WO1997000566A2 - Surechantillonnage et interpolation pour modulateur multiporteur - Google Patents
Surechantillonnage et interpolation pour modulateur multiporteur Download PDFInfo
- Publication number
- WO1997000566A2 WO1997000566A2 PCT/FR1996/000911 FR9600911W WO9700566A2 WO 1997000566 A2 WO1997000566 A2 WO 1997000566A2 FR 9600911 W FR9600911 W FR 9600911W WO 9700566 A2 WO9700566 A2 WO 9700566A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- samples
- frequency
- dab
- analog
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
- H04L27/2627—Modulators
- H04L27/2644—Modulators with oversampling
Definitions
- the present invention relates to a method and a device for oversampling and frequency transposition of a digital radio signal of the type known by the Anglo-Saxon abbreviation DAB for "Digital Audio Broadcast” and as defined by the directives of the European project Eureka. relating to the installation of digital transmissions to replace the current emissions in frequency modulation for the diffusion of radio programs.
- the DAB signal is supplied by the COFDM modulator by a standardized interface circuit WG 1-2, in the form of two digital channels I and Q carrying digital samples of signal coded on 8 bits and paced at a frequency of 2.048 MHz.
- a translation of the DAB signal into an analog form is then carried out and the analog signal obtained is transposed in frequency to a determined carrier frequency, generally 1.5 GHz, before being amplified.
- the solution which appears most direct to obtain this result consists in carrying out a digital analog transformation on each of the two channels I and Q and in carrying out a transposition on a carrier of each analog signal in baseband thus created.
- the object of the invention is to overcome the aforementioned drawbacks.
- the subject of the invention is a method for oversampling and transposing in frequency a digital radio signal DAB modulated according to a COFDM modulation and sampled at a determined frequency Fe, for its transformation into an analog signal, characterized in what it consists of inserting between the successive samples of the DAB signal samples whose amplitude is interpolated between the values of samples neighboring the DAB signal and digitally transposing the signal samples obtained on an intermediate frequency under multiple of the frequency interpolated samples before converting them to analog form.
- the invention also has the advantage of offering a mixed digital analog solution using only a limited number of components to effect the transformation into analog of the DAB signal and its transposition on the carrier frequency of the transmitter.
- FIG. 1 a flowchart to illustrate a possibility of transformation according to the invention of a DAB signal into an analog signal by the implementation of an entirely digital processing method.
- FIG. 2 an embodiment of a device for implementing the method illustrated by the diagram in FIG. 1.
- Figure 3 a frequency response curve of a half-band filter used in the device of Figure 2.
- FIG. 5 the temporal evolution of the signal processed inside the device represented in FIGS. 4a and 4b.
- FIG. 6 the evolution of the spectrum of the signal observed at the various stages of the processing carried out by the device of FIGS. 4a and 4b.
- Figures 7 to 12 the evolution of the spectrum of the DAB signal throughout the processing chain making up the device shown in Figures 4a and 4b.
- steps 1 and 2 of the flowchart shown in Figure 1 offers a fully digital processing solution and avoids the problems encountered during the implementation of analog solutions.
- the oversampling operation can be carried out by performing an interpolation filtering making it possible to reconstruct missing samples between successive samples of the DAB signal or else be carried out as shown in FIG. 1 by inserting in step 1 null samples in the digital stream composing the DAB signal in order to obtain the desired sampling frequency and by filtering in step 2 the train of digital signals obtained to suppress the image frequencies.
- the embodiment of FIG. 2 makes it possible to pass from a DAB signal sampled at 2.048 MHz to a DAB signal oversampled at the frequency 16.384 MHz, by digital interpolation by a factor 8 of the DAB signal d 'origin.
- This is obtained by interposing on the I and Q channels a set of 5 devices optionally each composed of one or more signal processing processors operating in parallel or by a configurable ASIC of the same type referenced from 3 to 7, allowing the insertion of null samples into a digital stream of samples and the digital filtering necessary to suppress the resulting image frequencies.
