JPS58201423A - Receiver - Google Patents

Abstract

PURPOSE:To eliminate a impulsive noise and a synchronizing noise effectively with high S/N improvement and excellent sound quality characteristics, by providing a comb line filter having a broad pass band for a sound signal system. CONSTITUTION:The comb line filter 27 is provided at a post-stage of a detecting circuit 26 of a receiver 20. Filter characteristics of the comb line filter 27 are set to narrow band pass band characteristics by turning all switches 381- 38n on. In this case, since the pitch of a sound signal is converted into a prescribed value with a sound pitch converter 13 of a transmitter 10, the frequency pitch of the pass band of the comb line filter 27 is also matched to this prescribed value and the noise with respect to white noise is eliminated with the stop band. The impulsive noise is also eliminated by adopting the filter characteristics as eliminator characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiver that can effectively remove interference signals received by radio waves during their propagation paths.

Normally, the radio wave signal emitted from the transmitter is received by the receiver, and before it is emitted from the speaker, etc., it is subject to various forms of electrical interference, and its S/N ratio is generally deteriorated. It is. In particular, the influence of so-called urban noise is large in the radio wave propagation path, and 87N is degraded by all types of noise (periodic, random, etc.). By suppressing the influence of such noise 8/
In order to improve N, it may be possible to improve the communication system itself by changing it to a PCM communication method, etc. However, in the conventional communication bands permitted under the Radio Law (such as CB band) Currently, the communication method is not permitted and cannot be used.

Therefore, in order to remove such noise interference, a formant band division method as shown in Fig. 1 has been proposed, for example, which improves 87N by removing the band that is relatively necessary for voice information and narrowing the used bandwidth. .

That is, in FIG. 1, fmin and fmax are the minimum and maximum frequencies of the used bandwidth, respectively, and the frequency fm
The first formant is between in and fl, frequencies f2 and fma
The space between X represents the second formant. The frequency range between frequencies f1 and fz shown by diagonal lines in FIG. 1A is a band that is relatively unnecessary for audio information. Therefore, this unnecessary band is removed to create the audio spectrum as shown in FIG. 1B. In FIG. 1B, the frequency fx is fx
” fmax-(fz h ).

However, in such a conventional method, it is difficult to separate the signal voice band and the voice band noise, and it would be better if the pass band ratio could be reduced to 1/2 using this polar band division method.

Therefore, the present applicant has first developed a transmission/reception system that can eliminate various noise disturbances received in the radio wave propagation path and perform N-optimal communication within the scope of the communication system permitted by the current Radio Law. proposed a device.

Below, such a transmitting/receiving device will be explained with reference to FIGS. 2 to 5.

FIG. 2 schematically shows this transmitting/receiving device. In the figure, α1 is a transmitter, and the handle is a receiver.

The transmitter α1 consists of a microphone 0υ, an amplifier 0'IJ1, an audio pitch converter 03, a modulator 0, a transmitting circuit 01 including a power amplifier, etc., and a transmitting antenna Oe, which will be explained in detail later, except for the audio pitch converter O1l. This is a conventional circuit.

Note that the oscillation unit of the transmitter 0 is not shown here.

Normally, the fundamental pitch frequency of the speech spectrum varies depending on whether the voice is male or female or due to the intonation of the neck lobe, but this change is converted into a substantially constant value by passing through the voice pitch converter (3). As this audio pitch converter (3), for example, one having a configuration as shown in FIG. 3 is used. Third
The figure shows a case where an audio signal is processed in 7 frames. audio signal 8
Load D into memory frame by frame. Furthermore, the microcomputer Gυ inputs the basic pitch information P into the interval N(
The positive integer) value information is calculated and supplied to a synthesizer oscillation circuit consisting of, for example, a PLL circuit.

The synthesizer side oscillation circuit (to) consists of a frequency divider (32m), a reference oscillator (32b), a divider (32a) and a reference oscillator (
A phase comparator (32c) that compares the phases of both outputs of (32b)
), a low-pass F-wave device (
32d) and a voltage-controlled oscillator (hereinafter referred to as ``CO'') (32e) whose oscillation frequency is controlled by the DC signal from the low-frequency F wave generator (azd) according to its error. The output frequency of the synthesizer generator circuit (company), that is, the oscillation frequency of the VCO (32e), is further increased by the division ratio m
(a positive integer) is supplied to the microcomputer Gυ as a read clock CLK2. The synthesizer oscillation circuit (to) determines the section read clock based on the N-value information and generates the read clock CLK2.

