JP3875564B2 - FM multiplex broadcast receiving method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an FM multiplex broadcast receiving method, and in particular, stores an alternative frequency list sent from a broadcasting station, and receives a received signal using a predetermined frequency in the alternative frequency list when the reception level is lower than a set level. The present invention relates to a receiving method in an on-vehicle FM multiplex broadcast receiver that continues the above.
[0002]
[Prior art]
In recent years, FM multiplex broadcasting services have been provided in which general information such as weather forecasts and news and road traffic information are multiplexed and transmitted on FM broadcast signals, and these general information and road traffic information are received and displayed by FM multiplex broadcast receivers. It has been broken.
An FM multiplex broadcast receiver in such an FM multiplex broadcast service periodically determines the broadcast status of the same series of frequencies as the currently received FM multiplex broadcast and automatically changes the channel selection to the best frequency. (Auto tuning) function is provided. Here, the series means a series of broadcasting companies such as JFN series and NHK series. The JFN-series FM multiplex station and some independent FM multiplex stations multiplex-transmit DGPS information (GPS correction information), and the NHK-series FM multiplex station multiplex-transmits VICS information.
[0003]
Also, the FM multiplex broadcast receiver appropriately creates a list of receivable FM multiplex stations, displays the list according to the user's request, and allows the user to select a desired FM multiplex station, or traffic information and general A function of selecting information and displaying the selected information is provided.
As described above, the FM multiplex broadcast receiver has an automatic follow-up function and a receivable station list creation function, and the frequency electric field strength is used in both functions. That is, the set value of the electric field strength is held for each function, and the receivable station list creation function determines that there is a possibility of being an FM multiplex broadcasting station if the frequency electric field strength exceeds the set value. Based on the result, the list of receivable stations is created by narrowing down the number of target frequencies. Further, in the automatic tracking function, if the electric field strength of the frequency is below the set value, it is determined that the radio wave condition has deteriorated, and automatic tracking control is started.
[0004]
By the way, in the metropolitan area where the radio wave condition is messy, the minimum electric field strength level at which FM multiplex broadcasting can be received is different from that in the suburban area (region). That is, since each FM multiplex broadcasting station has a large transmission output in the metropolitan area where the radio wave condition is messy, the minimum electric field strength level at which the metropolitan area can receive FM multiplex broadcasting is higher than in the local area. For this reason, if the same low electric field strength level in the metropolitan area as the setting value of each function is used, it is determined that there is a possibility of an FM multiplex broadcasting station at a low level that cannot be received in the metropolitan area. In spite of the low-level electric field intensity that cannot be received, a phenomenon occurs in which the automatic tracking operation does not start.
[0005]
[Problems to be solved by the invention]
That is, in the conventional technique, the same electric field strength setting value is used in any area, so that the operation assumed in the following two points cannot be obtained.
-When creating a list of receivable stations or at the time of automatic tracking, it consists of an operation to narrow down the frequency that seems to be an FM multiplex broadcasting station from all frequencies or a specific frequency group, and an operation to check the presence of multiplexed data by switching to the narrowed frequency. Yes. For this reason, if the electric field strength setting is not appropriate (for example, lower than an appropriate setting value) during the operation of narrowing down the frequency that seems to be an FM multiplex broadcasting station from all frequencies or a specific frequency group, the reception state should be recognized poorly. A frequency that does not exist is recognized as an FM multiplex broadcasting station, and the presence or absence of multiplexed data is checked.
In the confirmation of the presence / absence of multiple data, the processing time per station is long. Therefore, if there are a large number of frequencies to be confirmed, the time required for creating a list of receivable stations and automatic follow-up processing becomes longer overall. During the creation of the list of receivable stations and during automatic tracking, the multiplexed data of the original reception frequency cannot be received. Therefore, when the process is prolonged, the number of missing multiplexed data increases.
[0006]
-The timing for starting the automatic tracking when the radio wave condition deteriorates is one of the conditions that the electric field strength is lower than the set value. If the set value of the electric field strength is not appropriate (for example, an appropriate set value) If the reception state deteriorates and automatic tracking operation is to be performed, the tracking operation is not started because the electric field strength is not lower than the set value. For this reason, it continues to receive a frequency whose reception state has deteriorated, and the multiplexed data during that time is lost.
[0007]
From the above, an object of the present invention is to enable the set value of the electric field strength to be an appropriate value.
Another object of the present invention is to correctly perform the frequency narrowing operation that seems to be an FM multiplex broadcasting station, by reducing the time required for receivable station list creation and automatic follow-up processing and reducing multiplex data that is missing. is there.
