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Publication numberUS3754099 A
Publication typeGrant
Publication dateAug 21, 1973
Filing dateNov 9, 1971
Priority dateNov 9, 1970
Also published asDE2155336A1
Publication numberUS 3754099 A, US 3754099A, US-A-3754099, US3754099 A, US3754099A
InventorsS Takaoka
Original AssigneePioneer Electronic Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Four channel stereophonic broadcasting system
US 3754099 A
Abstract
A broadcasting system wherein a left front, a right front, a left rear, and a right rear signal are transmitted on a single radio frequency channel with no significant increase in bandwidth. It should be compatible, that is, it should give satisfactory monophonic and two channel stereophonic reception on receivers presently in use by the public.
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United States Patent Takaoka FOUR CHANNEL STEREOPHONIC BROADCASTING SYSTEM [75] Inventor: Saburo Takaoka,l(ohoku-ku,

Yokohama-shi, Kanagawa, Japan [73] Assignee: Pioneer Electronic Corporation, Tokyo, Japan [22] Filed: Nov. 9, 1971 [21] Appl. No.: 196,932

[30] Foreign Application Priority Data Nov. 9, 1970 Japan 45/9851'3 [52] US. Cl. 179/15 RT [51] Int. Cl. H0411 5/00 [58] Field of Search 179/1 GQ, 15 BT [56] References Cited UNITED STATES PATENTS 3,708,623 1/1973 Dorren 179/15 BT (LF-LRl [451 Aug. 21, 1973 7/1972 Halpem 179/15 BT OTHER PUBLICATIONS The Quart Broadcasting System, Geryon Audio Magazine, Sept. 1970.

Quadrasonics On The Air, Feldman Audio Magazine, Jan. 1970.

Primary Examiner-Kathleen H. Claffy Assistant Examiner-Thomas D'Amico Attorney-Richard C. Sughrue et a1.

[57] ABSTRACT A broadcasting system wherein a left front, a right front, a left rear, and a right rear signal are transmitted on a single radio frequency channel with no significant increase in bandwidth. It should be compatible, that is, it should give satisfactory monophonic and two channel stereophonic reception on receivers presently in use by the public.

7 Claims, 2 Drawing Figures D CARRIER SUPPRESSED AM SIGNAL AT l9KHz (FREQUENCY OFA PILOT SIGNAL) A CARRIER SUPPRESSED AM SIGNAL AT 38 KHz (DOUBEED FREQUENCY l* [EM MODULATION OF EilOKHz AT 85.5KHz

FREQUENCY Hz V FM MOD FREQUENCY Hz FOUR CHANNEL STEREOPHONIC BROADCASTING SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to systems for the transmission of multiplex signals and particularly to systems for the transmission of four channel stereophonic signals by means of frequency modulation broadcasting, and to transmitters and receivers for use in such systems.

2. Description of the Prior Art The FM multiplex stereophonic broadcasting system, which has been adopted in Japan and is called the pilot tone system, transmits a left (or L) channel signal and a right (or R) channel signal on a single radio frequency channel and converts the signals with a receiver into L and R signals to achieve two channel stereophonic reproduction. On the other hand, there have been recently developed magnetic tapes and record discs having recorded thereon left front and right front signals in addition to left rear and right rear signals; consequently, a system for four channel stereophonic broadcasting is now demanded.

The main factors which are desirable in such a four channel system can be summarized as follows: it should be compatible, that is, it should give'satisfactory monophonic and two channel stereophonic reception on receivers presently in use by the public; it should give quality equal to present systems in frequency characteristic, distortion factor, signal-to-noise ratio and other characteristics; and it should be capable of transmission of a composite signal on about 100 KHZ or less with no significant increase in bandwidth.

SUMMARY OF THE INVENTION It is one object of the present invention to provide a novel and improved four channel stereophonic broadcasting system which is compatible with the present FM broadcasting system.

It is another object of the present invention to provide a four channel stereophonic broadcasting system which is equal in quality to the present system in frequency characteristic, distortion factor, signal-to-noise ratio and other characteristics.

