JPH10150426A - FM multiplexing data generator - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an FM multiplexing data generating device capable of realizing encoding and modulation with a small-scale device and minimizing a data error rate in a transmission process and an arithmetic process. The challenge is to do. A data creation unit for creating data including at least characters to be multiplexed in a vacant frequency band of FM broadcast, an audio signal generation unit for generating an audio signal, and a data creation unit
A signal processing unit 14 that captures each output of the audio signal generation unit 12, adds additional information for performing error correction on the data, and modulates the data based on the output of the audio signal generation unit 12, The output of the signal processing unit 14 and the output of the audio signal generation unit 12 are multiplexed into independent frequency bands,
A transmitting unit 15 for transmitting the multiplexed signal to the receiving side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the error rate of FM multiplexing data such as characters and figures, and multiplexes the FM multiplexing data into a frequency band independent of a voice signal. FM multiplexing data generator.

[0002]

2. Description of the Related Art In current FM multiplex broadcasting, a digital signal is frequency-division multiplexed in addition to the stereo sound signal of the current FM broadcasting to newly provide text, graphics, audio information and the like. In this FM multiplex broadcasting, various kinds of information are multiplexed on existing broadcasting waves. (1) FM multiplex broadcasting can be easily put into practical use simply by adding a multiplex signal modulator to existing FM broadcasting equipment. .

(2) An existing FM broadcast network can be used. (3) A service area as large as FM stereo broadcasting can be expected. (4) The frequency can be used effectively. There are many advantages.

In recent years, demand for data services for mobiles has increased, and in particular, as a data broadcast capable of providing real-time traffic information to automobiles, a relatively large-capacity and sufficiently reliable FM for mobile reception has been developed. Multiplex broadcasting is being developed.

FIG. 4 shows a frame configuration of FM multiplex broadcasting. In FIG. 4, one frame is composed of 272 blocks, of which 190 blocks are an information part and a CRC.
(Cycle Redundancy Check Character) code part, remaining 8
Two blocks are a column parity section and a row parity section for transmitting vertical and horizontal parity bits. A 16-bit block identification code is added to the head of each block in the horizontal direction.

Here, in the FM multiplex broadcasting, a coding device for performing error correction, a modulation device for performing modulation, and the like are provided integrally with the data generating device. Then, in order to perform error correction on the 272 blocks of data on the data creation device side, the BEST method, which is a characteristic superior to a convolutional code having a coding rate of 50%, is employed. It is doubled in the horizontal direction.

[0007] However, since the above-mentioned data producing apparatus performs powerful error correction such that data is subjected to double BEST, the data amount becomes large. Then, it is necessary to increase the scale of the data creation device due to the problem of the data processing capacity. Further, in order to reduce the data error rate, it is only necessary to reduce the amount of data sent to the encoding device, but it is difficult.

[0008]

As described above, in the conventional data generator for FM multiplexing, the amount of data increases when error correction is performed. However, there is a problem that a separate apparatus is required.

An object of the present invention is to provide an FM multiplexing data generator capable of realizing encoding and modulation with a small-scale device and minimizing a data error rate in a transmission process and an arithmetic process. .

[0010]

An FM multiplexing data generating apparatus according to the present invention comprises: a data generating section for generating data including at least characters to be multiplexed in a vacant frequency band of an FM broadcast; and an audio signal for generating an audio signal. The output of the generator, the data generator, and the audio signal generator are taken in, an error correction code for performing error correction is added to the data, and the data is modulated based on the output of the audio signal generator. It comprises a signal processing unit, and a transmission unit that multiplexes the output of the signal processing unit and the output of the audio signal generation unit into mutually independent frequency bands and transmits the multiplexed signal to the receiving side.

According to this configuration, a small-scale data generating unit can be used, and furthermore, the signal processing unit can execute an arithmetic process independent of other circuits in real time. Thus, data can be transmitted with a small amount of data, and the error rate of data in the transmission process and the calculation process can be minimized.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an overall configuration of an FM multiplexing data generator according to an embodiment of the present invention.

This FM multiplexing data generating apparatus is roughly composed of a data creating section 11, an audio signal processing section 12, a data IF (interface) section 13, a signal processing section 14, and a transmission section 15. Among them, the transmission unit 15
Is a multiplexing circuit 151 and a mixer 15 forming a modulation circuit.
2 and a local oscillator 153.

The multiplexed data generated from the data creating unit 11 is supplied to one input terminal of a multiplexing circuit 151 in a transmitting unit 15 via a data IF unit 13 and a signal processing unit 14. The audio signal output from the audio signal processing unit 12 is supplied to the other input terminal of the multiplexing circuit 151. The multiplexing circuit 151 multiplexes the multiplexed data and the audio signal, and outputs the multiplexed data and the audio signal to the mixer 152. Mixer 152
Modulates by mixing the output of the multiplexing circuit 151 with the local oscillation signal output from the local oscillator 153,
Transmit via antenna.

The audio signal processing unit 12 has a frequency of 19 kHz.
Are output to the data IF unit 13. FIG. 2 shows an internal configuration of the data IF unit 13 and the signal processing unit 14.

The data IF unit 13 is a CPU (Central Processing Unit) 13 that receives multiplexed data by serial communication.
a, clock extraction circuit 13b, LR level detection circuit 1
3c, A / D (Analog / Digital) converter 13d and D / A
(Digital / Analog) converter 13e. The signal processing unit 14 includes an encoding circuit 14a, a level control circuit 1
4b and LMSK (Level Controlled Minimum Shift Key)
ing) It is composed of a modulation circuit 14c. The encoding circuit 14a, the level control circuit 14b, and the LMSK modulation circuit 14c are provided with a high-speed 32-bit floating point arithmetic DSP (D
digital signal Processor) to execute the respective processes.

