Abstract
A software based, real time, navigational receiver is described. This
provides high-accuracy and flexible operation using C/A, P and M
codes. The receiver has improved dynamic performance and anti-jam
capabilities. It allows incorporation of novel architectures such
as those using Ultra Tight Coupling, RTK type processing, etc. New
and future signals (such as Galileo) can be easily incorporated.
The block processing architecture enables improved dynamic performance,
anti-jam capability, faster acquisition, less susceptibility to multipath,
robust performance, easy transition to GPS/INS integration, and RTK
processing. The flexible, re-configurable, software based, real time
receiver will allow test and measurement of a variety of receiver
architectures. These in conjunction with the data recorder will allow
both real-time and off-line test of new signals and performance of
receivers under difficult conditions. This paper describes the structure,
operation and performance of a real-time dual frequency software
GPS receiver. The receiver consists of the hardware front-end which
downconverts and digitizes the signals from L1 and L2 frequencies,
followed by the FPGA which performs signal correlation. The correlator
output is fed to the PC which then continues signal processing entirely
using software. The dual frequency processing is performed using
semicodeless technique which provides independent carrier and code
tracking of the L2 signal. Software processing of the signals has
been extended to include advanced signal processing techniques such
as beamforming, interference rejection, multipath mitigation etc.
Addition of any novel type of processing using software approach
is greatly simplified. This reduces development time and effort by
an order of magnitude and at the same time allows the benefits of
software receiver while achieving the real-time performance.
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