The Application of DFT Technology in Soft Demodulation of π/4-DQPSK Signals

Presented to the π / 4 differential quaternary phase shift keying signal (π/4-DQPSK) using the discrete Fourier transform (DFT) for software demodulation algorithm in consideration of the actual received waveform into transition to π/4-DQPSK District and stable region, and only the waveform sampling point DFT transform the region stable recovery decision. simulation gives the demodulation method to achieve the same differential demodulation relatively simple structure, and the anti-noise in the signal to noise ratio greater than 3dB better performance than the differential demodulation performance, expected the algorithm is applied π/4-DQPSK software radio receiver design.

Study on Multipath Effect under the Environment of PCM/FM Telemetry Soft Demodulation

Because the reentry telemetry wireless channel multipath propagation effects and the effect, channel will introduce transmission time delay dispersion, caused between the PCM/FM telemetry signal crosstalk and signal to noise ratio is too low, significantly increase BER. While traditional demodulation method because the demodulator threshold higher no longer apply. Study the problem, a multiple Symbol Detection method based on sliding strategy (Multi - Symbol Detection, MSD), can effectively overcome the low SNR and inter symbol interference. The simulation and test results verify the effectiveness of the method.

Study of Reentry Telemetry Signal in the Environment of Soft Demodulation

PCM/FM system is one of the most widely used in the rocket telemetry system. Target spacecraft reentry telemetry telemetry signals in the process of low signal noise ratio (SNR), that the breakthrough tradition demodulation method of demodulation threshold problem, combined with the PCM/FM signal phase characteristic, the research based on a baseband complex rotating orthogonal symbol detection software (MSD) to solve method, and the corresponding synchronization algorithm is applied to ensure the smooth operation of the demodulation. The simulation and test results verified the soft demodulation algorithm can make the demodulation threshold effectively reduce.