JPH06204926A - Double tuner diversity rds receiver - Google Patents

Abstract

PURPOSE:To provide a double tuner diversity RDS receiver which can decide an accurate receiving state. CONSTITUTION:A double tuner diversity RDS receiver measures for a fixed time the average value of the S meter signal voltage as well as the noises of both S meters 1 and 2 produced by two tuners 100 and 200 while these tuners are receiving the same frequency. So that the difference of gains is corrected between both antennas 1 and 11. Then the average value of the S meter noises and signal voltage of both meters 1 and 2 are measured in an AF search processing state. The value corrected by the corrected gain difference is defined as a standard of comparison. Thus the frequency receiving states are compared with each other based on the value obtained by correcting the difference of gains between both antennas 1 and 11. Then an accurate receiving state is decided.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-tuner diversity RDS receiver and, more particularly, to a two-tuner diversity RDS receiver that enables accurate reception state determination. 2. Description of the Related Art RDS (Radio Data System), which digitally multiplexes music selection and program identification data into FM radio broadcast signals and provides various services to drivers, has been put to practical use in Europe. In the future, it is expected to spread worldwide, not only in the European region. Radio waves of RDS transmitted from a broadcasting station are received by an in-vehicle tuner. For example, if the receiving station radio wave weakens due to a change in the location while driving, the radio waves of the same program can be received one after another. It has such a search function. Typical RDS services include a PI (program identification) service that identifies the country, the receiving area, and the program name of the broadcasting station, and a PS (displaying the receiving station name) service that displays the receiving broadcasting station name on the tuner display. , The above-mentioned AF (similar program broadcast frequency list) service for displaying frequencies of other broadcasting stations broadcasting the same program, and TP service for identifying stations broadcasting traffic information. As a receiver for receiving such a broadcast, there is a two-tuner diversity RDS receiver which has two tuners and selects and receives a tuner having a good radio wave reception state. In the conventional RDS receiver with two tuner diversity, when one tuner searches for an AF frequency while one tuner continues to receive signals as it is, the S of two tuners is used in order to search for a frequency in a better reception state. The meter (electric field strength) or S meter noise is compared to determine whether or not the frequency can be moved to that frequency. As described above, in the conventional 2-tuner diversity RDS receiver, the AF frequency is searched for based on the comparison result based on the S meter noise or the like obtained from the two tuners. ing. However,
At the time of comparison, there is a problem in that an incorrect determination may occur in one comparison due to fluctuations in the reception state, and an accurate reception state cannot be determined due to a difference in sensitivity between antennas connected to two tuners. there were. Therefore, an object of the present invention is to provide a two-tuner diversity RDS receiver capable of accurately determining the reception state. In order to solve the above-mentioned problems, a two-tuner diversity RDS receiver according to the present invention has two tuners and selects and receives a tuner having a good reception state. In the RDS receiver, the demodulation means for demodulating RDS data from the reception signals received by the two tuners, the detection means for detecting S meter noise or the S meter signal indicating the reception electric field strength, and the two tuners are the same. Averaging means for outputting the average of the S meter noise or S meter signal detected by the detecting means while receiving the frequency; and the S meter noise or S meter signal average value of the two tuners obtained by the averaging means. Memory means for storing the difference as a correction value,
When one tuner searches for an alternative frequency (AF) of the same broadcast content based on the data, S-meter noise at the frequency currently being received or the average value of the S-meter signal and S-meter noise or S-meter at the AF frequency The reference value is a value obtained by adding the correction value to the average value of the signal. According to the present invention, in the two-tuner diversity RDS receiver, while two tuners are receiving the same frequency, the S meter noise and the S-meter noise obtained by the respective tuners can be obtained.
The average of the meter signal voltage is measured for a certain period of time to correct the gain difference of the antenna, and the S meter noise of each tuner and the average value of the S meter signal voltage are measured during the AF search processing, and the values are corrected by the above correction values. By using as a comparison reference, the reception states of the respective frequencies are compared with the values obtained by correcting the gain differences of the antennas, and it is possible to accurately determine the reception state. Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of a two-tuner diversity RDS receiver according to the present invention. The present embodiment has two tuner units 100 and 200, and each tuner unit has an antenna 1, 11 and
Front ends 2 and 12, FM detection circuits 3 and 13,
Stereo demodulation circuits 4 and 14, PLL circuits 5 and 15,
S meter noise (SN) detection circuit 6, 16 and RDS
The data demodulating circuits 7 and 17 are provided, and the microcomputer 8 receives the data obtained from these and demodulates the switch 9 so as to select a better tuner. The signal received by the antenna 1 is tuned to an arbitrary frequency in cooperation with the operation of the PLL circuit 5 in the front end 2. The intermediate frequency (I / F) signal output from the front end 2 is FM-detected by the FM detection circuit 3.
At this time, an S meter signal corresponding to the level of the I / F signal (corresponding to the electric field strength) is obtained and supplied to the S meter noise detection circuit 6 and the microcomputer 8. An example of the configuration of the S meter noise detection circuit 6 (16) is shown in FIG. In FIG. 2, the input S
The meter signal is DC by the low pass filter (LPF) 61.
A component is extracted, and a bandpass filter (BPF) 62 extracts a noise component such as multipath or adjacent interference,
