JPH05122014A - Automatic follow-up system of radio receiver - Google Patents

Abstract

PURPOSE:To start an automatic follow-up operation at an optimum threshold level in accordance with a radio reception system. CONSTITUTION:A threshold level value E1 when a radio reception is performed in a first radio reception system by a first radio reception part 23 is made smaller than a value E2 when the radio reception is performed in a second radio reception system by a second radio reception part 24. A controller 35 (automatic follow-up processing part) monitors whether the radio reception is performed by either one of the first or the second radio reception system based on a switch signal SWS. The value in accordance with a radio reception system to be being received is defined as a threshold level Eth. When a receiving electric field intensity E to be outputted from a signal meter 33 becomes below the threshold level value, an automatic follow-up operation is started based on RDS data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to first and second radio receiving systems and an automatic tracking system of a radio receiver having an automatic tracking function, and particularly to an automatic tracking operation in the first and second radio receiving systems. The present invention relates to an automatic tracking method in which the starting threshold level value is changed.

[0002]

2. Description of the Related Art In car radios, in addition to being able to easily obtain traffic information, it is required to have an advanced tuning function. In particular, in Europe where FM broadcasting, which has a relatively small service area, is the main body of radio broadcasting services, and the ratio of car radio broadcast reception is high, this requirement is strong and RDS (radio data system) has been put to practical use. This RDS
According to the, the message related to the FM broadcast being received
For example, a frequency list (AF list) of the same program broadcasting station, a program identification code, etc. are superimposed on the FM broadcasting signal and transmitted. For this reason, in the RDS, when the received electric field strength currently being received falls below a predetermined threshold level, the AF list is demodulated, and the received electric field strength is sequentially tuned to each AF station on the AF list. And tune to the frequency of the AF station with the highest received electric field strength to maintain a good reception state (automatic tracking). still,
The reception electric field strength of each AF station is checked for 10 msec by tuning the front end to the AF station frequency and muting during that period. Since the muting time is short, the broadcasting from the original receiving station is broadcast. Can be listened to without any discomfort.

In the automatic tracking process, it takes about 1 to 2 minutes to check the received electric field strengths of all AF stations and switch to the same program broadcasting station having a large received electric field strength. Therefore, if the threshold level at which the automatic tracking process is started is low, the signal must be received in a bad state for 1 to 2 minutes until the automatic tracking process is completed. Therefore, it is necessary to start the automatic follow-up operation before the reception state deteriorates, that is, from a reception state that is somewhat good. In other words, it is necessary to increase the threshold level at which the automatic tracking operation is started.

By the way, in Europe where countries are adjacent to each other, there are many areas where two or more kinds of broadcasting networks overlap, and each network often has broadcasting stations of the same frequency. When the user moves into such an area while moving and the received electric field strength falls below a predetermined threshold level, an automatic follow-up operation based on RDS data is performed. However, at the time of checking the received electric field strength in this automatic tracking operation, if it tries to tune to the AF station which is the RDS station and tunes to another network station, and the received electric field strength is large, the receiving station will be Malfunction caused by moving to another network station.

Such a malfunction is caused by other network stations
It can be recognized because it is not a DS station or because it does not multiplex broadcast the same program identification code PI as the RDS station. Then, when the malfunction is recognized, it is returned to the original RDS station, but for a moment, the broadcast sound of another network station is output from the speaker. In order to reduce such malfunctions, the automatic follow-up operation is not frequently performed in the above area, and therefore, the threshold level for starting the automatic follow-up operation needs to be lowered.

As described above, conventionally, there is a conflicting requirement that the threshold level should be raised and the threshold level should be lowered, and the threshold level is set depending on the balance between the two.

By the way, recently, a radio receiving system (referred to as a first radio receiving system) has been put into practical use, which controls the center frequency and the width of the bandwidth of an intermediate frequency filter by following the instantaneous frequency of an input signal (intermediate frequency signal). ing. FIG. 4 is a configuration diagram of a main part of an FM radio receiver adopting the first radio receiving method, where 11 is an antenna and 12 is 10.7 MHz.
, A ceramic filter that sets the intermediate frequency bandwidth, 200K
When the local frequency is defined at intervals of Hz, the frequency characteristic is set like CFF in FIG. 14 is 10 MHz
, 15 is a mixer, and an intermediate frequency of 10.7 MHz is set to 70 to facilitate the construction of a narrow band filter.
It is converted to 0 KHz. Reference numeral 16 is an intermediate frequency filter whose bandwidth and center frequency f ₀ are variable, and 17 is a demodulation circuit for demodulating a low frequency signal from the intermediate frequency signal. The greater the frequency modulation degree (deviation) from the center frequency 700 KHz, the greater the degree. The output becomes large. Reference numeral 18 denotes a filter control signal generator, which moves the center frequency f ₀ of the intermediate filter 16 based on the demodulated output, in other words, according to the frequency shift 1 of the intermediate frequency signal, as shown in 1a to 1c of FIG. ,
And it controls the width of the bandwidth. In addition, in FIG.
Is the frequency spectrum of the desired station and the adjacent interfering station.

