|Title of Invention||
A METHOD OF GENERATING A VIRTUAL STEREO RADIO STATION FROM A SINGLE FM STEREO MODULATION BROADCAST
|Abstract||A method of eeneratintz a virtual stereo radio station from a single FM stereo modulation broadcast comprising the steps of dii'idijig tJie XQII and n^\X signals L dxidi R into two portions in tlie iimQXmQ l.\ and T-i; OWQ portion m tlte tinieiine being the music signal L7 i, K\\ and the other portion in the tirnehne being further di^^ided into two individual distinct YOice signals LTi/RT^, the music signal LT^, RTi and the voice signal RT2 being considered to be the defauk program; multiplexing the left and right channel signals L and R whenever the stereo broadcasting is done, that is, whenever the music "grogcmm arc broadcast; transmitting R ^ LT2 and L '=- (IR'Ti "■ LT2) ixnA /nultiplexing them mto signals M ^ (R+L) and >S =-" (R-L); shifting the pilot tone transmitted irom 3HKhz to 76 Khz. such that M sienal carries IRT? and S signal carries ICL/T^-RT^); creating a virtual radio station on the receiver side within the bandwidth allotted by the regulator)' authorit)' (in oase the original freqviency is 9^,5 it creates another frequency 98.6) without causing interference with other frequencies; mixing the virtual station frequejicy with tlie 'mcoming fm frequencies to the stereo receii^er|
This invention relates to a method of generating a virtual stereo radio station irom a single radio station from a single FM stereo modulation broadcast
h\ the present stereo hii broadcastmg system, voice based programmes are also broadcasted in stereo. The need tbr stereo transmission arises only during the bj-oadcastmg of the nujsic programs whereas the voice programs do not show any increase in audio quality due to transmission m stereo.
Tlie present invention utilizes this redundant space to create a separate virtual station, there by giving the listener the feeling of having a separate stereo station as choice to switch over.
According to this invention, the main program broadcast by the system can be heard by the existing mono/ stereo receivers as they hear them now. The proposed system will work without interfering or having any effect on the existing mono/ stereo receivers.
At present, the information broadcasted t>y a Stereo FM broadcastmg station represents two signals L,R that is being cniTently used to transport audio signals to sources respectively.
located at the left, right speakers for regular two channel Stereo receiver system and combined signal for mono receivers.
The present invention utilizes the stereo FM spectrum during the voice transmission to transmit two voice ])rograms instead of one program as done in a regular broadcast.
This invention can be implemented either as an add-on to the existing transmitters and receivers or can be inbuilt into the transmitter and receiver.
The device and the method used at the transmitter and receiver end create a virtual radio station which provides an additional choice of voice program to the listener.
This invention will now be described with reference to the accompanying drawings which illustrate by way of example in
FIG 1 showing the schematic representation of the regular FM
FIG 2 showing the schematic representation of the FM spectrum
while transniittlng the voice portion
FIG 3 sho^Ying the working of MASS device while transmitting
FIG 4 showing the working of MASS device while receiving
The normal FM stereo broadcast occupies the FM sppptmni p show in FIG 1. To make the stereo broadcasts compatible with mono receivers, the left (L) and right (R) channels are multiplexed into sum (M) and difference (S) signals, i.e. M = (L+R)/2 and S ^ (L-R)/2. A mono receiver will use imt the M signal. Stereo receivers will multiplex thp M pd S ^^0^ to recover L and R: L = M+S and R = M-^,
The M signal is transmitted as baseband audio in the range 30 Hz to 15 kHz. Th^ S signal is amplitude-modulated onto a 38 kHz suppressed carrier to produce a douWp-s idpte^n^ §W carrier (DSBSC) signal in the range 23 kHz to 53 kf^?»
A 19 kHz pilot tone, at exactly half the 38 kHz subcarrier frequency and with a precisely defined phase relationship to it, is also generated. This is transmitted at 8-10% of overall modulation level and used by the receiver to regenerate the 38 kHz subcarrier with the correct phase.
The final multiplex signal from the stereo generator is the sum of the baseband mono audio (M), the pilot tone, and the DSBSC subcarrier. This multiplex, along with any other subcarriers, modulates thp FM transmitter.
Converting the multiplex signal back to left and right is performed by a stereo decoder, which is built into stereo receivers.
In a regular FM music entertainment station there is a program that is coordinated by a performer / Radio Jockey (RJ) who interacts with listeners and plays the listener's requests etc. It is desirable to use a single transmission stream and provide the listener a choice of two distinct voice (RJ) streams.
In a regular FM news channel or a eoriJiininlJy radio ttop k continuous voice stream in one language. It k desirable te USS
this single transmission to stream a two language broadcast and provide the listener his choice of language.
The method adopted and the device disclosed by this invention provide the existing FM stereo transmitter and FM Stereo receiver systems to create a virtual radio station which allows listeners to make a choice in the same transmission and
broadcasters to transmit multi audio signals using the same transmission,
*The two channels in a regular transmission would be left and right and these signals can be transmitted in any order. In my invention we have divided the signals into two portions in the timeline. One portion in the timeline is the music signal LTi, RTi and the other portion in the timeline is divided into two individual distinpt voice signals LT2, RT2. The music signal (LTi, RTi) and the voice signal RT2 is considered to b^ the default program. Tv and T2 specify the timffUne mii L mA R represent the left and right channel signals
The left and right channel signals are multiplexed in a regular method when the stereo broadcasting is done i.e. when music programs are broadcast.
