On Co-Existence of In-Band UWB-OFDM and GPS Signals: Tracking Performance Analysis

The problem of in-band co-existence between GPS and other potential interfering signals is viewed from the following angle in this paper: Is there a coding or modulation technique which would permit simultaneous use of GPS and other RF services occupying same bandwidth? Very low interference between the UWB radar and GPS signals can be achieved by shaping radar pulses using orthogonal frequency division multiplexing (OFDM) coding, which is a multi-carrier modulation technique targeted for commercial UWB communications. The paper shows that we can, in fact, expect a very good degree of interoperability of a system used for GPS reception and UWB-OFDM radar purposes. The benefits of using UWB sensor in conjunction with GPS can be for example, to supplement positioning algorithms with radar-collected data, as well as to perform general reconnaissance of the surrounding area. The paper includes detailed analysis of the proposed multiple-use UWB-OFDM radar/GPS receiver concept, the effect of co-existing UWB-OFDM signals on GPS receiver tracking loop carrier noise level, and the impact on the quality of GPS solution in weak GPS signal environment. A brief discussion of MATLAB implementation of the modeled scenarios is presented as well

SAR Imaging Using Fully Random Bandlimited Signals

A coherent ultrawideband (UWB) random noise synthetic aperture radar (SAR) has been developed and tested at the University of Nebraska. It has been experimentally shown that this type of radar is capable of extracting the phase and the amplitude of the backscattered signal, thus enabling us to create target profiles in the frequency domain. The use of fully random waveforms (bandlimited noise) as the transmit signal is analyzed in this paper. A UWB signal model is developed and radar signal processing is simulated to yield statistical characteristics of image formation using stochastic waveforms. The influence of UWB signal characteristics on the image quality is estimated and represented graphically

Multifrequency OFDM SAR in Presence of Deception Jamming

<p/> <p>Orthogonal frequency division multiplexing (OFDM) is considered in this paper from the perspective of usage in imaging radar scenarios with deception jamming. OFDM radar signals are inherently multifrequency waveforms, composed of a number of subbands which are orthogonal to each other. While being employed extensively in communications, OFDM has not found comparatively wide use in radar, and, particularly, in synthetic aperture radar (SAR) applications. In this paper, we aim to show the advantages of OFDM-coded radar signals with random subband composition when used in deception jamming scenarios. Two approaches to create a radar signal by the jammer are considered: instantaneous frequency (IF) estimator and digital-RF-memory- (DRFM-) based reproducer. In both cases, the jammer aims to create a copy of a valid target image via resending the radar signal at prescribed time intervals. Jammer signals are derived and used in SAR simulations with three types of signal models: OFDM, linear frequency modulated (LFM), and frequency-hopped (FH). Presented results include simulated peak side lobe (PSL) and peak cross-correlation values for random OFDM signals, as well as simulated SAR imagery with IF and DRFM jammers'-induced false targets. </p

Integration of Circuit Design and Signal Integrity Analysis: An applied frequency-domain approach Author/point of contact:

In this proposal a new methodology of system-level analysis for high-speed data transfer systems is presented. The methodology integrates CMOS AFE circuits and interconnect modeling into one simulation process, based on frequency-domain analysis, which is better suited for analog signal processing. The emphasis will be made on computationally efficient simulation process that yields comprehensive system performance data. The outcome of the project will allow avoiding deficiencies associated with time-domain simulation methodology – lengthy and labor-intensive modeling, incomplete point solutions, and often disjoint results pertaining to circuit and interconnect performance. By transforming signal specifications and system parameters into frequency domain, we will arrive to the possibility of solving for worst-case random combinations in a much more direct manner. This will allow for computationally efficient and high-confidence I/O system design.