EP0847157A2

EP0847157A2 - Arrangement for optimizing the utilization of frequencies through time-division multiplexing of stereophonic broadcasts

Info

Publication number: EP0847157A2
Application number: EP19970121048
Authority: EP
Inventors: Juan José Maria Lago; Emilio Oscar Caime; Julio Miguel Di Giusto; Néstor Rogelio Orlando
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-12-04
Filing date: 1997-12-01
Publication date: 1998-06-10
Also published as: BR9705938A; IT1297568B1; ES2140326B1; ES2140326A1; ITUD970223A1

Abstract

The arrangement processes the stereophonic information to be transmitted by means of two or more RF modulated channels either on air or through the telephone line or again through wires that may or may not carry energy. To this purpose, the stereophonic information means are introduced: the left-hand and right-hand audio channels, integrating the transmission baseband by means of a subcarrier in the 19 kHz region, with the sequential suppression in alternating form of the sidebands of said channels, and connected with the RF tansmission means. The receiver means include, at the output of the demodulator means, decoder means inverting the above mentioned alternating sequence, said means including an integrated comparator circuit and an integrated commutator circuit. Said stereophonic information means can also be connected to time-division multiplexing coder means, along with radio-frequency generator means and frequency-divider means.The RF is modulated by means of an electronic commutator, wherein pulses of the signals corresponding to the left-hand and right-hand channels are alternated at a rate in the region of 13 microseconds. The modulator means connect with respective mixer means connected in turn to the transmitter means constituted by an adder means forming a multiple transmission head unit.

Description

The present invention refers to an arrangement for optimizing the utilization of the frequencies by means of time-division multiplexing of stereophonic broadcastings, to the main purpose of obtaining an improved distribution of the spectrum of the frequencies that are used during stereophonic broadcasting so as to increase the number of available channels.

The main purpose of the present invention is to provide a new electronic arrangement that enables two or more monophonic or, preferably, stereophonic frequency-modulated music channels to be broadcast either on the air or by means of any two-wire installation that may or may not carry energy, such as for instance a point-to-point telephone link, without interfering with the related service.

Such an aim according to the present invention is reached in the utilization of modulated frequency, owing basically to its widely known property of being immune from the noises that may be generated by contiguous lines, industrial power generators, nearby machinery, atmospheric disturbances and the like, so that it actually proves to be ideal in view of being used in connection with the above mentioned broadcasting applications.

The frequency band selected to reach the aim according to the present invention is preferably the one which ranges from 100 kHz to 450 kHz.

The above cited arrangement is time-division multiplexed and essentially consists of a kind of electronic key that alternatingly commutates two distinct signals.

In an application, the transmission of information is a stereophonic music broadcast, by which the left-hand channel and the right-hand channel are sent by leaving on a side the monophonic signal of the standard large-band transmission used in regular broadcasting, to the extent that the width of the stereophonic channels to be transmitted is reduced to 50 kHz, which corresponds to the fourth part of the above mentioned standard values.

On the other hand, in a preferred embodiment of the invention, the signals of each one of the channels will keep within 15 kHz with a maximum deviation of 50 kHz. The arrangement is supplied with a signal issued by a modulated-frequency generator of a conventional type. Audio signals can be converted in digital form and compressed in any appropriate manner in the multiplexing arrangement according to the present invention.

It is a further purpose of the present invention to provide an arrangement for transmitting and receiving information by telephone line through frequency modulation of a radio-frequency carrier wave, so that the signal containing it will no suffer any degradation over considerable lengths of wire, wherein data are transmitted at a speed that is limited only by the modems which are used as an interface between a PC and the signal-emitting device.

Modems used to transmit data through a telephone line are generally known to convert such data into digital sound pulses ranging between 1500 and 2700 kHz, which means that they practically cannot exceed the passband of telephone exchanges, which is comprised between 300 and 3500 kHz.

