CA1253920A - Process and device for the radio transmission of coded data superimposed on a traditional frequency- modulated broadcast - Google Patents
Process and device for the radio transmission of coded data superimposed on a traditional frequency- modulated broadcastInfo
- Publication number
- CA1253920A CA1253920A CA000487662A CA487662A CA1253920A CA 1253920 A CA1253920 A CA 1253920A CA 000487662 A CA000487662 A CA 000487662A CA 487662 A CA487662 A CA 487662A CA 1253920 A CA1253920 A CA 1253920A
- Authority
- CA
- Canada
- Prior art keywords
- signals
- coded
- frequency
- coded data
- modulated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
- H04H20/28—Arrangements for simultaneous broadcast of plural pieces of information
- H04H20/33—Arrangements for simultaneous broadcast of plural pieces of information by plural channels
- H04H20/34—Arrangements for simultaneous broadcast of plural pieces of information by plural channels using an out-of-band subcarrier signal
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- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
- Transmitters (AREA)
- Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
- Circuits Of Receivers In General (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE The device comprises an input unit (40) for generating coded data to be transmitted, an FSK coder-modulator (30) for modulating, by frequency shift, the coded data to be transmitted, in a frequency range located between about 15 and 18 kHz, a mixer circuit (32) for superimposing, with an attenuation of 20 to 40 dB, the signals modulated by frequency shift on a low-frequency signal of a traditional program to be applied to a frequency modulation radio transmitter (20), a decoder comprising filter circuits and an FSK de-modulator for separating the coded data from the signals delivered by a standard frequency modulation receiver, and a display or recording unit for displaying or recording the demodulated, filtered, transmitted coded data.
Description
~Z5392(3 PROCESS AND DEVICE FOR THE RADIO TRANSMISSION OF CODED
D.~TA SUPERIMPOSED 0~ A TRADITIONAL FREQUENCY-~ODUI.~TED
BROADCAST
The present invention relates to a process and a device for the radio transmission of coded data super-imposed on a traditional frequency-modulated broadcast.
The invention relates more particularly to a process for the radio transmission of coded data super-imposed on a traditional frequency-modulated broadcast wherein coded data to be transmitted are modulated in a predetermined frequency range in order to create modulated coded signals, the modu]ated coded signa]s are mixed with the low-frequency signals of a traditional program to be broadcast by a frequency modulation radio transmitter, the signals delivered by a frequency modulation receiver are filtered in order to isolate the said modulated coded signals, the filtered, modulated coded signals are demodulated and the transmitted coded data are displayed or recorded by applying the demodulated, filtered coded signals to a display or recording unit.
A variety of systems for the radio transmission of coded data are already known. In general, these systems constitute warning ~r watching devices and require the existence of transmitters and receivers specially designed for the transmission of coded data.
Furthermore, attempts have already been made to superimpose, on a conventional radio broadcast, certain signals for controlling particular functions. However, applications of this type are very specific and do not permit the reception and display, in uncoded form, of coded data which are capable of complementing the content of audio data transmitted conventionally by radio waves.
It has also been proposed to superimpose coded data on a conventional frequency-modulated radio broad-cast by adding a low-level subcarrier modulated by coded ., ~2S~92~
signals. However, the proposed systems have not as yet made it possible to obtain reliable transmi.ssions without substantially impairing the main program or the additional coded signals.
The precise aim of the present invention is to overcome the abovementioned disadvantages and to make it possible, without impairing the quality of a con-ventional frequency-modulated radio broadcast, reliably to transmit supplementary coded data which are capable.
of complementing the conventional radio broadcast.
These objects are achieved by virtue of a pro~
cess of the type defined at the start of the description, wherein the coded data to be transmitted are modulated by frequency shift in a frequency range located between about 15 and 18 kHz, wherein the coded signals modulated by frequency shift are mixed, with an attenuation of 20 to 40 dB relative to the maximum transmission level, with the said low-frequency signals of a traditional program, and wherein the ratio of the frequency devia-tion of the coded signals modulated by frequency shift, expressed in Hertz, to the rate of transmission of the coded data to be transmitted, expressed in bauds, is kept between about 85 and 120% and preferably around 100%.
Preferably, the signals modulated by frequency shift are applied downstream of the stereophonic filters of the frequency modulation transmitter in order to mix the said modulated signals with the signals of a traditional radio program.
Advantageously, the reception signals to be filtered are tapped upstream of the de-emphasis circuits of the standard frequency modulation receiver.
The demodulated filtered reception signals can be displayed on a data processing terminal, which makes it possible to control the checking of the filtering ~25392 characteristics.
