JPH0423524A - Automatic gain control amplifier - Google Patents

Abstract

PURPOSE:To substantially fix phase characteristics in a control range by shifting the phase of an input signal by a phase shifting variable corresponding to the output signal of a level detecting means. CONSTITUTION:A variable phase sifting circuit 20 is connected to a variable attenuating means 10 and an amplifying means 12 in series so as to shift the phase of an input signal by a phase shifting variable corresponding to the output signal of the level detecting means 14. Since there is fixed relation between an attenuation ration in the means 10, i.e. the value of a control signal to the means 10, and a phase margin value from the means 10, the means 20 is provided with a phase shifting characteristic for canceling a change in the whole phase margin value of the means 10 by shifting the phase of the input signal by a phase shifting variable corresponding to the output signal of the means 14. Consequently, the phase margin value of the whole system can be maintained at a constant value independently of the level of the input signal.

Description

[Detailed Description of the Invention] [Summary] An automatic gain control amplifier, particularly an automatic gain control amplifier suitable as an automatic gain control amplifier provided for generating a phase shift amount control signal of a space diversity receiver, with variable attenuation. The purpose of this invention is to provide an automatic gain control amplifier in which the overall value around the phase does not change even if the gain variable range is set within a range where the value around the phase in the amplifier substantially changes. at least one stage of variable attenuation means for attenuating and outputting the signal at an attenuation ratio of at least one stage, at least one stage of amplification means connected in series with the variable attenuation means for amplifying and outputting the input signal, and a final stage for detecting the level of the signal. an automatic gain control amplifier comprising level detection means for outputting a signal corresponding to a level detected by the variable attenuation means as a control signal for the attenuation ratio of the variable attenuation means; The device is configured to include variable phase shift means which is connected and shifts the phase of the input signal by a phase shift amount according to the output signal of the level detection means.

[Industrial application field]

The present invention relates to an automatic gain control amplifier, and more particularly to an automatic gain control amplifier suitable as an automatic gain control amplifier provided for generating a phase shift amount control signal for a space dipacity receiving device.

[Conventional technology]

Fig. 7 is a diagram showing the configuration of a well-known space diversity receiver having an automatic gain control amplifier (AGCAMP). By combining the signal and the sub-signal from the sub-antenna installed in a different position from the main antenna by shifting the phase of one so that both are in phase, the interference waves caused by multipath are relatively attenuated. This eliminates the effects of multipath fading.

The main signal is supplied to the hybrid 514 via the amplifier 500 and the hybrid 502, and the sub signal is supplied to the hybrid 514 via the amplifier 506 and the endless phase shifter.
r: EPS), is supplied to the hybrid 514 via the amplifier 510 and the hybrid 512;
The two signals are combined and output via an amplifier 516.

On the other hand, the main signal and the sub signal are branched at hybrids 502 and 512, respectively, in order to generate the control signal of EP3508, pass through bandpass filters 504 and 518, and AG[: AMP 60 and 62, respectively, and are then sent to mixer 52.
At 0, both are combined. The signal synthesized by mixer 520 is input to control circuit 502, and the amount of phase shift in EPS 508 is controlled by its output.

Here, if the levels of the main signal and sub signal supplied to the mixer 520 are constant, the output of the mixer 520 becomes a signal corresponding to the phase difference between the two, and the phase shifter 50
The amount of phase shift at 8 is controlled to achieve in-phase synthesis.

Therefore, AGCAMP 60.62 supplies a signal at a constant level to mixer 520 regardless of level fluctuations of the main signal and sub signal in order to satisfy this condition.

By the way, the AGCAMP used in this space diversity receiver generally has a configuration in which a variable attenuator 100 and an amplifier 120 are connected in series in multiple stages, as shown in FIG. It is true.

The level of the output of the final stage amplifier 120 is detected by a wave detector 140 and amplified by an amplifier 142, and then the output is transmitted to each variable attenuator 100.
as a control voltage to the final stage amplifier 1.
The overall gain is automatically adjusted so that the level of the output signal 20 is constant regardless of the level of the input signal. The variable attenuator 100 is constructed using the characteristics of a PIN diode, as shown in FIG. The PIN diode has a property that the high frequency resistance R8 changes as shown in FIG. 10 in accordance with the value 10 of the current flowing in the forward direction within the frequency range reaching the microwave band. Therefore P.I.
The voltage division ratio between the N diode D1 and the resistor R3, that is, the attenuation amount AV also changes as shown in FIG. 10 in response to a change of 1°.