Thanks to the present invention, the width of the above mentioned band can be left out of consideration, since a frequency-modulated radio-frequency signal is sent through the telephone means, in a spectrum that actually enables the bandwidth to be extended, thereby obtaining a greater transmission and reception speed.

In this way, a further aim of the present invention is reached in that information is sent between users and a central station through so-called point-to-point links, thereby obtaining the circulation of data by means of the line conductors without any interruption in the voice traffic involved by the basic telephone service, so that both services, ie. voice and data (eg. music) transmission, can be rendered simultaneously, since the frequencies used do not interfere with each other.

As already mentioned above, the arrangement frequency-modulates the spectrum ranging from 100 to 450 kHz, wherein it reserves the space comprised between 100 and 200 kHz to the transmission of commands and the space comprised between 250 and 450 kHz to the reception or return, whereas the intermediate sector from 200 to 250 kHz, which is not modulated, serves the purpose of avoiding intermodulations between transmission and reception and to this end makes use of low-pass and high-pass filters.

It is a further purpose of the invention to provide arrangements for transmitting and receiving radio-frequency bands in general, said arrangements including a decoder for optimizing, through multiplexing, the utilization of the frequencies in broadcast transmissions, since a greater number of channels is thereby obtained, within the same frequencies that are available, for transmitters comprised in a determined broadcasting spectrum. Bandwidths of 60 kHz are in this way attained, instead of the usual 200 kHz, so that the modulator multiplexes by time division the stereo signals in the baseband by means of an electronic key that alternatingly commutates the transmission of the signals corresponding to the right-hand channel with those corresponding to the left-hand channel, thereby modulating up to 70% of the signal. This circumstance ensures that, during the transmission sequence, when for instance there is a signal in the right-hand channel, the left-hand channel is not present, since the missing sideband of the right-hand channel covers the space of the left-hand channel, and so on subsequently in the spaces of time assigned for said alterations. Therefore, the applied decoder unit is provided, as this will be described in a more detailed manner further on, with a transmission sequence inverter block.

In an embodiment of the present invention, a 19-kHz subcarrier and a commutation time divided into spaces of 13 microseconds each have been used. Such a commutation time cannot be perceived by the human ear and for this reason the signals turn actually out to be audibly continuous and fully separate from each other in both channels.

On the other hand, the invention will then enable a greater coverage area to be obtained for on-air broadcasts with a power equal to the usual one, or else the same coverage area to be obtained with a broadcast of lower power and energy usage.

The features of the invention are such as to make it compatible with conventional receivers currently available and used on the market.

It therefore ensues that the aims according to the present invention are reached in the frequency or amplitude modulation of either stereophonic or monophonic signals transmitted in a time-division multiplexed form with a 100% separation between channels in stereophonic transmission and reception, along with a smaller occupation of the RF badwidth.

The arrangement that is described below comprises essentially an installation which is provided for the transmission of six channels and is essentially constituted by a modulated-frequency generator, a multiplexor generator and a multiplexor coder, which channels, starting from a multiple transmission head pass through a mixer to the telephone line and, following the distribution route of the existing telephone network, reach the users, each one of them being provided with his/her own receiver apparatus comprising a low-pass input filter, a tuner from which, after a new filtration, they reach the demodulator and the decoder from which each channel is then amplified. The telephone line used to this purpose remains operationally separated.

Each one of the above elements features its own, peculiar characteristics in view of performing its own task in an optimum manner, so as this will be described in greater detail further on.

In a simple embodiment of the present invention, applied to transmissions by telephone line, the electronic configuration of the station providing the telephone service is again left out of consideration, so that no limits are actually set to the transmission speed which, as this has already been stated above, will basically depend on the modems installed at both its ends. It comprises a modulated-frequency carrier wave modulator/demodulator connected between the telephone line and a computer modem. Said modulator/demodulator comprises an emitter stage including a voltage-controlled oscillator and a FM-baseband generator with RF-pass filters, and connected to a separator stage exciting an output transistor having its collector connected to a telephone-line coupling transformer, whereas the receiver stage comprises an input stage with respective high-pass and low-pass filters according to the extremities, tuned on the frequency of the carrier wave and connected to a phase-locked oscillator with the output thereof directly connected to the computer modem.

