Digital audio broadcasting receiver

• US 6,539,065 B1
• Filed: 09/29/1999
• Issued: 03/25/2003
• Est. Priority Date: 09/30/1998
• Status: Expired due to Term

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Furukawa, Hiroki
• Primary Examiner(s): CORRIELUS, JEAN B
• Application Number:
  US09/407,925
• Time in Patent Office: 1,273 Days
• Field of Search: 375/316, 375/259, 375/260, 375/340, 375/324, 375/295, 370/206
• US Class Current: 375/316
• CPC Class Codes: H04H 2201/20 digital audio broadcasting [DAB]
• CPC Class Codes: H04H 40/18 Arrangements characterised by circuits or components specially adapted for receiving
• CPC Class Codes: H04H 60/11 Arrangements for counter-measures when a portion of broadcast information is unavailable

Abstract

A digital audio broadcasting receiver includes: an analog-digital converter for converting a plurality of transfer frames from an analog signal format into a digital signal format based on a clock signal having a fixed frequency and for outputting the first transfer frame; a demodulator for demodulating the first transfer frame from a first frame processing start position for the first transfer frame; an audio decoder for generating audio data containing a plurality of audio samples based on the data symbol contained in the first transfer frame which has been demodulated by the demodulator; a transfer path characteristics calculator for generating a transfer path characteristics signal representing transfer path characteristics based on the reference symbol contained in the first transfer frame which has been demodulated by the demodulator; and a frame processing start position control section for controlling a second frame processing start position for the second transfer frame, by outputting to the demodulator a position control signal representing a difference between a predetermined frame processing reference start position and the first frame processing start position for the first transfer frame based on the transfer path characteristics signal, so that the second frame processing start position for the second transfer frame coincides with the predetermined frame processing reference start position.

Claims

1. A digital audio broadcasting receiver for receiving a plurality of transfer frames comprising a first transfer frame and a second transfer frame subsequent to the first transfer frame,

each of the plurality of transfer frames containing a null symbol representing a start position of each transfer frame, a reference symbol representing known information, and a data symbol representing data to be transferred, wherein each of the null symbol, the reference symbol, and the data symbol includes a guard interval for preventing intersymbol interference due to a reflected wave,

wherein the digital audio broadcasting receiver comprises:

an analog-digital converter for converting the plurality of transfer frames from an analog signal format into a digital signal format based on a clock signal having a fixed frequency and for outputting the first transfer frame;

a demodulator for demodulating the first transfer frame from a first frame processing start position for the first transfer frame;

an audio decoder for generating audio data containing a plurality of audio samples based on the data symbol contained in the first transfer frame which has been demodulated by the demodulator;

a transfer path characteristics calculator for generating a transfer path characteristics signal representing transfer path characteristics based on the reference symbol contained in the first transfer frame which has been demodulated by the demodulator;

a frame processing start position control section, which includes the transfer path characteristics calculator, for controlling a second frame processing start position for the second transfer frame, by outputting to the demodulator a position control signal representing a difference between a predetermined frame processing reference start position and the first frame processing start position for the first transfer frame based on the transfer path characteristics signal, so that the second frame processing start position for the second transfer frame coincides with the predetermined frame processing reference start position;

an audio sample discrepancy calculation section for calculating a discrepancy between a plurality of audio samples contained in audio data transmitted by a digital audio transmitter and the plurality of audio samples contained in the audio data generated by the audio decoder based on the position control signal; and

an audio sample adjustment section for adjusting the number of audio samples contained in the audio data generated by the audio decoder, based on the audio sample discrepancy, and for selectively outputting audio reproduction data to be reproduced as sound.

2. A digital audio broadcasting receiver according to claim 1,

wherein the demodulator comprises an orthogonal frequency division multiplex demodulator for applying fast Fourier transform to the null symbol, the reference symbol, and the data symbol contained in the plurality of transfer frames, and

wherein the transfer path characteristics calculator comprises a channel impulse response calculator for generating a channel impulse response power characteristics signal, the channel impulse response power characteristics signal being the transfer path characteristics signal.

3. A digital audio broadcasting receiver according to claim 1,

wherein the predetermined frame processing reference start position is a predetermined position within the guard interval of the null symbol.

4. A digital audio broadcasting receiver according to claim 1,

wherein the analog-digital converter converts the plurality of transfer frames from an analog signal format into the digital signal format through sampling with a sampling cycle based on the clock signal having the fixed frequency, and

wherein the audio sample discrepancy calculation section comprises:

a total sample number memory section for storing a total number of samples which have been sampled by the analog-digital converter with the sampling cycle for a predetermined period, the total number of samples corresponding to a difference between the predetermined frame processing reference start position and the first frame processing start position;

a sample number conversion section for converting at least some of the total number of samples stored in the total sample number memory section into a number of audio samples, whereby the audio sample discrepancy is calculated; and

a total sample number correction section for correcting the total number of samples stored in the total sample number memory section by outputting at least some of the total number of samples after having been converted by the sample number conversion section to the total sample number memory section.

5. A digital audio broadcasting receiver according to claim 1, wherein

the audio sample adjustment section comprises at least one sample adjuster corresponding to at least one of monaural reproduction, stereo reproduction, and multi-channel reproduction,

each of the at least one sample adjuster including:

an input buffer for storing a predetermined number of audio samples among the audio samples contained in the audio data generated by the audio decoder;

a cross-fade processing section for reading the predetermined number of audio samples stored in the input buffer, for performing insertion or deletion of the predetermined number of audio samples with cross-fading, and for generating compensated audio data;

a sample adjustment controller for determining a number of audio samples to be inserted or deleted in one process by the cross-fade processing section; and

an output selector for selectively outputting the predetermined number of audio samples stored in the input buffer when performing neither insertion nor deletion of audio samples, and selectively outputting the compensated audio data generated by the cross-fade processing section when performing insertion or deletion of audio samples.

6. A digital audio broadcasting receiver according to claim 5,

wherein the cross-fade processing section comprises:

a first variable gain amplifier and a second variable gain amplifier;

a gain controller for controlling a gain of the first variable gain amplifier and a gain of the second variable gain amplifier;

an adder for adding outputs of the first variable gain amplifier and the second variable gain amplifier; and

an address generator for generating two addresses for audio samples to be input to the first variable gain amplifier and the second variable gain amplifier for insertion or deletion of the number of audio samples determined by the sample adjustment controller, the two addresses being output to the input buffer, and

wherein the gain controller controls the gain of the first variable gain amplifier so as to take a large value first and then gradually decrease and controls the gain of the second variable gain amplifier so as to take a small value first and then gradually increase.

7. A digital audio broadcasting receiver claim 5,

wherein, when the sample adjustment controller performs insertion or deletion of a plurality of audio samples, the insertion or deletion is performed at a plurality of times, with predetermined time intervals therebetween, so that one audio sample is inserted or deleted each time.