JPH0758930B2 - Automatic gain control amplifier - Google Patents

Description

DETAILED DESCRIPTION [Outline] Automatic gain control amplifier, in particular, to 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, a variable attenuation The purpose of the present invention is to provide an automatic gain control amplifier in which the value around the phase does not change even if the variable range of the gain is set to the range where the value around the phase of the converter changes substantially. At least one stage of variable attenuating means for attenuating and outputting at a damping ratio of at least one stage, at least one stage of amplifying means for amplifying and outputting an input signal connected in series to the variable attenuating means, and detecting the level of the final stage signal. An automatic gain control amplifier including level detection means for outputting a signal according to the level detected by the variable attenuation means as a control signal for the attenuation ratio of the variable attenuation means, Connected in series to the variable attenuation means and the amplification means configured by including a variable phase shifting means for phase shifting the input signal at the phase shift amount corresponding to the output signal of said level detecting 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 of a space diversity receiver.

[Conventional technology]

FIG. 7 is a diagram showing the configuration of a known space diversity receiver having an automatic gain control amplifier (AGC AMP). What is shown in the figure is a space diversity receiver using in-phase combining, and one of the main signal from the main antenna and the sub-signal from the sub-antenna installed at a different position from the main antenna is used so that both are in phase. By phase-shifting and synthesizing, interfering waves due to multipath are relatively attenuated and the effect of multipath fading is removed.

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 amplifier 506 and the infinite phase shifter (En
dless Phase Shifter: EPS), amplifier 510, hybrid
It is supplied to the Hybrid 514 via 512, and the Hybrid 51
In 4, the both are combined and output via the amplifier 516.

On the other hand, the main signal and the sub signal are respectively branched in the hybrid 502 and 512 to generate the control signal of EPS508,
Both are combined in mixer 520 through bandpass filters 504 and 518 and AGC AMPs 60 and 62, respectively. Mixer 520
The signal combined in (1) is input to the control circuit 502, and the output thereof controls the amount of phase shift in EPS 508. Here, if the levels of the main signal and the sub signal supplied to the mixer 520 are constant, the output of the mixer 520 becomes a signal corresponding to the phase shift difference between the two, and the amount of phase shift in the phase shifter 508 according to this signal. Are controlled and in-phase synthesis is achieved. Therefore, the AGC AMP60, 62 mixes signals of a constant level regardless of the level fluctuations of the main signal and sub-signal to satisfy this condition.
Supply to 520.

By the way, the AGC AMP used in this space diversity receiver is a variable attenuator 100 as shown in FIG.
Generally, a configuration in which a plurality of amplifiers and amplifiers 120 connected in series are connected in series is used. The level of the output of the amplifier 120 at the final stage is detected by the detector 140, and the amplifier 14
It is amplified by 2 and supplied as a control voltage to each variable attenuator 100, and as a result, the overall gain is automatically adjusted so that the level of the output signal of the final stage amplifier 120 is constant regardless of the level of the input signal. . As shown in FIG. 9, the variable attenuator 100 is configured by utilizing the characteristics of PIN diode. P
The IN diode has a property that the high frequency resistance R _X changes as shown in FIG. 10 according to the value i _O of the current flowing in the forward direction within the frequency range reaching the microwave band. Therefore, the voltage division ratio by the PIN diode D ₁ and the resistor R ₃ , that is, the attenuation amount A _V also changes as shown in FIG. 10 according to the change of i _O.

[Problems to be Solved by the Invention]

Since the diode has a capacitance between terminals (coupling capacitance), the circuit shown in FIG. 9 is obtained by replacing the PIN diode D ₁ with a parallel connection of the high frequency resistor R _X and the capacitance C _O between terminals as shown in FIG. Expressed equivalently.