According to the invention, a device ~or the radio transmission of coded data superimposed on a traditional frequency-modulated broadcast comprises an input unit for generating coded data to be transmitted, an FSK coder-modulator for modulating, by frequency shift, the coded data to be transmitted, in a frequency range located between about 15 and 18 kHz, a mixer circuit for superimposing, with an attenuation of 20 to 40 dB, the signals modulated by frequency shift on a low-frequency signal of a traditional program to be applied to a requency modulation radio transmitter, a decoder comprising filter circuits and an FSK de-modulator for separating the coded data from the signals delivered by a standard frequency modulation receiver, and a display or recording unit for displaying or re-cording the demodulated, filtered, transmitted coded data.
The display unit can be a standard television receiver or the display unit of a data processing terminsl equipped with an outlet for peripherals and, if appropriate, with an adapter circuit. A link can be provided between the said data processing terminal, displaying the transmitted coded data, and the program-mablefilters of the decoder for sending out programmable check codes.
The decoder also comprises a level adapter arranged at the input and two level-checking units arranged on either side of the filter circuits.
The device according to the invention is suitable for the transmission of coded data representing, for example, the title of a record, an advertising message or commercial information.
The coded message, which is prqferably trans-mitted repetitively with the aid of a loop broadcast, ,~ "'' :
.
~25392(1 can comprise various check characters or coded charac-ters which cannot be displayed.
Further characteristics and advantages of the invention will become apparent from the following des-cription of embodiments of the invention, with referenceto the attached drawing; in this drawing:
- Figure 1 schematically represents the .various items of equipment to be used for the broadcast part of a transmission device according to the invention, - Figure 2 schematically represents the various items of equipment to be used for the reception part of a transmission device according to the invention, - Figure 3 is the block diagram of the recep-tion part of a device according to the invention, - Figure 4 shows an embodiment of a coder-modulator circuit which can be incorporated in the broadcast part of the device according to the invention, - Figure 5 shows an example of filter and de-modulation circuits of a decoder which can be incorpora-: 20 ted in the reception part of the device according to the invention, and - Figure 6 shows a curve of the average re-cording level of a music signal as a function of the frequency.
Referring to Figure 1, this figure shows a con-ventional frequency modulation transmitter 20 equipped with an antenna 21 and intended for receiving, via a line 11, low-frequency electrical signals representing a radio program to be broadcast and originating from a microphone or from a system for reading recorded informa-tion, such as a record player turntable 10 or a tape or cassette recorder. In the absence of any other device, ~ the radio program is simply transmitted conventionally ; by the FM transmitter 20 and its antenna 21.
Accordin3 to the inveotion, before the frequencJ-' . ' `
:
~Z~;392(~
modulated broadcast, coded digital signals are super-imposed, in a mixer 32, on the program signals applied via the line 11, so that the FM transmitter then receives a mi~ture of conventional low-frequency signals and coded signals via the line 33.
The coded signals can be formed very easily from messages in uncoded form with the aid of a con-ventional data processing terminal 40 equipped with a keypad and capable of delivering, via a line 41, signals coded according to a preset code, for example in RTTY
code according to an RS 232 format. The terminal 40 can include a conventional unit for the storing and manage-ment of texts.
The coded signals can also originate directly from a memory or other recording medium. In one possible application, the coded signals can be formed from the reading of a bar code with the aid of an optical reading device. In another application, the coded signals can consist of coded signals which are non-decodable after radio transmission but which are already present in the recording medium read in the reading device 10 for the radio broadcast by the transmitter 20. In this case, the signals produced by the reading device 10 can also be applied, via the line lla, to a decoder 12 suitable for decoding coded magnetic tapes, cassettes or discs.
The signals produced by the decoder 12 via the line 41a, which comprise a coded message, can then be used to feed into the coder 30 provided for receiving the coded signals transmitted via the line 41.
The coder 30 essentially comprises a modulator 34 of the FSK type (frequency shift Keyin~) so that it can transmit, via the line 31, coded signals charac-terized by two predetermined frequency levels. According to the invention, the FSK modulator 34 is designed so that the frequency levels of the coded signals are 125392~
loca~ed between about 15 kHz and 18 kHz and so that the level of the coded signals in the line 31 is attenuated by 20 to 40 dB in order to take account of the curve of the level of the LF signals usually transmitted via the line 11 (see Figure 6). Thus, after mixing in the mixer 32 with the LF signals present in the line 11, the coded signals in the line 31 do not affect the quality of the conventional radio broadcast, nor are they suppressed by the filters of the conventional frequency modulation transmitters or receivers.
It is pointed out that, in an advantageous variant, the coded signals can be introduced directly into the FM transmitter 20, via the line 31a shown as a broken line in Figure 1, downstream of the stereo-phonic filters. In this case, the mixer 32 of Figure1 is naturally suppressed and the line 33 transmits the same signals as the line 11. The reinjection of coded signals after the stereophonic filters of the FM trans-mitter makes it possible subsequently to facilitate separation of the coded signals on reception, by virtue of the gain obtained in the frequency band of the FSK
modulated coded signals.
