JP2001057513A - Agc circuit and method for its gain control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optimum gain for a desired wave even when an adjacent channel interference wave is inputted to a receiver by calculating the difference between the power of a signal to be inputted to a band-pass filter(BPF) and the power of its output signal and adding a correction value corresponding to the magnitude of this differential signal to the input of an integrator. SOLUTION: The power of an input signal of a BPF 3 is detected, the power of an output signal of the BPF 3 is also detected, power values calculated by the respective detections are inputted to an adder 8-3 to calculate the difference between the both, a controller 13 outputs a gain correction signal by this differential signal to be added to an integrator 9, and the control gain of an automatic gain control(AGC) circuit 4 is adjusted. According to this configuration, it is possible to obtain an optimum gain for a desired wave all the time even when an adjacent channel interference wave is inputted to a receiver because the control gain is corrected by calculating the difference between the input and output powers of the BPF 3 and adding a correction signal corresponding to this differential signal to the integrator 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an AGC (Auto Gain con
The present invention relates to a trol (automatic gain control) circuit, and more particularly to an improvement of an AGC circuit used in a receiving apparatus such as a digital mobile communication.

[0002]

2. Description of the Related Art In a digital mobile communication receiver using a linear modulation method such as multi-level QAM, in order to avoid a decrease in reception quality due to a reception power fluctuation due to a distance attenuation of reception power or fading, AGC (Auto Gain contr) that compensates for fluctuations in received power and automatically adjusts to a predetermined power value
ol: automatic gain control) circuit.

A conventional AGC circuit will be described with reference to FIG.
FIG. 2 is a block diagram showing a configuration of a feedback type AGC circuit used in a digital wireless receiver. 1
-1 and 1-2 are input terminals, 2 is an output terminal, 3-1 is a band limiting filter (BPF), 4 is a variable gain amplifier, 5 is a detector, 6-1 is A /
D converter, 7 is a power calculator, 8-1 is an adder, 9 is an integrator, 10
Is a D / A converter. In FIG. 2, an intermediate frequency reception signal (reception IF signal) received by an antenna and frequency-converted into an intermediate frequency band signal is input to a variable gain amplifier 4 via an input terminal 1-1. The variable gain amplifier 4 includes a D / A converter 10
The gain control signal input from the power of the input signal from the input terminal 1-1 is sent to BPF3 are gain adjusted to a predetermined reference value P _0. In BPF3, the signal of which the band of the interference signal other than the desired signal is band-limited from the input signal is
It is sent to 5 and detected. The signal detected by detector 5 is A / D
The signal is converted into a digital signal by the converter 6-1 and output from the output terminal 2 to, for example, a demodulation processing unit.

[0004] The output of the A / D converter 6-1 is supplied to a power calculator.
Also sent to 7. The power calculation unit 7 calculates the power value P ₁ of the input signal and outputs the negative (subtraction) input of the adder 8-1. On the other hand, the positive adder 8-1 (minuend) input via the input terminal 1-2, the reference value P ₀ of the input signal power is inputted. The adder 8-1 outputs an error signal (P ₀₎ obtained by subtracting the power value P ₁ of the input signal from the reference power value P ₀ of the input signal.
- Output P _1). This error signal is input to the integrator 9 and integrated, and then output to the D / A converter 10. The D / A converter 10 outputs a control signal to the variable gain amplifier 4 based on the output of the integrator 9, and sets the gain of the variable gain amplifier 4.

[0005] As described above, the feedback control of the variable gain amplifier 4 is performed so that the power of the input signal becomes constant even when the input signal of the receiver fluctuates.

However, as shown in FIG. 3A, in the above-described technique, the power P _S [dBm] of a target signal to be received (desired wave: center frequency f ₀ ) is compared with the power P _S [dBm] from an adjacent radio channel. Power P _{d of} jammer (adjacent channel jammer: center frequency f ₁ )
If [dBm] is larger than the receiver selectivity (attenuation amount L [dB] of BPF3 with respect to the adjacent channel interference wave), the output of the BPF3 becomes the desired power P _S and the interference wave as shown in FIG. the synthesis of _{- (L P e = P d} ) BPF3 suppression residual P _e for. FIG.
FIG. 3A is a spectrum diagram illustrating a case where adjacent channel interference waves are present in the input and output signals of the BPF3. FIG. 3A shows an input signal, and FIG. 3B shows an output signal. In AGC circuit gain control so as to coincide with the combined power _{P 2 (P 2 = P S} + P e) the reference value P ₀ acts. As a result, compared with the adjacent channel interference wave is not, since the amount corresponding gain of the variable gain amplifier 4 for desired signal power of the interference wave component P _e is decreased, A / D converter
The output of the 6-1 quantization noise for the desired wave is increased by P _e, S / N is lowered. As a result, reception characteristics such as a reception error rate characteristic deteriorate.

