JP6549671B2 - Signal generator and signal generation method thereof - Google Patents

Description

  The present invention mixes a signal in the intermediate frequency band with a local signal and extracts a target signal from the output with a filter. In a signal generator having a frequency conversion circuit of the upconversion type, the variable width of the target signal is greater than the intermediate frequency. To suppress unnecessary signal components without using a large number of filters and switches for filter switching so that the level of the target signal can be identified with high accuracy from the level of the output signal of the filter. Related to technology.

  The frequency band of radio waves used for communication by wireless communication devices such as mobile phones is increasing year by year, and the frequency of the test signal required by the test apparatus for testing wireless communication devices is also increasing accordingly. On the other hand, since it is difficult to generate a test signal for the radio frequency band so that it can be varied directly and over a wide range of the frequency band assigned to communication, it is usually necessary for the test. A signal containing information is generated as a signal of a predetermined intermediate frequency lower than the radio frequency band, and this is supplied to the heterodyne frequency conversion circuit to convert it into a signal of the desired frequency in the radio frequency band.

As shown in FIG. 9, the heterodyne frequency conversion circuit nonlinearly _generates a signal of intermediate frequency f _IF (hereinafter referred to as an intermediate frequency signal) S _IF and a local signal S _LOC of which frequency f _LOC is variable. The signal component of the frequency of the difference between the input signals (| f _LOC −f _IF |) or the sum frequency (f _LOC + f _IF ) from the signal contained in the output of the mixer 1 which is an element One of them is extracted as the target signal S _{RF by the} filter 2 (usually a band pass filter), and if the variable width of the frequency f _LOC of the local signal S _LOC is Fw, the frequency f _RF of the target signal S _RF is also The width of Fw can be varied, in which case the pass band of the filter 2 corresponds to the frequency range of the target signal S _RF .

In general, when two signals are input to a circuit having non-linearity, each of the two input signals (in addition to the input signal (which may be its leak component)) Harmonic component, component of sum and difference frequency of fundamental waves of two input signals, component of sum and difference frequency of one fundamental wave and other harmonics and sum and difference frequency of harmonics Contains ingredients. Here, the sum and difference frequency components including the fundamental wave and the harmonics of the two input signals are represented by n · f _IF ± m · f _LOC using integers n and m, and the fundamental waves If one of the sum and difference frequency components f _IF ± f _LOC of m = 1) is the target signal, the other is the image component.

  In addition, when at least one of n and m is 2 or more, the sum and difference frequency components are referred to as (n + m) order intermodulation products in the case of amplifiers etc. In the case, it is called m × n spurious or multiple response. In the following description, the above-mentioned frequency component is called a multiple response component, and the order is counted by the larger one of n and m. The level of this multiple response component basically decreases as the order increases, and it is generally considered that low-order components up to the second or third order are considered.

Also, as the mixer 1 for frequency conversion, a double balanced mixer (DBM) with less passing through to the input signal (high isolation) is generally used, and switching of the intermediate frequency signal S _IF by the local signal S _LOC In order to perform processing, the level of the intermediate frequency signal S _IF is set sufficiently smaller (eg, -20 dB) than the level of the local signal S _LOC so as not to affect this switching operation.

Therefore, among the signals included in the output of mixer 1, high-order harmonic components of intermediate frequency signal S _IF and high-order fifth or higher order multiple response components are sufficiently small relative to the level of target signal S _RF and ignored. can be, leak component and harmonic components of the level is high local signal S _LOC, image component of the target signal S _RF, for multiple response component of low-order (up to the second order or third order), a target signal S _RF There is a high possibility that the level can not be ignored with respect to the

Although there are infinite _choices of the intermediate frequency f _IF and the frequency of the local signal S _LOC to set the frequency variable range of the target signal S _RF to a desired range, in general, the frequency difference between the target signal S _RF and the image component The second, third, and third harmonics of the high-frequency local signal S _LOC , and the second, third harmonics of the intermediate-frequency signal S _IF are filtered to increase the intermediate frequency f _IF relatively to increase Select a combination of frequencies that does not enter the 2 pass band.

For example, as shown in FIG. 10, assuming that the intermediate frequency f _IF is 5 GHz, the variable range of the frequency f _RF of the target signal S _RF and the passband of the filter are 27 GHz ± 2 GHz, the frequency f of the local signal S _LOC is _LOC may be set in the range of 22 ± 2 GHz (in the case of sum frequency conversion). In this case, the image component is in the range of 17 ± 2 GHz, and the second or higher harmonics of the local signal S _LOC is 2 × (22 ± 2) GHz or more, both of which are sufficiently away from the passband of the filter. Furthermore, among the harmonics of the intermediate frequency signal _SIF, the harmonics of 2 to 4 and the harmonics of 6 or more do not enter the passband of the filter, and the 5th harmonic (25 GHz) is the passband of the filter 22 The level of the fifth harmonic of the level of the intermediate frequency signal S _IF is sufficiently smaller than the level of the target signal S _RF although it falls within ± 2 GHz.

