RU2505925C2 - Method for simultaneous emission of high-frequency analogue and digital signal from one transmitter - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: disclosed is modernisation of a method of modulating a high-frequency signal broadcast by one transmitter with simultaneous emission by the transmitter of an analogue broadcast AM signal and a digital radio broadcast DRM signal (Simulcast mode), wherein the analogue part of the emitted signal is an amplitude-modulated signal with one or two sidebands. The analogue part of the AM signal has to undergo dynamic processing (DOAM) by varying the carrier level synchronously with the envelope of the modulating signal, wherein both the carrier level and the side level undergo processing.

EFFECT: high efficiency of transmitting a high-frequency signal in Simulcast mode during the transition period from analogue to digital broadcast.

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Description

The invention relates to the field of LF and MF broadcasting (HF communication), and in particular to increasing the efficiency of transmitting an HF signal during the transition period until the listeners are saturated with digital radios. The problem of simultaneous emission of analog and digital RF signals from one transmitter (receiver) (analog and digital) is to maintain the service area and signal quality, as well as the issue of reducing power consumption. These problems can be solved both by increasing the efficiency of the transmitter, and by applying new modulation methods.

Known technical solutions that allow due to the timely overlap of the radiation channel for one of the transmitted signals to produce amplitude modulation of the analog AM signal (1). However, this technical solution requires the development of non-standard equipment, which significantly complicates and increases the cost of the task. Known technical solutions in which the sideband of an analog signal is modulated by a digital signal, and the other sideband by an analog signal (2). This technical solution requires additional correction during demodulation. The Simulcast system (simultaneous emission by a single transmitter of a signal of analogue broadcasting AM and digital broadcasting DRM: AM + DRM) is described in the European standard ETSI ES 201 980 v3.1.1 (2009-08) (3). There is also a known modulation method called DAM - dynamic processing, in which the carrier is controlled in proportion to the average modulation level (4) as well as the DUN dynamic carrier control.

The present invention provides a method for transmitting an RF signal radiated by one transmitter while simultaneously emitting an analog AM broadcast signal and DRM digital broadcast transmitter, in which the analog part of the emitted signal is an amplitude-modulated signal with one or two side bands. Part of the AM signal is subjected to dynamic processing (DOAM) by changing the level of the carrier in time with the envelope of the modulating signal, while the processing is subjected to both the carrier level and the level lateral or side.

The following are examples of the implementation of the claimed invention.

Figure 1 shows the options of the Simulcast mode in accordance with the standard ETSI ES 201 980 v3.1.1 (2009-08) the analog part of the emitted signal in Simulcast mode, which is a classic amplitude-modulated signal with two side bands - mode A3E (or single-band modulation with equal values of the levels of the carrier and one side at 100% modulation).

Figure 2 presents the mode A3E, as a function of the values of high-frequency oscillations during time t.

Figure 3 presents (s) a graph of changes in the values of the levels of the carrier and the side, as well as their total value for the values of the modulation index m from 0 to 1.

4, the DRM signal has the appearance of high-frequency oscillations during time t.

Figure 5 high-frequency signals AM and DRM (Simulcast) on the linear part of the modulation characteristic of the transmitter. For convenience, we present a two-part modulation characterization.

The AM signal (left) maximizes the modulation characteristic of the transmitter only with modulation indices m = 1. Considering that the average modulation index m = 0.3 ÷ 0.4, we obtain a serious underutilization of the modulation characteristic in the region of the AM signal. To increase the average value of the modulation index m, it is possible to use sound compression devices, but at the same time you can get the sound-wall effect, which will adversely affect the sound of the radio station.

Figure 6 presents a graph of the changes in the values of the levels of the carrier and side (side) depending on the modulation index m for DOAM.

Figure 7 presents the RF signal using DOAM.

On Fig shows how the DOAM mode allows you to generate an AM signal with a constant peak value of the amplitude of the RF signal regardless of the modulation index m, which allows you to maximize the modulation characteristic of the transmitter.

In broadcasting, the Dynamic Carrier Control (DLS) method is widely used in transmitters operating with amplitude modulation (A3E). In the DUN mode, the carrier level changes according to a certain law in time with the envelope of the modulating signal. In this case, one can obtain significant energy savings and preserve the coverage of the transmitter, provided that at m = 0 the level of the carrier will be equal to the rated power of the transmitter. At the same time, when using a DUN, the dynamic range of the modulating signal at the output of the receiving device will be distorted, since only the transmitter carrier is subjected to dynamic processing.

To maximize the use of the modulation characteristic when transmitting an AM signal and obtaining a larger service area, it is proposed in Simulcast mode to use the dynamic processing of the analog part of the AM signal (DOAM). In the case of using DOAM, both the carrier level and the side (or side, if using single-band modulation with equal values of the levels of the carrier and one side at 100% modulation).

Due to this, when using DOAM, there are no dynamic distortions at the output of the receiving device, as in the receiver path the AGC compensates for the dynamic processing of the AM signal.

The use of the DOAM mode in the analogue part of the Simulcast signal allows more efficient use of the modulation characteristic of the transmitter. In this case, the service area of the transmitter with the analog part of the Simulcast signal using DOAM will be approximately the same as the broadcast area of the transmitter operating in purely analog mode using classic AM (A3E). At the same time, in the transmitter signal, the digital component of the Simulcast signal will provide approximately the same coverage area as the analog part of the signal in the DOAM mode with the appropriate choice of the level of the ratio between the analog and digital parts of the Simulcast signal.

Information sources

1. RU No. 2140708, H03C 5/00, 1994.

2. RU No. 2317644, Н04В 20/36, 2008.

3. ETSI ES 201 980, v. 3.1.1 (2009/08), Digital Ratio Mondial (DRM) System Specification.

4. MKKP XVI, Plenary Assembly, Dubrovnik 1986, “Methods for saving energy when broadcasting broadcast programs using AM, and their impact on reception quality.”

Claims (1)

A method of transmitting an RF signal radiated by one transmitter while simultaneously emitting an analog broadcast signal AM and digital broadcasting DRM (Simulcast mode), wherein the analog part of the emitted signal is an amplitude-modulated signal with one or two side bands, characterized in that the analog part The AM signal is dynamically processed (DOAM) by changing the level of the AM signal per clock with a control signal obtained from the modulating signal.

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