JP3010404B2 - Gain detection device and automatic gain control device for linear circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gain detection device for detecting the gain of a linear circuit and an automatic gain control device.

[0002]

2. Description of the Related Art In a linear circuit such as an amplifier used in various electronic devices, a gain changes according to a change in temperature or a frequency of a signal. Levels fluctuate.

[0003] In various measuring instruments in which such level fluctuations cannot be ignored, the output level is stabilized by, for example, an automatic level controller (ALC) 10 as shown in FIG. This device 10 detects an output signal of the amplifier 1 by a detector 11 in order to stabilize an output level of the amplifier 1 as a linear circuit, and detects a low-pass filter 1 from the detected output.
2 and a preset reference voltage Vr are input to a differential amplifier 13, and a variable gain circuit 2 inserted on the input side of the amplifier 1 so that the differential output approaches zero. Is controlled to keep the level of the signal output from the amplifier 1 constant.

However, such an automatic level control device can stabilize the output level of a continuous signal having a constant average amplitude, such as a non-modulated signal or an AM modulated signal, but cannot generate a signal similar to a quadrature modulated signal. In the case of a signal whose amplitude is not constant and whose level changes in a burst, the gain changes according to the average change in the amplitude, and the linearity between the input signal and the output signal is lost. There was a problem that would be. It is also conceivable to detect the gain variation of the amplifier 1 itself from the value of the DC voltage Vs of the automatic level control device. However, since the voltage Vs includes the level variation of the input signal, Amplifier 1
Cannot be accurately detected.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. A gain detecting device capable of accurately detecting the gain of a linear circuit independently of a signal waveform, and a gain detecting device for the linear circuit using the gain detecting device. It is an object of the present invention to provide an automatic gain control device capable of stabilizing a gain.

[0006]

In order to solve the above-mentioned problems, a linear circuit gain detection apparatus according to the present invention comprises a first integrator for integrating a signal inputted to a linear circuit, and a signal outputted from the linear circuit. A second integrator for integrating the first and second signals;
Synchronizing means for synchronizing the integration periods of the integrator and the second integrator, and a gain calculator for calculating a ratio between the output of the first integrator and the output of the second integrator after the integration period And

Further, the automatic gain control apparatus for a linear circuit according to the present invention comprises a first integrator for integrating a signal input to a linear circuit capable of changing a gain, and an integrated circuit for integrating a signal output from the linear circuit. A second integrator, a synchronizing means for synchronizing the integration periods of the first and second integrators, an output of the first integrator after the integration period, and the second integrator A gain calculator for calculating a ratio to the output of the linear circuit, comparing the calculated value of the gain calculator with a preset reference value, and increasing the gain of the linear circuit in a direction in which the calculated value becomes equal to the reference value. Variable gain control means.

[0008]

With this configuration, in the gain detection device for a linear circuit according to the present invention, the signal input to the linear circuit and the output signal are the same in the first integrator and the second integrator, respectively. , And a ratio between the integrated values is calculated as a value corresponding to the gain of the linear circuit.

Further, in the automatic gain control apparatus for a linear circuit according to the present invention, the gain of the linear circuit is variably controlled so that the value calculated by the gain detection apparatus approaches a preset reference value.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a linear circuit section 20 of a quadrature modulation signal generator.

The linear circuit section 20 converts a modulated output signal, which has been quadrature-modulated by the quadrature modulator 21 with the two modulation signals I and Q, to a desired frequency by a frequency mixing type frequency converter 30 and outputs the converted output signal. Is output through a variable gain circuit 31 and an amplifier 32.

As shown in FIG. 2, a quadrature modulator 21 divides a signal of a predetermined frequency from a carrier signal generator 22 into two local signals having phases different from each other by 90 degrees by a 90 ° hybrid 23, and transmits these local signals. The signals and the modulated signals I and Q are mixed by mixers 24 and 25, and a signal obtained by adding the respective mixed outputs by a power combiner 26 is output as a modulated output signal.

Therefore, as shown in FIG. 3, when the amplitude of each modulation signal is I and Q, the amplitude value of this modulation output signal is from the origin of the point P of the coordinates (I, Q) on the rectangular coordinates. ^Is a value proportional to the distance (I ² + Q ² ) ^1/2 and also proportional to the amplitude of each modulated signal. That is, the quadrature modulator 21
Is a linear circuit that outputs a signal proportional to the amplitude of the input signal, like the frequency converter 30, the gain variable circuit 31, and the amplifier 32. The variable gain circuit 31 is composed of an attenuator capable of varying the amount of attenuation externally and a programmable amplifier capable of varying the gain.

The gain detecting device 35 for detecting the gain of the linear circuit section 20 has two modulated signals I and Q as values corresponding to the amplitude of the signal input to the linear circuit section 20.
An input level calculator 36 for calculating the sum of the squares of (I ² + Q ² ) is provided.

The gain detector 35 includes a detector 37 for detecting the output signal of the linear circuit section 20 and an output level calculator 38 for calculating the square (D ² ) of the detection output D. I have.

