JP2978263B2 - RDS receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to radio data suitable for in-vehicle use, which receives data from a broadcasting station forming a network and automatically selects and receives radio waves from a broadcasting station having a high electric field strength. The present invention relates to an improvement in a system receiver (hereinafter, referred to as an RDS receiver).

[0002]

2. Description of the Related Art In the above-mentioned radio data system (RDS), 1 which is a main carrier of an FM modulated wave is used.
5 which is the third harmonic of the 9KHz stereo pilot signal
7 KHz is used as a sub-carrier, this sub-carrier is carrier-suppressed amplitude-modulated by a bi-phase coded RDS data signal, and the amplitude-modulated sub-modulated wave is frequency-modulated on the main carrier to be added to the FM audio signal. RDS data indicating a broadcast station name, a same broadcast frequency list, and the like are multiplexed and broadcast.

FIG. 4 shows a list of the RDS data.
FIG. 5 shows a transmission format of RDS data. The RDS receiver receives and decodes the RDS data of FIG. 4 transmitted in accordance with the transmission format of FIG. 5, and for example, in an on-vehicle RDS receiver, a running vehicle moves from a reception area of a broadcast station currently receiving. When it becomes difficult to listen to the program that has been received up to that point, the broadcasting station broadcasting the same program is automatically determined based on the frequency list of the same broadcasting station included in the RDS data. The program is tuned and switched one after another so that the same program can be continuously listened to.

In the above-described RDS receiver, when it is difficult to listen to the broadcast station away from the reception area of the currently receiving broadcast station, the RDS receiver switches to another broadcast station broadcasting the same program. At this time, the electric field strength from the currently receiving broadcast station is weakened, another broadcast station of the same program is identified, and PLL data (tuning voltage TV, which is applied to the varicap DC level or high level, which is the AND output of the detection output from the level detector and the S-curve output after a fixed time (usually 16 ms) from the time when the PLL output of the low-pass filter (DC output voltage) is output at the applied DC voltage. Check the low level SD output (station detector output)
Mute is released when output is present.

[0005]

By the way, the time for transmitting the above-mentioned mute output, that is, the SD wait time (16 ms) is the same as the frequency of the currently receiving broadcasting station. This time is constant regardless of whether the frequency of the broadcast station is far from or close to the frequency of the broadcast station. That is, FIG.
As shown in (B), the time from when the TV output corresponding to the other broadcasting station is transmitted to when the SD output is transmitted is determined by the frequency of the currently receiving broadcasting station and the time of the other broadcasting station. Since the frequency is constant even if it is far from or close to the frequency, the frequency change processing time (AF check time), that is, the mute time is long even when a broadcast from a close broadcast station is selected. There was a problem of becoming.

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to select another broadcasting station of the same program from a currently receiving broadcasting station. By changing the SD wait time depending on whether the frequency of the current broadcast station is distant from or close to the frequency of the currently receiving broadcast station, the AF check time, ie, the mute time, can be reduced when switching to a nearby broadcast station. To provide a possible RDS receiver.

[0007]

SUMMARY OF THE INVENTION An RDS receiver according to the present invention achieves the above-mentioned object. The RDS receiver receives data of a broadcasting station forming a network and is currently receiving the data. A radio data system (RDS) receiver which automatically selects and receives radio waves from other broadcasting stations having a high electric field strength when the electric field strength of a broadcasting station is weakened. So,
When switching from the currently receiving broadcast station to the other broadcast station, a difference between the frequency of the currently received broadcast station and the frequency of the other broadcast station is calculated, and the SD wait time is proportional to the difference. This is to control by.

[0008]

The RDS receiver of the present invention configured as described above automatically reduces the electric field strength of the currently receiving broadcasting station and automatically transmits radio waves from other broadcasting stations having a high electric field strength forming a network. When selecting and switching, the difference between the frequencies of the other broadcasting stations is calculated from the frequency of the currently receiving broadcasting station, and the SD wait time is set for a time proportional to the difference, so that the frequency change processing time Shorter mute time.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the RDS receiver according to the present invention will be described below with reference to FIG. The FM multiplex broadcast wave received by the antenna 1 is used to select a desired broadcast station on the FM front end 2 by a controller 9 command described later based on the operation of an operation panel switch 12 described later, It is supplied to the detector 4. The FM front end 2 employs, for example, a PLL synthesizer method using a PLL circuit including a programmable frequency divider, and performs a channel selection operation by controlling the frequency division ratio of the programmable frequency divider by the controller 9. Has become.

[0010] The detection output of the FM detector 4 is supplied to an MPX (multiplex) demodulation circuit 5, where the signal is separated into audio signals of L (left) channel and R (right) channel in the case of stereo broadcasting. The L and R audio signals demodulated by the MPX demodulation circuit 5 are transmitted to the controller 9.
Is connected to a low-frequency amplifier (not shown) via a mute circuit 6 controlled by the control circuit.

On the other hand, the detection output of the FM detector 4 is 5
It is also supplied to a 7 KHz band pass filter 7, and by passing through this filter 7, a 57 KHz sub-carrier, ie, an RDS data signal, whose amplitude is modulated is extracted from the detection output, and supplied to the RDS data demodulation circuit 8. You.