Also, as described above, when the frequency variable width Fw (= 4 GHz) is smaller than the intermediate frequency f _IF (= 5 GHz), the leak component (22 ± 2 GHz) of the local signal S _LOC enters the passband 27 ± 2 GHz of the filter (2 × 5) ± (22 ± 2) GHz of the second-order multiple response component is 32 ± 2 GHz and 12 ± 2 GHz, and 2 × (22 ± 2) of another second-order multiple response component ± 5 GHz is in the range of 39 ± 4 GHz and 49 ± 4 GHz, none of which falls within the passband of the filter. The third and higher order multiple response components may fall in the pass band of the filter, but are ignored here as having lower levels than the second order multiple response components.

  Therefore, when each frequency is set as described above, it can be considered that the level of the signal output from the filter corresponds to the level of the target signal with high accuracy, which is detected by, for example, a detection circuit. From the detected values, it is possible to perform level calibration that specifies the level value of the target signal with high accuracy.

However, if the frequency variable width Fw is greater than or equal to the intermediate frequency f _IF , the above-described leak component of the local signal S _LOC and the secondary multiple response component fall within the pass band of the filter.

For example, as shown in FIG. 11, when the frequency variable width Fw and 8GHz (= ± 4GHz), the frequency _{f LOC} of the local signal _{S LOC} becomes a range of 22 ± 4 GHz, a part of the passband 27 ± 4 GHz filters It is in the range. Also, for example, the second-order multiple response component (2 × 5) + (22 ± 4) GHz is in the range of 32 ± 4 GHz, 2 × (22 ± 4) -5 GHz is in the range of 39 ± 8 GHz, and a part of each is Is in the passband of the filter.

In this way, when the leak component of the local signal S _LOC having a relatively large level or the low-order multiple response component enters the filter band, the level of the output signal of the filter accurately corresponds to the level of the target signal S _RF It becomes difficult to accurately grasp the level of the target signal S _RF from the level of this output signal.

In order to prevent this, conventionally, as shown in FIG. 12, the frequency variable range of the target signal S _RF is covered with a plurality of M (three in the figure) filters of different pass bands Band1 to Band3; A method is adopted to suppress the leak component of the local signal S _LOC falling within the frequency variable range of the target signal S _RF and the second-order multiple response component. In this case, for example, if pass bands Band1 to Band3 of each filter are set to a range that divides the frequency variable range (27 ± 4 GHz) of the target signal into three equal parts, while the frequency of the target signal is in Band1, The frequency is in the range lower than the lower limit of Band1, and the second-order multiple response component is in the range higher than the upper limit of Band1. Similarly, when the frequency of the target signal is in Band 2 or in Band 3, both the frequency of the local signal and the second-order multiple response component are outside the passband. Therefore, as described above, by using a plurality of filters having pass bands such that the target signal and the local signal are not simultaneously output, and the target signal and the second-order multiple response component are not simultaneously output, It is possible to suppress the unnecessary signal component and extract only the target signal.

  In this case, as shown in FIG. 13, a plurality of filters 2A, 2B and 2C having different passbands and switches 3 and 4 for selectively switching these are provided on the output side of the mixer 1 according to the frequency of the target signal. The filter switching is performed.

  As described above, a technique for reducing unnecessary signal components included in the frequency variable range of the target signal using a filter in a pass band narrower than the frequency variable range is conventionally widely known (for example, Patent Document 1).

Unexamined-Japanese-Patent No. 7-22971

  However, as described above, in the method of switching a plurality of filters in which respective pass bands are set so that the unnecessary signal component and the target signal are not simultaneously output, the entire circuit becomes large-scale, the cost increases, and the device becomes large. Have the problem of In addition, switches 3 and 4 for selecting filters have large losses in the several 10 GHz band as in the above frequency example, and when configuring a selection circuit with a large number of switches, it is necessary to connect switches with a small number of switches in multiple stages. There is a problem with further increase in losses due to switches.

  The present invention solves these problems so that even if the frequency variable width of the target signal is wider than the intermediate frequency, the leak component of the local signal included in the output signal of the mixer and the low-order multiple are reduced with a small number of filters. A signal generator capable of sufficiently suppressing the response component with respect to the target signal, accurately grasping the level of the target signal from the level of the output signal of the filter, enabling cost reduction and downsizing, and a signal generation method therefor It is intended to be provided.

In order to achieve the above object, a signal generator according to claim 1 of the present invention,
An intermediate frequency signal generation circuit (21) that generates and outputs an intermediate frequency signal of a predetermined frequency;
A local signal generation circuit (27) for outputting a local signal whose frequency is varied in a predetermined range, a mixer (26) for mixing the local signal and the intermediate frequency signal, the output of the mixer, the intermediate frequency signal and the local A frequency conversion circuit (25) including a filter circuit (28) for extracting a frequency component of sum of signals or a frequency component of difference as a target signal;
First level varying means (22) for varying the level of the intermediate frequency signal input to the frequency conversion circuit;
Second level varying means (30) for receiving the signal output from the frequency conversion circuit, varying the level thereof, and outputting it;
Target signal frequency specifying means (51) for specifying a desired frequency of the target signal;
Local signal frequency setting means (52) for setting the frequency of the local signal corresponding to the frequency of the target signal specified by the target signal frequency specifying means in the frequency conversion circuit;
When the frequency of the local signal corresponding to the frequency of the designated target signal and the frequency of the low-order multiple response component generated by the intermediate frequency signal and the local signal are both outside the passband of the filter circuit The gain of the first level variable means required for the level of the signal output from the second level variable means to be the target value is a first reference value, and the gain of the second level variable means. When the gain is a second reference value, the frequency of the local signal is outside the passband of the filter circuit, and the frequency of the low-order multiple response component is inside the passband of the filter circuit. The gain of the first level variable means is lower than the first reference value with respect to the level of the target signal contained in the output signal of the mixer. The first predetermined amount necessary to make the maximum level of the rutile response component smaller than the allowable value is a value smaller than the first predetermined amount, and the gain of the second level variable means is the first based on the second reference value. If the value of the local signal is within the passband of the filter circuit and the frequency of the low-order multiple response component is outside the passband of the filter circuit The level of the leak component of the local signal is made equal to or less than the allowable value with respect to the level of the target signal included in the output signal of the mixer by the gain of the first level variable means with respect to the first reference value. To increase the value of the second level variable means by a value smaller than the second reference value by the second predetermined amount. Characterized in that it comprises a setting means (53).