- HSP 43216 component marketed by the law company of the United States of America HARRIS as a configurable ASIC.
- This component has a half-band filter whose normalized frequency response has the characteristics shown in FIG. 3.
- the association in series on each I and Q channel of two components referenced respectively 3, 4 and 5, 6 makes it possible to pass successively from a sampling frequency of 2.048 MHz to a frequency of 4.096 MHz at the output of components 3 and 5 then at a frequency 8.192 MHz at the output of components 4 and 6.
- the device which is shown in FIG. 4a comprises an interface circuit 9 coupled to a COFDM modulator.
- the interface circuit 9 applies on two channels I and Q samples clocked at 2.048 MHz on the corresponding inputs of a null sample insertion module 10.
- This sample insertion module can be formed in a known manner using a stack of correctly timed digital registers to provide a flow of complex samples at 8.192 MHz on two channels I and Q.
- This stream of samples is applied to the corresponding inputs of an interpolation module 11 composed, for example, by a component of the HP43216 type mentioned above and suitably programmed to perform successively, as shown in the block diagram of FIG. 4b, a factor 2 oversampling represented by blocks 14a, 14b, half-band digital filtering using finite impulse response filters represented by blocks 15a, 15b and transposition represented by block 16 on an equal intermediate frequency at 1/4 of the sampling frequency, i.e. 4.096 MHz for a sampling frequency of 16.384 MHz of the signal applied to it.
- This transposition results from a nesting in the block . 16 sample suites, respectively ⁇ i 0 , i, ...
- the transposed signal obtained is applied to a digital analog converter 12 sampled at the frequency 16.384 MHz, the output of which is filtered by an analog filter 13 of the Chebyschev type of order 8, for example, to -select the useful band of the signal in the different images generated by digital oversampling.
- the analog signal thus obtained can then be applied to the input of a transmission chain of a broadcasting transmitter not shown, to be amplified and transposed to the carrier frequency of the transmitter.
- the temporal evolution of the signal is shown in FIG. 5 as a function of the processing steps, observed at the places referenced from A to E on the device represented in FIGS. 4a and 4b and the corresponding spectral evolution is represented in FIGS. 6 to 12.
- the signals at A in FIG. 4a are those obtained at the output of the interface module 9. They are formed as shown in FIG. 5 by a series of samples of variable amplitudes and clocked at the frequency of 2.048 MHz.
- the corresponding spectrum of the sampled DAB signal represented in FIG. 7 has a baseband width of between - 1 MHz and + 1 MHz.
- the insertion of null samples takes place in the manner shown at B in FIG. 5 by inserting, between two successive samples of the signals at A, three samples of zero amplitudes also spaced apart by a distance equal to a quarter of the period separating two samples of the signal at A.
- This operation amounts to multiplying by 4 the frequency of the samples and artificially widening as shown in FIG. 6 by four times the width of the spectrum of the initial DAB signal.
- the oversampling frequency is further doubled, which brings to eight the number of null samples inserted between two samples of the initial DAB signal.
- This last operation is equivalent to multiplying by eight the width of the spectrum of the initial DAB signal as shown in Figure 8.
- the signal appearing in D in FIG. 4b at the output of the half-band filters with infinite response corresponds to an interpolation between two non-zero samples of the signal obtained in C. Its spectral distribution which is shown in FIGS. 6 and 9 is between the frequencies - 4.096 MHz and + 4.096 MHz.
- the signal obtained in D is then transposed in frequency by a module 16 on the frequency 4.096 MHz.
- the resulting spectrum is shown at D ′ in FIG. 6.
- the transposition operation generating image frequencies, the spectrum of the signal obtained at E at the output of the module 11 finally occupies a bandwidth between - 8.192 MHz and 8.192 MHz as this is shown in Figures 6 and 10.
