JP3660974B2 - RDS receiver and receiving method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an RDS receiver that automatically performs channel selection using an RDS (Radio Data System) and a reception method thereof.
[0002]
[Prior art]
Since the on-vehicle radio receiver is used even while the vehicle is moving, the reception condition deteriorates while the vehicle moves over a long distance due to being out of the service area of the receiving station or being affected by buildings, etc. In that case, re-tuning is generally performed. RDS is a digital data multiplex system that was developed mainly in Europe, where radio broadcast services are mainly FM broadcasts with a relatively small service area, and has been standardized by the European Broadcasting Union. In such a case, in order to eliminate the need for the driver to re-select the channel manually, a function of automatically selecting an AF station that is broadcasting the same program as the currently received broadcast at another frequency is provided. There is something.
[0003]
RDS, which is now widely used in Europe, is a system that transmits FM radio broadcasts with accompanying digital data (data for automatic channel selection, traffic information identification, data that can be used for broadcasting station name display, etc.) multiplexed. In addition, the incidental digital data includes an AF list and PI data for performing an automatic search for appropriately selecting the same program broadcasting station (AF station) having a good reception state. The AF list is also called an alternative frequency list and corresponds to a frequency list of a broadcasting station (AF station) that broadcasts the same program in the same or adjacent receiving area. By referring to the AF list, the currently received broadcast All the frequencies of broadcast stations that broadcast the same program are known. PI data is also called program identification data, and is unique data given to the same broadcast program (program). If different broadcast stations transmit the same broadcast program, both Broadcast stations have common PI data, and the PI data of the broadcast currently being received can be known by extracting the PI data from the RDS data being received.
[0004]
In a conventional RDS receiver, for example, when a receiver with a single tuner configuration performs automatic search for a station (AF station) of the same broadcast program as the currently receiving broadcast station B0 at a frequency f0, it is demodulated by an RDS decoder. When the AF list is extracted from the RDS data and stored in the memory, and the current reception state deteriorates, a certain broadcasting station B1 on the AF list stored in the memory is received at the frequency f1, and the newly received signal is received. It is determined whether the received electric field strength of the broadcast of the AF station (that is, the receiving station after changing the frequency) B1 is a predetermined value (for example, 20 dBμV) or more, and the noise level of the received signal of the AF station is predetermined. It is determined whether or not it is less than or equal to the value.
[0005]
As a result of the determination, if the received electric field strength of the currently receiving AF station (B1) is equal to or higher than a predetermined value and the noise level of the received signal is lower than the predetermined value, the PI code of the currently received broadcast B1 Is coincident with the PI code of the original broadcast B0, and if it coincides, the receiving AF station B1 is continuously received.
If the received electric field strength of the newly received AF station (B1) broadcast is smaller than the predetermined value as a result of the above determination, the received frequency is temporarily returned to the original frequency (f0) to return to the original broadcast station. After receiving B0, an AF station other than B1 on the AF list (for example, B2) is searched.
[0006]
[Problems to be solved by the invention]
As described above, in the conventional RDS receiver, when searching for an AF station that can be satisfactorily received from the broadcasting stations on the AF list, the broadcast of a newly received AF station (B1 described above) is broadcast. If the received electric field strength is not greater than or equal to a predetermined value, it is determined that reception is impossible, and the next AF station (eg, B2) is searched. The reason for setting the conditions for switching to the AF station in this way is to prevent switching to other than the AF stations that can be received well, as well as frequent switching of the receiving broadcast station, and switching noise and sound quality each time. This is to prevent the volume from changing.
[0007]
The above items will be described with reference to the drawings. FIG. 3 is a diagram illustrating a reception state when an RDS broadcast is received in a traveling vehicle. The horizontal axis indicates elapsed time, and the upper and lower stages have the same value. The upper part of the figure shows the reception state when the broadcast station A is received, and the lower part shows the reception state when the broadcast station B is received. The reception state is indicated by the received electric field strength and the amount of noise included in the audio signal obtained by FM detection.
In the figure, at both the broadcasting station A and the broadcasting station B, the received electric field strength is large at the beginning and small in the latter half. In addition, the amount of noise is small in the first half in broadcasting station A and increases in the second half, while in broadcasting station B, the first half and second half remain relatively small. The noise is caused by multipath distortion or broadcasting of adjacent frequencies.
