JP2606747B2 - Automatic tracking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention relates to an automatic tracking method for switching to the same program broadcasting station having a good reception condition by a digital data multiplexing system, and particularly to a method for automatically receiving a station currently being received during automatic tracking. The present invention relates to an automatic tracking method capable of promptly switching to the same program broadcasting station having a good reception state even when the level rapidly deteriorates.

<Prior art> In a car radio, the driver usually operates the radio, and when the car moves long distances and leaves the service area of the receiving station, it is necessary to reselect the station every time. Advanced functions have been required. This requirement was particularly strong in Europe, where radio broadcasting services are mainly used for FM broadcasting, which has a relatively narrow service area, and the broadcast reception ratio on car radio is high. A digital data multiplexing system standardized by the European Broadcasting Corporation to meet this demand is the RDS (Radio Data System).

RDS is a system that multiplexes and transmits various digital data (data that can be used for automatic selection of the best receiving station, traffic information identification, display of broadcast station name, etc.) to FM radio broadcasting, using AF codes and PI codes. Thus, automatic tracking can be performed so as to successively receive broadcast stations having the same broadcast content in a good reception state.

The AF code is called an alternative frequency code, and is equivalent to the frequency code of a broadcasting station (AF station) that broadcasts the same program in the same or adjacent reception area. All frequencies can be understood. 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 program is different, the same program has a common PI code.

Conventionally, for example, when the same broadcasting station is automatically followed by a one-channel receiver, the signal strength (for example, the electric field strength) of the currently receiving broadcasting station and the strongest electric field strength are determined based on the AF code. AF stations are compared and AF stations with a stronger electric field strength than the receiving station are automatically received.

<Problems to be Solved by the Invention> However, in the conventional automatic tracking method, when searching for the strongest station of the AF stations currently being compared with the receiving station, the station is selected from all the stations in the AF list. Therefore, if a car enters a valley of a building or the like, which is susceptible to multipath, and the reception condition deteriorates rapidly, the AF station update will be delayed, and abnormal noise will be output from the speaker, causing discomfort to the user. And other problems.

As described above, an object of the present invention is to provide an automatic tracking method capable of updating an AF station without a sense of incongruity even when the reception state suddenly deteriorates.

<Means for Solving the Problems> According to the present invention, the present invention relates to a monitoring means for monitoring a signal level of a current receiving station, and when the output of the monitoring means falls below a first level, the signal level is the same. When the detection of the program broadcasting station is started, and the output of the monitoring means falls below the second level during the detection, the detection is interrupted, and the AF station having the maximum signal level among the stations detected before the interruption is stopped. To determine whether the AF station and the current receiving station have the same PI code.If the AF code is the same, it is determined that the broadcasting station is broadcasting the same program, and Control means for receiving the station.

<Operation> When the signal strength of the receiving station falls below the first level by the monitoring means for monitoring the signal level of the receiving station, detection of the same program broadcasting station having the highest signal level is started, and during the detection, the monitoring means is started. When the output becomes lower than the second level, the detection is interrupted, and the same program broadcasting station having the highest signal level among the stations detected before the interruption is made receivable.

<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 denotes a PLL circuit which outputs a predetermined voltage signal corresponding to a station to be received to the front end 2. The front end 2 receives a broadcast station input from an antenna (ANT) based on a voltage signal, and generates a predetermined intermediate frequency signal (IF). Reference numeral 3 denotes an intermediate frequency amplifier, which amplifies the intermediate frequency signal. Reference numeral 4 denotes an IF detector, which detects an intermediate frequency signal converted by the front end 2 and amplified by the intermediate frequency amplifier circuit. Reference numeral 5 denotes a stereo demodulation circuit, and an IF detector 4
Is demodulated into a stereo signal. Reference numeral 6 denotes an amplifier, which amplifies a stereo signal. Reference numeral 7 denotes a speaker which is driven by the amplifier 6 and outputs an audio signal corresponding to the stereo signal.

Reference numeral 8 denotes an RDS decoder, which demodulates an AF code or the like transmitted at a predetermined transmission timing. Reference numeral 9 denotes an error correction circuit, which outputs an R code such as an AF code demodulated by the RDS decoder 8.
DS data errors are detected while synchronizing for each group, and the errors are corrected.

Reference numeral 10 denotes a signal meter, which is the signal intensity (for example, electric field intensity) of the intermediate frequency signal output from the intermediate frequency amplifier 3
, The level of the reception state of the receiving station is detected.

Reference numeral 11 denotes a control unit that controls the overall operation of the radio data system receiver, and compares the signal strength of the receiving station with the signal strength of the AF station based on the detection level of the signal meter 10 to determine the AF having the strongest signal strength. It has comparison means 12 for detecting stations. Further, the control unit 11 obtains, via the RDS decoder 8 and the error correction circuit 9, an AF code and the like in the same program broadcast transmitted by being superimposed on the received broadcast signal, and obtains a frequency control signal based on the AF code. Is output to the PLL circuit 1 to perform automatic tracking.

Next, the operation of the in-vehicle radio receiver of the present invention at the time of automatic tracking will be described with reference to the flowchart of the process shown in FIG.

