JP2000209052A - Digital agc device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the distribution of gains that is optimum to plural AGC amplifiers while keeping the total gain of a digital AGC device. SOLUTION: This digital AGC device outputs digitally the received signals through the AGC amplifiers 6 and 16 and is provided with an amplitude judging means 263 which judges the digital output amplitude, a gain distribution means 268 which distributes the general gains obtained based on the amplitude judged by the means 263 to the amplifiers 6 and 16 with the higher priority given to the amplifier of the preceding stage and D/A converters 265a and 265b which feed back the amplitude signals of gains distributed by the means 268 to the corresponding AGC amplifiers after the D/A conversion of the amplitude signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital A for digitally outputting a received signal through a plurality of AGC amplifiers.
It relates to a GC device.

[0002]

2. Description of the Related Art Generally, the amplitude of a radio signal coming into a radio receiver fluctuates greatly due to fading, multipath, and the like. However, in the receiver, the signals need to be adjusted to an almost constant level in terms of signal processing, and an AGC device (automatic gain adjusting device) for automatically performing the amplitude is generally added. . In this AGC apparatus, for example, in a conventional analog TV signal processing circuit, processing such as detecting a video signal amplitude and the like and feeding back a gain signal to the AGC apparatus is performed.

Further, in order to expand a signal input range for obtaining a constant level output despite the level fluctuation of an input signal, a first AGC amplifier for a major loop and a second AGC amplifier for a minor loop are provided. 2. Description of the Related Art There is known an automatic control device that forms a double feedback loop of a major loop and a minor loop. As a result, the entire gain range can be expanded, and a signal having a wider dynamic range can be received.

[0004] In recent years, development has been actively pursued to enhance services such as digitizing broadcast radio signals and expanding to high sound quality, high image quality, multiple channels, and data broadcasting. In order to receive such a signal, digital signal processing different from conventional analog signal processing is required. Generally, the above-mentioned AGC device digitizes an IF signal with an A / D converter, digitally discriminates the digital signal, and detects whether or not the input amplitude of the A / D converter is optimum. The resulting data is converted to an analog signal via a D / A converter, fed back to the AGC amplifier as a gain control signal, and automatically controls the gain.

FIG. 1 is a block diagram of a general digital signal receiving apparatus for receiving broadcast waves or the like. The broadcast wave received by the antenna 2 is passed through an RF band pass filter (BPF) 4 to remove noise outside the desired band, and is amplified by an RF amplifier 6. The amplifier 6 is an AGC amplifier that absorbs fluctuations of an input signal and outputs a signal of a constant amplitude in order to ensure signal processing in a subsequent stage. The output signal of the RF amplifier 6 is a mixer (MIX) 1 having a local oscillator (OSC) 8.
0 to the intermediate frequency (IF), IF BPF1
2, and is amplified by the IF amplifier 14. IF amplifier 1
4 is further subjected to AGC by the second AGC amplifier 16.
The processed mixer (MIX) 20 having a local oscillator (OSC) 18, a BPF 22, a second IF amplifier 24,
Then, the signal is output to a demodulation circuit (not shown) through the processing circuit 26. In the processing circuit 26, generally, an input signal is digitized by an A / D converter, and an amplitude judging unit monitors whether or not the amplitude of the input signal is optimal. ) 28 to change the gain, and through the low-pass filter (LPF) 30, the first AG
The signal is fed back to the C amplifier 6, where a first AGC feedback loop is formed.

In the above example, the AGC feedback loop is a single system. However, when the two-stage AGC amplifiers 6 and 16 are provided as shown in FIG. As described above, the second gain control signal is generated for the digital data from the processing circuit 26 and fed back to the second AGC amplifier 16, where a second AGC feedback loop is formed.
In this case, the first feedback loop is a major feedback loop, and the second feedback loop is a minor feedback loop.

FIG. 2 shows an input waveform and an output waveform of the AGC amplifier 6 in the receiving apparatus of FIG. The incoming radio wave to the antenna 2 may cause fading due to the reflection of the ionosphere or the like, or may cause multipath due to the reflection of an airplane, a building, or the like, and the amplitude may fluctuate sharply as shown in the input signal of FIG. Since the internal circuit of the receiving device requires a constant amplitude and an amplitude level within a certain range, such as the mixers 10 and 20, a feedback loop as shown in FIG. 1 is formed and an output waveform is shown in FIG. Thus, the signal is output as a signal having a substantially constant amplitude.