Figure 2 schematically represents the components of the recep~ion system of a device according to the~
invention. These components essentially comprise a standard frequency modulation receiver 120 with its antenna 121, a decoder 50 and a display unit 60, which can be a standard television receiver or a data pro-cessing terminal equipped with an inlet for peripherals.
The signals applied to the decoder 50 can be tapped from an audio outlet via a line 51 or, preferably, via a line 51a shown as a broken line in Figure 2, before the de-emphasis circuits of the receiver 120, which affords a gain of the order of 10 to 15 dB in the frequency band containing the coded signals.
. ''" . .
. . :
.
.
' ;
~Z539;~i The coded signals, which, in the decoder 50, are separated from the conventional radio message, are applied to the display unit 60 via a line 52 and can then appear in uncoded form on the screenA At the same time, the listener can listen to the usual radio program. Of course, the decoder 50 can be integrated into the housing of the FM receiver 120 if required.
Furthermore, in the case where the display unit 60 con-sists of a data processing terminal, it is also possible to send coded check signals to the decoder 50 via the line 53 from the terminal 60 in order to be able to adapt to different reception circumstances a~d to con-trol, for example, the programming of the quality factcr or of the central frequency of the filter con-tained in the decoder.
A recording unit consisting of a memory, for example, can be substituted for or associated with the display unit 60 for recording the coded signals produced by the demodulator 50.
Figure 3 shows the components forming the de-coder 50. A level adapter 55 receives, via an input capacitor 54, the complex signals delivered via the lines 51 or 51a by the FM receiver 120, as indicated previously. The output of the level adapter 55 is con-nected to filter circuits 56, which are preferably program~able capacitor switched bandpass filters, associated with a clock 57. The filters can be programmed permanently with the aid of keys, but the programming can also be adapted by the user if the unit 60 consists of a data processing terminal.
Level-checking components 63, 64 are arranged respectively before and after the filter circuits 56.
A phase loop FSK demodulator 58 is placed at the output of the filters 56, and error correction circuits 59, sensitive to coded error correction signals, can be ~Z539Z~
placed at the output of the FSK demodulator 58 i~
required. Adapters 61, 62, which depend on the type of display unit 60, are inserted between the output of the decoder 50 and the lines 52a, 52 respectively, which are provided for connection to two display units 60 of different types.
Figure 4 shows a particular example of an FSK
modulator which can be incorporated in the coder 30 of Figure 1. This modulator 34 is constructed around a standard base circuit, for example the XR2206 circuit from the Company EX~R, and has characteristics which can be adapted with the aid of external resistors and capacitors. The coded signals are applied to the input 35 and the sinusoidal FSK modulated output signals are available at an output 36. Square-wave output signals are available for checking purposes at an output 37.
As can be seen in Figure 4, the FSK modulator 34 can comprise a base circuit with current interrupters, 131, a voltaae controlled oscillator circuit (VC0) 132 and a multiplier circuit 133 which also converts the signals to sinusoidal form. The external components can then comprise resistors or potentiometers 141 to 144 and a frequency-regulating capacitor 145, resistors or poten-tiometers 151 to 153 and a capacitor 154 for regulating the output signal level, and resistors or potentiometers 161, 162 for adjusting the shape and symmetry of the sinusoidal output signal with the aim of obtaining minimum distortion.
To have a good signal-to-noise ratio and to reduce intermodulation, it is desirable for the ratio of the frequency deviation of the signals modulated by frequency shift, expressed in Hertz, to the rate of transmission of the coded data to be transmitted, ex-pressed in bauds, to be between about 85 and 120% and preferably around 100%. Thus, with a transmission rate ~5392~3 g of 300 bauds, it is desirable for the frequency shift caused by the FSK modulator to be, for exampl~, +150 Hz.
Figure 5 shows, in greater detail, an embodi-ment of a decoder-demodulator circuit 50 with a clock 57 comprising a frequency reference component 70, connected in parallel with a capacitor 71, and reversing logic gates 73, 74, 75 associated with resistors 7J, 79, capacitors 72, 78 and an output circuit 76 consis-ting of a frequency divider (dividing by 9 for example), which makes it possible for example to deliver clock pulses of the order of 1 MHz at a frequency of 8 MHz divided by 9.
The filter circuit system 56 comprises first and second switched capacitor filters 56a, 56b, which can consist, for example, of the R562~
circuits from the Company RETICON. The characteristics of the programmable filters 56a, 56b can be determined by interrupters, as shown in Figure 5, or by control signals produced by the terminal 60, as indicated pre-viously. The filters 56a, 56b can be of the bandpass or high-pass type.