Another object of the present invention is to reduce the loss of multiplexed data by reliably performing good reception by an automatic tracking operation when the reception state deteriorates.
[0008]
[Means for Solving the Problems]
The present invention saves an alternative frequency list sent from a broadcast station , and when a reception level becomes a set level E _THL or less, an in-vehicle FM that performs automatic follow-up reception using a predetermined frequency in the alternative frequency list This is a reception method in a multiplex broadcast receiver, where the reception level detection unit detects the reception level of the broadcast signal, and the automatic tracking control unit of the receiver is (1) the first area where the transmission power of the FM broadcast station is large and the FM broadcast Each of the levels E _B and E _S corresponding to the second area where the transmission power of the station is small is held, and the level corresponding to the area where the automobile is present is set as the setting level E _THL . (2) The reception level is the setting seeking level E _THL above all FM multiplex broadcast receivable stations, the average level per station reception level of the FM multiplex broadcast receivable station calculates, with the average value level is above a predetermined level, and, FM multiplex broadcasting the number of receivable stations is equal to or greater than the set number of If, automotive determines that determines that present in the first area, otherwise, the vehicle exists in the second region.
[0009]
In this way, the setting level for narrowing down the frequency and the setting level for starting automatic tracking can be set to appropriate values according to the area where the automobile is located. For this reason, it is possible to correctly perform the frequency narrowing operation that seems to be an FM multiplex broadcast station, and it is possible to reduce the time required for the list of receivable stations and the automatic tracking process and to reduce the missing multiplex data. Further, when the reception state deteriorates, the automatic follow-up operation can be surely started, and thereby good reception can be performed, so that the loss of multiplexed data can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
(A) Configuration of FM multiplex broadcast receiver FIG. 1 is a block diagram of an FM multiplex broadcast receiver according to the present invention. The FM multiplex broadcast receiver receives an FM broadcast signal, separates and demodulates FM multiplex broadcast data such as character information and traffic information transmitted by being multiplexed on the FM broadcast signal, and displays it on a display device. is there.
As shown in FIG. 2, FM multiplex broadcast data is composed of 272 blocks per frame. Of the 272 blocks, 190 blocks are data blocks, 82 blocks are parity blocks that transmit only parity, and the parity blocks are in the data blocks. It is distributed.
[0011]
Each data block includes a 16-bit block identification code (BIC), 176-bit data, a 14-bit CRC code, and a 82-bit parity for error detection and correction (horizontal code). . The parity block is composed of a 16-bit block identification code BIC, a 190-bit parity (vertical code), and a 82-bit parity for error detection and correction (horizontal code).
Among the first 13 blocks, the data block identification code is BIC1, among the next 123 blocks the data block identification code is BIC3, and among the next 13 blocks, the data block identification code is BIC2, and the last Of the 123 blocks, the identification code of the data block is BIC3, and the identification code of the parity block is BIC4.
[0012]
Block synchronization can be achieved by detecting the block identification code for each block, and frame synchronization can be achieved for every 272 blocks (by detecting BIC1 next to the block identification code BIC4). In other words, when the number of times that the block identification code cannot be detected in the above order occurs at a predetermined rate, the block synchronization is lost, and when the frame synchronization cannot be achieved at the predetermined rate, the frame synchronization is lost. Further, since the CRC code is included in the data block, a CRC check can be performed for each block. Further, since parity (vertical code, horizontal code) for error detection and correction is included, error detection and error correction processing can be performed using these parities.
[0013]
In FIG. 1, reference numeral 1 denotes an antenna, and 2 denotes a front end (F / E), which includes an antenna tuning circuit, a high-frequency amplifier circuit, a local oscillator, a mixer and the like (not shown). 3 is a PLL circuit, 4 is a low-pass filter, and 5 is an intermediate frequency amplifier / FM detector (IF / DET). The PLL circuit 3, the low-pass filter 4 and the local oscillator built in the front end 2 constitute an electronic channel selection device, and the local oscillator oscillates at a frequency corresponding to the reception frequency (frequency of the FM broadcast station selected by the channel selection operation). The intermediate frequency signal is output by a mixer in the front end 2.
[0014]
6 is a reception level detector that outputs the received electric field intensity based on the S meter output of the intermediate frequency amplifier / FM detector (IF / DET), and 7 is a noise canceller / stereo demodulator (NC / MPX) that performs noise cancellation and stereo demodulation. ). 8 is a filter circuit that extracts an L-MSK modulation signal component from the FM detection signal, 9 is an L-MSK demodulation circuit that performs delay detection on the L-MSK modulation signal, regenerates the bit clock, and demodulates the bit data string. A synchronization circuit 11 for detecting block synchronization and frame synchronization, and 11 is an error detection and correction unit.
