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An innovative 24 GHz digital beamforming radar system for three-dimensional imaging is addressed in this paper. The presented FMCW radar is characterized by an orthogonal arrangement of a transmitter and receiver antenna array in order to perform digital beamforming in two dimensions. By temporal multiplexing of the transmitter channels and parallel-operated receivers, each propagation path from the mth transmit antenna to the object to the nth receive antenna is made available to the signal processing. The three-dimensional imaging concept and the realized digital beamforming radar as well as signal processing aspects concerning sensor calibration are described in this paper.___________________________________ 978-1-4244-8443-0/11/$26.00 ©2011 IEEE

Orthogonal frequency division multiplexing (OFDM) is very sensitive to frequency offsets which result in considerable interference. Performance of the system will be exacerbated in the uplink of a cellular deployment with frequency reuse of one. A general mathematical model is developed to calculate the amount of interference in cellular OFDM system considering frequency offset between transmitter (Tx) and receiver (Rx), depending on different multiple access and duplexing techniques. An ideal adaptive modulation scheme is applied to compare the capacity of different cellular OFDM systems. It is found that the capacity of frequency division multiple access (FDMA) system outperforms that of time division multiple access (TDMA) system due to multiuser diversity in FDMA. Moreover, time division duplexing (TDD) system outperforms frequency division duplexing (FDD) system irrespective of the multiple access techniques by exploiting time slot (TS) opposing techniques.