外文翻譯---短波通信的現(xiàn)狀及發(fā)展趨勢(shì)-其他專業(yè)(編輯修改稿)
2025-02-24 09:41 本頁面
【文章內(nèi)容簡(jiǎn)介】 adapted technology, autoadapted channel autoadapted weighs the technology, the autoadapted antenna technology and so on. 1) Chooses the frequency and the channel establishment technology autoadapted. The present chooses the frequency and the channel establishment technology is autoadapted with the correspondence unifies in together, will choose frequency quality to be lower than the frequency quality which like the specialpurpose realtime frequencyselective system will provide. From now on the development direction should be unifies the specialpurpose frequencyselective system and the adaptive munication system, enters one step to improve the shortwave munication quality. 2) Transmission speed autoadapted technology . Shortwave munication after designation operating frequency, must in obtain the biggest data volume of goods handled along with on the time variation channel, must use the transmission speed autoadapted technology. Usually should choose as far as possible the high data transfer rate under the permission error rate condition, this need system uses the code and the modulator approach and the channel condition incident crosscorrelation, when the channel dissemination characteristic is good with high transmission speed transmitter data, but when disseminates the characteristic variation cuts the transmission speed, enables the error rate throughout to satisfy the correspondence quality the request. 3) Autoadapted channel balanced technology. When shortwave timevariable channel transmission signal, to eliminate the multidiameter effect, the Doppler shift and so on serious code which brings to disturb, must use the autoadapted channel balanced technology. The decision feedback equalizer (Decision Feedback Equalizers, DFE) is the present shortwave munication is one kind of balanced technology which the series uses generally. In recent years proposed one kind of new balanced technical Turbo balanced technology, it unifies the channel to arrange the decoding technology, full has used the channel information, enhanced 2~3dB after the parison in the shortwave munication system using the Turbo balanced technology pared with DFE. 4) Autoadapted antenna technology . The autoadapted antenna technology39。s principle is the signal which receives through docking carries on the realtime processing, the control and the adjustment antenna array element phase changes the antenna pattern characteristic, pletes the autoadapted beam forming, enables the antenna beam the zero position alignment disturbance direction, the signal direction gain to achieve most to be big, thus enhances the system antimultidiameter decline and antijamming ability effectively. high speed modulation demodulation technology At present is widespread the application the narrow band shortwave broadcasting station39。s modem to have serial and the parallel two systems, the serial system uses the single carrier to modulate the transmitter data, before item of , the maximum speed is , is very high to the balanced request。 The parallel system is the data parallel allocation which transmits to many subcarriers in transmits, the tradition and in the good system each subcarrier does not overlap mutually in the frequency spectrum, separates each subchannel in the receiving end with the filter group, between each subchannel must leave leeway protects the frequency band, the frequency band use factor is low, moreover many filter realize also have the difficulty, at present the maximum speed is only (Orthogonal Frequency Division Multiplexing, OFDM) the modulation system is quick by its transmission speed, frequency band use factor Gao Hekang multidiameter ability strong and so on merits is valued people39。s more and more, also starts to apply gradually in shortwave munication domain . Is opposite in the single carrier and nonorthogonal the frequency division multiplying way, OFDM applies in the shortwave munication has following superiority : 1) Antifrequency selectivity decline. The OFDM system and transforms the high speed data stream through the string, causes in each subcarrier the data mark t
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