JPH09139700A - Diversity receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reading rate of an FM multiplex data signal by a mobile object. SOLUTION: In this receiver, a band pass filter 14 extracts a digital signal component from an FM multiplex broadcast signal demodulated by an FM tuner 13 and an MSK demodulator 15 applies MSK demodulation to the digital signal component to obtain the original data signal. Then a synchronization recovery section 17 applies synchronization recovery to the data signal subject to MSK demodulation. When the synchronization recovery section 17 is unable to conduct synchronization recovery, a synchronization defect signal is outputted and an error correction section 18 outputs a data error amount and an antenna switching discrimination section 19 compares the data error amount with a prescribed value and outputs an antenna switching signal when the data error amount is a prescribed value or over, and an antenna changeover operating section 20 receiving the synchronization defect signal or the antenna switching signal to allow an antenna changeover circuit 12 to conduct switching to select either of antennas 11a, 11b whose reception state is optimum and to allow the selected antenna to receive the FM multiplex broadcast radio wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiver for receiving FM multiplex broadcast waves and effectively reproducing FM multiplex data signals.

[0002]

2. Description of the Related Art Conventionally, as a diversity receiving device which is mounted on a moving body and used for receiving and demodulating FM broadcast radio waves, there is a diversity receiving device described in Japanese Patent Publication No. 3-6701. As shown in FIG. 2, this conventional diversity receiver includes an antenna switching circuit 2 for switching connection with any one of a plurality of antennas 1a and 1b to take in FM broadcast radio waves, and an FM switching circuit.
The tuner 3 for demodulating a broadcast signal, the intermediate frequency amplifier circuit 4 provided in the FM tuner 3 for detecting the reception state of the selected antenna, and the intermediate frequency signal output by the intermediate frequency amplifier circuit 4 On the other hand, a distortion component detection circuit 5 for detecting a distortion component, a limiter circuit 6 for level-limiting the electric field strength signal output by the intermediate frequency amplification circuit 4, and a distortion component and an electric field strength signal output by the distortion component detection circuit 5. The antenna switching determination circuit 7 is configured to perform switching determination of the antennas 1a and 1b based on the size and operate the antenna switching circuit 2.

In this conventional diversity receiver circuit, F
While the FM tuner 3 demodulates the FM broadcast signal and outputs it to the audio circuit for reproduction, the antenna switching determination circuit 7
Then, based on the distortion component detected by the distortion component detection circuit 5 with respect to the intermediate frequency signal amplified by the intermediate frequency amplification circuit 4 in the FM tuner 3 and the electric field strength signal from the limiter circuit 6, a predetermined electric field strength or more is obtained. Then, the antenna with the smaller distortion component is selected to operate the antenna switching circuit 2, and the antenna with the better reception state is always used to receive, demodulate, and reproduce the FM broadcast wave.

On the other hand, as a receiving apparatus for FM multiplex broadcasting in which digital data signals are multiplexed and transmitted by utilizing the gap of FM broadcasting, an FM multiplex broadcasting receiving apparatus developed especially for mobile bodies such as automobiles is called "broadcasting". Technology "1994
It is disclosed in an article entitled "Outline of FM character multiplex broadcasting LSI" on and after page 79 of the July issue of the year. This conventional FM multiplex broadcast receiving apparatus has a configuration as shown in FIG. 3, and includes an FM tuner 3 ′ for demodulating an FM multiplex broadcast signal received by the antenna 1 and an FM multiplex broadcast signal demodulated by the FM tuner 3 ′. A bandpass filter 8 for extracting only the digital signal component multiplexed therein, an MSK demodulation circuit 9 for performing MSK demodulation of the extracted digital signal component,
The MSK demodulation circuit 9 is composed of an error correction circuit 10 that performs error correction on a data signal in a state before being demodulated and multiplexed.

In this conventional FM multiplex broadcast receiving apparatus, the FM multiplex broadcast signal received by the antenna 1 and demodulated by the FM tuner 3'is frequency-division-multiplexed with the FM multiplex broadcast signal. The signal is extracted by the bandpass filter 8 and MSK
The demodulation circuit 9 performs MSK demodulation, the data signal before multiplexing is taken out, the error correction circuit 10 performs error correction, and the data signal is output to a subsequent data signal processing circuit (not shown).

