JP3342275B2 - DAB signal detection device in digital broadcast receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a device for detecting a DAB signal in a digital broadcast receiving device.

[0002]

2. Description of the Related Art DAB signals are provided by Digital Audio Broadcas.
It is a signal of ting, its frequency band is about 1.5 MHz, and its center frequency is likely to be arranged at a multiple of 16 KHz.

Also, the frequency at which the center frequency of a DAB signal is arranged often differs from country to country, and the center frequency is unknown. Further, the frequency range in which the center frequency of the DAB signal can be arranged extends over several MHz.

Therefore, when searching for the center frequency of the DAB signal, conventionally, the center frequency is changed every 16 KHz, that is, synchronization acquisition is performed every 16 KHz, and the current reception and demodulation results at that time are used. It is determined whether or not the center frequency is the center frequency of the DAB signal.

[0005]

However, in the above conventional example, seeking is performed every 16 KHz to search for the center frequency of the DAB signal. There is a problem that time is required.

The present invention detects the frequency at which the DAB signal exists, rather than searching for the center frequency of the DAB signal by seeking every 16 KHz over the entire frequency range where the DAB signal may be located. It is an object of the present invention to provide a DAB signal detecting device in a digital broadcast receiving device which can shorten the time required until the signal is detected.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a predetermined area,
A table is provided in correspondence with the frequency of the broadcast wave used in the area, and based on the area indicated by the received PI code, the frequency of the broadcast wave used in the area is detected from the table, The above-described detected frequency band is excluded from the frequency band in which the center frequency of the DAB signal is searched by seeking for each frequency.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a DAB signal detecting device in a digital broadcast receiving device according to one embodiment of the present invention.

In this embodiment, an RDS receiving unit 10 and an FM
It has a receiving antenna 11, a DAB receiving unit 20, a DAB receiving antenna 21, a memory 30, and a control unit 40.

The RDS receiver 10 demodulates the received RDS signal, outputs a PI code from the demodulated RDS signal,
Is controlled by the control signal for the RDS receiving unit from the PC. The DAB receiving unit 20 has a PLL, a demodulation circuit, etc., outputs a demodulated signal, and the tuning frequency is controlled by a DAB receiving unit control signal from the control unit 40.

The memory 30 stores a predetermined area and an existing broadcast wave used in the area (for example, a television broadcast, an FM broadcast).
This is a memory that stores a table in which the frequency of the broadcast is corresponded.

The control unit 40 controls the whole of the above embodiment, and sends a control signal for the RDS receiving unit to the RDS receiving unit 1.
0, the RDS receiver 10
By receiving a PI code and outputting a DAB receiving unit control signal to the DAB receiving unit 20,
The center frequency of the filter built in AB20 is 16
The frequency information is changed for each KHz, and the frequency information corresponding to the area corresponding to the fetched PI code is fetched from the memory 30. Further, the control unit 40 determines the DAB at that time according to the level of the demodulated signal output from the DAB receiving unit 20.
This is to determine that the DAB signal exists near the center frequency received by the receiving unit 20. That is, the control unit 40
, The frequency information (information of the frequency band of the existing broadcast wave) corresponding to the area fetched from the memory 30 is set to 1.536
The DAB receiving unit 20 removes a center frequency included in the MHz band (a band of one DAB signal) from the search candidates and searches only the remaining center frequencies.
Control.

The RDS is an abbreviation for Radio Data System, and is a system in which digital data for channel selection and the like is multiplexed with an FM radio signal and transmitted.

The PI code is a program identification code, which is composed of a country code, a program code, etc., is formed of 16 bits, and is transmitted at a frequency of 11 times / second. is there.

FIG. 2 shows the memory 30 in the above embodiment.
FIG. 3 is a diagram showing an example of the contents of a table stored by the user.

The table stored in the memory 30 is exemplified by two countries, namely, country A and country B. In country A, the frequency used for FM broadcasting is 88.5 to 88.7 MH.
z, 92.0-92.2 MHz, 98.1-98.3M
Hz, 104.3 to 104.5 MHz, and the operating frequency of the television broadcasting is 61.1 to 68.0 MHz, 18
1.0 to 188.0 MHz,....

Next, the operation of the above embodiment will be described.

FIG. 3 is a flowchart showing the operation of the above embodiment.

First, an RDS broadcast is received, the RDS receiving section 10 detects a PI code (S1), and the detected P
The control unit 40 determines the area (country) where the receiver is currently located based on the I code (S2). Then, the control unit 40
Sends the determined area to the memory 30 as area information,
The memory 30 reads the broadcast frequency band already used in the area from the stored table using the area information as a keyword (S3).

Then, a frequency obtained by adding 768 KHz to the upper limit frequency of the frequency band read from the table and 766 KH from the lower limit frequency of the read frequency band.
A frequency range sandwiched by the frequency obtained by subtracting z is set as a search exclusion band (S4). The search exclusion band is a frequency range that is not included in the search target when a subsequent search is performed. When calculating the search exclusion band, the upper limit frequency of the frequency band read from the table is 768.
Adding KHz or subtracting 768 KHz from the lower limit frequency of the frequency band read from the table is such that the frequency band of one DAB signal is 1.536 MHz and the DAB band overlaps with the existing broadcast wave. Is not set.

Here, the lower limit of the frequency range that can be used for the DAB signal is 47.008 MHz, and the upper limit is 2
It is assumed that the frequency is 40 MHz. That is, 47.008 MHz
To search between 240 MHz and 240 MHz. First, the frequency Fs to be set in the PLL in the DAB receiving unit 20 is set to Fs = 47.008 MHz (S5), and if this frequency Fs is outside the range of the search exclusion band (S5).
6) The frequency is actually set in the PLL, and the electric field strength at that time is detected (S7). If the detected electric field strength is equal to or greater than a predetermined threshold (S8), synchronization acquisition is performed (S8).
9) If a synchronization signal can be detected (S10), it is recognized that a DAB signal has been received at the current reception frequency (S1).
1).