The demodulator 58 shown in Figure 5 is of a conventional configuration with an input preamplifier 81, a voltage controlled oscillator circuit (~7CO) ~0, a t~hase detector 82 and a quadrature detector 83, a locking detection filter 84, loop and data filters 85, 86, a comparator for detecting a locking condition, 88, an internal reference circuit 89 and an FSK comparator 87 delivering output signals corresponding to the de-modulated, transmitted coded signals.
It is desirable if the coded data to be trans-mitted are transmitted according to a repetition loop.
Furthermore, the transmitted coded message will advantageously comprise check characters including an image clearing code, placed before each phase of the ~L2~
message, as well as an end-of-message signaling code.
In one possible application, the transmitted coded message comprises coded characters which cannot be displayed and the transmitted coded characters which S cannot be displayed are recorded by applying the de-modulated filtered signals to a memory unit. This can contribute for example to facilitating the measurement of the ratings of radio stations identified by a par-ticular code.
The invention is particularly suitable for the use of the decoder-demodulator in combination with a personal data processing terminal such as, for example, the one known as ALCATEL 250. In this case, it is desirable for the check characters to include a charac-ter which ensures that the personal terminal is in the scroll mode.
D.~TA SUPERIMPOSED 0~ A TRADITIONAL FREQUENCY-~ODUI.~TED
BROADCAST
The present invention relates to a process and a device for the radio transmission of coded data super-imposed on a traditional frequency-modulated broadcast.
The invention relates more particularly to a process for the radio transmission of coded data super-imposed on a traditional frequency-modulated broadcast wherein coded data to be transmitted are modulated in a predetermined frequency range in order to create modulated coded signals, the modu]ated coded signa]s are mixed with the low-frequency signals of a traditional program to be broadcast by a frequency modulation radio transmitter, the signals delivered by a frequency modulation receiver are filtered in order to isolate the said modulated coded signals, the filtered, modulated coded signals are demodulated and the transmitted coded data are displayed or recorded by applying the demodulated, filtered coded signals to a display or recording unit.
A variety of systems for the radio transmission of coded data are already known. In general, these systems constitute warning ~r watching devices and require the existence of transmitters and receivers specially designed for the transmission of coded data.
Furthermore, attempts have already been made to superimpose, on a conventional radio broadcast, certain signals for controlling particular functions. However, applications of this type are very specific and do not permit the reception and display, in uncoded form, of coded data which are capable of complementing the content of audio data transmitted conventionally by radio waves.
It has also been proposed to superimpose coded data on a conventional frequency-modulated radio broad-cast by adding a low-level subcarrier modulated by coded ., ~2S~92~
signals. However, the proposed systems have not as yet made it possible to obtain reliable transmi.ssions without substantially impairing the main program or the additional coded signals.
The precise aim of the present invention is to overcome the abovementioned disadvantages and to make it possible, without impairing the quality of a con-ventional frequency-modulated radio broadcast, reliably to transmit supplementary coded data which are capable.
of complementing the conventional radio broadcast.
These objects are achieved by virtue of a pro~
cess of the type defined at the start of the description, wherein the coded data to be transmitted are modulated by frequency shift in a frequency range located between about 15 and 18 kHz, wherein the coded signals modulated by frequency shift are mixed, with an attenuation of 20 to 40 dB relative to the maximum transmission level, with the said low-frequency signals of a traditional program, and wherein the ratio of the frequency devia-tion of the coded signals modulated by frequency shift, expressed in Hertz, to the rate of transmission of the coded data to be transmitted, expressed in bauds, is kept between about 85 and 120% and preferably around 100%.
Preferably, the signals modulated by frequency shift are applied downstream of the stereophonic filters of the frequency modulation transmitter in order to mix the said modulated signals with the signals of a traditional radio program.
Advantageously, the reception signals to be filtered are tapped upstream of the de-emphasis circuits of the standard frequency modulation receiver.
The demodulated filtered reception signals can be displayed on a data processing terminal, which makes it possible to control the checking of the filtering ~25392 characteristics.
According to the invention, a device ~or the radio transmission of coded data superimposed on a traditional frequency-modulated broadcast comprises an input unit for generating coded data to be transmitted, an FSK coder-modulator for modulating, by frequency shift, the coded data to be transmitted, in a frequency range located between about 15 and 18 kHz, a mixer circuit for superimposing, with an attenuation of 20 to 40 dB, the signals modulated by frequency shift on a low-frequency signal of a traditional program to be applied to a requency modulation radio transmitter, a decoder comprising filter circuits and an FSK de-modulator for separating the coded data from the signals delivered by a standard frequency modulation receiver, and a display or recording unit for displaying or re-cording the demodulated, filtered, transmitted coded data.
