Apparatus and method for minimizing multipath interference
AssigneeBAE Systems Information and Electronic Systems Integration Inc.
InventorDavid L. Herrick
Life of this patent
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Abstract
A method and apparatus for minimizing multipath interference for commercial FM signals which use SCA secondary signals in QAM format that includes tracking the time series of phase measurements of a received stereo pilot signal for determining the proper phase reference for demodulation of QAM signals at the center of the time series. Phase measurements of the pilot signal are tracked over a predetermined tracking period. The phase measurement is used to support demodulation of the QAM signal. The SCA secondary signals in QAM format transmitted on commercial FM have minimal multipath interference and Doppler interference by movement of transmitter and receiver (vehicular).
Claims20
A method for minimizing multipath interference in the broadcast of FM signals that use secondary signals in a QAM format comprising the steps of:
- a) generating an FM stereo pilot signal of a predetermined median frequency and secondary signals in a quadrature amplitude modulation format;
- a1) receiving said FM stereo pilot signal of said predetermined frequency;
- b) tracking the time series of phase measurements of the received FM stereo pilot signal;
- c) determining the proper phase reference of the FM pilot signal for demodulation of the QAM secondary signals at approximately the center of the time series;
- d) comparing the phase measurements over the time series to detect changes in said phase based upon multipath signal interference and relative movement between transmitter and receiver;
- e) selecting the appropriate phase modulation for demodulation of said QAM secondary signals;
- e1) demodulating the QAM secondary signals without multiple path interference.
An apparatus for minimizing multipath interference in a commercial FM broadcast and receiver system that utilize commercial FM signals that include subsidiary communication authority secondary signals in a quadrature amplitude modulation (QAM) comprising:
- antennae means for receiving commercial FM signals of a predetermined pilot frequency;
- means for tracking a time series of phase measurements of the received FM pilot signal for determining the proper phase reference for demodulation of the secondary QAM signals;
- and
- means for demodulation of the QAM secondary signals at approximately the center of said time series using the proper phase reference of said pilot signal to minimize multipath interference caused by step changes in the phase of the received signals and movement between the transmitter and the receiver.
A method for minimizing multiple path interference for wireless broadcast RF signals that includes a bandwidth that has subsidiary communications authority including secondary signals that use a phase modulation format subject to multiple path and Doppler interference comprises the steps of:
- a) means for broadcasting a pilot signal at a pre determined radio frequency that is not phase dependent on modulation and secondary signals using a phase modulation format;
- b) means for receiving said pilot signal and said secondary signals utilizing a phase modulation format;
- c) tracking a time series of phase measurements of the receiving pilot signal;
- d) determining from the tracked time series of phase measurement the proper phase reference from said pilot signal for secondary signal modulation;
- e) selecting the appropriate phase measurement for demodulation of the phase dependent secondary signals to minimize multiple path interference;
- and
- f) demodulating the data from said secondary signals that was translated in a phase responsive format.
A system for minimizing multipath interference for wireless broadcast RF signals that includes a pilot signal at a predetermined frequency, the modulation and demodulation of which is not phase dependent and that has sufficient bandwidth to have subsidiary communication authority that includes secondary signals at a different frequency that use a phase modulation format that subjects the received secondary signals to multiple path and Doppler interference comprising:
- means for transmitting a pilot RF signal at a pre-determined frequency, the modulation of which is not phase dependent and including the transmission of secondary signals using a phase modulation format that is incorporated into the bandwidth of the pilot signal under the subsidiary communication authority;
- means for receiving said pilot signal and said secondary signals;
- means connected to the receiving means for tracking a time series of phase measurements of the received pilot signal;
- means for determining from the tracked time series of phase measurements the proper phase reference for appropriate secondary signals demodulation connected to said means for tracking;
- and
- means for selecting the appropriate phase measurement for demodulation of the phase dependent secondary signals to minimize multipath interference.
Dependencies are inferred from the claim text.