JP7766722B2 - Skew generating device and skew generating method - Google Patents

Description

The present invention relates to a skew generation device and method for generating skew in the source signal when generating a ternary or higher level PAM signal.

Increasing the modulation rate is one way to improve communication speeds, but there are limits to how much can be achieved by using modulation rate alone, due to factors such as the operating speed of semiconductors and loss along the transmission path. For this reason, in recent high-speed serial communications, in addition to increasing modulation rates, a multi-level modulation technique called "PAM" is used, which transmits multiple bits per symbol by expressing the amplitude direction using multiple gradations. For example, PCIe Gen6 uses 32Gbaud PAM4, which transmits two bits of information per symbol by expressing the amplitude direction using four values, achieving a transmission capacity of 64Gbps with the same frequency bandwidth as 32Gbps. However, PAM has the disadvantage of significantly degrading the S/N ratio because it divides the amplitude direction into multiple parts, which places stricter requirements on distortion, reflection, and noise.

There are several ways to generate a PAM signal, but a typical example is combining multiple NRZ signals. Figure 9 shows the simplest example, a PAM4 signal configuration, where the two original NRZ signals are called the MSB and LSB. In the example shown in Figure 9, the LSB is attenuated by the desired amount using attenuator 21, and then combined with the MSB using combiner (power divider) 22 to generate a combined signal (PAM4 signal). This method requires that the arrival timing of the MSB and LSB be synchronized, but because the original signal sources and transmission paths are different, there is a possibility of timing discrepancies (skew). Because skew between the MSB and LSB significantly distorts the combined PAM4 waveform, a measurement system must have a mechanism to adjust for this. There may also be demand for intentionally introducing skew to evaluate the impact of MSB/LSB skew or for margin testing. Patent Document 1 below discloses technology related to skew adjustment.

By the way, one method for varying the skew between MSB and LSB is to use a mechanical delay adapter, a device that mechanically varies the line length of a coaxial line.

Japanese Patent Application Publication No. 10-096760

However, because mechanical delay adapters are operated mechanically, there are limitations to their repeatability, resolution, and variable range, making them unsuitable for automation. While there are types with wider variable ranges, in these cases there is a trade-off with resolution, making it difficult to achieve both variable range and resolution. Furthermore, because simply inserting a mechanical delay adapter affects the transmission characteristics, the person performing the measurement must carefully examine the measurement results to determine whether the effect is due to the mechanical delay adapter or skew. While the effects of the frequency characteristics and insertion loss of a mechanical delay adapter can be largely eliminated by calibrating the end face of the mechanical delay adapter, there is the problem that the calibration end face changes depending on the operation of the mechanical delay adapter, making it impossible to precisely maintain phase calibration.

The present invention was made in consideration of the above problems, and aims to provide a skew generation device and skew generation method that can vary the amount of skew in a PAM signal without mechanical operation.

In order to achieve the above object, a skew generating device according to a first aspect of the present invention comprises: a clock oscillator 2 for oscillating and outputting a clock signal;
a plurality of signal generators 4A, 4B including IQ modulators 13A, 13B, pattern generating units 14A, 14B, and control units 15A, 15B for outputting positive signals and negative signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle,
the plurality of signal generators operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation , while shifting the transmission timing of the signal by an integer unit of UI of the set skew amount ;
a control unit of the plurality of signal generators, when a skew amount in units of UI is set, allocating a necessary IQ modulation amount and a necessary transmission timing shift amount to control at least one of the IQ modulator and the pattern generation unit ;
The positive signals and negative signals are multiplexed at the same desired amplitude ratio to output a PAM signal with three or more values.

A skew generating device according to a second aspect of the present invention comprises a clock oscillator 2 for oscillating and outputting a clock signal;
a first signal generator 4A including a first IQ modulator 13A, a first pattern generating unit 14A, and a first control unit 15A for outputting upper positive and negative signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
a second signal generator 4B including a second IQ modulator 13B, a second pattern generating unit 14B, and a second control unit 15B for outputting a lower positive signal and a lower negative signal having opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
the first signal generator and the second signal generator operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation, and allocate a transmission timing shift that shifts the transmission timing of the signal by an integer unit of UI of the set skew amount , respectively ;
the first control unit, when a skew amount in units of UI is set, controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount ;
the second control unit, when a skew amount in units of UI is set, controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount;
The upper positive signal and the lower positive signal, and the upper negative signal and the lower negative signal are multiplexed at the same desired amplitude ratio to output a PAM3 signal.

A skew generating device according to a third aspect of the present invention comprises a clock oscillator 2 for oscillating and outputting a clock signal;
a first signal generator 4A including a first IQ modulator 13A, a first pattern generating unit 14A, and a first control unit 15A for outputting positive and negative MSB signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle ;
a second signal generator 4B including a second IQ modulator 13B, a second pattern generating unit 14B, and a second control unit 15B for outputting an LSB positive signal and a negative signal of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
the first signal generator and the second signal generator operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation, and allocate a transmission timing shift that shifts the transmission timing of the signal by an integer unit of UI of the set skew amount , respectively ;
the first control unit, when a skew amount in units of UI is set, controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount ;
the second control unit, when a skew amount in units of UI is set, controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount;
The positive signal of the MSB and the positive signal of the LSB, and the negative signal of the MSB and the negative signal of the LSB are multiplexed at the same desired amplitude ratio to output a PAM4 signal.

