JPS6143835A - Muting device of radio receiver - Google Patents

Abstract

PURPOSE:To improve the intermodulation disturbance without losing the reception characteristic at a weak input by using a controller having an operating function such as a microcomputer function so as to control a reception frequency, to retrieve and operate the presence of a broadcast radio wave invaded to a desired reception frequency and its intensity and to control the reduction in the disturbance in response to the result. CONSTITUTION:A controller 10 is connected to a programmable divider 54 of a local oscillation circuit 5 to control a frequency dividing ratio N and is provided with an operation processing section 110 processing a signal based on a program of a program section 120 and with a storage device 130. That is, the presence of a broadcast wave having a frequency disturbing a desired reception frequency is discriminated by varying the reception frequency, and when this disturbing wave exceeds a set level of a level detector 14, a gain controller 15 being a disturbance reducing means is controlled by an output signal of an operation processing section 110 of the controller 10 so that the characteristic at a weak signal is not lost when no disturbing signal exists and the effect of the disturbance is improved when any disturbing signal exists.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a muting device in a radio receiver.

[Background of the invention]

FM radio broadcasting is widely available due to its high quality.

However, there is a strong desire for more sources from viewers. In other words, the number of broadcast stations is expected to increase.

By the way, as the number of broadcasting stations increases, the problem of interference, which was not a problem in the past, becomes a serious problem.

It becomes an issue. Among them, intermodulation interference is desired.

This is an improvement because the beat with the double signal is generated and an unpleasant sound such as ``Gielji = -1, Ru'' is generated.

is desired.

Intermodulation interference is caused by two or more interfering radio waves.

It is at a frequency different from these frequencies.

It generates a spectrum similar to that of broadcast radio waves, and this is caused by the nonlinearity of the amplification element and mixing element in the receiver. Suppose you have type S personality.

I-αG+α, V+α2shi2+αsU'10-0-(1)
However, if there are two signals, fl and f2, as input signals in the above equation, then the following equation will be obtained.
nw2 Q-1-c2 (v, zirunl t+v2p
irun2tf-I-a3(Lll!Lnurl t
+v2, p13 w2t)' , , , ,
(2) However, C1. υ2 becomes the signal voltage W1 of f, , f,; 2πf+lWx; 2πf2.

When the fourth term in equation (2), that is, the fifth power term, is expanded using the trigonometric formula, -al v, v2, rtrL2π(2j', -f
2)t, ---<5)”eLI TJIU22!Ln
It includes a spectrum of 2π(2f2-f,)t, , (4). In this case, if f, -f, and 7V, the spectra of equations (3) and (4) are as shown by the broken line in Figure 1, f -1sf , f,
It occurs at +2△f. Therefore, if the receiving frequency of the receiver is tuned to f-td or f, +2Δf, if there is no signal there, a mixture of the broadcast contents of f, , f2 will be received, and f, -Δf or l,
When there is a broadcast signal at +2Δf, these false signals caused by intermodulation become an interference in receiving the broadcast signal. Even if the false signal generated by intermodulation does not have the same frequency as the desired reception frequency signal, if it is near the desired reception frequency signal, it will cause similar interference, so improvement is desired.

As a means to solve this problem, in the high frequency circuit shown in FIG. 2, the elements used in the high frequency amplification circuit 3 and the mixer circuit 6 have low nonlinearity, and the selectivity of the frequency selection circuit 2 or 4 is This is done to lower the level of interference waves input to the high frequency amplification circuit 3 and mixer circuit 6 by increasing the intermodulation interference, but this increases insertion loss and reduces practical sensitivity, so intermodulation interference cannot be satisfied. It is far from possible to improve to that level.

In FIG. 2, 1 is an antenna and 5 is a local oscillator.

In addition to the above method, there is a method of controlling the input level of the high frequency amplification circuit 6 and the mixer circuit 6 using AGC. FIG. 3 shows a block diagram of a conventional AGC circuit. The signal converted to an intermediate frequency by the mixer circuit 6 is demodulated through an intermediate frequency filter 7, an amplifier 8, and an FM detector 9. In this case, the control signal for AGC is input from the amplifier 8 to the level detector 19, and is taken out by the level detector 19 as a DC voltage according to the input signal level to control the gain of the high frequency amplification circuit 3. Ru.

However, this method is of little use against the above-mentioned interference. This is because if the reception frequency of the receiver is tuned to f and -Af in FIG. 1, this spectrum will be exactly at the intermediate frequency at the output of the mixer circuit 6, but it will cause interference waves f and f.

