JP2006340004A - Radio tuner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio tuner having a seeking means for avoiding adjacency jamming or AF search means of RDS. <P>SOLUTION: Receive frequency is changed with a step at prescribed frequency intervals, and at the same time whether there is a broadcast or not in the receive frequency at each step is judged. If it is determined that there is a broadcast, the adjacency receive frequency at each before-and-after one step adjoining to the receive frequency is received, and detection of receive signal intensity X0, X1 of each signal meter is performed. Only it is determined that both the signal intensity X0, X1 are smaller than a prescribed level, the receive condition of the receive frequency is kept. If it is determined that at least one of signal intensity X0, X1 of the signal meter is a prescribed level or larger, the seeking operation of next receive frequency is continued in a jamming avoiding means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radio tuner, and more particularly to a technique of automatic channel selection in a general FM radio tuner or a radio tuner of an RDS (Radio Data System) receiver.

  In general, an FM radio tuner of a normal analog FM broadcast is a synthesizer tuner (PLL system) as shown in FIG. 3, and includes a tuning circuit 1 that receives a reception signal of an FM antenna, an RF amplifier 2, and a first mixer. 3 and a first local oscillator 4 of the VCO, a reference oscillator (100 kHz) not shown for locking the oscillation frequency of the first local oscillator 4, a 1/10 frequency divider, a phase comparison, a low frequency An intermediate frequency composed of a PLL circuit 5 comprising a filter and a 1 / N counter, a one-stage or two-stage IF filter 6, an IF amplifier 7, a second mixer 8, a second local oscillator 9, and an FM detector 10. And is commercially available as a so-called FM tuner pack 15 bundled in a hybrid integrated circuit block mainly composed of one to several LSIs.

  In general, the N frequency of the 1 / N counter of the PLL circuit 5 is stepped by software control by the microcomputer 20 to change the reception frequency step by step at predetermined frequency intervals (100 kHz). If it is determined that there is a broadcasting station at the received frequency, and if it is determined that there is a broadcasting station, the reception state of the broadcasting station at the receiving frequency is maintained, and the step to the next receiving frequency is stopped and automatic tuning is performed. So-called seek means is provided.

  As a procedure for determining the presence / absence of a broadcasting station at the reception frequency at each step in the seek means, the next N value in the PLL circuit 5 is determined from the reception state at the current reception frequency as shown in the flowchart of FIG. Perform calculation, set N value of PLL circuit 5 and step to the next reception frequency. After a predetermined time has elapsed, detect the electric field strength (DC voltage level of S meter 11) at the reception frequency to a predetermined level. SD (Signal Detector) determination is performed to determine whether or not it is above. If the level is above a predetermined level (YES), a predetermined observation time of the IF frequency in the IF amplifier 7 (a so-called gate time) is further observed. 1/0 judgment (IF count judgment) that the regular IF frequency (10.7 MHz) is detected by detecting the number of peak values in the IF counter 12 once Performed several times Itaru, determines the presence or absence of broadcasting stations in the frequency. If it is determined that there is a station (YES), it is basically to maintain the reception state of the broadcasting station at the reception frequency, stop the step to the next reception frequency, and end the automatic channel selection. It is a procedure.

  Next, the RDS radio tuner used by RDS radio receivers that are put to practical use in Europe and the like has a block configuration as shown in FIG. 5, and has the same circuit configuration as the above-described general FM tuner pack and microcomputer. In addition, an RDS demodulator 17 that receives RDS data output from the RDS FM tuner pack 16 to acquire RDS data and outputs the RDS data to the microcomputer 21 with a 1/0 signal is provided.

  In general, the microcomputer 21 is provided with an alternative candidate station search (AF (Auto Frequency) search) means unique to the RDS in addition to the seek means similar to the above-described, by software control by the microcomputer 21.

