BG62545B1 - Method for modulation and device for data signal transport - Google Patents

Abstract

The method and the system are used in communications engineering. The use of single band signal in the long wave range is possible in them. According to the method the subcarrier frequency is modulated quadangularly in two bands with the data. A single-band signal is made of the moduclation signal with residual signal with carrier frequency which is converted into the long-wave range by mixing it with the frequency of a generator after which it is broadcast. The circuitry on the transmission side contains an encoder (2), frequency converter (2, 3), single-band filter (5), frequency converter in the long wave range (6, 7) and transmitter (8), and on the receiving side - amplifier (14) generator (15), mixer (16), band filter (17) and demodulator (18) which can be synchronous or asynchronous. 10 claims, 3 figures

Description

The invention relates to a modulation method and a data transmission device, as well as a receiver for receiving modulated and transmitted data signals applicable in the communication technique.

BACKGROUND OF THE INVENTION

Two-band modulation is known as a method of transmission in different areas of information channels, such as in differential signal during stereo transmission. The RDS signal (RDS = Radio Daten System Information Radio System) for transmitting color-coded information on television broadcasts to the program for additional information in the civilian VHF radio broadcasting. There is a known application of PSK modulation (PSK = Phase Shift Keying) on a subcarrier for compatible data transmission in the AM radio band / 1 /.

These two-band modulations are embedded specifically in information channels in which the bandwidth plays a secondary role.

The carrier frequency required for the demodulation of DSB modulation (DSB = Double Side Band = two-way band) is formed, for example, in stereo transmission, and a pilot frequency of 19 kHz is simultaneously transmitted to generate the carrier of 38 kHz in a high frequency compacted signal. To restore a DSB carrier with identical sidebars, other methods use “Costa's Loop. An example in this regard is the RDS demodulator type SAA6579T.

The desired transmission of the RDS signal (QDSB with two identical sidebands where QDSB is quadrature two-band modulation) over a bandwidth of 4.8 kHz is set.

Broadcasting an RDS QDSB signal with this bandwidth in the longwave and superwave (9 ... 148.5 kHz) bandwidths would cause up to 30 interference from adjacent channels of already coordinated data transmitters.

In view of this circumstance and the related disadvantages of a single DSB broadcast, such as: double bandwidth of the radio signal, distribution of the radiated energy into equal parts in the sidebands, only one such double bandwidth is required for 10 receivers are needed, all of which increase the likelihood of interference from interference. A major problem with the transmission of radio messages of analogue or digital type is the required width of the 15 bands of the modulated product. This means that efforts will have to be made to make optimal use of the natural frequency band resource that can be used for Messages / Information.

In order to narrow the bandwidth, one-band method (SSB = Single Side Band) of PSK-modulated digital signals is known. It is based on the finding that two sidebands with the same content of information appear in the two-band modulation relative to the fictitious radio carrier. Only one sidebar is required to recover the message content, and this already known method requires special schemes to decode received signals / 2 /.

SUMMARY OF THE INVENTION

It is an object of the invention to develop a method and apparatus for transmitting data signals over long-range transmitters, to a large extent eliminating the aforementioned disadvantages. The method, circuit and receiver according to the invention must be able to be quickly and cheaply developed, not require the creation of new chips and allow immediate operation in terminal equipment.

The task is solved by means of single-band transmission of RDS modulation (SSBRDS = Single Side Band - Radio Daten System) with a data modulation method in which a first carrier frequency is modulated by data signals quadrature two-band, where from mo2

ύ. 545 Duplicate signal by filter or phase method a single-band residual signal with a carrier frequency is produced, after which the single-band signal is converted and transferred to the longwave range by mixing with a frequency generator, after which the converted single-band signal is transmitted together with the transformed residual signal carrier frequency.

It is possible to form a single-band residual signal with synthetic generation by a carrier signal of two-band modulated with data signals, the single-band signal being converted and transferred to the longwave range by mixing with the frequency of the generator, after which the converted single-band signal is transmitted together with converted residual carrier frequency signal.

The modulated signal can be obtained using an encoder of the Information Radio System.

The single-band signal is optionally formed by a filter such as the lower or upper sideband of the modulated signal.

The task is also solved by a scheme for transmitting data signals, these data signals entering the RDS encoder, and the output of the RDS encoder is connected to a frequency converter (3, 4), which in turn is output is coupled to a single-pass filter whose output is coupled to a frequency converter (6, 7) for conversion to the longwave range whose output is connected to the input of a longwave transmitter.