As regards the decoder for otpimizing the utilization of frequencies by means of time-division multiplexing of broadcast transmissions, this is substantially and preferredly formed by a time-division multiplexor processing block for each one of the channels, starting from the block constituted by the audio source, the channels of which integrate the transmission baseband of 10 to 15 kHz and a subcarrier having a frequency in the order of 19 kHz for controlling both left-hand and right-hand channels that are sequentially suppressed in an alternate manner, and are connected to the RF transmission block, whereas the radio receiver includes, at the output of the demodulator block, a decoder block inverting the alternating sequence imposed to said right-hand and left-hand channels, said decoder block comprising a level-boosting transistor, after which they are input in a commutator IC, the circuit of which includes a divider IC and a phase-comparator IC, the latter being controlled by a master oscillator, and a second conditioning transistor of a divider IC.

Various arrangements are known in the art which are set up to provide a music broadcasting service transmitted by a radio station emitting in frequency modulation with a pair of channels that can be selected according to the type of music that one desires to listen to, whereas the user must install a receiver with an appropriate decoder if he/she wants to be admitted to the service. The broadcast music is monophonic.

A further service is known which, supplied by the radio in amplitude-modulated form, enables half a dozen channels to be acceded to, each one of them transmitting a well-determined kind of music, whereas transmissions are in all cases amplitude-modulated monophonic ones.

Said service can as well be recived through the telephone line, wherein it maintains the peculiarity of being monophonic.

The major drawbacks of all such methods lie in the absence of stereophonic effects, since transmissions are in all cases monophonic, in the bandwidth that is occupied, as well as the noise interferences.

Such drawbacks are eliminated by the present invention through the use of an unconventional frequency modulation system, from which the signal is emitted in stereophony without carrier and occupying a much narrower bandwidth. To reach the aims of the present invention, the signal is narrowed to 15 kHz in analogue form.

SHORT DESCRIPTION OF THE DRAWINGS

The illustrations appearing in the accompanying drawings are as follows:

Figure 1 is a block diagram representing the multiplexor generator that is part of the present invention;
Figure 2 is a block diagram of the user-side radio-frequency receiver apparatus used in connection with the present invention;
Figure 3 is block diagram corresponding to a transmission head unit of the installation, according to the principles of the present invention;
Figure 4 is a block diagram of the distribution in the telephone network, complementing the previous Figure;
Figure 5 is a preferred schematics of the electronics of the multiplexor coder which is an integral part of the present invention;
Figure 6 is a part of the above electronic diagram and represents a modulated-frequency generator;
Figure 7 integrates an electronic circuit corresponding to one of the arrangements according to the present invention, and corresponds to the stereo decoder applied to the invention;
Figure 8 is a co-ordinate diagram showing the frequency spectrum used for the multiplexed stereo signals of 15 kHz and 15 kHz, and the corresponding bandwidth;
Figure 9 is a co-ordinate diagram of a composite stereo signal, for the comparison thereof;
Figures 10 illustrate the frequency patterns used for an arrangement according to the present invention, where a) is for the reception and transmission frequencies of the server and b) for the frequencies of the user;
Figure 11 is a block diagram of the radio-frequency unit;
Figure 12 is a block diagram showing the connections of an arrangement according to the invention to the telephone means;
Figure 13 is an electronic diagram of the radio-frequency unit;
Figure 14 is a block diagram of the decoder;
Figure 15 is a view of comparative schematic diagrams of a conventional transmission system and a multiplexed system according to the present invention;
Figure 16 is an electronic circuit implementing the block diagram shown in Figure 14.