- the spectrum of the signal obtained in F on the output of the digital analog converter 12 is represented in FIGS. 6 and 12.
- the spectrum of the signal selected in G by the filtering module 13 finally has the form represented in FIG. 11.
- the Chebyschev filter which makes up the filtering module 13 and which, in the example described, has a bandwidth of 2.048 MHz centered on the frequency 4.096 MHz under a multiple of the frequency of the samples interpolated by the module 11, allows indeed a useful spectrum selection outside the spectra overlap zones or (aliazing zones in the English language) of the signal E represented in FIG. 6.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Analogue/Digital Conversion (AREA)
- Television Systems (AREA)
- Transmitters (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP96922924A EP0836772A2 (fr) | 1995-06-16 | 1996-06-14 | Surechantillonnage et interpolation pour modulateur multiporteur |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9507227A FR2735636B1 (fr) | 1995-06-16 | 1995-06-16 | Procede et dispositif de surechantillonnage et de transposition en frequence d'un signal radio numerique |
FR95/07227 | 1995-06-16 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1997000566A2 true WO1997000566A2 (fr) | 1997-01-03 |
WO1997000566A3 WO1997000566A3 (fr) | 1997-01-23 |
Family
ID=9480087
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FR1996/000911 WO1997000566A2 (fr) | 1995-06-16 | 1996-06-14 | Surechantillonnage et interpolation pour modulateur multiporteur |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0836772A2 (fr) |
FR (1) | FR2735636B1 (fr) |
WO (1) | WO1997000566A2 (fr) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1237342A3 (fr) * | 2001-03-01 | 2006-05-03 | Alps Electric Co., Ltd. | Modulateur multiporteuse |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0323675A1 (fr) * | 1988-01-06 | 1989-07-12 | Philips Electronics Uk Limited | Montage de génération d'un signal à bande latérale unique |
WO1994017599A1 (fr) * | 1993-01-28 | 1994-08-04 | Telefonaktiebolaget Lm Ericsson | Boucle de reaction a porteuses multiples cartesienne |
JPH06326739A (ja) * | 1993-05-11 | 1994-11-25 | Sharp Corp | Cofdm信号受信機 |
JPH0766793A (ja) * | 1993-08-27 | 1995-03-10 | Sharp Corp | 符号化直交周波数分割多重信号受信機 |
-
1995
- 1995-06-16 FR FR9507227A patent/FR2735636B1/fr not_active Expired - Fee Related
-
1996
- 1996-06-14 WO PCT/FR1996/000911 patent/WO1997000566A2/fr not_active Application Discontinuation
- 1996-06-14 EP EP96922924A patent/EP0836772A2/fr not_active Withdrawn
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0323675A1 (fr) * | 1988-01-06 | 1989-07-12 | Philips Electronics Uk Limited | Montage de génération d'un signal à bande latérale unique |
WO1994017599A1 (fr) * | 1993-01-28 | 1994-08-04 | Telefonaktiebolaget Lm Ericsson | Boucle de reaction a porteuses multiples cartesienne |
JPH06326739A (ja) * | 1993-05-11 | 1994-11-25 | Sharp Corp | Cofdm信号受信機 |
JPH0766793A (ja) * | 1993-08-27 | 1995-03-10 | Sharp Corp | 符号化直交周波数分割多重信号受信機 |
Non-Patent Citations (2)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 940, no. 011 & JP 06 326739 A (SHARP CORP), 25 Novembre 1994, * |
PATENT ABSTRACTS OF JAPAN vol. 950, no. 003 & JP 07 066793 A (SHARP CORP), 10 Mars 1995, * |
Also Published As
Publication number | Publication date |
---|---|
WO1997000566A3 (fr) | 1997-01-23 |
FR2735636A1 (fr) | 1996-12-20 |
EP0836772A2 (fr) | 1998-04-22 |
FR2735636B1 (fr) | 1997-07-25 |
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