  That is, when the reception state deteriorates, the mute state is set, the reception frequency is set to the frequency of the alternative candidate station obtained from the RDS data, the presence / absence of an alternative candidate station exceeding the reference electric field strength is determined, and there is an alternative candidate station If it is determined, the signal strength determination and program identification code determination of the alternative candidate station of the reception frequency is performed, and the reception status of the alternative candidate station is maintained in the case of a regular alternative candidate station having a signal strength equal to or higher than the reference. In general, it has an automatic switching function for stopping the search and switching to an alternative candidate station.

  As a procedure for determining the presence or absence of a receivable alternative candidate station in the AF search means of the alternative candidate station, when the reception state of the currently receiving broadcast station deteriorates due to the software control of the microcomputer 21, for example, When the DC voltage of the S meter 11 in FIG. 5 is monitored and falls below a certain threshold value, or when the multipath component included in the FM detection signal is amplified and converted to DC by the multipath detection circuit 18, the threshold value is exceeded. In such a case, the AF search mode is automatically switched by using these as a trigger. First, as shown in the flowchart of FIG. 6, the check of alternative candidate stations is started from the RDS data of the RDS demodulator 17, and the mute is performed. Set the reception status to the frequency of the checked alternative candidate station, detect the electric field strength, and determine the level Do.

  If it is determined in the above level determination that there is an AF candidate station at a reference value of 29 (24) dBμV or more (YES), the SD determination and IF count determination are performed in the same manner as the FM tuner described above, and further, from the RDS data PI code determination is performed to determine whether or not the acquired RDS program identification code (PI) of the alternative candidate station is the same as the PI code of the currently received broadcasting station. Thereafter, the basic procedure is to maintain the reception state, cancel the mute, and complete the AF search. Of course, if the determination at each stage is NO, the process proceeds to the AF search of the next alternative candidate station.

  By the way, as publicly known documents related to measures against adjacent interference of the radio tuner, for example, the following [Patent Document 1] includes an FM front end unit and a first IF band amplification unit that receives the output of the FM front end unit. A switch unit that receives the output of the FM front end unit and switches the output of the second IF band amplification unit having a narrower band than the first IF band amplification unit and the outputs of the first and second IF band amplification units And an FM demodulator that FM-demodulates the output of the first or second IF band amplification unit that is switched and output by the switch unit, and when it is detected that adjacent interference has occurred in the output of the FM demodulator A stereo full separation according to switching between the adjacent interference detection unit that controls the switch unit to select the output of the second IF band amplification unit and the switch unit. The frequency characteristic correcting means for correcting the frequency characteristic of the composite signal including the FM multiplexed signal and the stereo demodulator for performing stereo demodulation by the output of the frequency characteristic correcting means, and the FM by the output of the frequency characteristic correcting means. An FM stereo tuner configured to perform multiple demodulation is disclosed.

  In [Patent Document 2] below, an IBOC having a carrier frequency adjacent to a reception frequency by an adjacent station detection circuit as a radio receiver capable of setting an appropriate reception state regardless of the presence or absence of the adjacent station. When a station is detected, the control unit sends an instruction to the stereo demodulation circuit, soft mute circuit, etc., and changes the control content of the input / output characteristics such as channel separation characteristics, blend characteristics, high cut characteristics, soft mute characteristics, In addition, a radio receiver is disclosed in which the control unit sends instructions to the multipath detection circuit and the adjacent interference detection circuit to change the threshold for detecting multipath interference and adjacent interference.

  Furthermore, as a publicly known document related to the AF search means of the RDS radio tuner, the following [Patent Document 3] is received as an article that improves the sound cut-out feeling due to the mute operation during the AF search of the RDS receiver. A configuration is shown in which the amount of noise included in an audio signal is detected, and control is performed so as to perform an AF search operation in a form hidden in the noise generation period.

JP-A-6-112914

JP 2005-5819 A Japanese Utility Model Publication No. 5-63122

  In an FM radio tuner having a seek means as described above, when a seek operation is stopped at a certain reception frequency and reception of an FM broadcast station at that reception frequency is started, listening cannot be performed due to the influence of so-called adjacent interference. In addition, there are not many users, and although the switching to the alternative candidate station has been completed by the AF search means in the RDS radio tuner described above, the user is dissatisfied with immediately searching for alternative candidate stations of other frequencies due to adjacent interference (noise). There is a risk of inviting reception.

