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AssigneeAgence Spatiale Europeenne
InventorsEnno E. Lijphart, Gerardus Drewes
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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 (f.sub.c) 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 (f.sub.c) and the bit clock frequency (f.sub.B) is regenerated in a first order phase locked loop using the subcarrier wave frequency as a reference frequency.
A method for demodulating a carrier wave which is phase modulated by a subcarrier wave which is phase shift modulated by baseband signals, according to which at least one phase demodulation process is performed using a Costas tracking loop to regenerate the carrier wave, wherein the baseband signals obtained are all subsequently sampled, then decoded, characterized by the fact that a carrier wave frequency is first converted to an intermediate frequency which is lower than the carrier wave frequency, that the subcarrier wave is extracted by a phase demodulation process using a modified Costas loop having a digital circuit portion comprising a waveform synthesizer by which the subcarrier is regenerated and matched digital filters, that digital sampling is then performed on the signal demodulated in said modified Costas loop at a frequency which is twice the frequency of the intermediate frequency and that a bit clock frequency is regenerated in a first order phase locked loop wherein the subcarrier wave frequency is used as a reference frequency in regeneration of said bit clock frequency.
An apparatus for implementing a process for demodulating a carrier wave which is phase modulated by a subcarrier wave which is phase shift modulated by baseband signals, by which at least one phase demodulation process is performed using a Costas tracking loop to regenerate the carrier wave, wherein the baseband signals obtained are all subsequently sampled, then decoded, wherein a carrier wave frequency is first converted to an intermediate frequency which is lower than the carrier wave frequency, and the subcarrier wave is extracted by a phase demodulation process using a modified Costas loop, characterized by the fact that each "data" arm and "error" arm of the modified Costas loop comprises, in sequence, a demodulator mixer circuit which receives a waveform at subcarrier wave frequency, a bandpass filter, a sampling multiplier which receives a signal at a frequency which is twice the intermediate frequency, an analog to digital converter and a matched digital filter controlled by the bit clock frequency and the output of which is received by a multiplier of "data" and "error" arm signals.
An apparatus for implementing a process for demodulating a carrier wave which is phase modulated by a subcarrier wave which is phase shift modulated by baseband signals, by which at least one phase demodulation process is performed using a Costas tracking loop to regenerate the carrier wave, wherein the baseband signals obtained are all subsequently sampled, then decoded, wherein a carrier wave frequency is first converted to an intermediate frequency which is lower than the carrier wave frequency, and the subcarrier wave is extracted by a phase demodulation process using a modified Costas loop, and comprising at least one processor of a bit slice type which executes at least some digital functions of the process, wherein functional analog processes are executed in technology known as integrated function technology.
Dependencies are inferred from the claim text.