[0006]

However, in the conventional FM multiplex broadcast receiving apparatus as described above, the FM multiplex digital signal is received together with the FM audio signal by one FM tuner, and only the FM multiplex digital signal is extracted and demodulated. With this configuration, it is not possible to receive and demodulate a multiplex broadcast in a frequency band different from that of the FM audio signal. Therefore, for example, as a receiving device that receives and demodulates only FM multiplex signals in order to use the level 3 traffic information in a car navigation system, a configuration as shown in FIG. 4 can be considered. This conceivable receiving device has a structure in which the diversity receiving device shown in FIG. 2 and the FM multiplex broadcasting receiving device shown in FIG.
Antenna switching circuit 2 for switching connection with either a or 1b
, An FM tuner 3 ″ different from the FM tuner for receiving the audio signal, a distortion component detection circuit 5 for extracting an electric field strength signal from the FM tuner 3 ″ and detecting a distortion component, and a level limit for the electric field strength signal. Switching limit of the antennas 1a and 1b is determined based on the limiter circuit 6 to be applied, the distortion component output from the distortion component detection circuit 5, and the magnitude of the electric field strength signal.
An antenna switching determination circuit 7 for operating the antenna switching circuit 2 is provided, and at the same time, a bandpass filter 8 for extracting a digital signal component from the FM multiplex signal demodulated by the FM tuner 3 ″, and an MS of the extracted digital signal component.
The configuration includes an MSK demodulation circuit 9 that performs K demodulation, and an error correction circuit 10 that performs error correction on the data signal demodulated by the MSK demodulation circuit 9.

In this diversity FM receiver, the electric field strength signal is taken out from the FM tuner 3 ", the distortion component is detected by the distortion component detection circuit 5, and the antenna switching judgment circuit 7 outputs the electric field strength signal output from the limiter circuit 6. Based on the distortion component, the antenna having the smaller distortion component at a predetermined electric field strength or more is selected and the antenna switching circuit 2 is operated, and the antenna having the better reception state is always used for FM.
The multiple signal is received, and the digital signal demodulation system demodulates the signal received by the antenna with the better reception condition.

However, in the diversity receiving apparatus having such a configuration, the F multiplexed digital signal is received from the FM multiplexed signals and the F signal is demodulated while demodulating the data signal.
When the M audio signal is distorted, the antenna may be compulsorily switched on the data signal side even if the data signal side can be sufficiently used, which causes a problem that the demodulated data signal is disturbed.

The present invention has been invented based on such a consideration, and in a receiver of an FM multiplex broadcasting signal, switching control of the diversity antenna is performed according to the state of the demodulated data signal on the FM multiplex digital signal side. It is an object of the present invention to provide a diversity receiving apparatus capable of increasing the reading rate of FM multiplex data signals.

[0010]

A diversity receiving apparatus of the present invention is capable of switching connection with any one of a plurality of antennas and connecting the F
An antenna switching circuit that takes in M multiplex broadcasting radio waves, an FM tuner that demodulates the FM multiplex broadcasting radio waves that are taken in through the antenna switching circuit, and a band that extracts digital signal components from the FM multiplex broadcasting signals demodulated by the FM tuner. Pass filter and MSK for MSK demodulating the digital signal component extracted by the band pass filter
A demodulator, a synchronous reproduction unit that performs synchronous reproduction on the digital signal component demodulated by the MSK demodulator, and outputs a synchronization failure signal when synchronous reproduction cannot be performed, and a data signal on which the synchronous reproduction unit performs synchronous reproduction. Error correction unit for outputting the demodulated data and outputting the data error amount, and comparing the data error amount from the error correction unit with a predetermined value, there is a data error amount equal to or more than the predetermined value. An antenna switching determination unit that sometimes performs antenna switching determination, and an antenna switching operation unit that causes the antenna switching circuit to perform switching operation when the synchronization failure signal or the antenna switching determination signal is output.

In the diversity receiver of this invention,
FM from any one of the multiple antennas selected
The multiplex broadcast wave is taken in and the FM multiplex broadcast signal is demodulated by the FM tuner. FM demodulated by this FM tuner
A bandpass filter extracts a digital signal component from the multiplex broadcast signal, and an MSK demodulator MSK demodulates the digital signal component into an original data signal. Then, the synchronous reproduction unit performs synchronous reproduction on the MSK-demodulated data signal, the error correction unit performs error correction on the data signal, and outputs the data signal to the subsequent data signal processing circuit.

At the same time, when the synchronous reproducing section cannot perform synchronous reproduction, a sync failure signal is output, and the error correcting section outputs a data error amount indicating how many bits are in error in one frame of data, and the antenna switching judging section outputs this. The data error amount is compared with a predetermined value, and when the data error amount is equal to or larger than the predetermined value, an antenna switching signal is output. Therefore, the antenna switching operation unit causes the antenna switching circuit to perform the switching operation when the synchronization failure signal or the antenna switching signal is input, and switches to the antenna having the optimum reception state to capture the FM multiplex broadcast wave. .