[0008]
Comparing the reception status of broadcast station A and broadcast station B, the first station is 20 dBμV or more in both stations, and it is traveling in an area where the received electric field strength is relatively high. Has been. The received electric field strength of the broadcasting station A starts to decrease from the middle, and in the second half, the amount of noise increases and the reception state deteriorates, but in the second half, the receiving electric field strength of the broadcasting station B is larger than the broadcasting station A. Even though the noise is small, the received electric field strength of broadcasting station B, which is an AF station, is smaller than the predetermined value of 20 dBμV, so that the received broadcast does not switch from station A to station B, and continues in a state where there is a lot of noise. Broadcast station A is continuously received.
[0009]
As described above, the conventional RDS receiver has a problem that even in the weak electric field region, even if there is an AF station that can receive with low noise, it cannot be switched and received.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an RDS receiver capable of receiving an AF station even when the received electric field strength of the AF station in RDS broadcasting is small, and a receiving method thereof. It is to be.
[0010]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems, and the first invention is an RDS receiver that selects a channel by using an AF list and PI data transmitted by being superimposed on an RDS broadcast. Electric field strength measuring means for measuring the received electric field strength of the broadcast wave, noise measuring means for measuring the noise level of the received broadcast wave or a signal after detection thereof, and the AF list and PI data from the received broadcast wave. And an RDS decoder for extracting, when the reception state of the receiving broadcast station deteriorates, the broadcast of a certain AF station in the received AF list is received, and the received electric field strength of the original receiving broadcast station is smaller than a predetermined value. When the noise level of the received signal of the AF station being received is below a predetermined value and the PI data of the broadcast of the AF station being received matches the PI data of the original received broadcast, the release of the AF station being received is released. Regardless of the reception field intensity is RDS receiver which is adapted to continuously receive the broadcast AF station being received.
[0011]
According to a second aspect of the present invention, in the RDS receiver according to the first aspect of the present invention, a broadcast of a certain AF station in the AF list received when the reception state of the reception broadcast station deteriorates is received, and the reception of the original reception broadcast station is received. When the electric field strength is equal to or higher than a predetermined value, the received electric field strength of the receiving AF station is equal to or higher than the predetermined value, the noise level of the received signal is lower than the predetermined value, and the received PI data of the broadcasting of the AF station and the original The RDS receiver is configured to continuously receive the broadcast of the receiving AF station only when the PI data of the received broadcast matches.
[0012]
According to a third aspect of the present invention, there is provided a receiving method of an RDS receiver that performs channel selection using an AF list and PI data transmitted superimposed on an RDS broadcast, and an electric field strength for measuring a received electric field strength of a received broadcast wave. Including a measurement step and a noise measurement step of measuring a noise level of the received broadcast wave or a signal after detection thereof, and when a reception state of the reception broadcast station deteriorates, a certain AF station in the received AF list If the received electric field strength of the original receiving broadcast station is smaller than a predetermined value and the noise level of the received signal of the receiving AF station is less than the predetermined value, the PI data of the broadcast of the receiving AF station and It is determined whether or not the PI data of the original received broadcast matches, and if it matches, the received AF station broadcast is continuously received regardless of the received electric field strength of the received AF station broadcast. RDS received To a receiving method of the machine.
[0013]
According to a fourth aspect of the present invention, in the reception method of the RDS receiver of the third aspect, when a reception state of the reception broadcast station deteriorates, a broadcast of an AF station in the received AF list is received, and the original reception broadcast If the received electric field strength of the station is equal to or higher than a predetermined value, the received electric field strength of the receiving AF station is equal to or higher than the predetermined value, the noise level of the received signal is lower than the predetermined value, and the broadcast PI of the receiving AF station is PI This is a reception method of the RDS receiver that continuously receives the broadcast of the AF station being received only when the data and the PI data of the original reception broadcast match.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. When the reception status of the receiving broadcast station deteriorates while receiving the RDS broadcast, the frequency is switched to a certain AF station in the AF list decoded from the currently received broadcast wave, and the broadcast is received. It is determined whether or not the received electric field strength of the broadcasting station is equal to or higher than a predetermined value. If the received electric field strength of the original receiving broadcast station is smaller than a predetermined value in the determination and the noise level of the broadcast of the receiving AF station is less than the predetermined value, the PI data of the receiving AF station broadcast and the original reception It is determined whether or not the PI data of the broadcast matches, and if they match, the broadcast of the AF station being received is continuously received regardless of the received electric field strength of the broadcast of the AF station being received.
