JPH09247064A - Fm multiplex receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an FM multiplex receiver which prevents the deterioration of an error rate owing to unnecessary switching and always switches a system to the reception of more satisfactory radio wave state when the radio wave state is deteriorated. SOLUTION: When a detection circuit 231 detects that electric field intensity detected by an electric field intensity detection circuit 21 is more than electric field intensity which is previously set, selection based on diversity in a selection circuit 20 is inhibited and a reception side is not unnecessarily switched. Then, the error rate of data in a multiplex signal which is received at present based on the switching is prevented from increasing. When electric field intensity detected by the electric field intensity detection circuit 21 is detected to be less than electric field intensity which is previously set, selection in the selection circuit 20 based on received electric field intensity is released, selection based on diversity is executed and the increase of the error rate of data in the multiplex signal owing to the deterioration of the received radio wave is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM multiplex receiver for receiving an FM multiplex broadcast signal, and more particularly to a diversity type FM multiplex receiver.

[0002]

2. Description of the Related Art In a conventional diversity type FM multiplex receiver, an electric field intensity signal detected based on an intermediate frequency signal received from each antenna and a multi-point detected from the electric field intensity signal through a band pass filter. The level of the difference signal with the path component is compared, and the receiving side is selected based on the comparison output.

[0003]

However, when the above-mentioned conventional FM multiplex receiver is used, if the other receiving state is good, the receiving state is such that no data error is included in the currently received multiplex signal. Regardless, there is a problem in that the receiving state is switched to the other receiving state, which causes a data error.

It is an object of the present invention to prevent an error rate from being deteriorated due to unnecessary switching, and to provide an FM multiplex receiver which always switches to reception of a better radio wave condition when the radio wave condition deteriorates.

[0005]

An FM multiplex receiver according to the present invention is a diversity type FM multiplex receiver which selects and receives one having a larger received electric field strength, and the electric field strength on the receiving side is set in advance. Detection means for detecting whether or not the electric field strength is equal to or higher than a set electric field strength, and prohibiting selection based on the received electric field strength when the detection means detects that the electric field strength on the receiving side is equal to or higher than a preset electric field strength. The present invention is characterized by further comprising switching control means for releasing prohibition of selection based on the received electric field strength when the detection means detects that the electric field strength on the receiving side is less than a preset electric field strength.

According to the FM multiplex receiver of the present invention,
When it is detected that the electric field strength on the receiving side is equal to or higher than the preset electric field strength, selection based on the received electric field strength is prohibited, and the electric field strength on the receiving side is less than the preset electric field strength. When it is detected, the prohibition of selection based on the received electric field strength is released. Therefore, when the electric field strength on the receiving side is equal to or higher than the preset electric field strength, selection based on diversity is prohibited. As a result, the receiving side is not unnecessarily switched, and the error rate of the data in the currently received multiplex signal based on this switching is not increased. On the contrary, when it is detected that the electric field strength on the receiving side is less than the preset electric field strength, the prohibition of the selection based on the received electric field strength is released, and the selection based on diversity is performed to The increase in the error rate of the data in the multiplexed signal due to the deterioration is suppressed.

The FM multiplex receiver according to the present invention is a diversity type FM multiplex receiver which selects and receives the one having a larger received electric field strength, and whether the electric field strength on the receiving side is equal to or higher than a preset electric field strength. First detecting means for detecting whether or not there is a second detecting means for detecting whether or not the error rate of the data multiplexed in the signal on the receiving side is equal to or more than a predetermined value, and If the electric field strength on the receiving side is equal to or higher than a preset electric field strength, the error rate of the data detected by the first detecting means and multiplexed on the receiving side signal is less than a predetermined value. It is characterized by further comprising switching control means for prohibiting the selection based on the received electric field strength only when detected by the second detecting means, and releasing the prohibition of the selection based on the received electric field strength otherwise.

According to the FM multiplex receiver of the present invention,
Selection based on diversity is prohibited only when the electric field strength on the receiving side is equal to or higher than a preset electric field strength and the error rate is less than a preset predetermined value. As a result, the receiving side is not unnecessarily switched, and the error rate of the data in the currently received multiplex signal based on this switching is maintained below a predetermined value. When it is detected that the electric field strength on the receiving side is less than a preset electric field strength and / or the error rate of the data multiplexed on the receiving side signal is equal to or more than a predetermined value, reception The prohibition of the selection based on the electric field strength is released, the selection based on the diversity is performed, and the increase in the error rate of the data in the multiplex signal due to the deterioration of the received radio wave is suppressed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An FM multiplex receiver according to the present invention will be described with reference to an embodiment. FIG. 1 is a block diagram showing the configuration of an FM multiplex receiver according to an embodiment of the present invention. The FM multiplex receiver according to the embodiment shown in FIG. 1 illustrates an FM multiplex receiver in which data such as traffic information is multiplexed.