The problem is also solved by a receiver for receiving data signals, the data signals being transmitted and received as modulation of a single-band signal with a residual signal with a carrier frequency, which for its transmission is converted into the longwave range by mixing with the frequency from a generator, such as for the conversion of the received signal in the long-wavelength bandwidth of the single-band signal with a residual signal with a carrier frequency, a mixer generator is provided to which a bandpass filter is connected and a bandpass filter is connected. en with the demodulator.

In the receiver the bandpass filter 17 has a bandwidth of 2.4 kHz and includes a frequency of 57 kHz, the demodulator (18) is an RDS demodulator.

In the receiver, data signals are transmitted and received as a modulation of a single-band residual-frequency signal that is transmitted to the long-range by mixing with a frequency generator 5, the transmitted carrier-frequency residual signal is used for synchronous demodulation.

In the receiver, data signals are transmitted and received as a modulation of a single-band residual-frequency 10-band signal that is transmitted to the long-wavelength band by mixing with the generator frequency, and the received sideband is demodulated asynchronously by analyzing the frequency components15. of the product spectrum from modulation.

The advantage of the solution according to the invention is that the Analog Single Band Modulation (SSB) can also be implemented in the Digital Two Band Modulation (DSB = 2PSK). A typical representative for the application of two-band modulation (DSB), or more specifically quadrature two-band modulation (QDSB), is the RDS signal.

By applying the filter method, the lower or upper sideband of the RDS signal can optionally be formed. The digital single-band modulation thus obtained can be shifted to the desired transmission spectrum by mixing with a corresponding generator frequency.

The broadcasting of a sideband, with or without residual carrier frequency signal, is a function of the demodulation method used. Both options are acceptable. It follows that only half of the bandwidth is occupied, unlike one RDS-DSB-, (QDSB) broadcast. In addition, the efficiency of the transmitting station is improved, and hence the energy and operating costs can be reduced at the same radius. Reducing the bandwidth allows reducing the width of the selection bar at the receiving side, thereby reducing the likelihood of interference from interfering signals.

Description of the attached figures

Figure 1 shows a diagram of single-band transmission by RDS modulation;

Figure 2 is a schematic diagram of an application of the method according to the invention;

Figure 3 is a schematic diagram of a single receiver.

The following abbreviations are used in the description and figures:

ARI - information for motorists on the radio;

RDS - Radio Daten System;

SSB - Single Side Bamd;

DSB - Double Side Band;

QDSB - Quadrature Dual Band Modulation (Quadratur-Doppel Seiten Band);

USB - Upper Side Band;

LSB - Lower Side Band]

PSK - Phase Schift Keying;

ZF - Zwischen Frequenz.

The difficulties encountered in transmitting the long wave RDS signal are overcome by the use of the SSB-known methods of the SSB transmission technique in the RDS-QDSB modulation. Unlike analog SSB-modulation, demodulation will need to provide a carrier frequency with appropriate, well-defined frequency and phase.

An exemplary embodiment of the invention

In FIG. 1 shows the RDS signal with its sidebars. The dotted line carrier Ωο = 57 kHz characterizes the non-modulated ARI carrier known from the ARI system. It is quadrature (with a phase difference of 90 ° C relative to the RDS phase and can therefore be used to demodulate a RDS-QDSB sideband.

The preparation of the RDS-QDSB application signal in the longwave range is shown in FIG. 2. Generally, any RDS-RDS encoder known from the VHF-RDS encoder can be used to represent the RDS-QDSB signal carrier (unmodulated ARI).

For the formation shown in FIG. 1 in a dotted upper sidebar (USB) frame with a carrier the filter method is applied here.

This means that in the second step, a frequency conversion of the RDS-QDSB signal (57 kHz) into the filter bandwidth (Ωο- Ωο + pho 2.4 kHz) of the SSB filter is performed. Thus, depending on the generator frequency selected, a lower (LSB + carrier) sideband or upper (USB + carrier) sideband with an intermediate phase is available for the first frequency conversion of the filter output. The second frequency conversion is for transposing the received SSB of the RDS signal with a residual carrier frequency signal (carrier is reduced to the sideband amplitudes maximum) to the requested transmit frequency. In the next step, the signal is amplified to the corresponding transmit power. The way in which the SSB signal is formed (filter method, phase method, respectively synthetic generation) is irrelevant. The application of the method to higher quality DSB-based modulation methods cannot be ruled out. The application of the method is not only related to the longwave range.

The demodulation of the SSB-RDS broadcast is described below.

