Búsqueda Imágenes Maps Play YouTube Noticias Gmail Drive Más »
Iniciar sesión
Usuarios de lectores de pantalla: deben hacer clic en este enlace para utilizar el modo de accesibilidad. Este modo tiene las mismas funciones esenciales pero funciona mejor con el lector.

Patentes

  1. Búsqueda avanzada de patentes
Número de publicaciónWO1997039544 A1
Tipo de publicaciónSolicitud
Número de solicitudPCT/US1996/005284
Fecha de publicación23 Oct 1997
Fecha de presentación17 Abr 1996
Fecha de prioridad17 Abr 1996
Número de publicaciónPCT/1996/5284, PCT/US/1996/005284, PCT/US/1996/05284, PCT/US/96/005284, PCT/US/96/05284, PCT/US1996/005284, PCT/US1996/05284, PCT/US1996005284, PCT/US199605284, PCT/US96/005284, PCT/US96/05284, PCT/US96005284, PCT/US9605284, WO 1997/039544 A1, WO 1997039544 A1, WO 1997039544A1, WO 9739544 A1, WO 9739544A1, WO-A1-1997039544, WO-A1-9739544, WO1997/039544A1, WO1997039544 A1, WO1997039544A1, WO9739544 A1, WO9739544A1
InventoresDavid L. Herrick, David K. Murotake
SolicitanteLockheed Martin Corporation
Exportar citaBiBTeX, EndNote, RefMan
Enlaces externos:  Patentscope, Espacenet
Method for digital broadcasting over the commercial fm band
WO 1997039544 A1
Resumen
A method for broadcasting digital data (146, 150) over a limited bandwidth, FM broadcast channel in addition to a normal monaural or stereophonic analog signal, includes compressing (152) or decimating (148) the digital data to be transmitted, phase modulating (140) the compressed or decimated digital data onto a subcarrier signal within an unused upper portion of a limited bandwidth channel to form a modulated digital data signal, modulating (144) an FM transmission carrier signal with the digital data signal and a baseband monaural or stereophonic analog signal, and transmitting (136) the modulated FM carrier signal. The present invention can be applied to any regulated FM broadcasting spectrum which includes unused bandwidth between stations, to more efficiently use that bandwidth without adding interference.
Reclamaciones  (El texto procesado por OCR puede contener errores)
sWHAT IS CLAIMED IS:
1. A method for FM broadcasting digital data over a limited bandwidth, FM broadcast channel in addition to a normal monaural or stereophonic analog signal, comprising the steps of: compressing or decimating the digital data to be transmitted; phase modulating the compressed or decimated digital data onto a subcarrier signal within an unused upper portion ofthe limited bandwidth channel to form a modulated digital data signal; modulating an FM transmission carrier signal with the digital data signal and a baseband monaural or stereophonic analog signal; and transmitting the modulated FM carrier signal.
2. The method of claim 1 , further comprising the steps of: receiving the transmitted signal at one or more locations; separating the modulated digital data signal from the analog signal; demodulating the separated digital data signal; and decompressing the demodulated digital data.
3. The method of claim 1 , wherein the step of modulating an FM transmission carrier signal includes the steps of combining the modulated digital data signal with the baseband signal and then modulating the FM carrier signal.
4. The method of claim 1 , wherein the limited bandwidth, FM broadcast channel is a standardized 200 kHz. FM channel.
5. The method of claim 4, wherein the unused upper portion of the standardized 200 kHz. FM channel is allocated for communications which are subsidiary to the baseband signal.
SUBSTTTUTE SHEET (RULE 26)
6. The method of claim 1 , wherein the step of modulating the digital data onto a subcarrier signal is accomplished by quadrature amplitude modulation.
7. The method of claim 1, wherein the step of receiving the transmitted signal includes the step of compensating for signal distortion produced between the steps of transmitting and receiving.
SUBSTTTUTE SHEET (RULE 26)
Descripción  (El texto procesado por OCR puede contener errores)

METHOD FOR DIGITAL BROADCASTING OVER THE COMMERCIAL FM BAND

Background of the Invention Field of the Invention

The present invention generally relates to commercial FM broadcasting, and particularly, to digital broadcasting over existing FM station allocations. Statement of the Prior Art