In all above listed Figures, the same reference numerals are used to indicate similar or corresponding items.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1, the described multiplexor generator can be noticed to be constituted by a first 456-kHz oscillator block conditioned electronically to divide by six said frequency, which therefore gives a result of 76 kHz. Such a frequency is then sent to a divider-by-2 block which reduces it to 38 kHz, such a frequency being in turn processed in another divider-by-2 block and is at the same time supplied to a multiplexor block jointly with the left-hand and right-hand audio-frequency channels. From such multiplexor block, and passing through a ceramic filter, it enters the mixer block along with the 19-kHz signal resulting from the division by six of the oscillator frequency, from the block of which the output of the muitiplexor is obtained.

Figure 2 is a block diagram of the user receiver apparatus. At the input side of the telephone line there is provided the low-pass filter block followed by the tuner block. The resulting signal is sent to a ceramic filter that is followed immediately first by the demodulator block and then by the decoder block to which the amplifier blocks corresponding to the left-hand and right-hand channels are connected. The conventional sound reproducing system may be a compact disc, a hard disc, a magnetic tape, satellite signals picked up by a receiver, etc. Said receiver apparatus includes a microprocessor-based automatic sequencer of music themes.

Figure 3 illustrates an embodiment of the transmission head unit of the arrangement, which accomodates, in this case, a plurality of six analogue channels that are formed sequentially by a first sound reproducer block D linked to a second microprocessor-based automatic music-theme sequencer block C, which is followed by a third block A representing an audio processor, from which each modulator block M and, from there, an adder block S is supplied From the latter block, the signals are then input in the telephone network RT for transmission.

Figure 4 completes the transmission block diagram starting from the last adder block. The signal enters the input telephone exchange, or block CTA, from which it then can take the appropriate route to other peripheral telephone companies CTP. From each such company the signal then continues to travel along the respective telephone lines LT until it reaches either the private user UD or commercial users UC, such as offices, hotels, trading centers and the like.

From the representative blocks thereof, the line remains on one side available for telephone communications T, while it on the oher side inputs in the RF-receiver block R, which will described in greater detail separately, and from the latter in the speaker network P or the respective audio equipment EA, from which the so received music is diffused appropriately.

The electronic diagram appearing in Figure 5 illustrates in detail the construction of a multiplexor coder circuit according to the present invention.

Said circuit is formed essentially by a 456-kHz oscillator that includes a ceramic filter FC and a field-effect triode FET whose output is connected to a divider-by-six represented by the integrated circuit IC1.

The integrated circuits IC2 and IC3 accomodate a pair of dividers. The integrated circuit IC2 consists of a divider by two and by four, wheras the integrated circuit IC3 is a divider by three. A divider-by-two can easily be obtained by connecting the output QA to the input D and applying the frequency to be divided to the clock input. Both dividers are used in the above mentioned schematics.

As an electronic commutator switch an integrated circuit IC4 is used, which has been appropriately selected in view of its characteristics of switching speed and channel separation. In this particular case, the terminal 13 is used for the right-hand channel and the terminal 3 for the left-hand channel.

In conclusion, it will occur that when the terminal 13 is at logic level 1 at its output and at the input to the adder, it is the right-hand signal that is present; the same will occur as far as the left-hand signal is concerned.

A variable-amplitude pilot signal may possibly be aggregated at the input of the operational adder IC5.

Anyway, on the signal input side there are provided two frequency-limiting operational elements IC7 , ie. e right-hand and a left-hand one, which contain a frequency-limiter network to limit frequency to 15 kHz, and whose respective outputs lead to two equalizer operational elements IC6, which are equalized with a pre-emphasis of 50 microseconds to the purpose of improving the signal-to-noise ratio.

The radio-frequency generator illustrated in Figure 6 comprises a coil with a frequency of 456 kHz and a VCO element electrically associated to a pair of appropriately biased transistors to obtain the desired oscillations.

The decoder circuit of Figure 7 is a simple one and is based on an integrated circuit IC11 that contains a phase-locked loop PPL to regenerate either a pilot signal or a signal of its own in view of achieving the separation of the two channels. It also includes an indicator consisting of a LED device.

