JP2011004108A - Rds reception device - Google Patents

Abstract

To provide an RDS receiver capable of improving the PI acquisition rate even when an alternative station includes an adjacent station having a high electric field strength.
An RDS demodulator 200 that demodulates a signal detected by an FM detector 180 to obtain an alternative station PI code, and an AGC unit 160 when the RDS demodulator 200 obtains an alternative station PI code. In the RDS receiving apparatus 100 including the control unit 230 that defines the output level of the mixer unit 150 that starts the operation, when the RDS data of the alternative station is acquired in the mute state, the AGC operation start level is normally received. Since it is changed to the second AGC operation start level FS2 higher than the first AGC operation start level FS1, the PI acquisition rate can be improved even when the electric field strength of the adjacent interfering wave is large.
[Selection] Figure 1

Description

  The present invention relates to an RDS receiver that receives RDS data.

  A radio data system (RDS) is a service that, in FM broadcasting, multiplexes additional information regarding broadcast stations and broadcast contents as RDS data into FM broadcast signals and provides them to the FM broadcast receiving side. An example of the service is to display the name of the currently selected broadcasting station on an FM broadcast receiving apparatus (hereinafter referred to as “RDS receiving apparatus”). In recent years, FM broadcast receivers that can receive RDS data have been widely used in Europe, the United States, and the like.

  In RDS, the same broadcast content is broadcast in a plurality of frequency bands. For example, even if the reception state of an RDS receiver mounted on a vehicle deteriorates due to the movement of the vehicle, the RDS receiver is a broadcasting station that broadcasts the same broadcast content at a frequency different from the frequency being received (hereinafter “ Search for an alternative broadcasting station with good reception quality from the "alternative station") and switch. At this time, the RDS receiver switches between broadcast stations based on the RDS data.

  The RDS data includes an AF (Alternative Frequency) list that describes the frequency at which the alternative station is broadcast (hereinafter referred to as “alternative frequency”) and the PI (Program Identification) code of the alternative station. The PI code is a code for identifying a broadcasting station, and the same PI code is assigned to broadcasting stations that broadcast the same broadcast content. The RDS receiving apparatus acquires an AF list in advance from the FM broadcast being received, and can switch to an alternative station with good reception quality based on the AF list when the reception quality of the signal deteriorates.

  The RDS receiver performs an AF operation when switching to an alternative station. The AF operation is an operation of searching for an alternative frequency with good signal reception quality from the alternative frequencies described in the AF list and switching to the searched alternative frequency. The AF operation is composed of two processes of “AF check” and “PI check”. “AF check” is a method for detecting whether the electric field strength of an FM broadcast signal transmitted at an alternative frequency is greater than or equal to a threshold, and whether or not RSD data can be acquired from an alternative station. It is a process to confirm. The “PI check” is a process for confirming whether the PI code of the currently receiving broadcast station matches the PI code of the alternative station described in the AF list.

  Since it is necessary to receive an alternative station during the “PI check”, reception of the FM broadcast signal being received is interrupted. At this time, since the sound is interrupted, it is necessary to complete the PI check in a very short time so that the user does not notice it. Therefore, it is desired to improve the PI code acquisition rate in order to complete the PI check time in a short time.

  The conventional RDS receiving apparatus controls the variable IF filter, removes the influence of adjacent interference at the IF stage, and improves the PI code acquisition performance in the adjacent interference environment (for example, Japanese Patent Application No. 2008 of unpublished company application). -041887).

  However, in the RDS receiver described in Patent Document 1, when the electric field strength of the broadcasting station adjacent to the alternative station is large, the AGC unit provided in the front end unit controls the variable attenuator and the RF amplifier to output the RF signal. In order to attenuate, the signal of the alternative station is also suppressed in the RF stage, and there is a problem that the PI code acquisition rate is lowered.

  An object of the present invention is to provide an RDS receiver capable of reducing suppression of a signal of an alternative station and improving a PI code acquisition rate even when a signal level of a broadcasting station adjacent to the alternative station is high. To do.