  Such an automatic tuning operation of the radio tuner, which is an undesirable result for listening, is particularly noticeable in a vehicle-mounted radio receiver whose reception state changes from moment to moment.

  In this regard, in the FM stereo tuner described in [Patent Document 1], as countermeasures for adjacent interference, selectivity setting means for amplifying a received signal by changing selectivity in IF band characteristics, and composite according to selectivity The frequency characteristic correcting means for correcting the frequency characteristic of the signal is used as a constituent element, and the existing tuner pack cannot be used as it is, and a new design is required, and an increase in cost is inevitable. In addition, there is no suggestion about application to adjacent interference during seek operation.

  Further, in the radio receiver described in [Patent Document 2], the threshold for determining the presence / absence of adjacent interference is made variable, and only a predetermined band component is selected from the IF signal when adjacent interference occurs. Although a technique for narrowing the band of a bandpass filter that passes the signal is described, there is no suggestion of a countermeasure when there is an adjacent disturbance during a seek operation.

  Furthermore, the RDS receiver described in the above [Patent Document 3] improves the sound cut-off feeling at the time of AF search, and there is no suggestion regarding appropriate channel selection of alternative candidate stations when there is adjacent interference. .

  The present invention has been made in view of the above circumstances, avoiding undesirable automatic channel selection due to adjacent interference during seek or AF search in a radio tuner mounted on an FM radio receiver or an RDS radio receiver, The purpose is to realize a radio tuner that realizes an appropriate seek operation and an RDS AF search operation.

The present invention
(1) The reception frequency is stepped and changed sequentially at a predetermined frequency interval, and the presence / absence of a broadcast station is determined at the reception frequency at each step. In a radio tuner that includes a seek unit that maintains the reception state and stops the step to the next reception frequency and performs automatic channel selection, when the seek unit is determined to have a broadcasting station, the reception frequency is further reduced. Only when the signal strength of each signal meter is received by receiving the adjacent reception frequency of one step before and after adjacent to the signal meter and the signal strength of each signal meter at the adjacent reception frequency is determined to be less than a predetermined level, The reception state of the broadcast station at the reception frequency is maintained, and the signal strength of at least one signal meter at the adjacent reception frequency is below a predetermined level. When it is determined that the above is satisfied, the above-described problem is solved by providing a radio tuner including an adjacent interference avoidance unit that continues the step to the next reception frequency.
(2) When the reception state deteriorates, the mute state is set, the reception frequency is set to the frequency of the alternative candidate station obtained from the RDS data, the presence / absence of an alternative candidate station having a reference electric field strength or higher is determined, and the alternative candidate station When it is determined that there is a signal, the signal strength determination and program identification code determination of the alternative candidate station of the reception frequency are performed, and the reception status of the alternative candidate station is maintained in the case of a regular alternative candidate station having a signal strength equal to or higher than the reference. In the radio tuner of the radio data system including the AF search means for stopping the search and switching to the alternative candidate station, when the AF search means determines that there is an alternative candidate station, Receiving adjacent reception frequencies of about one step adjacent to the frequency of the alternative candidate station, signal strength detection of each signal meter is performed, and each signal at the adjacent reception frequency is detected. Only when it is determined that the signal strength of the signal meter is less than a predetermined level, the determination that there is an alternative candidate station for the reception frequency is maintained, and the signal strength of at least one signal meter at the adjacent reception frequency is determined to be equal to or higher than the predetermined level. In such a case, the above problem can be solved by providing a radio tuner including an adjacent interference avoidance unit that shifts to the search for the next alternative candidate station when there is no alternative candidate station.

Since the radio tuner according to the present invention is configured as described above,
(1) At the time of a seek operation in the FM radio tuner, there is an excellent effect that a broadcasting station suitable for listening with less influence of adjacent interference is automatically selected.
(2) In the AF search operation of the RDS radio tuner, there is an excellent effect that automatic switching to an alternative candidate station suitable for listening with little influence of adjacent interference is performed.
(3) Even if the existing tuner pack itself does not have an adjacent interference detection function, it is a broadcasting station in a suitable reception state based on the determination of adjacent interference during seek operation or AF search operation only by changing the microcomputer software. Can be selected at low cost.