A signal generator according to claim 2 of the present invention is the signal generator according to claim 1, wherein
The gain setting means is a gain value from gain information storage means (54) which stores in advance gain values for setting in the first level variable means and the second level variable means for each frequency of the target signal. Are read out and set as the first level changing means and the second level changing means.

In the signal generator according to claim 3 of the present invention, in the signal generator according to claim 1 or 2,
Correction data storage means (56) storing data of the level of the signal output from the second level variable means or the difference between the level and the target value as correction data for each frequency of the target signal;
The correction data stored in the correction data storage means corrects the level of the intermediate frequency signal input to the frequency conversion circuit or the level of the signal output from the second level change means, And level error correction means (57) for matching the level of the signal output from the level change means of the above to the target value.

In the signal generator according to claim 4 of the present invention, in the signal generator according to claim 1 or 2,
Level detection means (35) for detecting the level of the signal output from the second level variable means;
The level of the intermediate frequency signal input to the frequency conversion circuit or the level of the signal output from the second level varying means is corrected so that the level detected by the level detecting means matches the target value. And a level error correction means (57 ').

In the signal generator according to claim 5 of the present invention, in the signal generator according to any one of claims 1 to 4,
The filter circuit of the frequency conversion circuit is a switch (29a, 29b) that selectively uses a plurality of filters (28a, 28b) having different passbands and a filter that passes the frequency of the target signal among the plurality of filters. ) And,
The gain setting means sets the gains of the first level changing means and the second level changing means for each pass band of the plurality of filters.

Also, according to the signal generator method of claim 6 of the present invention,
An intermediate frequency signal generation circuit (21) that generates and outputs an intermediate frequency signal of a predetermined frequency;
A local signal generation circuit (27) for outputting a local signal whose frequency is varied in a predetermined range, a mixer (26) for mixing the local signal and the intermediate frequency signal, the output of the mixer, the intermediate frequency signal and the local A frequency conversion circuit (25) including a filter circuit (28) for extracting a frequency component of sum of signals or a frequency component of difference as a target signal;
First level varying means (22) for varying the level of the intermediate frequency signal input to the frequency conversion circuit;
A signal generator method of a signal generator, comprising: second level variable means (30) for receiving the signal outputted from the frequency conversion circuit, varying the level thereof, and outputting it.
Specifying a desired frequency of the target signal;
Setting the frequency of the local signal corresponding to the frequency of the specified target signal in the frequency conversion circuit;
When the frequency of the local signal corresponding to the frequency of the designated target signal and the frequency of the low-order multiple response component generated by the intermediate frequency signal and the local signal are both outside the passband of the filter circuit A first reference value for the gain of the first level variable means, and a gain for the second level variable means required for the level of the signal output from the second level variable means to be a target value Where the frequency of the local signal is outside the passband of the filter circuit, and the frequency of the low-order multiple response component is inside the passband of the filter circuit. The gain of the first level varying means is lower than the first reference value relative to the level of the target signal contained in the output signal of the mixer. The first predetermined amount necessary to make the maximum level of the multiple response component smaller than the allowable value is a smaller value, and the gain of the second level variable means is the first position than the second reference value. If the value is set to a large value by a fixed amount, the frequency of the local signal is inside the passband of the filter circuit, and the frequency of the low-order multiple response component is outside the passband of the filter circuit. The gain of the first level varying means is set to a level of the leak component of the local signal below the allowable value with respect to the level of the target signal contained in the output signal of the mixer from the first reference value. To make the gain of the second level variable means smaller by the second predetermined amount than the second reference value. Characterized in that it comprises a step of constant.

  As described above, in the present invention, when the frequency variable range of the target signal is wider than the intermediate frequency, unnecessary signal components of the leak component of the local signal and the low-order multiple response component appear in the passband of the filter circuit. Even if there is an unnecessary signal component with respect to the level of the target signal, the gains of the first level variable means and the second level variable means are reciprocally changed without finely dividing the pass band of the filter. It can be suppressed below the allowable value, and cost reduction and miniaturization can be achieved.

  In addition, by correcting the difference between the level of the signal output from the second level varying means and the target value, it is possible to output a target signal whose level exactly matches the target value for each frequency.

