JP3593254B2 - Digital broadcast receiver - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital broadcast receiver for receiving a digital broadcast such as DAB (Digital Audio Broadcasting), and more particularly to a digital broadcast receiver for smoothly switching digital broadcast signals. .
[0002]
[Prior art]
DAB has attracted attention as a radio broadcast format that can cope with sound quality deterioration due to interference due to multi-station of FM broadcasts and difficulty in receiving good quality on mobiles. DAB is being developed by Eureka (Euréka: European Advanced Technology Development Plan), and its specifications have already been defined. As a modulation method, π / 4 shift DQPSK-OFDM (Differential Quadrature Phase Shift Keying-Rev. (Orthogonal frequency division multiplexing), and is characterized by being less susceptible to fading and multipath, and using MPEG layer II for high-efficiency voice coding for voice coding, with a transmission bandwidth of 1.5 MHz. It enables a large number of stereo and data broadcasts.
[0003]
In DAB, one ensemble includes a plurality of services and is transmitted by an orthogonal frequency division multiplexing modulation method. Each service further includes one primary audio service component and zero or more secondary audio services. It includes a service component and a data service component. The transmission frame of the DAB digital broadcast signal includes a synchronization channel as a reference signal at the beginning, and the DAB radio tunes and demodulates the frequency based on the synchronization channel to display a predetermined service component through a speaker or display. Output to the container.
[0004]
In the DAB radio, switching of the output is usually switching of an audio service component as a primary service component of each service. At the same time, one predetermined service component is output from the speaker. In a conventional DAB radio, there is of course only one receiver for tuning and demodulating the DAB digital broadcast signal.
[0005]
[Problems to be solved by the invention]
In a conventional DAB radio, if the service component is switched within the same ensemble, there is no need to change the digital broadcast signal to be tuned and demodulated. Since the digital broadcast signal to be switched must be changed, and the digital broadcast signal of DAB includes only a part of the transmission frame at the beginning of the transmission frame and includes the synchronization channel as the reference signal, the digital broadcast signal after the switching is frequency-tuned and synchronized. It takes time to demodulate, and there is a delay before the service component of the switched ensemble is output from the speaker.
[0006]
An object of the present invention is to provide a digital broadcast receiver which can overcome the above-mentioned problems.
[0007]
[Means for Solving the Problems]
A digital broadcast receiver (10) of the present invention receives a digital broadcast signal partially including a reference signal for frequency tuning and demodulation, and performs frequency tuning and demodulation of the digital broadcast signal based on the reference signal. Output the broadcast contents. This digital broadcast receiver (10) has the following (a) to (c).
(A) a first receiving unit (12a) for frequency tuning and demodulating a digital broadcast signal including broadcast content being output based on a frequency deviation and a phase deviation obtained from the reference signal;
(B) a second receiver that frequency-tunes and demodulates a digital broadcast signal other than the digital broadcast signal whose frequency is tuned and demodulated by the first receiving unit (12a) based on the frequency deviation and phase deviation obtained from the reference signal; Receiving unit (12b)
(C) When switching the output to the broadcast content included in the digital broadcast signal other than the digital broadcast signal including the broadcast content being output, the frequency used for frequency tuning and demodulation in the second receiving unit (12b). Control means (13) for sending the deviation and the phase deviation to the first receiving section (12a) and for tuning and demodulating the digital broadcast signal after switching in the first receiving section (12a);
[0008]
The digital broadcast signal includes at least a DAB broadcast signal, and the digital broadcast receiver (10) includes at least a DAB car radio (10).
[0009]
Since a digital broadcast signal only partially includes a reference signal, it takes time to determine the frequency deviation and phase deviation required for frequency tuning and demodulating the digital broadcast signal. However, when the digital broadcast signal relating to the broadcast content to be output is switched, the frequency deviation and the phase deviation already obtained in the second receiving unit (12b) are used, so the first receiving unit (12a) The broadcast content can be output from a speaker or the like in synchronization with the digital broadcast signal after switching quickly.
[0010]
According to the digital broadcast receiver (10) of the present invention, there are a plurality of second receiving sections (12b).
[0011]
Since there are a plurality of second receiving units (12b), the frequency deviation and the phase deviation of each of a plurality of digital broadcast signals other than the digital broadcast signal including the output broadcast content are obtained in advance. Even if there are multiple digital broadcast signals other than the digital broadcast signal including the broadcast content being output, the broadcast content included in the digital broadcast signal selected by the user as the switched digital broadcast signal can be output quickly. it can.