[0015]
If the received electric field strength of the original receiving broadcast station is equal to or greater than a predetermined value in the determination, it is determined whether or not the received electric field strength of the newly received AF station is equal to or higher than the predetermined value. If the noise level of the broadcast of the AF station being received is equal to or greater than the predetermined value, and whether or not the PI data of the broadcast of the AF station being received matches the PI data of the original received broadcast If they match, the receiving AF station broadcast is continuously received.
[0016]
In the determination, when the received electric field strength of the original receiving broadcasting station is equal to or higher than a predetermined value and the receiving electric field strength of the newly received AF station is smaller than the predetermined value, or the noise level of the broadcasting of the receiving AF station is lower than the predetermined value. If it is larger or the PI data of the broadcast of the AF station being received does not match the PI data of the original received broadcast, the reception frequency is once restored and the same processing is repeated for another AF station, Find an AF station that can receive well.
[0017]
FIG. 1 is a block diagram showing an embodiment of the RDS receiver of the present invention. The RDS receiver 10 mixes the tuning circuit 13, the RF amplifier circuit 15, and the output of the RF amplifier circuit 15 and the output of the local oscillation circuit 25 that pass only the vicinity of the set reception frequency, and the difference in frequency between the two. A mixing circuit 17 that outputs an intermediate frequency signal having a frequency of 1, an IF amplification circuit 19 that amplifies the intermediate frequency signal output from the mixing circuit 17, an FM detector 21 that performs FM detection on the output of the IF amplification circuit 19, MPX22 which produces | generates a stereo signal from the output of FM detector 21, The audio amplifier circuit 23 which amplifies the output of MPX22, and the control means 33 which controls the RDS receiver 30 whole are provided. The output of the audio amplifier circuit 23 is given to a speaker (not shown). When switching the receiving station or performing a search operation, the audio amplifying circuit 23 is temporarily muted under the control of the control means 33 and operates so as not to output the output from the audio amplifying circuit 23.
[0018]
The RDS receiver 10 further includes an electric field intensity measuring means 27 for measuring the received electric field intensity of the received broadcast wave using the intermediate frequency signal in the IF amplifier circuit 19, and an FM detector 21 via a BPF 29 having a center frequency of 57 kHz. RDS decoder 30 that decodes the RDS data using the output of, and noise measurement means 31 that measures the level of the noise signal included in the output of MPX 22. The noise measuring means 31 measures the noise level of the received signal, and the input signal may be the output of the FM detector 21 or the IF signal in the IF amplifier circuit 19, but the output signal of the MPX 22 It is most practical to measure.
[0019]
An operation means 35 and a display means 37 are connected to the control means 33. The control unit 33 includes a microprocessor (MPU) 50, an electric field strength determination unit 51, a memory 52, and a noise determination unit 53. The electric field strength determination unit 51 determines whether the received electric field strength of the received broadcast wave is equal to or higher than a predetermined value based on the output of the electric field strength measurement unit 27 and gives the result to the MPU 50. The memory 52 stores RDS data such as AF data and PI code output from the RDS decoder 30. Based on the output of the noise measurement means 31, the noise determination means 53 determines whether or not the noise level of the reception signal subjected to FM detection is equal to or lower than a predetermined value, and gives the result to the MPU 50.
[0020]
The local oscillation circuit 25 is composed of a PLL (Phase Locked Loop) having the output of the reference signal oscillation circuit 43 as a reference frequency. (LPF) 45. The output frequency of the local oscillation circuit 25 is changed by changing the frequency division ratio in accordance with a control signal supplied from the control means 33 to the frequency divider circuit 42. The output of the LPF 45 is also given to the tuning circuit 13.
The measurement of the received electric field strength in the electric field strength measuring means 27 and the measurement of the noise level in the noise measuring means 31 are not instantaneous measurement values but are continued for a certain period of time and their average values are adopted.