  The RDS receiver of the present invention is an operation for searching for an alternative frequency with good signal reception quality from among the alternative frequencies described in the AF list and switching to the searched alternative frequency with good reception quality. An RDS receiver that performs an operation, wherein a variable attenuator unit that attenuates a received signal, an RF filter unit that attenuates a signal having a frequency outside the FM band among signals output from the variable attenuator unit, and the RF filter unit An RF amplifier unit for amplifying the signal output from the RF amplifier, a mixer unit for converting the signal output from the RF amplifier unit into an intermediate frequency signal, an AGC operation start level which is a predetermined level, and an output level of the mixer unit An AGC unit that adjusts the gains of the variable attenuator unit and the RF amplifier unit so as to maintain the AGC operation start level at the AGC operation start level; A control unit that controls each unit, and the control unit has a configuration that performs control to change the AGC operation start level when switching to an alternative frequency with good reception quality during the AF operation. .

  With this configuration, when the RDS demodulator obtains the PI code of the alternative station, the AGC operation start level is changed by adjusting the gain of the variable attenuator or the RF amplifier by controlling the AGC unit. The acquisition rate can be further improved.

  According to the present invention, the PI code acquisition rate is improved even when there is an adjacent station having a large electric field intensity by controlling the AGC unit when acquiring the PI code of the alternative station and adjusting the gains of the variable attenuator and the RF amplifier. be able to.

The system block diagram which shows the structure of the RDS receiver which concerns on one embodiment of this invention The figure which shows an example of the operation content of the AGC part in this Embodiment The figure which shows an example of the operation content of the AGC part in this Embodiment The figure which shows an example of the operation content of the AGC part in this Embodiment The figure which shows an example at the time of shifting the operation start level of the AGC part in this Embodiment The flowchart figure which shows the flow of operation | movement of the RDS receiver in this Embodiment. The flowchart figure which shows the flow of AF operation | movement in this Embodiment The figure which shows an example of the relationship between the AGC operation | movement start level and the bit error rate of RDS data in this Embodiment

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram showing a configuration of an RDS receiving apparatus according to an embodiment of the present invention.

  In FIG. 1, an RDS receiver 100 includes an antenna unit 110, a variable attenuator unit 120, an RF filter unit 130, an RF amplifier unit 140, a mixer unit 150, an AGC (Auto Gain Control) unit 160, a variable IF filter unit 170, and FM detection. Unit 180, adjacent noise detection unit 190, RDS demodulation unit 200, ROM (Read Only Memory) 210, RAM (Random Access Memory) 220, control unit 230, MPX (multiplex) demodulation unit 240, mute unit 250, speaker unit 260, A display device 270 and an operation unit 280 are included.

  The antenna unit 110 receives FM-multiplexed FM broadcast signals.

  The variable attenuator unit 120 attenuates the FM broadcast signal received by the antenna unit 110. The amount of attenuation of the signal level in the variable attenuator unit 120 is variable, and the amount of attenuation is controlled by the AGC unit 160.

The RF filter unit 130 is a filter that attenuates frequency signals outside the FM band and passes only frequency signals within the FM band.
The RF amplifier unit 140 amplifies the signal to a sufficient voltage so that the frequency signal in the FM band that has passed through the RF filter unit 130 is not buried in noise by the mixer unit 150 at the subsequent stage. The mixer unit 150 converts an FM broadcast signal of a broadcast station designated by the user or a predetermined broadcast station out of the signals output from the RF amplifier unit 140 into an intermediate frequency (IF) signal.

When the output of the mixer unit 150 exceeds a predetermined level, the AGC unit 160 controls the gains of the variable attenuator unit 120 and the RF amplifier unit 140 to keep the output level of the mixer unit 150 at a predetermined level. This predetermined level is called an AGC operation start level, and the AGC operation start level is controlled by the control unit 230.
The variable IF filter unit 170 band-limits the intermediate frequency signal converted by the mixer unit 150 with a predetermined filter bandwidth, and outputs a filter output signal. The filter bandwidth of the variable IF filter unit 170 is variable and is controlled by the control unit 230.

  The FM detection unit 180 performs FM detection on the filter output signal output from the variable IF filter unit 170 and outputs a detection signal. Further, the FM detection unit 180 detects the electric field strength of a detection signal (hereinafter referred to as “desired wave”) in a frequency band broadcast by a predetermined broadcasting station during the AF operation of the RDS receiver 100.

  The adjacent noise detection unit 190 detects the electric field strength of adjacent noise (hereinafter referred to as “adjacent noise value” as appropriate) from the detection signal output by the FM detection unit 180. Hereinafter, the adjacent noise is not limited to noise due to FM broadcast signals of other adjacent broadcast stations, but refers to noise existing in the vicinity of the desired wave.