This read clock CLK2 is delay-corrected by the microcomputer Gυ, and the delay-corrected read clock CLK2 is used to generate the audio signal S stored in the memory.
D is read and read out, and a digital signal SD', which has been converted by the read clock CLK2, is obtained on the output side of the microcomputer Gυ. This digital signal Sd is converted into an analog signal by a digital-to-analog converter (B), and then output to an output terminal (To) through a low-pass wave transducer (To). The converted audio signal So is extracted, and this signal s□ is used as a modulation signal for the transmitter.

Returning to Figure 2, the receiver consists of a receiving antenna Qυ, a high frequency amplifier circuit (2), a mixing circuit (C), a local oscillation circuit (2), an intermediate frequency amplifier circuit (C), and a detection circuit. □
It consists of a comb-shaped filter (5), an audible phono amplifier circuit (c), and a speaker (to), which will be described in detail later.The circuits other than the comb-shaped filter (a) are conventional circuits.

A comb filter@ generally has filter characteristics as shown in FIG. 4E. For example, in an analog signal (not necessarily an analog signal) as shown in Figure 4, a fourth
They are lined up at regular intervals as shown in Figure B ( f
If an unnecessary signal (domain) is mixed in and a composite signal as shown in FIG. 4C is formed, the spectrum of this signal is expressed as shown in the fourth diagram. In the fourth diagram, fp is the fundamental pitch frequency. Therefore, when a composite signal having such a spectrum is passed through a comb filter (2) having filter characteristics as shown in FIG. 4E, a signal from which unnecessary signals have been substantially removed, as shown in FIG. Figure 4: A signal substantially similar to the human input analog signal is obtained. The degree to which some unnecessary signals remain in the extracted signal as shown in FIG. 4F is determined by the attenuation characteristic of the filter (2).

Next, the operation of this transmitter/receiver will be explained with reference to FIG. As shown in FIG. A pitch conversion operation is performed, and a sound spectrum signal having a constant pitch P2 as shown in FIG. 5B is extracted on the output side.
This signal is supplied to modulator α4 as a modulation source or modulation frequency. Then, it is superimposed on a predetermined carrier wave and is emitted as a radio signal from the transmitting antenna 0e via the transmitting circuit a9. This radio wave signal is electrically subjected to various interferences on its propagation path to the receiver (2), and the interference at this time is shown in Figure 5C. In Figure 5C, n represents interference noise There is.

The radio signal captured by the receiving antenna C711 of the receiver (to) is amplified by the high frequency circuit (2) and then supplied to the mixing circuit, where it is mixed with the local oscillation signal from the local oscillation circuit t24) to generate a high frequency signal. The signal is converted into an intermediate frequency signal. This intermediate frequency signal is amplified by an intermediate frequency amplifier circuit (E), demodulated into an audio frequency signal by a detection circuit (1), and supplied to a comb filter (5).

As shown in the fifth diagram, this comb-shaped filter has a filter characteristic set to the pitch P2 of the audio signal on the transmitting side,
Therefore, in this case, on the output side of the comb-shaped filter, an audio signal from which noise components have been substantially removed is obtained as shown in FIG. 1 Nodas Band (Pa5s Ban)
d) Determined with dilute acid.

The audio signal from which noise components have been substantially removed in this way is amplified by the audio frequency amplification circuit (2) and then emitted from the speaker (c). Note that if the pitch of the audio signal is constant, there is a risk that the intonation will be lost, but this is not particularly inconvenient for determining the meaning of words, and the intended purpose of transmitting information can be reliably achieved.

According to such a transmitter/receiver, the pitch of the audio signal to be transmitted is fixed, and the audio signal is extracted by correlating this pitch on the receiving side, so that the audio signal and noise within the audio band can be reliably separated. S/ on the receiving side
Since N can be improved, it is extremely useful especially when the wave propagation path is easily affected by urban noise. As can be seen from the above, the degree of improvement in S/N depends on the pitch fixing rate of the audio signal on the transmitting side (the rate of how accurately it can be fixed) and the narrowness of the comb filter on the receiving side and the mother span band. Substantially determined by banding.