It is a further object of the present invention to provide a four channel stereophonic broadcasting system in which a composite signal can be trans-mitted on about 100 KHZ or less with no significant increase in bandwidth.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an electrical block diagram of a preferred embodiment of a transmitter in accordance with the invention, and also graphical represen-tations of frequency relationships of signals used in carrying out the invention.

FIG. 2 is an electrical block diagram of a preferred embodiment of a receiver in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The system of the invention will now be described with reference to the drawings. In FIG. 1, a signal source 1 1 produces a signal representing a left front (or LP) channel, a signal representing a right front (or RF) channel, a signal representing a left rear (or LR) channel and a signal representing a right rear (or RR) channel. As indicated schematically in FIG. 1, these signals are added or subtracted to obtain an (LF LR) signal, an (RF RR) signal, an (LF LR) signal and an (RF RR) signal. Further, these signals are added or subtracted to obtain an (LF LR) (RF RR) signal (hereinafter being called only A" signal for simplicity), an (LF LR) (RF RR) signal (3" signal), an (LF LR) (RF RR) signal (C signal) and an (LF LR) (RF RR) signal (D signal).

The A signal is positioned as a main channel signal corresponding to the main signal (L R) of the present FM multiplex broadcasting system. The 8" signal, after being converted into a carrier suppressed AM signal wherein the frequency of the carrier is 38 KHZ or a doubled l9 KHZ pilot signal, is positioned as a first subchannel signal corresponding to the subsignal (L R) sin an of the present FM multiplex broadcasting systern.

The C signal and the D signal are converted in the same manner, that is, the C signal is positioned as a main channel signal (30 Hz 9 KHZ) corresponding to the A signal, and the D signal is positioned as a subchannel signal (10 KHZ 28 KHZ) corresponding to the B signal after being converted into a carrier suppressed AM signal wherein the frequency of the carrier is 19 KHZ which is the same as that of the pilot signal. The C signal and the D signal which are positioned in a frequencyspectrum are positioned as a second sub-channel (57.5 KHZ 113.5 KHZ) higher than the first sub-channel (23 KHz 53 KHZ), after being frequency modulated into 85.5 KHZ 10 KHz. As is well known only one sideband of the 85.5Khz carrier need be transmitted.

By the above converting process, the A, B, C" and D signals are converted and positioned as shown in the lower part of FIG. 1, further modulated into a frequency modulated signal by the frequency being used in a present FM stereo broadcasting system at present, and then transmitted.

Now, the receiving system of this invention will be described with reference to FIG. 2. A receiving antenna 21, an FM tuner 22 and a stereo decoder 23 are shown in a dotted line 24 and are the same as those in FM stereo receivers presently in use by the public. Therefore, the (LF LR) signal and the (RF RR) signal are led out from the output terminals of the stereo decoder 23.

One part of the output power of the FM tuner 22 is fed into an FM demodulator 25 for the second subchannel and is further frequency demodulated to produce an output signal containing the C signal and the D signal. The output signal of the FM demodulator 2-5 is fed into a stereo decoder 26 for the second subchannel to be converted into the (LF LR) signal and the (RF RR) signal by the pilot signal which is supplied from the stereo decoder 23 and then the two converted signals are led out from output terminals of the decoder 26.

The (LF LR) signal and the (LF LR) signal are fed into a matrix circuit 27 and are added and subtracted to produce the LF signal and the LR signal on the two output terminals of the matrix circuit 27. The (RF RR) signal and the (RF RR) signal are fed into a matrix circuit 28 and are added and subtracted to produce the RF signal and the RR signal on the two output terminals of the matrix circuit 28.

The received signal may be discriminated whether it is a monaural signal or a stereophonic signal by using the pilot signal being led out from the FM tuner 22, as in a prior art receiver. Furthermore, the received signal may be discriminated whether it is a two channel stereophonic signal or a four channel stereophonic signal by using the l9 KHz pilot signal being led out from the FM demodulator 25. Therefore, an automatic switching operation may be easily obtained so as to compose a reproduction circuit corresponding to either a monaural, two channel stereophonic or four channel stereophonic signal.

