Digital videocast modulating method and device

Abstract

The invention discloses a signal modulation method for digital television broadcasting. The method comprises: multiplexing data signals, pre-generated pilot symbols and synchronous band symbols in the frequency domain, and performing orthogonal frequency division multiplexing on the multiplexed data Use (OFDM) modulation to obtain a time-domain signal; the synchronization band symbol includes a subcarrier that transmits a synchronization symbol and a zero-set subcarrier that does not transmit any information, and the zero-set subcarrier is symmetrical on both sides of the subcarrier that transmits a synchronization symbol Distribution; the pilot symbols occupy a part of subcarriers, and the occupied subcarriers are not adjacent to each other; add a guard interval before the time domain signal, and fill in 0 in the guard interval to form an OFDM symbol; use more than one OFDM symbol and a preamble pilot signal to generate a baseband transmit signal. At the same time, the invention also discloses a signal modulation device for data television broadcasting. The modulation method provided by the invention has the characteristics of low power consumption, fast synchronization and low peak-to-average ratio.

Description

technical field [0001] The invention relates to the field of digital TV broadcasting, in particular to a modulation method and device for digital TV broadcasting. Background technique [0002] Digital TV broadcasting is a research and application hotspot in the field of broadcasting technology at present, and many countries have launched their own digital TV broadcasting systems one after another. At present, there are various modulation techniques for digital TV broadcasting, among which, the DVB-T standard adopts Orthogonal Frequency Division Multiplexing (OFDM) modulation in terms of transmission, which belongs to the multi-carrier transmission technique. [0003] see figure 1 As shown, the modulation structure of the transmitter defined by the DVB-T standard includes an OFDM modulation unit 100 , a guard interval (CP) unit 104 and a framing unit 105 . Wherein, the OFDM modulation unit 100 includes a serial / parallel conversion unit 101 , an inverse fast Fourier transfor...

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Problems solved by technology

[0004] From the above modulation system, CP needs to be inserted into the signal after OFDM modulation. Since CP and data have certain correlation characteristics, the receiver can complete timing synchronization by relying on CP. However, transmitting CP needs to consume a certain amount of power.

However, fading channels, special values ​​of data signals, etc. will deteriorate the correlation between CP and data, thus greatly reducing the speed and accuracy of timing synchronization

[0005] Moreover, for all digital broadcasting systems based on OFDM modulation, there is a common problem: the peak-to-average power ratio (PAPR) is generally high, which will directly lead to a decrease in the use efficiency of the power amplifier of the transmitter, especially when the number of carriers is small. When it is large, such as 8k mode of DVB-T, the power amplifier efficiency of the transmitter is very low

Unfortunately, the existing DVB-T system does not take this issue into account

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