In the FM multiplex receiver according to the embodiment of the present invention, the voltage induced by the antenna 1 is the front end 3
The signal of the desired reception frequency is supplied to and selectively amplified,
The signal of the reception frequency that has been selectively amplified is converted into an intermediate frequency based on the oscillation output of the voltage controlled oscillator that cooperates with the PLL circuit 26, and is output as an intermediate frequency signal. Similarly,
The voltage induced by the antenna 2 is supplied to the front end 4 to selectively amplify the signal of the desired reception frequency, and the signal of the reception frequency thus selectively amplified is intermediated based on the oscillation output of the voltage controlled oscillator which cooperates with the PLL circuit 26. Converted to a frequency and sent out as an intermediate frequency signal.

For the intermediate frequency signal output from the front end 3 and the intermediate frequency signal output from the front end 4, the received electric field strength is detected and the one with the larger received electric field strength is selected to select one of the intermediate frequency signals. Is supplied to the reception electric field detection circuit 10 for transmitting a switching signal for switching, and based on the switching signal from the reception electric field detection circuit 10, the intermediate frequency signal output from the front end 3 and the intermediate frequency signal output from the front end 4 And one of are selected.

The reception electric field detection circuit 10 amplifies the output signal from the front end 3 by the intermediate frequency amplifier 11, and detects the reception electric field strength from the intermediate frequency signal amplified by the intermediate frequency amplifier 11 by the reception electric field strength detection circuit 13. Then, the received electric field strength signal based on the electric field strength detected from the received electric field strength detection circuit 13 is transmitted, the received electric field strength signal is supplied to the bandpass filter 15 having a center frequency of 114 kHz, and the output signal from the bandpass filter 15 is supplied. The arithmetic circuit 17 is configured to subtract from the received electric field strength signal.

Further, the reception electric field detection circuit 10 amplifies the output signal from the front end 4 by the intermediate frequency amplifier 12, and the reception electric field strength is detected from the intermediate frequency signal amplified by the intermediate frequency amplifier 12 by the reception electric field strength detection circuit 14.
And outputs the received electric field strength signal based on the electric field strength detected by the received electric field strength detection circuit 14, supplies the received electric field strength signal to the bandpass filter 16 having a center frequency of 114 kHz, and outputs from the bandpass filter 16. The arithmetic circuit 18 subtracts the signal from the received electric field strength signal, and the subtraction output signal from the arithmetic circuit 17 and the subtraction output signal from the arithmetic circuit 18 are supplied to the comparator 19 for level comparison, and received based on the level comparison output. It is configured to supply a switching signal for instructing switching to a side having a larger electric field strength to a control circuit 23 described later.

One of the intermediate frequency signal output from the front end 3 and the intermediate frequency signal output from the front end 4 is selected by the selection circuit 20 based on the selection signal from the control circuit 23. An intermediate frequency signal amplification / FM detection circuit (I
The intermediate frequency signal selected by the selection circuit 20 is supplied to the F / DET) 5, amplified and FM-detected.
The FM detection output is supplied to the stereo demodulation circuit 6, stereo demodulated and separated into left and right audio signals, and the separated left audio signal and right audio signal are respectively low frequency amplifiers 7a and 7b.
In (1), the left audio signal and the right audio signal, which are individually amplified, are supplied to the speakers 8a, 8b and reproduced as audio separately.

The intermediate frequency signal amplified by the intermediate frequency signal amplification / FM detection circuit 5 is supplied to the electric field strength detection circuit 21 and the electric field strength based on the intermediate frequency signal selected by the selection circuit 20 is detected. An electric field strength signal based on the detected electric field strength is supplied to the control circuit 23. The FM detection output of the intermediate frequency signal amplification / FM detection circuit 5 is supplied to a decoder 22 equipped with a bandpass filter / LMSK demodulation / error correction circuit, and is multiplexed into an FM stereo signal from the FM stereo signal in the decoder 22. The traffic information data is extracted, the extracted traffic information data is LMSK demodulated, error detection and error correction are performed in the LMSK demodulated data, and the control circuit 2
3 is supplied.

The control circuit 23 receives a signal based on the operation key from the operation key group 24, sends a frequency division ratio signal based on the reception frequency to the PLL circuit 26 to set the reception frequency, and outputs the decoded output from the decoder 22. Upon receipt, the display 25 is caused to display the decoded output based on the operation keys from the operation key group 24.

Further, the control circuit 23 includes a decoder 22.
The error counter 232 that receives an uncorrectable error signal being output from the device and counts the error signal over a predetermined period as an error rate, and the electric field strength based on the electric field strength signal output from the electric field strength detection circuit 21 And a detection circuit 231 for detecting whether or not the error rate is less than or equal to a predetermined value set in advance and detecting whether the error rate is less than a predetermined value set in advance.

