JP2002261642A - Receiving machine - Google Patents

Abstract

(57) [Summary] The present invention can suppress the peak level fluctuation of a composite waveform of a received signal even when an unnecessary signal having a higher level than a desired signal is received, thereby reducing the following speed of the AGC circuit. An object of the present invention is to provide a receiver that can be delayed and does not affect amplitude information of an amplitude modulation method such as an SSB modulated signal. SOLUTION: In a receiver for conducting a demodulation process after guiding a plurality of received channel signals to an A / D converter through a filter and an AGC circuit through which the plurality of channel signals can pass, and converting the digital signals into digital signals, By adding a pilot signal having a predetermined level outside the band of the filter in advance, the level fluctuation related to the composite waveform of the plurality of channel signals is suppressed when receiving unnecessary channel signals. Receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver, and more particularly to a means for suppressing an instantaneous level fluctuation of a signal composite waveform due to reception of an unnecessary channel signal in a configuration in which 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. 3 is a functional block diagram showing a configuration example of a conventional digital receiver. The digital receiver shown in this example guides an output signal of an amplifier 103 connected to an antenna 102 via an RF band-pass filter 101 to a mixer 104, and converts the output signal to a predetermined frequency by an output signal of a local signal oscillator 105. After that, IF band pass filter 106 and AGC
(Automatic Gain Control) circuit 107 and the A / D converter 108.

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

The IF band-pass filter 106 has a wide band characteristic so that a plurality of channel signals related 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 amplification degree g of the AGC circuit based on the control signal 107a is adjusted so that the maximum level is constant within the dynamic range of the A / D converter 108.
Is controlled, and is converted into a digital signal by the A / D converter 108 and supplied to the channel separation / demodulation processing unit.
Here, digital processing is performed by the DSP.

FIG. 4 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. 3 (a) to (c)), and when these signals are superimposed in the same phase, they are added and the amplitude is increased, but 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.

FIG. 5 shows the frequency spectrum at the input of the AGC circuit when an unnecessary signal Su (a channel signal not used for the current communication) having a level 60 dB higher than this signal is received during communication using the desired signal Sd. FIG. In this case, the composite waveform of the signals has a level difference of 60 dB between the two signals.
Therefore, the peak level is larger than that in the case of FIG. 4 described above, and changes instantaneously (the level changes quickly)
Will be. Therefore, even in such a case, it is necessary to increase the following speed (time constant) of the AGC circuit so that the received plurality of channel signals do not exceed the dynamic range of the A / D converter.

[0009]

However, the conventional receiver as described above has the following problems. In other words, this receiver uses DS in the demodulation processing unit.
It is configured to be compatible with various modulation schemes by changing the software of P. By the way, an AGC circuit that varies the amplitude level is unnecessary for the amplitude modulation method, and for example, an SSB (Single S
ide Band) When receiving a modulated signal, this signal is typically 300
Since the carrier wave is amplitude-modulated by an audio signal having a frequency component of -2700 Hz, if the tracking speed of the AGC circuit is slower than the period of the audio signal, the rate at which the signal amplitude is changed by the AGC is the signal As a whole, the amplitude information of the signal is not so much affected and does not matter. However, when the follow-up speed of the AGC circuit is increased as described above, the rate at which the signal amplitude is changed from the viewpoint of the entire signal increases, and communication of the amplitude modulation method is affected by amplitude information (missing) and communication cannot be performed. There was a problem. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems related to the conventional receiver. Even when an unnecessary signal having a higher level than a desired signal is received, the instantaneous peak level related to the composite waveform of the received signal is obtained. It is an object of the present invention to provide a receiver that can suppress fluctuations and therefore does not need to increase the following speed of an AGC circuit, and therefore does not affect amplitude information included in an amplitude modulation signal such as an SSB modulated signal. I do.

[0010]

According to a first aspect of the present invention, there is provided a receiver according to the present invention, comprising a filter capable of passing a plurality of received channel signals through the plurality of channel signals. An AGC circuit leads the signal to an A / D converter, and in a receiver that performs demodulation after converting the signal into a digital signal, by adding a pilot signal having a predetermined level outside the band of the filter in advance, an unnecessary channel is added. When receiving a signal, a level fluctuation relating to a composite waveform of the plurality of channel signals is suppressed. The invention according to claim 2 of the receiver according to the present invention is such that, in the receiver according to claim 1, an adder in which a signal oscillator that generates the pilot signal is connected between the filter and an AGC circuit is arranged. I made it.

[0011]

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 receiver according to the present invention. The receiver shown in this example guides an output signal of an amplifier 13 connected to an antenna 12 via an RF band-pass filter 11 to a mixer 14, and converts the output signal to a predetermined frequency by an output signal of a first local signal oscillator 15. After the conversion, A is passed through an IF bandpass filter 16 having a bandwidth to be described later and an AGC circuit 17.
Supply to the / D converter 18. Also, the IF band-pass filter
A second local signal oscillator 1 for generating a pilot signal of amplitude A characterizing the present invention between 16 and AGC circuit 17
An adder 20 to which 9 is connected is arranged.

