Patent ID: 6430213
Filing Date: 2002-08-06
Classification: H04B

Abstract:
A system for modulating DS data on an I phase communicating DN data and on a Q phase communicating the DN data, the I phase and Q phase are phases of a modulated carrier signal communicating the DN data, the carrier signal has a total phase equal to arctangent of the Q phase divided by the I phase, the DN data is a GPS navigation message communicated in spread spectrum signals spread by a P(Y) code and a CA code, the DS data is communicated in spread spectrum signals spread by an M code, the DS data is subcarrier data and the M code is a subcarrier code, the system comprising,an encoder for encoding the DN data spread by the P(Y) code into an Io encoded signal, and for encoding the DN data spread by the CA code into a Qo encoded signal, an encoded subcarrier modulation signal generator for receiving the DS data and the M code and the DN data and the P(Y) code and the CA code and for generating an encoded subcarrier modulation signal, the encoded subcarrier modulation signal comprises a product of a data partition function and a code partition function, the data partition function is the DN data, the code partition function is one of the P(Y) code or the CA code, and a modulator for modulating a subcarrier signal by the encoded subcarrier modulation signal for providing a modulated subcarrier signal, for modulating the total phase of the carrier signal by the modulated subcarrier signal, for modulating the I phase of the carrier signal by the Io encoded signal and by an I phase subcarrier signal to provide an I phase carrier signal and for modulating the Q phase of the carrier signal by the Qo encoded signal and by an Q phase subcarrier signal to provide a Q phase carrier signal, the carrier modulator combining the Q phase carrier signal and the I phase carrier signal as a composite signal, the Q phase subcarrier signal is a Q intermodulation product of the encoded subcarrier modulation signal and the Io encoded signal, the I phase subcarrier signal is an I intermodulation product of the encoded subcarrier modulation signal and the Qo encoded signal, the ratio of the Q intermodulation product over the I intermodulation product is equal to the ratio of the Io encoded signal over the Qo encoded signal, the composite signal has a constant amplitude envelop.