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As a novel code-acquisition scheme, the twin-cell detection (TCD) is proposed for the acquisition in time of spread-spectrum codes in the presence of fractional Doppler frequency offset (FDFO). When the FDFO exists, the correlation peak that is used for detection during the acquisition process is split into two neighboring peaks with smaller magnitudes, which results in a considerable degradation in the overall acquisition performance of conventional schemes. In the TCD, the decision variable for detection is formed by combining two consecutive correlator outputs so that the influence of the reduction in the correlation peak due to the FDFO can be alleviated. The numerical results show that the TCD can offer a better mean-time-to-synchronization performance than the conventional scheme based on the cell-by-cell detection. Index Terms--Code acquisition, fractional Doppler frequency offset (FDFO), spread-spectrum (SS), twin-cell detection (TCD).

A novel pre-equalization method for terrestrial DTV transmitters is presented. A pre-equalizer is used in transmitters to correct group delay and amplitude distortions caused by a channel filter. In the proposed pre-equalizer, an equation-error adaptive IIR filtering scheme is adopted unlike the conventional pre-equalization using FIR filtering. The pole-zero modeling property of IIR filters improves the signal-to-noise ratio by compensating for various linear distortions existing in DTV transmitters as well as the channel filter distortion. Simulation results show that the proposed IIR pre-equalizer performs better than the FIR pre-equalizer in terms of the residual mean-square error. Index Terms--Channel filter, DTV, IIR, pre-equalizer, transmitter.

In this paper, we propose and analyze concatenated coding schemes for direct-sequence code-division multiple-access (DS/CDMA) systems in asynchronous channels. In the concatenated coding, bandwidth-efficient [2.sup.2L-2]-state L/(L+1)-rate 2-MTCM with biorthogonal signal constellation is used for the inner code, and ([2.sup.L]-1, [([2.sup.L]-1)/L/2]) RS code is used for the outer code. It is shown that we can get considerable performance gain over the uncoded system without sacrificing the data transmission rate. The proposed system can be used as a coding scheme for reliable and high-speed integrated information services of mobile communication systems. Index Terms - Concatenated code, direct-sequence code-division multiple access, trellis-coded modulation.

Antenna tilt angles having a relation to element spacings are among the important radar design parameters. The optimum tilt angles are derived theoretically: four types of uniform and nonuniform linear arrays are considered and Chebyshev array factors are used as a nonuniformly excited array case. Index Terms - Phased-array radar, scanning antennas, tilt angle.