The display unit can be a standard television receiver or the display unit of a data processing terminsl equipped with an outlet for peripherals and, if appropriate, with an adapter circuit. A link can be provided between the said data processing terminal, displaying the transmitted coded data, and the program-mablefilters of the decoder for sending out programmable check codes.
The decoder also comprises a level adapter arranged at the input and two level-checking units arranged on either side of the filter circuits.
The device according to the invention is suitable for the transmission of coded data representing, for example, the title of a record, an advertising message or commercial information.
The coded message, which is prqferably trans-mitted repetitively with the aid of a loop broadcast, ,~ "'' :
.
~25392(1 can comprise various check characters or coded charac-ters which cannot be displayed.
Further characteristics and advantages of the invention will become apparent from the following des-cription of embodiments of the invention, with referenceto the attached drawing; in this drawing:
- Figure 1 schematically represents the .various items of equipment to be used for the broadcast part of a transmission device according to the invention, - Figure 2 schematically represents the various items of equipment to be used for the reception part of a transmission device according to the invention, - Figure 3 is the block diagram of the recep-tion part of a device according to the invention, - Figure 4 shows an embodiment of a coder-modulator circuit which can be incorporated in the broadcast part of the device according to the invention, - Figure 5 shows an example of filter and de-modulation circuits of a decoder which can be incorpora-: 20 ted in the reception part of the device according to the invention, and - Figure 6 shows a curve of the average re-cording level of a music signal as a function of the frequency.
Referring to Figure 1, this figure shows a con-ventional frequency modulation transmitter 20 equipped with an antenna 21 and intended for receiving, via a line 11, low-frequency electrical signals representing a radio program to be broadcast and originating from a microphone or from a system for reading recorded informa-tion, such as a record player turntable 10 or a tape or cassette recorder. In the absence of any other device, ~ the radio program is simply transmitted conventionally ; by the FM transmitter 20 and its antenna 21.
Accordin3 to the inveotion, before the frequencJ-' . ' `
:
~Z~;392(~
modulated broadcast, coded digital signals are super-imposed, in a mixer 32, on the program signals applied via the line 11, so that the FM transmitter then receives a mi~ture of conventional low-frequency signals and coded signals via the line 33.
The coded signals can be formed very easily from messages in uncoded form with the aid of a con-ventional data processing terminal 40 equipped with a keypad and capable of delivering, via a line 41, signals coded according to a preset code, for example in RTTY
code according to an RS 232 format. The terminal 40 can include a conventional unit for the storing and manage-ment of texts.
The coded signals can also originate directly from a memory or other recording medium. In one possible application, the coded signals can be formed from the reading of a bar code with the aid of an optical reading device. In another application, the coded signals can consist of coded signals which are non-decodable after radio transmission but which are already present in the recording medium read in the reading device 10 for the radio broadcast by the transmitter 20. In this case, the signals produced by the reading device 10 can also be applied, via the line lla, to a decoder 12 suitable for decoding coded magnetic tapes, cassettes or discs.
The signals produced by the decoder 12 via the line 41a, which comprise a coded message, can then be used to feed into the coder 30 provided for receiving the coded signals transmitted via the line 41.
The coder 30 essentially comprises a modulator 34 of the FSK type (frequency shift Keyin~) so that it can transmit, via the line 31, coded signals charac-terized by two predetermined frequency levels. According to the invention, the FSK modulator 34 is designed so that the frequency levels of the coded signals are 125392~
loca~ed between about 15 kHz and 18 kHz and so that the level of the coded signals in the line 31 is attenuated by 20 to 40 dB in order to take account of the curve of the level of the LF signals usually transmitted via the line 11 (see Figure 6). Thus, after mixing in the mixer 32 with the LF signals present in the line 11, the coded signals in the line 31 do not affect the quality of the conventional radio broadcast, nor are they suppressed by the filters of the conventional frequency modulation transmitters or receivers.
It is pointed out that, in an advantageous variant, the coded signals can be introduced directly into the FM transmitter 20, via the line 31a shown as a broken line in Figure 1, downstream of the stereo-phonic filters. In this case, the mixer 32 of Figure1 is naturally suppressed and the line 33 transmits the same signals as the line 11. The reinjection of coded signals after the stereophonic filters of the FM trans-mitter makes it possible subsequently to facilitate separation of the coded signals on reception, by virtue of the gain obtained in the frequency band of the FSK
modulated coded signals.
Figure 2 schematically represents the components of the recep~ion system of a device according to the~
invention. These components essentially comprise a standard frequency modulation receiver 120 with its antenna 121, a decoder 50 and a display unit 60, which can be a standard television receiver or a data pro-cessing terminal equipped with an inlet for peripherals.