A skew generating device according to claim 4 of the present invention is a skew generating device according to any one of claims 1 to 3,
When the amount of skew is set in units of time, the amount of skew set in units of time is multiplied by the bit rate and converted into the amount of skew in units of UI.

A skew generating method according to claim 5 of the present invention comprises the steps of: oscillating and outputting a clock signal;
a step of outputting a positive signal and a negative signal of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by using a plurality of signal generators 4 including IQ modulators 13A and 13B, pattern generating units 14A and 14B, and control units 15A and 15B;
a step of synchronizing the operation of the plurality of signal generators, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount ;
When the skew amount in UI units is set, a control unit of the plurality of signal generators controls at least one of the IQ modulator and the pattern generation unit by dividing the necessary IQ modulation amount and transmission timing shift amount ;
and a step of multiplexing the positive signals and the negative signals at the same desired amplitude ratio to output a ternary or higher value PAM signal.

A skew generating method according to claim 6 of the present invention comprises the steps of: oscillating and outputting a clock signal;
a step of outputting upper positive and negative signals of opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a first signal generator 4A including a first IQ modulator 13A, a first pattern generating unit 14A, and a first control unit 15A;
a step of outputting a lower positive signal and a lower negative signal having opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a second signal generator 4B including a second IQ modulator 13B, a second pattern generating unit 14B, and a second control unit 15B ;
a step of synchronously operating the first signal generator and the second signal generator, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount ;
When the skew amount in units of UI is set, the first control unit controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount ;
When the skew amount in units of UI is set, the second control unit controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount;
and a step of multiplexing the upper positive signal and the lower positive signal together, and the upper negative signal and the lower negative signal together at the same desired amplitude ratio, to output a PAM3 signal.

A skew generating method according to a seventh aspect of the present invention comprises the steps of: oscillating and outputting a clock signal;
a step of outputting , by a first signal generator 4A including a first IQ modulator 13A, a first pattern generating unit 14A, and a first control unit 15A, a positive signal and a negative signal of an MSB having opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
a step of outputting , by a second signal generator 4B including a second IQ modulator 13B, a second pattern generating unit 14B, and a second control unit 15B, a positive signal and a negative signal of LSB having opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
a step of synchronously operating the first signal generator and the second signal generator, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount ;
When the skew amount in units of UI is set, the first control unit controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount ;
When the skew amount in units of UI is set, the second control unit controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount;
and a step of multiplexing the MSB positive signal and the LSB positive signal together, and the MSB negative signal and the LSB negative signal together at the same desired amplitude ratio, to output a PAM4 signal.

A skew generation method according to claim 8 of the present invention is a skew generation method according to any one of claims 5 to 7, further comprising:
When the amount of skew is set in units of time, the amount of skew set in units of time is multiplied by the bit rate and converted into the amount of skew in units of UI.

According to the present invention, the amount of skew of a ternary or higher level PAM signal can be varied using multiple synchronized signal generators, which not only improves convenience compared to using a mechanical delay adapter, but also enables measurements with excellent variable range, reproducibility, and resolution.

1 is a block diagram showing a schematic configuration of a skew generator according to the present invention when generating a PAM4 signal; 2 is a block diagram showing the internal configuration of a first signal generator and a second signal generator of the skew generating device of FIG. 1; FIG. 1 is a block diagram showing a schematic configuration of a skew generator according to the present invention when generating a PAM3 signal; 1 is a block diagram showing a schematic configuration of a skew generator according to the present invention when generating a PAM8 signal; FIG. 10 is an explanatory diagram of a method for multiplexing PAM2 ^N signals. FIG. 10 is an explanatory diagram of a method for multiplexing a PAMN+1 signal. FIG. 7 is an explanatory diagram of bit correspondence in USB4 Version 2.0 as an example using PAM3 generated by the multiplexing method of FIG. 6. 10 is an explanatory diagram illustrating a case where a multiplexing method for a PAM2 ^N signal and a multiplexing method for a PAMN+1 signal are combined. FIG. 1 is an explanatory diagram of a conventional method for generating a PAM4 signal.

The following describes in detail the embodiments of the present invention, with reference to the accompanying drawings.

The skew generation device and method of the present invention generate PAM skew (the individual skews of the signals that are the basis for generating the PAM signal) for ternary or higher-valued PAM signals using positive and negative signals, which are repetitive signals of opposite phases. The skew generation device 1 (1A) shown in Figure 1 enables the amount of skew of a PAM4 signal, which is made up of positive and negative signals, which are repetitive signals of opposite phases, input to an object W (device under test or measuring instrument), to be varied. It is generally comprised of a clock oscillator 2, a setting unit 3, multiple signal generators 4 (first signal generator 4A, second signal generator 4B), and a PAM encoder 5.

The skew generating device 1A synchronizes the operation of the first signal generator 4A and the second signal generator 4B, manipulates the internal delay amounts of the first signal generator 4A and the second signal generator 4B, varies the PAM4 signal to the desired skew amount (eye phase), and outputs positive and negative signals with arbitrary delay amounts 1 and 2.