[0007]

The above-mentioned prior art includes the following:
If the power of the interfering wave from the adjacent radio channel is greater than the receiver selectivity compared to the power of the signal to be received, the component of the interfering wave component is compared to the case where there is no adjacent channel interfering wave. However, since the gain of the variable gain amplifier with respect to the desired signal power is reduced, the S / N is reduced. As a result, there is a disadvantage that the reception characteristics (for example, the reception error rate characteristics) deteriorate.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to provide an AGC which provides an optimum gain for a desired signal even when an adjacent channel interference signal having a greater selectivity than the receiver is input to the receiver. It is to provide a circuit.

[0009]

In order to achieve the above object, an AGC circuit according to the present invention obtains a difference in power between a signal input to a BPF and an output signal of the AGC circuit, and determines the magnitude of the difference signal. By adding the corresponding correction value to the input of the integrator, even if an adjacent channel interference wave larger than the receiver's selectivity is input to the receiver, the AGC that gives the optimum gain to the desired wave A circuit is realized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the AGC circuit of the present invention. Components having the same functions as those in FIG. 2 are denoted by the same reference numerals. In addition, 11 is a power detector, 6-2 is an A / D converter,
12-1 and 12-2 are amplifiers, 8-2 and 8-3 are adders, and 13 is a control device. In FIG. 1, a reception IF signal is input from an input terminal 1-1 and sent to a variable gain amplifier 4. The variable gain amplifier 4 is amplified and output with a gain set by the output signal of the D / A converter 10 and sent to the BPF 3 and the power detector 11. The operation from the BPF 3 to the output terminal 2 is as described in FIG. The output of the A / D converter 6-1 is also sent to a power calculating unit 7, a negative input (minuend of the adder 8-1 by calculating the power value P ₁ of the signal inputted in the power calculation section 7 Input side) terminal and send to amplifier 12-2. On the other hand, adder 8-1
Positively (minuend) input via the input terminal 1-2, the reference value P ₀ of the input signal power is inputted. In the adder 8-1,
From the reference power value P ₀ of the input signal, and outputs an error signal obtained by subtracting the power value P ₁ of the input signal. This error signal is sent to the adder 8-2, added to the output signal of the control device 13, and then input to the integrator 9 for integration, and then the D / A converter 10
The integration result is output to. The D / A converter 10 supplies a voltage based on the input signal as a control voltage for the variable gain amplifier 4.

On the other hand, for example, RSSI (Received Signal Stre
ngth Indicator) A voltage proportional to the power value (unit: dBm) of the input signal, such as a circuit (hereinafter referred to as RSSI voltage)
The power detector 11 that outputs
Output SI voltage. The signal having the RSSI voltage is input to the A / D converter 6-2, where the signal is converted into digital data, amplified by K ₁ times by the amplifier 12-1 (power value: P ₂ ), Three
To the positive input (subtracted input side) terminal. On the other hand, the output power signal (power value: P ₁ ) of the power calculation unit 7 is K
_It is amplified by a factor of ₂ (power value: P ₃ ) and input to the negative input (subtraction input) terminal of the adder 6-2. Note that the coefficient K ₁ and K ₂ are adders
8-3 is a correction coefficient for calibrating a gain difference between two power signals input to 8-3 (a difference in conversion gain for each path). The adder 8-3 calculates the difference ΔP between the two input signals (ΔP = P ₂
-Calculate and output P ₃ ) and send it to the controller 13. The control device 13 outputs a correction value ΔG for the gain of the AGC circuit according to the input difference signal ΔP and sends it to the adder 8-2. Adder 8-
2 is sent from the adder 8-1 come error signal (P ₀ - P ₁₎
And the correction value ΔG is sent to the integrator.

Here, the operation of the control device 13 will be described with reference to FIG. FIG. 4 shows the relationship (referred to as ΔP characteristic) between the interference wave power ratio [dB] (horizontal axis) and the power difference ΔP [dB] (vertical axis) based on the desired signal power. FIG. 4 shows that the selectivity of the BPF3 for the adjacent channel is L = 45 [dB].
This is an example of the case. Also, the asymptote (slope in FIG. 4)
= 1) and the difference ΔG between the ΔP characteristic and the ΔP characteristic indicate the shortage of the gain of the AGC circuit with respect to the desired wave when the interference wave is input. For example, when the interference power ratio is 45 [dB], the power difference ΔP = 42
At this time, the control gain of the AGC circuit for the desired wave is insufficient by ΔG = 3 [dB]. The control device 13 stores information (or an arithmetic expression) of the gain correction value ΔG for ΔP in advance, and uses the input difference signal ΔP as an argument,
The ΔG value (or a value corresponding to ΔG) is output to the integrator 9
To correct the control gain.