Figure 8, which represents the spectrum of frequencies used for six channels, shows the width of the band comprised between 100 and 450 kHz, wherein each one of the channels is distributed at 140, 190, 240, 290, 340, 390 and390 kHz with an available aplitude of 50 kHz for a stereo signal of 15 and 15 kHz.

Figure 9 illustrates the composite stereo signal, wheras following distributions can be compared in it.

Monophonic	100% = 75 kHz Deviation
Monophonic	75% = 33.75 kHz Deviation
19-kHz Signal	10% = 7.5 kHz Deviation
Left-Hand Channel	22.5% = 16.875 kHz Deviation
Right-Hand Channel	22.5% = 16.875 kHz Deviation
Total Stereo Signal	= 75 kHz Deviation

With reference to the ambodiment variant illustrated in Figures 10 through to 13, it can be noticed from the diagram appearing in Figure 10a) that the frequency spectrum situated between 100 and 450 kHz, so as it is used by the central "server" unit, is determined by the low-pass and high-pass filters. It can be noticed that the band comprised between 250 and 450 kHz is used for transmission, the division of the frequencies between reception and transmission being determined by the suppression defined by a notch filter.

The diagram in Figure 10b) illustrates the case of the user wherein the same principle is adopted as for the above described central unit. From these two Figures it is possible for the bandwidths to be inferred which are used by both the server and the user.

According to the illustration appearing in Figure 11, it can be noticed that the signal received at the telephone input is filtered in the corresponding input filter which consists of determined band-pass filters. After passing through the demodulator, the signal is sent to the modem which is connected to the data processor.

During the data emission from said processor, the signal received by the modem is received in the FM-generator and, once it has been filtered in the output filter, which also consists of determined band-pass filters, it is returned to the input telephone line.

In this case, both the demodulator and the modulator receive their power supply from the mains to which they are connected through a line filter.

Figure 12 illustrates how the various PC computer units of each user are connected with the central unit, or "server", through their respective modems and the above described units, on the telephone lines.

Figure 13 illustrates the electronic circuit which, for the transmission of the data, has an integrated circuit IC1 of the VCO type (voltage-controlled oscillator) which, connected to the modem, generates the baseband for the FM, whose output is connected through the variable excitation-adjustment capacitor C1 to the base of the RF-exciting transistor T1, said base being biased by means of the resistor R1. The emitter of said transistor T1 is connected to ground through the biasing resistor R2 in parallel with the capacitor C2, whereas the collector thereof is connected to the tuned load L1 which is in series with the RF choke L2. The collector of the transistor T1 is in turn connected through the capacitor C4 to the base of the output transistor T2, said base being biased by means of the resistor R3 in parallel with the capacitor C5, whereas the emitter thereof is biased by means of the resitor R4 in parallel with the capacitor C6.

The collector of the output transistor T2 is connected to the RF output transformer LT1 which in turn is connected to the telephone line TEL. Said transformer is in series with the RF choke L3 and the capacitor C7 is grounded.

For the reception, the telephone line supplies the signal to the input filter F1, which is a low-pass filter in "server" and a high-pass filter in user and whose output supplies the integrated circuit IC2 of the Pll type (phase-locked loop) which has its output connected to the modem of the computer of the user. In the circuit supply there are connected the source-filter capacitors C7 and C8.

In the variant of application of the present invention according to Figures 14 to 16, it can be noticed from the illustration in Figure 14 that the block 1 represents the audio source with its left-hand channel L and right-hand channel R that will be processed in the baseband multiplexor processor block 2, the signals of which are then sent to the transmission RF generator block 3.

The emitted processed signals are received by the radio receiver block 4 that includes the decoder block 5 which in this case supplies the channels L and R in audio frequency.

