SK174797A3 - Modulation method and circuit arrangement for the transmission of data signals - Google Patents

Abstract

The data source (for long-wave single-sideband transmission of the RDS signal (SSB-RDS))is an RDS coder capable of QDSB modulation with or without the carrier frequency. The RDS-SSB signal with vestigial carrier is produced by the filter method and converted to the transmission frequency by mixing. The road traffic information carrier which can be fed into the RDS coder can thus be used as the vestigial carrier. A known all-band receiver with synchronous demodulator is used for receiving the SSB-RDS signal. Further processing of the RDS baseband (biphase signal) is a straightforward matter.

Description

Technical field

The invention relates to a method for modulating and arranging data signal transmission circuits and a receiver for receiving modulated and transmitted data signals according to the method.

BACKGROUND OF THE INVENTION

For example, modulation with two sidebands is generally known. As a subcarrier method, dual sideband modulation is again in different areas of the communication channels, such as a stereo broadcast signal, an RSD signal for transmitting additional program-related information in a UKW radio broadcast, and color information for television transmission. WO 85/05748 also discloses the use of PSK sub-carrier modulation for compatible data transmission by AM radio transmission.

These two sideband modulations have been specially integrated into the notification channels in which signal bandwidth plays a minor role.

For example, the carrier required to demodulate DSB modulation is generated in stereo transmission in which a pilot frequency of 19 kHz is transmitted together to generate a 38 kHz carrier in the multiplex FM signal. Other methods use a Costas loop to recover a carrier DSB with identical side bands. As an example, let us mention the RDS demodulator chip - SAA6579T.

In our case, however, certain limits are set for the desired transmission of RDS signals (QDSB with two identical sidebands) in the long wave region with respect to bandwidth (RDS QDSB = 4.8 kHz).

The emission of RSD QDSB with this bandwidth in the long and kilometer range (9 ... 148.5 kHz) would lead to interference of neighboring channels of already coordinated data transmitters.

In view of this and the associated disadvantages of DSB broadcasting as

1. Double RF signal bandwidth

2. Distribution of transmitted energy into equal parts into sidebands, with only one required

3. The double selection bandwidth for the necessary receivers increases the likelihood of interference signals.

A general problem with the transmission of radio signals of an analogue or digital type is the necessary bandwidth of the modulation product. This means that efforts must be made internationally and / or nationally to ensure that the natural source of the frequency band needed for messages is optimally used.

In order to reduce the bandwidth, a single sideband (SSB) method for QAM or PSK modulated digital signals has become known, for example from WO 85/04541. It is based on the fact that in modulation with two sidebands, based on a fictitious carrier RF, two sidebands with the same information content arise. However, only one sideband is required to recover the content of the information, which in this known method requires special circuits to decode the received signal.

It is therefore an object of the present invention to provide a method and arrangement of circuits for transmitting data signals over a broad coverage transmitter, while avoiding these disadvantages. The method according to the invention, the circuit arrangement according to the invention and the receiver according to the invention are to be implemented quickly and inexpensively, do not need the development of any new chips and allow immediate use in terminal devices.

SUMMARY OF THE INVENTION

This problem is solved by transmitting RDS modulation (SSB-RDS) with a single sideband by the features of claim 1 or claim 6 for circuit arrangement.

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Further features are characterized in the corresponding feature of claims 2 to 5.

An advantage in the solution according to the invention is, inter alia, that analog modulation with one sideband SSB can also be transferred to digital modulation with two sidebands (DSB = 2PSK). A typical representative of the use of dual sideband modulation (DSB), more precisely quadrature dual sideband modulation (QDSB), is the RDS signal of Fig. 1.

By using, for example, a filtering method, the lower or upper sideband of the RDS signal can optionally be created. The single sideband digital modulation thus obtained can be transported to the desired broadcast spectrum by mixing with the appropriate oscillator frequency, as shown in FIG.

The transmission of the sideband with or without the remainder of the carrier depends on the demodulation method used. Both variants are acceptable, see Fig. 1. As a result, only half of the bandwidth of the RDS-DSB broadcast (QDSB) is provided. In addition, the efficiency of the transmitting equipment is improved and thus energy and operating costs can be reduced with the same coverage range. Reducing the bandwidth allows a smaller selection bandwidth on the receiving side and thus reduces the likelihood of interfering signals. A preferred receiver is characterized in the patent claims 7 to 9.

BRIEF DESCRIPTION OF THE DRAWINGS

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG.

2 of a wiring diagram for implementing the method of FIG. 3, a basic wiring diagram of the receiver.

DETAILED DESCRIPTION OF THE INVENTION

The following abbreviations are used in the description and figures:

ARI radio information for car drivers

RDS radio data system

SSB single side band

DSB double side bands

QDSB quadrature modulation with two sidebands

USB upper side band

LSD lower side band

PSK phase shift keing

ZF intermediate frequency.

The indicated difficulty in radiating the RDS signal over long waves is overcome in such a way that the known SSB methods known from analogue transmission techniques are transmitted on RDS QDSB modulation. Unlike analog SSB modulation, demodulation requires frequency correct and phase correct carriers.

1 shows an RDS signal with its side bands. Wherein the intermittent carrying _of Q = 57 kHz modulating said unmodulated carrier refers CAI, a known system of ARI. This is in the quadrature of the RDS phase and can thus be used to demodulate the RDS QDSB sideband.

The preparation of the RDS QDSB signal for use on long waves is shown in Fig. 2. As a RDS QDSB signal carrier with a carrier (unmodulated ARI), any RDS encoder known from UKW-RDS can generally be used.

A filtering method is used here to form the upper sideband (USB) with a carrier, intermittently framed in FIG. That is, in a second step, the RDS QDSB signal (57 kHz) is converted to the filter bandwidth (Qq j) ^{+ =} 2.4 kHZ) of the SSB filter.