On the other hand, if the frequency Fs to be set in the PLL is within the range of the search exclusion band (S6), the frequency Fs is not set in the PLL, and 16 KHz is added to the frequency Fs to be set in the PLL. The frequency is set as a new frequency Fs to be set in the PLL (S12), and it is determined whether the new frequency Fs is within or outside the range of the search exclusion band (S6). If the frequency Fs is within the range of the search exclusion band, the frequency Fs is not set in the PLL, and a frequency obtained by adding 16 KHz to the frequency Fs that should have been set in the PLL again is a new frequency to be set in the PLL. Fs (S12).

In this way, when the frequency of the DAB signal is searched while sliding the frequency to be set in the PLL every 16 KHz, if the frequency Fs is within the range of the search exclusion band, the frequency Fs is not set in the PLL. The time for detecting the electric field strength within the range of the search exclusion band does not require the processing time for determining whether or not the electric field strength is equal to or more than the threshold value. Therefore, only the processing time within the range of the search exclusion band is required. , And the time for searching the frequency of the DAB signal is reduced.

FIG. 4 is a diagram showing the above embodiment more specifically.

In FIG. 4, the frequency range that can be used in DAB is 47.008 MHz to 240 MHz (19 MHz).
(Frequency range of 2.992 MHz). In this case, in the conventional example, the search target area is as shown in FIG.
As shown in the above, the frequency range of 192.992 MHz is the entire range, and the number of candidates for the center frequency of the DAB in this frequency range is about 12000 (1929292 KHz).
{16KHz @ 12000). When the electric field strength of the DAB is checked for these candidates in order and synchronization acquisition is performed, the maximum number of inspections becomes 12,000.

However, in the above embodiment, when the receiver is located in the country A, the frequency range indicated by the diagonal lines in FIG. 536 MHz × 5 + 1.736 MHz × 4 = 4
The 9.624 MHz frequency range is excluded from the search candidates, and therefore, 49624 KHzＫ16 KHz ≒ 31
For the 00 candidate, there is no need to search. For this reason, when the DAB electric field strength is sequentially checked for these candidates and synchronization acquisition is performed, the maximum number of inspections is 890
0 times (12000 times-3100 times = 8900
Times), and the time required for the search is reduced by 26% as compared with the conventional example.

Therefore, according to the above embodiment, DAB
The time required to detect the frequency at which the DAB signal exists is shorter than when searching for the center frequency of the DAB signal by seeking every 16 KHz over the entire frequency range where the signal may be located. be able to.

In the above embodiment, the DAB receiver 20
The center frequency of the built-in filter is changed every 16 KHz, but it is not exactly 16 KHz but almost 1 KHz.
You may make it change for every frequency of 6 KHz.

The RDS receiver 10 is an example of a PI code detector for detecting a PI code from an RDS broadcast signal wave. The DAB receiver 20 has a filter capable of controlling the center frequency of a pass band. The control unit 40 is an example of a filter center frequency control unit that changes the center frequency of the filter by a predetermined frequency, and according to the level of the signal that has passed through the filter, the DA
It is an example of DAB signal center frequency presence detection means for determining that a B signal is present. Further, the control unit 40
Based on the area indicated by the PI code detected by the code detection means, the frequency of the broadcast wave used in that area is detected from a table stored in the memory 30 and the DAB signal is searched for by a predetermined frequency to thereby detect the frequency of the DAB signal. This is an example of excluding a detected frequency band from a frequency band for searching for a center frequency.

[0030]

According to the present invention, the DAB signal exists more than when the center frequency of the DAB signal is searched by seeking every 16 KHz over the entire frequency range where the DAB signal may be arranged. There is an effect that the time required until the frequency is detected can be shortened.

[Brief description of the drawings]

FIG. 1 is a diagram showing a DAB signal detection device in a digital broadcast receiving device according to one embodiment of the present invention.

FIG. 2 is a diagram showing an example of the contents of a table stored in a memory 30 in the embodiment.

FIG. 3 is a flowchart showing the operation of the embodiment.

FIG. 4 is a diagram more specifically showing the above embodiment.

[Explanation of symbols]

 10 RDS receiver, 20 DAB receiver, 30 memory, 40 controller.

Claims (2)

(57) [Claims] [1 claim: a predetermined area, a table that associates a frequency band of the broadcast wave used in the area provided, R
Based on the area indicated by the PI code output from the RDS receiving unit that receives and demodulates the DS broadcast ,
Detecting the frequency band of the broadcast wave used in the area, searching for the center frequency of the DAB signal by seeking every predetermined frequency, and excluding the detected frequency band from the searched frequency band. A DAB signal detecting device in a digital broadcast receiving device. A filter capable of controlling a center frequency of a pass band; filter center frequency control means for changing a center frequency of the filter by a predetermined frequency; and a filter of the filter according to a level of a signal passing through the filter. Means for detecting the presence of the center frequency of the DAB signal that determines that the DAB signal exists in the band at that time; means for detecting the PI code from the RDS broadcast signal wave; means for detecting the PI code from the RDS broadcast signal wave; Broadcast frequency
Storage means for storing a table corresponding to a band, and based on the area indicated by the PI code detected by the PI code detection means, the broadcast wave used in that area is obtained from the table. detecting a frequency band, the frequency band to search for the center frequency of the DAB signal by seeking every predetermined frequency, DAB signal detection apparatus in the digital broadcast receiving apparatus characterized by excluding the detected frequency band .