The present invention has many improvements, as described hereinabove. First, compatibility can be obtained, that is, the invention gives satisfactory monophonic or two channel stereophonic reception on receivers presently in use by the public. in other words, if a monaural receiver receives the four channel stereophonic signal of the present invention, the mixed signal (LF LR RF RR) can be reproduced; and, if a two channel stereophonic receiver receives the four channel signal, the left signal (LF LR) and the right signal (RF RR) are reproduced.

On the other hand, if the receiver of the invention receives a monaural signal, the monaural signal is reproduced by the front left and right and the rear left and right speakers; and, if the receiver of the invention receives a twochannel stereophonic signal, the left signal of the stereophonic signal is reproduced by the front and rear speakers of the left side, and the right signal is reproduced by the front and rear speakers of the right side. In these cases, it is, of course, unnatural that the same signal is heard from both front and rear speakers; however, it is easy to cut off the rear signals so as to eliminate the unnatural sound by using the pilot signal, the second sub-carrier of other suitable signals.

Second, the four signals, that is, the front and the rear signals of the left side and those of the right side are equal to each other in their qualities, and it is easy to get more than 30 db in channel separation between each channel.

Third, if the modulation degree of the main channel and the-first sub-channel is set at less than 40 percent, and that of the pilot signal and the second sub-channel is set at less than 10 percent, the system of the invention is capable of transmission on a present signal radie-frequency channel with no interference between neighboring radio-frequency channels.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

1 claim:

1. A four channel stereophonic composite signal broadcasting system comprising a transmitter and at least one receiver, said transmitter comprising:

a. sources of left front (LF), right front (RF), left rear (LR) and right rear (RR) stereophonically related audio frequency signals,

b. means for adding the audio frequency signals together to obtain first intermediate signals including an (LF LR) signal and an (RF RR) signal,

0. means for subtracting said audio frequency signals one from the other to obtain second intermediate signals including an (LF LR) signal and an (RF RR) signal,

d. means for adding said first and second intermediate signals to obtain an [(LF LR) (RF RR)] or A signal and an [(LF LR) (RF RR)] or C signal,

e. means for subtracting said first and second intermediate signals one from the other to obtain an [(LF LR) (RF RR)] or B signal and an {(LF LR) (RF RR)]or D" signal,

f. means for supressed carrier amplitude modulating the 8 signal on a carrier of 38 R112 producing a bandwidth of 23Khz-5Khz,

g. means for suppressed carrier amplitude modulating the D signal on a carrier of I9Khz producing a bandwidth of IOKhz-ZSKhz,

h. means for combining the C signal and the modulated D signal to produce a first composite signal in which the C signal occupies a bandwidth of 30hz-9Khz and the modulated D signal occupies a bandwidth of 10Khz-28Khz,

i. means producing a pilot signal at l9Khz,

j. means for-frequency modulating said first composite signal on a carrier of 85.5Khz i lOKhz producing a bandwidth of 57.5Khz-1 13.5Khz,

it. means for combining said A signal, said pilot signal, said modulated B signal, and said frequency modulated first composite signal to produce a second composite signal in which said A signal occupies thebandwidth 30hz-l5Khz, said modulated B signal occupies the bandwidth 23Khz-53Khz, and said'modulated first composite signal occupies the bandwidth 57.5Khz-l 13.5Khz,

1. means for frequency modulating said second composite signal, and

m. means for broadcasting said frequency modulated second composite signal.

2. A broadcasting system as defined in claim 1 wherein said one receiver comprises:

a. a first FM demodulator circuit for demodulating the received FM second composite signal,

b. a first stereo decoder for obtaining an (LF LR) signal and an (RF RR) signal by using the output signal of said first FM demodulator circuit and a pilot signal, 1

c. a second FM demodulator circuit for further demodulating the signal coming from the first FM de-' modulator circuit,

d. a second stereo decoder for obtaining an (LF LR) signal and an (RF RR) signal by using the output signal of the second FM demodulator circuit and the pilot signal, and

e. matrix circuit means for combining said (LF LR), (RF RR), (LF LR) and (RF RR) signals to obtain LF, LR, RF and RR signals.