[0013]

As described above, according to the present invention, the difference between the input power and the output power of the band limiting filter is obtained, and a correction signal corresponding to the difference signal is added to the integrator to correct the control gain. With this configuration, it is possible to realize an AGC circuit that can always provide an optimum gain to a desired wave even when an interference wave is input to the receiver.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an AGC circuit according to the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional AGC circuit.

FIG. 3 is an explanatory diagram showing an input and output spectrum of a band limiting filter when there is an adjacent channel interference wave.

FIG. 4 is an explanatory diagram showing an example of control characteristics of the control device of the AGC circuit according to the present invention.

[Explanation of symbols]

1-1, 1-2: input terminal, 2: output terminal, 3-1: band limiting filter (BPF), 4: variable gain amplifier, 5: detector, 6-1, 6-2: A / D conversion , 7: Power calculation section, 8-1, 8
-2, 8-3: adder, 9: integrator, 10: D / A converter, 1
1: Power detector, 12-1, 12-2: Amplifier, 13: Control device,

Continued on the front page F term (reference) 5J100 AA02 AA15 AA22 BA01 BB01 BC05 CA01 CA23 CA28 CA29 CA31 CA32 DA06 FA02 JA01 JA02 JA05 KA05 LA03 LA06 LA09 LA11 QA01 QA03 SA02 5K052 AA01 AA14 BB02 CC00 DD04 EE04 EE19 GG04 GG04 CC25 CC52 JJ24

Claims (5)

[Claims] 1. A variable gain amplifier, comprising: a variable gain amplifier that amplifies a received signal by performing gain control with a gain control signal, wherein a difference between a feedback signal power and a predetermined reference power is used as the gain control signal. Controlling AGC
(Auto Gain Control) circuit, a band limiting filter for removing an interfering wave from the amplified signal, and a power difference between a signal input to the band limiting filter and the feedback signal power is obtained. An AGC circuit, comprising: a correction unit that adds a correction value corresponding to the magnitude of the gain control signal to an input of an integrator, wherein the correction unit corrects the gain control signal. 2. A variable gain amplifier for amplifying a received signal by gain control with a gain control signal, a band limiting filter for band limiting to remove an interference wave from the amplified signal, and a band limiting filter for filtering the band limited signal. A detector for detecting, an A / D converter for converting the detected signal into digital data, and power calculating means for converting the digital data into an output signal of an AGC (Auto Gain Control) circuit and calculating a power value thereof An adder that compares the calculated power with a predetermined reference power and outputs an error signal; an integrator that integrates the error signal; and a D that converts the signal output by the integrator into an analog signal. / A converter, and controls the gain of the received signal by controlling the gain of the variable gain amplifier using the analog signal as the gain control signal.
In the AGC circuit, a power detection unit that calculates a power value of a signal input to the band-limiting filter, a power value of a signal input to the band-limiting filter detected by the power detection unit, and a power value calculated by the power calculation unit. And a correction value for outputting a correction value for correcting the error signal output by the adder from the difference value of the power obtained by the difference value calculation means. Output means, and a correction value output by the correction value output means.
An AGC circuit comprising: a correction unit that corrects the value of the error signal, wherein the gain of the received signal is controlled by controlling the gain of the variable gain amplifier based on the error signal corrected by the correction unit. 3. The AGC circuit according to claim 1, wherein said power detection means performs power detection by inputting a signal to be input to said band limiting filter, and outputs a digital data by said power detector. Convert to the second
An A / D converter, wherein the difference value calculating means is an adder for calculating a difference between the digital data output by the second A / D converter and a power value calculated by the power calculating means. An AGC circuit characterized by the following. 4. The AGC circuit according to claim 1, wherein said correction value output means is difference information between input power and output power of said band-limiting filter, and said correction value output means outputs said AGC circuit. Control information for correcting the gain of
The correction value output means stores in advance a gain correction value corresponding to the difference information or an arithmetic expression for calculating the gain correction value, and outputs the stored or calculated gain correction value based on the input difference information. AGC circuit wherein the gain of the AGC circuit is corrected by adding 5. A received signal is amplified, a band is limited to remove an interference wave from the amplified signal, the band-limited signal is detected, the detected signal is converted into digital data, and the converted signal is converted. AGC (Auto Gain Con
trol) as an output signal of the circuit and calculating a power value thereof, comparing the calculated power with a predetermined reference power, outputting an error signal, integrating the error signal, and converting the integrated signal into an analog signal. AG that performs conversion and controls the gain of the received signal using the converted analog signal as the gain control signal.
In the C circuit control method, a power value of the signal before the band limitation is obtained, and a difference value between a power value of the signal before the band limitation and a power value of an output signal of the AGC circuit is obtained. AGC circuit gain control method comprising: outputting a correction value for correcting the error signal from the output signal; correcting the value of the error signal with the correction value; and controlling the gain of the reception signal with the corrected error signal. .