  An embodiment of a radio tuner according to the present invention will be described with reference to the drawings. The block configurations of the FM radio tuner and the RDS radio tuner according to the present invention are the same as those of the publicly known FM radio tuner of FIG. 3 and the RDS radio tuner of FIG. 5, and detailed descriptions thereof are omitted, and the present invention is exclusively used. Next, the adjacent interference avoidance means in the seek means of the FM radio tuner and the adjacent interference avoidance means in the AF search means of the RDS radio tuner will be described in detail.

  FIG. 1 is a flowchart of a processing procedure of seek means that is software-controlled by a microcomputer of a controller of an FM radio tuner according to the present invention. FIG. 2 is a flowchart of the processing procedure of the AF search means controlled by the microcomputer of the controller of the RDS radio tuner according to the present invention.

  The seek means of the FM radio tuner provided with the seek means according to the present invention having the block configuration as shown in FIG. 3 is similar to the conventional one as shown in the additional processing surrounded by the broken line frame in the flowchart of FIG. When it is determined that there is a broadcasting station at a reception frequency at a certain step by SD determination and IF count determination, an adjacent reception frequency (adjacent station) of one step before and after adjacent to the reception frequency is further received. Only when the signal intensity X0, X1 of the signal meter is detected and it is determined that the signal intensity X0, X1 of the signal meter at the adjacent reception frequency is both lower than a predetermined level, the seek operation is stopped and broadcasting of the reception frequency is performed. The reception state of the station is maintained, and at least one of the signal intensities X0 and X1 of the signal meter at the adjacent reception frequency is determined to be a predetermined level or more. If so, the microcomputer 20 is provided with an adjacent interference avoiding means that is realized by software control on the PLL circuit 5 so as to continue the step to the next reception frequency (next N value) without stopping the seek operation. It has become.

  The determination of the presence / absence of the adjacent interference is made in the reception state of the adjacent frequency by counting the N value of the PLL circuit 5 ± 1 from the current reception frequency in a short mute state of about several milliseconds that hardly affects the listening. It is assumed that the DC voltage level of the S meter is determined as the reference level by the microcomputer 20. The reference level in this case is set as appropriate. For example, as shown in FIG. 1, the magnitudes of X and X0, and X and X1 are compared with reference to the signal intensity X of the S meter of the seek stop station of the reception frequency. Since this can be realized by changing only the software in the microcomputer 20, it is a simple and preferable example.

  Even if it is determined that the broadcast station that can be received by the SD determination and the IF count determination during the seek operation by the adjacent interference avoiding operation according to the above processing procedure, the adjacent interference that is not suitable for listening is determined. If there is a broadcast station, the seek operation is continued without being selected, and a broadcast station suitable for listening is selected in the following steps.

  Next, as in the conventional RDS radio tuner, the AF search means of the RDS radio tuner according to the present invention having the block configuration as shown in FIG. 5 sets the reception frequency to the RDS data in the mute state when the reception state deteriorates. Is set to the frequency of the alternative candidate station obtained from the above, and the presence / absence of an alternative candidate station equal to or higher than the reference electric field strength is determined. In particular, as shown in the additional processing surrounded by the broken line in the flowchart of FIG. When it is determined that there is an alternative candidate station, it further receives adjacent reception frequencies (N values of ± 1 of the N value counter of the PLL circuit 5) around one step adjacent to the frequency of the alternative candidate station. Only when the signal intensity X0, X1 of the signal meter is detected and the signal intensity X0, X1 of each signal meter at each adjacent reception frequency is determined to be less than a predetermined level. If it is determined that there is an alternative candidate station for the reception frequency and the signal intensity X0 or X1 of at least one signal meter at the adjacent reception frequency is determined to be equal to or higher than a predetermined level, it is determined that there is no alternative candidate station and the next alternative candidate station It is the structure provided with the adjacent disturbance avoidance means which transfers to this search.