Generally, demodulation can be performed both synchronously through a coherent subcarrier demodulator that has appropriately specified frequency and phase, and asynchronously without a subcarrier. When using one of the modes of synchronous demodulation, it is necessary to transmit at a transmitter side at the same time a residual signal with a carrier frequency quadrature relative to the side band. Demodulation is performed by synchronous detectors, using synchronous demodulation using a transmitted residual signal with a carrier frequency. In this way, demodulation is performed directly in the band of the main group. If demodulation is asynchronous, measures must be taken on the receiving side to ensure that the supporting phase of the carrier relative to the sideband is missing from the demodulator. Furthermore, it is possible to analyze the demodulation of a signal by the presence of its typical frequency components of the spectrum corresponding to digital 0 or 1 and from there to generate the data stream by modulating the sideband asynchronously, including demodulation by analyzing the frequency components in the modulation product spectrum. This means that demodulation eliminates the dependency on chips that have yet to be developed, since the demodulation product can in any case be further processed by standard digital circuits.

The single-band broadcast RDS signal (SSB-RDS) has already been tested on long waves with a frequency of 123.7 kHz, where the scheme described below in accordance with FIG. 2. An RDS encoder 2 is used as the data source 1 in this particular case, which can provide QDSB modulation with or without carrier frequency. After the first frequency conversion with the first mixing device 3 and the first generator 4, the SSB signal is formed with a residual signal with a carrier frequency in the filter method 5 and by mixing with the help of a second mixing device 6 into which a second generator 7 enters a carrier frequency, which the SSB signal is converted to a transmission frequency, is amplified at 8 and transmitted.

In this way, an AR1 carrier can be used as a residual carrier signal, which can be connected to the RDS encoder. To receive the SSBRDS signal, a known multi-band receiver with a synchronous demodulator is used. Further processing of the basic band RDS band (two-phase signal) does not create any technical problems. The application of the method is not only related to the longwave range.

In FIG. 3 shows a receiver for data signals transmitted by the method according to the invention. From antenna 13, the high frequency signals are provided to the input amplifier 14. The frequency fe + fZF is formed by generator 15, fe being the frequency of the carrier (residual signal with carrier frequency) contained in the high frequency signal, and fZF = 57 kHz. In the mixing step 16, the amplified high-frequency signal is then converted to an intermediate frequency range and passed through a bandpass filter 17 having a bandwidth of 2.4 kHz. It is connected to a standard SAA6579T RDS demodulator 18, which has one output 19, 20 for one clock signal and one data signal. These signals can be decoded according to the rules laid down in the information radio system and then displayed.

Claims (10)

Claims 1. A modulation method for transmitting data signals, wherein a first carrier frequency is modulated by quadrature bi-band data signals, characterized in that a single-band residual carrier signal is generated from the modulated signal by a filter or phase method. frequency, after which the single-band signal is converted and transmitted to the long-wavelength range by mixing with a frequency of a generator, after which the converted single-band signal is transmitted together with the converted residual signal with a carrier frequency. 2. A modulation method for transmitting data signals in which a single-band residual-frequency carrier signal is formed by synthetic generation from a two-band modulated data signal, and the single-band signal is converted and transmitted to the long-wavelength range by mixing with a frequency of generator, after which the converted single-band signal is transmitted along with the converted residual signal with a carrier frequency. Modulation method according to claim 1, characterized in that the modulated signal is received by means of a coding device of the Information Radio System. Modulation method according to any one of the claims 1,3, characterized in that the single-band signal is formed by a filter such as the lower or upper sideband of the modulated signal. 5. Scheme for transmitting data signals, the data signals being fed to the RDS encoder (2), the output of the RDS encoder (2) being connected to a frequency converter (3, 4), which in turn is output connected to a single-pass filter (5), the output of which is connected to a frequency converter (6, 7) for conversion to the longwave range, the output of which is connected to the input of a longwave transmitter (8). 6. Receiver for receiving data signals, the data signals being transmitted and received as modulation of a single-band signal with a residual signal with a carrier frequency, which for 5 transmission is converted to the longwave range by mixing with a frequency from a generator, such as for conversion of the signal received in the long wavelength range at the frequency band of the residual 10 signal with a carrier frequency, characterized in that it has a generator (15) and a mixer (16) to the output of which a tape filter (17) is attached, which is associated with e a modulator (18). A receiver according to claim 6, characterized in that the bandpass filter (17) has a bandwidth of 2.4 kHz including a frequency of 57 kHz. A receiver according to any one of claims 6, 7, characterized in that the demodulator (18) is an RDS demodulator. 9. Receiver for receiving data signals, the data signals being transmitted and received as modulation of a single-band signal with a residual signal with a carrier frequency, which for its transmission is converted to the longwave range by mixing with a generator frequency, characterized in that that the transmitted residual carrier signal is for synchronous demodulation. 10. Receiver for receiving data signals, the data signals being transmitted and received as modulation of a single-band residual frequency carrier signal which is transmitted to the long wavelength range by mixing with a generator frequency, characterized in that that the sideband is demodulated asynchronously by analyzing the frequency components of the modulation product spectrum.