JP2006279271A - Automatic channel selection method, and radio receiver with automatic channel selection function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately perform automatic channel selection in a digital broadcasting receiver. <P>SOLUTION: The invention gradually changes a selection channel frequency, and simultaneously carries out sampling for a level of a S meter signal in each frequency at a plurality of points. And a plurality of values carried out sampling are compared, it is discriminated whether a broadcasting station is operating. Further, a condition of variation of an IF counter value is sampled, it is combined with a plurality of samplings of the S meter signal level, and determination of presence or absence of broadcasting office is accurately made. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

 The present invention relates to an automatic channel selection method and a radio receiver having an automatic channel selection function.

  Automatically starts the tuning operation according to the user's instructions, and automatically reaches the station frequency (herein, the station frequency is the frequency of the radio broadcast where the broadcasting station exists). Some radio receivers have an automatic tuning function that stops automatically. For example, if this automatic channel selection function is installed in an in-vehicle radio receiver, the user can concentrate on driving operation.

  As an important technical element of the automatic channel selection method, there is a detection method of a broadcasting station, that is, a detection method of whether it is a stationed frequency. Normally, the channel selection frequency is sequentially changed, and for example, the frequency change is stopped at the frequency at which the intensity of the intermediate frequency signal is maximized. It is determined that broadcasting is being performed at this frequency.

The automatic channel selection method requires accuracy of discrimination. It must be able to correctly identify the frequency at which the broadcast is being performed. For example, in the radio receiver disclosed in Japanese Patent Application Laid-Open No. 10-200355, the broadcast station is based on the SD signal, the IF counter value, and the size of the adjacent interference signal that detect the presence / absence of a broadcast signal from the frequency shift of the received signal. The presence or absence is determined.
Japanese Patent Laid-Open No. 10-200355 (H04B 1/16)

  In recent years, digital radio broadcasting has been started, and in-vehicle digital radio receivers have been developed and commercialized. It is desirable to provide an automatic channel selection function in this digital radio receiver. The automatic channel selection function is an operation of changing from a currently selected frequency to a certain frequency of another broadcast station when a user's instruction or a reception state deteriorates. More specifically, the selected frequency is changed little by little. Then, the frequency at which both the value of the IF counter and the signal level of the intermediate frequency (S meter signal level) are in a better state than the predetermined condition is detected. Then, the frequency changing operation is terminated at the detected frequency. It is determined that there is a broadcasting station at a frequency at which the level of the S meter signal and the IF counter value meet the conditions. This determination is based on a simple premise that the S meter signal level changes, for example, as shown in FIG.

  However, in the case of a receiver for digital broadcasting, there is a case where the determination is made that a broadcasting station is present when the S meter signal level is higher than a predetermined threshold value. Further, even when the IF counter value is a predetermined value, there is a case where the tuning is not correctly performed. This is because the S meter signal level and the IF counter value may change as shown in FIG.

  Therefore, the present invention proposes a radio receiver and an automatic channel selection method that can correctly determine the presence or absence of a broadcasting station.

  The present invention includes a step of changing a channel selection frequency, a step of obtaining a detection signal indicating a reception state corresponding to the channel selection frequency, and a change of a plurality of detection signals corresponding to a plurality of channel selection frequencies in receiving digital broadcasting. Is an automatic channel selection method in which a stationed frequency is discriminated based on the above.

  As a detection signal indicating the reception state, an S meter signal and / or an IF count value can be used. Further, it is desirable to use at least three pieces of data for the detection signal.

  With the configuration described above, according to the present invention, it is possible to provide an automatic channel selection method and a radio receiver that can accurately determine digital radio broadcast reception.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart for explaining the operation in one embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the embodiment, and FIG. 3 is a change in S meter signal and IF counter value accompanying a change in channel selection frequency. FIG. 4 is a characteristic diagram showing a simplified change in the S meter signal accompanying a change in the channel selection frequency.

  First, a hardware configuration will be described with reference to FIG. Reference numeral 1 is an antenna, and 2 is a tuner compatible with digital radio broadcasting. Its function is to select a high-frequency signal having a predetermined frequency, convert it to an intermediate frequency, and output it. The output intermediate frequency signal is subjected to predetermined signal processing by the signal processing circuit 3, and an audio signal is output from the terminal 4. Subsequent amplification circuits and speakers are not shown.

  The microcomputer 5 controls the radio receiver of this embodiment. A predetermined program is stored in the microcomputer, and for example, the operation of the tuner 2 is controlled. The microcomputer 5 controls the frequency selected by the tuner 2 by a command signal to the terminal 2a (serial bus) of the tuner 5. The microcomputer 5 takes in the AD conversion output of the S meter signal from the tuner 2. This is for checking the level of the S meter signal.