Configuration diagram of an embodiment of the present invention Diagram for explaining the operation of the embodiment Diagram for explaining the operation of the embodiment Diagram for explaining the operation of the embodiment Configuration diagram of another embodiment of the present invention Configuration diagram of another embodiment of the present invention Frequency relationship diagram when the frequency range of the target signal is wider Signal generator corresponding to the frequency example of FIG. 7 Configuration diagram of frequency conversion circuit Frequency relationship diagram of frequency conversion when the frequency variable range is narrow Frequency relationship diagram of frequency conversion when the frequency variable range is wide Frequency relationship diagram when the passband is divided when the variable frequency range is wide Block diagram of frequency conversion circuit in case of dividing pass band

Hereinafter, embodiments of the present invention will be described based on the drawings.
FIG. 1 shows the basic configuration of a signal generator 20 to which the present invention is applied.

The signal generator 20 includes an intermediate frequency signal generating circuit 21, a first level changing means 22, a frequency converting circuit 25, a second level changing means 30, an output terminal 31, and a control unit 50. An intermediate frequency signal S _IF of an intermediate frequency f _IF (for example, 5 GHz) is converted to a target signal S _RF of a higher frequency f _RF (for example, 23 to 31 GHz) by frequency conversion processing of the heterodyne method and output.

The intermediate frequency signal generation circuit 21 generates and outputs an intermediate frequency signal S _IF of a predetermined intermediate frequency f _IF (for example, 5 GHz). The intermediate frequency signal _SIF is a signal (which can be designated by the control unit 50) including information (including not only modulation information but also the frequency and level of the carrier) necessary for the test of communication devices such as portable terminals. Here, it is simply described as a non-modulated signal.

The first level variable means 22 is for receiving the intermediate frequency signal S _IF outputted from the intermediate frequency signal generation circuit 21 and changing its level for output, and is a variable attenuator, a gain variable amplifier or the like. The intermediate frequency signal S _IF is amplified or attenuated with a gain G1 specified by the control unit 50, and is output. Here, although an example in which the first level variable means 22 is provided separately from the intermediate frequency signal generation circuit 21 is shown, the first level variable means 22 generates an intermediate frequency signal in the intermediate frequency signal generation circuit 21. It may be provided in the middle of processing.

The intermediate frequency signal S _IF 'output from the first level variable means 22 is input to the double balanced mixer (DBM) 26 of the frequency conversion circuit 25 and the local signal S output from the local signal generator 27. Mixed with _LOC . Local signal generator 27, under control of the control unit 50 (in this example, 18～23GHz) local signal _S a predetermined range frequency _{f LOC} of _LOC outputting shall be variable.

The output signal of the mixer 26 is input to the filter circuit 28 having a pass band equal to the frequency range (23 to 31 GHz) of the target signal S _RF . The filter circuit 28 of this embodiment is constituted by a single band pass type filter, but as will be described later, when the frequency range of the target signal S _RF is wider, the plural filters are switched. It may be used.

Frequency example of this embodiment, since the intermediate frequency _f IF (= 5GHz) than the target signal _{S RF} frequency variable width Fw (= 8 GHz) is wide example, as shown in FIG. 11, the target signal _{S RF} In the lower frequency range (23 to 26 GHz) of the frequency f _RF , the second-order multiple response component S _IM appears in the higher frequency range (28 to 31 GHz) of the pass band of the filter and the frequency of the target signal S _RF When f _RF is in the high frequency range (28 to 31 GHz), the leak component of the local signal S _LOC appears in the low frequency range (23 to 26 GHz) of the pass band of the filter. Further, when the frequency of the target signal S _RF is between the low band and the high band, the leak component of the secondary multiple response component S _IM and the local signal S _LOC is outside the pass band of the filter.

  The signal Sout output from the frequency conversion circuit 25 is input to the second level varying means 30. Similar to the first level variable means 22, the second level variable means 30 is composed of a variable attenuator, a variable gain amplifier, or a combination thereof, and receives the output signal Sout of the frequency conversion circuit 25 to control unit 50. Is amplified or attenuated with a gain G2 specified by

The signal Sout ′ (S _RF ) output from the second level variable means 30 is output to the outside through the output terminal 31.

  The control unit 50 has a target signal frequency designation unit 51, a local signal frequency setting unit 52, a gain setting unit 53, and a gain information storage unit 54.

The target signal frequency designation unit 51 designates the desired frequency f _RF of the target signal S _RF to be output from the output terminal 31 in response to the operation of the operation unit (not shown) or the like, and the local signal frequency setting unit 52 designates The frequency f _LOC of the local signal S _LOC corresponding to the determined frequency f _RF is set in the frequency conversion circuit 25.

The gain information storage section 54 allowed, for each region of the frequency of the target signal S _RF, the level of the output signal Sout 'outputted from the output terminal 31, relative to the level of the target signal S _RF contained in the output signal Gains G1 and G2 necessary for becoming equal to or less than the value are stored in advance, and gain setting means 53 refers to gain information storage means 54 to obtain gain G1 corresponding to the designated frequency of target signal S _RF , G2 is read out and set in the first level varying means 22 and the second level varying means 30, respectively.

Here, the gain values stored in the gain information storage means 54 will be described.
The first condition is that the leak component of the local signal S _LOC and the second-order multiple response component S _IM do not enter the pass band of the filter circuit 28, and the frequency region of the target signal S _{RF in} that case is the first condition region, in this state, each part of the signal generator 20 with margin operating normally, the level of the signal output (in this case, be regarded as a target signal S _RF level) to the output terminal 31 is the target value (e.g. -16 dBm) These gains G1 and G2 are set as reference values Gr1 and Gr2, respectively.

