Channel Leakage Cancellation for Software Defined Radio (SDR) Narrowband Radar Interferometry Using GNU Radio

Abstract

Because the SDR has both an RF transmitter and a receiver
integrated in the same module, leakage from transmit into
receive path is inevitable. Without proper compensation,
the received radar signal is combined with this
unintentional leakage signal from the transmit path
creating unintended distortion in phase and amplitude. This
type of accuracy degradation has been reported in the
previous publication when a Multiple Frequency
Continuous Wave (MFCW) distance sensing radar was
created with SDR.[1] A traditional Pulse or FMCW radar
needs 1GHz bandwidth (BW) to achieve 15cm resolution
for short range applications, making a typical SDR’s 4-
60MHz BW seem far from adequate for distance sensing.
However, in this project, a new interferometry radar
solution is demonstrated to make short range distance
sensing possible using bandwidth-limited SDR. This new
concept opens the doors to many short-range radar
applications using this low cost SDR technology and will
help to overcome the high power and harsh interference
associated with traditional ultrawide band radars. Major
improvement in distance sensing accuracy has been
achieved by introducing two all-software solutions in GNU
Radio for leakage cancellation and automatic erroneous
result correction. This article will highlight how GNU
Radio was used not only as a simulator in the debug phase
but also as the end solution to the actual leakage
cancellation in the radar operation.