Note that in Figures 1 to 4, positive signals are represented as Pos and negative signals as Neg. Also, in Figures 1 to 3, the first signal generator 4A and the second signal generator 4B are shown as separate block configurations, and in Figure 4, the first signal generator 4A, the second signal generator 4B, and the third signal generator 4C are shown as separate block configurations, but these can also be configured as a single module.

The clock oscillator 2 oscillates and outputs a clock signal of the required frequency using a rectangular wave signal or a sine wave signal. The clock signal oscillated and output from the clock oscillator 2 is input to an IQ modulator 13A (described below) of the first signal generator 4A and an IQ modulator 13B (described below) of the second signal generator 4B.

The setting unit 3 is a GUI that the user operates to input information necessary to generate PAM skew, and sets the type of pattern (positive signal and negative signal) to be input to the evaluation object W, the bit rate, and the amount of skew for each of the first signal generator 4A and the second signal generator 4B.

Here, the skew amount can be input in UI (unit interval) or time (sec). However, in this embodiment, as with the skew amount varying method described below, the skew amount is varied using IQ modulation and transmission timing shift, so it operates in the dimension of phase ≈ UI rather than time (sec). Note that transmission timing shift means shifting the transmission timing of the signal bits (symbols in PAM3 and higher) by an integer unit of UI of the set skew amount: N bits (symbols). Therefore, when the skew amount is input and set by the setting unit 3 in units of time (sec), the setting is converted to units of UI using the formula UI = skew amount time (sec) × bit rate in the control unit 15A (described later) of the first signal generator 4A and the control unit 15B (described later) of the second signal generator 4B.

In this embodiment, since the skew resolution is in 2mUI units, depending on the input value in units of time (sec) input and set by the setting unit 3, it may not be in 2mUI units and rounding may be necessary. In this case, the control unit 15A of the first signal generator 4A and the control unit 15B of the second signal generator 4B (described below) calculate the closest skew amount time (sec) that can be achieved in 2mUI units and perform a process of overwriting the input value by the setting unit 3.

The first signal generator 4A has a first output terminal 11A that outputs a positive signal Pos1 of the MSB (most significant bit) and a second output terminal 12A that outputs a negative signal Neg1 of the MSB, and operates synchronously with the second signal generator 4B. As shown in Figure 2, the first signal generator 4A is configured with an IQ modulator 13A, a pattern generation unit 14A, and a control unit 15A.

Under the control of the control unit 15A, the IQ modulator 13A performs IQ modulation on the clock signal from the clock oscillator 2 using the input I and Q signals based on the decimal unit of the skew amount set by the setting unit 3.

Under the control of the control unit 15A, the pattern generation unit 14A generates the MSB positive signal Pos1 and negative signal Neg1 of the desired pattern based on the pattern type and bit rate set by the setting unit 3, shifts the transmission timing of the generated MSB positive signal Pos1 and negative signal Neg1 based on the integer unit of the skew amount set by the setting unit 3, and outputs the MSB positive signal Pos1 of the transmission timing-shifted signals from the first output terminal 11A and the MSB negative signal Neg1 from the second output terminal 12A.

The control unit 15A outputs a timing synchronization signal to the control unit 15B (described later) of the second signal generator 4B so that the first signal generator 4A operates in synchronization with the second signal generator 4B, and controls the IQ modulator 13A and pattern generation unit 14A in an integrated manner.

Specifically, the control unit 15A outputs I and Q signals corresponding to the decimal unit of the skew amount set by the setting unit 3 to the IQ modulator 13A, and adjusts and controls the phase angle of the clock signal from the clock oscillator 2. The control unit 15A also generates a positive signal Pos1 and a negative signal Neg1 of the desired pattern based on the pattern type and bit rate set by the setting unit 3, and controls the pattern generation unit 14A to shift the transmission timing based on the integer unit of the skew amount set by the setting unit 3. Furthermore, when the skew amount is input and set by the setting unit 3 in units of time (sec), the control unit 15A converts and sets it in units of UI based on the formula UI = skew amount time (sec) × bit rate. If rounding is required, the control unit 15A calculates the closest skew amount time (sec) that can be achieved in 2mUI units, and overwrites and sets the value input by the setting unit 3.

The second signal generator 4B has the same configuration as the first signal generator 4A, and has a first output terminal 11B that outputs an LSB (least significant bit) positive signal Pos2 and a second output terminal 12B that outputs an LSB negative signal Neg2. It operates in synchronization with the first signal generator 4A, and as shown in Figure 2, is configured with an IQ modulator 13B, a pattern generation unit 14B, and a control unit 15B.

Under the control of the control unit 15B, the IQ modulator 13B performs IQ modulation on the clock signal from the clock oscillator 2 using the input I and Q signals based on the decimal unit of the skew amount set by the setting unit 3.

Under the control of the control unit 15B, the pattern generation unit 14B generates the LSB positive signal Pos2 and negative signal Neg2 of the desired pattern based on the pattern type and bit rate set by the setting unit 3, shifts the transmission timing of the generated LSB positive signal Pos2 and negative signal Neg2 based on the integer unit of the skew amount set by the setting unit 3, and outputs the LSB positive signal Pos2 of the transmission timing-shifted signals from the first output terminal 11B and the LSB negative signal Neg2 from the second output terminal 12B.

