Receiving circuit in an interference-suppressing communications system comprising narrow-band conventional message modulation and additional pseudo-noise phase shift keying

US4327438A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Paul Walter Baier · Kaiserslautern, DE
• Klaus Dostert · Kaiserslautern, DE
• Madhukar Pandit · Kaiserslautern, DE
• Reinhard Simons · Horb, DE

Key dates

• Filing date: Dec 12, 1979
• Grant date: Apr 27, 1982
• Expiry date: Dec 12, 1999

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04B7/216
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

A receiving circuit for an interference-suppressing communications system having a narrow-band conventional message modulation and additional pseudo-noise phase shift keying (PN-PSK), has a pseudo-random generator whose pseudo-random sequence is identical to the pseudo-random sequence provided by the system transmitter. The pseudo-random generator actuates a phase-shift keying element to cancel the phase shift modulation produced at the transmitter. A matched filter or correlation network for correlation of the pseudo-random sequence at the receiver with the pseudo-random sequence contained in the received signal is provided. The message modulation impairs the function of the matched filter or the correlation network. The degrading influence of message modulation is to be eliminated, at least, reduced. To this end, a demodulation circuit is provided which receives the entire received signal and the signal present after removal of the phase-shift keying to provide an input for the matched filter or correlation network. This signal only exhibits the pseudo-noise phase-shift keying contained in the received signal, but no longer has the message modulation.