  The adjacent noise detection unit 190 includes a band pass filter (BPF) unit 191 and an electric field strength measurement unit 192. The band-pass filter unit 191 extracts a detection signal in a frequency band (hereinafter referred to as “noise detection band”) that is a target for detection of adjacent noise from the detection signal output by the FM detection unit 180.

  The electric field strength measuring unit 192 measures the electric field strength of the detection signal in the noise detection band, and outputs the measurement result as an adjacent noise value.

  The RDS demodulation unit 200 performs demodulation and decoding processing for extracting RDS data from the detection signal output from the FM detection unit 180. The RDS data includes an AF list that lists alternative frequencies and a PI code.

  The ROM 210 stores various control programs executed by the control unit 230 in advance. The control unit 230 controls each unit of the RDS receiver 100 by reading the control program stored in the ROM 210 into the RAM 220 and executing it. The ROM 210 also has a determination reference value for selecting whether or not to start the AF operation, a determination reference value for selecting whether or not to perform the PI check, the AGC operation start level during normal reception, and the PI. The AGC operation start level at the time of check is stored.

  2 to 5 show an example of the operation content of the AGC unit 160. As shown in FIG. 2, the center frequency of the desired wave 311 is the alternative frequency f1, and the RDS data is broadcast in bands centering around two frequencies (f1 + 57 kHz, f1-57 kHz) of plus and minus 57 kHz of the alternative frequency f1. An RDS subcarrier 312 that is a broadcast wave is located. FS1 is the AGC operation start level at the time of normal reception and is the first AGC operation start level. This AGC operation start level is defined by the control unit 230. In FIG. 2, since the electric field strength of the desired wave 311 is lower than the AGC operation start level FS1, the AGC unit 160 does not operate, and thus there is no signal attenuation in the variable attenuator unit 120 and the RF amplifier unit 140.

  FIG. 3 shows an operation when the electric field intensity of the desired wave 311 exceeds the AGC operation start level FS1. Since the electric field strength of the desired wave 311 exceeds the AGC operation start level FS1, the AGC unit 160 adjusts the gains of the variable attenuator unit 120 and the RF amplifier unit 140 so that the electric field strength does not exceed FS1, and attenuates the signal. Let A portion 313 indicates the amount of signal attenuation due to the operation of the AGC unit 160. The signal level of the subcarrier 312 is also attenuated similarly to the desired wave 311.

  FIG. 4 shows a case where an interference wave 314 adjacent to the desired wave 311 exists. In FIG. 4, the electric field strength of the desired wave 311 is lower than the AGC operation start level FS1, but the electric field strength of the disturbing wave 314 is higher than the AGC operation start level FS1. In this case, the AGC unit 160 operates so as to attenuate the signal by an amount (part 315) in which the electric field strength of the interference wave 314 exceeds the AGC operation start level FS1. At this time, since the variable attenuator unit 120 and the RF amplifier unit 140 perform gain adjustment for the entire frequency band, the signal level of the desired wave 311 is also attenuated by the same amount (part 316) as the interference wave. Become. Therefore, when the electric field strength of the interference wave 314 is high, the signal level of the desired wave is greatly suppressed, and the signal level of the RDS subcarrier 312 of the desired wave 311 is reduced, so that the PI code acquisition rate is deteriorated. End up.

  FIG. 5 shows a case where the AGC operation start level FS1 is shifted to a higher level and the second AGC operation start level FS2. By raising the AGC operation start level to FS2, the AGC unit 160 does not operate at the electric field strength of the interference wave, so that the signal attenuation in the variable attenuator unit 120 and the RF amplifier unit 140 is eliminated. Therefore, the signal of the desired wave that was suppressed when the AGC operation start level was FS1 is no longer attenuated, and the PI code acquisition rate of the desired wave is not deteriorated.

  Next, the operation of the RDS receiver 100 in the embodiment of the present invention will be described.

  FIG. 6 is a flowchart showing an operation flow of the RDS receiver 100.

First, in step S1100, the control unit 230 determines whether or not an FM broadcast viewing start has been instructed by turning on the power of the RDS receiver or a user operation of the operation unit 280. At this time, if it is determined that an instruction to start viewing of FM broadcast is given (S1100: YES), control unit 230 advances the process to step S1200. Note that, as an initial state, the control unit 230 controls the mute unit 250 so that the signal level of the audio signal output from the RDS receiving apparatus 100 to the outside is zero.

  In step S1200, since the frequency of the FM broadcast signal received last is stored in the ROM 210, the control unit 230 reads out the frequency and sets the read frequency as the desired station desired wave f0.

