TABLE OF CONTENTS A System level functional block diagram of a generic GPS receiver is shown in Fig. 1. The generic receiver consists of the following functions: 1) antenna; 2) preamplifier; 3) reference oscillator; 4) frequency synthesizer; 5) downconverter; 6) an intermediate frequency (IF) section; 7) signal processing; and; 8) applications processing.
In a general sense, not all GPS receivers perform navigation processing. Many perform time transfer or differential surveying, or simply collect measurement data. Thus, the last function is more appropriately called applications processing, thus covering a broad set of applications.
The antenna may consist of one or more elements and associated control electronics, and may be passive or active, depending upon its performance requirements. Its function is to receive the GPS satellite signals while rejecting multipath and, if so designed, interference signals. The preamplifier generally consists of burnout protection, filtering, and a low-noise amplifier (LNA). Its primary function is to set the receiver's noise figure and to reject out-of-band interference.
The reference oscillator provides the time and frequency reference for the receiver. Because GPS receiver measurements are based on the time-of-arrival of pseudorandom noise (PRN) code phase and received carrier phase and frequency information, the reference oscillator is a key function of the receiver. The reference oscillator output is used in the frequency synthesizer, from which it derives local oscillators (LOs) and clocks...