As a result, the switching control of the antenna is controlled by looking at the reception state of the FM multiplex data signal side rather than the reception state of the FM audio signal of the FM multiplex broadcast signal, and the read rate of the FM multiplex data signal is improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a circuit configuration of a diversity receiving apparatus according to an embodiment of the present invention. Diversity antennas 11a and 11b and an antenna switching circuit 1 for connecting to any one of them to take in an FM multiplex broadcast wave.
2, an FM tuner 13 for demodulating the fetched FM multiplex broadcast signal, a bandpass filter 14 for extracting the FM multiplex digital signal from the FM multiplex signal demodulated by the FM tuner 13, and an MSK demodulation of the FM multiplex digital signal. MSK demodulation circuit 1 for extracting the original data signal before multiplexing
5 and an error correction circuit 16 for performing error correction on the data signal and outputting the demodulated data signal to the subsequent data signal processing circuit (not shown).

The error correction circuit 16 has a data signal of 1
Synchronous reproduction is performed in order to read the beginning of the data of the frame, and a synchronous reproduction unit 17 that outputs a synchronization failure signal when the synchronization cannot be obtained, and error correction of the synchronously reproduced data are performed. An error correction unit 18 that outputs a data error amount that indicates whether there is error data is provided.

The diversity receiver of this embodiment further monitors the data error amount performed by the error correction section 18,
An antenna switching determination circuit 19 that outputs an antenna switching signal as a sensitivity failure when the value exceeds a predetermined value, and a synchronization failure signal or antenna switching determination circuit 19 from the sync reproducing unit 17.
An OR circuit 20 which receives the antenna switching signal from the antenna switching circuit 12 and gives a final antenna switching command to the antenna switching circuit 12 is provided.

Next, the operation of the diversity receiving apparatus having the above configuration will be described. If the antenna 11a side is now connected to the FM tuner 13 by the antenna switching circuit 12, the FM multiplex broadcast wave received by the antenna 11a passes through the antenna switching circuit 12 and the FM tuner 13 is transmitted.
, FM demodulated here, and output as an FM composite signal.

The band-pass filter 14 extracts the FM multiplex digital signal component contained in this FM composite signal, MSK demodulates it in the MSK demodulation circuit 15 and demodulates it into a data signal before multiplexing. Then, this data signal is error-corrected in the error correction circuit 16 and sent to the subsequent data processing circuit (not shown).

In the data error correction of the error correction circuit 16,
The synchronous reproduction unit 17 performs synchronous reproduction for reading the beginning of one frame of data, and when synchronization cannot be achieved here, a synchronization failure signal is output to the OR circuit 20. on the other hand,
The synchronously reproduced data is error-corrected by the error correction unit 18. At this time, the error correction unit 18 outputs a data error amount indicating how many bits of error data are contained in one frame to the antenna switching determination circuit 19, The antenna switching determination circuit 19 outputs an antenna switching signal to the OR circuit 20 when the data error amount exceeds a predetermined value. When the synchronization failure signal or the antenna switching signal is input, the final antenna switching signal is output from the OR circuit 20 to the antenna switching circuit 12, and the diversity antenna 11a is switched to the diversity antenna 11b.

[0020]

As described above, according to the present invention, the antenna is used when the FM multiplex data signal demodulated from the received FM multiplex broadcast signal has poor synchronization or has a data error amount of a predetermined value or more. Since I tried to switch, FM
Unlike the conventional receiving device that switches the antenna in the receiving state of the audio signal, the reading rate of the FM multiplex data can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of one embodiment of the present invention.

FIG. 2 is a circuit block diagram of a conventional diversity receiver.

FIG. 3 is a circuit block diagram of a conventional FM multiplex broadcast receiver.

FIG. 4 is a circuit block diagram of a proposed diversity receiver.

[Explanation of symbols]

 11a, 11b antenna 12 antenna switching circuit 13 FM tuner 14 bandpass filter 15 MSK demodulation circuit 16 error correction circuit 17 synchronization reproduction unit 18 error correction unit 19 antenna switching determination circuit 20 OR circuit

Claims (1)

[Claims] 1. An antenna switching circuit for switching and connecting with any one of a plurality of antennas to take in an FM multiplex broadcasting wave, an FM tuner for demodulating an FM multiplex broadcasting wave taken in through the antenna switching circuit, and the FM. A bandpass filter for extracting a digital signal component from the FM multiplex broadcast signal demodulated by the tuner, an MSK demodulator for MSK demodulating the digital signal component extracted by the bandpass filter, and a digital signal component demodulated by the MSK demodulator. In addition to performing synchronous reproduction, a synchronous reproduction unit that outputs a synchronization failure signal when synchronous reproduction cannot be performed, and the synchronous reproduction unit performs error correction on the data signal that has been synchronously reproduced and outputs demodulated data, and also outputs data. An error correction unit that outputs an error amount, and compares the data error amount from the error correction unit with a predetermined value. Compare
An antenna switching determination unit that performs antenna switching determination when there is a data error amount of a predetermined value or more, and an antenna switching operation unit that causes the antenna switching circuit to perform switching operation when outputting the synchronization failure signal or the antenna switching determination signal. A diversity receiver comprising: