JPH0779272B2 - RDS automatic tracking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an automatic tracking method for receiving a broadcasting station (AF station) having the same broadcast content by automatic tracking using an RDS (radio data system), and in particular, an automatic tracking method. The present invention relates to an RDS automatic tracking method capable of preventing a malfunction during tracking.

<Prior Art> In a car radio, it is usually the driver who operates it, and when the car travels a long distance and goes out of the service area of the receiving station, it is necessary to re-tune each time. There has been a demand for higher functionality. Especially in Europe, where FM broadcasting, which has a relatively small service area, is the main body of radio broadcasting services and the ratio of car radio reception is high, this requirement was strong. The data system standardized by the European Broadcasting Union to meet this requirement is RD
It is S (Radio Data System).

RDS is a system that multiplexes various digital data (data that can be used for automatic selection of the best receiving station, traffic information identification, broadcast station name display, etc.) in FM radio broadcasting, using AF code and PI code. Thus, it is possible to perform automatic follow-up to successively receive broadcasting stations having the same broadcast content and having a good reception state.

The AF code is called an alternative frequency code and corresponds to the frequency code of a broadcasting station (AF station) broadcasting the same program in the same or adjacent receiving areas. By referring to such AF code, the same program broadcasting station All frequencies are known. Further, the PI code is called a program identification code and is a unique code given to the same broadcast program (program). Even if the broadcast stations are different, the same program has a common PI code.

Conventionally, for example, when the receiver of one tuner automatically follows the same broadcasting station, the signal strength (for example, electric field strength) of the broadcasting station currently being received and the electric field strength of the AF station are calculated based on the AF code described above. Compare and automatically receive stronger field strength than the receiving station
AF station was newly received. In addition, the comparison of the electric field strength is
The broadcast currently being received is interrupted for a short time without any discomfort.

<Problems to be solved by the invention> However, in the conventional automatic tracking method using RDS,
If there is an adjacent station with a strong electric field that uses a broadcasting frequency near the broadcasting frequency of the station, the electric field strength of the adjacent station is detected as the electric field strength of the AF station, and even if there is no AF station,
Even if the electric field strength of the station is weak, there is a problem that the reception frequency is switched for a moment. Therefore, there is a problem that an abnormal sound is output from the speaker and the user feels uncomfortable.

From the above, the object of the present invention is to provide an RDS automatic tracking method capable of reliably switching to an AF station with a good reception state without being affected by an adjacent station having a strong electric field and preventing a malfunction during automatic tracking. That is.

<Means for Solving the Problems> According to the present invention, the above-mentioned problems are the first means for detecting the signal strength of the receiving station and the signal strength at a predetermined frequency deviation ± Δf from the broadcast frequency of the receiving station. When the signal strength of the current receiving station detected by the first means and the second means for determining that the receiving station is present when the level is higher than or equal to the level is equal to or lower than the set level, the same broadcast is performed based on the AF code. Content
When the means for receiving the AF station and the signal strength detected by the first means are equal to or higher than the set level and the second means determines that the AF station exists, the AF station is continuously operated. Achieved by means of receiving.

<Operation> First means for detecting the signal strength of the receiving station and second means for judging that the receiving station exists when the signal strength at a predetermined frequency deviation ± Δf from the broadcast frequency of the receiving station is equal to or higher than a predetermined level Means is provided, and when the signal strength of the current receiving station detected by the first means falls below a set level, an AF station having the same broadcast content is received based on the AF code and detected by the first means. When the determined signal strength is equal to or higher than the set level and it is determined by the second means that the AF station exists, the AF station is continuously received.

<Embodiment> FIG. 1 is a block diagram of a main part of a radio data system receiver for realizing an automatic tracking method according to the present invention.

Reference numeral 1 is a PLL circuit, which outputs a predetermined voltage signal corresponding to a station to be received to the FM front end 2. The FM front end 2 receives the broadcasting station input from the antenna ANT based on the voltage signal, and generates a predetermined intermediate frequency signal (IF). An intermediate frequency amplifier 3 amplifies the intermediate frequency signal converted by the FM front end 2 to a predetermined level. An MPX 4 demodulates the intermediate frequency signal input from the intermediate frequency amplifier 3 into a stereo signal. An amplifier (AMP) 5 amplifies a stereo signal according to a volume setting value (not shown). A speaker 6 is driven by the amplifier 5 and outputs a voice signal.

An RDS decoder 7 demodulates the AF code, PI code, etc. sent at a predetermined transmission timing. An error correction circuit 8 detects an error in the RDS data such as the AF code and PI code demodulated by the RDS decoder 7 while synchronizing each group and corrects the error.

