JP3252592B2 - Digital AGC device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital AGC device used for a digital radio telephone or the like and for stabilizing the level fluctuation of an input digital signal.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional digital AGC (Automati
c is a block diagram illustrating a configuration of a device.
In FIG. 3, this example shows an amplifier 2 that converts the frequency of a received signal in a digital radio telephone or the like and amplifies an input signal obtained by digitizing an intermediate frequency signal or the like, a squarer 3, and an x ^−1/2 generator. 4, adaptive LPF 5, and amplifier 6
And a multiplier 7.

Next, the operation of this conventional example will be described. Input signal (sampling data) level to amplifier 2
And the squarer 3. The output signal of the ^squarer 3 is input to the x- ^{1 / 2} generator 4 and generates a signal indicating a gain corresponding to the level of the input signal (sampling data).
In this case, the x- ^{1 / 2} generator 4 divides the input value into m sections, and divides each section into a spline function (y
= A ₃ x ³ + a ₂ x ² + a ₁ x + a ₀ ). The spline coefficients (a ₃ , a ₂ , a ₁ , a ₀ ) are read from a spline coefficient table (not shown) provided in the x ^−1/2 generator 4. The output signal of the x- ^{1 / 2} generator 4 is input to the adaptive LPF 5 to obtain a stable output level. The adaptive LPF 5 has a one-sample delay element, and compares the magnitude relationship between the current input value and the previous output value to dynamically change the filter coefficient. By changing the filter coefficient, the rate of change of the output level when the output signal level increases and when the output signal level decreases can be adjusted. Adaptive LPF5
Is input to a multiplier 7 through an amplifier 6, and the multiplier 7 multiplies the input sampling data to obtain an AGC output signal.

As described above, even in the conventional digital AGC device, an AGC output signal whose output level is kept constant can be obtained.

[0005]

In the conventional digital AGC apparatus, all input sampling data is used for control. Therefore, when the above-mentioned AGC processing is performed using a digital signal processor (DSP), the processing time is 28 μs per data, for example, when converted into 200 ns per instruction. That is, the spline function and the adaptive LPF in the entire AGC process
A large part of the time required for the calculation is required, and there is a disadvantage that the digital AGC device is equipped, for example, the stabilization of an input signal in a digital radio telephone cannot be processed at high speed.

The present invention solves such a conventional problem, and can reduce the number of operations of the AGC process, shorten the processing time, and apply the apparatus to which the apparatus is applied, for example,
An object of the present invention is to provide an excellent digital AGC device which can stabilize an input signal in a digital wireless telephone at a high speed.

[0007]

To achieve the above object, according to the Invention The digital AGC apparatus comprising: a detection means for detecting the level of the input signal, where it is detected by the detection means
Smoothing means for smoothing the power of a constant sample signal , function generation means for calculating the gain required to keep the output level constant using a spline function, and stable processing of the output signal from the function generation means Adaptive LPF, delay means for matching an input signal to a delay time when the input signal is processed by the adaptive LPF, and multiplication means for transmitting an AGC output signal obtained by multiplying output signals from the adaptive LPF and the delay means , And the smoothing means determines the number of input samples.
Until the constant is reached, send processing signal to function generator
Is stopped, and when the specified number is reached, processing is performed by the function generator.
It is configured to transmit a signal .

In a digital AGC apparatus according to a second aspect, the smoothing means amplifies an input signal and a delay circuit in which delay elements are connected in series, and amplifies signals from the respective delay elements of the delay circuit. And an amplifier circuit in which a plurality of amplifying elements are connected in series, and further, the input signal and the signal from the first stage of the amplifying element are added, and the signals from the preceding and next-stage amplifying elements are added. And a switch that closes the signal from the adder circuit each time a signal is input from the adder circuit and sends out a processing signal to the function generating means and the adaptive LPF, or a switch that stops sending. It is configured to be provided.

According to a third aspect of the present invention, in the digital AGC apparatus, the function generating means divides the input value into a plurality of sections and obtains an approximate value obtained by processing each section with a cubic spline function.
The output gain corresponding to the input level, which is the average value of the power of a plurality of samples, is obtained.

[0010]

The digital AGC according to any one of claims 1 to 3 having this configuration.
The device smoothes the power of the input signal based on the detected level. Further, a gain necessary for keeping the output level constant is calculated by a spline function, and the calculated signal is processed stably. At this time, whether or not the smoothing means performs the calculation by the function generating means and the adaptive LPF is switched for each of a plurality of (m) samples. As a result, the number of operations of the spline function and the adaptive LPF is reduced to 1 / m
And the AGC processing time is reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a digital AGC apparatus according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a digital AGC apparatus according to an embodiment of the present invention. In FIG. 1, an amplifier 11 converts the frequency of a received signal in a digital radio telephone or the like and amplifies sampling data of an input signal obtained by digitizing an intermediate frequency signal or the like, and squares the sampling data from the amplifier 11 to perform sampling. A squarer 12 for obtaining the power of data and a smoothing unit 13 for smoothing the power obtained by the squarer 12 and having a detailed configuration in FIG. Further, this digital AGC device obtains an approximate value of x ^-1/2 from the output signal of the smoothing unit 13 and obtains an x ^-1/2 generator 14 for obtaining an output gain corresponding to the input level.
An adaptive LPF 15 for obtaining an output level stabilized by the output signal of the x ^-1/2 generator 14, an amplifier 16 for amplifying an output signal from the adaptive LPF 15, and delay elements 17a, 1
.. 17o, a delay unit 17 for matching the sampling data with a delay in the signal processing from the amplifier 11 to the amplifier 16 on the time axis, and the delay unit 1
A multiplied by the output signal from the amplifier 16 to the sampling data from the amplifier 7 to control the gain of the sampling data.
It has a multiplier 18 for sending out a GC output signal. FIG.
3 is a block diagram illustrating a detailed configuration of the smoothing unit 13. FIG. In FIG. 2, the smoothing unit 13 includes, for example, 15
A delay circuit 19 comprising stage delay elements 19a, 19b, 19c... 19o;
9 from the respective delay elements 19a to 19o,
Each of the 16 amplifying elements 20a, 20b, 2
0c, 20d... 20q (amplification ratio 1/16), and an input signal and the first-stage amplification element 2
0a, and further adds the signals from the preceding and next amplification elements (20a to 20q).
Adder 21 having 1a, 21b, 21c... 21q
And a switch 22 for outputting (ON) the signal from the adding circuit 21 or stopping (OFF) the output.