The control unit 15B outputs a timing synchronization signal to the control unit 15A of the first signal generator 4A so that the second signal generator 4B operates in synchronization with the first signal generator 4A, and controls the IQ modulator 13B and pattern generation unit 14B in an integrated manner.

Specifically, the control unit 15B outputs I and Q signals corresponding to the decimal unit of the skew amount set by the setting unit 3 to the IQ modulator 13B, and adjusts and controls the phase angle of the clock signal from the clock oscillator 2. The control unit 15B also generates a pattern (positive signal Pos2 and negative signal Neg2) based on the pattern type and bit rate set by the setting unit 3, and controls the pattern generation unit 14B to shift the transmission timing based on the integer unit of the skew amount set by the setting unit 3. Furthermore, when the skew amount is input and set by the setting unit 3 in units of time (sec), the control unit 15B converts and sets it in units of UI based on the formula UI = skew amount time (sec) × bit rate. If rounding is required, the control unit 15B calculates the closest skew amount time (sec) that can be achieved in 2mUI units, and overwrites and sets the value input by the setting unit 3.

The PAM encoder 5 combines the positive signals and negative signals output by the first signal generator 4A and the second signal generator 4B at a desired amplitude ratio and outputs an encoded combined signal (PAM4 signal). It includes attenuators 5a (5a1, 5a2) and combiners (power dividers) 5b (5b1, 5b2).

Attenuator 5a1 attenuates the LSB positive signal Pos2 output from the first output terminal 11B of second signal generator 4B by the desired attenuation amount. Attenuator 5a2 attenuates the LSB negative signal Neg2 output from the second output terminal 12B of second signal generator 4B by the same desired attenuation amount as the LSB positive signal Pos2. Note that if the control unit 15B of second signal generator 4B varies the amplitudes of the LSB positive signal Pos2 and the LSB negative signal Neg2 at the desired amplitude ratio set by setting unit 3, attenuators 5a (5a1, 5a2) can be omitted.

The combiner 5b1 combines the MSB positive signal Pos1 output from the first output terminal 11A of the first signal generator 4A with the LSB positive signal Pos2 attenuated by the attenuator 5a1, and outputs the result to the object W (object under test or measuring instrument) as a combined signal (PAM4 signal) of positive signals with the desired amplitude ratio. The combiner 5b2 combines the MSB negative signal Neg1 output from the second output terminal 12A of the first signal generator 4A with the LSB negative signal Neg2 attenuated by the attenuator 5a2, and outputs the result to the object W (object under test or measuring instrument) as a combined signal (PAM4 signal) of negative signals with the same desired amplitude ratio as the positive signal Pos1.

Next, we will explain how to vary the amount of skew using the skew generation device 1A configured as described above.

First, the setting unit 3 is used to set the type of pattern (positive signal, negative signal) to be input to the object W (object under test or measuring instrument), the bit rate, and the amount of skew for each of the first signal generator 4A and second signal generator 4B.

Here, the skew amount can be input in UI or time (sec). However, if the skew amount is input and set in units of time (sec), the control unit 15A of the first signal generator 4A and the control unit 15B of the second signal generator 4B convert it into UI units and set it based on the formula UI = skew amount time (sec) x bit rate.

In addition, if the input value in units of time (sec) input and set by the setting unit 3 does not match 2mUI units and requires rounding, the control unit 15A of the first signal generator 4A and the control unit 15B of the second signal generator 4B calculate the closest skew amount of time (sec) that can be achieved in 2mUI units, and overwrite the input value by the setting unit 3.

Then, once the skew amount in UI units is set, the control unit 15A of the first signal generator 4A and the control unit 15B of the second signal generator 4B allocate the required IQ modulation amount and transmission timing shift amount and control at least one of the IQ modulators 13A, 13B and the pattern generation units 14A, 14B.

Here, transmission timing shift can only manipulate the skew amount in 1 UI units, but the maximum change range is large (e.g., ±64 UI). In contrast, IQ modulation can vary the skew amount in decimal units (e.g., 2 mUI), but the maximum change range is small (±360° = ±1000 mUI). For this reason, in this embodiment, the integer unit amount of the required skew amount (UI) is allocated to transmission timing shift, and the decimal unit amount is allocated to IQ modulation, and both are controlled.

Specifically, if the skew amount is 1250 (mUI), it is 1 transmission timing shift (1000 mUI) + IQ modulation 90° (250 mUI). Also, if the skew amount is -2250 (mUI), it is -3 transmission timing shift (-3000 mUI) + IQ modulation 270° (750 mUI).

The above examples use IQ modulation at 0 to 360° (0 to 2π) = 0 to 1000 mUI, but the point at which the transmission timing shift is advanced is arbitrary. For example, IQ modulation can be used at ±500 mUI, with ±180° (±π) = 0 mUI as the center. In this case, if the skew amount is 1250 (mUI), the result is 1 transmission timing shift (1000 mUI) + IQ modulation 90° (250 mUI). Also, if the skew amount is -2250 (mUI), the result is -2 transmission timing shift (-2000 mUI) + IQ modulation -90° (-250 mUI).