The signals applied to the decoder 50 can be tapped from an audio outlet via a line 51 or, preferably, via a line 51a shown as a broken line in Figure 2, before the de-emphasis circuits of the receiver 120, which affords a gain of the order of 10 to 15 dB in the frequency band containing the coded signals.
. ''" . .
. . :
.
.
' ;
~Z539;~i The coded signals, which, in the decoder 50, are separated from the conventional radio message, are applied to the display unit 60 via a line 52 and can then appear in uncoded form on the screenA At the same time, the listener can listen to the usual radio program. Of course, the decoder 50 can be integrated into the housing of the FM receiver 120 if required.
Furthermore, in the case where the display unit 60 con-sists of a data processing terminal, it is also possible to send coded check signals to the decoder 50 via the line 53 from the terminal 60 in order to be able to adapt to different reception circumstances a~d to con-trol, for example, the programming of the quality factcr or of the central frequency of the filter con-tained in the decoder.
A recording unit consisting of a memory, for example, can be substituted for or associated with the display unit 60 for recording the coded signals produced by the demodulator 50.
Figure 3 shows the components forming the de-coder 50. A level adapter 55 receives, via an input capacitor 54, the complex signals delivered via the lines 51 or 51a by the FM receiver 120, as indicated previously. The output of the level adapter 55 is con-nected to filter circuits 56, which are preferably program~able capacitor switched bandpass filters, associated with a clock 57. The filters can be programmed permanently with the aid of keys, but the programming can also be adapted by the user if the unit 60 consists of a data processing terminal.
Level-checking components 63, 64 are arranged respectively before and after the filter circuits 56.
A phase loop FSK demodulator 58 is placed at the output of the filters 56, and error correction circuits 59, sensitive to coded error correction signals, can be ~Z539Z~
placed at the output of the FSK demodulator 58 i~
required. Adapters 61, 62, which depend on the type of display unit 60, are inserted between the output of the decoder 50 and the lines 52a, 52 respectively, which are provided for connection to two display units 60 of different types.
Figure 4 shows a particular example of an FSK
modulator which can be incorporated in the coder 30 of Figure 1. This modulator 34 is constructed around a standard base circuit, for example the XR2206 circuit from the Company EX~R, and has characteristics which can be adapted with the aid of external resistors and capacitors. The coded signals are applied to the input 35 and the sinusoidal FSK modulated output signals are available at an output 36. Square-wave output signals are available for checking purposes at an output 37.
As can be seen in Figure 4, the FSK modulator 34 can comprise a base circuit with current interrupters, 131, a voltaae controlled oscillator circuit (VC0) 132 and a multiplier circuit 133 which also converts the signals to sinusoidal form. The external components can then comprise resistors or potentiometers 141 to 144 and a frequency-regulating capacitor 145, resistors or poten-tiometers 151 to 153 and a capacitor 154 for regulating the output signal level, and resistors or potentiometers 161, 162 for adjusting the shape and symmetry of the sinusoidal output signal with the aim of obtaining minimum distortion.
To have a good signal-to-noise ratio and to reduce intermodulation, it is desirable for the ratio of the frequency deviation of the signals modulated by frequency shift, expressed in Hertz, to the rate of transmission of the coded data to be transmitted, ex-pressed in bauds, to be between about 85 and 120% and preferably around 100%. Thus, with a transmission rate ~5392~3 g of 300 bauds, it is desirable for the frequency shift caused by the FSK modulator to be, for exampl~, +150 Hz.
Figure 5 shows, in greater detail, an embodi-ment of a decoder-demodulator circuit 50 with a clock 57 comprising a frequency reference component 70, connected in parallel with a capacitor 71, and reversing logic gates 73, 74, 75 associated with resistors 7J, 79, capacitors 72, 78 and an output circuit 76 consis-ting of a frequency divider (dividing by 9 for example), which makes it possible for example to deliver clock pulses of the order of 1 MHz at a frequency of 8 MHz divided by 9.
The filter circuit system 56 comprises first and second switched capacitor filters 56a, 56b, which can consist, for example, of the R562~
circuits from the Company RETICON. The characteristics of the programmable filters 56a, 56b can be determined by interrupters, as shown in Figure 5, or by control signals produced by the terminal 60, as indicated pre-viously. The filters 56a, 56b can be of the bandpass or high-pass type.
The demodulator 58 shown in Figure 5 is of a conventional configuration with an input preamplifier 81, a voltage controlled oscillator circuit (~7CO) ~0, a t~hase detector 82 and a quadrature detector 83, a locking detection filter 84, loop and data filters 85, 86, a comparator for detecting a locking condition, 88, an internal reference circuit 89 and an FSK comparator 87 delivering output signals corresponding to the de-modulated, transmitted coded signals.