[0012]
According to the digital broadcast receiver (10) of the present invention, there is only one second receiving unit (12b). The control means (13) switches the frequency of the digital broadcast signal tuned by the second receiver (12b) as appropriate, and stores the frequency deviation and the phase deviation of each digital broadcast signal in the second receiver (12b). When the digital broadcast signal is changed in the first receiving unit (12a), the stored frequency deviation and phase deviation are sent to the first receiving unit (12a).
[0013]
Even if there are a plurality of digital broadcast signals other than the digital broadcast signal outputting the broadcast content, the frequency deviation and the phase deviation of these digital broadcast signals can be changed by appropriately switching the tuned digital broadcast signal in the second receiving section (12b). Is obtained and stored in advance. Therefore, even when there are a plurality of digital broadcast signals other than the digital broadcast signal including the broadcast content being outputted, the frequency deviation and the phase deviation of each digital broadcast signal stored in the control means (13) are stored in the first receiving section. By sending the digital broadcast signal to the section (12a), the broadcast content included in the digital broadcast signal selected as the digital broadcast signal after switching by the user can be output quickly.
[0014]
A digital broadcast receiver (10) of the present invention receives a digital broadcast signal partially including a reference signal for frequency tuning and demodulation, and performs frequency tuning and demodulation of the digital broadcast signal based on the reference signal. Output the broadcast contents. This digital broadcast receiver (10) has the following (a) and (b).
(A) a plurality of receivers (12a, 12b) for frequency tuning and demodulating different digital broadcast signals based on their reference signals
(B) selecting means (24) for selecting one of the plurality of receiving sections (12a, 12b) and outputting the broadcast content of the digital broadcast signal whose frequency has been tuned and demodulated by the receiving sections (12a, 12b);
[0015]
The number of receiving units (12a, 12b) is not limited to two, but includes three or more. When switching the digital broadcast signal including the broadcast content to be output, the selection means (24) selects the digital broadcast signal which has already been frequency-tuned and demodulated in the other receiving units (12a, 12b). Therefore, even when the reference signal is only a part of the digital broadcast signal and it takes time to detect the frequency deviation and the phase deviation, the frequency of the switched digital broadcast signal is quickly tuned and demodulated. , The broadcast content can be output.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2, the communication protocol of various elements of DAB such as a transmission frame is appropriately described. For details, see European Telecommunications Standards Institute's European Telecommunications Standards Standard).
[0017]
FIG. 1 shows the structure of a DAB transmission frame. The transmission frame includes a synchronization channel, a FIC (Fast Information Channel), and an MSC (Main Service Channel) in that order from the front. The synchronization channel is composed of two OFDM (Orthogonal Frequency Division Multiplex) symbols. The first OFDM symbol is a null symbol that becomes “0” for a predetermined time. The second OFDM symbol is a phase reference symbol. With the null symbol, it is possible to detect the frequency deviation required for frequency tuning to this digital signal. The phase deviation required for demodulating this digital signal can be detected by the phase reference symbol. The FIC further includes a plurality of FIBs (Fast Information Blocks), and the MSC further includes a plurality of CIFs (Common Interleaved Frames). The specifications of DAB are determined from mode 1 to mode 3, and the transmission frame time (duration) and the number of FIBs and CIFs in one transmission frame are different for each mode. For example, in mode 1, the time of one transmission frame is 96 ms, and the numbers of FIBs and CIFs in one transmission frame are 12 and 4, respectively.
[0018]
FIG. 2 is an exemplary diagram of a DAB service structure. An ensemble whose ensemble label (ensemble name) is DAB ENSEMBLE ONE is a service label whose service label is alpha 1 radio (ALPHA1 RADIO), beta radio (BETA RADIO), alpha 2 radio (ALPHA2 RADIO), or the like. It includes a plurality of services. The user hears the selected service from the DAB car radio 10.
[0019]
The alpha-1 radio has one primary (Service components) and two secondary (secondary) service components. The primary service component is audio, and the secondary service components are a traffic message channel: TMC (Traffic Message Channel) and service information: SI (Service Information). The audio component and the SI are transmitted on separate sub-channels (SubCh) in the MSC, and the TMC is transmitted on a FIDC (Fast Information Data Channel) in the FIC.
[0020]
Beta radio has two service components. Audio and secondary audio components, both of which are carried on MSC sub-channels.