  In step S1300, the control unit 230 starts the tuning operation of the own apparatus and tunes to the desired station desired wave f0.

  In step S1400, control unit 230 causes FM detection unit 180 to measure the electric field strength of the desired wave of own station desired wave f0, and adjacent noise detection unit 190 uses the electric field of the adjacent noise of own station desired wave f0. Measure strength. At this time, the control unit 230 stores the measurement result of the electric field strength of the adjacent noise of the desired wave f0 of the own station in the RAM 220.

In step S1500, control unit 230 determines whether or not to perform the AF operation based on the electric field strength of own station desired wave f0 and the adjacent noise electric field strength of own station desired wave f0 measured in step S1400. .
As a result of the determination in step S1500, when the AF operation is executed (S1500: YES), the control unit 230 advances the process to step S1600. If the result of determination in step S1500 is that the AF operation is not executed (S1500: NO), control unit 230 advances the process to step S1700.

  In step S1600, control unit 230 performs an AF operation. Details of the AF operation will be described later.

  In step S <b> 1700, control unit 230 determines whether or not FM broadcast viewing / listening is instructed by powering off RDS receiver 100 or a user operation on operation unit 280. At this time, when it is determined that the end of viewing of the FM broadcast is not instructed (S1700: NO), the control unit 203 advances the process to step S1800.

  In step S1800, control unit 230 determines whether or not an instruction to change a broadcasting station to be viewed is given by a user operation of operation unit 280 or the like. If the result of this determination is that there is no instruction to change the broadcast station (S1800: NO), the process returns to step 1400. If a broadcast station change is instructed (S1800: YES), the process proceeds to step S1900. Thereby, the measurement of the electric field strength and the AF operation as necessary are repeated.

  When the broadcast station change is instructed in step S1800 and the process proceeds to step S1900, the control unit 230 sets the frequency of the broadcast station instructed as the change destination to a new desired wave f0, and then performs the process. Is returned to step S1300. Thereby, viewing of the broadcast of the alternative station is started.

  On the other hand, when it is instructed to end viewing of the FM broadcast in step S1700 (S1700: YES), control unit 230 advances the process to step S2000.

  When the process proceeds to step S2000, the control unit 230 stores the frequency of the FM broadcast signal received last in the ROM 210, and the series of processes ends.

  Next, details of the AF operation will be described with reference to FIG. FIG. 7 is a flowchart showing the flow of the AF operation, and corresponds to the processing in step S1600 of FIG.

  First, in step 1601, the control unit 230 controls the operation of the mute unit 250 to reduce the signal level of the audio signal to a level that the user cannot recognize by hearing, thereby muting the output audio.

In step S1602, the control unit 203 tries to acquire the AF list of the local station, and determines whether or not an alternative frequency is described in the acquired AF list.
At this time, if the AF list of the own station can be acquired and an alternative frequency is described in the acquired AF list (S1602: YES), the control unit 230 advances the process to step S1603. Proceed. The acquisition of the AF list is performed, for example, when the corresponding AF list is stored in the ROM 210 and read from the ROM 210, and when the corresponding AF list is not stored in the ROM 210, the RDS demodulator 200 obtains the AF list from the RDS data. Extraction may be performed. Each time the control unit 230 acquires the AF list from the RDS data, it is desirable to store the acquired AF list in the ROM 210.

  When the process proceeds to step S1603, the control unit 230 sets a value “0” to the initial value of the variable L that indicates what number of alternative frequencies in the AF list is to be processed.

  In step S1604, the control unit 230 sets the Lth alternative frequency in the AF list as the alternative frequency f1 to be processed.

  Thereafter, in step S1605, the control unit 230 sets the filter bandwidth of the variable IF filter unit 170 to a bandwidth that can detect the adjacent noise value of the alternative frequency performed in step S1607 of the post-processing.

  After the processing in step S1605, in step S1606, the control unit 230 performs control for tuning to the alternative frequency f1.

  In step S1607, the control unit 230 measures the electric field strength of the desired wave at the alternative frequency f1, and measures the electric field strength of the adjacent noise at the alternative frequency f1 using the adjacent noise detection unit 190. The result is stored in the RAM 220.

In step S1608, the control unit 230 performs an AF check that is a determination as to whether or not to switch to the alternative station having the alternative frequency f1. Specifically, the control unit 230 determines whether or not to perform the PI check based on the electric field strength of the alternative frequency f1 and the electric field strength of adjacent noise of the alternative frequency f1 measured in step S1607.
If the control unit 230 determines not to perform the PI check, that is, determines that switching to reception of the alternative frequency f1 is not performed (S1608: NO), the process proceeds to step S1609.