It is desirable if the coded data to be trans-mitted are transmitted according to a repetition loop.
Furthermore, the transmitted coded message will advantageously comprise check characters including an image clearing code, placed before each phase of the ~L2~
message, as well as an end-of-message signaling code.
In one possible application, the transmitted coded message comprises coded characters which cannot be displayed and the transmitted coded characters which S cannot be displayed are recorded by applying the de-modulated filtered signals to a memory unit. This can contribute for example to facilitating the measurement of the ratings of radio stations identified by a par-ticular code.
The invention is particularly suitable for the use of the decoder-demodulator in combination with a personal data processing terminal such as, for example, the one known as ALCATEL 250. In this case, it is desirable for the check characters to include a charac-ter which ensures that the personal terminal is in the scroll mode.
Claims (13)
1. A process for the radio transmission of coded data superimposed on a traditional frequency-modulated broad-cast, in which process coded data to be transmitted are modulated in a predetermined frequency range in order to create modulated coded signals, the modulated coded signals are mixed with the low-frequency signals of a traditional program to be broadcast by a frequency modulation radio transmitter, the signals delivered by a frequency modulation receiver are filtered in order to isolate the said modulated coded signals, the filtered, modulated coded signals are demodulated and the trans-mitted coded data are displayed or recorded by applying the demodulated, filtered coded signals to a display or recording unit, wherein the coded data to be transmitted are modulated by frequency shift in a frequency range located between about 15 and 18 kHz, wherein the coded signals modulated by frequency shift are mixed, with an attenuation of 20 to 40 dB relative to the maximum transmission level, with the said low-frequency signals of a traditional program, and wherein the ratio of the frequency deviation of the coded signals modulated by frequency shift, expressed in Hertz, to the rate of transmission of the coded data to be transmitted, ex-pressed in bauds, is kept between about 85 and 120% and preferably around 100%.
2. The process as claimed in claim 1, wherein the sig-nals modulated by frequency shift are applied downstream of the stereophonic filters of the frequency modulation transmitter in order to mix the said modulated signals with the signals of a traditional radio program.
3. The process as claimed in claim 2, wherein the reception signals to be filtered are tapped upstream of the de-emphasis circuits of the standard frequency modulation receiver.
4. The process as claimed in claim 1, wherein the demodulated filtered reception signals are displayed on a data processing terminal, which makes it possible to control the checking of the characteristics of the said filtering.
5. The process as claimed in claim 1, wherein the coded data to be transmitted are transmitted according to a repetition loop.
6. The process as claimed in claim 1, wherein the transmitted coded data are displayed by applying the demodulated filtered signals to a display unit of a data processing terminal or of a television receiver, and wherein the transmitted coded message comprises check characters including an image clearing code placed before each phase of the message.
7. The process as claimed in claim 1, wherein the transmitted coded message comprises coded characters which cannot be displayed, and wherein the coded charac-ters which cannot be displayed are recorded by applying the demodulated filtered signals to a memory unit.
8. A device for the radio transmission of coded data superimposed on a traditional frequency-modulated broad-cast, which comprises an input unit (40) for generating coded data to be transmitted, an FSK coder-modulator (30) for modulating, by frequency shift, the coded data to be transmitted, in a frequency range located between about 15 and 18 kHz, a mixer circuit (32) for super-imposing, with an attenuation of 20 to 40 dB, the signals modulated by frequency shift on a low-frequency signal of a traditional program to be applied to a frequency modulation radio transmitter (20), a decoder (50) com-prising filter circuits (56) and an FSK demodulator (58) for separating the coded data from the signals delivered by a standard frequency modulation receiver (120), and a display or recording unit (60) for displaying or recording the demodulated, filtered, transmitted coded data.
9, The device as claimed in claim 8, wherein the said mixer circuit (32) is located downstream of the stereo-phonic filters of the frequency modulation transmitter (20).
10. The device as claimed in claim 9, wherein the signals applied to the decoder (50) are tapped upstream of the de-emphasis circuits of the standard frequency modulation receiver (120).
11. The device as claimed in claim 8, wherein the filter circuits (56) comprise programmable switched capacitor bandpass filters, associated with a clock (57), wherein the display unit (60) is a data processing terminal, and wherein a link (53) is provided between the said data processing terminal (60), displaying the transmitted coded data, and the program-mable filters (56) of the decoder (50) for sending out programmable check codes.
12. The device as claimed in claim 8, wherein the decoder (50) also comprises a level adapter (55) arranged at the input and two level-checking units (63, 64) arranged on either side of the filter circuits.
