Receiver architecture for use with a global positioning system
First Claim
1. A demodulation circuit for use in a global positioning system (GPS) receiver, comprising:
- a reference oscillator generating a frequency of nominally F or an integral multiple thereof, where F=5.115 MHz;
first, second and third demodulation stages for demodulating an L1 GPS signal in an L1 signal channel;
first, second and third demodulation stages for demodulating an L2 GPS signal in an L2 signal channel;
a frequency synthesizer coupled to the reference oscillator, for generating a first local oscillator frequency for application to the first demodulation stages of the L1 and L2 signal channels, and for generating a second local oscillator frequency for application to the second demodulation stages of the L1 and L2 signal channels; and
means for applying the reference oscillator signal to the third demodulation stage of the L1 and L2 signal channels in such a manner that each signal channel after the third stage of demodulation is still modulated at the same nominal intermediate frequency.
9 Assignments
0 Petitions
Accused Products
Abstract
A demodulation frequency plan for use in a global positioning system (GPS) receiver, having three demodulation stages for L1 and L2 signal channels, in which identical local oscillator frequencies are used in the L1 and L2 channels at each demodulation stage, to minimize phase error differences between the two channels. The third stage provides an output at an intermediate frequency high enough to carry the full information bandwidth, thereby simplifying digital sampling of the signal, which is also performed in the third stage. Sampling is performed at a high enough rate to facilitate subsequent conversion to baseband. Moreover, the sampling rate is a binary multiple of the intermediate frequency, and this binary relationship further simplifies conversion to baseband.
28 Citations
5 Claims
-
1. A demodulation circuit for use in a global positioning system (GPS) receiver, comprising:
-
a reference oscillator generating a frequency of nominally F or an integral multiple thereof, where F=5.115 MHz; first, second and third demodulation stages for demodulating an L1 GPS signal in an L1 signal channel; first, second and third demodulation stages for demodulating an L2 GPS signal in an L2 signal channel; a frequency synthesizer coupled to the reference oscillator, for generating a first local oscillator frequency for application to the first demodulation stages of the L1 and L2 signal channels, and for generating a second local oscillator frequency for application to the second demodulation stages of the L1 and L2 signal channels; and means for applying the reference oscillator signal to the third demodulation stage of the L1 and L2 signal channels in such a manner that each signal channel after the third stage of demodulation is still modulated at the same nominal intermediate frequency. - View Dependent Claims (2, 3, 4, 5)
-
Specification