The Johns Hopkins University

Whiting School of Engineering

Department of Electrical and Computer Engineering

Applications of Orthogonal Frequency-Division Multiplexing (OFDM) to Radar

Seminar By

John P. Stralka

Graduate Research Assistant

Electrical and Computer

Abstract:

Orthogonal Frequency-Division Multiplexing (OFDM) is a wideband, multicarrier digital communications modulation technique in which high-rate data is transmitted in parallel at a slower rate over a frequency-selective channel via multiple closely-spaced narrowband orthogonal subcarriers. With a large number of OFDM subcarriers, each frequency segment, or subband, in the signal spectrum spanned by a single modulated subcarrier can be viewed as being a frequency-flat, as opposed to a frequency-selective, channel. This allows channel equalization in the frequency domain on a subband-by-subband basis, through simple amplitude and phase compensation. Time and frequency synchronization is crucial in OFDM communications systems to preserve subcarrier orthogonality. For radar, however, sensitivity to synchronization is beneficial since the radar receiver uses a stored version of the transmit signal to measure time-delay (range) and frequency (Doppler) offsets between the transmitted signal and the received echo to derive target parameters.

I propose to exploit the multicarrier nature of OFDM to solve three problems in radar:

1.) Time dispersion across electrically-long phased array antennas with the use of wide instantaneous bandwidth pseudo-random coded pulses

2.) Multipath-induced search detection fading of low-altitude targets experienced with surface-based radars

3.) Poor spectral efficiency of diverse, quasi-orthogonal phase-coded signals for use in Multiple-Input Multiple-Output (MIMO) radar systems.

Friday, September 28, 2007

11:00 AM

Barton 114

Refreshments will be served at 10:45 AM

FOR DISABILITY INFORMATION

CONTACT: Candace Abel (410) 516-7031 cabel@jhu.edu