  The IF counter value is a count value representing the frequency of the intermediate frequency signal output from the tuner 2. A high frequency signal from the antenna is converted into an intermediate frequency signal in the tuner 2. The IF count value is a predetermined value at the frequency where the broadcast station exists (stationary frequency). The microcomputer 5 can capture the IF count value via the serial bus 6.

  Next, operations related to the present embodiment will be described based on FIG. 1 and other flowcharts. FIG. 1 is a flowchart showing the automatic channel selection operation of the embodiment of the present invention. 13 and 14 are flowcharts showing details of the operation of the portion of FIG. The automatic channel selection mode is started according to a user instruction. Alternatively, a configuration is also conceivable in which the automatic channel selection mode is automatically executed when the reception state of the currently receiving broadcast station deteriorates. When the reception condition deteriorates, in the case of an in-vehicle digital radio, the distance from the broadcasting station increases as the car travels, the reception condition deteriorates, and finally the noise increases and it cannot stand to watch This is the case.

  When the automatic tuning mode is set, variables and other variables are first initialized. Then, Step 11 is performed in which the channel selection frequency is changed by a predetermined magnitude in a predetermined direction with respect to the current channel selection frequency. Details of step 11 are shown in FIG.

  First, it is checked whether or not the currently selected frequency ft is within the range of the minimum frequency f_min and the maximum frequency f_max. If the frequency is out of the range and is lower than the minimum frequency f_min, the channel selection frequency ft is set to the maximum frequency f_max, and if it is higher than the maximum frequency f_max, the channel selection frequency ft is set to the maximum frequency f_min (step) 11A).

  Next, it is determined whether this is the first processing after the start of the automatic channel selection mode or the processing at the boundary (when the maximum frequency or the minimum frequency is set in the previous step 11A) (step 11B). This determination is performed using a flag. Immediately after the start of the automatic tuning mode, in addition to the tuning frequency ft, the S meter signal level at each time point is AD converted for the previous frequency ft−Δf and the next frequency ft−Δf. Then, it is taken in and stored in the microcomputer. Further, an IF count value at each time point is obtained and stored via the serial bus 6 (step 11C). Then, the process proceeds to Step 12 (FIG. 1). The S meter signal level at the current time ft is stored in s [ft], and the IF counter value is stored in IF [ft]. The previous S meter signal is stored in S [ft−Δf] and IF counter value IF [ft−Δf]. The next S meter signal is stored in s [ft + Δf], and the IF counter value is stored in IF [ft + Δf].

  In cases other than the first time and a boundary time (at the time of a band edge), the S meter signal level and IF counter value at the next frequency determined by whether the frequency change direction is up or down are measured and stored (step 11D). . From Steps 11C and 11D, the process proceeds to Step 12 in FIG. 1 to check whether analog broadcasting or digital broadcasting can be received at the current channel selection frequency ft. If either analog or digital broadcasting can be received, it is determined that the station is stationed. In step 14, the current channel selection frequency is returned to the previous state, and the automatic channel selection mode is terminated.

  If neither analog nor digital broadcasting can be received, the process proceeds to step 13 to change the channel selection frequency, and to shift the stored measurement data for use in the next determination, Return to Step 11. The loop of steps 11, 12, 13 will be repeated until a stationed frequency is found. Although not shown in the flowchart in FIG. 1, the automatic channel selection mode may be terminated if the frequency of the station cannot be detected even if the entire frequency region is scanned.

  FIG. 14 shows details of step 13. First, in step 13A, it is determined whether the frequency change direction is up or down. If the frequency is to be lowered (down), the measurement data shown in step 13B is shifted and the channel selection frequency ft is set to Δf. Just make it smaller. In the case of increasing the frequency (up), the measurement data shown in step 13C is shifted to increase the channel selection frequency ft by Δf.

  The determination of whether or not the station is stationed in step 12 is performed based on the three sampling data. It is necessary to determine the condition for determining whether or not the station is stationed according to the specifications of the receiver. An example of the determination criterion is as shown in FIGS. Here, Sa is the lower limit value of the S meter for analog signals, IF1_La is the lower limit value of the IF counter at ft−Δf for analog signals, IF2_La is the lower limit value of the IF counter at ft for analog signals, IF3_La is the lower limit value of the IF counter at ft + Δf for an analog signal, IF1_Ha is the upper limit value of the IF counter at ft−Δf for an analog signal, and IF2_Ha is the IF counter value at ft for an analog signal. The upper limit value IF3_Ha is the upper limit value of the IF counter at ft + Δf in the case of an analog signal.