Note that while the above examples show cases where the skew amount is varied using both transmission timing shift and IQ modulation, it is also possible to vary the skew amount using either transmission timing shift or IQ modulation, depending on the amount of skew that is set. For example, if the amount of skew that is set is 1000 (mUI), the result is 1 transmission timing shift (1000 mUI), and only the transmission timing shift is controlled. Furthermore, if the amount of skew that is set is 250 (mUI), the result is 90° IQ modulation (250 mUI), and only the IQ modulation is controlled.

In the above-described skew generating device 1A, the first signal generator 4A and second signal generator 4B operate synchronously, shifting the transmission timing by integer units of the UI of the set skew amount and allocating the decimal units to IQ modulation to control at least one of them, combining positive signals (Pos1 and Pos2) and negative signals (Neg1 and Neg2) at the same desired amplitude ratio, and the combined signal (PAM4 signal) is input to the object W (device under test or measuring instrument).

That is, when the positive signal Pos1 and negative signal Neg1 are varied to the desired skew amount (arbitrary delay amount 1) in the first signal generator 4A, and the positive signal Pos2 and negative signal Neg2 are varied to the desired skew amount (arbitrary delay amount 2) in the second signal generator 4B, the LSB positive signal Pos2 output from the first output terminal 11B of the second signal generator 4B is attenuated by the desired attenuation amount (attenuation amount corresponding to the desired amplitude ratio) in the attenuator 5a1 of the PAM encoder 5, and then combined in the combiner 5b1 with the MSB positive signal Pos1 output from the first output terminal 11A of the first signal generator 4A, and input to the object W (device under test or measuring instrument) as a combined signal (PAM4 signal) of positive signals with the desired amplitude ratio.

The LSB negative signal Neg2 output from the second output terminal 12B of the second signal generator 4B is attenuated by the same desired attenuation amount (attenuation amount corresponding to the desired amplitude ratio) as the LSB positive signal Pos2 by the attenuator 5a2 of the PAM encoder 5, and then combined with the MSB negative signal Neg1 output from the second output terminal 12A of the first signal generator 4A by the combiner 5b2, and input to the object W (object under test or measuring instrument) as a combined signal (PAM4 signal) of negative signals with the desired amplitude ratio.

Note that a differential signal is generated from the combined signal (PAM4 signal) of the positive signal input to the target W and the combined signal (PAM4 signal) of the negative signal input to the target W described above. However, if only one signal (single-ended transmission) is required to be input to the target W, the remaining signal can be input to a monitor device (not shown) for monitoring purposes to observe the waveform.

The pattern generation unit 14A of the first signal generator 4A and the pattern generation unit 14B of the second signal generator 4B described above are capable of generating PRBS patterns and arbitrary patterns, and can control the start timing of the patterns. Specifically, to achieve higher-rate data output from a low-rate pattern generation unit, for example, they can be configured with an FPGA that outputs 1/N data and multiple MUXes (N:1 MUX for MSB output, N:1 MUX for LSB output, 2:1 MUX for PAM4 output), or they can be configured with D-FFs, but are not limited to these circuit configurations.

Furthermore, in the embodiment shown in Figures 1 and 2, a PAM4 signal is generated as the PAM signal, but this is not limited to this. For example, it is also possible to generate a PAM3 signal by combining an Upper signal and a Lower signal.

Below, an embodiment of the skew generator 1 (1B) for generating a PAM3 signal will be described with reference to Figure 3. Note that components that function in the same way as those in the skew generator 1A of Figure 1 are given the same numbers and their description will be omitted.

The skew generating device 1 (1B) in Figure 3 is generally configured with a clock oscillator 2, a setting unit 3, a first signal generator 4A, a second signal generator 4B, and a PAM encoder 5.

In the skew generation device 1B of Figure 3, the first signal generator 4A and second signal generator 4B operate synchronously, shifting the transmission timing by integer units of UI of the set skew amount, and allocating and controlling the decimal units as IQ modulation. Positive signals and negative signals are combined at the same desired amplitude ratio, and the combined signal (PAM3 signal) is input to the object W (device under test or measuring instrument).

That is, an Upper signal based on positive signal Pos1, which has been adjusted to the desired skew amount (arbitrary delay amount 1), is output from first output terminal 11A of first signal generator 4A, and a Lower signal based on positive signal Pos2, which has been adjusted to the desired skew amount (arbitrary delay amount 2), is output from first output terminal 11B of second signal generator 4B. The Upper signal based on positive signal Pos1 and the Lower signal based on positive signal Pos2 are then combined by combiner 5b (5b1) of PAM encoder 5, and input to object W (device under test or measuring instrument) as a combined signal (PAM3 signal) based on positive signals with the desired amplitude ratio.

In addition, an Upper signal based on the negative signal Neg1, which has been adjusted to the desired skew amount (arbitrary delay amount 1), is output from the second output terminal 12A of the first signal generator 4A, and a Lower signal based on the negative signal Neg2, which has been adjusted to the desired skew amount (arbitrary delay amount 2), is output from the second output terminal 12B of the second signal generator 4B. The Upper signal based on the negative signal Neg1 and the Lower signal based on the negative signal neg2 are then combined by the combiner 5b (5b2) of the PAM encoder 5, and input to the object W (device under test or measuring instrument) as a combined signal (PAM3 signal) based on negative signals with the desired amplitude ratio.

In addition, one of the combined signals (PAM3 signal) based on a positive signal and the combined signal (PAM3 signal) based on a negative signal input to the target W described above can also be input to a monitor device (not shown) for monitoring purposes to observe the waveform.