+d is Δf and 2Δfl! from the intermediate frequency. This is because it is difficult to obtain a sufficient AGC voltage due to the interfering radio waves, which have low frequencies and are attenuated by the intermediate frequency filter 7, causing interference. Since the band of the intermediate frequency filter 7 is determined so as not to be affected by the II contact, the AGC voltage is hardly affected by interfering radio waves, and is not useful for improving the interference caused by the above-mentioned intermodulation.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a radio receiver that can improve intermodulation interference without impairing reception characteristics during weak input, and that can provide good reception characteristics. To provide a muting device [Summary of the Invention] In order to achieve the above-mentioned object, the present invention introduces a control device having an arithmetic function such as a microcomputer to control the receiving frequency so that the broadcast radio waves drop to the desired receiving frequency. In addition to searching for and calculating the presence or absence of interference waves and their strength, the control device performs interference mitigation control in accordance with the results, and also provides means for preventing unnecessary audio from being output during the detection period for the presence or absence of interference waves. It is something that

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings. FIG. 4 is a block diagram showing one embodiment of the present invention. In FIG. 4, 1 is an antenna 12, a frequency selection circuit 13 is a high frequency amplification circuit, 4 is a frequency selection circuit 15 is a local oscillation circuit of a tuning device, 6 is a mixer circuit, 7 is an intermediate frequency filter, 8
is an intermediate frequency amplification circuit, and 9 is an FM detector.

These constitute the well-known superheterodyne receiver.

are doing. The local oscillation circuit 5, which is a channel selection device, is made of water.

A stable reference frequency fr is oscillated based on the crystal oscillator 51.

a reference signal generator 52 and a voltage controlled oscillator (VCo)
ss, a programmable divider 54 that divides the oscillation frequency f- of the CO into 1A, an output frequency fe/N of the 7'l' grammar divider, and the reference signal generator 52.
A phase comparator 55 that compares the phases of the output frequencies fr and detects the phase difference and obtains a DC voltage according to the phase difference, and a low frequency comparator that smoothes the output voltage of the phase comparator and leads it to the VCO 53. The F-wave generator 56 is generally composed of a well-known PLL circuit. Here, the frequency fτ of the reference signal generator 52 is, for example, fr = I Do KHz
If this is the case, by changing the division ratio N of the programmable divider 54, reception at every 100 KHz step becomes possible. Reference numeral 10 denotes a control device connected to the programmable divider 54 of the local oscillation circuit 5 to control the division ratio N thereof. Part 11
0 and a storage device 130. 11 is its operation keyboard. A level detector 14 is connected between the intermediate frequency amplifier 8 and the arithmetic processing unit 110 and detects when the reception level of one receiver reaches a certain level. 1
5 is a gain control device connected between the antenna 1 and the frequency selection circuit 2 of the receiver, and this device is connected to the arithmetic processing section 110.
The gain of the receiver is variably controlled by the output signal of the phase.

This is an example of interference reduction means for reducing interference between tautomers.

As the gain control device 15, as shown in FIG.
h) Show like < R other force F meme CdS 154
There is a method of controlling the current of the light emitting element 155 by using the same method, but it is not limited to these methods. Alternatively, the bias and gain of the high frequency amplifier circuit 3 may be controlled. 16 is the control device 10
is connected to the output of the arithmetic processing unit 110 of the transistor 1
61. A display device consisting of a resistor 1621 and a display element 165 is shown, which indicates that there is a broadcast with a frequency relationship that causes intermodulation interference and that the interference mitigation device according to the invention is functioning. In the embodiment shown in FIG. 4, the gain control device 15 is driven by a control signal, but it can also be driven independently from the control device 110.

FIG. 3 shows an example of a processing flow of the control device 10 when the user inputs a designation of a receiving frequency to the control device 10.

The operation of the present invention will be explained below with reference to FIGS. 4 and 3.

In FIG. 4, when a desired frequency fz is specified by operating a desired operation key on the keyboard 11, the control device 10 uses its arithmetic processing unit 110 to calculate the desired tuning control signal N0 corresponding to that frequency in step 3 of FIG. Yes ◇This value N
0 is stored in the storage unit 150C of the storage device 160 and is also input to the programmable divider 54. As a result, the local oscillation circuit 5 performs a PLL operation in a well-known manner, and the reception frequency of the receiver is set to fz. Next, the arithmetic processing unit 110 returns N in step (3) of FIG.