By the way, if the noise is white noise, there is no problem, but if the noise is lousous or periodic, the S/N improvement and sound quality characteristics are not very good with the above transmitting/receiving device. There is a drawback.

In view of this, the present invention is aimed at reducing ignition noise, etc.
The purpose of the present invention is to propose a receiver capable of removing random noise and periodic noise with a high degree of S/N improvement and good sound quality characteristics.

An embodiment in which the present invention is applied to a transmitting/receiving device will be described in detail below with reference to FIG.
The same reference numerals are given to the parts corresponding to t, and redundant explanation will be omitted.

A comb filter (C) is provided in the audio signal system of the receiver ■, that is, after the detection circuit (E).The comb filter (C) will be explained below.C37) is n (2e3e4e・
...) In the BBD (packet brigade device) of the stage, a tag is derived from each stage 5l-Sn, and each tap is an on/off switch (381).
~(38n) through resistor R1;R1'~Rn;R
d, and the other end of the resistor R1 and the other end of the resistor R1' are respectively connected to the inverting input terminal and the non-inverting input terminal of the operational amplifier ■ constituting the adder uD. Ru. A negative feedback resistor (43) is connected between the output terminal and the inverting input terminal of the operational amplifier (42j).

The output terminal of this adder (41) is connected to the input side of the amplifier circuit (to). (to) is the clock oscillator, and this
The two-phase lock signals φl and φ2 from the side are BBD((
? ). Note that this clock signal φ1. The frequency of φ2 can be varied by adjusting the variable resistor (41) attached to the oscillator.

Next, the operation of the receiver shown in FIG. 6 will be explained. In the first case, by turning on all switches (381) to (38n), the filter characteristics of the comb filter (b) are changed to the seventh
As shown in the figure, the narrow band flat spant characteristic is set. In this case, the pitch of the audio signal is converted to a predetermined value by the transmitter Ql as in FIG. 2, so the frequency pitch of the A span of the comb filter forehead is also adjusted to this predetermined value. The strug band eliminates white noise yarn noise.

In the second case, by turning on two (or even three) switches with the same weight, e.g., switches (381) and (382), and turning off all the remaining switches, the comb filter is The filter characteristics are selected to be broadband flat spant (eliminator) characteristics as shown in FIG. 8 or 9. Also, set variable resistor 4 according to the frequency pitch of the noise! 111m, and the clock signal φ1. The frequency of φ2 is continuously varied 2, and the stopband frequency is varied. Note that the clock frequency can be varied significantly by selectively turning on switches other than switches S1 and s2. By doing so, when the noise is noise such as ignition noise or periodic noise, the noise can be effectively removed by the comb filter (b). In this case, the existence of the pitch converter 03 of the transmitter Ql becomes meaningless.

According to the receiver of the present invention described above, the audio signal system has a wide band
A comb-shaped filter is provided for the mother band, and a stop-band frequency variable means is provided in the comb-shaped filter.
- Routine and periodic noise can be effectively removed with a high 8/N improvement and good sound quality characteristics.

In addition, when installing an audio pinch converter in the transmitter to keep the pitch of the audio signal constant, and switching the filter characteristics of the comb filter in the receiver to narrowband/main span characteristics, white noise type noise can also be effectively used. Can be removed.

[Brief explanation of the drawing]

Figure 1 is a characteristic curve diagram demonstrating the conventional method, and Figure 2
The figure is a block diagram showing an example of the transmitting/receiving device proposed previously, and FIG. 3 is a block diagram showing the detailed configuration of a part thereof.
4 and 5 are waveform diagrams for explaining the manufacture of the transmitting and receiving device shown in FIG. 2, FIG. 6 is a block diagram showing one embodiment of the present invention, and FIGS. 7, 8, and 9 are FIG. 7 is a curve diagram showing filter characteristics of the comb-shaped filter of FIG. 6; The wire is the receiver, (271 is the comb-shaped filter, and the third one is the stop band frequency variable means.)

Claims (1)

[Claims] 1. A receiver characterized in that a comb filter having a wide band and main span is provided in an audio signal system, and a stop band wave number variable means is provided on the comb filter.