Abstract
Conventional GNSS receiver designs are based on the fundamental concept
of correlation between the received GNSS satellite signal and a reference
code of interest to acquire. The correlation as implemented in today
widely used receivers assume different forms such as active parallel
correlators and passive matched filters, either in hardware or in
software or hybrid. This paper introduces the concepts of satellite
signal channel transfer function and signal channel impulse response
and present their use to design GNSS receivers for timing and positioning
as well as for propagation and environment characterization. One
advantage of this design approach is that the satellite specific
signal channel transfer function/impulse response does not depend
on the underlying code sequence. This is in sharp contrast to correlation
function which is code dependent. Such dependence requires a conventional
receiver to handle a BOC modulation code differently than a BPSK
modulation code. This is because the former has many sidelobes of
significant strength as compared to the mainlobe. Without special
hardware and software, a conventional receiver runs the risk of being
trapped in nulls (missing detection) or of locking onto a sidelobe
(biased measurements). Ideally, the satellite signal channel impulse
response is a Dirac delta function which has an infinite time resolution
capability, thus being immune to multipath. In practice, however,
both the satellite signals and receivers are bandlimited. The impulse
response estimated from sample data is a sinc function with its first
nulls at +/-Ts, where Ts is the sampling interval. Even so, the impulse
response peak still has its base much narrower than that of a correlation
function. As such, it is less sensitive to multipath than conventional
receivers. In this paper, we formulate the concepts, present the
novel GNSS receiver architecture, and detail implementation schemes.
Simulation results are also presented to illustrate the utilities
of this novel design approach.
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