What's the "PSK "?

The English quadraturephaseshiftkeying abbreviation, stands for orthogonal phase shift keying, is a digital modulation method. The four-phase Phase Shift Keying Signal is short for "PSK ". It can be divided into absolute phase shifting and relative phase shifting.

The following figure shows the principle of the following:

The following digital demodulation methods are available: analog-to-digital conversion, extraction or interpolation, matching filtering, clock and carrier recovery.

 

In the actual tuning and demodulation circuit, non-coherent carrier demodulation is adopted. The frequency deviation and phase jitter exist between the local vibration signal and the carrier signal at the transmitting end, therefore, the decoded analog engineer and Q baseband signals are signals with carrier errors. Even if this analog baseband signal uses a timing accurate clock for sampling and determination, the obtained digital signal is not the modulation signal of the original transmitting end. The accumulation of errors will increase the bit error rate after sampling, therefore, the digital PSK demodulation circuit must compensate the carrier error to reduce the impact of non-coherent carrier demodulation. In addition, the ADC sampling clock is not extracted from the signal. When the sampling clock is different from the input data, the statistical signal-to-noise ratio of the sample value obtained during sampling is not the highest and the error rate is high. Therefore, a clock synchronized with the input symbol rate needs to be restored in the circuit, fixed sampling error correction, and accurate bit timing information can provide a correct clock for Channel Error Correction and decoding after digital demodulation. The correction method is implemented by the timed recovery and carrier recovery modulesAlgorithmGenerates timing and carrier errors. the interpolation or Extraction Tool extracts or interpolation the sampled values after A/D conversion under the control of timing and carrier error signals, obtain the value of the signal at the optimal sampling point. Different chips use different algorithms. For example, the maximum likelihood Algorithm for joint estimation of carrier phase and timing phase can be used by the data-assisted method (DA.

 

Link: http://www.hudong.com/wiki/qpsk