In step S1609, the control unit 230 determines whether the variable L has exceeded the number N of alternative frequencies described in the AF list, that is, whether there is an unprocessed alternative frequency.
At this time, if the variable L has not yet exceeded the number N (S1609: NO), the control unit 230 advances the process to step S1610.

  Then, in step S1610, control unit 230 increases variable L by value 1, and then returns the process to step S1604. As a result, while the switching destination is not determined, while the switching destination candidates remain, AF checks are sequentially performed on the alternative frequencies described in the AF list.

  On the other hand, when it is determined to perform the PI check, that is, when it is determined to switch to reception of the alternative frequency f1 (S1608: YES), the control unit 230 advances the process to step S1611.

In step S1611, the control unit 230 controls the AGC unit 160, and shifts the AGC operation start level from FS1 to FS2 as shown in FIG. That is, the control unit 230 performs the AGC operation so that the PI code acquisition rate can be suppressed even when the electric field level of the adjacent interfering wave is large when “PI check is in progress” in a mute state and no audio output. Set the start level to FS2.
Normally, when the signal level received by the antenna unit 110 is too high, distortion occurs in the RF amplifier unit 140 and the mixer unit 150. For this reason, the gain of the variable attenuator unit 120 and the RF amplifier unit 140 is adjusted to attenuate the signal so that noise is not heard by the user. In this embodiment, the AGC operation start level during normal reception is set to FS1 that does not generate audible noise, but it is necessary to consider noise that is audible in the mute state during PI check. Therefore, the AGC operation start level is set to FS2 that is high enough to suppress deterioration of the PI code acquisition rate.

  In step S1612, the control unit 230 controls the variable IF filter unit 170. That is, the control unit 230 sets the filter bandwidth of the variable IF filter unit 170 to an optimum bandwidth that can suppress the degradation of the reception quality of the alternative frequency f1 due to the adjacent noise according to the adjacent noise value measured in step S1607. To do.

Then, after acquiring the PI code from the FM broadcast signal having the alternative frequency f1 in step S1613, the control unit 230 determines whether or not the acquired PI code matches the PI code of the desired station wave described in the AF list. A PI check is performed to determine whether or not.
If the PI code cannot be acquired, or if the acquired PI code does not match the PI code of the AF list (S1613: NO), the control unit 230 advances the process to step S1609. . Thereby, it can transfer to the process to another switching destination candidate.
On the other hand, if the PI code can be acquired and the acquired PI code matches the PI code of the AF list (S1613: YES), the control unit 230 advances the process to step S1614.

In step S <b> 1614, control unit 230 sets AGC operation start level FS <b> 1 set at the time of normal audio output to AGC unit 160.
In step S1615, the control unit 230 controls the variable IF filter unit 170 again for normal audio output.

  In step S <b> 1616, the control unit 230 controls the mute unit 250 to increase the signal level of the audio signal to a level that can be recognized by the user.

  On the other hand, when the variable L exceeds the number N of alternative frequencies described in the AF list, that is, when the switching destination is not finally determined (S1609: YES), the control unit 230 advances the process to step S1617. .

In step S1617, the control unit 230 sets the operation start level of the AGC unit 160 to FS1 for normal reception in the same manner as in step 1614, for the desired wave of its own station.
Furthermore, in step S1618, the control unit 230 controls the variable IF filter unit 170 again for normal audio output.

  In step S1619, the control unit 230 retunes to the desired station desired wave f0, and the process proceeds to step S1616.

  If the AF list of the own station cannot be acquired, or if an alternative frequency is not described in the acquired AF list (S1602: NO), the control unit 230 proceeds directly to step S1616.

  In this way, the control unit 230 performs control to change the AGC operation start level during the PI check so that the PI code acquisition rate can be improved.

  Hereinafter, experimental data indicating that the PI acquisition rate is improved by using the RDS receiver 100 according to the present embodiment will be described.

  FIG. 8 is a diagram showing the relationship between the AGC operation start level and the RDS bit error rate. In the figure, the horizontal axis indicates the electric field strength of adjacent interference waves, and the vertical axis indicates the RDS bit error rate. The electric field strength of the desired wave being received is 40 dBuV. A curve 410 is an RDS bit error rate when the AGC operation start level is FS1 which is a setting at the time of normal reception, and a curve 420 is an RDS bit error rate when the AGC operation start level is a setting of FS2 during PI check.

