System and method for amplitude pre-distortion optimization for gps signal constant envelope transmission
AssigneeThe Boeing Company
InventorCornel Prunean
Life of this patent
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Abstract
A system and method include a modulator configured to combine satellite codes with carrier signals on an in-phase channel and a quadrature-phase channel to produce I-channel and Q-channel signal components. The powers of the combined satellite codes are selected according to desired code power fractions. A processor pre-distorts the signal components such that they can be transmitted as a unit-amplitude constant envelope transmission that preserves the desired code power fractions. The pre-distortion may also account for data filtering effects that tend to distort the code power fractions.
Claims20
A system comprising:
- a signal waveform generator combiner/modulator (WGCM) configured to:
- multiplex, on an in-phase channel (I-channel), a first set of satellite codes of a plurality of satellite codes to create a base-band in-phase signal component,
- multiplex, on a quadrature-phase channel (Q-channel), a second set of satellite codes of the plurality of satellite codes to create a base-band quadrature-phase signal component,
- modulate the base-band in-phase signal component and the base-band quadrature-phase signal component onto an RF carrier;
- and
- a processor coupled to the WGCM and configured to pre-distort the base-band in-phase signal component and the base-band quadrature-phase signal component, such that after modulation of the in-phase and quadrature-phase signal components a power ratio of a modulated in-phase signal component to a modulated quadrature-phase signal component falls within a predetermined range.
A method of transmitting a GPS signal, comprising:
- modulating, on an in-phase channel (I-channel), a first portion of data using a first combination of two or more satellite codes of a plurality of satellite codes;
- modulating, on a quadrature-phase channel (Q-channel), a second portion of the data using a second combination of two or more satellite codes of the plurality of satellite codes;
- combining each of the modulated first and second portions of the data with a respective carrier signal to produce an in-phase signal component and a quadrature-phase signal component;
- before modulating the data, pre-distorting the data such that a power ratio of the in-phase signal component to the quadrature-phase signal component falls within a predetermined range after modulating the data;
- and
- transmitting the in-phase signal component and the quadrature-phase signal component as a constant envelope signal.
A GPS satellite, comprising:
- a satellite body;
- a GPS signal payload including a modulator and a processor coupled to the modulator;
- and
- a power source configured to provide power to the GPS signal payload;
- wherein the modulator is configured to:
- modulate, on an in-phase channel (I-channel), a first portion of data using a first combination of two or more satellite codes of a plurality of satellite codes,
- modulate, on a quadrature-phase channel (Q-channel), a second portion of the data using a second combination of two or more satellite codes of the plurality of satellite codes, and
- combine each of the modulated first and second portions of the data with a respective carrier signal to produce an in-phase signal component and a quadrature-phase signal component;
- and
- wherein the processor is configured to pre-distort the data, before modulation of the data, such that a power ratio of the in-phase signal component to the quadrature-phase signal component after modulation of the data falls within a predetermined range.
Dependencies are inferred from the claim text.