FM broadcast stations and information service providers use a 20 MHz. frequency band which is divided by Federal regulation into 100 channels of 200 kHz. for each station. Currently provided services are typically analog and include either a monaural or stereo primary baseband signal and a maximum of two or three subcarrier or subsidiary broadcast signals. Broadcasters are prohibited from charging for their primary or main broadcast signal, but are permitted to use their subsidiary broadcasts for revenue bearing services such as functional or background music, specialized foreign language programs, radio reading services, utility load management, market and financial data and news, paging and calling, traffic control signal switching, bilingual television audio, and point to point or multipoint messages. These broadcast service providers are facing increased competition from other forms of transmission and entertainment media such as cable television, compact discs (CDs), satellite TV, and computer modems, many of which employ high quality digital formats. As a result, FM broadcasters are seeking additional revenue producing services for their subsidiary communications broadcasts. There is interest in transmitting CD quality digital audio, as evidenced by one transmission format called ln Band, On Channel (IBOC) Digital Audio Broadcast (DAB). Unfortunately, this format may not provide the bandwidth necessary to broadcast CD quality digital audio within the existing

SOBSTTΓUIE SHEET (RD1£ 26) station channel allocation, or may interfere with existing services. IBOC DAB may also fall outside the current limitations for the subsidiary communications services and thereby limit the digital broadcasts to "free access" services as required by Federal regulations. Thus, this technique would not improve the competitive position of FM broadcasters.

Summary of the Invention Accordingly, it is an objective of the present invention to provide a method for the FM broadcasting of digitally formatted data.

It is a further objective to provide such a method which operates within the currently regulated, subsidiary communications allocation.

It is yet a further objective to provide such a method which provides contemporaneous digital quality audio broadcasts.

The present invention provides a method for FM broadcasting digital data over a limited bandwidth, FM broadcast channel in addition to a normal monaural or stereophonic analog signal, comprising the steps of compressing or decimating the digital data to be transmitted, phase modulating the compressed or decimated digital data onto a subcarrier signal within an unused upper portion of the limited bandwidth channel to form a modulated digital data signal, modulating an FM transmission carrier signal with the digital data signal and a baseband monaural or stereophonic analog signal, and transmitting the modulated FM carrier signal.

Brief Description of the Drawings The present invention is illustratively described in reference to the appended drawings in which: Fig. 1 is a baseband frequency spectrum diagram ofthe currently regulated FM broadcast format showing transmission schemes used in the Prior Art;

SUBSπiUTE SHEET (RULE 26) Fig. 2 is a baseband frequency spectrum diagram of an FM broadcast signal used in accordance with one embodiment of the present invention; and

Fig. 3 is a block diagram of a system constructed in accordance with another embodiment of the present invention. Detailed Description of the Drawings

Fig. 1 shows a frequency spectrum diagram of a single sideband of a 200 kHz. wide commercial FM broadcast channel as established by 47 C.F.R. 73.201. The horizontal axis shows frequency in kHz. and thus spans 1 00 kHz., or a full side band of the normal FM channel allocation. The signals represented would be used to frequency modulate a carrier signal in accordance with a regulated channel assignment. The arrow or signal spike 1 10 would represent the location of the carrier frequency upon modulation.

The standard FM signal shown includes a baseband monaural signal 1 12 which spans 50 Hz. to 15 kHz., a stereo pilot signal 1 14 at 19 kHz., and a suppressed stereo subcarrier 1 15 at 38 kHz. surrounded by lower and upper stereo sidebands 1 16, 1 17, respectively, between 23 kHz. and 53 kHz.. In addition, the signal includes a pair of subsidiary signals 1 1 8, 1 19 at 63 kHz. and 93 kHz., located within the subsidiary communications allocation (SCA) 120 between 53 kHz and 99 kHz., as defined by 47 C.F.R. 73.319. These supplemental carriers 1 18, 1 19 are currently used by a number of FM stations to transmit revenue bearing, subscriber services such as background music and data (i.e. stock quotes). The SCA 120 is limited in the percentage of overall station power it can contain and signals therein are restricted from interfering with the primary signal or adjacent channels. Fig. 2 shows an FM broadcast spectrum diagram 123 used in accordance with the present invention. The spectrum diagram 123 is similar to that of Fig. 1 except that the supplemental carriers 1 1 8, 1 19 are replaced by a modulated signal 122 in accordance with the method of the present invention. Modulated signal

SUBSTITUTE S8EET (RULE 26) 122 may take the form of a single signal or a plurality of signals. The remaining elements shown in Fig. 2 are identical to the elements in Fig. 1 which bear the same identification numbers.