[0015]
A processor (CPU) 12 performs channel selection control according to the channel selection operation, character information display control, setting level change control, automatic follow-up control, receivable list creation control, and the like. RAM for storing received alternative frequency list, metropolitan area mode / local mode, prepared receivable list, etc., 13 for storing received FM multiplexed data (text broadcast program information, traffic information, etc.), Reference numeral 14 denotes an operation unit for performing a channel selection operation or selection of a desired teletext program, 15 a display processor, 16 a display device for displaying character information (traffic information, general information), and 17 a navigation control. Part. The display device 16 can also be used as a map display device of the navigation device.
(B) Determination of metropolitan area mode / local mode Radio waves are messy in urban areas, and FM broadcast stations increase transmission power so that they are not affected by garbage radio waves. For this reason, the reception level in the city is, for example, about 1.75 V, but the reception level in rural areas is low. Therefore, in the present invention, a metropolitan area mode and a regional mode are provided. Then, in consideration of fluctuations in the reception level, the threshold level E _THL that is a reference for automatic tracking and frequency narrowing is set to 1.5 V in the Tokyo metropolitan area mode, and the threshold level E _{THL is set} to 1.0 V in the local mode.
[0017]
FIG. 3 shows a determination process flow of the metropolitan area mode / local mode. In the city, the mode is determined by taking advantage of the fact that the reception level is large and the number of FM multiplex broadcasting stations is larger than in rural areas. However, the mode is determined when the receivable list is created.
The navigation control unit 17 sends a receivable list creation request to the CPU 12 when the apparatus is turned on, in a cycle of 300 seconds, or when a user request is made.
[0018]
The CPU checks whether a list creation request has been made (step 101). If there is a request, the CPU executes a receivable list creation routine shown in FIG. 4 (step 102). That is, the received electric field strength of each frequency in the FM frequency band is measured, and a frequency of the current mode threshold level E _THL (1.5 v or 1.0 v) or higher is set as a candidate (frequency narrowing, step 102a). Next, i = 1 is set (step 102b), and the presence / absence of multiplexed data is confirmed for the i-th candidate frequency (steps 102c and 102d). The presence or absence of multiplexed data is determined by whether or not a predetermined number of blocks having the format configuration shown in FIG.
[0019]
If received, the frequency is registered in the receivable list RVL together with the station name and broadcast contents (traffic information, general information) (step 102e). Thereafter, it is checked whether or not the above processing has been completed for all narrowing candidate frequencies (step 102f). If not completed, i is incremented (i = i + 1, step 102g), and the processing after step 102c is repeated. . Through the above receivable list creation routine, a receivable list RVL as shown in FIG. 1 is created.
[0020]
If the operation of the receivable list routine is completed, the registration frequency n, the average level Eavr reception field strength of each registered frequency calculated (step 103), or is the number n of the registration frequency setting number N _MD or ( N _MD is 3, for example), an average level or Eavr is set level E _MD or (E _MD is 1.5v for example), to check (steps 104 and 105).
In n> N _MD, and, to the metropolitan area mode it is determined that the automobile if Eavr> E _MD is present in the Tokyo metropolitan area. That is, the threshold level E _{THL is set} to E _B (= 1.5 v) (step 106). However, if at least one of steps 104 and 105 is not satisfied, it is determined that the vehicle exists in the region, and the region mode is set. That is, the threshold level E _{THL is set} to E _S (= 1.0 v) (step 107).
[0021]
(C) Automatic tracking FIGS. 5 and 6 are flowcharts of automatic tracking.
The CPU receives and stores in the memory 12a if a frequency list (alternative frequency list) FLS that can be replaced with the currently received frequency is transmitted from the broadcast station (step 201). Next, it is checked whether or not the flag F = "0" (step 202). This flag F = "1" means that the reception level becomes equal to or lower than the threshold level E _THL and the reception state deteriorates and automatic tracking control is being performed.
[0022]
If F = "0", it is checked whether 300 seconds have passed (step 203), and if not, it is monitored whether the received electric field intensity has continued for 5 seconds or more and has become below the threshold level E _THL (step 204). ), If “NO”, the process from step 202 is repeated.