3. A four channel st'ereophonic composite signal broadcasting system including a transmitter comprisa. sources of left front (LF), right front (RF), left rear (LR) and right rear (RR) stereophonically related audio frequency signals,

b. means for adding the audio frequency signals together to obtain first intermediate signals including an (LF LR) signal and an (RF RR) signal,

0. means for subtracting said audio frequency signals one from the other to obtain second intermediate ma M... A.

signals including an (LF LR) signal and an (RF RR) signal,

d. means for adding said first and second intermedi ate signals to obtain an [(LF LR) (RF RR)] or A signal and an [(LF LR) (RF RR)] or C signal,

e. means for subtracting said first and second intermediate signals one from the other to obtain an [(LF LR) (RF RR)] or B signal and an [(LF LR) (RF RR)] or D" signal,

. means for supressed carrier amplitude modulating the B signal on a carrier of 38 Khz producing a bandwidth of 23Khz-53Khz,

g. means for suppressed carrier amplitude modulating the D signal on a carrier of 19Khz producing a bandwidth of lOKhz28Khz,

h. means for combining the C signal and the modulated D signal to produce a first composite signal in which the C signal occupies a bandwidth of 30hz-9Khz and the modulated D signal occupies a bandwidth of lOKhz-28Khz,

i. means for producing a pilot signal at 19Khz,

j. means for frequency modulating said first compos' ite signal on a carrier of 85.5KhzilOKhz producing a bandwidth of 57.5Khzl 13.5Khz,

k. means for combining said A signal, said pilot signal, said modulated B signal, and said frequency modulated first composite signal to produce a second composite signal in which said A signal occupies the bandwidth 30hz-15Khz, said modulated B signal occupies the bandwidth 23Khz-53Khz, and said modulated first composite signal occupies the bandwidth 57.5Khz-l 13.5Khz,

1. means for frequency modulating said second composite signal, and

in. means for broadcasting said frequency modulated second composite signal.

4. A receiver for receiving the broadcast frequency modulated signal formed in accordance with claim 3, said receiver comprising a. a first FM demodulator circuit for demodulating the recieved FM second composite signal,

b. a first stereo decoder for obtaining an (LF LR) signal and an (RF RR) signal by using the output signal of said first FM demodulator circuit and the pilot signal,

c. a second FM demodulator circuit for further demodulating the signal coming from the first FM demodulator circuit,

d. a second stereo decoder for obtaining an (LF LR) signal and an (RF RR) signal by using the output signal of the second FM demodulator circuit and the pilot signal, and

e. matrix circuit means for combining said (LF LR), (RF+ RR), (LF LR) and (RF RR) signals to obtain LF, LR, RF and RR signals.

5. A method of broadcasting a four channel stereophonic composite signal comprising the steps of a. generating left front (LF), right front (RF), left rear (LR) and right rear (RR) stereophonically related audio frequency signals,

b. adding the audio frequency signals together to obtain first intermediate signals including an (LF LR) signal and an (RF RR) signal,

0. subtracting said audio frequency signals one from the other to obtain second intermediate signals including an (LF LR) signal and an (RF RR) signal,

. adding said first and second intermediate signals to obtain an [(LF LR) (RF RR)] or A signal and an [(LF LR) (RF RR)] or C" signal,

. subtracting said first and second intermediate signals one from the other to obtain an [(LF LR) (RF RR)] or B signal and an [(LF LR) (RF RR)} or 13" signal,

f. suppressed carrier amplitude modulating the B signal on a carrier of 38Khz producing a bandwidth of 23Khz-53Khz,

g. suppressed carrier amplitude modulating the D signal on a carrier of l9Khz producing a bandwidth of l0Kh2-28Khz,