The inter-terminal capacitance C _O causes a signal phase θ _O , but this value shows a change as shown in FIG. 12 in relation to the high frequency resistance R _X. As is clear from the figure, even if R _X changes, there is no problem if it is used within a range where θ _O is substantially constant.
Then, the gain adjustment range cannot be taken sufficiently. This is also why the variable attenuator and the amplifier are connected in multiple stages as shown in FIG.

Further increasing the number of stages, the variable range of R _X per stage is θ _O
It is conceivable that the value is substantially constant, but the circuit scale becomes large, which is against the recent demand for miniaturization.

Therefore, under the present circumstances, the variable range of R _X is set to the right of the value indicated by the broken line in FIG. 12 to allow a slight change in the value around the phase. Therefore, when applied to the space diversity receiver shown in FIG. 7, when the level of the main signal or the sub-signal is significantly reduced, the signal supplied to the mixer 520 has a difference in the values around the phase by the AGC AMPs 60 and 62. However, there is a problem in that the control of the in-phase synthesis of such a signal deviates from the condition of the complete in-phase synthesis.

Therefore, an object of the present invention is to provide an automatic gain control amplifier in which the total value around the phase does not change even if the variable range of the gain in the variable attenuator is set to a range where the value around the phase substantially changes. Especially.

[Means for Solving the Problems]

FIG. 1 is a principle diagram of the present invention. In the figure, the automatic gain control amplifier of the present invention comprises at least one stage of variable attenuating means 10 for attenuating an input signal with a variable attenuation ratio and outputting the attenuated input signal.
The variable attenuating means 10 is connected in series with at least one stage of amplifying means 12 for amplifying and outputting an input signal, and the level of the signal of the last stage is detected, and a signal corresponding to the detected level is output to output the variable signal. In an automatic gain control amplifier including a level detecting means 14 for controlling the attenuation ratio of the attenuating means 10, an output signal of the level detecting means 14 is connected in series to the variable attenuating means 10 and the amplifying means 12. It is characterized by comprising variable phase shift means 20 for shifting the phase of the input signal by a corresponding phase shift amount.

This automatic gain control amplifier receives the output signal of the level detection means 14 as an input, and uses the variable phase shift means by line approximation.
It is preferable to include a polygonal line approximation means 22 for generating a signal for controlling 20.

[Work]

As described above, since the damping ratio in the variable attenuating means 10, that is, the value of the control signal to the variable attenuating means 10 and the value around the phase by the variable attenuating means 10 have a constant relationship, the variable phase means 20 responds to this value. It is possible to provide a phase shift characteristic that cancels the change in the value around the phase of the variable attenuator 10 by shifting the signal with the phase shift amount, and by doing so, the value around the entire phase is input signal. It can be kept constant regardless of the level of.

The phase shift characteristic that cancels the change in the value around the phase of the variable damping means 10 can be approximately obtained by, for example, the polygonal line approximation.

〔Example〕

FIG. 2 is an automatic gain control amplifier (AGC AMP) according to the present invention.
It is a figure showing one Example. Components with the same reference numbers as in FIG. 8 (portions other than the portion enclosed by the broken line)
Has the same effect as described above.

The variable phase shifter 200 shifts the phase of the input signal according to the value of the control voltage and outputs it. Operational amplifier 220, diode D ₂ ,
D ₃ and resistors R _{5 to} R _{9 form} a well-known polygonal line approximation circuit, and a polygonal line that defines the relationship between the input voltage and the output voltage by the number of paths including the diode (2 in the example in the figure) and each resistance value is Determined.

Amplifier 142 supplied to each variable attenuator 100 as a control signal
The output voltage of is converted by this broken 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 200 can be provided with a phase characteristic that cancels the variation characteristic around the phase by each variable attenuator 100.

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 D ₄ . Depending on the value of this control voltage, the variable capacitance diode D ₄
The junction capacitance of changes, and the amount of phase shift changes.