Figure 15 illustrates the carrier without modulation P represented by a simple axis. A carrier with monophonic modulation M is then joined thereto, followed by the carrier with stereo modulation S. The contiguous diagram shows the multiplex modulation according to the invention, with the left-hand channel L and the right-hand channel R, the electronic switching key C and the result of the sequence to be transmitted.

Figure 16 illustrates a possible embodiment of the electronic circuit corresponding to the decoder that is incorporated in the receiver apparatus, the basic component parts of which are identified in the circuit diagram.

Such component parts include the integrated circuits the basic characteristics of which are: IC1 is an electronic comparator and IC2 is an electronic commutator; the circuit includes the transistors T1, T2 and T3.

The reference E is used to indicate the already demodulated signal; SL is used to indicate the output of the left-hand channel and SR the output of the right-hand channel.

The demodulated signal E is sent to the integrated circuits IC1 and IC2, to the integrated comparator IC1 through the resitor R2 and the capacitor C1, which is connected to the base of the transistor T1, which is biased by means of the resistors R1 and R2 and is channelled to the integrated circuit IC1 by its collector through the capacitor C2, wheras its emitter is connected to ground. The above mentioned signal E also reaches the IC2 directly.

Said IC comprises a LED indicator, connected at its pin 6, and the resistor R3 in series with the variable resistor R4 adjusting the VCO value fof the voltage-controlled oscillator thereof, which acts as the FM baseband generator.

At the outputs of the comparator IC1 there are connected respective transistors T2 and T3 with the bases thereof biased by the resistors R15 and R5, respectively, and coupled through the capacitors C4 and C3. Both emitters thereof, connected to ground, generate inverted square-wave pulses that are applied to the inputs of the commutator IC2. The respective outputs, as appropriately biased through the resistors R12 and R13 and balanced by means of the variable resistor R14, constitute the output SL of the left-hand channel and the output SR of the right-hand channel through the capacitors C7 and C8.

OPERATION

Having in this way cited and described the various main component parts that are used to embody the present invention, which have been developed and illustrated to the main end of explaining the nature and basic simplicity thereof, the above description is completed below with the illustration of the actual operation and function of all said component parts and the overall result of such operation, whereas such an illustration will be extremely simple and based on the operating mode of each component part.

Therefore, with reference to Figures 1 through to 9 it can be noticed that the therein illustrated arrangement generates a radio frequency (RF) that is appropriately divided to a value which is approximately six times smaller than the one that is normally used in radio transmission. Such a frequency is obtained through integrated frequency dividers. The stereophonic information to be transmitted through the telephone line is input , appropriately filtered, in a multiplexor block and the radio-frequency is modulated by means of an integrated electronic commutator adapted to alternate, in the form of pulses with a duration of 13 microseconds each, the signals corresponding to the left-hand and the right-hand channels. The whole combination of various analogue channels, which are in the number of six in the above described example of embodiment, are introduced in an integrated adder, appropriately equalized and adjusted to the desired frequency by means of respective integrated operational circuits.

Starting from the integrated adders, the information is then conveyed by the telephone network, and the from time to time involved telephone exchange units, up to the destination thereof, where it is then filtered, tuned and demodulated, after which, as soon as the left-hand and right-hand channels are duly decoded and separated, the latter are amplified and sent to the places or rooms that have been planned.

At the same time, the so separated telephone line remains capable of being normally used for telephone communications with no interference at all.

The above cited places or rooms, where the transducers, ie. the loudspeakers or the audio equipment as the case may be, are installed, can be in private household, residential dwellings, offices and trading centers, shops and the like.

The variant described with particular reference to the illustrations in Figures 10 to 13 does not differ from the above explained mode of operation to any significant extent.

As far as finally the illustrations in Figures 14 to 16 are concerned, it can be noticed that the time-division multiplexed signal emitted in the above indicated manner is received in a receiver of a conventional kind to which, in this case, the decoder according to the present invention has however been added. Said decoder operated in an inverted manner with respect to the afore described signal multiplexing process. It is in fact this decoder that is given the task of reconstituting the received information into two fully separated audio channels, so that there will be obtained the same 100% separation between the laft-hand channel and the right-hand one as in the above described case.