  As can be seen from FIG. 8, even when the electric field strength level of the adjacent interfering wave is large, when the AGC operation start level is FS2, the bit error rate is lower than in the case of FS1. That is, it can be said that the PI code acquisition rate is high.

  In the above description, the FS2 level is set to a level at which the PI code acquisition rate is the highest. However, when the FS2 level is set to an excessive level, the FS2 level is input to the RF amplifier unit 140 and the mixer unit 150. Since the maximum signal level is increased, the generated distortion is increased, and the PI code acquisition rate is deteriorated, the level of FS2 is determined by taking into account the distortion generated in the RF amplifier unit 140 and the mixer unit 150 and the RDS bit error rate. It is necessary to measure and set to an optimum level at which the PI code acquisition rate is the highest.

  As described above, according to RDS receiver 100 according to the present embodiment, when acquiring RDS data of an alternative station in a mute state, the AGC operation start level is changed to a level higher than the level at the time of normal reception. Therefore, even when the electric field strength of the adjacent interfering wave is large, the PI acquisition rate can be improved.

  The RDS receiver according to the present invention is useful as an RDS receiver capable of improving the PI code acquisition rate even when there is an adjacent interfering wave having a high electric field strength.

DESCRIPTION OF SYMBOLS 100 RDS receiver 110 Antenna part 120 Variable attenuator part 130 RF filter part 140 RF amplifier part 150 Mixer part 160 AGC part 170 Variable IF filter part 180 FM detection part 190 Adjacent noise detection part 191 Band pass filter part 192 Electric field strength measurement part 200 RDS demodulator 210 ROM
220 RAM
230 Control Unit 240 MPX Demodulation Unit 250 Mute Unit 260 Speaker Unit 270 Display Device 280 Operation Unit

Claims (6)

An RDS receiver that performs an AF operation that searches for an alternative frequency with good signal reception quality from among alternative frequencies described in an AF list and switches to the searched alternative frequency with good reception quality. And
A variable attenuator that attenuates the received signal;
An RF filter unit for attenuating a signal having a frequency outside the FM band among the signals output from the variable attenuator unit;
An RF amplifier unit for amplifying the signal output from the RF filter unit;
A mixer unit for converting a signal output from the RF amplifier unit into an intermediate frequency signal;
An AGC unit that sets an AGC operation start level that is a predetermined level and adjusts the gains of the variable attenuator unit and the RF amplifier unit so as to maintain the output level of the mixer unit at the AGC operation start level;
A control unit that controls each unit of the device itself,
The RDS receiving apparatus, wherein the control unit performs control to change the AGC operation start level when switching to an alternative frequency with good reception quality during the AF operation. The AGC unit sets a first AGC operation start level and a second AGC operation start level larger than the first AGC operation start level to be switchable,
The first AGC operation start level is set during normal reception, and the second AGC operation start level is set when switching to an alternative frequency with good reception quality during the AF operation. Item 4. The RDS receiver according to Item 1.   A variable IF filter unit with a variable filter bandwidth that outputs a filter output signal by limiting the intermediate frequency signal output by the mixer unit with a predetermined filter bandwidth, and a filter output output by the variable IF filter unit An FM detector for FM detection of the signal, an RDS demodulator for demodulating the signal detected by the FM detector to obtain the PI code of the alternative station, and an alternative station from the signal detected by the FM detector An adjacent noise detection unit that extracts a signal of a station adjacent to the signal and detects an adjacent noise value of the signal, and an electric field strength measurement that measures the electric field strength of a receiving station or an alternative station from the signal detected by the FM detection unit The RDS receiver according to claim 1, further comprising:   An MPX demodulator that demodulates the detection signal output by the FM detector and outputs a voice signal; and the voice signal output by the MPX demodulator when the RDS demodulator acquires the PI code of the alternative station. 4. The RDS receiver according to claim 3, further comprising a mute unit for muting and a speaker unit for outputting the audio signal as audio. The control unit sets the first AGC operation start level in the AGC unit when outputting the sound of the receiving broadcast station, and the audio output is a mute unit in order to acquire the PI code of the alternative station 5. The RDS receiving apparatus according to claim 4, wherein the second AGC operation start level is set when muted at.   The first AGC operation start level is an AGC operation start level at which distortion or noise does not appear in the output sound when the sound of the receiving broadcasting station is being output. 6. The RDS receiver according to any one of 6.