The RDS data demodulation circuit 8 demodulates the RDS data signal sent from the 57 KHz band-pass filter 7 and decodes it into the original RDS data. As shown in FIG. 5, this decoded RDS data forms one group by linking four blocks with 26 bits as one block, and 10 bits of 10 bits allocated to the check word of each block. Based on the offset word, the start bit of the block and which block the group is in are identified. Also,
Based on the check word, error detection of the 16-bit information word of the block is performed. The decoded RDS data is supplied to the controller 9.

The controller 9 is constituted by a microcomputer. The controller 9 fetches the code information of each block in the RDS data sequentially inputted in groups and stores it in the RAM 10. The operation switch panel 12
The frequency division ratio of a programmable frequency divider (not shown) of the PLL circuit which constitutes a part of the front end 2 is controlled based on the channel selection operation given from, and a desired FM station is selected. Note that the selected reception frequency is stored in the RAM 11.

The controller 9 is connected to a display 13 composed of a liquid crystal display element or the like, so that necessary information such as a receiving station name and data of a receiving frequency is displayed. The processing operation of the controller 9 is executed according to a control program stored in the ROM 11.

Further, the controller 9 is supplied with a level detection output from a level detector 14 for detecting the strength of the signal based on the IF signal level, that is, the fact that the electric field intensity has fallen below a set level. When the output is supplied to the controller 9, it is determined that the reception state of the currently receiving broadcast station has deteriorated, and another broadcast station based on the AF data of the broadcast station broadcasting the same program stored in the RAM 10 in advance is determined. An operation of controlling the frequency division ratio of the programmable frequency divider to select a station is also performed.

Next, the operation based on the configuration described above will be described with reference to FIG.
This will be described with reference to the flowchart of FIG. Since the level detector 14 detects the electric field strength from the currently receiving broadcast station, the level detection output from the level detector 14 is supplied to the controller 9. The controller 9 monitors whether the detection output from the level detector 14 has fallen below a preset level (step S1), and keeps the electric field intensity below the set level for a certain period of time (the time when the AF data makes one round). Is reached, Δf, which is a value obtained by subtracting the AF frequency of the broadcasting station broadcasting the same program from the frequency currently being received, is calculated (step S2).

After this Δf is calculated, the wait time of SD is calculated and the timer time is set. That is, wait time (ms) = 8 (ms) + 8 × Δf (MHz) /
108.0-87.5 (MHz) is calculated (step S3).

Here, for example, if the total bandwidth of the FM broadcast is 8
Assuming that the frequency is 7.5 to 108.0 MHz, the frequency of the currently receiving broadcasting station is 100 MHz, and the AF frequency is 105 MHz, Δf is 5 MHz and the wait time is 9.95 ms. On the other hand, assuming that the frequency of the currently receiving broadcast station is 88 MHz and the AF frequency is 105 MHz, Δf is 17 MHz and the wait time is 14.
63 ms. As described above, depending on whether the frequency of the currently receiving broadcast station and the AF frequency are distant or close to each other, the wait time becomes longer or shorter.

Then, if the wait time is set by the controller 9 based on the above formula,
The PLL output of the AF frequency is sent to the front end 2, and a command for muting the output from the MPX demodulation circuit 5 is sent to the mute circuit 6 (step S).
4). Thereby, the mute circuit 6 is connected to the MPX demodulation circuit 5
Cut more output.

On the other hand, the controller 9 monitors whether the set timer time has elapsed (step S5).
If the time has elapsed, a mute release output is sent to the mute circuit 6 to release the mute (step S
6). That is, when switching to a nearby broadcast station, it is possible to listen to the broadcast of the new broadcast station in a short mute time.

As described above, as shown in FIGS. 3A and 3B, the wait time can be set in accordance with the response speed of the SD after the TV output rises by the data output of the PLL. The mute time can be reduced.

[0022]

As described above, the present invention calculates the difference between the frequencies of the currently receiving broadcasting stations and the frequencies of the other broadcasting stations forming the network, and calculates the SD wait time by a time proportional to the difference. Therefore, when the frequency of the currently receiving broadcast station and the frequency of the other broadcast station are close to each other, the AF check time is shortened and the mute time is shortened. .

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing the operation of the controller in FIG. 1;

FIG. 3 is an operation diagram for explaining a mute time.

FIG. 4 is a list of RDS data.

FIG. 5 is a transmission format of RDS data.

FIG. 6 is an operation diagram for explaining a conventional mute time.

[Explanation of symbols]

 Reference Signs List 1 antenna 2 front end 3 IF amplifier 4 FM detector 5 MPX demodulation circuit 6 mute circuit 7 bandpass filter 8 RDS data demodulation circuit 9 controller 10 RAM 11 ROM 12 operation panel switch 13 display 14 level detector

Claims (1)

(57) [Claims] 1. When data of a broadcasting station forming a network is received and the electric field strength of the currently receiving broadcasting station becomes weaker, data from another broadcasting station having a higher electric field strength forming the network is received. A radio data system (RDS) receiver for automatically selecting and receiving radio waves, which is currently being received when switching from the currently receiving broadcast station to the other broadcast station. An RDS receiver, wherein a difference between the frequencies of the other broadcasting stations is calculated from a frequency of a broadcasting station, and the SD wait time is controlled in proportion to the difference.