13. The device as claimed in claim 8, wherein the frequency shift of the coder-modulator (30) is of the order of 300 Hz for a rate of transmission of coded data of the order of 300 bauds.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8412092 | 1984-07-30 | ||
| FR8412092A FR2568432B1 (en) | 1984-07-30 | 1984-07-30 | METHOD AND DEVICE FOR TRANSMITTING CODED INFORMATION OVER THE WIRE OVERLAY ON A TRADITIONAL FREQUENCY MODULATED TRANSMISSION |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1253920A true CA1253920A (en) | 1989-05-09 |
Family
ID=9306637
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000487662A Expired CA1253920A (en) | 1984-07-30 | 1985-07-29 | Process and device for the radio transmission of coded data superimposed on a traditional frequency- modulated broadcast |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0172095B1 (en) |
| JP (1) | JPS6199446A (en) |
| AT (1) | ATE64048T1 (en) |
| CA (1) | CA1253920A (en) |
| DE (1) | DE3582979D1 (en) |
| FR (1) | FR2568432B1 (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3512297C2 (en) * | 1985-04-04 | 1994-03-10 | Grundig Emv | Device for receiving additional information in radio broadcasting |
| FR2619662A1 (en) * | 1987-08-19 | 1989-02-24 | Bernard Alain | Method of transmitting information relating to racing and receiver for implementing this method |
| WO1989007374A1 (en) * | 1988-02-08 | 1989-08-10 | Robert John Suffern | Apparatus for transmitting information |
| FR2630604A1 (en) * | 1988-04-22 | 1989-10-27 | Marinier Denis | METHOD AND APPARATUS FOR COMMUNICATION BY INTEGRATED SUBCARKERS IN AN ANALOG OR DIGITAL SIGNAL |
| EP0423381B1 (en) * | 1989-10-16 | 1994-12-14 | MPS Media Presse Service GmbH & Co. KG | Apparatus for transmitting audio and/or digital information |
| ES2048043B1 (en) * | 1991-08-14 | 1995-12-16 | Baranoff Rossine Dimitri | PROCESS AND DEVICE FOR RADIO TRANSMISSION OF CODED DATA OVERLAYED ON A TRADITIONAL BROADCAST OF MODULATED FREQUENCY |
| GR910100504A (en) * | 1991-12-18 | 1993-08-31 | Baranoff Rossine Dimitri | Method and arrangement for the transmission of coded data |
| DE4142332A1 (en) * | 1991-12-20 | 1993-07-01 | Bosch Siemens Hausgeraete | BROADCAST RECEIVER FOR INTENDED RECEPTION OF RADIO RADIO PROGRAMS |
| US5630203A (en) * | 1993-01-12 | 1997-05-13 | Weinblatt; Lee S. | Technique for surveying a radio or a television audience |
| KR0123755B1 (en) * | 1993-08-19 | 1997-12-01 | 김광호 | Voice signal transceiver system |
| GB9700854D0 (en) | 1997-01-16 | 1997-03-05 | Scient Generics Ltd | Sub-audible acoustic data transmission mechanism |
| GB9917985D0 (en) | 1999-07-30 | 1999-09-29 | Scient Generics Ltd | Acoustic communication system |
| US7796978B2 (en) | 2000-11-30 | 2010-09-14 | Intrasonics S.A.R.L. | Communication system for receiving and transmitting data using an acoustic data channel |
| AU2211102A (en) | 2000-11-30 | 2002-06-11 | Scient Generics Ltd | Acoustic communication system |
| AU2002363907A1 (en) | 2001-12-24 | 2003-07-30 | Scientific Generics Limited | Captioning system |
| GB2460306B (en) | 2008-05-29 | 2013-02-13 | Intrasonics Sarl | Data embedding system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3269126D1 (en) * | 1981-06-02 | 1986-03-27 | Texas Instruments Inc | Integrated circuit fsk modem |
-
1984
- 1984-07-30 FR FR8412092A patent/FR2568432B1/en not_active Expired - Lifetime
-
1985
- 1985-07-27 JP JP60166615A patent/JPS6199446A/en active Pending
- 1985-07-29 EP EP85401547A patent/EP0172095B1/en not_active Expired - Lifetime
- 1985-07-29 CA CA000487662A patent/CA1253920A/en not_active Expired
- 1985-07-29 AT AT85401547T patent/ATE64048T1/en not_active IP Right Cessation
- 1985-07-29 DE DE8585401547T patent/DE3582979D1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| FR2568432A1 (en) | 1986-01-31 |
| ATE64048T1 (en) | 1991-06-15 |
| FR2568432B1 (en) | 1990-06-29 |
| EP0172095A1 (en) | 1986-02-19 |
| JPS6199446A (en) | 1986-05-17 |
| DE3582979D1 (en) | 1991-07-04 |
| EP0172095B1 (en) | 1991-05-29 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20060509 |