Also, second-order multiple response component S _IM enters the high-frequency side of the pass band of the filter circuit 28, a case where the leak component of the local signal S _LOC is outside the pass band of the filter circuit 28 as a second condition, in which case The frequency region of the target signal _SRF of In this case, the level of second-order multiple response component S _IM in question, relative to the amount of decrease in the level of the intermediate frequency signal by utilizing the fact that has a property of decreasing in the next several times, first level than the reference value Gr1 the gain G1 of the variable means 22, a predetermined amount .DELTA.Ga (> 0) and only the smaller Gr1-.DELTA.Ga, and the level of second-order multiple response component _{S IM} appearing in the mixer output lowering 2 × .DELTA.Ga min. Then, in order to compensate for the level reduction of the target signal S _RF due to the gain reduction, the gain G2 of the second level variable means 30 is set to a value Gr2 + ΔGa which is larger than the reference value Gr2 by a predetermined amount ΔGa (> 0). The level of the signal output from 31 is made to be the target value.

Also, the third condition is that the leak component of the local signal S _LOC enters the low band side of the pass band of the filter circuit 28 and the second-order multiple response component S _IM is outside the pass band of the filter circuit 28 in that case The frequency region of the target signal S _RF of In this case, the level of the leak component appearing in the mixer output, so that the allowable value or less relative to the level of the target signal S _RF, a predetermined amount than the reference value Gr1 the gain G1 of the first level varying means 22? Gb ( The gain G2 of the second level variable means 30 is set by a predetermined amount .DELTA.Gb (> 0) over the reference value Gr2 in order to compensate the level increase of the target signal S _RF due to the increase of the gain Gr1 + .DELTA.Gb by> 0). The level of the signal output from the output terminal 31 is set to the target value by setting the small value Gr2-ΔGb.

As described above, since the frequency variable range (the pass band width of the filter circuit) of the target signal S _RF is wider than the intermediate frequency, unnecessary signal components such as the leak component of the local signal S _LOC and the multiple response component S _IM Even when appearing in the pass band of the filter, the gains G1 and G2 of the first level variable means 22 and the second level variable means 30 are reciprocally changed to obtain the target signal S _RF level. the unnecessary signal components can be suppressed to less than the allowable value, yet can maintain the level of the target signal S _RF outputted from the output terminal 31 to the target value.

Hereinafter, specific numerical examples will be described.
The gains of the first level varying means 22 and the second level varying means 30 are within the range in which each part of the signal generator 20 normally operates around the first reference value Gr1 and the second reference value Gr2. Although it can be changed arbitrarily, to give one numerical example, Gr1 = Gr2 = 0 (dB), the level of the intermediate frequency signal output from the intermediate frequency signal generation circuit 21 is −10 dBm, the level 10 dBm of the local signal S _LOC , and the mixer The level of the target signal S _RF appearing at the output of 26 is −16 dBm, the level of the leak component of the local signal S _LOC is −30 dBm, and the second-order multiple response of 2f _IF + f _LOC may enter the passband of the filter circuit 28 The level of the component S _IM is −30 dBm.

FIG. 2 shows the frequency relationship of each component when the frequency of the target signal S _RF is in the region satisfying the first condition, and as described above, under the first condition, the leakage component of the local signal S _LOC or The second-order multiple response component S _IM of 2f _IF + f _LOC is outside the passband of the filter circuit 28, and the output of the mixer 26 in the passband of the filter circuit 28 is as shown in FIG. There is no unnecessary signal component of a size that can not be ignored with respect to the level of the target signal _{SRF, and} the level of the output signal of the filter circuit 28 can be regarded as corresponding to the level of the target signal _SRF . In the above numerical example, if the level of the target signal S _RF output from the second level variable means 30 is 0 dB in the pass band of the filter circuit 28 as shown in (b) of FIG. It will be 16 dBm. Also, the leakage component of the local signal S _LOC outside the passband of the filter circuit 28 and the second-order multiple response component S _IM of 2f _IF + f _LOC are greatly attenuated (eg, 40 dB or more) when passing through the filter circuit 28. Therefore, the influence on the level of the target signal S _RF can be ignored.

  When the frequency of the target signal is in the range satisfying the second condition, the gain of the first level varying unit 22 is set to a value Gr1-ΔGa which is smaller than the first reference value Gr1 by the first predetermined amount ΔGa, In order to compensate for the decrease in gain, the gain of the second level variable unit 30 is set to a value Gr2 + ΔGa which is larger than the second reference value Gr2 by a first predetermined amount.

The first predetermined amount ΔGa makes the maximum level of the low-order multiple response component lower than the allowable value (for example, 20 dB: 1/100 in power conversion) with respect to the level of the target signal S _RF included in the output signal of the mixer 26 Is the value to be

The level of the multiple response component changes its level response depending on its order. For example, the level of multiple response component _{S IM} frequencies _2f IF _{+ f LOC} varies in the following several times harmonics of the intermediate frequency signal (twice in this case), when the level of the intermediate frequency signal, for example 10dB lower, Part 2 It will decrease by 20 dB.