[0021]
The alpha 2 radio has the same TMC and SI as the alpha 1 radio, and the audio may be the same as the alpha 1 radio depending on the switching.
[0022]
FIG. 3 is a block diagram of the DAB car radio 10. The DAB car radio 10 includes an antenna 11, receiving units 12a and 12b, a control unit 13, and an audio decoder 14. Each of the receiving units 12a and 12b includes a frequency conversion unit 19, a digital demodulation unit 20, and a clock generation unit 21. The frequency conversion unit 19 tunes in frequency to a predetermined RF signal from the antenna 11, converts the signal into an intermediate frequency signal, amplifies the signal, and outputs the signal to the digital demodulation unit 20. The digital demodulation unit 20 demodulates and decodes the intermediate frequency signal based on the clock signal from the clock generation unit 21. The audio signal of the predetermined audio service component decoded and extracted in the digital demodulation unit 20 of the reception unit 12a is further output to the audio decoder 14, decoded, and D / A (digital / analog) not shown. The signal is output to a speaker (not shown) via the converter. Thus, the audio service component is output from the speaker. At the time of frequency tuning and demodulation of the ensemble as a digital broadcast signal in the receiving units 12a and 12b, the null symbol and the phase reference symbol of the synchronization channel of the transmission frame relating to the ensemble are referred to, and the reception of the null symbol and the phase reference symbol is performed. With the demodulation of the digital demodulation unit 20 of the units 12a and 12b, the frequency tuning, the frequency deviation and the phase deviation with respect to the RF signal being demodulated are found, and are sent to the control unit 13. The control unit 13 feeds back the frequency deviation to the frequency conversion unit 19, and the frequency conversion unit 19 adjusts the generated frequency based on the feedback signal, and accurately tunes the frequency to the RF signal. The clock generation unit 21 adjusts the phase of the clock pulse based on the feedback signal of the phase deviation from the control unit 13, and the digital demodulation unit 20 becomes zero in phase deviation based on the clock pulse from the clock generation unit 21. Next, demodulation is performed.
[0023]
The receiving unit 12b tunes the frequency of a digital signal related to an ensemble different from that of the receiving unit 12a and demodulates it. Therefore, the control unit 13 can grasp the frequency deviation and the phase deviation of the digital signal being frequency-tuned and demodulated in the receiving unit 12b. When the user switches the audio service component currently being listened to, if the ensemble related to the switched audio service component is another ensemble, that is, a digital signal whose frequency is tuned and demodulated in the receiving unit 12b, the control unit The frequency deviation and the phase deviation output from 13 to the frequency conversion unit 19 and the clock generation unit 21 of the reception unit 12b as control signals are immediately output to the frequency conversion unit 19 and the clock generation unit 21 of the reception unit 12a. The receiving unit 12a is immediately in frequency tuning and demodulation with the audio digital signal of another ensemble, and can immediately output the switched service component from the speaker. After the reception unit 12a completes the switching of the ensemble, the frequency conversion unit 19 and the clock generation unit 21 of the reception unit 12a receive the feedback signal of the frequency deviation and the phase deviation from the digital demodulation unit 20 of the reception unit 12a. Input from the control unit 13.
[0024]
After the ensemble is switched and the receiving unit 12b frequency-tunes and demodulates the ensemble that has been frequency-tuned and demodulated by the receiving unit 12b, the receiving unit 12b outputs the frequency-tuned signal from the control unit 13. The frequency of the third ensemble is tuned and demodulated by switching. If there is no third ensemble, the receiving unit 12b tunes and demodulates the ensemble before the ensemble switching in the receiving unit 12a.
[0025]
Since the DAB car radio 10 of FIG. 3 includes only one receiving unit 12b, in an area where three or more ensembles can be heard, the user can use the ensemble whose frequency is tuned and demodulated by the receiving unit 12b at that time. When trying to switch to an ensemble other than the above, rapid switching cannot be performed because the frequency deviation and the phase deviation of the digital signal of the ensemble are not known. Therefore, a plurality of receiving units 12b are provided, and in each receiving unit 12b, an ensemble other than the frequency tuned and demodulated by the receiving unit 12a and an ensemble different from each other are frequency-tuned and demodulated. At the time of ensemble switching, the frequency deviation and the phase deviation from the receiving unit 12b that tunes and demodulates the ensemble desired by the user are output from the control unit 13 to the frequency conversion unit 19 and the clock generation unit 21 of the receiving unit 12a. I do.