According to the first radio receiving method, the radio receiving can be performed with good sound quality with less distortion, and the audible sensitivity can be improved. The conventional radio receiving method does not control the center frequency of the intermediate frequency filter. It is used together with (called the second radio reception method). And the first and second
In a conventional radio receiver equipped with both of the above radio receiving systems, the threshold level for starting the automatic tracking operation is set to a constant value E ₂ based on the second radio receiving system.

[0009]

When the signal is received by the first radio receiving method, the auditory sensitivity is improved as described above. Therefore, in the first radio receiving method, even if the threshold level for starting the automatic tracking is set to the set value E ₂ or less, the automatic tracking can be started in a good reception state, and the threshold level It is possible to reduce the frequency of the automatic tracking operation in the area where the broadcasting networks overlap by lowering.

However, conventionally, the threshold level for starting the automatic tracking operation is set to a constant value E ₂ based on the second radio receiving system, so that it can be satisfied when receiving by the second radio receiving system. However, there is a room for further improvement when receiving by the first radio receiving method, and there is a problem that cannot be satisfied.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an automatic tracking system for a radio receiver capable of starting an automatic tracking operation at an optimum threshold level according to the radio receiving system.

[0012]

According to the present invention, there is provided a receiving section according to the first radio receiving system for controlling the center frequency of an intermediate frequency filter based on the output of a demodulation circuit,
A receiving section according to a second radio receiving method in which the center frequency of the intermediate frequency filter is not controlled, an automatic follow-up means for performing an automatic follow-up operation when the received electric field strength falls below a predetermined threshold level, and a first radio reception And a threshold level value at the time of radio reception according to the second method, which is smaller than the threshold level value at the time of radio reception according to the second radio reception method.

[0013]

The threshold level value E ₁ at the time of radio reception by the first radio reception system is set to be smaller than the value E ₂ at the time of radio reception by the second radio reception system so that either the first or the second The radio reception method is used to monitor whether or not radio reception is in progress, and the value according to the radio reception method is set as the threshold level E _th, and when the received electric field strength E falls below the threshold level value, automatic tracking operation starts. To do. With this configuration, the automatic tracking operation can be started at the optimum threshold level according to the radio receiving method.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Overall Configuration FIG. 1 is a block diagram of a main part of a radio receiver which realizes an automatic tracking system according to the present invention. Reference numeral 21 is an antenna, and 22 is a front end, which tunes to a predetermined broadcasting station based on a voltage signal output from a PLL circuit described later to generate an intermediate frequency signal. Reference numeral 23 is a first radio receiving section, and 24 is a second radio receiving section. The first radio receiving unit 23,
The center frequency of the intermediate frequency filter is made to follow the instantaneous frequency of the input signal (intermediate frequency signal) based on the output of the demodulation circuit, and has the configuration shown in FIG. The second radio receiving section 24 is composed of an intermediate frequency amplifier, an intermediate frequency filter, a demodulation circuit, etc., and receives with the center frequency of the intermediate frequency filter fixed.

Reference numeral 25 is a selector for selecting / outputting the output from one of the radio receiving sections according to the switching signal SWS.
The switching signal SWS is generated by, for example, a selection operation of a reception system changeover switch of an operation unit (not shown). Reference numeral 26 is a stereo demodulation circuit (MPX), which converts the demodulation signal output from the selector 25 into a stereo signal. 27 is a mute circuit, 28 is an amplifier (AMP), 29 is a speaker,
The sound is output by being driven by the amplifier 28.

Reference numeral 30 denotes a 57 KHz band pass filter (BPF) which allows a 57 KHz subcarrier whose amplitude is modulated based on the RDS data to pass therethrough. 31 is RDS
A decoder, which demodulates RDS data such as AF list and PI code from the output of the bandpass filter. An error correction circuit 32 detects an error in the RDS data such as the AF list and PI code demodulated by the RDS decoder 31 while synchronizing each group and corrects the error.

A signal meter 33 detects the reception level (reception electric field strength) E of the receiving station by monitoring the signal strength of the intermediate frequency signal output from the intermediate frequency amplifier 24a of the second radio receiving section 24. To do. A station detector 34 has a frequency deviation Δf of the received signal.
When the signal strength is within the range of (bandwidth) and the signal strength is equal to or higher than a predetermined level, it is determined that the receiving station exists.
When the station detect signal SD is at a low level, even if the signal intensity detected by the signal meter 32 is high, there is no broadcasting station at the tuning point, and
It is determined that the detected signal strength is affected by the adjacent station.

A reference numeral 35 designates a controller (automatic follow-up processing section) of a microcomputer configuration for carrying out an automatic follow-up processing, which will be described later, based on the RDS data, the received electric field strength E, the station detect signal SD, etc., and a digital tuning processing.
36 is the reception frequency data F input from the controller
It is a PLL circuit that inputs a voltage signal corresponding to DT to the front end 22 and tunes to a predetermined broadcasting station.