FIG. 3 shows the input / output characteristics of the AGC amplifier 6. If the input voltage Vi is within a certain range Vm, the output voltage is kept almost constant. However, the input voltage V
In the range Vs where i is too low or the range Vh where i is too high, the amplitude of the output voltage changes considerably. If this becomes a problem, as shown in FIG.
6 to provide a two-stage configuration. By doing so, as shown by the dashed line in FIG. 4, the input voltage range Vm in which a constant output can be obtained at the same time as the gain itself increases, and a wider dynamic range can be obtained.

FIG. 5 is a block diagram showing a general internal configuration of the processing circuit 26 of FIG. The IF signal from the second IF amplifier 24 is digitized by the A / D converter 261. Reference amplitude ROM 26 for storing optimal amplitude data
2 are provided, and the amplitude determination unit (ADC) 263
The digital data input from the / D converter 261 is compared with the reference data stored in the reference amplitude ROM 262, and the gain data of the desired AGC amplifier is output. Output to The gain output data of ADC 263 is D /
The signal is converted into an analog signal by the A converter 264 and passes through a low-pass filter (LPF) 265 in order to give the control signal a certain time constant. The output signal of the LPF 265 becomes a final control signal through the buffer amplifier 266, and is fed back to the AGC amplifiers 6, 16 as a feedback signal for gain control.

Here, as described above, when the AGC amplifier has two stages, only the amplitude determination section 263 is provided after the A / D converter 261 in the amplitude detection portion as shown in FIG.

[0011]

As described above, an AGC amplifier is provided in two stages for expanding the gain range, and a digital signal is received as described above. Here, in the case of analog signal processing, the output amplitude is extracted from the video detection output or the like, and the second AGC feedback loop, that is, the minor loop can be easily configured. This loop can be a different system from the first AGC loop, ie, the major loop. However, in the case of digital processing, there is usually only one IF signal amplitude output, so that the amplitude can be detected only at one location. Therefore, it is necessary to perform gain distribution for two AGC amplifiers with one detection point. Further, as long as the gain control is performed by a digital signal, all of the gain distribution must be digitally processed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a digital AGC apparatus which can achieve a predetermined overall gain with optimal gain distribution for a plurality of AGC amplifiers.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a digital AGC apparatus for digitally outputting a received signal through a plurality of AGC amplifiers. The amplitude signal of the total gain obtained based on the amplitude determined by the amplitude determination means is supplied to each AGC amplifier by the preceding AG.
Gain distribution means for preferentially distributing the C amplifier, and D / A for D / A converting the gain distributed by the gain distribution means and feeding back the gain to the corresponding AGC amplifier
And a converter.

The gain distributing means stores intermediate gain storing means for storing a shared boundary point of the shared gain of each AGC amplifier with respect to the total gain, and gain data of each AGC amplifier for the total gain of each AGC amplifier. Comparing the preset storage means with the stored contents of the total gain and the intermediate gain storage means, and issuing a comparison output when the total gain reaches a value equal to or greater than the stored contents of the intermediate gain storage means; A data selector for selecting the gain of each AGC amplifier based on the stored contents of the preset storage means and the comparison output of the comparison means can be provided.

[0015]

FIG. 6 shows gain data versus gain characteristics of a first AGC amplifier 6 and a second AGC amplifier 16. The product G1 * G2 = G of the gain G1 of the first AGC amplifier 6 and the gain G2 of the second AGC amplifier 16
The total gain data (output signal of the amplitude determination unit 263) of the entire system represented as t is from 0 to 2 ＾ (m + n), and 0 to 2 ＾ m in this range is set to the first AGC amplifier 6.
ゲ イ ン (m + 1) to 2 ＾ (m +
n) is distributed to the gain input range of the second AGC amplifier 16. m and n are both integers greater than 1. Here, m = n may be satisfied, or m = n may not be satisfied. The gain G1 of the first AGC amplifier 6 ranges from 1 to Gm, and the gain G2 of the second AGC amplifier 16 ranges from 1 to Gn. As shown in FIG. 6, the total gain range is expanded by the two-stage AGC amplifiers 6 and 16, and the first A
The gain range of the GC amplifier 6 is indicated by a solid line, and the gain range of the second AGC amplifier 16 is indicated by a broken line. The left vertical axis represents the overall gain of the entire system and the gain of the first AGC amplifier 6, and the right vertical axis represents the gain of the second AGC amplifier 16. In principle, in order to maximize the S / N ratio, it is preferable that the gain is preferentially distributed to the preceding AGC amplifier, that is, the gain of the preceding AGC amplifier 6 is increased.
It is more advantageous to make the gain as large as possible,
Gain G1 of first AGC amplifier 6 and second AGC amplifier 1
It is preferable to perform control so that the relationship of G1> G2 is satisfied between the gains G2 of 6.