Furthermore, the electric field strength based on the electric field strength signal output from the electric field strength detection circuit 21 is preset in the control circuit 23 in response to the comparison output from the comparator 19 and the output from the detection circuit 231. When the error rate is greater than or equal to the predetermined value and less than the predetermined value set in advance, switching by the selection circuit 20 to the output on the front end side having the larger received electric field strength signal based on the switching signal from the comparator 19 is performed. In other cases, the prohibition of switching to the output on the front end side of the larger received electric field strength signal based on the switching signal from the comparator 19 is released, and the received electric field strength signal based on the switching signal from the comparator 19 is released. For switching the output on the front end side of the larger one by the selection circuit 20 And a control circuit 233.

The operation of the FM multiplex receiver according to the present embodiment configured as described above will be described.

The reception signal from the antenna 1 is selectively amplified and frequency-converted in the front end 3, and the frequency-converted intermediate frequency signal is sent to the selection circuit 20.
The reception signal from the antenna 2 is selectively amplified and frequency-converted in the front end 4, and the frequency-converted intermediate frequency signal is sent to the selection circuit 20 to select one of them.

The intermediate frequency signal output from the front end 3 is amplified in the intermediate frequency amplifier circuit 11, the received electric field strength is detected in the received electric field strength detection circuit 13, and the received electric field strength signal passes through the band pass filter 15. The signal from the multipath is extracted, and the signal that has passed through the bandpass filter 15 is calculated from the received electric field strength signal by the calculator
And the subtraction output signal is sent from the arithmetic unit 17. This signal is a received electric field strength signal from which the influence of multipath is removed.

Similarly, the intermediate frequency signal output from the front end 4 is amplified by the intermediate frequency amplifier circuit 12 and the received electric field strength is detected by the received electric field strength detection circuit 14. The received electric field strength signal is the band pass filter 16
The signal that has passed through the bandpass filter is extracted, the signal that has passed through the bandpass filter 15 is subtracted from the received electric field intensity signal in the calculator 17, and the subtraction output signal is sent from the calculator 17. This signal is a received electric field strength signal from which the influence of multipath is removed.

The subtracted signals output from the arithmetic circuits 17 and 18, that is, the received electric field strength signal, are compared by the comparator 19.
Then, the levels are compared with each other, and a switching signal for instructing switching to the side having the higher level of the received electric field strength is sent to the control circuit 23.

On the other hand, the intermediate frequency signal selected by the selection circuit 20 is amplified by the intermediate frequency signal amplification / FM detection circuit 5, FM detected, and the FM detection output is stereo demodulated by the stereo demodulation circuit 6. The left and right audio signals that have been demodulated in stereo and separated are low-frequency amplifier 7a,
It is amplified in 7b and reproduced as sound in the speakers 8a and 8b.

The intermediate frequency signal selected by the selection circuit 20 and amplified by the intermediate frequency signal amplification / FM detection circuit 5 has its electric field strength detected by the electric field strength detection circuit 21, and the electric field based on the electric field strength. The intensity signal is sent to the control circuit 23. Intermediate frequency signal amplification / F
The FM detection output detected by the M detection circuit 5 is supplied to the decoder 22, the traffic information data multiplexed in the FM stereo signal is extracted, the extracted traffic information data is LMSK demodulated, and the LMSK demodulated data is included. Is detected and corrected, and is sent to the control circuit 23.

Upon receiving the uncorrectable error signal being output from the decoder 22, the error signal over a predetermined period is counted by the error counter 232, and the count value of the error counter 232 during the predetermined period,
That is, the error rate is detected. On the other hand, it is determined whether the electric field strength based on the electric field strength signal sent from the electric field strength detection circuit 21 is equal to or higher than a preset electric field strength and whether the error rate is less than a preset predetermined value.
Detected in.

Based on the detection output from the detection circuit 231,
When the electric field intensity detected by the electric field intensity detection circuit 21 is equal to or higher than the preset electric field intensity and the error rate is less than the preset predetermined value, the selection circuit 20 selects the signal based on the switching signal output from the comparator 19. It is prohibited under the control of the switching control circuit 233, and the state in which the intermediate frequency signal output from the front end selected before is kept selected is continued.

In other states, that is, when the electric field intensity detected by the electric field intensity detection circuit 21 is less than a preset electric field intensity and / or the error rate is equal to or more than a preset predetermined value, the switching is performed. Under the control of the control circuit 233, the prohibition of the selection in the selection circuit 20 by the switching signal output from the comparator 19 is released, and the intermediate frequency output from the front end by the selection signal based on the switching signal from the comparator 19 is released. The signal is selected in the selection circuit 20,
It is transmitted via the selection circuit 20.

