Frequency Diverse Array Radar Research Articles

Transmit Subaperturing for Range and Angle Estimation in Frequency Diverse Array Radar

Different from conventional phased-array, which provides only angle-dependent beampattern, frequency diverse array (FDA) employs a small frequency increment across the antenna elements and results in a range-angle-dependent beampattern. This beampattern offers a potential to localize the targets in two dimensions in terms of slant ranges and azimuth angles. However, it is difficult to obtain the target location information from a standard FDA radar due to the couplings in range and angle responses. In this paper, we propose a transmit subaperturing scheme on the FDA radar for range and angle estimation of targets. The essence is to divide the FDA elements into multiple subarrays and optimize the transmit beamspace matrix with the use of convex optimization. We also discuss several practical issues for designing the FDA radar system parameters. Since the subarrays offer decoupled range and angle responses, the targets can be located using the beamspace-based multiple signal classification algorithm. The range and angle estimation performance is evaluated by comparing with the Cramer-Rao lower bound.

Study on Space-time Character of Clutter for Forward-looking Frequency Diverse Array Radar

Study on Space-time Character of Clutter for Forward-looking Frequency Diverse Array Radar

Range-Angle Localization of Targets by A Double-Pulse Frequency Diverse Array Radar

Phased-array radar is widely used in localizating non-cooperative targets, but the range and angle of targets cannot be directly estimated from its beamforming output due to an inherent range ambiguity, i.e., two-dimensional localization of non- cooperative targets cannot be obtained directly from conventional linear phased-array radar beamforming peaks. This paper proposes a simple range-angle localization of targets by uniform linear array (ULA) double-pulse frequency diverse array (FDA) radar. The FDA transmits two pulses with zero and non-zero frequency increments, respectively. The azimuth angle and slant range of targets are then estimated directly from the beamforming output peaks. This approach can be interpreted as detecting the targets in angle dimension and then localizing them in range dimension by properly choosing the frequency increment. Moreover, multiple FDA radars can work as netted radar networks, in which distinct frequency increments or orthogonal waveforms are employed. The localization performance is examined by analyzing the Cramér-Rao lower bound (CRLB) and numerical mean square error (MSE). The effectiveness is demonstrated by simulation results.

Frequency Diverse Array Radar Cramér-Rao Lower Bounds for Estimating Direction, Range, and Velocity

Different from phased-array radar, frequency diverse array (FDA) radar offers range-dependent beampattern and thus provides new application potentials. But there is a fundamental question: what estimation performance can achieve for an FDA radar? In this paper, we derive FDA radar Cramér-Rao lower bounds (CRLBs) for estimating direction, range (time delay), and velocity (Doppler shift). Two different data models including pre- and postmatched filtering are investigated separately. As the FDA radar has range-angle coupling, we use a simple transmit subaperturing strategy which divides the whole array into two subarrays, each uses a distinct frequency increment. Assuming temporally white Gaussian noise and linear frequency modulated transmit signal, extensive simulation examples are performed. When compared to conventional phased-array radar, FDA can yield better CRLBs for estimating the direction, range, and velocity. Moreover, the impacts of the element number and frequency increment are also analyzed. Simulation results show that the CRLBs decrease with the increase of the elements number and frequency increment.

Adaptive Frequency Offset Selection in Frequency Diverse Array Radar

Frequency diverse array (FDA) can provide a range-angle-dependent beam that can be controlled by using a frequency increment between adjacent elements, but the frequency increment is fixed in a basic FDA, which restraints the performance improvement in different environments significantly. In this letter, we propose an adaptive frequency offset selection scheme to control the transmit beam direction by choosing the frequency offset adaptively. In doing so, we design the frequency increment of transmit signal in each step by maximizing the output signal-to-interference-plus-noise ratio (SINR) criteria. Our proposal can adaptively adjust the beam direction to match the current target angle and range sector. The effectiveness of the proposed scheme is verified by simulation results.

Frequency Diverse Array Radar With Time-Dependent 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.