In this case, if the input signal is 0 to 2 .mu.m in FIG.
When the amplitude D1 is within the range, the first AGC amplifier 6
Is set to the gain G1 corresponding to the amplitude D1 on the characteristic line, and the gain of the second AGC amplifier 16 is set to 1. When the input signal has an amplitude D2 within the range of 2 ＾ (m + 1) 〜2 ＾ (m + n) in FIG.
1 is set to Gm, and the gain of the second AGC amplifier 16 is set to a gain G2 / Gm corresponding to the amplitude D2 on the characteristic line. The processing of the input data for obtaining this gain can be easily calculated by (G2 / Gm) * (2 ＾ n / Gn). Here, since all except G2 are constants, K = (1 / Gm) * (2 (N / Gn) can be calculated in advance, and the calculation can be simplified as G2 * K.

By selecting appropriate parameters,
K can be a power of two, which makes it possible to configure the hardware described below with a very simple shift operation circuit or ROM table.

FIG. 7 shows a block diagram of the gain distribution device. The output data of the amplitude determiner (ADC) 263 is distributed to the respective gain control signals by the gain distribution device 268, and converted into analog signals by the D / A converters 265a and 265b, respectively, and further the low-pass filter (LP)
F) The gains G1, G2 of the respective AGC amplifiers 6, 16 are controlled through 266a, 266b.

FIG. 8 shows the internal configuration of the gain distribution device 268 of FIG. The value of 2Δm = Dm in FIG. 6, that is, the boundary gain Gm sharing the gain of the first AGC amplifier 6 and the second AGC amplifier 16, that is, 1A
Data 2 m corresponding to the maximum gain Gm of the GC amplifier 6
Gain storage ROM 41 and ADC 2
A gain comparator 42 for comparing the gain data input from 63 with the data in the ROM 41; a data selector 43 for selecting data for each of the AGC amplifiers 6 and 16;
44 are provided respectively. Data selector 43,
44, the gain data from the ADC 263 and the comparison result of the gain comparator 42 are input. Each of the data selectors 43 and 44 has ROMs 45 and 46 for storing preset values for generating prescribed value gain data. The ROM 45 stores a preset value Gm for the first AGC amplifier 6, and the ROM 46 stores a preset value "1" for the second AGC amplifier 16. Data selector 4
A ROM 47 for storing the above-mentioned constant K and a calculator 48 for calculating the gain data for the second AGC amplifier 16 as described above are provided at the subsequent stage of 4.

In the circuit device shown in FIG. 8, the input gain data is compared with the stored data value Dm of the ROM 41 by the gain comparator 42, and the gain comparator 42 includes only the first AGC amplifier 6 or two AGC amplifiers 6, 16 Is sent to the two data selectors 43 and 44.
The input gain data is D1 in FIG. 6 (where 0 ≦ D1 ≦ D
m), a signal to be dealt with only by the first AGC amplifier 6 is output. The data selector 43 outputs the data input by the signal as it is as a gain signal of the first AGC amplifier 6. On the other hand, the data selector 44
In this case, the gain of the second AGC amplifier 16 is set to "1" because only the first AGC amplifier 6 handles this case. Therefore, in order to output data corresponding to the gain, the data "1" is read from the ROM 46 in which the data is stored in advance, and is output as a gain signal of the second AGC amplifier 16.

