Method and apparatus for demodulating a carrier wave which is phase modulated by a subcarrier wave which is phase shift modulated by baseband signals

摘要

The invention relates to a method for demodulating a carrier wave which is phase modulated by a subcarrier wave which is phase shift modulated by baseband signals and applies especially to data transmission between a spacecraft and a ground station. The technological problem addressed is reduction of signal degradation and, consequently, of transmission power and size of the receiving antenna. According to the invention, the frequency is first down converted to an intermediate frequency (fc) which is lower than the carrier wave frequency; the subcarrier wave is extracted by phase demodulation using a Costas loop; digital sampling is performed on the signal demodulated in a Costas loop at a frequency which is twice the intermediate frequency (fc) and the bit clock frequency (fB) is regenerated in a first order phase locked loop using the subcarrier wave frequency as a reference frequency.