[Problem to be solved by the invention]

Since the diode has capacitance between terminals (coupling capacitance), the circuit in Figure 9 uses the PIN diode D as shown in Figure 11.
1 is replaced with a parallel connection of a high frequency resistor R8 and an inter-terminal capacitance C6.

Due to this inter-terminal capacitance C8, the phase rotation of the signal is θ. However, this value shows a change as shown in FIG. 12 in relation to the high frequency resistor R8. As is clear from the figure, even if R8 changes, θ. There is no problem if it is used within a range in which is substantially constant, but this does not provide a sufficient range of gain adjustment. This is also the reason why variable attenuators and amplifiers are connected in multiple stages as shown in FIG.

Furthermore, the number of stages is increased, and the variable range of R8 per - stage is θ
. It is conceivable to keep the value within a range where the value is substantially constant, but this would increase the circuit scale and go against the recent demand for miniaturization.

Therefore, the current situation is to set the variable range of RX to the right side of the value shown by the broken line in FIG. 12, allowing some change in the values around the phase. Therefore, when applied to the space diversity receiver shown in FIG. 7, when the level of the main signal or sub signal drops significantly, the mixer 52
The problem is that there is a difference in the values around the phase of the AGC 8 MP 60 and 62 in the signal supplied to the AGC 8 MP 60 and 62, and in-phase synthesis control is performed for such signals, which deviates from the conditions for perfect in-phase synthesis. was there.

Therefore, an object of the present invention is to provide an automatic gain control amplifier in which the overall phase value does not change even if the gain variable range is set within a range in which the phase value in the variable attenuator substantially changes. There is a particular thing.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention. In the figure, the automatic gain control amplifier of the present invention includes at least one stage of variable attenuation means 10 which attenuates an input signal at a variable attenuation ratio and outputs the resultant signal, and which is connected in series with the variable attenuation means 10 to amplify the input signal. at least one stage of amplifying means 12 for outputting, and level detecting means 14 for detecting the level of the final stage signal and outputting a signal corresponding to the detected level as a control signal for the attenuation ratio of the variable attenuation means 10. In the automatic gain control amplifier, a variable phase shifter is connected in series with the variable attenuation means 10 and the amplification means 12 and shifts the input signal by a phase shift amount according to the output signal of the level detection means 14. It is characterized by comprising means 20.

This automatic gain control amplifier has a polygonal line approximation means 2 which receives the output signal of the level detection means 14 as an input and generates a signal for controlling the variable phase shift means 20 by polygonal approximation.
2 is preferably provided.

[For production]

As described above, the attenuation ratio in the variable attenuation means 10, that is, the value of the control signal to the variable attenuation means 10 and the variable attenuation means 10
Since there is a certain relationship with the value around the phase of It can have a phase shift characteristic, and by doing so, the value around the overall phase can be kept constant regardless of the level of the input signal.

A phase shift characteristic that cancels out changes in values around the phase of the variable attenuation means 10 can be approximately obtained, for example, by polygonal line approximation.

〔Example〕

FIG. 2 shows an automatic gain control amplifier (AGCAM) according to the present invention.
It is a figure showing one example of P). Components labeled with the same reference numbers as in FIG. 8 (portions other than those surrounded by broken lines) exhibit the same effects as described above.

The variable phase shifter 200 shifts the phase of the input signal by a magnitude corresponding to the value of the control voltage and outputs it. Operational amplifier 2201 diodes D2, D3, and resistors R5 to R9 constitute a well-known polygonal line approximation circuit, and the relationship between input voltage and output voltage is defined by the number of paths including diodes (2 in the example shown) and each resistance value. The polygonal line is determined.

The output voltage of the amplifier 142, which is supplied as a control signal to each variable attenuator 100, is converted by this polygonal line approximation circuit and supplied to the variable phase shifter 200 as its control signal. Therefore, by appropriately designing the polygonal line determined in the polygonal line approximation circuit, the variable phase shifter 20 can create a phase shift characteristic that cancels out the change characteristics around the phase caused by each variable attenuator 100.
It can be set to 0.

FIG. 3 is a detailed circuit diagram of an example of the variable phase shifter 200 of FIG.