1 is added to , and in step (2) it is determined whether this value exceeds a numerical value corresponding to the upper limit frequency of the reception band, which is stored in advance in the storage section 130α of the storage device 160. If N0+1 is within the reception band, enter this value into the programmable divider 54 in step (3) to change the reception frequency by one step (for example, 100 KHz).
), and at this frequency, the presence or absence of the output of the level detector 14 is determined through the arithmetic processing unit 110, and if there is no broadcast to check whether or not there is a broadcast, return to step 1, add 1 again, and perform the same operation. If there is a broadcast in step 0, this value is stored in the storage unit 130d of the storage device 150,
The arithmetic processing unit 110 calculates the difference frequency (ΔN=
N-No) (this is done by subtracting the value in the storage section 130c from the value in the storage section 130d).

In step (2), a frequency (corresponding value N0+21ΔN) at which the received frequency causes intermodulation is calculated. In step 2, similarly to step 2, it is determined whether this frequency is within the reception band. If it is outside the reception band, return to step ■. If it is within the reception band in step (2), the process advances to step (2) and the presence or absence of broadcasting is determined in the same manner as in step (2). If there is no broadcast, the process returns to step (3) to continue searching for frequency-related broadcasts that cause intermodulation interference. If there is a broadcast in step (2), it means that there is a broadcast with a frequency relationship that causes intermodulation interference.In this case, in step O, the gain of the gain control device 15 is controlled to be lowered, and in step Enter N0 to complete the reception operation and receive the desired broadcast frequency fz.

If the reception band is exceeded in step ■, it means that the search up to the upper limit frequency has been completed, and the process moves to step ■, returns to the desired broadcasting frequency, and searches toward the opposite side from steps ■ to ■, that is, the lower limit frequency. . Storage device 1
The lower limit frequency of the receiving band is stored in advance in the storage unit 130h of the receiver. In FIG. 3, steps OO correspond to steps ① to ① described above, and their explanation will be omitted.

These series of operations are performed by a program 120 stored in advance. Also, the storage unit 130 of the storage device 130
The other part 130g of α~130d... is the arithmetic processing unit 1
In FIGS. 4 and 3, which are used as the working area of 10, to simplify the explanation, the case where the gain is controlled by the presence or absence of the output of the level detector 14 has been explained, but in reality, interference may become a problem. Since this is a case where the interfering radio waves are strong above a certain level, it is actually desired that the level detector 14 is made sensitive only when the input radio waves are strong above a certain level.

Further, in the embodiment shown in FIG. 4, after searching for the presence or absence of an interference signal, the gain control device 15, which is interference reduction means, is controlled by the control device 1i10, and when there is no interference signal, the gain control device 15 is controlled by the control device 1i10. If there is a jamming signal, the effect of the jamming can be improved, but during the search for the presence or absence of a jamming signal shown in steps ① to 0 in Figure 3, the receiving frequency changes from moment to moment, so it is possible to improve the effect of the jamming every time there is a broadcast signal. fragmentary F
The audio of the broadcast content is outputted from the M detector 9, resulting in harshness.

FIG. 7 shows another embodiment of the present invention in which this problem is corrected.
5 is performed more finely than in the case of FIG. 4, and unnecessary sounds are not output while searching for the presence or absence of an interfering signal.

In the seventh threshold, 141, 142, and 145 are comparators, and respective comparison levels are set by a power supply 148 and resistors 144 to 147. Reference numeral 17 indicates a muting circuit connected after the FM detector 8, and this circuit is controlled by the control device 10 so as not to output unnecessary audio during the processing period shown in FIG.

In the embodiments of FIGS. 4 and 7 described above, it is assumed that, for example, the gain of the gain control device 15 is lowered by 5'3. In this case, the input levels of high frequency amplifier circuit 5 and mixer circuit 6 are all lowered by 51B. As shown in equations (3) and (4) above, the magnitude of intermodulation interference is proportional to vl ν2 or ν1υ22, and each vI+'2 is 5.
Niji, ′ν2 or ν1v2 by being lowered by dB
' falls by 15'l'B. In other words, by lowering the input level of the desired signal by just 5 dB, the magnitude of intermodulation interference can be reduced by 1.
54B is lowered and interference is significantly improved.

In the embodiments shown in FIGS. 4 and 7, it takes time for channel selection to perform the processing shown in FIG. 5 every time a desired broadcast is received.