A signal meter 9 detects the level of the receiving state of the receiving station by monitoring the signal strength (for example, electric field strength) of the intermediate frequency signal output from the intermediate frequency amplifier 3. Reference numeral 10 is a station detector that determines that a receiving station exists when the received signal is within the frequency deviation Δf (bandwidth) of the received signal and the signal strength is equal to or higher than a predetermined level. It is commercialized as the circuit TA8129Z. That is, the receiving station frequency is f _0, if present a strong electric field adjacent stations to the higher than f _0, it can be determined that the signal strength in f ₀ -.DELTA.f is when more than a predetermined level, there is a receiving station, and, If the strong electric field adjacent station exists lower than f ₀ , it can be determined that the receiving station exists when the signal strength at f ₀ + Δf is equal to or higher than a predetermined level. Therefore, the station detector 10 determines that the receiving station exists when the signal strength is equal to or higher than a predetermined level in both f ₀ ± Δf, and reliably detects the presence or absence of the receiving station without being influenced by the adjacent station. it can. Therefore, when the station detect signal SD is at a low level, even if the signal strength detected by the signal meter 9 is large, the broadcasting station at the tuning point does not actually exist, and the detected signal strength is influenced by the adjacent station. I understand that I am receiving. That is, in the automatic tracking method of the present invention, the presence or absence of the AF station is determined by detecting the signal strength and the frequency deviation Δf.

Reference numeral 11 is a main microcomputer that controls the overall operation of the radio data system receiver. During automatic tracking, the signal strength of the receiving station and the signal strength of the AF station are compared based on the detection level of the signal meter 9 to determine the reception status. Means to find a good AF station,
The station detector 10 has means for receiving the AF station only when it is determined that the AF station exists. Further, the main microcomputer 11 obtains the AF code or the like in the same program broadcast superposed on the received broadcast signal via the RDS decoder 7 and the error correction circuit 8, and when the reception state becomes poor, A frequency control signal based on the AF code is output to the PLL circuit 1 for automatic tracking. That is, the main microcomputer 11 has signal strength and
Automatically follow only AF stations that output SD signals to prevent accidentally automatically following AF stations with poor reception.

According to the process flow chart of the present invention shown in FIG.
The operation of the figure will be described.

When an arbitrary broadcasting station is selected (step 101), the main microcomputer 11 checks, via the RDS decoder 7 and the error correction circuit 8, whether or not an RDS code such as an AF code or a PI code is superimposed on the received broadcasting signal. (Step 102). When the AF code is superimposed, the main microcomputer 11
The code is read (step 103), and the signal strength of the received broadcast is monitored by the signal meter 9 (step 10).
Four).

When the signal strength of the received broadcast falls below a predetermined level, the main microcomputer 11 PLLs the frequency control signal according to the AF code.
Output to circuit 1 and start automatic tracking (step 10
Five).

In such automatic tracking, the main microcomputer 11 first determines whether or not the signal strength of the AF station by the signal meter 9 is a good reception level (step 106), and if YES, then the station detector 10 determines whether or not there is an AF station. Is determined (step 107), and if there is an AF station, it automatically follows the AF station (step 108).

On the other hand, in step 106, AF is performed by the signal meter 9.
If the signal strength of the station is a poor reception level, or if there is no AF station in the determination in step 107, the next AF station is set according to the AF code (step 109), the process returns to step 105, and the subsequent processing is repeated. .

If the RDS code is not transmitted in the determination of step 102, the process ends.

The automatic follow-up according to the present invention is performed by interrupting the currently received broadcast for a short time so that there is no discomfort.

<Effects of the Invention> According to the present invention, the signal strength of the receiving station and the signal strength of the AF station are compared with each other, and it is determined whether the AF station actually exists.
Since the signal strength is strong and the AF station is received only when the AF station exists, the AF station is surely switched to the good receiving state without being affected by the adjacent station of the strong electric field,
It is possible to prevent erroneous operation at the time of automatic follow-up, and therefore, there is an excellent advantage that the automatic follow-up operation can be surely executed even with one tuner configuration.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a radio data system receiver that realizes an automatic tracking method according to the present invention, and FIG. 2 is a flow chart of processing of the present invention. 1 ... PLL circuit, 2 ... FM front end, 3 ... intermediate frequency amplifier, 7 ... RDS decoder, 8 ... error correction circuit, 9 ... signal meter, 10 ... station detector, 11 ... main microcomputer .

Claims (1)

[Claims] 1. An RD that receives an AF station having the same broadcast content based on an AF code included in transmission data of a radio data system.
In the automatic tracking method of S, the first means for detecting the signal strength of the receiving station and the presence of the receiving station when the signal strength at a predetermined frequency deviation ± Δf from the broadcast frequency of the receiving station is equal to or higher than a predetermined level A second means for determining is provided, and when the signal strength of the current receiving station detected by the first means becomes equal to or lower than a set level, an AF station having the same broadcast content is received based on the AF code, When the signal strength detected by the means is equal to or higher than a set level, and the AF station is determined to exist by the second means, the RDS automatic reception is characterized by continuously receiving the AF station. How to follow.