If the input gain data is such as D2 in FIG. 6 (where Dm ≦ D2 ≦ 2 ＾ (m + n)), the gain comparator 42 includes the first AGC amplifier 6 and the second AGC amplifier. Signals to be dealt with by both 16 are issued. Upon receiving the signal, the data selector 43 reads out the data of the maximum gain Gm from the ROM 45 in which the data is stored in advance and outputs the data as the gain signal for the first AGC amplifier 6 in order to output the data corresponding to the maximum gain Gm. I do. On the other hand, the data selector 44 uses the two AGC amplifiers 6 and 16 so that the second
The gain of the AGC amplifier 16 is set to G2 / Gm as described above. The calculation for this is performed by the calculator 48. The data selector 44 sends the input data (D2) as it is to the arithmetic unit 48 in order to output the data for the arithmetic unit 48.

The arithmetic unit 48 here has a constant K (= (1 /
Gm) * (2 ＾ n / Gn))
47 and the data D2 from the data selector 44.
And outputs the result as a gain signal of the second AGC amplifier 16. In this case, a multiplier is necessary, but if the parameters are appropriately selected as described above, the value of the constant K can be set to a power of 2, and the multiplier can be replaced with a simple shift calculator. In addition, the hardware configuration can be greatly simplified. Further, the arithmetic unit 48 may be replaced with a large ROM table more directly so that the gain data can be directly output from the input data.

Although a two-stage AGC amplifier has been considered above, a similar gain distribution device can be constructed even with a multistage AGC amplifier.

[0024]

According to the present invention described above, the dynamic range is expanded as compared with the case where one AGC amplifier is used.
Optimal gain distribution by digital processing can be made possible under multistage AGC amplifiers of stages or more. In that case, for each set bit number of the total gain,
The number of bits of the D / A converter of the GC amplifier is arbitrary, and both need not necessarily be the same. Therefore, the degree of freedom of design is expanded.

According to the gain distribution method of the present invention, the gain of the preceding AGC amplifier can be maximized, and the S / N ratio of the entire apparatus can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a conventional digital wave receiving device.

FIG. 2 is a diagram showing input / output waveforms of a first AGC amplifier in the device of FIG.

FIG. 3 is a diagram showing input / output characteristics of a first AGC amplifier in the device of FIG. 1;

FIG. 4 is a diagram showing input / output characteristics when a plurality of AGC amplifiers are provided.

FIG. 5 is a block diagram illustrating an internal configuration of a processing circuit in the apparatus of FIG. 1;

FIG. 6 is an explanatory diagram for explaining an AGC gain distribution characteristic of the present invention.

FIG. 7 is a block diagram of a processing circuit in the digital AGC device of the present invention.

8 is a block diagram showing an internal configuration of an AGC gain distribution device in the processing circuit of FIG. 7;

[Description of Signs] 2 Antenna 4 RF Band Pass Filter (BPF) 6 First AGC Amplifier 10 Mixer 14 First IF Amplifier 16 Second AGC Amplifier 20 Mixer 22 Band Pass Filter (BPF) 24 Second IF Amplifier 26 Processing Circuit 261 A / D converter 262 ROM (storage means) 263 Amplitude judgment device (amplitude judgment means) 265a, 265b D / A converter 266a, 266b Low-pass filter (LPF) 268 Gain distribution device (gain distribution means) 41, 45, 46, 47 ROM ( Storage means) 42 gain comparator (gain comparing means) 43, 44 data selector 48 arithmetic unit

Claims (2)

[Claims] 1. A digital AGC device for digitally outputting a received signal through a plurality of AGC amplifiers, an amplitude determining means for determining the amplitude of the digital output, and a total gain of an amplitude determined based on the amplitude determined by the amplitude determining means. Amplitude signal to each AGC amplifier
Gain distribution means for preferentially distributing the signal to the amplifier;
A digital AGC device comprising: a D / A converter that performs / A conversion and feeds back to a corresponding AGC amplifier. 2. A digital AGC apparatus according to claim 1, wherein said gain distribution means includes: a boundary gain storage means for storing a shared boundary point for a total gain of a shared gain of each AGC amplifier; The preset storage means storing the gain data of each AGC amplifier with respect to the total gain is compared with the storage contents of the total gain and the boundary gain storage means, and the total gain is equal to or more than the storage contents of the boundary gain storage means. A comparison means for issuing a comparison output when the value of
A digital AGC device comprising: a data selector for selecting a gain of each AGC amplifier based on the storage contents of the preset storage means and a comparison output of the comparison means.