Multiplex communications – Generalized orthogonal or special mathematical techniques – Particular set of orthogonal functions
Reexamination Certificate
1999-03-29
2002-08-06
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Generalized orthogonal or special mathematical techniques
Particular set of orthogonal functions
C370S210000, C708S404000, C375S261000
Reexamination Certificate
active
06430149
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a processing circuit for a complex operation, and more particularly, is directed to an improvement in a processing circuit for a complex operation which is operative to receive a pair of orthogonal demodulation output signals obtained by causing an orthogonal frequency division multiplexing signal to be subjected to quadrature demodulation, to cause each of the orthogonal demodulation output signals to be subjected to complex operation processing for fast Fourier transform and to cause the result of the complex operation processing for fast Fourier transform to be subjected to complex operation processing for differential demodulation so as to obtain reproduced data outputs based on the orthogonal frequency division multiplexing signal.
2. Description of the Prior Art
Although an analog audio broadcasting system which includes an amplitude-modulated (AM) audio broadcasting system in which audio signals are transmitted in the form of an AM audio information signal and a frequency-modulated (FM) audio broadcasting system in which audio signals are transmitted in the form of an FM audio information signal, has been put to practical use for a long time in the field of audio broadcasting, there has been recently proposed to introduce a digital audio broadcasting system in which audio signals are transmitted in the form of a digital audio information signal for the purpose of improving quality of audio information transmitted or received in the system. Especially, in the region of Europe, the digital audio broadcasting system called a “DAB” system has been already put to practical use in some countries.
The digital audio information signal transmitted from a broadcasting station under the digital audio broadcasting system is called a digital audio broadcasting signal. The digital audio broadcasting signal carries not only audio information data forming a digital audio signal but also service information data representing service information, such as weather forecast, traffic information and so on, and further carries control information data which are necessitated for reproducing the digital audio signal based on the audio information data and the service information based on the service information data on the receiving side. Then, the digital audio broadcasting signal is a modulated wave signal obtained by modulating a carrier wave signal with digital data, such as audio information data, service information data, control information data and so on, in accordance with the Orthogonal Frequency Division Multiplexing (OFDM) system and the digital data transmitted by the digital audio broadcasting signal is composed of a series of frame units, each of which is called a transmission frame.
The transmission frame has a time duration of, for example, 96 ms and contains 77 segmental periods each named Symbol and identified with Symbol
0
to Symbol
76
, respectively, as shown in
FIGS. 1A and 1B
. The Symbol
0
is a null Symbol where the modulated wave signal does not exist in actual fact. The Symbol
1
is a reference Symbol for synchronization. The Symbol
0
which is the null Symbol corresponds to about 1.3 ms and each of the Symbol
0
to the Symbol
76
corresponds to about 1.25 ms.
A channel named Synchronous Channel is allocated to the Symbol
0
and the Symbol
1
, a channel named Fast Information Channel (FIC) is allocated to the Symbol
2
to the Symbol
4
following the Symbol
1
, and a channel named Main Service Channel (MSC) is allocated to the Symbol
5
to the Symbol
76
following the Symbol
4
, as shown in
FIGS. 1A and 1B
. The MSC is composed of a series of frames each named Common Interleaved Frame (CIF) for transmitting the audio information data and the service information data. The FIC is composed of series of blocks each named First Information Block (FIB). The FIB contains a couple of portions of a FIB data field and an error checking word, and the FIB data field is composed of a series of groups each named Fast Information Groups (FIGS). The FIC thus formed transmits the control information data representing multiplex configuration information (MCI) and other information.
Each of the Symbol
1
to the Symbol
76
contains a couple of portions Gi and Se, as shown in FIG.
1
C. The portion Gi is named Guard Interval and corresponds to about 0.246 ms. The portion Se is named Effective Symbol and corresponds to about 1 ms.
The above described digital audio broadcasting signal which is a modulated carrier wave signal obtained by modulating a carrier wave signal with digital data, such as audio information data, service information data, control information data and so on, in accordance with the OFDM system and transmitting the digital data in the form of a series of the transmission frames, is received by use of a digital audio broadcasting signal receiver.
In the digital audio broadcasting signal receiver, each of digital audio broadcasting signals transmitted respectively from a plurality of broadcasting stations is received selectively through a tuning operation by a tuner and the received digital audio broadcasting signal is subjected to demodulation processing, data selection and so on so as to produce audio information data, service information data and control information data. The audio information data and service information data are further subjected to decoding processing for producing digital audio signals and service data.
FIG. 2
shows an example of the digital audio broadcasting signal receiver which has been generally proposed. In the digital audio broadcasting signal receiver shown in
FIG. 2
, a digital audio broadcasting signal, which is a modulated carrier wave signal obtained in accordance with the OFDM system, transmitted from a broadcasting station and having reached to a receiving antenna
21
, is received through a tuning operation by a tuner
22
. The tuning operation by the tuner
22
is performed in accordance with a tuning control signal STD supplied to the tuner from a control unit
40
. In the tuner
22
, the digital audio broadcasting signal received selectively is subjected to amplifying processing and frequency-converting processing to produce an intermediate frequency (IF) signal SID. The IF signal SID is supplied to an analog to digital (A/D) convertor
23
.
A digital IF signal DID corresponding to the IF signal SID is obtained from the A/D convertor
23
to be supplied to a quadrature demodulator
24
. In the quadrature demodulator
24
, the digital IF signal DID is subjected to quadrature demodulation processing to produce I and Q signals DI and DQ which are a pair of quadrature demodulation output signals.
The I and Q signals DI and DQ obtained from the quadrature demodulator
24
are supplied to a fast Fourier transform (FFT) differential demodulator
25
. In the FFT differential demodulator
25
, each of the I and Q signals DI and DQ is subjected to transformation from a time domain signal to a frequency domain signal to produce control information data DCD representing control information transmitted through the FIC and composite data DXD composed of audio information data and service information data representing respectively audio information and service information transmitted through the MSC.
The audio information data and service information data constituting the composite data DXD have been subjected to time interleaving arrangements respectively to form time interleaved audio information data and time interleaved service information data. Each of the audio information data and service information data are composed of a series of logical frames each having a time duration of, for example, 24 ms and corresponding to the CIF. The time interleaving arrangement to which each of the audio information data and service information data have been subjected has been carried out to each interleaving completion segment consisting of, for example, successive sixteen logical frames. Each of the logical frames is composed of a series
Ho Duc
Hsu Alpus H.
Maioli Jay H.
Sony Corporation
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