[0026]
Alternatively, the digital signal relating to the ensemble to be tuned and demodulated in the receiving unit 12b is switched at predetermined time intervals, and the frequency deviation and the phase deviation of each digital signal are stored in a predetermined memory in the control unit 13. At the time of ensemble switching, the control unit 13 outputs the stored data of the frequency deviation and the phase deviation of the memory for the ensemble desired by the user from the control unit 13 to the frequency conversion unit 19 and the clock generation unit 21 of the reception unit 12a.
[0027]
FIG. 4 is a modification of the DAB car radio 10 of FIG. 3 are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described. A plurality of receiving units 12a are provided. In the DAB car radio 10, a selection unit 24 is provided, and the connection between the reception units 12a and 12b and the audio decoder 14 is switched by the selection unit 24 according to the switching of the service component by the user. Thereby, the receiving unit 12a or the receiving unit 12b performing frequency tuning and demodulation on the ensemble including the service component switched by the user is selected, the output is sent to the audio decoder 14, and the broadcast content is output from the speaker. You. In the DAB car radio 10 of FIG. 4, the number of receiving units is increased according to the number of ensembles, and the selecting unit 24 selects a desired receiving unit from three or more receiving units 12a and 12b. Is also good.
[Brief description of the drawings]
FIG. 1 is a diagram showing the structure of a DAB transmission frame.
FIG. 3 is a block diagram of a DAB car radio.
FIG. 2 is an exemplary diagram of a DAB service structure;
FIG. 4 is a modified example of the DAB car radio shown in FIG. 3;
[Explanation of symbols]
10 DAB Car Radio (Digital Broadcast Receiver, DAB Radio)
12a receiving unit (receiving unit, first receiving unit)
12b receiving unit (receiving unit, second receiving unit)
13 control unit 24 selection unit (selection means)

Claims (4)

Receiving a digital broadcast signal including a part of the reference signal for frequency tuning and demodulation, on the basis of the digital broadcast signal to the reference signal frequency tuning and demodulation to digital broadcast receivers and outputting the broadcast content (10 )
(A) a first receiving unit (12a) for frequency tuning and demodulating a digital broadcast signal including broadcast content being output based on a frequency deviation and a phase deviation obtained from the reference signal;
(B) A digital broadcast signal different from the digital broadcast signal whose frequency has been tuned and demodulated by the first receiving unit (12a) is converted into a frequency deviation and a phase deviation obtained from a reference signal of the another digital broadcast signal. A second receiving unit (12b) that performs frequency tuning and demodulation based on the frequency, and (c) when the output is switched to the broadcast content included in the another digital broadcast signal, the second receiving unit (12b) performs frequency tuning and It said further in the first receiving unit on the basis of the frequency deviation and phase deviation the frequency deviation and phase deviation are used which sent the first receiver sending to (12a) Rutotomoni for demodulation (12a) Control means (13) for frequency tuning and demodulating the digital broadcast signal of
A digital broadcast receiver characterized by having: 2. The digital broadcast receiver according to claim 1, wherein a plurality of said second receiving units (12b) exist. There is only one second receiving section (12b), and the control means (13) switches the digital broadcasting signal to which the second receiving section (12b) is tuned in frequency as appropriate, and controls the second receiving section (12b). The frequency deviation and the phase deviation of each digital broadcast signal in (12b) are stored. When the digital broadcast signal is changed in the first receiving unit (12a), the stored frequency deviation and phase deviation are stored in the first receiving unit (12a). 2. The digital broadcast receiver according to claim 1, wherein the digital broadcast is sent to one receiver. Each ensemble includes a plurality of audio service components, one ensemble is associated with one digital broadcast signal, and each digital broadcast signal defines a reference signal for frequency tuning and demodulation for each digital broadcast signal. In a digital broadcasting receiver (10), the digital broadcasting signal includes a part, frequency-tunes and demodulates a digital broadcast signal based on its own reference signal, and outputs an audio service component included in the frequency-tuned and demodulated digital broadcast signal . ,
(A) a plurality of receivers (12a, 12b) for frequency tuning and demodulating digital broadcast signals according to different ensembles based on frequency deviation and phase deviation obtained from its own reference signal , and (b) user digital broadcast signal frequency tuning and a receiver that demodulates (12a, 12b) receiving unit and said selected by selecting (12a, 12b) digital broadcast signal is frequency tuning and demodulation including service component is switched Selecting means (24) for outputting an audio service component of
A digital broadcast receiver characterized by having:

Images