Furthermore, in the embodiment of Figures 1 and 2, two signal generators (first signal generator 4A and second signal generator 4B) are operated synchronously, but the number of signal generators operated synchronously is not limited to two. For example, it is also possible to operate three signal generators synchronously to generate a PAM8 signal. Below, an embodiment of the skew generation device 1 (1C) in which three signal generators are operated synchronously to generate a PAM8 signal will be described with reference to Figure 4. Note that components that function in the same way as the skew generation device 1A in Figure 1 are assigned the same numbers and their description will be omitted.

The skew generating device 1 (1C) in Figure 4 is generally configured with a clock oscillator 2, a setting unit 3, a first signal generator 4A, a second signal generator 4B, a third signal generator 4C, and a PAM encoder 5. Note that the third signal generator 4C has the same internal configuration as the first signal generator 4A and the second signal generator 4B shown in Figure 2.

In the skew generating device 1C of Figure 4, the first signal generator 4A, second signal generator 4B, and third signal generator 4C operate synchronously, controlling the set skew amount by shifting the transmission timing by integer units of UI and allocating the decimal units as IQ modulation, combining positive signals and negative signals at the same desired amplitude ratio, and the combined signal (PAM8 signal) is input to the object W (device under test or measuring instrument).

That is, a positive signal Pos1 adjusted to the desired skew amount (arbitrary delay amount 1) is output from the first output terminal 11A of the first signal generator 4A, a positive signal Pos2 adjusted to the desired skew amount (arbitrary delay amount 2) is output from the first output terminal 11B of the second signal generator 4B, and then attenuated by the desired attenuation amount (attenuation amount corresponding to the desired amplitude ratio) by the attenuator 5a (5a1) of the PAM encoder 5, and a positive signal Pos3 adjusted to the desired skew amount (arbitrary delay amount 3) is output from the first output terminal 11C of the third signal generator 4C. The positive signal Pos1 and the positive signal Pos2 attenuated by the attenuator 5a (5a1) are then combined by the combiner 5b (5b1), and then combined with the positive signal Pos3 by the combiner 5b (5b2). The combined signal (PAM8 signal) of positive signals with the desired amplitude ratio is input to the object (device under test or measuring instrument) (not shown).

In addition, a negative signal Neg1 that has been changed to the desired skew amount (arbitrary delay amount 1) is output from the second output terminal 12A of the first signal generator 4A, a negative signal Neg2 that has been changed to the desired skew amount (arbitrary delay amount 2) is output from the second output terminal 12B of the second signal generator 4B, and then attenuated by the desired attenuation amount (attenuation amount corresponding to the desired amplitude ratio) by the attenuator 5a (5a2) of the PAM encoder 5, and a negative signal Neg3 that has been changed to the desired skew amount (arbitrary delay amount 3) is output from the first output terminal 11C of the third signal generator 4C. Then, the negative signal Neg1 and the negative signal Neg2 attenuated by the attenuator 5a (5a2) of the PAM encoder 5 are combined by the combiner 5b (5b3) of the PAM encoder 5, and then the negative signal Neg3 is combined by the combiner 5b (5b3) of the PAM encoder 5, and the combined signal (PAM8 signal) of negative signals with the desired amplitude ratio is input to the object (object under test or measuring instrument) not shown.

In addition, one of the combined signals (PAM8 signal) based on positive signals and the combined signal (PAM8 signal) based on negative signals input to an object (object under test or measuring instrument) (not shown) can be input to a monitor device (not shown) for monitoring purposes to observe the waveform. Furthermore, if the control unit 15B of the second signal generator 4B varies the amplitudes of the positive signal Pos2 and the negative signal Neg2 at the desired amplitude ratio set by the setting unit 3, the attenuator 5a (5a1, 5a2) of the PAM encoder 5 can be omitted.

In the above-described embodiment, PAM3, PAM4, and PAM8 signals were used as examples of PAM signals controlled by transmission timing shifts of integer units of UI of the set skew amount and IQ modulation of decimal units. However, this is not limited to these signals and can be applied to any PAM signal. Below, a method for multiplexing any PAM signal will be explained with reference to Figures 5 to 8. Note that Figures 5, 6, and 8 illustrate the case where a PAM signal is generated by multiplexing positive signals, but a PAM signal can also be generated by multiplexing negative signals in the same way.

FIG. 5 is an explanatory diagram of a method for multiplexing a PAM2 ^N signal, FIG. 6 is an explanatory diagram of a method for multiplexing a PAMN+1 signal, FIG. 7 is an explanatory diagram of bit correspondence in USB4 Version 2.0 as an example using PAM3 generated by the multiplexing method of FIG. 6, and FIG. 8 is an explanatory diagram of a case where the multiplexing method for a PAM2 ^N signal and the multiplexing method for a PAMN+1 signal are combined. Note that FIGS. 5, 6, and 8 show a case where the skew amount is set to 0. The amplitude ratio is adjusted by an attenuator (not shown) or the control unit of the signal generator 4. Here, the 2 ^N in PAM2 ^N indicates a power of 2.

