Adaptive beamforming is used in many applications such as radar, sonar and wireless communications for separating desired signals from other unwanted signals. Beamforming is essentially applied to direct the pattern of the receiving antenna system towards the desired direction as well as to attenuate the received signals from unwanted directions. The process of adaptive beamforming is performed in two steps. The first step is assigned to estimate the direction of arrival of signals at the field of view of the receiving system. The second step is assigned to nullify the beam pattern in the directions of unwanted signals. To improve the performance of the adaptive beamforming, the number of array elements as well as the number of snapshots should be increased. However, this increase in both numbers of elements and snapshots leads to increase in the cost and the processing time. In this paper, a proposed iterative adaptive digital beamforming technique is presented to improve the array capability of interference cancellation while reducing the processing time. The proposed technique is based on the Jacobi theorem for iterative solution of a system of linear equation to determine the optimum weight vector at the array output. The proposed technique is compared with the optimal Minimum Variance Distortionless Response (MVDR) beamformer technique. Computer simulation is applied to verify the mathematical analysis that presented in the paper. The paper results show that the proposed technique can provide effective Co-Channel Interference (CCI) suppression better than MVDR, while increasing the strength of the desired signal.

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This paper characterizes the performance of direct sequence spread spectrum (DS-SS) signals from the detection probability point of view. The detection probability of DS-SS signals is estimated using wideband radiometer receiver over flat fading channel. Simulations are performed to evaluate detection probability of DS-SS signals over flat fading channel for various time bandwidth product values. The results are compared with the detection probability of DS-SS signals over AWGN channel. The results show that the fading parameter degrades the detection probability of DS-SS signals. The performance of DS will be discussed later in the presence of imperfect channel estimation errors.

The two-dimensional filtering approach often referred to as space-time processing, (STP) has been the subject of considerable research interest over the past two decades. The space-time processing (STP) is a crucial technique for the new generation airborne radar with high air-toground performance. Slowly moving ground targets produce a reflected signals which could not be distinguish from the surrounding clutter reflections, The results in either space processing, (adaptive array) or temporal processing, (MTI) will be miss detection of the desired target which has Doppler frequency and angle of arrival near to that ones of the clutter. Moreover ground based jammers could produce a wide frequency spread jamming signal with relatively high power to confuse airborne radars. However STP could significantly reduces the effects of both the clutter and jammers.

Radar electronic support measures (ESM) systems perform the functions of threat detection and area surveillance to determine the identity and bearing of surrounding radar emitters . These ESM receivers have a wide frequency band and their antennas have a wide coverage pattern. These features of the ESM reeQiver are necessary to increase the instantaneous coverage and to enhance the probability of in:terception. However , the ESM receiver is vulnerable to overlapping pulses, these pulses which tyrrive simultaneously or partially are time overlapped to the ESM receiver input In this work a quelling model is performed to describe the arrival process of radar pulses at the input of an TESM receiver. From this arrival model, the probability of pulse overlapping is determined. for an arbitrary arrival rate . The effect of this undesired pulse overlapping on the measurements performed by an ESM receiver and consequently the output digital words that describe the arrival pulse train is evaluated in two cases. The first case which is denoted as paraPyzable receiver type , where the ESM receiver can only process a pulse which arrives after a fix(ed time from the last pulse processed. The second case is denoted as non paralyzable receiver, where the receiver is ready to process a new :wise, as soot as the life time of the previous pulse is expired . A computer program is constructed to simulate the operation of an ESM receiver in these two cases . The results show that the ratio of successfully processed pulses in case of non paralyzable processing is larger than the case of a paralyzable processing .