The 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 is removed by an RF band-pass filter 11 having a required bandwidth, an unnecessary component is removed, and the amplified signal is amplified by an amplifier 13. The frequency is converted to a predetermined IF frequency by the oscillator 15 and the mixer 14 and supplied to the IF band-pass filter 16.

The band characteristics of the IF band-pass filter 16 are set so as to be able to 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 the signal unnecessary component is removed again here, the amplification degree g of the AGC circuit 17 based on the control signal 17a is adjusted so that the received signal becomes constant within the dynamic range of the A / D converter 18.
, And is converted into a digital signal by the A / D converter 18 and supplied to a channel separation / demodulation processing unit (not shown).

On the other hand, the pilot signal output from the second local signal oscillator 19 is set in advance to output a signal having a frequency outside the band of the IF band-pass filter 16 before receiving a plurality of channel signals. The signal is input to the AGC circuit 17 via the adder 20. When a plurality of channel signals are received, the pilot signal is added to this received signal in adder 20.

FIG. 2 shows a frequency spectrum at the input of the AGC circuit when an unnecessary signal Su (a channel signal not used for the current communication) having a higher level than this signal is received during communication using the desired signal Sd. FIG. As described above, the receiver according to the present invention has a predetermined level sufficiently higher than the reception level assumed as the desired signal Sd in advance.
(80 dB in this embodiment) is generated and input to the AGC circuit 17, so that the peak level of the composite waveform of the received signal in the absence of a strong unnecessary signal is the desired signal Sd and the pilot signal This is a combination with Sp, and the peak level of the pilot signal Sp becomes dominant in effect. For example, as shown in FIG.
When 0 dB is selected, even if an unnecessary signal Su of 60 dB higher than this is received, the 80 dB level is always input to the AGC as the pilot signal Sp, so the instantaneous fluctuation width related to the peak level of the composite waveform of the received signal Can be increased by up to 3dB. If the level of the unnecessary signal Su is 80 dB or less, the instantaneous fluctuation width of the peak level of this waveform can be made 3 dB or less.

More generally, when an unnecessary signal Su having a level Lu higher than the level Lp of the pilot signal Sp is received as shown in FIG. 2 (b), it is accompanied by a level difference of (Lu-Lp). An instantaneous variation (increase) related to the peak level of the composite waveform occurs. However, even if an unnecessary signal level Lu twice as large as the pilot signal level Lp is received, the instantaneous fluctuation width of the peak level of the composite waveform can be suppressed to a maximum of 6 dB.

Therefore, even if an unnecessary signal having a higher level than the desired signal is received during a call, the instantaneous fluctuation width related to the peak level of the synthesized waveform can be suppressed. It is not necessary to increase the following speed, and therefore, even when a signal of the amplitude modulation method is received, it is possible to prevent a loss of amplitude information that may hinder communication.

In short, the receiver of the present invention is to input a pilot signal having a predetermined level to an AGC circuit in advance and suppress an instantaneous level fluctuation of a composite waveform caused by an unnecessary signal received during communication. This eliminates the need to increase the tracking speed of the AGC circuit, thereby preventing the loss of amplitude information even when receiving an amplitude modulation signal.

[0019]

As described above, according to the present invention, by inputting a pilot signal having a predetermined level to an AGC circuit in advance, it is possible to suppress the instantaneous level fluctuation of a composite waveform relating to a plurality of received signals. Thus, the present invention is very effective in realizing a receiver capable of preventing a loss of amplitude information of a signal by the amplitude modulation method without increasing the tracking speed of the AGC circuit.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating an embodiment of a receiver according to the present invention.

FIG. 2 is a diagram illustrating frequency spectra of a desired signal, an unnecessary signal, and a pilot signal in the receiver according to the present invention.

FIG. 3 is a functional block diagram illustrating a configuration example of a conventional receiver.

FIG. 4 is a diagram illustrating the concept of a signal waveform at the input of the AGC circuit.

FIG. 5 is a diagram showing frequency spectra of a desired signal and an unnecessary signal in a conventional receiver.

[Explanation of symbols]

 11 RF bandpass filter 12 Antenna 13 RF amplifier 14 Mixer 15 First local signal oscillator 16 IF bandpass filter 17 AGC circuit 18 A / D converter 19 ..Second local signal oscillators 20.Adders

Claims (2)

[Claims] 1. A receiver for performing a demodulation process after guiding a plurality of received channel signals to an A / D converter through a filter and an AGC circuit through which the plurality of channel signals can pass and converting the signals into digital signals. Adding a pilot signal having a predetermined level outside the band of the filter in advance to suppress level fluctuations related to a composite waveform of the plurality of channel signals with respect to reception of unnecessary channel signals. And receiver. 2. The receiver according to claim 1, wherein an adder connected with a signal oscillator for generating the pilot signal is arranged between the filter and an AGC circuit.