Dual-carrier ABSK communication system on basis of same narrow-band filter

Abstract

The invention relates to a dual-carrier ABSK communication system on the basis of the same narrow-band filter, which comprises a dual-carrier ABSK modulator and a dual-carrier ABSK demodulator. The dual-carrier ABSK modulator is used for alternately modulating each data bits of a path of data sequence with a code rate of 2Rbps onto two paths of ABSK signals of which carrier frequencies respectively are fc1 and fc2 and both the code rates are Rbps; on the two paths, a T time interval is reserved between positions at which each path of '1' code element appears, i.e. the simultaneous appearance of '1' on the two paths of carrier frequencies can be completely eliminated at an initial end; and T represents a code element period of the data sequence; the dual-carrier ABSK demodulator comprises the narrow-band filter of which both left and right transition zones are very precipitous; and when the carrier frequencies fc1 and fc2 are respectively positioned at the high-slope positions of the left and right transition zones, the narrow-band filter utilizes the slope phase demodulation characteristic to convert phase information of a double-carrier ABSK receiving signal at the position of each path of code element '1' into obvious and strong parasitic amplitude modulation impact, so that an envelope detector can output an impact envelope pulse which is naturally combined into the code rate 2Rbps.

Description

technical field [0001] The invention belongs to the field of information modulation and demodulation in digital communication, relates to a digital communication system, in particular to a communication system which utilizes the same narrow-band filter to demodulate two-way ABSK signals. Background technique [0002] 1. Asymmetric binary phase shift keying [0003] Spectrum is a non-renewable resource that bears various growing wireless services and is precious to all countries in the world, as can be seen from the huge bidding price of limited frequency usage rights in Europe. How to use limited spectrum resources more efficiently is also crucial to the sustainable development of my country's modernization drive. [0004] The spectrum utilization rate of the digital communication system can be evaluated by the digital rate (in bps / Hz) that can be transmitted within the unit frequency band, which mainly depends on the frequency bandwidth occupied when the binary data stream...

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Problems solved by technology

[0031] 1) It is required that an extremely narrow notch-frequency selection characteristic must be present in the passband, that is, the amplitude-frequency gain needs to be within 10 of the signal carrier frequency starting from the valley point. -3 In the magnitude bandwidth, it increases sharply to the peak value of at least 30dB above the valley point. This special amplitude-frequency response is not easy to achieve, whether it is a digital filter or a corresponding analog filter;

[0032] 2) In order to achieve sharp frequency-selective characteristics in the passband, several pairs of poles constituting the IIR-type impact filter must be very close to the unit circle, and the radius of a pair of poles should be taken near 0.99995. On the other hand, the digital impact filter When the filter is implemented on hardware, each filter coefficient participating in the operation must be stored in a finite-length register in binary form. At this time, due to the existence of quantization errors, these poles that are very close to the unit circle are likely to move to the unit circle. on or outside the unit circle, making the actual filter network unstable

At the same time, the IIR filter must adopt a recursive structure. In this structure, the rounding of the sequence during the operation sometimes causes a certain degree of parasitic oscillation;

[0033] 3) The unit impulse response of the IIR system continues to infinity, and the frequency selection characteristic of the IIR digital shock filter is extremely sharp (that is, the Q value

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