Therefore, temporarily, as shown in FIG. 3A, the target signal S _RF included in the output signal of the mixer 26 with the gain of the first level variable means 22 being the first reference value Gr1 (= 0 dB). level -16dBm _of, 2f when IF _{+ f LOC} level of multiple response component _{S IM} of the -30 dBm, as described above, the level of the intermediate frequency signal lower 10dB and (.DELTA.Ga = 10), in FIG. 3 (b as a), becomes a -26dBm down also target signal _{S RF} level 10 _dB, 2f IF _{+ f} level of multiple response component _{S IM} of _LOC is twice of 20dB down to -50dBm, and the object signal _{S RF} The level is below the allowable value (20 dB). Finally, the gain of the second level variable means 30 is set to a value 10 dB larger than the second reference value Gr2 (= 0 dB) by the first predetermined amount ΔGa (= 10). As in c), the level of the target signal S _RF outputted from the second level variable means 30 returns to the original level (-16 dBm), and the level of the multiple response S _IM increases by 10 dB to -40 dBm, It becomes less than the allowable value (20 dB) with respect to the signal S _RF . In this case, since the leak component S _LOC 'of the local signal S _LOC outside the passband is largely attenuated when passing through the filter circuit 28, even if it is amplified by 10 dB by the second level variable means 30, the multiple response It is sufficiently lower than the level of S _IM and the influence on the level of the target signal S _RF can be ignored.

Further, when the frequency of the target signal S _{RF is in} a region satisfying the third condition, the gain of the first level varying means 22 is set to a value Gr1 + ΔGb larger by a second predetermined amount ΔGb than the first reference value Gr1. In order to compensate for this gain increase, the gain of the second level variable means 30 is set to a value Gr2-ΔGa which is smaller than the second reference value Gr2 by a second predetermined amount ΔGb.

Here, the second predetermined amount ΔGb makes the level of the leak component S _LOC ′ of the local signal S _LOC relatively lower than the allowable value with respect to the level of the target signal S _RF included in the output signal of the mixer 26 It is a value.

Therefore, as shown in FIG. 4A, temporarily, the gain of the first level variable means 22 is the target signal S _RF included in the output signal of the mixer 26 when it is the first reference value Gr1 (= 0). When the level is −16 dBm and the level of the leak component S _LOC ′ of the local signal S _LOC is −30 dBm, as described above, the level of the intermediate frequency signal is increased by 10 dB (ΔGb = 10), as shown in FIG. As described above, the level of the target signal S _RF is increased by 10 dB to −6 dBm, and is equal to or higher than the allowable value (20 dB) with respect to the level of the leak component S _LOC ′ of the local signal S _LOC . Finally, the gain of the second level variable unit 30 is set to a value -10 dB smaller than the second reference value Gr2 (for example, 0 dB) by the second predetermined amount ΔGb (= 10). As shown in (c), the level of the target signal S _RF output from the second level variable means 30 returns to the original level (-16 dBm), and the level of the leakage component S _LOC 'is also reduced by 10 dB to -40 dBm. Or less than the allowable value (20 dB) with respect to the target signal S _RF . In this case, as the level of the intermediate frequency signal increases, the level of the second-order multiple response component S _IM increases to −10 dBm at the mixer output, but is greatly attenuated when passing through the filter circuit 28, and Since the signal is further attenuated by 10 dB by the level varying means 30, it is sufficiently lower than the level of the leak component S _LOC 'of the local signal and the influence on the level of the target signal S _RF can be ignored.

As described above, the level of the intermediate frequency signal input to the frequency conversion circuit 25 is increased or decreased by the first level variable means 22 so that the low order multiple response component or the leak component of the local signal is the passband of the filter circuit 28. be contained in, can be below the allowable value and the level for the target signal S _RF, target signal S _RF to increase or decrease changes by which to increase or decrease the level of the intermediate frequency signal at a first level varying means 22 Can be compensated back by the inverse increase / decrease change of the gain of the second level variable unit 30, and the level of the signal output from the second level variable unit 30 is always set to the level of the target signal _SRF . A consistent state can be maintained within tolerances.

The signal generator 20 of the above embodiment, since the level of the signal Sout 'outputted from the output terminal 31 considered to be consistent with high accuracy to the level of the target signal S _RF, as shown in FIG. 5 The actual power Pout of the output signal is measured for each frequency by the power meter 60 connected to the output terminal 31, and the difference between the measured value or the measured value and the target value (which may be a gain error) is corrected as correction data. It is possible to store in the data storage means 56 and use this correction data to more strictly manage the output level of the target signal _SRF .

For example, as shown in FIG. 5, the level error correction means 57 uses the correction data (level error, gain error) corresponding to the specified frequency of the target signal S _RF to perform the second level change means 30. The level of the signal output from the output terminal 31 can be accurately adjusted to the target value by correcting the gain of the above and the input level of the intermediate frequency signal to the frequency conversion circuit 25.

  Further, as shown in FIG. 6, in order to obtain the correction data, it is possible to detect the level of the signal output from the second level variable means 30 by a level detector 35 comprising a detector or the like. .

  In this configuration, the output signal of the second level varying means 30 is branched by the coupler 32, one of which is input to the output terminal 31, and the other input to the level detector 35. The level of the signal input to the output terminal 31 and the level detector 35 is reduced with respect to the level of the output signal of the level detector 35. However, if there is no loss of the coupler 32 and the branch ratio is 1: 1, the level detector The level detected at 35 is equal to the level of the signal output from the output terminal 31.