The decoder is applied to the receivers at the output of the demodulated signal. The latter is sent to a transistor T1 which boosts the level thereof.

The integrated circuit IC1 compares the received signal which it puts in phase with the generated signal, so that the signal is restored to the exact form in which it had been emitted.

In conclusion, in the described embodiment use is made of a 19-kHz subcarrier that controls the phase and ensures that in the transmission sequence, when for instance the signal is in the right-hand channel, the left-hand channel is not present, in a manner that the missing sideband of the right-hand channel covers the spectrum of the left-hand channel, and vice-versa, such a process going then on in a sequence of intervals of 13 microseconds. At the output of the electronic commutator, therefore, there will be obtained the signal R during said 13 microseconds and the signal L during the subsequent 13 microseconds, such a commutation rate being fully unperceivable by human ears. This practically means that, in the multiplex arrangement such as the one illustrated in Figure 2, the two inputs of each channels show up 38,000 times per second each.

Such an arrangement, as it has already been mentioned, can also be applied to amplitude-modulation transmissions, which would enable a stereophinc signal to practically occupy the same space that is currently occupied by broadcasting stations transmitting in the AM spectrum. For the reception thereof, the same decoder arrangement would be used as the one described for the FM transmissions.This practically means that, adding the decoder arrangement according to the invention to a conventional receiver, the latter will be enabled to receive FM stereo, AM stereo and FM/AM monophonic transmissions as well.

In this way, one among a variety of possible embodiments of the invention has been illustrated by way of example, along with the operation mode thereof, such an illustration being integrated by the accompanying summary of the invention and the appended claims.

