JP3044977B2 - Diversity antenna switching control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity antenna switching control circuit, and more particularly to a diversity antenna switching control circuit suitable for switching a diversity antenna used for car radios and car televisions.

[0002]

2. Description of the Related Art Conventionally, a diversity antenna switching control circuit to which this type of antenna switching system is applied is shown in FIG. In FIG. 5, a diversity antenna switching control circuit includes an input terminal 1 for inputting an S-meter output or a detection output of a receiver, a band-pass filter (BPF) 2, a level detection circuit 3, a level comparison circuit 4, a waveform shaping circuit 5, A switching signal output circuit 6, a normal output terminal 7, and an inverted output terminal 8 are provided.

Next, the operation of the above conventional example will be described. In the diversity system of the antenna switching system (hereinafter referred to as one tuner diver), it is generally recognized that multipath interference is caused by the presence or absence and magnitude of a high-frequency noise component included in the S-meter output or the detection output, and Is switched to the other antenna.

Accordingly, in the case of the configuration shown in FIG. 4, when an output signal from the S meter or a detection output signal is input to the input terminal 1, a high-frequency noise component included in the detection signal passes through a band. The noise component extracted by the filter 2 and converted into a DC level by the level detection circuit 3. When the DC level signal is input to the level comparison circuit 4, the DC level is compared with a predetermined threshold value. When the DC level exceeds the threshold value, a comparison signal is output from the level comparison circuit 4. Is converted into a pulse signal in the waveform shaping circuit 5. When this pulse signal is input to the switching signal output circuit 6, the flip-flop in the switching signal output circuit 6 operates, and the output terminals 7,
The output value of 8 is inverted. Each of the output terminals 7 and 8 is connected to a diode switch of an antenna switching circuit, so that the antenna is switched by a signal from the output terminals 7 and 8 so that the other antenna can receive the signal. For this reason, a plurality of antennas can be switched by a single system tuner, and a diversity effect such as removal of multipath interference can be obtained.

[0005]

However, in the conventional diversity antenna switching control circuit, when the state of one antenna is determined, the state of the other antenna is not detected. When it is determined that multipath interference has been received and the antenna is switched to the other antenna, there is a possibility that the other antenna may also receive multipath interference. When such a situation occurs, the conventional system detects the multipath with both antennas, so that the antennas are continuously switched, and each time the antenna is switched, both antennas receive multipath interference. become. Therefore, there is a problem that the effect of the diversity system is reduced or rather deteriorated in the audio output.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a diversity antenna switching control circuit capable of reducing the frequency of antenna switching.

[0007]

In order to achieve the above object, the present invention provides a noise extraction means for extracting a noise component from a detection signal obtained by detecting a signal received by an antenna, and a noise extraction means. The level conversion means for converting the noise component by the extraction into a DC level, the level comparison means for comparing the output level of the level conversion means with the set value and outputting a signal corresponding to the comparison result, and the comparison result of the level comparison means. Pulse signal generating means for generating a corresponding pulse signal;
Conversion level control means for outputting a conversion level control signal corresponding to the pulse signal from the pulse signal generation means to the level conversion means, and switching signal output means for outputting an antenna switching signal in response to the pulse signal from the pulse signal generation means And a diversity antenna switching control circuit comprising:

In the diversity antenna switching control circuit, set value control means for outputting a set value control signal corresponding to the pulse signal from the pulse signal generation means to the level comparison means instead of the conversion level control means is provided. The setting value of the comparing means may be controlled.

[0009]

Therefore, according to the present invention, when a pulse signal is generated from the pulse signal generating means due to the occurrence of multipath interference, a conversion level control signal is generated in accordance with the pulse signal, and the level conversion is performed by the conversion level control signal. The conversion level of the means is controlled, equivalently increasing the set value of the level comparison means, and the switching frequency can be reduced. Further, even when the set value control signal is output to the level comparing means due to the occurrence of the multipath interference, the set value of the level comparing means is equivalently increased, and the switching frequency can be reduced. Therefore, even when both antennas are subjected to multipath interference, a lighter antenna is selected, and it is possible to reduce a decrease in the degree of effect due to continuous antenna switching.

[0010]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a diversity antenna switching control circuit includes an input terminal 1, a band-pass filter 2, a level detection circuit 3, a level comparison circuit 4, a waveform shaping circuit 5, a switching signal output circuit 6, a non-inverting output terminal 7, and an inverting terminal. Output terminal 8, AG
It comprises a C circuit 9. The input terminal 1 receives an S-meter output signal or a detection output signal of the receiver. When a signal from the input terminal 1 is input to the band-pass filter 2, only high-frequency noise components are extracted from the noise components in the detection signal. That is, the band-pass filter 2 is configured as a noise extraction unit. When the signal of the band-pass filter 2 is input to the level detection circuit 3,
It is converted to a noise component or a DC level. That is, the level detection circuit 3 is configured as level conversion means. When the DC level is input to the level comparison circuit 4, the DC level is compared with a predetermined threshold value, and the comparison result is output. That is, the level comparison circuit 4 is configured as level comparison means. When the signal from the level comparing circuit 4 is input to the waveform shaping circuit 5, the waveform shaping circuit 5 outputs a pulse signal corresponding to the comparison result from the level comparing circuit 4. That is, when the DC level exceeds the threshold value, the waveform shaping circuit 5 outputs a pulse signal. That is, the waveform shaping circuit 5 is configured as pulse signal generating means. The pulse signal from the waveform shaping circuit 5 is input to the switching signal output circuit 6 and the AGC circuit 9. When the pulse signal is input to the switching signal output circuit 6, the normal output terminal 7
And the value of the inverted output terminal 8 is inverted so that the antenna is switched. That is, the switching signal output circuit 6 is configured as switching signal output means.

