JP2002164755A - Digital receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital receiving device capable of preventing the omission of any signal information by compensating signal waveform distortion in an AGC circuit (or a post-A/D converter) output even when the number of channel signals to be used is increased. SOLUTION: In this digital receiver in which a plurality of received channel signals are introduced through a filter and an AGC circuit through which the plurality of channel signals are allowed to pass to an A/D converter, and converted into digital signals, and demodulated, the inverse number of the degree of amplification of the AGC circuit is calculated from a control signal for controlling the degree of amplification and the plurality of channel signals to be inputted to the AGC circuit based on this are reproduced at the output of the A/D converter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital receiver, and more particularly to a means for improving signal distortion when a plurality of channel signals are simultaneously input to an AGC circuit.

[0002]

2. Description of the Related Art In recent years, with the development of digital circuit technology,
Examples of realizing functions realized by analog circuits using digital circuits are increasing. DS as a digital circuit
When a programmable device such as P (digital signal processor) is used, the functions are realized by software, so it is easy to modify and change the characteristics, and there is no variation or deterioration over time, or no adjustment is required Is obtained.

[0003] In the field of mobile communication such as a digital cellular phone, the shift to the digital circuit has been progressing, and as an ultimate example, a software defined radio that realizes most of the communication functions by software has been proposed.
Details are described in the following document, so the description is omitted.
(Joe Mitola, The software radio architecture, IEEE
Communication magazine, May 1995 vol.33, No.5). However, in reality, wideband amplifiers, mixers, local oscillators, or high-speed A / D (analog / digital) converters, as required in the above-mentioned documents, are currently difficult to realize, so the high-frequency section and the IF section The following configuration has been proposed for analog processing.

FIG. 2 is a functional block diagram showing a configuration example of a conventional digital receiving apparatus. The digital receiving apparatus shown in this example includes an antenna 102 through an RF bandpass filter 101.
After the output signal of the amplifier 103 connected to the filter 104 is guided to the mixer 104 and converted to a predetermined frequency by the output signal of the local signal oscillator 105, the IF band-pass filter 106
And AGC (Automatic Gain Control) circuit 107
And is supplied to the A / D converter 108 through.

[0005] The digital receiving apparatus shown in this example functions as follows. That is, a high-frequency analog signal including a plurality of channel signals received via the antenna 102 is subjected to removal of unnecessary components by an RF band-pass filter 101 having a required bandwidth, and is amplified by an amplifier 103. The oscillator 105 and the mixer 104
The frequency is converted to an IF frequency and supplied to the IF pass filter 106.

[0006] The IF pass filter 106 has a wide band characteristic so that a plurality of channel signals relating to various modulation schemes realized by software modification of a DSP in a demodulation processing unit (not shown) can pass through. After the unnecessary components are removed again here, the A / D converter 1
The gain g of the AGC circuit is controlled based on the control signal 107a so that the maximum level is constant within the dynamic range of 08, and is converted to a digital signal by the A / D converter 108 for channel separation / demodulation processing. Supplied to the department, where D
Digitally processed by SP.

FIG. 3 is a conceptual diagram illustrating a composite waveform relating to a plurality of channel signals at the input of the AGC circuit 107.
This figure shows an example in which two channel signals having the same amplitude level are input for the sake of simplicity.
These two signals s1 and s2 have frequencies f1 and f2, respectively (FIGS. 3A to 3C), and when these signals are superimposed in the same phase, the signals become added and the amplitude becomes large, but the opposite occurs. Since the amplitude is reduced due to the subtraction at the timing of superimposition in the phase, the superimposed signal of the two signals s1 and s2 has a waveform in which the maximum amplitude value temporally fluctuates as shown in FIG.

[0008]

However, the conventional digital receiver as described above has the following problems. In other words, when a superimposed signal as shown in Fig. 3 (d) is input to the AGC circuit, the AGC circuit functions to keep the input signal constant at the maximum signal level within the operating dynamic range of the subsequent A / D converter. I do. However, in order to improve the frequency use efficiency, for example, when the number of channel signals increases to about 100 channels, the superimposed signal level becomes AG
When the saturation level (operating dynamic range) of the C circuit is exceeded, the waveform is clipped (a phenomenon in which the leading end of the waveform is cut). FIG. 4 is a diagram illustrating a waveform example of the superimposed signal in the output of the AGC circuit in such a case. As shown in this figure, the superimposed signal causes waveform distortion, and as a result, there is a problem that frequency information (signal information) is lost. The present invention
The purpose of this is to solve the above-mentioned problems related to the conventional digital receiver. Even when the number of channel signals used increases, the signal waveform distortion is compensated at the output of the AGC circuit (or the A / D converter at the subsequent stage). It is another object of the present invention to provide a digital receiving apparatus capable of preventing loss of signal information.

