A mixed phased array and retrodirective array providing auto tracking of the angular position of the unmanned aerial vehicle (UAV) is presented. The phase conjugation technique and complex vector multiplication are used together to find the geometric phase of each channel canceling the need to use direction finding algorithm (DOA). After generating the phase conjugated version of the received signal on each channel, its complex vector representation will be multiplied by the complex vector representation of the received signal on the reference channel. The UAV will stay on the beak of the array factor during its movement within the field of view (FOV), and a permanent high gain data link is obtained without the need of the tracking algorithm. The beamwidth of the resulted array is widened to be equal to the FOV. The computational cost of the tracking system will be reduced due to canceling the need of using the complex processing algorithms (DOA, and tracking) used in smart antenna. Direction finding algorithm, beamforming algorithm, and tracking algorithm are combined in one algorithm. The least square error pattern synthesis with nulls method is used to eliminate the predefined interference signals and add null steering ability to the resulted array. The effect of the phase errors is reduced to the case of single antenna due to including the phase errors of each channel in its complex weights. The beam pointing error is taken as a metric to evaluate the performance of the resulted array compared with the BPE of a phased array using the monopulse tracking method.
An improved mixed phased/retrodirective array is presented. The phase conjugation technique will be achieved in base band instead of intermediate frequency (IF) band. Canceling the need to the intermediate frequency stage in the receiver will reduce the complexity and cost of the system. The ability to entire processing of the tracking array function to be applied using software defined radio (SDR) system is added. The effect of the phase errors at each channel is compensated, and the noise performance of the tracking array is improved. Also an expanded analytical study of the noise performance of the array to include the impact of the phase errors on the array performance is presented. The proposed equivalent one-channel model of the N-channel array model provides a clear and efficient way to characterize the noise performance of array receiver systems with any amplitude tapering and also considering the phase errors. The improvement provided by the mixed phased/retrodirective array compared to the traditional phased array is evaluated. The effect of array size on the tracking array performance in the presence of phase error is discussed. A monopulse tracking array is taken as an example.
Successfully achieving the mission of the unmanned aerial vehicle (UAV) requiring a high gain data link between the UAV and the ground control station (GCS). The antenna of the ground station must has a narrow, precisely guided beam towards the UAV. Widening the beamwidth in phased array will be on the expense of reducing the gain and increasing the possibility of receiving the interference signal, this may lead to the failure in achieving the desired link. This paper presents a new method to achieve an automatic forming of the reception beam and automatic tracking of the UAV’s signal in the digital phased array without the need of the complex digital signal processing algorithms used in smart antenna. The proposed approach is based on the complex vector multiplication and phase conjugation technique. The UAV will stay on the beak of the array factor. The resulted array is a combination between retrodirective array and phased array, with beamwidth equal to the field of view without reducing the gain and with null steering ability.
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