The output of the input level calculator 36 and the output of the output level calculator 38 are connected to a switch 3 which is turned on and off synchronously.
The signals are input to the first integrators 41 and 42 via the reference numerals 9 and 40, respectively.

The first integrator 41 is connected to the input level calculator 3
The output of No. 6 is integrated while the switch 39 is closed, and the integrated output is output to a voltage comparator 43 and a gain calculator 44 which will be described later. When a high-level reset signal R is received, the integrated output is made zero. The second integrator 42 integrates the output of the output level calculator 38 while the switch 40 is closed, outputs the integrated output to a gain calculator 44 described later, and receives the high-level reset signal R. And its integral output to zero.

The voltage comparator 43 outputs a low level when the output voltage of the first integrator 41 is lower than the reference voltage Vr, and outputs a high level voltage when the output voltage of the second integrator 42 is higher than the reference voltage Vr. I do. The aforementioned switch 39,
Reference numeral 40 denotes an ON state while the output of the voltage comparator 43 is at a low level, and an OFF state while the output of the voltage comparator 43 is at a high level.

The gain calculator 44 calculates the ratio G between the output A of the first integrator 41 and the output B of the second integrator 42 during the integration period T by the following equation. G = 10 · log (B / A) (1) where A = ∫ ^T (I ² + Q ² ) dt, B = ∫ ^T D ² d
t

Since the above equation (1) is equivalent to G = 20 · log [(B ^1/2 / T) / (A ^1/2 / T)], G is the input signal of the linear circuit section 20. Of the amplitude of the output signal and the effective value of the amplitude of the output signal, that is,
The gain of the linear circuit unit 20 is a value represented by a dB value.

When the output of the voltage comparator 43 goes high, the A / D converter 45 converts the calculation result G of the gain calculator 44 into a digital value, sends it to the control unit 50, and controls the control unit 50. The measurement completion signal S is output to the unit 50.

The control unit 50 constituted by a microcomputer forms an automatic gain control device together with the gain detection device 35, and is provided with a gain control means 51 and a reset means 52.

The gain control means 51 latches the gain value G of the linear circuit section 20 output as a digital value from the gain detection device 35 in response to the measurement completion signal.
And a predetermined reference gain Gr. When G is larger than Gr, the gain of the variable gain circuit 31 is reduced by the difference. Conversely, when G is smaller than Gr, the gain of the variable gain circuit 31 is reduced by the difference. Increase.

After the gain value G is latched by the measurement completion signal S, the reset means 52 outputs a high-level reset signal R to the first and second integrators 41 and 42.

Therefore, one of the two integrators 41, 42
The integration period T is a period from when the reset state by the reset means 52 is released to when the output of the first integrator 41 reaches the reference voltage Vr. The integration period T varies depending on the amplitudes of the modulation signals I and Q, and is not always constant.

Next, the operation of this embodiment will be described with reference to the tie chart of FIG. This time chart shows changes in the signals of the respective units from the transmission of the high-level reset signal R from the control unit 50 to the transmission of the next reset signal as shown in FIG. When the reset signal is output at t0, the first and second integrators 41,
The integrated output at 42 becomes zero as shown in (e) and (h) of the figure, and the output of the voltage comparator 43 also becomes low level as shown at (i) in the figure. For this reason, the switches 39 and 40
Are both turned on.

After the reset of the two integrators 41 and 42 is released, during the period from t1 to t2, the modulation signals I and Q as shown in FIGS. When they are input to the burst circuit 20 in a burst form, a quadrature modulated signal of a desired frequency modulated by the two modulated signals I and Q is output from the linear circuit section 20.

The input level calculator 36 receiving the modulated signals I and Q outputs the sum of squares signal (I ² + Q ² ) as shown in FIG. 4D, and detects and outputs the quadrature modulated signal. The output level calculator 38 receiving ((f) in FIG. 4) outputs the squared signal (D ² ) as shown in (g) in FIG.

The first and second integrators 41 and 42 start integrating the square sum signal (I ² + Q ² ) and the square signal (D ² ) after reset release, respectively. 4 (e) and (h)) gradually increase from t1 to t2.

The gain calculator 44 having received each integrated output calculates the gain G according to the above-mentioned equation (1), and calculates the gain G by the A / D converter 4.
Output to 5

As shown in this figure, from t1 to t
If the output of the first integrator 41 does not reach the reference voltage Vr by the integration up to 2 o'clock, the digital conversion by the A / D converter 45 is not performed, and each integrated output becomes constant after t2.

Then, when the next modulated signals I and Q are input at t3, each integrated output increases again. When the output of the first integrator 41 reaches the reference voltage Vr at t4 due to the input of the modulation signal from time t3, the output of the voltage comparator 43 rises to a high level as shown in FIG.
The switches 39 and 40 are both turned off, and the A / D converter 45 converts the gain value G from the gain calculator 44 whose output is stabilized by turning off the switches 39 and 40 into a digital value. A high-level measurement completion signal ((j) in FIG. 4) is sent to the control unit 50.