On the other hand, when a pulse signal from the waveform shaping circuit 5 is input to the AGC circuit 9, the AGC circuit 9 outputs a conversion level control signal corresponding to the input pulse signal to the level detection circuit 3. I have. When this conversion level control signal is input to the level detection circuit 3, the conversion level of the level detection circuit 3 is controlled. When the conversion level of the level detection circuit 3 is controlled, the threshold value of the level comparison circuit 4 is equivalently increased, and the control is performed in a direction in which the antenna is hardly switched. . That is, the AGC circuit 9 is configured as conversion level control means.

Therefore, as shown in FIG. 3, even when multipath interference is simultaneously applied to both antennas, the conversion level of the level detection circuit 3 is controlled by the output of the AGC circuit 9 by receiving one of the antennas, and the level comparison is performed. Circuit 4
Is equivalently increased, and the antenna with the lighter degree of interference is selected from the antennas subjected to multipath interference.

Here, as the design points of the AGC circuit 9, the amount of gain to be reduced and the recovery time when the gain becomes high are important. That is, if the decrease in the gain is large,
The switching itself stops, and if it is small, there is no effect. If the return time is lengthened, the switching frequency decreases, and if it is shortened, there is no effect. Thus, these settings are determined by the tuner system, including the antenna, and field conditions.

As described above, according to this embodiment, the conversion level of the level detection circuit 3 is controlled by the signal from the AGC circuit 9, and the threshold value of the level comparison circuit 4 is equivalently increased. The frequency of antenna switching can be reduced, and the reduction in effectiveness due to continuous switching can be reduced.

FIG. 2 shows a second embodiment of the present invention. In the present embodiment, instead of inputting the output of the AGC circuit 9 to the level detection circuit 3, the output is input to the level comparison circuit 4 to control the threshold value of the level comparison circuit 4. Are the same as those in FIG. 1, and the same components are denoted by the same reference numerals and description thereof will be omitted.

In this embodiment, since the threshold value of the level comparison circuit 4 is controlled by the output signal of the AGC circuit 9, even if multi-path interference is applied to both antennas at the same time, the switching is detected. The threshold value can be increased, the frequency of antenna switching can be reduced, and the decrease in effectiveness due to continuous antenna switching can be reduced. Note that the AGC circuit 9 in this embodiment functions as a set value control unit.

As shown in FIG. 3, when the output signal of the level detection circuit 3 is input to the AGC circuit 9 and the output level of the AGC circuit 9 is controlled according to the output level of the level detection circuit 3, the level comparison circuit The threshold value of 4 can be controlled more linearly, and a fine-grained response is possible.

FIG. 4 is a timing chart of the present invention. As can be understood from FIG. 4, the introduction of the AGC circuit 9 controls the threshold value to fluctuate in accordance with the value of the multipath interference level. Even if you join,
It will be appreciated that a lighter antenna is selected to achieve an improvement.

[0020]

According to the present invention, as is apparent from the above embodiment, the conversion level of the level conversion means for converting the noise component due to multipath interference into a DC level is controlled in accordance with the interference level, or the level conversion means is controlled. Since the set value of the level comparing means for comparing the output level and the set value is controlled according to the interference level, even if both antennas are simultaneously subjected to multipath interference, the effect of continuous switching of the antennas is obtained. The decrease in degree can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a timing chart for explaining the operation of the device according to the present invention.

FIG. 5 is a block diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input terminal 2 Band-pass filter 3 Level detection circuit 4 Level comparison circuit 5 Waveform shaping circuit 6 Switching signal output circuit 7 Forward output terminal 8 Inverted output terminal 9 AGC circuit

Continuation of the front page (56) References JP-A-57-135533 (JP, A) JP-A-57-135532 (JP, A) JP-A-1-265626 (JP, A) JP-A-58-5041 (JP) JP-A-52-142915 (JP, A) JP-A-60-172452 (JP, U) JP-A-61-37641 (JP, U) JP-A-59-104647 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 7/00 H04B ⁷ /02-7/12 H04L 1/02-1/06

Claims (2)

(57) [Claims] A noise extraction means for extracting a noise component from a detection signal obtained by detecting a signal received by an antenna; a level conversion means for converting the noise component extracted by the noise extraction means into a DC level; Level comparison means for comparing the output level of the conversion means with the set value and outputting a signal corresponding to the comparison result, and pulse signal generation means for generating a pulse signal according to the comparison result of the level comparison means;
Conversion level control means for outputting a conversion level control signal corresponding to the pulse signal from the pulse signal generation means to the level conversion means, and switching signal output means for outputting an antenna switching signal in response to the pulse signal from the pulse signal generation means And a diversity antenna switching control circuit. 2. A noise extracting means for extracting a noise component from a detected signal obtained by detecting a signal received by an antenna, a level converting means for converting the noise component extracted by the noise extracting means into a DC level, Level comparing means for comparing the output level of the converting means with the set value and outputting a pulse signal according to the comparison result; pulse signal generating means for generating a pulse signal according to the comparison result of the level comparing means; Set value control means for outputting a set value control signal corresponding to the pulse signal from the generation means to the level comparison means, and switching signal output means for outputting an antenna switching signal in response to the pulse signal from the pulse signal generation means. Diversity antenna switching control circuit provided.