The control voltage is applied to the cathode side of the variable capacitance diode D4. Depending on the value of this control voltage, the junction capacitance of the variable capacitance diode D changes, and the amount of phase shift changes.

Figure 4 shows the junction capacitance C of the variable capacitance diode in the variable phase shifter shown in Figure 3 and the resulting value θ around the phase.
FIG. This characteristic and the phase rotation θ of the variable attenuator 100 explained in FIG.

The phase rotation θ due to the variable phase shifter 100 is obtained from the characteristics of . The phase rotation θ in the variable phase shifter 200 that cancels the change characteristics of . The change characteristic of is determined, and each constant of the polygonal line approximation circuit is determined to appropriately approximate it.

FIG. 5 shows the output level characteristics and phase characteristics of the automatic gain control amplifier thus designed as a function of the input level. - The dashed dotted line shows the output level characteristics, the thin solid line shows the phase characteristics in the conventional AGCAMP without the phase shifter 200, the broken line shows the phase characteristics of the phase shifter 200, and the thick solid line shows the present invention which combines both. AGCAM related to
The phase characteristics of P are shown.

As is clear from the figure, the AGCAMP according to the present invention exhibits a characteristic in which the values around the phase are substantially constant even in the entire range where the output level is controlled to be constant, especially in the region where the input level is small.

FIG. 6 is a diagram showing the configuration of a space diversity receiving apparatus incorporating the AGCAMP described in FIG. 2. It is the same as the conventional space diversity receiver shown in FIG. 7, except that AGCAMPs 60, 62 (FIG. 7) are replaced by AGCAMPs 64, 66 according to the present invention. In the circuit shown in FIG. 6, even when the level of either the main signal or the sub signal drops significantly, there is no difference in the amount of phase shift between the eight GCAMPs 64 and 66, and therefore the conditions for perfect in-phase synthesis are satisfied. can get.

[Effects of the Invention] As described above, according to the present invention, an automatic gain control amplifier whose phase characteristics are substantially constant within a control range is provided, and an infinite shift of a space diversity receiving device that performs in-phase combining is provided. When applied to a circuit for generating a control signal for a phase converter, excellent fading distortion removal can be achieved even in a wide range of reception levels, especially when the reception level is extremely low.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle configuration of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing the variable phase shifter 2 of FIG.
4 is a diagram showing the characteristics of the variable phase shifter 200, FIG. 5 is a diagram showing the characteristics of the AGCAMP of FIG. 2, and FIG. 6 is a diagram showing the characteristics of the AGCAMP of the present invention. FIG. 7 is a diagram showing the configuration of an example of a conventional space diversity receiving device; FIG. 8 is a detailed configuration of the AGCAMPs 60 and 62 shown in FIG. 7. 9 is a diagram showing the detailed configuration of the variable attenuator 100 shown in FIG. 8, FIG. 10 is a diagram showing the characteristics of the circuit shown in FIG. Equivalent circuit diagram of the circuit, Figure 12 is 9
FIG. 12 is a diagram showing the characteristics of the circuit shown in FIG. In the figure, 100...variable attenuator, 120, 1.42
...Amplifier, 140...Detector, 200.
... variable phase shifter, 220... operational amplifier. Detailed configuration of an example of the variable phase shifter 200 Fig. 3 - Input level (dB) Output level Fig. Phase 1 of conventional AGCAMP Phase rotation of phase shifter Synthesis phase rotation Fig. W''' . Ganjōkai)

Claims (1)

[Claims] 1. At least one stage of variable attenuation means (10) for attenuating an input signal at a variable attenuation ratio and outputting the resultant signal, and at least one stage of variable attenuation means (10) connected in series to the variable attenuation means (10) for amplifying the input signal. At least one stage of amplification means (12) for outputting, and a level for detecting the level of the signal at the final stage and outputting a signal corresponding to the detected level as a control signal for the attenuation ratio of the variable attenuation means (10). an automatic gain control amplifier comprising: a detection means (14) connected in series with the variable attenuation means (10) and the amplification means (12), a phase shift according to the output signal of the level detection means (14); variable phase shifting means (20) for shifting the input signal by an amount;
An automatic gain control amplifier comprising: 2. The apparatus according to claim 1, further comprising polygonal line approximation means (22) which receives the output signal of the level detection means (14) and generates a signal for controlling the variable phase shift means (20) by polygonal line approximation. Automatic gain control amplifier.