Therefore, a gain error (or a level difference between the detected value and the target value) for making the level (power) detected for each frequency of the designated target signal coincide with the target value is obtained by the level error correction means 57 '. If the gain of the second level varying means 30 is corrected by this error or the input level of the intermediate frequency signal S _IF to the frequency conversion circuit 25 is corrected, the level of the signal output from the output terminal 31 becomes the target value. It can be precisely adjusted. The information on the error is stored in storage means (not shown), and in the steady state, using the stored error data, the level detector 35 newly generates a signal for each frequency at the timing when the calibration is necessary. It is also possible to detect the level and obtain new error information from the detected level to update the storage content of the storage means.

In the above embodiment, the intermediate frequency 5 GHz, the local signal S _LOC frequency range 22 ± 4 GHz, and the target signal S _RF frequency range 27 ± 4 GHz as an example where the frequency range of the target signal S _RF is wider than the intermediate frequency. In this frequency example, the frequency of the local signal S _{LOC and} the frequency of the second-order multiple response component S _IM simultaneously with the frequency of the target signal S _RF occur in the pass band of the filter. Because I did not, I was able to cope with one filter.

However, if the wider the frequency range of the target signal S _RF for frequencies of interest signal S _RF, the pass band of the filter frequency of the second-order multiple response component S _IM of the local signal S _LOC simultaneously In this case, the frequency of the local signal S _{LOC and} the frequency of the second-order multiple response component S _IM do not simultaneously appear with respect to the frequency of the target signal S _RF . It is sufficient to switch the filter, and it is not necessary to use the narrow band filter which passes only the target signal S _RF as in the prior art.

FIG. 7 shows the frequency relationship in the case where the frequency of the local signal S _{LOC and} the frequency of the second-order multiple response component S _IM simultaneously enter the pass band of the filter with respect to the frequency of the target signal S _RF .

In this example, the intermediate frequency 5 GHz, the local signal S _LOC frequency range 22 ± 6 GHz, and the target signal S _RF frequency range 27 ± 6 GHz, the horizontal axis represents the frequency of the target signal S _RF and the vertical axis represents the unnecessary signal component. And the frequency of

To changes to the desired signal _{S RF} frequency _{f RF 21~33GHz,} frequency _{f LOC} of the local signal _{S LOC} varies from 16~28GHz, but the range of less than 16～21GHz, target signal _{S RF} frequency range It is not necessary to consider it because it is lower than the lower limit of Further, the frequency f _IM of the second-order multiple response component S _IM varies from 26 to 38 GHz, but in the range exceeding 33 GHz, it is higher than the upper limit of the frequency range of the target signal S _RF .

Also, when the frequency of the target signal S _RF is in the range of 21 to 28 GHz, the frequency of the second-order multiple response component S _IM appears in the range of 26 to 33 GHz, and the frequency of the target signal S _RF is in the range of 26 to 33 GHz, the local Since the frequency of the signal S _LOC appears in the range of 21 to 28 GHz, when the pass band of the filter is set to the frequency range 21 to 33 GHz of the target signal S _RF as described above, the second-order multiple response component S _IM and the local signal S The unwanted signal component of the _LOC leak component simultaneously appears at the common target frequency S _RF .

In order to prevent this, for example, as shown in FIG. 7, the entire frequency range of the target signal S _RF is divided into a passband Band 1 of 21 to 28 GHz and a pass band Band 2 of 28 to 33 GHz. In the pass band Band1, when the frequency of the target signal S _RF is in the range of 21 to 23 GHz, only the second-order multiple response component S _IM up to 26 to 28 GHz appears, and the frequency of the target signal S _RF is in the range of 26 to 28 GHz , Only the leakage component of the local signal S _LOC from 21 to 23 GHz appears, and both unwanted signal components do not appear in the frequency range of 23 to 26 GHz of the target signal S _RF (strictly considering the boundary value There is a need). Further, unnecessary signal components other than the target signal do not appear in the pass band Band2.

Therefore, as shown in FIG. 8, the filter circuit 28 is composed of the filter 28a in the passband Band1, the filter 28b in the passband Band2, and the switches 29a and 29b for switching them, and the gain information storage means 54 includes two filters. 28a, may be set to gain information for the pass band of 28b, if provided filter switching means 58 for switching control of the filter according to the frequency of the designated object signal S _RF, 2 single filter 28a, at 28b It can cover a wide frequency range.

In the above embodiment has described the case of extracting a target signal S _RF as a frequency component of the sum of the intermediate frequency signal and the local signal S _LOC, the desired signal S _RF, a difference of the intermediate frequency signal S _IF and the local signal S _LOC The present invention can be similarly applied to the case of extracting as the frequency component of

  20: Signal generator, 21: Intermediate frequency signal generator, 22: First level variable means, 25: Frequency conversion circuit, 26: Mixer, 27: Local signal generator, 28: Filter Circuits 28a, 28b: filters, 29a, 29b: switches 30, 30: second level variable means, 31: output terminal 32, 32: coupler, 35: level detector, 50: control unit, 51: Target signal frequency specifying means, 52: Local signal frequency setting means, 53: Gain setting means, 54: Gain information storage means, 56: Correction data storage means, 57, 57 ': Level error correction Means, 58: Filter switching means, 60: Power meter

Claims (6)