[0023]
If the received electric field strength continues for 5 seconds or more and does not _fall below the threshold level E _THL and 300 seconds elapse, “YES” is determined in step 203, and each frequency in the alternative frequency list is received and the received electric field strength is measured (step 205). Next, it is checked whether there is a frequency whose received electric field strength is larger than the received electric field strength by a set value or more (step 206). If there is no frequency, the original reception frequency is restored and reception is continued (step 207). However, if there is a frequency at which the received electric field strength is larger than the received electric field strength by a set value or more, the frequency of the maximum received electric field strength is received (step 208), and PI (broadcast station identification: NHK series, JFN series, etc.) (Identification) match, whether the received field strength is higher than the set value of the received field strength and whether the number of errors is less than the set value (steps 209 to 211). Continue to complete the frequency shift by automatic tracking (step 212). If any of the conditions in steps 209 to 211 is not satisfied, the original reception frequency is restored and reception is continued (step 207).
[0024]
On the other hand, in step 204, when the received electric field strength continues for 5 seconds or more and becomes the threshold level E _THL or less, the flag F is set to “1” (step 220). Next, each frequency in the alternative frequency list is received, and a frequency whose received electric field strength is _{equal to} or higher than the threshold level E _THL is obtained as a candidate (frequency narrowing, step 221). When the frequency narrowing is completed, the presence / absence of multiplexed data is confirmed for each candidate frequency (step 222). If none of the candidate frequencies is an FM multiplex broadcast frequency, there is no multiplexed data, and the reception is continued after returning to the original reception frequency (step 223). In this case, the processing after step 201 is repeated again. However, since F = "1" in step 202, "NO" is set.
[0025]
On the other hand, if there is an FM multiplex broadcast frequency in step 222, the frequency with the maximum received electric field strength is determined and the frequency is received (step 224). Thereafter, it is judged whether PI (broadcast station identification: identification of NHK series, JFN series, etc.) matches, the received electric field strength is greater than or equal to the threshold level E _THL , and the number of errors is less than the set value (steps 225 to 227). If all are satisfied, the reception at the frequency is continued, the frequency shift by the automatic tracking is completed (step 228), and the flag F is returned to “0” (step 229). If any of the conditions in steps 225 to 227 is not satisfied, the original reception frequency is restored and reception is continued (step 223).
[0026]
If the frequency cannot be changed by the above control, F remains “1” and “NO” in step 202. In such a case, it is checked whether 30 seconds have passed (step 230), and if it has passed, it is checked whether the received electric field strength is equal to or higher than the threshold level E _THL (step 231), and if it is _{equal to} or higher than the threshold level E _THL. The flag is returned to “0” (step 299). However, if the received electric field strength is not greater than or equal to the threshold level E _THL in step 231, the process of step 221 is repeated.
[0027]
(D) Description of Effects of the Present Invention FIG. 7 is an explanatory diagram of effects of the present invention that can reduce the number of candidate frequencies when creating a list of receivable stations to shorten the list creation time. In FIG. 7 (a), 51 is an FM broadcast station having a frequency of 80.0MHz, 52 is an FM broadcast station having a frequency of 84.0MHz, 53 is an FM broadcast station having a frequency of 82.0MHz, and 54 is equipped with the FM multiplex broadcast receiver of the present invention. Car. 61a, 62a and 63a are areas where the received electric field strength at each broadcasting station is 1.5v or more, and 61b, 62b and 6ba are areas where the received electric field strength at each broadcasting station is 1.0v or more.
[0028]
In the prior art, the threshold level is constant regardless of the metropolitan area or region. Here, assuming that the threshold level E _THL is 1.0 v, as shown by PRIOR in FIG. 7 (b), the three FM broadcast frequencies 80.0MHz, 82.0MHz, and 84.0 are obtained by the frequency narrowing performed before the list creation. MHz is determined as a candidate frequency. For this reason, it is necessary to inspect the presence or absence of time-consuming multiplexed data for these three frequencies, and it takes a long time to switch to the original reception frequency.
[0029]
On the other hand, in the present invention, since the threshold level E _THL is 1.5v in the metropolitan area mode, as shown by INVT in FIG. 7 (b), one FM broadcast is performed by frequency narrowing performed prior to list creation. Only the frequency 84.0 MHz is obtained as a candidate frequency. For this reason, it is only necessary to inspect the presence / absence of multiplexed data that takes time only for this frequency, and the time required for switching to the original reception frequency can be shortened.
[0030]
FIG. 8 is an explanatory diagram of the effect of the present invention that can advance the tracking start time during automatic tracking. In FIG. 8 (a), reference numeral 81 denotes an FM broadcast station having a frequency of 80.0 MHz, 82 denotes an FM broadcast station having a frequency of 82.0 MHz, and 83 denotes an automobile equipped with the FM multiplex broadcast receiver of the present invention. Reference numerals 91a and 92a denote areas where the received electric field strength at each broadcasting station is 1.5 v or higher, and 91b and 92b denote areas where the received electric field strength at each broadcasting station is 1.0 v or higher.
