JPS61242406A - Agc system - Google Patents

Abstract

PURPOSE:To eliminate the influence of external noises, temperature variation, etc., and to easily set a gain by comparing control contents which correspond to a detection output and characteristics of a detecting circuit with the storage contents stored in a ROM and calculating a control voltage. CONSTITUTION:A sample and hold circuit 10 holds a level with a clock for reception synchronization in synchronism with the clock. An adder 12 is an adder which adds the output of an A/D converter 11 and adds (i) samples (i: positive integer) and a subtracter 13 performs subtraction. This function is equivalent to the calculation of the mean value of the (i) samples and determines the time constant of an AGC loop. Then, the ROM 14 compares and output e0 with a detected voltage corresponding to the mean output. The ROM 14 is stored with respective values to be read out corresponding to inputs according to detection voltage characteristics of a detector 3. An adder 15 adds the ROM output to a constant voltage input VG and a 1dB (m)-bit digital attenuator 17 is controlled with the addition output.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides an A
Concerning improvements in GC circuits.

[Conventional technology]

Generally, in a repeater, the received electric field often changes over time, so an AGC method is used to keep the output constant regardless of changes in the received electric field. FIG. 6 shows an AGC circuit within a transmitting/receiving device in a conventional repeater. 1 is a variable attenuator, 2 is an amplifier, 3 is a detector, 4 is a low-pass filter (
below.

5 is a reference voltage generator, and 6 is an AGO amplifier.

The AGC operation will be explained below using the circuit shown in FIG. In FIG. 7, the variable attenuator 1 of FIG. 6 is replaced by a multiplier 7.
The AGC amplifier 6 in FIG. 6 can be considered to be composed of a comparator 8 and an amplifier 9. Here, the output e0
is detected and then input to the comparator 8 via the LPF i,
It is compared with a reference voltage E. Furthermore, the differential voltage is applied to the amplifier 9
is amplified and fed back to the input. The relational expression at this time is given by the following expression.

G-HH elQ = □ E+ □ ei(1)G
+HG+H Here, the gain of the GUAGC amplifier 9.

H is the gain of amplifier 2.

Therefore, the output e regardless of the change in the input ei. In order to keep it constant.

G>)l. At this time, e(1*E), the output e becomes constant.

FIG. 8 shows input J-output e. Show characteristics.

[Problem that the invention seeks to solve]

In a conventional AGC amplifier, the output level characteristics relative to the input level are determined by a control voltage of a pin diode or the like that constitutes a variable resistor. However, since the detection voltage characteristic for obtaining this control voltage is non-linear, (1) it is difficult to set an arbitrary gain, and (2) it is easily affected by temperature fluctuations.

■It had the disadvantage of being weak against external noise.

Furthermore, since the gain of the AGC amplifier in equation (1) above has a limit, it becomes e(1'yE, which causes the problem that the output is not completely constant and varies slightly in response to changes in the input. was there.

The present invention seeks to eliminate the above drawbacks.

It is an object of the present invention to provide an AGC method that has stable gain settings, can set the gain arbitrarily, and is resistant to temperature fluctuations and external noise.

[Failure to solve the problem]

The present invention includes a circuit that detects a received signal, a circuit that samples and holds the detection output, and means for A/D converting the output t of the sample and hold circuit.

#Equipped with means for averaging the A/D conversion output for a certain period corresponding to a predetermined AGC time constant, and means for comparing and calculating the averaged output with the memory content stored in the ROM in advance, An AGC method that maintains the output constant regardless of fluctuations in the reception input by controlling a variable attenuation gain inserted in the reception circuit using the calculation output,
The present invention is characterized in that control contents corresponding to the characteristics of the detection circuit are written in the ROM.

〔Example〕

FIG. 1 shows an AGC circuit in a transmitter/receiver according to the present invention, which is constructed digitally.

In the figure, 10 is a sample and hold circuit.

It has a function of holding the level in synchronization with the clock using the clock for synchronizing transmission and reception.

11 is an ADD converter. 12 is an adder that adds the output of the A/D converter 11, and has l samples (i is a positive integer).
Then, the divider 13 performs division. This function is equivalent to taking the average of l samples, and AG
Determine the time constant of C loop t6゜(”j; f(i))
Next, a comparison is made with the detected voltage in the LIC and ROM 14 corresponding to the average output of the oi-feo.