The voice program which passes through the transmission side apparatus disclosed in this invention which can be an add-on or as inbuilt upgrade to the transmission system implements an alternate methpd to transmit R = LT2 and L = (2RT2 - LT2) and multiplex them into signals, i.e. M = (R+L) and S = (R-L). The device also shifts the pilot tone transmitted fi'om 38Khz to 76 Khz. Hence M signal will carry 2RT2 and S will carry 2(LT2--
The receiver side of the device creates a virtual radio station within the bandwidth allotted by the regulatory authority (incase the original frequency is 98.5 it creates another frequ^npy 98,6) without causing interference with other frequencies and mixes this virtual station frequency with the incoming fm fi-equencies to the stereo receiver through a cable in case it is an addon apparatus to th© receiver or through an integrated cirpuitry in case in the receiver upgrade.
During the music program transmission the device deducts the 19Khz pilot signal and let go the signal in th(^ frequency created for the virtual radio station. The stereo receiver attached w^ill receive the sarne music program in stereo in the main frequency as well as in the virtual radio station created.
During the voice program transmission the pilot tone is deducted at 76 KHz by the device and separates the miiltiplexed signal i.e M and S and feeds (S+M) in M spectrum of the virtual radio station. Due to this separation the main frequency will listen to RT2 and the frequency of the virtual radio station will listen to
Thus the method and device disclosed in this invention at the transmitter side and the receiver side enable listeners to listen to the same music program but different voice programs through the virtual fadiq station created from the same FM spectrum at
the receiver 9nd.
In case the receiver has not been attached with the add-on device or in the event of there being no inbuilt upgrade then the regular receiver continues to receive the music program LTi, RT) in stereo and the vpice program RT2 in mono. In case of a monp receiver the music program and the voice program RT2 both are received in mono.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a conventional FM stereo broadcast there are two signals encoded through the use of a stereo signal generator and transmitted to receive the programs in stereo as show in FIG 1.
In accordance with the present invention a device attached to the stereo signal generator/transmitter multiplex the voice signals to transmit two distinct voice programs as shown in FIG 3. The FM spectrum of the voice programme is represented in FIG 2.
In accordance to the present invention the device attached to the receiver creates a virtual radio station from the multiplexed voice signals ^t the receiving end facilitating the user to select his voice programme of choice as represented in the FIG 4.
Referring to the drawings in which the reference numerals are designated to explain the working of the devices at the signal transmission end and in the receiving end.
1 - Voice arogmr^ 1
2 - Voice program 2
3 - Methodology to multiplex the voice signals
Si - Multiplexed voice signal for the Right channel = 2Vi S2- Multiplexe4 voice signal for the left channel = 2V2- V
4 - Right Channel input on transmitter
5 - Left channel input on transmitter
6 - FM modulator/Transmitter
1 - All FM fi-equencies received
2 - BPF for Altering the frequency for which virtual radio station to be created
3 - FM frequency for which the virtual radio station to be created
4 - Demodulator
5 - Adding of th^ multiplexed signal
6 - Pilot tone autP detector
7 - Key Switch when pilot tone is detected at 19Khz - to feed the music program in the virtual radio station
8 - Key Switch when pilot tone is detected at 78Khz - tq the second voice program in virtual radio station
9 - FM modulator for virtual radio station transmission
10 - Virtual radio station frequency
11 - Merged virtual radio station frequency with the other FM frequencies for use by the regular receiver
I.A method of eeneratintz a virtual stereo radio station from a single FM stereo modulation broadcast comprising the steps of dii'idijig tJie XQII and n^\X signals L dxidi R into two portions in tlie iimQXmQ l.\ and T-i; OWQ portion m tlte tinieiine being the music signal L7 i, K\\ and the other portion in the tirnehne being further di^^ided into two individual distinct YOice signals LTi/RT^, the music signal LT^, RTi and the voice signal RT2 being considered to be the defauk program;
multiplexing the left and right channel signals L and R whenever the stereo broadcasting is done, that is, whenever the music "grogcmm arc broadcast; transmitting R ^ LT2 and L '=- (IR'Ti "■ LT2) ixnA /nultiplexing them mto signals M ^ (R+L) and >S =-" (R-L); shifting the pilot tone transmitted irom 3HKhz to 76 Khz. such that M sienal carries IRT? and S signal carries ICL/T^-RT^); creating a virtual radio station on the receiver side within the bandwidth allotted by the regulator)' authorit)' (in oase the original freqviency is 9^,5 it creates another frequency 98.6) without causing interference with other frequencies; mixing the virtual station frequejicy with tlie 'mcoming fm frequencies to the stereo receii^er
through a cable in case it is an addon apparatus to the receiver or through an integrated circuitry in case in the receiver upgrade; deducting the 19Kliz pilot signal during the music transmission and letting go the signal in the frequency created Ibr the viituat radio station wherebv ttie stereo receiver attached receives the same music program in stereo in the main frequency as \veil as in the virtual radio station created: deductnig the pilot tone at 76 ICHz during the voice transmission and separating the multiplexed signal, that is, M and S and feeding (S+M) in M spectrum of the virtiia) radio station whereby tJic mam frequency vviJl listen to R T'2 and the frequency of tlie virtual radio station will listen to
2.A mediod of generating a virtual stereo radio station from a single FM stereo modulation broadcast substantially as herein described with reference to, and as illustrated in, he accompanying drawings.
|Indian Patent Application Number||2646/CHE/2007|
|PG Journal Number||35/2012|
|Date of Filing||15-Nov-2007|
|Name of Patentee||VALAGAM RAJAGOPAL RAGHUNATHAN|
|Applicant Address||OLD NO.6, NEW NO. 72, 12TH AVENUE, ASHOK NAGAR, CHENNAI 600 083 TAMIL NADU, INDIA|
|PCT International Classification Number||A61F 2/16B2|
|PCT International Application Number||N/A|
|PCT International Filing date|