An intermediate frequency signal generation circuit (21) that generates and outputs an intermediate frequency signal of a predetermined frequency;
A local signal generation circuit (27) for outputting a local signal whose frequency is varied in a predetermined range, a mixer (26) for mixing the local signal and the intermediate frequency signal, the output of the mixer, the intermediate frequency signal and the local A frequency conversion circuit (25) including a filter circuit (28) for extracting a frequency component of sum of signals or a frequency component of difference as a target signal;
First level varying means (22) for varying the level of the intermediate frequency signal input to the frequency conversion circuit;
Second level varying means (30) for receiving the signal output from the frequency conversion circuit, varying the level thereof, and outputting it;
Target signal frequency specifying means (51) for specifying a desired frequency of the target signal;
Local signal frequency setting means (52) for setting the frequency of the local signal corresponding to the frequency of the target signal specified by the target signal frequency specifying means in the frequency conversion circuit;
When the frequency of the local signal corresponding to the frequency of the designated target signal and the frequency of the low-order multiple response component generated by the intermediate frequency signal and the local signal are both outside the passband of the filter circuit The gain of the first level variable means required for the level of the signal output from the second level variable means to be the target value is a first reference value, and the gain of the second level variable means. When the gain is a second reference value, the frequency of the local signal is outside the passband of the filter circuit, and the frequency of the low-order multiple response component is inside the passband of the filter circuit. The gain of the first level variable means is lower than the first reference value with respect to the level of the target signal contained in the output signal of the mixer. The first predetermined amount necessary to make the maximum level of the rutile response component smaller than the allowable value is a value smaller than the first predetermined amount, and the gain of the second level variable means is the first based on the second reference value. If the value of the local signal is within the passband of the filter circuit and the frequency of the low-order multiple response component is outside the passband of the filter circuit The level of the leak component of the local signal is made equal to or less than the allowable value with respect to the level of the target signal included in the output signal of the mixer by the gain of the first level variable means with respect to the first reference value. To increase the value of the second level variable means by a value smaller than the second reference value by the second predetermined amount. Signal generator, characterized in that it comprises a setting means (53).   The gain setting means is a gain value from gain information storage means (54) which stores in advance gain values for setting in the first level variable means and the second level variable means for each frequency of the target signal. The signal generator according to claim 1, wherein the first level changing means and the second level changing means are read out and set as the first level changing means. Correction data storage means (56) storing data of the level of the signal output from the second level variable means or the difference between the level and the target value as correction data for each frequency of the target signal;
The correction data stored in the correction data storage means corrects the level of the intermediate frequency signal input to the frequency conversion circuit or the level of the signal output from the second level change means, The signal generator according to claim 1 or 2, further comprising: level error correction means (57) for making the level of the signal output from the level variable means equal to the target value. Level detection means (35) for detecting the level of the signal output from the second level variable means;
The level of the intermediate frequency signal input to the frequency conversion circuit or the level of the signal output from the second level varying means is corrected so that the level detected by the level detecting means matches the target value. A signal generator according to claim 1 or 2, characterized in that level error correction means (57 ') are provided. The filter circuit of the frequency conversion circuit is a switch (29a, 29b) that selectively uses a plurality of filters (28a, 28b) having different passbands and a filter that passes the frequency of the target signal among the plurality of filters. ) And,
The gain setting means sets the gains of the first level changing means and the second level changing means for each pass band of the plurality of filters. Signal generator as described. An intermediate frequency signal generation circuit (21) that generates and outputs an intermediate frequency signal of a predetermined frequency;
A local signal generation circuit (27) for outputting a local signal whose frequency is varied in a predetermined range, a mixer (26) for mixing the local signal and the intermediate frequency signal, the output of the mixer, the intermediate frequency signal and the local A frequency conversion circuit (25) including a filter circuit (28) for extracting a frequency component of sum of signals or a frequency component of difference as a target signal;
First level varying means (22) for varying the level of the intermediate frequency signal input to the frequency conversion circuit;
A signal generator method of a signal generator, comprising: second level variable means (30) for receiving the signal outputted from the frequency conversion circuit, varying the level thereof, and outputting it.
Specifying a desired frequency of the target signal;
Setting the frequency of the local signal corresponding to the frequency of the specified target signal in the frequency conversion circuit;
When the frequency of the local signal corresponding to the frequency of the designated target signal and the frequency of the low-order multiple response component generated by the intermediate frequency signal and the local signal are both outside the passband of the filter circuit A first reference value for the gain of the first level variable means, and a gain for the second level variable means required for the level of the signal output from the second level variable means to be a target value Where the frequency of the local signal is outside the passband of the filter circuit, and the frequency of the low-order multiple response component is inside the passband of the filter circuit. The gain of the first level varying means is lower than the first reference value relative to the level of the target signal contained in the output signal of the mixer. The first predetermined amount necessary to make the maximum level of the multiple response component smaller than the allowable value is a smaller value, and the gain of the second level variable means is the first position than the second reference value. If the value is set to a large value by a fixed amount, the frequency of the local signal is inside the passband of the filter circuit, and the frequency of the low-order multiple response component is outside the passband of the filter circuit. The gain of the first level varying means is set to a level of the leak component of the local signal below the allowable value with respect to the level of the target signal contained in the output signal of the mixer from the first reference value. To make the gain of the second level variable means smaller by the second predetermined amount than the second reference value. Signal generating method of a signal generator, which comprises a step of constant.

Images