  Further, Sd is a lower limit value of the S meter in the case of a digital signal, IF1_Ld is a lower limit value of the IF counter in ft−Δf in the case of a digital signal, IF2_Ld is a lower limit value of the IF counter in ft in the case of a digital signal, and IF3_Ld. Is the lower limit value of the IF counter at ft + Δf for a digital signal, IF1_Hd is the upper limit value of the IF counter at ft−Δf for a digital signal, and IF2_Hd is the upper limit value of the IF counter at ft for a digital signal. The value IF3_Hd is the upper limit value of the IF counter at ft + Δf in the case of a digital signal.

  15 and FIG. 16 show the conditions for determining the presence of a station, as shown in the graphs, respectively, as shown in FIGS. That is, the level of the S meter signal is greater than a predetermined level at a plurality of frequency points, and the IF counter value is located within a predetermined range at the plurality of frequency points.

  In step 12, even when the reception status of the analog signal and the digital signal is poor, the channel selection operation may be stopped under the following conditions in order to stop the reception. These conditions can be understood from the graphs of FIGS. In any case, it is common to measure data at multiple frequencies and use the results to make a decision, but the conditions have been relaxed so that even if the reception situation is bad, it can be identified as stationed. Yes.

  7 to 9 show the determination conditions in analog broadcasting, and FIG. 17 collectively shows the conditions. In FIG. 7, the S meter signal level is larger than the threshold value Sa only at the center frequency ft, and is smaller than the threshold value Sa on both sides. In this case, the IF count value is used for determination only when the S meter signal level is larger than the threshold value Sa.

  In the case of FIGS. 8 and 9, two sets of measurement data out of the three sets of measurement data match the condition. Even when the conditions shown in FIGS. 8 and 9 are met, it can be determined that the station is stationed.

  10 to 12 show the determination conditions in digital broadcasting, and FIG. 18 collectively shows the conditions. Also in this case, the IF counter value is compared only when the S meter signal level is larger than the predetermined threshold value Sd, as in the case of the analog signal. In the case of digital broadcasting, unlike the case of analog broadcasting, the S meter signal level needs to be larger than the threshold value Sd at two frequencies among the three measurement frequencies.

It is a flowchart explaining operation | movement of the Example of this invention. It is a block diagram which shows the structure of the Example of this invention. It is a characteristic view which shows the change of S meter signal and IF counter value at the time of digital broadcast reception. It is a characteristic view which shows the change of S meter signal at the time of analog broadcast reception, and IF counter value. It is a characteristic view which shows the stop conditions at the time of analog broadcast reception. It is a characteristic view which shows the stop conditions at the time of digital broadcast reception. It is a characteristic view which shows another stop conditions at the time of analog broadcast reception. It is a characteristic view which shows another stop conditions at the time of analog broadcast reception. It is a characteristic view which shows another stop conditions at the time of analog broadcast reception. It is a characteristic view which shows another stop conditions at the time of digital broadcast reception. It is a characteristic view which shows another stop conditions at the time of digital broadcast reception. It is a characteristic view which shows another stop conditions at the time of digital broadcast reception. It is a flowchart which shows the detail of operation | movement. It is a flowchart which shows the detail of another operation | movement. It is explanatory drawing which put together the stop conditions in the case of analog reception. It is explanatory drawing which put together the stop conditions in the case of digital reception. It is explanatory drawing which summarized another stop condition in the case of analog reception. It is explanatory drawing which summarized another stop condition in the case of digital reception.

Explanation of symbols

1 Antenna 2 Tuner 3 Signal Processing Circuit
4 Microcomputer

Claims (10)

A step of changing a channel selection frequency, a step of obtaining a detection signal indicating a reception state corresponding to the channel selection frequency, and a determination of a stationed frequency based on changes in a plurality of detection signals corresponding to a plurality of channel selection frequencies. Automatic tuning method.
The automatic channel selection method according to claim 1, wherein the plurality is three. 3. The automatic channel selection method according to claim 2, wherein there are a plurality of types of detection signals. 4. The automatic channel selection method according to claim 3, wherein the detection signal is an S meter signal and an IF counter value. 5. The automatic channel selection method according to claim 4, wherein the determination of the stationed frequency is performed by determining that the IF count value is within a predetermined range and the level of the S meter signal exhibits a predetermined change. Means for changing the tuning frequency of the tuner;
A detection signal creating means for obtaining a detection signal indicating a reception state corresponding to the tuning frequency;
A radio receiver having an automatic channel selection device provided with a discriminating means for discriminating a stationed frequency based on changes in a plurality of detection signals corresponding to a plurality of channel selection frequencies. The radio receiver according to claim 6, wherein the plurality is three. 8. The radio receiver according to claim 7, wherein there are a plurality of types of detection signals. The radio receiver according to claim 8, wherein the detection signal is an S meter signal and an IF count value. 10. The radio receiver according to claim 9, wherein the determination of the stationed frequency is performed by determining that the IF count value is within a predetermined range and the level of the S meter signal exhibits a predetermined change.