19 research outputs found
A beamforming comparative study of least mean square, genetic algorithm and grey wolf optimization algorithms for multipath smart antenna system
Multipath environment is a limitation fact in optimized usage of wireless networks. Using smart antenna and beamforming algorithms contributed to that subscribers get a higher-gain signal and better directivity as well as reduce the consumed power for users and the mobile base stations by adjusting the appropriate weights for each element in the antenna array that leads to reducing interference anddirecting the main beam to wanted user. In this paper, the performance of three of beamforming algorithms in multipath environment in terms of directivity and side lobe level reduction has been studied and compared, which are least mean square (LMS), genetic algorithm (GA) and grey wolf optimization (GWO) technique. The simulation result appears that LMS algorithm aids us to get the best directivity followed by the GWO, and we may get most sidelobe level reduction by using the GA algorithm, followed by LMS algorithm in second rank.Â
IRCI Free Range Reconstruction for SAR Imaging with Arbitrary Length OFDM Pulse
Our previously proposed OFDM with sufficient cyclic prefix (CP) synthetic
aperture radar (SAR) imaging algorithm is inter-range-cell interference (IRCI)
free and achieves ideally zero range sidelobes for range reconstruction. In
this OFDM SAR imaging algorithm, the minimum required CP length is almost equal
to the number of range cells in a swath, while the number of subcarriers of an
OFDM signal needs to be more than the CP length. This makes the length of a
transmitted OFDM sequence at least almost twice of the number of range cells in
a swath and for a wide swath imaging, the transmitted OFDM pulse length becomes
long, which may cause problems in some radar applications. In this paper, we
propose a CP based OFDM SAR imaging with arbitrary pulse length, which has IRCI
free range reconstruction and its pulse length is independent of a swath width.
We then present a novel design method for our proposed arbitrary length OFDM
pulses. Simulation results are presented to illustrate the performances of the
OFDM pulse design and the arbitrary pulse length CP based OFDM SAR imaging.Comment: 29 pages, 10 figures, regular pape
Adaptive Radio Frequency Interference Mitigation for Passive Bistatic Radar Using OFDM Waveform
High frequency passive bistatic radar (HFPBR) is a novel and promising technique in development. DRM broadcast exploiting orthogonal frequency division multiplexing (OFDM) technique supplies a good choice for the illuminator of HFPBR. HFPBR works in crowded short wave band. It faces severe radio frequency interference (RFI) problem. In this paper, a theoretical analysis of the range-domain correlation of RFI in OFDM-based HF radar is presented. A RFI mitigation method in the range domain is introduced. After the direct-path wave rejection, the interference subspace is constructed using the echo signals at the reserved range bins. Then RFI in the effective range bins is mitigated by the subspace projection, using the correlation among different range bins. The introduced algorithm is easy to perform in practice and the RFI mitigation performance is evaluated using the experimental data of DRM-based HFPBR