In recent years, frequency diverse array (FDA) radar with uniform interelement frequency offset has been proposed and investigated. It has been shown that the beampattern of this form of radar is range-angle-dependent, and it exhibits maxima at multiple range values. Due to the multiple maxima, a number of reflectors located at any of the maxima can interfere the target-return, thus deteriorating signal-to-interference-plus-noise ratio (SINR). In this letter, we have proposed FDA with logarithmically increasing frequency offset to achieve a beampattern with a single maximum at the target location. A transmitter for the proposed radar system has been described and analyzed mathematically. Furthermore, the transmit beampattern has been derived and plotted and compared to that of phased-array radar (PAR) and the existing forms of FDA employing uniform frequency offset.

In recent years, frequency diverse array radar with fixed frequency offset has been proposed and investigated. It has been shown that the beampattern of this category of radar is time-dependent as well as range-angle-dependent. In this letter, we have proposed time-dependent frequency offset to achieve a beampattern that is time-independent for a given pair of range and angle. The proposed radar system has been analyzed mathematically, and the simulation results are presented. Simulations show that the beampattern does not change with time for a particular range-angle pair, but it remains time-dependent for other values of range and angle. With the proposed radar system, the target remains illuminated constantly for the whole pulse duration, causing a high-energy reflection that can increase detectability of the target.

Frequency Diverse Array (FDA) radar has recently gained substantial interest among the researchers due to its unique range-angle-dependent beampattern in contrast to angle-dependent beampattern of phased-array radar. In the simplest form of FDA radar, a uniform inter-element frequency offset is applied across the aperture of uniform linear array of sensors. This offset may be small as compared to the carrier frequency or large, giving rise to different advantages. To investigate the range and Doppler resolution of a radar system, ambiguity function has been a traditional and effective tool. In this letter, the ambiguity function of FDA radar with small frequency offset has been formulated, and some important properties of the ambiguity function have been derived. These properties can help compare its performance with the other forms of radar.

A split-aperture array (SAA) is an array of sensors or antenna elements in which the array is split into two or more sub-arrays (SAs). Recently proposed SAAs, namely coprime and semi-coprime arrays, offer to attain a small half-power beamwidth (HPBW) with a small number of elements, compared to most conventional unified-aperture arrays, at the cost of reduced peak-to-side-lobe ratio (PSLR). To reduce HPBW and increase PSLR, non-uniform inter-element spacing and excitation amplitudes have proven helpful. However, all the existing arrays and beam-formers suffer increased HPBW, degraded PSLR or both when the main beam is steered away from the broadside. In this paper, we propose staggered beam-steering of SAs, a novel technique for decreasing HPBW. In this technique, we steer the main beams of the SAs of a semi-coprime array to angles slightly different from the desired steering angle. In conjunction with staggered beam-steering of SAs, we have utilized Chebyshev weights to suppress the side lobes. The results show that the beam-widening effect of Chebyshev weights can be mitigated considerably by staggered beam-steering of the SAs. Ultimately, the unified beam-pattern of the whole array offers HPBW and PSLR better than the existing SAAs, uniform and non-uniform linear arrays, especially when the desired steering angle is away from the broadside direction.

In this paper, an artificial neural network (ANN) has been proposed to estimate the required values of the adjustable parameters of a Semi-Coprime array with staggered steering (SCASS), which was proposed recently. By adjusting the amount of staggering and the sidelobe attenuation (SLA) factor of Chebyshev weights, SCASS can promise a quite small half-power beamwidth (HPBW) and a high peak-to-side-lobe ratio (PLSR), even when the beam is steered away from broadside direction. However, HPBW and PSLR cannot be improved simultaneously. There is always a trade-off between the two performance metrics. Therefore, in this paper, a mechanism has been introduced to minimize HPBW for a desired PSLR. The proposed ANN takes the array of architectural parameters, the required steering angle, and the desired performance metric, i.e., PSLR, as input and suggests the values of the adjustable parameters, which can promise the minimum HPBW for the desired PSLR and steering angle. To train the ANN, we have developed a dataset in Matlab by calculating HPBW and PSLR from the beampattern generated for a large number of combinations of all the variable parameters. It has been shown in this work that the trained ANN can suggest the optimum values of the adjustable parameters that promise the minimum HPBW for the given steering angle, PSLR, and array architectural parameters. The trained ANN can suggest the required adjustable parameters for the desired performance with mean absolute error within just 0.83%.