Digital signal transmitting method and equipment based on modulated carriers of equal amplitude and equal period

Abstract

The invention discloses a digital signal transmitting method based on modulated carriers of equal amplitude and equal period, comprising the steps of: sampling two basic wave shapes of f0(t) of 0 representation information and f1(t) of 1 representation information within a period; respectively selecting a storage area which corresponds to f0(t) or f1(t) by a control selection switch of binary information to be transmitted within a wave shape period; converting wave shape samples in the storage area into modulated high-frequency simulating signals under the control of a synchronous clock; transmitting the modulated high-frequency simulating signals subjected to up-conversion modulation, filtering and power amplification; and demodulating the modulated signals before up-conversion on a transmitting end by adopting a demodulating method based on small phase difference or a demodulating method based on zero-crossing detection after the down-conversion of the received signals. The invention also discloses special equipment for implementing the method. A high-efficiency modulating system of equal amplitude and equal period realized by the method further enhances frequency band utilization ratio, ensures the constant performance of the amplitude of the modulating wave shapes, and also strengthens the capability of resisting channel distortion and noise disturbance.

Description

technical field [0001] The invention relates to a digital signal transmission method and equipment based on equal-amplitude and equal-period modulation carrier waves, belonging to the field of digital communication. Background technique [0002] In digital signal transmission, modulation and demodulation is a very important link in the field of electronic communication. Different modulation methods play a decisive role in the performance parameters of a communication system. At the sending end of the communication system, the low-frequency binary baseband signal is usually modulated to the high frequency to facilitate transmission, and the receiving end demodulates the baseband signal on the high-frequency carrier to restore the original sending signal. In recent years, a variety of new modulation and demodulation technologies have emerged. In order to achieve the highest possible frequency band utilization, that is, to transmit higher digital rates (in bps / Hz) within the un...

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Problems solved by technology

[0003] But above-mentioned two patents still have unsatisfactory place

The waveform of "Information modulation and demodulation method of high frequency band utilization" is as mentioned above. The amplitude of the front and rear halves is different. In some occasions where the amplitude is limited, it will affect its demodulation performance. In some waveforms It is not applicable to occasions with uniform amplitude requirements, and because the amplitude in each symbol period is not fixed, it is difficult to combine this technology with traditional AM / FM technology to achieve the transmission of one channel while transmitting analog signals. high-speed digital information

Observing its power spectrum as shown in Figure 2(a), it can be found that the waveform has more high-order harmonics and larger amplitudes, which will not only waste energy but also limit the further improvement of bandwidth efficiency

Although the waveform of "Information Modulation and Demodulation Method with Equal Amplitude and High Frequency Band Utilization" has undergone some limiting processing, in order to further increase the distinction between the two basic waveforms and ensure information transmission under the condition of low signal-to-noise ratio The accuracy of the two basic waveforms needs to be increased by increasing the parameter A (the waveform control parameter in this patent), but it can be clearly seen from Figure 3(b) that with the further increase of the parameter A Large, the amplitudes of the two basic waveforms gradually begin to appear inconsistent, especially when A increases to more than 0.5, the two waveforms have a high degree of discrimination, but the jump of the amplitude of the waveform is already quite obvious. The amplitude of the basic waveform in the patent The biggest advantage of unification will no longer exist. In the occasions where the waveform discrimination is relatively high, it cannot be well combined with the broadcasting system. Because the method used in this patent is to superimpose the spurious waveform on the sine wave, it cannot Fundamentally solve the above defects

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