[0021]
When the RDS receiver 10 is received in the traveling vehicle and the reception state deteriorates, an alternative station of the FM station currently being received is searched for in the AF list stored in the memory 52, and is put on the list. A certain AF is received. Then, the MPU 50 determines whether or not the newly received AF station is in a continuously receivable radio wave state based on the output of the electric field strength determination means 51 and the output of the noise determination means 53, and continues. If the radio wave condition is receivable, the PI code of the receiving AF station is compared with the PI code of the original broadcast. If they match, the receiving AF station is continuously received and matched. If not, the receiving broadcast station is temporarily returned to the original broadcast station, and after that, the reception status and PI code of the other AF stations in the AF list received in the original broadcast can be checked and received well. Find an AF station.
[0022]
FIG. 2 is a flowchart showing an AF station receiving method according to the RDS receiver of the present invention. The processing flow shown in FIG. 2 is started at predetermined time intervals while the user is receiving with the RDS receiver. First, RDS data received by the currently receiving broadcasting station is stored in the memory 52 (step S11), and in step S13, the average received electric field strength and average noise level of the receiving broadcast (original broadcast) are measured. In step S15, it is determined whether or not the reception state of the original broadcast is good. This determination is made by comparing the level with a predetermined level by the noise determination unit 53 based on the noise level of the received signal measured by the noise measurement unit 31. If it is determined in step S15 that the reception state is good, this process ends, and the broadcast being received is continuously received.
[0023]
On the other hand, if it is determined in step S15 that the reception state is not good, the process proceeds to step S17. In step S17, the audio amplification circuit 23 is muted so that no audio signal is output, and the AF stored in the memory 52 is stored. A broadcast of an AF station in the list is received. After the tuning to the AF station is achieved, the mute is released. In step S18, PI data of the AF station is acquired by the RDS decoder 30, stored in the memory 52, and the process proceeds to step S19. In step S19, it is determined whether or not the average received electric field strength of the original broadcast (before changing the reception frequency) is equal to or greater than a predetermined value. If it is equal to or greater than the predetermined value, the process proceeds to step S21. If so, the process proceeds to step S23. In step S21, it is determined whether or not the current average received electric field strength of the AF station (after changing the reception frequency) is greater than or equal to a predetermined value. If it is greater than or equal to the predetermined value, the process proceeds to step S23. If so, the process proceeds to step S27.
[0024]
In step S23, it is determined whether or not the average noise level of the currently receiving AF station is equal to or lower than a predetermined value. If the average noise level is lower than the predetermined value, the process proceeds to step S25, and if larger than the predetermined value, the process proceeds to step S27. In step S25, it is determined whether or not the PI code of the AF station currently being received matches the PI code of the original broadcast. If they match, this flow is terminated and the currently received broadcast is continued. And receive. If they do not match, the process proceeds to step S27.
In step S27, the reception frequency is temporarily returned to the original reception frequency, and this flow is temporarily ended. Although the illustration of the processing subsequent to the processing in step S27 is omitted, if there is a broadcast station that has not been searched yet in the AF list, the process returns to step S17, and the frequency that has not been searched yet is determined in step S17. To the step S25 (or step S27) to search for an AF station that can be satisfactorily received.
[0025]
In the above-described embodiment, when the RDS broadcast is received in the traveling vehicle, the received electric field intensity of the received RDS broadcast gradually decreases or the noise gradually increases as illustrated in FIG. It was explained assuming that. On the other hand, when traveling while receiving an RDS broadcast with a low received electric field strength or an RDS broadcast with a relatively large amount of noise, among the broadcasting stations on the AF list, the received electric field strength is large and noise is generated. An AF station with a small amount may appear.
[0026]
In this case, when it is determined in step S15 in FIG. 2 that the original broadcast reception state is not good, the processing from step S17 to step S25 is performed. Switching to the AF station is performed. In areas where the received electric field strength is weak, there are relatively many situations where the noise of the received broadcast signal becomes larger than a predetermined value due to a change in the direction of the vehicle or the influence of surrounding buildings. That is, there are relatively many cases where it is determined in step S15 that the reception state is not good. At this time, if there is a broadcast station that can satisfactorily receive among the AF stations, the receiving station is switched to that AF station.
[0027]
As described above in detail, according to the RDS receiver and the reception method of the present invention, when the reception state of the receiving broadcast station deteriorates during reception of the RDS broadcast and the AF station is searched, the original is detected in step S19. When it is determined that the average received electric field strength of the broadcast is greater than or equal to a predetermined value, the process proceeds to step S23 only when the average received electric field strength of the AF station is determined to be greater than or equal to the predetermined value in step S21. Prevent frequent switching of receiving broadcast stations.