Therefore, even if the received electric field strength of the other side becomes larger than the received electric field strength of the currently selected side,
When the electric field strength on the currently selected side is equal to or higher than the preset electric field strength and the error rate is less than the set predetermined value, switching of the intermediate frequency signal is not performed, and deterioration of the error rate due to unnecessary switching is prevented. As a result, the rate at which reception with a low error rate can be performed increases.

Further, when the radio wave condition deteriorates and the electric field strength of the currently selected side becomes less than the preset electric field strength and / or the error rate reaches or exceeds a preset predetermined value, reception is performed. The switching to the intermediate frequency signal having the larger electric field strength is performed, and the switching is made to the one having the larger reception electric field strength.

Further, in the FM multiplex receiver according to the above-described embodiment, the intermediate frequency signals amplified by the intermediate frequency amplifying circuits 11 and 12 instead of the outputs from the front ends 3 and 4 are selected as intermediate signals. A frequency signal is supplied to the selection circuit 20, and an FM detection circuit is used in place of the intermediate frequency signal amplification / FM detection circuit 5 to replace the amplified intermediate frequency signal output from the intermediate frequency signal amplification / FM detection circuit 5. The intermediate frequency signal output from the selection circuit 20 may be supplied to the electric field strength detection circuit 21 to detect the electric field strength.

In the FM multiplex receiver according to the above-described embodiment, whether or not the error rate is less than a predetermined error rate set in advance also determines whether or not selection by the selection circuit 20 is prohibited. Although the case of using as an element of
Only the output of the electric field strength detection circuit 21 selects the selection circuit 20.
It may be possible to determine whether or not the selection in step 1 is prohibited, and even in this case, a considerable effect can be obtained.

[0033]

As described above, the FM according to the present invention
According to the multiplex receiver, when the electric field strength on the currently selected side is detected to be equal to or higher than the preset electric field strength, deterioration of the error rate due to unnecessary switching on the receiving side is prevented, and the error rate is small. It is possible to obtain the effect of increasing the ratio of reception. Also, when the radio wave condition is deteriorated such that the electric field strength on the currently selected side is less than the preset electric field strength, it is switched to the one with the larger received electric field strength, which causes deterioration of the radio wave condition. It also has the effect of suppressing an increase in the error rate.

Further, according to the FM multiplex receiver of the present invention, the electric field strength on the currently selected side is detected to be equal to or higher than the preset electric field strength, and the error rate is detected to be less than the preset value. When this occurs, the effect that the deterioration of the error rate due to unnecessary switching on the receiving side is prevented and the rate at which reception with a low error rate can be performed increases is obtained.
When the radio wave condition deteriorates and the electric field strength on the currently selected side is less than the preset electric field strength and / or the error rate reaches a preset value or more, the received electric field strength is set to the larger one. By switching, the increase in the error rate due to the deterioration of the radio wave state can be suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an FM multiplex receiver according to an embodiment of the present invention.

[Explanation of symbols]

 1 and 2 antennas 3 and 4 front end 5 intermediate frequency signal amplification / FM detection circuit 10 reception electric field detection circuit 11 and 12 intermediate frequency amplification circuit 13 and 14 reception electric field strength detection circuit 15 and 16 band pass filter 17 and 18 arithmetic circuit 19 Comparator 20 Selection circuit 21 Electric field intensity detection circuit 22 Decoder 23 Control circuit 231 Detection circuit 232 Error counter 233 Switching control circuit

Claims (2)

[Claims] 1. A detection means for detecting whether or not the electric field strength on the receiving side is equal to or higher than a preset electric field strength in a diversity type FM multiplex receiver which selects and receives one having a larger received electric field strength. When the detection means detects that the electric field strength on the receiving side is equal to or higher than a preset electric field strength, the selection based on the received electric field strength is prohibited, and the electric field strength on the receiving side is a preset electric field strength. An FM multiplex receiver comprising switching control means for canceling prohibition of selection based on the received electric field strength when the detection means detects that the intensity is less than the strength. 2. A diversity-type FM multiplex receiver that selects and receives one having a larger received electric field strength, and detects whether the electric field strength on the receiving side is equal to or higher than a preset electric field strength. Detecting means, second detecting means for detecting whether or not the error rate of the data multiplexed in the signal on the receiving side is a predetermined value or more, and the electric field strength on the receiving side is preset. It is detected by the second detecting means that the error rate of the data which is detected by the first detecting means when it is equal to or higher than the electric field strength and which is multiplexed in the signal on the receiving side is less than a predetermined value. An FM multiplex receiver comprising a switching control means for prohibiting the selection based on the received electric field strength only when the above, and canceling the prohibition of the selection based on the received electric field strength during the other cases.