Claims

Arrangement for optimizing the utilization of the frequencies by means of time-division multiplexing for stereophonic broadcastings, of the type that enables two or more radio-frequency modulated channels to be broadcast either on the air or by means of any two-wire installation that may or may not carry energy, such as for instance a point-to-point telephone channel, without interfering with the related service, said arrangement comprising a transmitter circuit and a receiver circuit, characterized in that the stereophonic information means connect to time-division multiplexing coder, along with RF generator means, and frequency divider means including filter means and electronic commutator means, from which the left-hand and right-hand channel signals alternate in a sequence, wherein the respective modulator means connect to the respective mixer means that are connected to the information transmission means constituted by adder means forming a multiple transmission head unit, whereas the user is provided with his/her own receiver equipment provided with filter means, tuner means and demodulator means connected to decoder means for decoding said information which is then amplified and channelled to respective transducer means.
Arrangement according to claim 1, characterized in that said multiplexor coder means are formed by a Rf oscillator in the 456 kHz region, the circuit of which comprises filter means consisting preferably of a ceramic filter (FC), and a field-effect transistor (FET) the output of which is connected to integrated frequency divider-by-six circuit means which include a pair of divider means by at least two, by three and by four, whereas the electronic commutator means are constituted by an integrated circuit at the terminals of which there are obtained the signals corresponding to the left-hand channel and the right-hand one, whose signals have access to an integrated operational adder circuit, to the input of which a pilot signal of variable amplitude can be associated, whereas to the input og the signals corresponding to the two left-hand and right-hand channels there are connected respective frequency limiter elements limiting said frequency to 15 kHz, wherein the outputs of said elements connect to respective equalizer elements having their outputs connected to said integrated electronic commutator means.
Arrangement according to claims 1 and 2, characterized in that said equalizer elements are adjusted with an emphasis of 50 microseconds to improve the signal-to-noise ratio.
Arrangement according to claims 1 to 3, characterized in that in saidelectronic commutator means the signals corresponding to the left-hand and right-hand channels alternate at intervals of 13 microseconds.
Arrangement according to claims 1 to 4 , characterized in that said transmission head unit is formed by six analogue channels formed in succession by means of respective sound reproducer means that are respectively connected to microprocessor-based automatic sequencers of the information themes to be transmitted, from which they connect to audio precessor means which are then sent in modulated form to adder means, after which they are introduced in the telephone line, thereby reaching the access telephone exchange that is connected with peripheral exchanges from which they reach by line the user, where the telephone line is separated from the RF receiver means, said receiver means comprising low-pass filter means, tuner means from which the so obtained signals, passing through a preferably ceramic filter, are input to demodulator means and decoder means from which the left-hand and right-hand channels are then amplified.
Arrangement according to claims 1 to 5, characterized in that in said RF generator means the spectrum of frequencies usedis comprised between 100 and 450 kHz and from there, in the particular case of transmission of six channels with a multiplex stereo signal held at 15 kHz and 15 kHz with a maximum devuation of 50 kHz, the distribution thereof is in the region of 140, 190, 240, 290, 340, 390 and 450 kHz.
Arrangement according to claims 1 to 6, characterized in that said decoder circuit forming a part of the user receiver equipment comprises an integrated circuit that includes a phase-locked loop (PLL) regenerating a signal selected between a pilot signal and a own signal to obtain the separation of the two stereo channels.
Arrangement according to claims 1 to 7, characterized in that said user receiver equipment is provided with a sound reproducer element of the CD, hard or vynil disc, magnetic tape, satellite-broadcast music receiver and similar type.
Arrangement for sending and receiving information by point-to-point telephone link according to claim 1, characterized in that said information transmission means comprise a FM-baseband generating voltage-controlled oscillator that includes respective pass filters and possesses a modulator/demodulator of the carrier wave connected between the telephone line and a computer modem, from which said modulator/demodulator then further comprises receiver means.
Arrangement according to claims 1 and 9, characterized in that said transmission means that comprise an oscillator also include separator means exciting an output transistor, the collector of which is connected to a telephone-line coupling transformer.
Arrangement according to claims 1 and 9, characterized in that said receiver means include at their input respective pass filters and are tuned to the frequency of the carrier wave, said means being connected to a phase-locked oscillator the output of which is connected to the computer.
Arrangement according to claims 1 and 9, characterized in that said data transmission means have a modem connected to a FM baseband generating integrated circuit of the VCO (Voltage-Controlled Oscillator), the output of which is connected through a variable excitation adjustment capacitor to the base of a RF exciter transistor, wherein the emitter thereof is connected to ground through the biasing resistor in parallel with a capacitor, while the collector thereof is connected with the tuned load connected in series with a RF choke, said collector being in turn coupled through a capacitor with the base of a second output transistor, the emitter of which is connected with a RF output transformer connected in series with the telephone line.
Arrangement according to claims 1 and 10, characterized in that said user computers are connected to the server through respective modems.
Arrangement according to claims 1 and 9, characterized in that said receiver means include a low-pass filter on the server side and a high-pass filter on the user side, the output of which connects to an integrated circuit of the PLL (phase-locked loop) type having the output thereof connected to the user computer modem.
Decoder for an arrangement optimizing the utilization of frequencies by time-division multiplexing of stereophonic radio broadcast transmissions, characterized in that the transmitter comprises time-division multiplexing processor means in each channel starting from the audio source means , the channels of which integrate the transmission baseband by means of a subcarrier at a frequency in the 19 kHz region, with its sidebands of the left-hand and right-hand channels suppressed sequentially in an alternate manner and connected to the RF transmission means, whereas the radio receiver means include, at the output of the demodulator means, decoder means inverting the alternating sequence imposed to said left-hand and right-hand channels, the decoder means of which comprise a booster transistor for boosting the level thereof, introduced ahead of an integrated phase-comparator circuit controlled by a master oscillator and a pair of transistors conditioning an integrated commutator circuit.
Decoder according to claim 15, characterized in that said commutator IC, which is controlled by the pilot signal of the phase-comparator PLL, determines at its output that each left-hand and right-hand channel signal alternates sequentially at a rate of 13 microseconds.