[0009]

According to a first aspect of the present invention, there is provided a digital receiving apparatus according to the present invention, comprising a filter capable of passing a plurality of channel signals received by the plurality of channel signals. A / D through and AGC circuit
In a digital receiver that performs a demodulation process after converting the signal into a digital signal, the reciprocal of the amplification degree is calculated from a control signal that controls the amplification degree of the AGC circuit, and input to the AGC circuit based on this. The plurality of channel signals to be reproduced were reproduced at the output of the A / D converter. The invention according to claim 2 of the digital receiving apparatus according to the present invention includes an AGC circuit to which a plurality of channel signals are input and a first
An A / D converter, a multiplier, an amplification reciprocal calculator for calculating the reciprocal of the amplification of the AGC circuit and a second A / D converter are connected in a loop, and the amplification of the AGC circuit is adjusted. A control signal to be controlled was supplied to the reciprocal amplification degree calculating section via the second A / D converter, and a plurality of channel signals input to the AGC circuit at the output of the multiplier were reproduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a functional block diagram showing an embodiment of a digital receiving apparatus according to the present invention. The digital receiver shown in this example guides the output signal of the amplifier 13 connected to the antenna 12 via the RF band-pass filter 11 to the mixer 14, and converts the output signal to a predetermined frequency by the output signal of the local signal oscillator 15. rear,
The signal is supplied to a multiplier 19 via an IF band-pass filter 16 having a bandwidth to be described later, an AGC circuit 17, and a first A / D converter 18. Also, the control signal 17a in the AGC circuit 17 calculates the reciprocal of the amplification of the AGC circuit via the second A / D converter 20 and supplies the control signal 17a to the amplification reciprocal calculation unit 21 connected to the multiplier 19. The configuration is as follows.

The digital receiver shown in this example functions as follows. That is, a high-frequency analog signal including a plurality of channel signals received via the antenna 12, after removing unnecessary components by an RF bandpass filter 11 having a required bandwidth and amplifying by an amplifier 13, the local signal oscillator 15 and The frequency is converted to a predetermined IF frequency by the mixer 14 and supplied to the IF pass filter 16.

The band characteristic of the IF pass filter 16 is set so that it can pass all of a plurality of channel signals related to various modulation schemes realized by software modification of a DSP in a demodulation processing unit (not shown). After removing the signal unnecessary component again here, while controlling the amplification g of the AGC circuit 17 based on the control signal 17a so that the maximum level of the received signal is constant within the dynamic range of the A / D converter, The signal is converted into a digital signal by the A / D converter 18 and supplied to the multiplier 19.

As described above, the control signal 17a of the AGC circuit 17
Controls the amplification degree g of the AGC circuit, and therefore has information relating to the amplification degree g.
Is converted to a digital signal via the second A / D converter 20, and then based on the information of the amplification g, the reciprocal 1 / g relating to the amplification g of the AGC circuit 17 is calculated by the amplification reciprocal calculating unit 21 based on the information of the amplification g. The calculated value is supplied to the multiplier 19. The signal Sin at the input of the AGC circuit 17 becomes gSin at the output of the AGC circuit, and when the number of received channel signals is large, the waveform becomes a distortion waveform as shown in FIG. 4, but 1 / g is calculated by the multiplier 19 at the subsequent stage. Since the multiplication is performed, Sin without distortion is reproduced at the output of the multiplier 19, and therefore, loss of signal information can be prevented.

[0014] In short, the digital receiving device of the present invention comprises:
Amplification degree in the AGC circuit based on the control signal of the AGC circuit
The input signal of the AGC circuit is reproduced by calculating the reciprocal 1 / g of g and multiplying this by the output signal of the A / D converter whose input signal has been multiplied by g through the AGC circuit. Therefore, the reproduced signal does not have a waveform distortion related to the signal level control of the AGC circuit, and as a result, does not lose signal information.

[0015]

As described above, according to the present invention, the reciprocal 1 / g of the amplification degree of the AGC circuit is separately calculated from the control signal of the AGC circuit, and the reciprocal 1 / g is calculated from the output of the A / D converter arranged at the subsequent stage of the AGC circuit. By multiplying the signal, the input signal of the AGC circuit was reproduced at the output of the A / D converter, so there was no waveform distortion related to the signal level control of the AGC circuit regardless of the number of reception channels.
Therefore, the present invention is very effective in realizing a digital receiver capable of reproducing a plurality of channel signals without loss of signal information (frequency information).

[Brief description of the drawings]

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

FIG. 2 is a functional block diagram showing a configuration example of a conventional digital receiving device.

FIG. 3 is a diagram for explaining the concept of a signal waveform at an input of an AGC circuit;

FIG. 4 is a view for explaining the concept of a signal waveform at the output of the AGC circuit;

[Explanation of symbols]

 11 RF bandpass filter 12 Antenna 13 RF amplifier 14 Mixer 15 Local signal oscillator 16 IF bandpass filter 17 AGC circuit 18 First A / D converter 19 ..Multiplier 20..Second multiplier 21..Reciprocal calculator of amplification degree of AGC circuit

Claims (2)

[Claims] 1. A digital receiving apparatus for guiding a plurality of received channel signals to an A / D converter via a filter through which the plurality of channel signals can pass and an AGC circuit, converting the signals into digital signals, and performing demodulation processing. In, while calculating the reciprocal of the amplification degree from a control signal for controlling the amplification degree of the AGC circuit, based on this, the plurality of channel signals input to the AGC circuit were reproduced at the output of the A / D converter A digital receiver characterized by the above-mentioned. 2. An AGC circuit to which a plurality of channel signals are input, a first A / D converter, a multiplier, an amplification reciprocal calculator for calculating a reciprocal of the amplification of the AGC circuit, and a second A / D. While connecting the converter and a loop, a control signal for controlling the amplification of the AGC circuit is supplied to the amplification reciprocal calculation unit via the second A / D converter, and the output of the multiplier is A digital receiver, wherein a plurality of channel signals input to the AGC circuit are reproduced.