After being amplified to a predetermined level by the amplifier 63, the detector 64
Is detected by. The differential amplifier 65 obtains a difference component between the thus obtained DC component and a noise component such as multipath and outputs it as an S meter noise (SN) signal. An example of the S meter input signal and the S meter noise component signal input to the circuit as shown in FIG. 2 is shown in FIG. 3. The S meter noise level is lowered by the noise component, and the S meter noise level is reduced except the noise. It is shown to operate in the same manner as. The microcomputer 8 receives the S meter signal and the S meter noise signal, and performs the processing described below. FIG. 4 shows a flowchart of the procedure of the averaging process. First, it is determined whether or not the two tuners are receiving the same frequency (step S1). If not receiving, the process ends. If receiving, the average of the S meter noise voltage of each tuner is calculated. Measurement is performed for a fixed time (step S2). Next, the difference between the obtained average values is calculated and stored in the memory as a correction value (step S3). In this processing, for example, when the average values of the S meter noise voltages of the tuners 100 and 200 are SN1 and SN2, respectively, the correction value SN is obtained by SN = SN1-SN2. This difference SN is caused by the gain difference of the antenna. Next, the AF search process performed by the microcomputer will be described with reference to the flowchart shown in FIG. A
The F search is the RD obtained by the RDS data demodulation circuit 7.
The AF (alternative frequency) included in the S data is searched, and if the reception state is better than the current frequency, the function is to move. When the tuner has two tuners, one tuner 100 is used.
Allows the other tuner 200 to perform an AF search while receiving the currently received frequency as it is.
Now, in FIG. 5, AF data is received and it is checked whether or not the S meter is above a certain standard (step S11). This is because if the electric field strength is not large enough, the receiving sensitivity is poor and the RDS data cannot be demodulated sufficiently.
This processing is performed because the AF search speed becomes very slow when the number of AFs is large. If it is not above the standard, the processing is ended, and if it is above the standard, then the broadcast station code (PI code) in the RDS data is checked to see if it has the same content (OK) (step S12).
If it is not OK, the processing is terminated. If it is OK, then the average of the S meter noise voltage of each tuner is measured for a certain period of time, and the S meter noise voltage of the tuner unit 200 on the search side is set to the above. Correction is performed using the correction value SN, and the S meter noise voltages of the tuner units 100 and 200 are compared (step S13). As a result of the comparison, if the S-meter noise voltage of the searched station (frequency) is larger, the S-meter noise voltage is moved to that frequency (step S15). For example, assuming that the average values of the tuner units are SN1 'and SN2', respectively, the corrected values of the tuner units 100 and 200 are: tuner unit 100: SN correction value = SN1 'tuner unit 200: SN correction value = SN2' + SN ( Search side) By such processing, it becomes possible to compare the reception states of the respective frequencies with the values obtained by correcting the gain differences of the antennas. After moving to a frequency with a good reception state by the AF search, both tuners receive the same frequency, and as a diversity operation, the S meter noise voltage of each tuner is compared and the larger audio signal is received. The signal is selectively output by controlling the switch 9. In the above-mentioned embodiment, the S meter noise voltage is used to judge the reception state.
Needless to say, the same processing can be performed using the S meter signal without this detection circuit. In this case, an erroneous determination may occur when multipath noise or the like occurs. As described above, in the two-tuner diversity RDS receiver according to the present invention, while two tuners are receiving the same frequency, the S-meter noise and the S-meter signal voltage of each tuner are averaged. Is measured for a certain period of time to correct the gain difference of the antenna, and during AF search processing, the S meter noise of each tuner and the average of the S meter signal voltage are measured for a certain period of time, and the value corrected by the above correction value is used as a comparison reference. Therefore, the reception state of each frequency can be compared with the value obtained by correcting the gain difference of the antenna.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration block diagram showing an embodiment of a two-tuner diversity RDS receiver according to the present invention. FIG. 2 is a block diagram showing a configuration example of an S meter noise detection circuit in FIG. FIG. 3 is a diagram showing input / output waveforms of the S meter noise detection circuit shown in FIG. FIG. 4 is a flowchart showing an averaging processing procedure in the embodiment of the present invention. FIG. 5 is a flowchart showing an AF search processing procedure according to the embodiment of the present invention. [Explanation of Codes] 1,11 Antenna 2,12 Front End 3,13 FM Detection Circuit 4,14 Stereo Demodulation Circuit 5,15 PLL Circuit 6,16 S Meter Noise Detection Circuit 7,17 RDS Data Demodulation Circuit 8 Microcomputer 9 Switch 100,200 tuner section

Claims (1)

Claim: What is claimed is: 1. An RDS receiver having two tuners for selecting and receiving a tuner in a good reception state, and a demodulation means for demodulating RDS data from a reception signal received by the two tuners, Detecting means for detecting S-meter noise or S-meter signal indicating received electric field strength, and average for outputting an average of S-meter noise or S-meter signal detected by the detecting means while the two tuners are receiving the same frequency. Means and memory means for storing the difference between the S-meter noise or the S-meter signal average value of the two tuners, which is obtained by the averaging means, as a correction value, and one of the tuners is based on the RDS data. When searching for an alternative frequency (AF) of the same broadcast content, the S meter noise or the average value of the S meter signal at the frequency currently being received and the AF frequency 2 tuner diversity RDS receiver, characterized in that the reference value the value of the plus correction value to the average value of the S meter noise or S meter signal by the number.