  The determination of the presence / absence of adjacent interference is performed by counting the N value of the PLL circuit 5 by ± 1 count from the N value of the current reception frequency in a short mute state of about several milliseconds that hardly affects the listening. Switching to the frequency reception state, the signal intensity (DC voltage level) X0, X1 of the S meter is determined as the reference level by the microcomputer 21, respectively. The reference level in this case is set as appropriate. For example, as shown in FIG. 2, the magnitudes of X and X0, and X and X1 are compared with reference to the signal intensity X of the S meter of the seek stop station of the reception frequency. This is a simple and preferable example.

  Even if it is determined that there is an alternative candidate station having sufficient electric field strength during the AF search operation by the adjacent interference avoidance operation according to the above processing procedure, if the adjacent interference is not suitable for listening, the alternative candidate The next alternative candidate station is searched by continuing the AF search operation without being switched to the station, and a switch (tuning) to an alternative candidate station more suitable for listening is realized.

It is a flowchart of the processing procedure of the seek means which the microcomputer of the controller of the FM radio tuner which concerns on this invention performs software control. It is a flowchart of the process sequence of the AF search means which the microcomputer of the controller of the controller of the RDS radio tuner which concerns on this invention carries out software control. It is a block block diagram of the FM radio tuner of normal analog FM broadcasting. It is a flowchart figure which shows the process sequence of the seek means of FM radio tuner. It is a block block diagram of a RDS radio tuner. It is a flowchart figure which shows the process sequence of the AF search means of a RDS radio tuner.

Explanation of symbols

1 Tuning circuit
2 RF amplifier
3 First mixer
4 First local oscillator
5 PLL circuit
6 IF filter
7 IF amplifier
8 Second mixer
9 Second local oscillator 10 FM detection 11 S meter 12 IF counter 15 FM tuner pack 17 RDS demodulator 18 Multipath detection circuit 20, 21 Microcomputer

Claims (2)

The reception frequency is stepped and changed sequentially at predetermined frequency intervals, and the presence / absence of a broadcast station is determined at the reception frequency at each step, and if it is determined that there is a broadcast station, the reception status of the broadcast station at the reception frequency is determined. In a radio tuner comprising a seek means for maintaining and stopping the step to the next reception frequency and performing automatic channel selection,
When it is determined that there is a broadcasting station, the seek means further receives adjacent reception frequencies of one step before and after adjacent to the reception frequency, detects the signal strength of each signal meter, Only when the signal strength of each signal meter is determined to be less than a predetermined level, the reception state of the broadcast station at the reception frequency is maintained, and the signal strength of at least one signal meter at the adjacent reception frequency is equal to or higher than the predetermined level. A radio tuner, comprising: an adjacent disturbance avoiding means for continuing the step to the next reception frequency when judged. When the reception condition deteriorates, the mute state is set, the reception frequency is set to the frequency of the alternative candidate station obtained from the RDS data, the presence / absence of an alternative candidate station with a reference electric field strength or higher is determined, and it is determined that there is an alternative candidate station If it is determined, the signal strength determination and program identification code determination of the alternative candidate station of the reception frequency are performed, and the reception status of the alternative candidate station is maintained in the case of a regular alternative candidate station having a signal strength equal to or higher than the reference. In a radio data system radio tuner having an AF search means for switching to an alternative candidate station by stopping
When it is determined that there is an alternative candidate station, the AF search means further receives an adjacent reception frequency around one step adjacent to the frequency of the alternative candidate station, and performs signal strength detection of each signal meter, Only when it is determined that the signal strength of each signal meter at the adjacent reception frequency is less than a predetermined level, the determination that there is an alternative candidate station for the reception frequency is maintained, and the signal strength of at least one signal meter at the adjacent reception frequency A radio tuner, comprising: an adjacent interference avoidance unit that shifts to a search for a next alternative candidate station when there is no alternative candidate station when it is determined that the frequency is higher than a predetermined level.

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