When an arbitrary broadcast station is selected (step 101), the control unit 1
1 checks via the RDS decoder 8 and the error correction circuit 9 whether an RDS code such as an AF code or a PI code is superimposed on the received broadcast signal (step 102). When the RDS code is superimposed, the control unit 11 reads the RDS code,
The signal strength of the received signal is monitored by the signal meter 10 (step 103).

The input level of the receiving station is the first threshold level E ₁
When the signal level becomes below (step 104), the signal strength of the AF station is compared with the signal meter 10 and the comparison means 12 is started (step 105), and the AF station (MAX station) having the strongest signal level is started.
Is started (step 106). In that case, if the station on the AF list is as shown in Fig. 3, 87.9
Compare the signal strength of AF stations at 88.0 MHz and 88.0 MHz. Further, the control unit 11 determines from the output of the signal meter 10 whether or not the level of the currently receiving station is equal to or lower than the _second threshold level E ₂ (E ₂ <E ₁ ) (step 107). if ₂ or less, i.e. if present signal level of the station currently being received between E ₁ and E _2, and confirm that a checking of all the AF station has been completed (step 108), it has not been completed For example, the next AF station, 88.1 MHz, is detected (step 109), and steps 103 and 104 are detected.
After that, in step 105, the signal is compared with the AF station whose signal strength is determined to be large in the previous comparison. During the MAX station detection operation of the antenna input level station currently being received exists between E ₁ and E ₂ are, a checking of all the AF station is continued until the end. If the check of all AF stations is completed in step 108, the station having the highest signal strength among all AF stations is detected.
Compare the signal strength of the X station (step 110). If the signal strength of the MAX station is strong, move the receiving station to the detected MAX AF station (step 111), and check whether the set station and the receiving station have the same PI. Is determined (step 112), and if the PI is the same, the PLL circuit 1 intermittently down-seeks or up-seeks while temporarily interrupting the broadcast currently being received to tune to the MAX station (step 114). . If it is not the same PI, it is determined that it is a station on another network and the receiving station is not changed (step 113), the station that is determined to be the MAX station is deleted from the AF list (step 114), usually becomes unbearable to listen to the broadcast itself the reception level to detect the re-MAX station is below thread Tsushi yaw field level E _2.
Therefore, at step 107, at the E ₂ or less, i.e., MAX A
If the reception condition suddenly deteriorates during the detection of the F station, the control unit 11 interrupts the detection of the MAX AF station, and the AF station having the highest signal level among the stations detected before the interruption. And the current receiving station is compared (step 115). If the signal strength of the MAX station is strong, the receiving station is moved to the MAX AF station (step 11).
6), it is determined whether the PI is the same (step 117). If the PI is the same, the processing after step 114 is performed. Otherwise the same PI, deletes the MAX AF station from the AF list (step 118), the signal strength of the station currently being received to determine whether the E ₂ following states (step 119). If in E ₂ following conditions, still detects AF station that is not a checking (step 120), (step 121) to together to perform level comparison with the receiving station, it is judged whether or not the same PI (step 122 ). If it is the same PI, the processing after step 114 is performed. If it is not the same PI, the AF station is deleted from the AF list (step 123), and the processing after step 119 is performed. If a receivable station cannot be detected in step 115, the processing after step 120 is performed, and if it is detected in step 119 that the reception state has been recovered, the processing after step 103 is performed again. Search for receivable stations.

Note that the above-described automatic tracking operation is performed by interrupting the currently receiving broadcast for a time that does not cause a sense of discomfort.

<Effects of the Invention> As described above, according to the present invention, when the signal level of the receiving station falls below the first level, the monitoring unit that monitors the signal level of the receiving station detects the same program broadcasting station having the maximum signal level. Start, and during the detection, the output of the
When the level falls below the level, the detection is interrupted, and the AF station having the highest signal level among the stations detected before the interruption is selected, and the AF station is selected.
It is determined whether or not the same PI code between the station and the current receiving station, if the same PI code, it is determined that the broadcasting station is broadcasting the same program, and the AF station is received. Therefore, even when the reception level suddenly deteriorates, not only can the receiving station be instantly switched to a station broadcasting the same program with good reception conditions, but at that time, a broadcast station on another network may be erroneously received. Can be prevented.

[Brief description of the drawings]

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, FIG. 2 is a flowchart of processing of the present invention, and FIG. 3 is a diagram showing an example of an AF frequency list. . 1 ... PLL 2, 2 ... FM front end, 8 ... RDS decoder, 9 ... Error correction circuit, 10 ... Signal meter, 11
... Control unit, 12 ... Comparison means.

Claims (1)

(57) [Claims] 1. The same program is broadcast based on an AF code included in transmission data of a radio data system.
In an automatic tracking method for receiving an AF station, a monitoring means for monitoring a signal level of a current receiving station is provided, and when the output of the monitoring means falls below a first level, detection of the same program broadcasting station having a maximum signal level is performed. When the output of the monitoring means falls below the second level during the detection, the detection is interrupted, and the AF station having the highest signal level among the stations detected before the interruption is selected. The station and the current receiving station determine whether they have the same PI code, and
An automatic tracking method characterized by determining that a PI code is a broadcasting station broadcasting the same program and receiving the AF station.