A frequency diverse array (FDA) with uniform inter-element frequency offset generates an “S-shaped” beam pattern with maxima at multiple range and angle values. This property allows a number of reflectors positioned at any of the maxima to interfere with the target-returns, thus weakening the signal-to-interference-plus-noise ratio. In this letter, a uniformly spaced symmetric FDA with Hamming window-based tapering interelement frequency offsets has been proposed. The proposed design produces a single maximum beam pattern toward the desired range and angle values. This approach is mathematically analyzed and verified by numerical results. Moreover, it outperforms the existing forms of FDA with uniform interelement offset, e.g., conventional FDA, as well as the FDA with nonuniform interelement offset, e.g., Log-FDA in terms of side-lobe suppression and transmit energy focusing.

Electronic beam steering with greater efficiency is a vibrant feature of a phased array antenna, but for all the range cells, it is fixed at a specific angle. To mitigate this problem, frequency diverse array (FDA) antenna was proposed. This study presents a review on the development of FDA technology in radar and navigation applications. FDA is different from a conventional phased array antenna radar in a sense that it uses a small frequency offset across the array, which helps to generate a range, angle and time‐dependent beam pattern. This pattern assures the energy transmission towards the desired angle and range cell. In addition, this study also focuses the research on getting range‐angle uncoupled beam patterns along with diverse hybrid cognitive FDA design, available in the literature, for improved radar performance.

Frequency diverse array (FDA) radar has been investigated in recent years to provide range-dependent as well as angle-dependent beamforming. The problem of multiple maxima at different ranges due to periodicity of FDA beampattern has been mitigated by using an FDA radar with logarithmic offset (log-FDA). This idea has achieved single maxima for a target in the desired range dimension. In this letter, we have proposed multiple-input-multiple-output frequency diverse array radar with logarithmic offset (MIMO-log-FDA), which can be used to produce single maxima for multiple targets present in different range bins. Using range bins concept along with logarithmic offset in each subarray of MIMO-FDA has not only allowed us to produce single maxima for each target in a particular range bin, but also to minimize the reflections from any other target. Simulation and results have verified the effectiveness of proposed scheme.

Since frequency diverse array multiple-input multiple-output (FDA-MIMO) radar possesses additional target range information for potential performance improvement, this article studies adaptive distributed targets detection for FDA-MIMO radar, where the targets are embedded in Gaussian clutter with unknown covariance matrix. The proposed FDA-MIMO radar detection model considers also the distributed targets occupying several secondary range cells, which is different from the classic detection models in multiple-input multiple-output (MIMO) and/or phase array (PA) radars that discuss only point-like targets. By exploiting the FDA-MIMO radar framework for distributed target detection, we propose the detector through a two-step generalized likelihood ratio test criteria without the need of training data and/or a priori covariance matrix. Moreover, closed-form expressions for the probability of false alarm and detection probability are derived, respectively. The proposed detector adheres to the property of a constant false alarm rate because its probability of false alarm is not restricted by the covariance matrix. The proposed method together with all theoretical analysis are verified by numerical results.

In this letter, we explore time-modulated frequency diverse multiple-input multiple-output (TMFD-MIMO) array for integrated radar and communications, where the communication information bits are embedded via spread sequence technique during each radar pulse. Orthogonal waveforms are adopted in the TMFD-MIMO array for radar functionality, and a switching time-modulation scheme is applied according to the information bits (i.e., binary phase shift keying) associated spreading sequences. Thus, the number of embedded information bits during each radar pulse equals the number of spread sequences. In doing so, the communication receiver interprets the bits associated with a particular waveform as binary information with prior knowledge of the spread sequences. While compared to existing radar-communications, the achievable data rate is then proportionally increased with the pulse repetition frequency, spreading sequence and size of the BPSK constellation. Moreover, satisfactory probability of target resolution and signal to interference plus noise ratio for radar functionality and symbol error rate for communication functionality are achieved.

This paper deals with the problem of adaptive moving target detection, embedded in homogeneous Gaussian noise with unknown covariance matrix, for frequency diverse array multiple-input multiple-output (FDA-MIMO) radar operating in interference-dominant environment. Unlike traditional adaptive moving target detectors that need training data to estimate the jamming covariance matrix (JCM), we present the Rao and Wald test based adaptive detector, which requires no training data. Furthermore, we proposed a two-stage approach to obtain maximum likelihood estimate (MLE) of the joint range, angle and Doppler, respectively. The corresponding signal-to-jamming-plus-noise ratio (SJNR) is derived to evaluate the FDA-MIMO radar performance. All proposed methods are validated by numerical results, which show that the proposed detector outperforms the existing generalized likelihood ratio test (GLRT).