If the total number of NRZ signals used (the number of signal generators 4) is N (N≧2) and the nth signal generator 4 among the N signal generators 4 is n, then in the PAM2N signal multiplexing method, as shown in Fig. 5, the ^PAM2N signal can be generated by multiplexing ^N NRZ signals generated by the first to Nth signal generators 4 using a combiner 5b. In this case, the first to Nth signal generators 4 correspond to each digit of the bits, and the amplitude ratio corresponds to the weight (power of 2) of that digit.

Let N (N≧2) be the total number of NRZ signals used (number of signal generators 4), and n be the nth signal generator 4 among the N signal generators 4. In the PAMN+1 signal multiplexing method, as shown in Figure 6, N NRZ signals generated by the first through Nth signal generators 4 are multiplexed at the same amplitude by a combiner 5b to generate the PAMN+1 signal. This PAMN+1 multiplexing method makes it possible to generate any PAM signal that is not a power of two, such as a PAM3 signal. An example of generating a PAM3 signal will be explained with reference to Figure 7. As an example of using a PAM3 signal, USB4 Version 2.0 transmits three bits in two symbols, as shown in Figure 7. Specifically, two signal generators 4 are used, and for example, in the case of a bit string of "011" in Figure 7, the first signal generator 4 generates a 1 and the second signal generator 4 generates a 0 at the first symbol, and the first signal generator 4 generates a 0 and the second signal generator 4 generates a 0 at the second symbol.

In a multiplexing method that combines the ^PAM2N signal multiplexing method and the PAMN+1 signal multiplexing method, as shown in Figure 8, the number of signals from signal generators 4 that are added together at a power amplitude ratio is N (N ≥ 2), and the number of signals from signal generators 4 that are added together at the same amplitude ratio is M (M ≥ 1), and a ^PAM2N + M signal can be generated by multiplexing the NRZ signals generated by each signal generator 4 using a combiner 5b. Figure 8 shows an example of generating a PAM22 + 1 = PAM5 signal when the number of signals from signal generators 4 that are added together at a power amplitude ratio (1/2) is N = 2 and the number of signals from signal generators 4 that are added together at the same amplitude ratio ( ¹ ) is M = 1.

As such, according to this embodiment, multiple synchronized signal generators (first signal generator 4A and second signal generator 4B in Figures 1 and 3, and first signal generator 4A, second signal generator 4B, and third signal generator 4C in Figure 4) individually generate positive and negative signals, making it possible to vary the eye phase to the desired skew amount. This not only improves convenience compared to using conventional mechanical delay adapters, but also enables skew variation with excellent variable width, reproducibility, and resolution. Specifically, a variable width of ±64 UI and a resolution of 2 mUI are achieved, with an operating rate of 2.4 Gbaud to 64.2 Gbaud. Converting this to time units translates to a maximum variable width of ±26.6 ns and a minimum resolution of 31.1 fs.

The skew generator 1 of this embodiment is not configured to generate positive and negative signals from a single signal generator, but rather, as shown in Figure 1, is configured to generate positive and negative signals individually from two synchronously operating signal generators (first signal generator 4A and second signal generator 4B). This allows each signal to be independently controlled for parameters other than skew. The controllable parameters depend on the functionality of the signal generator, but examples include amplitude and Tx equalizer (emphasis). For comparison with Figure 9, Figure 1 uses attenuator 5a (5a1, 5a2: 6 dB attenuator) on the second signal generator 4B side, which outputs the LSB positive and negative signals. However, the amplitude may be halved within the second signal generator 4B without using an attenuator.

The amount of skew can be controlled by inputting it in time units or UI units in the setting unit 3, or by intuitively operating the setting unit 3 while the skewed waveform image is displayed.

As such, according to this embodiment, the skew amount (eye phase) of ternary or higher PAM signals can be varied using multiple synchronized signal generators (at least two signal generators), which not only improves convenience compared to using a mechanical delay adapter, but also enables measurements with excellent variable range, reproducibility, and resolution.

Furthermore, since it does not affect the transmission path characteristics, the evaluator can easily separate and evaluate only the effects of skew.

In addition, because multiple signal generators (4A, 4B, 4C) can be operated independently, it is possible to intentionally disrupt the symmetry of the waveform, making it possible to evaluate skew not only from the perspective of arrival timing, but also from the perspective of waveform asymmetry.

Furthermore, the amount of skew can be controlled by inputting it in time units or UI units in the setting unit 3, or by intuitively operating the setting unit 3 while an image of a skewed waveform is displayed, making it easier for the user to intuitively grasp what kind of skewed signal they are providing.

These are useful for compensating for skew between, for example, MSB and LSB that occurs due to the measurement system, and can also be used for verification that anticipates skew between, for example, MSB and LSB that may occur in devices due to manufacturing variations, and for evaluation when a device receives a skewed PAM signal.

The above describes the best mode for the skew generation device and skew generation method according to the present invention, but the present invention is not limited to the description and drawings of this mode. In other words, all other modes, embodiments, and operational techniques that are developed by those skilled in the art based on this mode are naturally included within the scope of the present invention.