[0031]
In the prior art, the threshold level is constant regardless of the metropolitan area or region. Here, assuming that the threshold level E _THL is 1.0 v, in the conventional technique, as indicated by PRIOR in FIG. This is from the point P beyond the area 91b.
In contrast, in the present invention, in the metropolitan area mode, the threshold level E _THL is 1.5 v. Therefore, as indicated by INVT in FIG. From the point Q1 beyond the area 91a where the received electric field strength is 1.5v or more, the automatic follow-up start time can be advanced, and good reception is possible.
[0032]
(E) Summary In summary, the present invention holds the set values of the electric field strengths in the metropolitan area mode and the local mode in the receiver, determines the current reception area, and performs mode switching. Using the set value (threshold level E _THL ) of the field strength of the switched mode for creating the list of receivable stations and automatic tracking, and using the optimal field strength setting value, speeding up and stabilizing the receiver processing・ Encourage FM multiple data guarantee.
[0033]
The procedure is as follows.
(1) When the list of receivable stations is completed, the number of frequencies registered in the list and the average electric field strength of those frequencies are calculated, and the number of registered frequencies exceeds a certain number. The metropolitan area mode is set when a certain level is exceeded. If the two conditions are not met, the local mode is selected.
From (2) onward, the determination at the time of creating a list of receivable stations or automatic tracking uses the set value of the electric field strength of the switched mode.
{Circle around (3)} When the list of receivable stations is completed, a mode switching determination is made every time, and switching can be performed when necessary.
[0034]
【The invention's effect】
As described above, according to the present invention, the threshold level for narrowing down the frequency and the threshold level for starting automatic tracking can be set to appropriate values according to the area where the automobile is located. Can be correctly performed, the multiple data presence / absence confirmation process can be shortened, the time required for the receivable station list creation and the automatic follow-up process can be shortened, and the missing multiple data can be reduced.
[0035]
Further, according to the present invention, when the reception state deteriorates, the automatic follow-up operation can be quickly started, and thereby good reception can be performed, so that the loss of multiplexed data can be reduced. That is, according to the present invention, it is possible to switch the frequency at the optimum timing by using the electric field strength setting value of the optimum mode for the automatic tracking start timing judgment when the radio wave condition deteriorates, and the reception state is determined. It becomes possible to receive the optimum frequency in the deteriorated area. As a result, it is possible to eliminate the situation in which the frequency does not switch despite the deterioration of the reception state, and it is possible to eliminate the loss of multiplexed data.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an FM multiplex broadcast receiver according to the present invention.
FIG. 2 is a frame configuration diagram of FM multiplex broadcast data.
FIG. 3 is a determination process flow of a metropolitan area mode / local mode.
FIG. 4 is a receivable list creation routine.
FIG. 5 is a first processing flow of automatic tracking.
FIG. 6 is a second processing flow of automatic tracking. FIG. 7 is an explanatory diagram of effects of the present invention that can reduce the number of candidate frequencies when creating a list of receivable stations to shorten the list creation time.
FIG. 8 is an explanatory diagram of the effect of the present invention that can advance the follow-up start time during automatic follow-up.
[Explanation of symbols]
2 Front end (F / E)
3 PLL circuit 5 Intermediate frequency amplification / FM detector (IF / DET)
6 Reception Level Detection Unit 9 L-MSK Demodulation Circuit 10 Synchronization Circuit 11 Error Detection Correction Unit 12 Processor (CPU)
13 Memory 16 Display Device 17 Navigation Control Unit
RVL ready list

Claims (1)

An on-vehicle FM multiplex broadcast receiver that saves an alternative frequency list sent from a broadcast station and performs automatic follow-up reception using a predetermined frequency in the alternative frequency list when the reception level falls below the set level E _THL In the receiving method in
The reception level detection unit detects the reception level of the broadcast signal,
The automatic tracking control unit of the receiver
(1) holds the level first transmit power region and FM station transmitting power is large the FM broadcast station corresponding to a small second region E _B, the E _S, respectively, corresponding to the area where motor vehicles are present This level is the set level E _THL ,
(2) the reception level is determined for all FM multiplex broadcast receivable station above the set level E _THL, calculates the average value level per station reception level of the FM multiplex broadcast receivable stations, the average level Is greater than or equal to a predetermined level and the number of FM multiplex broadcast receivable stations is greater than or equal to the set number, it is determined that the vehicle is present in the first region, otherwise the vehicle is present in the second region. judge,
FM multiplex broadcast receiving method characterized by the above.

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