[0028]
On the other hand, when it is determined in step S19 that the average received electric field strength of the original broadcast is less than the predetermined value, the process proceeds directly to step S23 without performing the determination processing in step S21, and the electric field strength of the AF station is increased. Even if it is small, it becomes easy to switch to the AF station. Therefore, according to the present invention, when the received electric field strength of the original broadcast is relatively large, the receiving station is prevented from frequently switching, and when the received electric field strength of the original broadcast is relatively small, the received electric field strength is reduced. There is an effect that it is possible to receive an AF station whose intensity is small and which could not be received conventionally.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of an RDS receiver of the present invention.
FIG. 2 is a flowchart showing an AF station receiving method according to the RDS receiver of the present invention.
FIG. 3 is a diagram illustrating a reception state when an RDS broadcast is received in a running vehicle.
[Explanation of symbols]
13 Tuning circuit 15 RF amplifier circuit 17 Mixer circuit 19 IF amplifier circuit 21 FM detector 22 MPX
23 Audio Amplifier 25 Local Transmission Circuit 27 Electric Field Strength Measuring Means 29 BPF
30 RDS decoder 31 Noise measuring means 33 Control means 50 MPU50
51 Electric field strength determination means 52 Memory 53 Noise determination means

Claims (4)

In an RDS receiver that selects a channel by using an AF list and PI data transmitted by being superimposed on an RDS broadcast, an electric field strength measuring unit that measures a received electric field strength of the received broadcast wave, and a received broadcast wave or A noise measuring means for measuring the noise level of the signal after detection; and an RDS decoder for extracting the AF list and PI data from the received broadcast wave;
When the reception state of the receiving broadcast station deteriorates, the received AF station receives a broadcast of an AF station in the received AF list, and the received electric field strength of the original receiving broadcast station is smaller than a predetermined strength value , and the receiving AF station When the noise level of the received signal is equal to or lower than a predetermined level value and the PI data of the broadcast of the AF station being received matches the PI data of the original received broadcast, the received electric field strength of the broadcast of the AF station being received Regardless of whether or not is smaller than the predetermined intensity value , the RDS receiver is characterized in that it continuously receives the broadcast of the receiving AF station. When a reception state of the receiving broadcast station deteriorates, a broadcast of a certain AF station in the received AF list is received, and if the received electric field strength of the original reception broadcast station is equal to or higher than the predetermined strength value , the reception is in progress The received electric field strength of the AF station is greater than or equal to the predetermined intensity value , the noise level of the received signal is less than or equal to the predetermined level value , and the PI data of the AF station broadcast being received and the PI data of the original received broadcast are 2. The RDS receiver according to claim 1, wherein the broadcast of the receiving AF station is continuously received only when they match. In a receiving method of an RDS receiver that selects a channel using an AF list and PI data transmitted by being superimposed on an RDS broadcast, an electric field strength measuring step for measuring a received electric field strength of a received broadcast wave, A noise measurement step for measuring a noise level of a broadcast wave or a signal after the detection,
When the reception state of the receiving broadcast station deteriorates, the received AF station receives a broadcast of an AF station in the received AF list, and the received electric field strength of the original receiving broadcast station is smaller than a predetermined strength value , and the receiving AF station If the noise level of the received signal is equal to or lower than a predetermined level value , it is determined whether or not the PI data of the received AF station broadcast matches the PI data of the original received broadcast. A receiving method of an RDS receiver, wherein the receiving AF station broadcast is continuously received regardless of whether or not the received electric field strength of the broadcast of the AF station is smaller than the predetermined intensity value . When a reception state of the receiving broadcast station deteriorates, a broadcast of a certain AF station in the received AF list is received, and if the received electric field strength of the original reception broadcast station is equal to or higher than the predetermined strength value , the reception is in progress The received electric field strength of the AF station is greater than or equal to the predetermined intensity value , the noise level of the received signal is less than or equal to the predetermined level value , and the PI data of the AF station broadcast being received and the PI data of the original received broadcast are 4. The reception method of an RDS receiver according to claim 3, wherein the broadcast of the receiving AF station is continuously received only when the two match.

Images