The signal 122 is located in the SCA 120 between 53 kHz. and 99 kHz. and it may be modulated by any suitably efficient method. In one embodiment the subsidiary signal may be produced by quadrature amplitude modulation (QAM) of a subcarrier signal by the digital data to be transmitted. This method varies the phase and amplitude ofthe subcarrier in accordance with the digital data. In one example of QAM, a sixteen point constellation is used made up of four different amplitude levels and four different phase values between -π and +π, with each point representing a binary value between 0 and 15. The digital data to be transmitted would be directly represented by the constellation points during transmission. The digital data used for transmission may be of any form such as unprocessed, compressed, decimated, coded, etc., depending upon the desired transmission efficiency.

Fig. 3 shows a block diagram of a transmitter/receiver system 130 generally including transmitter portion 132 and at least one receiver portion 134. Transmitter portion 132 includes an analog transmitter 136 coupled to an antenna 138. The input signal for transmitter 136 is formed in a phase linear pre-equalizer 140 which receives a baseband signal from a summation module 142 and a subcarrier modulated subsidiary signal from a digital SCA modulator/multiplexer (digital m/m) 144. Pre-equalizer 140 pre-compensates for phase nonlinearity which is inherent in transmitter 136. The inputs to summation module 142 are the traditional elements depicted in Fig. 1 and are labeled accordingly. Provision is even made for optionally inputting traditional SCA signals 1 18,1 19.

Digital m/m 144 alternatively receives inputs from the various types of digital data which may be transmitted. Included in this variety are ordinary

SUBSπTUTE SHEET (RULE 26) digital data 146, digital audio which is first passed through a decimation module 148 and digital multimedia 150 which is first passed through a decimation/compression module 152. The decimation and/or compression modules 148, 152 are required for the efficient use of the limited broadcast spectrum of the SCA 122. This allows the SCA to accommodate a pair of digital quality audio channels to be broadcast in a single SCA as well as for higher speed video than would otherwise be available in a single SCA. Maintaining the necessary bandwidth below that of a single SCA allows optimum usefulness by single station broadcasters. Dual station broadcasters benefit from a proportional bandwidth increase.

Receiver portion 134 may be one of many within system 130 and includes an analog receiver 160 having an input coupled to an antenna 162 and a demodulated output coupled to a channel equalizer 164. The output of channel equalizer 164 is coupled to a digital SCA demodulator/demultiplexer (digital d/d) 166 which separates whichever form of digital data has been transmitted over the SCA 120. The baseband audio signal which is also transmitted may be demodulated elsewhere by an ordinary FM receiver such as 160. Any decimated and/or compressed digital multimedia may be coupled through a comparable bit smoother/decompressor 168 for the appropriate signal reconditioning.

The benefits of decimation, compression, etc. in combination with the remainder of the described embodiments are readily apparent. The standard data rate for digital audio compact disc (CD) and CD- ROM playback is 1.5 mbps. Psychoacoustic decimation techniques, such as the Bose AC-2 method, can reduce the required signal data rate to 180-256 kbps, depending upon a quality factor, which decimated signal, according to broadcast industry experts, cannot be aurally differentiated from an undecimated CD playback by a human listener. Similarly, digital compression and video frame decimation methods can

SUBSπTUTE SHEET (RULE 26) reduce the data rate of multimedia transmissions to 420 kbps or less, resulting in an audio-visual multimedia presentation similar in quality to current music videos. To accomplish this, full motion video frame update rates of 30 frames per second are decimated to an average of 8 frames per second or less, with interpolation used for "bit smoothing".