REFERENCE SIGNS LIST 1 (1A, 1B, 1C) Skew generation device 2 Clock oscillator 3 Setting unit 4 Signal generator 4A First signal generator 4B Second signal generator 4C Third signal generator 5 PAM encoder 5a (5a1, 5a2) Attenuator 5b (5b1, 5b2, 5b3, 5b4) Combiner 11A, 11B, 11C First output terminal 12A, 12B, 12C Second output terminal 13A, 13B IQ modulator 14A, 14B Pattern generation unit 15A, 15B Control unit 21 Attenuator 22 Combiner W Object (device under test or measuring instrument)

Claims (8)

a clock oscillator (2) that oscillates and outputs a clock signal;
a plurality of signal generators (4A, 4B) including IQ modulators (13A, 13B), pattern generating units (14A, 14B), and control units (15A, 15B ) for outputting positive signals and negative signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle,
the plurality of signal generators operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation , while shifting the transmission timing of the signal by an integer unit of UI of the set skew amount ;
a control unit of the plurality of signal generators, when a skew amount in units of UI is set, allocating a necessary IQ modulation amount and a necessary transmission timing shift amount to control at least one of the IQ modulator and the pattern generation unit ;
A skew generator that combines positive signals and negative signals at the same desired amplitude ratio to output a PAM signal with three or more levels. a clock oscillator (2) that oscillates and outputs a clock signal;
a first signal generator (4A) including a first IQ modulator (13A), a first pattern generating unit (14A), and a first control unit (15A) for outputting upper positive and negative signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
a second signal generator (4B) including a second IQ modulator (13B), a second pattern generating unit (14B), and a second control unit (15B) for outputting a lower positive signal and a lower negative signal having opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
the first signal generator and the second signal generator operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation, and allocate a transmission timing shift that shifts the transmission timing of the signal by an integer unit of UI of the set skew amount , respectively ;
the first control unit, when a skew amount in units of UI is set, controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount ;
the second control unit, when a skew amount in units of UI is set, controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount;
A skew generating device characterized in that the upper positive signal and the lower positive signal, and the upper negative signal and the lower negative signal are multiplexed at the same desired amplitude ratio to output a PAM3 signal. a clock oscillator (2) that oscillates and outputs a clock signal;
a first signal generator (4A) including a first IQ modulator (13A), a first pattern generating unit (14A), and a first control unit (15A) for outputting positive and negative MSB signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
a second signal generator (4B) including a second IQ modulator (13B), a second pattern generating unit (14B), and a second control unit (15B) for outputting an LSB positive signal and a negative signal of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
the first signal generator and the second signal generator operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation, and allocate a transmission timing shift that shifts the transmission timing of the signal by an integer unit of UI of the set skew amount , respectively ;
the first control unit, when a skew amount in units of UI is set, controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount ;
the second control unit, when a skew amount in units of UI is set, controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount;
A skew generating device characterized in that the MSB positive signal and the LSB positive signal, and the MSB negative signal and the LSB negative signal are multiplexed at the same desired amplitude ratio to output a PAM4 signal. A skew generating device as described in any one of claims 1 to 3, characterized in that when the skew amount is set in units of time, the skew amount set in units of time is multiplied by the bit rate to convert it into a skew amount in units of UI. oscillating and outputting a clock signal;
a step of outputting a positive signal and a negative signal of opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a plurality of signal generators (4) including IQ modulators (13A, 13B), pattern generating units (14A, 14B), and control units (15A, 15B) ;
a step of synchronizing the operation of the plurality of signal generators, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount ;
When the skew amount in UI units is set, a control unit of the plurality of signal generators controls at least one of the IQ modulator and the pattern generation unit by dividing the necessary IQ modulation amount and transmission timing shift amount ;
and a step of multiplexing positive signals and negative signals at the same desired amplitude ratio to output a ternary or higher PAM signal. oscillating and outputting a clock signal;
a step of outputting upper positive and negative signals of opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a first signal generator (4A) including a first IQ modulator (13A), a first pattern generating unit (14A), and a first control unit (15A) ;
a step of outputting a lower positive signal and a lower negative signal having opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a second signal generator (4B) including a second IQ modulator (13B), a second pattern generating unit (14B), and a second control unit (15B) ;
a step of synchronously operating the first signal generator and the second signal generator, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount ;
When the skew amount in units of UI is set, the first control unit controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount ;
When the skew amount in units of UI is set, the second control unit controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount;
a step of combining the upper positive signal and the lower positive signal, and the upper negative signal and the lower negative signal at the same desired amplitude ratio to output a PAM3 signal. oscillating and outputting a clock signal;
a step of outputting a positive signal and a negative signal of an MSB having opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a first signal generator (4A) including a first IQ modulator (13A), a first pattern generating unit (14A), and a first control unit (15A) ;
a step of outputting , by a second signal generator (4B) including a second IQ modulator (13B), a second pattern generating unit (14B), and a second control unit (15B), a positive signal and a negative signal of LSB having opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle;
a step of synchronously operating the first signal generator and the second signal generator, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount ;
When the skew amount in units of UI is set, the first control unit controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount ;
When the skew amount in units of UI is set, the second control unit controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount;
and a step of multiplexing the MSB positive signal and the LSB positive signal together, and the MSB negative signal and the LSB negative signal together at the same desired amplitude ratio to output a PAM4 signal. A skew generation method according to any one of claims 5 to 7, characterized in that when the skew amount is set in units of time, the skew amount set in units of time is multiplied by the bit rate to convert it into a skew amount in units of UI.