Next, the operation of this embodiment will be described. The sampling data is input to the squarer 12 through the amplifier 11. The squarer 12 squares the sampling data to obtain the power of the sampling data. The output signal of the squarer 12 is input to the smoothing unit 13 shown in FIG. As shown in FIG. 2, the smoothing unit 13 includes, for example, a delay circuit 19 including 15 stages of delay elements 19a to 19o and an amplification circuit 20 including 16 amplification elements (20a to 20q) (an amplification factor of 1/20). 16) and a switch 22. The amplification elements (20a to 20a) of the amplification circuit 20 here are provided.
By adding the output signals from 20q), the average value of the power of 16 samples from the data 15 samples before to the data input this time is obtained. In this case, the switch 22 is closed every time 16 input signals are input. The switch 22 counts the sampling data using a counter (not shown), and resets the count every 16 samples. That is, the smoothing unit 1
The output signal from 3 is input to x-1 / 2 generator 14 every 16 sample inputs. Therefore, every 16 samples input, the average value of the power of the 16 samples is input to the x ^-1/2 generator 14. In this embodiment, x ^-1/2 generator 1
4 divides the input value into 13 sections, the respective section cubic spline function ^{_{(y = a 3 x 3 +}} a 2 x 2 + a 1 x + a 0), to obtain an approximate value of x ^-1/2, input Find the output gain corresponding to the level. The output signal of the x- ^{1 / 2} generator 14 is input to the adaptive LPF 15 to obtain a stable output level. The adaptive LPF 15 includes a one-sample delay element, and compares the magnitude relationship between the current input value and the previous output value,
Dynamically change filter coefficients. By changing the filter coefficient, the rate of change of the output level when the output signal level increases and when the output signal level decreases can be adjusted.
After the output signal from the adaptive LPF 15 is amplified by the amplifier 16, the input signal is held while 16 samples are input, and has the same delay time as the delay circuit 19 of the smoothing unit 13. 15-stage delay element 1
The input sampling data that has passed through the delay unit 17 consisting of 7a to 17o is multiplied by a multiplier 18. Thus, an AGC output signal is obtained.

[0013] calculation of the x ^-1/2 generator 14 and adaptive LPF15 is performed only when the switch 22 is closed (on), in the case of off-x ^-1/2 generator 14 and adaptive LPF15
Is not performed, and the input sampling data passed through the delay unit 17 is multiplied by the coefficient held at that time.
The delay unit 17 operates so that the sample group used for the calculation of the x ^-1/2 generator 14 and the adaptive LPF 15 and the sample group multiplied by the coefficient obtained by the calculation have the same time axis. That is, deterioration of dynamic characteristics is prevented.

In this case, the static characteristics and the dynamic characteristics are almost the same as those of the conventional example, for example, when the digital AGC device is mounted on a digital radio telephone, there is almost no difference in the audibility of a received call.

As described above, in this embodiment, the number of operations of the x- ^{1 / 2} generator 14 and the adaptive LPF 15 is reduced, and the processing time is reduced. (AGC) is processed at a high speed, and a high-quality call is made possible.

[0016]

As is apparent from the above description, the digital AGC apparatus according to any one of claims 1 to 3 smoothes the power of an input signal based on the detected level and maintains the output level constant. The required gain is calculated using a spline function. Further, since the calculated signal is stably processed, and whether or not the smoothing means performs the calculation by the function generating means and the adaptive LPF is switched for each of a plurality of (m) samples. The number of operations of the adaptive LPF is reduced to 1 / m, and the processing time of the AGC is shortened. For example, stabilization of an input signal in a digital wireless telephone can be processed at a high speed.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a detailed configuration of a smoothing unit in FIG. 1;

FIG. 3 is a block diagram showing a configuration of a conventional digital AGC device.

[Explanation of symbols]

^{Reference Signs List} 12 squarer 13 smoothing unit 14 x- ^{1 / 2} generator 15 adaptive LPF 17 delay unit 18 multiplier 19 delay circuit 20 amplifying circuit 21 addition circuit 22 switch

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-351110 (JP, A) JP-A-1-146413 (JP, A) JP-A-2-33220 (JP, A) 148417 (JP, A) JP-A-1-200709 (JP, A) JP-A-6-121018 (JP, A) JP-A-64-33230 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03G 1/00-3/34

Claims (1)

(57) [Claims] 1. A detecting means for detecting the level of an input signal, a smoothing means for smoothing the power of a predetermined number of sample signals detected by the detecting means, and a gain required to keep the output level constant. , An adaptive LPF for stably processing an output signal from the function generating means, and a delay time when the input signal is processed by the adaptive LPF from the detecting means. delay means for causing comprises a multiplication means for transmitting an AGC output signal obtained by multiplying the output signal from said adaptive LPF and said delay means, said smoothing means, the input sample
Until the number reaches the predetermined number, the function generation means
When the transmission of the processing signal is stopped and the predetermined number is reached,
A digital AGC device for sending a processing signal to said function generating means .