FIG. 4 shows the junction capacitance C of the variable capacitance diode in the variable phase shifter shown in FIG.
FIG. 5 represents and as a function of control voltage. This characteristic and the phase around theta ₀ of change characteristic of the variable phase shifter 200 to cancel the change characteristics of the phase around theta ₀ and a characteristic of the phase around theta ₀ of the variable attenuator 100 according to the variable phase shifter 100 described in FIG. 12 Is determined, and each constant of the polygonal line approximation circuit is determined so as to appropriately approximate it.

FIG. 5 shows the output level characteristic and the phase characteristic of the automatic gain control amplifier thus designed as a function of the input level. The alternate long and short dash line shows the output level characteristic, the thin solid line shows the phase characteristic in the conventional AGC AMP without the phase shifter 200, the broken line shows the phase characteristic of the phase shifter 200, and the thick solid line shows the present invention in which both are combined. 3 shows the phase characteristics of the AGC AMP according to. As is clear from the figure, the AGC AMP according to the present invention exhibits the characteristic that the value around the phase becomes substantially constant even in the entire range in which the output level is controlled to be constant, particularly 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 AGC AMP described in FIG. AG
It is the same as the conventional space diversity receiver shown in FIG. 7 except that the C AMPs 60, 62 (FIG. 7) are replaced with the AGC AMPs 64, 66 according to the present invention. The circuit shown in Fig. 6 does not cause a difference in the amount of phase shift between AGC AMP64 and 66 even when the level of either the main signal or the sub signal is significantly reduced, and therefore, the condition for perfect in-phase synthesis can be obtained. To be

〔The invention's effect〕

As described above, according to the present invention, an automatic gain control amplifier whose phase characteristic is substantially constant in a control range is provided, and a control signal of an infinite phase shifter of a space diversity receiver that performs in-phase combining is provided. When applied to a circuit for generating, good fading distortion removal can be achieved even in a wide range of reception levels, particularly when reception levels are extremely low.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle configuration of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing a detailed configuration of an example of the variable phase shifter 200 of FIG. FIG. 4 is a diagram showing characteristics of the variable phase shifter 200, FIG. 5 is a diagram showing characteristics of the AGC AMP of FIG. 2, and FIG. 6 is an example in which the AGC AMP of the present invention is incorporated in a space diversity receiver. FIG. 7 is a diagram showing a configuration of an example of a conventional space diversity receiver, FIG. 8 is a diagram showing a detailed configuration of the AGC AMPs 60 and 62 of FIG. 7, and FIG. 9 is a variable of FIG. FIG. 10 is a diagram showing a detailed configuration of the attenuator 100, FIG. 10 is a diagram showing characteristics of the circuit of FIG. 9 with respect to the control current i _0, FIG. 11 is an equivalent circuit diagram of the circuit of FIG. 9, and FIG. High frequency resistance R _{X of the} circuit shown in FIGS. 9 and 11.
FIG. In the figure, 100 ... variable attenuator, 120, 142 ... amplifier, 140 ... detector, 200 ... variable phase shifter, 220 ... operational amplifier.

Claims (2)

[Claims] 1. At least one stage of variable attenuating means (10) for attenuating an input signal with a variable attenuation ratio and outputting the same, and at least one amplifier connected in series with the variable attenuating means (10) for amplifying and outputting the input signal. One-stage amplification means (12) and level detection means for detecting the level of the signal at the final stage and outputting a signal corresponding to the detected level to obtain a control signal for the attenuation ratio of the variable attenuation means (10) ( 14) in an automatic gain control amplifier, which is connected in series with the variable attenuating means (10) and the amplifying means (12) and has a phase shift amount according to an output signal of the level detecting means (14). An automatic gain control amplifier comprising variable phase shift means (20) for shifting the phase of an input signal. 2. A polygonal line approximation means (22) for receiving the output signal of the level detection means (14) and generating a signal for controlling the variable phase shift means (20) by polygonal line approximation. 1. The automatic gain control amplifier according to 1.