FIG. 2 shows the detected voltage characteristics of the detector 3. As shown in Figure 2, when the output e0 is OdBm, the detection voltage is 1v, +
At 1dBm 1. IV, at -1dBm.

The characteristic is assumed to be 0.9v.

On the other hand, as shown in Fig. 3, the ROM 14 has a value of 0.0 when the ROM human power is 1V. Input 1. The various positions to be read out corresponding to the inputs are stored so that results such as +1 dB at IV17), -1 dB at input 0.9V, etc. are obtained.

The adder 15 adds the ROM output and the constant voltage input VG, and controls the m-bit digital attenuator 17 in 1 dB steps with the added output. Therefore.

When the input is J and the ROM power is 1V, the output of the adder 15 is V
C, V when the input is ei + 1 dB and ROM input + 1.1 V
C+ 1, input is ei-1dB and ROM input 0.9V
When VC-1d B and output e. is always kept constant. However, the output e. =1~1. IV, 0.9~1v
Since the variable attenuator 17 is constant in the section..., the output is e. changes in proportion to the input ei. When the dynamic range of the variable attenuator 17 is set to gold LdB, if the input ei decreases and the variable attenuator 17 becomes all OdB, the output e0 decreases in proportion to the input e, and conversely the input 81 increases. If the variable attenuator 17 becomes LdB, there is no increase in the variable attenuator 17, so the output e0 increases in proportion to the input ei. In this way, the AGC characteristic becomes constant within a range of +1 dB in the dynamic range L dB section, as shown in FIG.

Note that 16 is a mar-al/auto selector switch,
The AGC loop is disconnected if necessary, and the gain can be set manually.

Because of this circuit structure, the single-wire digital AGC system is less susceptible to external noise, temperature fluctuations, etc., and has the advantage of being easy to set gain.

In addition, in FIG. 1, the set value VG f added to the adder 15
It is clear that the operating point can be easily changed by changing. Furthermore, by changing the contents written in the ROM 14, the set point of the constant output can be changed. That is, the fifth
As shown in the figure.

Specify the address by setting the stored contents of the ROM 14 as the content that makes the output OdBm constant for address 0 and the output +10 dBm constant for address 1 based on the detection characteristic data in Figure 2. You can set the output as you like.

〔Effect of the invention〕

As explained above, according to the present invention, there is no influence from external noise, temperature fluctuations, etc.

An AGC method with easy gain setting is provided. Moreover,
Since the AGC circuit is entirely composed of digital circuits,
It also has the effect of being able to be made smaller and lighter by using ICs and the like.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the AGC circuit according to the present invention, FIG. 2 shows the detection characteristics of the detector shown in FIG. 1, and FIG. 3 shows the detection characteristics of the detector shown in FIG.
An example of the storage contents of the ROM shown in the figure is shown, FIG. 4 shows the AGC characteristics according to the embodiment of FIG. 1, and FIG. 5 shows the contents of the ROM when changing the setting output as a modification of the present invention.
FIG. 6 is a diagram showing the conventional AGC system, FIG. 7 is its equivalent circuit diagram, and FIG. 8 is its human power-output characteristic diagram. 1 is a variable attenuator, 2 is an amplifier, and 3 is a detector. 4 is a low-pass filter, 5 is a reference voltage generator, 6 is an AGC amplifier, 7 and 8 are adders, 9 is an amplifier, 10 is a sample and hold circuit, 11 is an A/D converter, 12 is an adder,
13 is a divider, 14 is a ROM, and 15 is an adder. 16 is a manual/auto selector switch, and 17 is a variable attenuator. Figure 2 Address Contents Figure 3 Figure 5 Figure 8

Claims (1)

[Claims] 1. A circuit for detecting a received signal, a circuit for sampling and holding the detection output, a means for A/D converting the output of the sample and holding circuit, and a means for converting the A/D conversion output into a predetermined AGC time constant. A variable attenuator is provided with means for averaging over a corresponding fixed period, and means for performing a comparison operation between the averaged output and memory contents stored in a ROM in advance, and is inserted into a receiving circuit according to the operation output. An AGC method that maintains an output constant regardless of fluctuations in received input by controlling the detection circuit, the AGC method being characterized in that control contents according to characteristics of the detection circuit are written in the ROM.