The data output from the data generator 11 is in a low-rate format shown in FIG.
nal Computer) at 19.2 kbps. At this time, the communication protocol is simplified as much as possible. The data shown in FIG. 3 corresponds to the information section shown in FIG.

The CPU 13a receives the input multiplexed data by serial communication. The data received by the CPU 13a is asynchronously encoded by the encoding circuit 14a in the signal processing unit 14.
Is transferred to the SIO (Serial Input Output) on the input side. At this time, the encoding circuit 14a is designed so that the processing buffer is a double buffer, and when one is full of processing, the other accesses the CPU 13a.

The encoding circuit 14a encodes the data output from the CPU 13a, and
3c is output to one input terminal. Further, the encoding circuit 14a performs arithmetic processing such as error correction on the data output from the CPU 13a, and adds a CRC code and a parity part for performing error correction to form a form as shown in FIG. . Also, the encoding circuit 14a
Performs BEST addition, transmission scrambling, and the like on data.

The 19 kHz pilot signal output from the audio signal processing unit 12 is supplied to a clock extraction circuit 13b.
Supplied to The clock extraction circuit 13b has a frequency of 19 kHz
The synchronous clock is extracted from the pilot signal, and the synchronous clock is output to the control terminal of the A / D converter 13d.

Further, the analog audio signals Lch and Rch output from the audio signal processing section 12 are supplied to an LR level detection circuit 13c. LR level detection circuit 13
c generates an LR difference signal from the analog audio signals Lch and Rch, detects an amplitude level of the LR difference signal, and calculates a modulation degree from a multilevel control characteristic according to a standard. The output of the LR level detection circuit 13c is digitized by an A / D converter 13d operated by the synchronous clock from the clock extraction circuit 11b, and supplied to the level control circuit 14b of the signal processing unit 14.

The level control circuit 14b includes the A / D converter 1
Based on the output of 3d, the superimposing level on the output data of the encoding circuit 14a is controlled and output to the other input terminal of the LMSK modulation circuit 14c.

The LMSK modulation circuit 14c includes the encoding circuit 1
The data sequence encoded by 4a is subjected to phase control and the like, and MSK modulation is performed according to the superimposed level from the level control circuit 14b. This MSK modulation is calculated in advance, and an R (not shown) built in the LMSK modulation circuit 14c is used.
This is performed by calling the space frequency and mark frequency of 0 and 180 degrees stored in the OM (Read Only Memory). The carrier level of the MSK signal is L
-Control is performed according to the amplitude level of the R difference signal.

The data multiplexed signal output from the LMSK modulation circuit 14c is supplied to the D / A converter 13 of the data IF unit 13.
The signal is converted into an analog signal by e, and output to the transmitting unit 15. As described above, according to the above embodiment, the encoding circuit 14
Since the a and the LMSK modulation circuit 14c are provided separately from the data creation unit 11, the data creation unit 11 can be realized by a small-scale device such as a personal computer.

Since the signal processing unit 14 has a function of encoding and modulating in real time, the data creation unit 11
Thus, it is possible to transmit a relatively small amount of information at a low rate. Therefore, the data creation unit 11 may be at the PC level, and the transmission means and protocol may be simple.

Furthermore, since the encoding circuit 14a and the LMSK modulation circuit 14c are incorporated into one signal processing unit 14 to form a unit, and the signal processing unit 14 performs processing independent of the data generation unit 11. By reducing the number of parts and the number of bits, it is possible to execute arithmetic processing in error correction.

The data creating section 11 can reduce the amount of data to be transferred by about 60%. It should be noted that the present invention is not limited to the above-described embodiment, and can be practiced without departing from the scope of the present invention.

[0028]

As described in detail above, according to the present invention,
It is possible to provide an FM multiplexing data generation device that can realize encoding and modulation with a small-scale device and minimize the data error rate in a transmission process and an arithmetic process.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an FM multiplexing data generator according to the present invention.

FIG. 2 is a block diagram showing a specific configuration of a data IF unit and a signal processing unit in the embodiment.

FIG. 3 is an exemplary view for explaining a form of data transmitted to a data IF unit in the embodiment.

FIG. 4 is a view for explaining a conventional data form.

[Explanation of symbols]

 11: Data creation unit, 12: Audio signal processing unit, 13: Data IF unit, 14: Signal processing unit, 14a: Encoding circuit, 14c: LMSK modulation circuit, 15: Transmission unit

Claims (3)

[Claims] 1. A data generator for generating data including at least characters to be multiplexed in a vacant frequency band of an FM broadcast; an audio signal generator for generating an audio signal; and each of the data generator and the audio signal generator. A signal processing unit that captures an output of the data, adds a correction code for performing error correction to the data, and modulates the data to which the correction code is added based on an output of the audio signal generation unit; A multiplexing unit for multiplexing an output of the processing unit and an output of the audio signal generation unit into mutually independent frequency bands, and transmitting the multiplexed signal to a receiving side. Generator. 2. The signal processing unit according to claim 1, wherein the signal processing unit performs an error correction code operation process on the data output from the data generation unit, and adds the error correction code as a result of the operation process to the data. Coding means for performing coding and MSK modulation processing on the output of the coding means based on the output level of the audio signal generation unit
2. The FM multiplexing data generating apparatus according to claim 1, further comprising K modulation means. 3. An FM multiplexing data generating apparatus according to claim 1, wherein an output of said data generating section has a low rate and an amount of information smaller than a predetermined standard level.