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Method and arragnement for digital transmission using AM emitters

A digital transmission and transmitter technology, applied in transmission systems, broadcasting devices, broadcasting circuit devices, etc., can solve the problems of out-of-band and parasitic emission increase, interference, etc.

Inactive Publication Date: 2008-05-28
DEUTSCHE TELEKOM AG
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Problems solved by technology

[0018] If the amplitude signal of an AM transmitter operating in a non-linear mode is clipped, non-linear distortions arise, leading on the one hand to an increase in out-of-band and spurious emissions, and on the other hand to a ratio greater than that caused by the mode of operation of the transmitter The out-of-band and spurious emissions are much higher than the in-band interference

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  • Method and arragnement for digital transmission using AM emitters

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Embodiment Construction

[0023] If the operating point of the transmitter is shifted to form a linear mode of operation, then non-linear distortion is prevented. For linear operation, known from the digital systems DAB and DVB, the output stage of the transmitter is driven with a complex modulated data signal (I / Q signal).

[0024] For spurious emissions, linear operation of the transmitter is advantageous. This has a much larger gradient than the previously described non-linear mode which allows for better calibration of the ITU spectral mask in conjunction with the transmitter. Only the transmitter efficiency is very low in linear operation, which leads to high cost of electricity.

[0025] The efficiency of AM transmitters during linear operation is poor because the full supply voltage has to be applied to the transmitter output stage even when the stage is driven low, and also because power is converted to heat due to quiescent currents in the transmitter output stage . Improved efficiency is a...

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Abstract

During digital transmission using existing non-linear AM emitters, spurious emissions occur as a result of the non-linear distortions, in turn causing inner band disturbances and also disturbing adjacent channels, as out-of-band radiation. Non-linear distortions are especially critical for digital multiple carrier signals (e.g. OFDM) which are recommended by the ITU with the DRM system for the AM area. In order to avoid the non-linear distortions, the end step of the AM emitter is operated in the linear mode, thus ensuring the ITU spectrum mask. The relatively low efficiency of the emitter during the linear operation can be improved by tracking the distribution voltage of the emitter end step according to the drive. To this end, the envelope of the complex modulated data signal is scanned, and said signal controls the distribution voltage for the emitter end step by means of the modulator operating as a switched-mode power supply unit.

Description

technical field [0001] The present invention relates to the field of broadcast transmitters which are converted from analog amplitude modulation (AM) to digital modulation as digitization advances. Background technique [0002] In this context, the invention is to enable the continued use of the type of transmitter commonly used today, a non-linear AM transmitter featuring an RF input (radio frequency) as well as an audio input. The reasons are as follows: [0003] AM transmitters work internally in switch mode and thus have 3 times better efficiency than linear transmitters, which are usually used for digital transmissions, eg for DAB (Digital Audio Broadcasting) and DVB (Digital Video Broadcasting). This results in savings in operating costs. [0004] Convincing broadcasters that the switch from analog to digital is more convenient if there is no major initial investment. [0005] Digitization of AM broadcasting can be seen as the only chance to maintain these frequency...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04H20/00H03F1/02H04B1/04H04H20/49
CPCH04H20/49
Inventor D·鲁多尔夫
Owner DEUTSCHE TELEKOM AG
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