In order to correct this problem, for example, as shown in FIG. 7, a switch 18 for turning the control device 10 ON-OFF is provided, and when the switch 18 is turned ON and OFF, the control device 10 operates as described above. In other words, it is only necessary to perform the channel selection according to the flow shown in FIG. 3, and to set the switch 18 to 0FFt, or in some cases, to only perform the operation in (2) in FIG. 3, that is, to only receive the designated broadcasting station. The problem of tuning time can also be solved by a radio receiver having a memory preset function for broadcast stations. That is, in a radio receiver configured as shown in FIG. 4 or 5 and having a preset function, for example, when a desired reception frequency is preset (stored in the channel preset storage device 3) as shown in FIG. The necessity of gain control is determined according to the flow shown in FIG. 3, and the resultant information is stored in the storage device 130' along with the reception frequency in correspondence with each other as shown in FIG. 8. Frequency information is stored in the 0 part of the storage device 130', and gain control amount information is stored in the 0 part of the storage device 130'. The configuration may be such that the gain control device 15 is controlled based on the information. The case in Figure 8 is an example of controlling ON/OFF of gain control. For example, when 20H is selected, the frequency is 82.5 MHz, and when the gain is reduced, the frequency is 80 MHz.
．． 0 MHz, and no gain control is performed. Here, in the case where the control device 10 is configured with a microcomputer as shown in FIG. do not have.

As described above, the channel selection time can be shortened by providing the control device with a switch that cancels the flow action shown in FIG. 3 of the arithmetic processing section, or by providing the control device with a storage device that stores the contents as shown in FIG. It is possible to improve channel selection efficiency.

As can be seen from the above, according to the present invention, when there is no interfering signal, the weak signal characteristics are not impaired, and when there is an interfering signal, there are no problems caused by the IP filter in conventional AGC. Since intermodulation interference can be improved without any interference, and unnecessary audio is prevented from being output during the period of detecting the presence or absence of intermodulation interference waves, a good reception aspect can be obtained.

[Brief explanation of the drawing]

Figure 1 is a frequency spectrum diagram to explain intermodulation interference, Figure 2 is a block diagram showing the high frequency section of a radio receiver, Figure 5 is a block diagram showing the configuration of a conventional AGC circuit, and Figure 4 is A block diagram of the interference reduction device according to the present invention, FIG. 5 is a program diagram showing an overview of the processing flow of the control device in FIG. 4, FIG. 3 is a circuit diagram showing a specific example of the gain control device, and FIG. FIG. 8 is a block diagram showing another embodiment of the invention. FIG. 8 is a diagram showing the storage contents of a radio receiver having a memory preset function according to the invention. FIG. 9 is a block diagram of the memory. 5... Tuning device 10... Control device 14... Level detector 15... Interference reducing means (gain control device) 16... Display device 17... Muting circuit 18... Switch Figure 1

Claims (1)

[Scope of Claims] 1. In a radio receiver, an interference detection means for detecting the presence or absence of an interference signal, an interference reduction means for reducing interference output caused by the interference signal, and a means for muting the radio receiver. a muting circuit; and a control means for controlling the interference reducing means and the muting circuit in response to the output of the interference detecting means, and controlling the interference reducing means and detecting the interference signal when the interference signal is detected. A muting device for a radio receiver, characterized in that the muting circuit is controlled to put the radio receiver in a mute state until the interference reducing means is controlled. 2. The interference detection means includes a level detector that detects the input intensity of broadcast waves of the radio receiver, and the control means receives the output of the level detector and detects the interference in the signal path of the radio receiver. a first control circuit that controls the reducing means; a second control circuit that controls a transmitting device of the radio receiver to vary the reception frequency; and the mu a control device including a third control circuit for controlling the receiving frequency; and the control device includes a control device including a third control circuit that controls the receiving frequency, and determines whether or not there is a broadcast wave having a frequency that may interfere with the desired receiving frequency by varying the receiving frequency, and detects the level of the interfering wave. control to drive the interference reduction means to reduce the interference output when the interference signal exceeds a set level of the interference signal, and mute the muting circuit until the interference signal is detected and the interference reduction means is driven. 2. A muting device for a radio receiver according to claim 1, characterized in that the muting device is configured to control the radio receiver. 3. The control device controls the channel selection device and searches for the presence or absence of a first broadcast signal at a predetermined level within a predetermined band centered on the desired reception frequency by identifying the output of the level detector; When there is no broadcast signal other than the desired reception frequency within the predetermined band, the channel selection device is set to the desired reception frequency, and when a broadcast signal is present, the desired reception frequency is set in combination with the first broadcast signal. The second part that interferes with the frequency
When the second broadcast signal is absent or below a predetermined level, the channel selection device is set to the desired reception frequency, and when the second broadcast signal is above the predetermined level, the interference is detected. The control device is configured to reduce interference output by driving a reducing means, and eliminates unnecessary noise from the time when the control device starts at least the operation of detecting the presence or absence of an interfering signal until the broadcast of the desired reception frequency is received. 3. The muting device for a radio receiver according to claim 2, wherein the muting circuit is configured to control the muting circuit so as not to output the muting circuit.