The lower (LSB + carrier) or upper (USB + carrier) sideband in the ZF position is thus available at the filter output, depending on the selected frequency of the first frequency converter oscillator. The second frequency conversion serves to transplant the obtained SSB signal with the remainder of the carrier (carrier reduced to maximum sideband amplitude) to the desired transmit frequency. In the next step, the signal is amplified to the corresponding transmit power. How the SSB signal of synchronous demodulation is quadrature to sideband, of which to generate a sideband data stream, including generating (filtering method, phase method, possibly synthetic generation) has no meaning. The use for more valuable modulation methods that need to be converted back to DSB cannot be excluded. The use of the method is not tied to a long wine band.

The following describes the demodulation of SSB-RDS broadcasts.

In general, synchronous demodulation (coherent demodulator with frequency and phase correct subcarrier) is possible, but also asynchronous (without subcarrier). When using one kind of necessary carrier rest, which is in the carry side with each other. Demodulation is carried out via synchronous demodulators, with the transferred carrier remainder being used for synchronous demodulation. Thus, demodulation is performed directly to baseband. In the case of asynchronous demodulation, care must be taken on the receiving side to ensure that the carrier side absent reference is provided by the demodulator. Further, it is possible to analyze the demodulation of a signal according to the digital 0 or 1 by the existence of its typical spectral frequency components, and by demodulating asynchronously demodulations by analyzing the spectral frequency components of the modulation product. This means that for demodulation, we do not have to bind to the chips that need to be developed, since the demodulation product is in any case immediately further processed by means of commercially available digital circuits.

Single sideband RDS (SSB-RDS) transmission was tested on long waves at a frequency of 123.7 kHz, and the circuit described in Fig. 2 below has proved technically feasible and advantageous. In such a case, the RDS encoder 2 is used as the data source, which may provide QDSB modulation with or without carrier frequency. After the first frequency conversion with the first mixer 3 and the first oscillator 4, an RDS-SSB signal is generated with the rest of the carrier by the filtering method at 5, and mixing by the second mixer 6, to which the carrier is supplied from the second oscillator 7. and 8. amplified and broadcast. Thus, a carrier ARI pluggable at an RDS encoder can be used as the remainder of the carrier. A known full-band receiver with a synchronous demodulator is used to receive the SSB-RDS signal.

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Further processing of the baseband RDS (biphasic signal) will not cause any technical problems. The use of the method is not tied to the long wine zone.

Fig. 3 shows a receiver for data signals transmitted by the method of the invention. From the antenna 13, the high frequency signals are applied to the input amplifier 14. The frequency f _e + 1 ff is generated by the oscillator 15, where f _e is the frequency (remainder) of the carrier contained in the high frequency signal and ff = 57 kHz. In the mixing stage 16, the amplified radio frequency signal is then transmitted to the ZF band and passed through a band filter 17 with a bandwidth of 2.4 kHz. It is connected to the RDS demodulator type SAA6579T, which is normally available in the shop, and which has one output 19, 20 for clock signal and data signal. These signals may be decoded according to the rules established in the radio data system and then indicated.

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Claims (6)

The patented claims are removed from the modulated method A modulation method for transmitting data signals, wherein the first carrier is modulated by the data signals according to a quadrature two sideband method, wherein the signal is filtered or. a single-band phase signal with the remainder of the carrier, and wherein the single-band signal by mixing with the oscillator frequency is transferred to the long waveband and the converted single-band signal including the converted carrier is emitted. A modulation method for transmitting data signals, wherein a synthesized generation of a single-band signal with a carrier rest is modulated by the data signals in a two-sideband manner, and wherein the single-band signal is mixed into the long wave band by mixing with oscillator frequency and converted single-band signal including carrier is radiated. Modulation method according to claim 1, characterized in that the modulated signal is obtained by means of a radio data signal encoder. Modulation method according to either of claims 1 or 3, characterized in that the single-band signal is optionally generated by means of a filter as a lower or upper side band of the modulated signal. Arrangement of circuits for transmitting data signals, wherein the data signals are fed to an RDS encoder (2), wherein the output of the RDS encoder (2) is connected to a frequency converter (3, 4) which is connected at its output to a single band filter (5) an SSB, the output of which is coupled to another frequency converter (6, 7) for converting into a long wave band, and wherein the output of the other frequency converter (6, 7) is coupled to a 6. Receiver for receiving data signals while being data signals transmitted and received as modulation of a single-band signal with the remainder of the carrier being transmitted to the long-wave band by mixing with the oscillator frequency and considering means (15, 15) and converting the signal received in the long-band to the frequency position of the single-band signal with the remainder of the carrier to which the bandpass filter (17) is connected and that the bandpass filter (17) is connected with a demodulator (18). input of longwave transmitter (8). The receiver of claim 6, wherein the bandpass filter (17) has a bandwidth of 2.4 at a frequency of 57 kHz. is by kHz and includes A receiver according to any of the features characterized by the RDS demodulator known per se. of claim 6 or 7, that the demodulator (18) is a A receiver for receiving data signals, wherein the data signals are transmitted and received as a modulation of a single-band signal with a carrier carrier, which is transmitted for transmission to the long wave band by mixing with the oscillator frequency and carrying the carrier carrier used for synchronous demodulation. 10. Receiver for receiving data signals, wherein the data signals are transmitted and received as a single-band signal modulation with the remainder of the carrier, which is transmitted to the long wave band by mixing with the oscillator frequency, and receiving the sideband asynchronously demodulated, mainly by spectral frequency component analysis modulation product. 7 / 1/1 RDS-QDSB RDS modulated 57kHz carrier position ZF RF signal