The gain control means 51 of the control section 50 latches this new data at the rising timing of the measurement completion signal as shown in FIG. 4 (k), compares the new data with a predetermined reference gain Gr, and calculates the difference G The gain of the variable gain circuit 31 is reduced by -Gr.

On the other hand, the reset means 52 becomes high level at t6 when the measurement completion signal falls, and resets the two integrators 41 and 42. As a result of this reset, the outputs of both the integrators 41 and 42 become zero, and the output of the voltage comparator 43 also returns to the low level, so that the switches 39 and 40 return to the ON state and return to the state of t0.

Similarly, the ratio of the level obtained by integrating the level of the signal input to the linear circuit section 20 and the level of the signal output from the linear circuit section 20 for the same period is the linear circuit section. The gain of the linear circuit section 20 is variably controlled so that the calculated value approaches the reference value. For this reason, even if the gain of some circuits of the linear circuit section 20 fluctuates due to a temperature change or the like, the gain of the entire linear circuit section is stabilized to the reference gain Gr.

Since the reference voltage Vs is set in advance so that the integration period becomes extremely short with respect to the fluctuation of the gain of the linear circuit section 20 due to the temperature or the like, the gain of the entire linear circuit section 20 is always constant. The magnitude of the output signal with respect to the input signal (modulation signal) is kept constant.

[0037]

[Other Embodiments] In the above embodiment, two modulated signals I and Q are used.
Is used as an input signal, and the gain control of the linear circuit unit 20 that outputs a signal orthogonally modulated by the modulation signal is performed. However, this does not limit the present invention.
The present invention can be similarly applied to a linear circuit including only a frequency converter or a linear circuit including only an amplifier. In this case, when both input and output are provided in a single system, the integrated value of the detection output of the input signal and the output signal is obtained. What is necessary is just to control so that the gain calculated from the ratio between the two approaches the reference value.

The present invention can be applied not only to a linear circuit for handling a high-frequency signal but also to a pulse amplifier for amplifying a pulse signal, for example. In this case, the input pulse to the pulse amplifier and its output pulse may be directly input to the first and second integrators 41 and 42 via the switches 39 and 40.

In the above embodiment, the first signal on the input signal side is used.
When the output of the integrator reaches the reference voltage, the integration is terminated. However, the integration may be terminated when the integrated output on the output side reaches the reference value. Alternatively, the integration may be terminated when a predetermined number of output signals have been detected, or the timer may be activated after the reset is released, and the integration may be terminated when a certain time has elapsed from the reset release.

Further, in the above embodiment, the logarithmic operation is performed so that the gain of the linear circuit is expressed as dB, but the ratio of the amplitude value of the input signal to the amplitude value of the output signal is simply calculated as the gain of the linear circuit. And the gain of the linear circuit may be controlled based on the calculated value. As a method of this gain control, control may be performed by an average value of a plurality of calculated gain values.

[0041]

As described above, the linear circuit gain detection apparatus according to the present invention provides an integrated result of a level value of a signal input to a linear circuit and a signal output from the linear circuit in response to the input signal. Calculate the ratio of the level value of
Because it is configured to detect the gain of the linear circuit,
The gain of the linear circuit can be accurately detected irrespective of the level change of the input signal.

The automatic gain control device of the present invention variably controls the gain of the linear circuit so that the gain of the linear circuit detected by the gain detection device approaches a predetermined gain. The fluctuation can be stabilized irrespective of the modulation mode of the signal or the like and without losing the linearity of the output signal with respect to the input signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a quadrature modulator.

FIG. 3 is a diagram showing the relationship between the amplitude of a modulation signal and the amplitude of a modulation output signal.

FIG. 4 is a time chart for explaining the operation of one embodiment.

FIG. 5 is a configuration diagram of a conventional automatic level control device.

[Explanation of symbols]

 Reference Signs List 20 linear circuit unit 21 quadrature modulator 30 frequency converter 31 variable gain circuit 32 amplifier 35 gain detector 36 input level calculator 37 detector 38 output level calculator 39, 40 switch 41 first integrator 42 second integration Unit 43 voltage comparator 44 gain calculator 45 A / D converter 50 control unit 51 gain control means 52 reset means

Claims (2)

(57) [Claims] A first circuit for integrating a signal inputted to a linear circuit;
An integrator, a second integrator for integrating a signal output from the linear circuit, a synchronization unit for synchronizing the integration periods of the first and second integrators, A gain detection device for a linear circuit, comprising: a gain calculator for calculating a ratio between an output of the first integrator and an output of the second integrator. 2. A first integrator for integrating a signal input to a linear circuit having a variable gain, a second integrator for integrating a signal output from the linear circuit, and the first integrator. Synchronization means for synchronizing the integration periods of the integrator and the second integrator; a gain calculator for calculating a ratio between the output of the first integrator and the output of the second integrator after the integration period; Comparing the calculated value of the gain calculator with a preset reference value, and gain control means for varying the gain of the linear circuit in a direction in which the calculated value becomes equal to the reference value. Automatic gain control device.