Overall Operation The automatic tracking process of the radio receiver shown in FIG. 1 will be described below with reference to the flowcharts shown in FIGS. The radio receiving schemes by the first and second radio receiving units 23 and 24 are referred to as first and second radio receiving schemes, respectively. Controller 35
Monitors whether the radio signal is being received by the first or second radio receiving method based on the switching signal SWS (step 101), and when it is receiving by the first radio receiving method, E ₁ is set. The threshold level E _th is set (step 102), and E ₂ (> E ₁ ) is set as the threshold level E _th when receiving by the second radio reception method (step 103).

In such a state, the signal meter 33
The received electric field intensity E output from the threshold level E _th is compared (step 104). If E ≧ E _th , that is, if the reception state is good, the automatic tracking process is not performed and step 101 is performed. Return to and repeat the subsequent processing. However, when the reception state deteriorates and E <E _th , the automatic tracking operation is started. That is, F of the current receiving station
The RDS data transmitted superimposed on the M broadcast is received via the bandpass filter 30, the RDS decoder 31, and the error correction circuit 32 (step 105).

Thereafter, the ith AF station frequency (the initial value of i is 1) is obtained from the AF list included in the RDS data, and the AF station search processing of 10 msec is performed on the ith AF station. To execute. That is, the mute command MUT is output to mute the sound, and the PLL circuit 36
To the i-th AF station to
2 to tune to the AF station frequency (step 10
6).

Next, the station detect signal SD
Is at a high level (step 107). If it is at a high level, there is a station.
The received electric field strength was taken in from 3 and taken in so far A
The received electric field strength of station F is rearranged in descending order (steps 108 and 109).

After that, or when the signal SD is low level in step 107, A of all AF lists is displayed.
It is checked whether or not the AF search has been completed for station F (step 110). If it has not been completed, i + 1 → i
(Step 111), the mute is canceled, the receiving station is returned to the original receiving station, and the i-th AF station is turned on.
Is completed (step 112).

After that, the processing from step 106 is repeated, and when the AF search processing is completed for all the AF stations, the received electric field strength level La of the current receiving station and the maximum received electric field strength level Lm of the AF station are compared ( Step 113), La ≧ L
If m, it is not necessary to change the receiving station, so step 10
The process returns to 1 and the subsequent processes are repeated.

However, if La <Lm, the controller 35 indicates to the PLL circuit 36 the AF which has indicated the maximum received electric field strength.
The reception of the station is commanded, and the front end 22 is tuned to the broadcasting frequency of the AF station (step 114). Then, the PI code included in the RDS data superimposed and transmitted on the FM signal is extracted, and it is checked whether the PI code matches the PI code indicating the program name broadcast by the original receiving station (step 115), if they match, step 101
Return to and repeat the subsequent processing.

If the PI code cannot be extracted or if the PI codes do not match, the received frequency is returned to the original broadcast frequency of the receiving station (step 116), and then deleted from the AF list (step 117). The AF station having the highest received electric field strength is set as the AF station having the maximum received electric field strength (step 118), and the processing from step 111 onward is repeated.

The present invention has been described above with reference to the embodiments.
The present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these modifications.

[0028]

As described above, according to the present invention, the threshold level value at the time of radio reception by the first radio reception system is made smaller than the value at the time of radio reception by the second radio reception system. , The second radio receiving method is used to monitor the radio reception, and the value according to the current radio receiving method is set as the threshold level, and when the received electric field strength falls below the threshold level value, automatic tracking is performed. Since the operation is started, the automatic follow-up operation can be started at the optimum threshold level in any radio receiving system. That is, regardless of which radio receiving method, the automatic tracking process can be performed in a state where the receiving condition is good to some extent, so that the receiving condition does not deteriorate during the automatic tracking process. In the case of the radio reception system, it is difficult to perform automatic tracking processing in an area where two or more broadcasting networks are overlapped with each other, and thus malfunctions in synchronization with broadcasting stations of other networks can be minimized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a first flowchart of the automatic tracking process of the present invention.

FIG. 3 is a second flowchart of the automatic tracking process of the present invention.

FIG. 4 is a configuration diagram of a radio receiving unit according to a first radio receiving system.

FIG. 5 is an explanatory diagram of a first radio reception system.

[Explanation of symbols]

 23. First radio receiving section 24. Second radio receiving section 25. Selector 33. Signal meter 35 .. Controller

Claims (1)

[Claims] 1. A receiving unit according to a first radio receiving system that controls a center frequency of an intermediate frequency filter based on a demodulation circuit output, and a receiving unit according to a second radio receiving system that does not control a center frequency of an intermediate frequency filter. When the received electric field strength falls below a predetermined threshold level, the frequency of the same program broadcasting station with a large received electric field strength is set based on the frequency data of the same program broadcasting station that is transmitted superimposed on the FM broadcast signal. In the automatic tracking system of the radio receiver having the automatic tracking means for tuning, the value of the threshold level at the time of radio reception by the first radio reception system is the value at the time of radio reception by the second radio reception system. Set a smaller value, monitor whether radio reception is being performed by the first or second radio reception method, and monitor the value according to the current radio reception method. A shawl de level, when the received field strength falls below a threshold level, automatic tracking system of the radio receiver, characterized in that to start the automatic follow-up operation.