. combining the C signal and the modulated D signal to produce a first composite signal in which the C signal occupies a bandwidth of 30hz-9Khz and the modulated D signal occupies a bandwidth of IOKhz-28Khz,

. producing a pilot signal at 19Khz,

. frequency modulating said first composite signal on a carrier of 85.5Khz lOKhz producing a bandwidth of 57.5Khzl13.5l(hz,

k. combining said A signal, said pilot signal, said modulated B signal, and said modulated first composite signal to produce a second composite signal in which said A signal occupies the bandwidth 30hz-l5Khz, said modulated B signal occupies the bandwidth 23Khz-53Khz, and said modulated first composite signal occupies the bandwidth 57.5Khz-l 13.5Khz,

1. frequency modulating said second composite signal, and

in. broadcasting said frequency modulated second composite signal.

6. A method as defined in claim 5, further comprising receiving the broadcast FM composite signal by:

a. frequency-demodulating the received FM second composite signal to obtain a first output signal,

b. decoding the first output signal with the pilot signal to obtain an (LF LR) signal and an (RF RR) signal,

c. further demodulating the first output signal to produce a second output signal,

(1. decoding the second output signal with the pilot signal to obtain an (LF LR) signal and an (RF RR) signal, and

e. combining said (LF LR), (RF RR), (LF 4 LR) and (RF RR) signals to reproduce the LF, LR, RF and RR signals.

7. A method of receiving the broadcast FM composite signal formed in accordance with the method of claim 5 and comprising:

a. frequency-demodulating the received FM second composite signal to obtain a first output signal,

b. decoding the first output signal with the pilot signal to obtain an (LF LR) signal and an (RF RR) signal,

c. further demodulating the first output signal to produce a second output signal,

d. decoding the second output signal with the pilot signal to obtain an (LF' LR) signal and an (RF RR) signal, and

e. combining said (LF LR), (RF RR), (LF LR) and (RF RR) signals to reproduce the LF, LR, RF and RR signals.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3679832 *Mar 23, 1971Jul 25, 1972Bell Telephone Labor IncThree-channel fm stereo transmission
US3708623 *Apr 29, 1970Jan 2, 1973Quadracast Syst IncCompatible four channel fm system
Non-Patent Citations
Reference
1 *Quadrasonics On The Air, Feldman Audio Magazine, Jan. 1970.
2 *The Quart Broadcasting System, Geryon Audio Magazine, Sept. 1970.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3902018 *Dec 3, 1973Aug 26, 1975Zenith Radio CorpMultiple channel fm stereo system employing am vestigial sideband subcarrier modulation
US3904828 *Mar 23, 1973Sep 9, 1975Siemens AgCompatible system for transmitting and receiving quadraphonic signals
US3906156 *Sep 13, 1972Sep 16, 1975Cooper Duane HSignal matrixing for directional reproduction of sound
US3944747 *Sep 28, 1973Mar 16, 1976Zenith Radio CorporationMultiple channel FM stereo system
US3965302 *Jan 28, 1975Jun 22, 1976Sansui Electric Co., Ltd.Stereo signal demodulator in a four-channel stereo broadcast receiver
US3970788 *May 16, 1975Jul 20, 1976Cooper Duane HMonaural and stereo compatible multidirectional sound matrixing
US4013841 *Jul 21, 1975Mar 22, 1977Matsushita Electric Industrial Co., Ltd.Four-channel stereo receiver
US4027107 *Dec 24, 1975May 31, 1977Zenith Radio CorporationMultiple channel FM stereo system
US4236039 *Jul 19, 1976Nov 25, 1980National Research Development CorporationSignal matrixing for directional reproduction of sound
US4301331 *Nov 15, 1979Nov 17, 1981Yurek John JComposite limiting sum and difference circuitry for extending the reception area of a frequency modulated stereo radio transmitter
Classifications
U.S. Classification381/6
International ClassificationH04S3/00, H04H20/89
Cooperative ClassificationH04H20/89
European ClassificationH04H20/89