In certain transmission environments multipath signal reception may be as problematic with embodiments ofthe present invention as it is with existing FM broadcasts. Basic multipath causes interference as a delayed echo of the received signal. Receiver 160 may include one or more algorithms for reducing the problem. One simple approach would be to subtract a delayed fraction of the received signal from itself to cancel the delayed multipath signal. Monitoring the phase synchronism ofthe QAM signal would provide data for adjusting the delay and determining the appropriate fraction of the received signal. The delay could be smoothly adjusted by use of a dispersive delay line whose delay is proportional to it's center frequency. This dispersive delay line would have an up converter on the input and a down converter on the output, with both converters being fed by the same local oscillator to cancel short term frequency drift. Varying the frequency of this local oscillator would allow for smooth and continuous adjustment of the time delay. Multipath compensation may also be accomplished by digital algorithms which would also provide greater flexibility for dealing with more than one multipath signal.

Conclusion

The present invention enables FM broadcast stations to add revenue bearing broadcast services within the subsidiary communications allocation without interfering with existing "free access" broadcast services. Such services may include one or two CD quality digital stereo audio channels, or some combination of digital multimedia, digital audio, and digital data services. Thus,

SUBSΠΠΠE SHEET (Mft£ 26> existing transmitters and receivers would remain in use while the market is expanded via the subsidiary broadcasts. Optimum use is made of the limited SCA bandwidth, enabling income producing use by even single station broadcasters. The present invention further avoids any need for changing current broadcast regulations and readily accommodates future digital upgrades io the main broadcast signals of any station.

The embodiments described above are intended to be taken in an illustrative and not a limiting sense. Various modifications and changes may be made to the above embodiments by persons skilled in the art without departing from the scope of the present invention as defined in the appended claims. The term 'commercial' used in describing the Federally regulated FM broadcast channels is intended to include not-for-profit, public broadcast allocations.

SUBSTITIITE SHEET (RULE 26)

Citas de patentes
Patente citada Fecha de presentación Fecha de publicación Solicitante Título
US4803727 *24 Nov 19877 Feb 1989British Telecommunications Public Limited CompanyTransmission system
US5155769 *12 Abr 199113 Oct 1992Aphex Systems, Ltd.Discrete parallel path modulation multiplexer
US5161251 *29 Jul 19913 Nov 1992Mankovitz Roy JApparatus and methods for providing text information identifying audio program selections
US5191615 *17 Ene 19902 Mar 1993The Drummer GroupInterrelational audio kinetic entertainment system
US5315583 *11 Abr 199124 May 1994Usa Digital RadioMethod and apparatus for digital audio broadcasting and reception
US5408686 *30 Oct 199218 Abr 1995Mankovitz; Roy J.Apparatus and methods for music and lyrics broadcasting
Citada por
Patente citante Fecha de presentación Fecha de publicación Solicitante Título
WO2002009329A2 *20 Jul 200131 Ene 2002Thomson Licensing S.A.An in-band-on-channel broadcast system for digital data
WO2002009329A3 *20 Jul 200127 Mar 2003Manuel ApraezAn in-band-on-channel broadcast system for digital data
US679205125 Jul 200014 Sep 2004Thomson Licensing S.A.In-band-on-channel broadcast system for digital data
US73889114 Ago 200417 Jun 2008Thomson LicensingIn-band-on-channel broadcast system for digital data
Clasificaciones
Clasificación internacionalH04H20/34
Clasificación cooperativaH04H20/34, H04H2201/183
Clasificación europeaH04H20/34
Eventos legales
FechaCódigoEventoDescripción
23 Oct 1997ALDesignated countries for regional patents
Kind code of ref document: A1
Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE
23 Oct 1997AKDesignated states
Kind code of ref document: A1
Designated state(s): AU BR CA CN JP MX
14 Ene 1998121Ep: the epo has been informed by wipo that ep was designated in this application
19 Feb 1998DFPERequest for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
5 Mar 1999NENPNon-entry into the national phase in:
Ref country code: JP
Ref document number: 97537045
Format of ref document f/p: F
1 Sep 1999122Ep: pct application non-entry in european phase
17 Oct 1999NENPNon-entry into the national phase in:
Ref country code: CA