Frequency diverse array (FDA) radar has been studied by many researchers due to the range-angle dependent beampattern which is different from the conventional phased array radar. However, the contribution of previous studies has received little attention within the circular frequency diverse array radar and no known empirical research has focused on investigating the three-dimensional (3D) parameter estimation (azimuth, elevation, and range). In this paper, we proposed a two-stage estimation algorithm for 3D parameter estimation of uniform circular frequency diverse array (UC-FDA) radar and firstly demonstrate the capability and performance of 3D parameter estimation. The first step of the two-stage estimation is the estimation of azimuth and elevation from the beamspace which is transformed from the element space by the beamformer. The second step is to substitute the angle obtained in the first step into the transmitting steering matrix for the range estimation. Cramér-Rao bound (CRB) that is used to evaluate the 3D parameter estimation performance is derived to compare. Theoretical analysis and numerical simulation demonstrate that the UC-FDA radar has superior 3D parameter estimation performance and the effectiveness of the proposed two-stage estimation algorithm. The research findings can contribute to a better 3D localization method and represent an additional step towards developing multi-dimensional localization and interference suppression for UC-FDA radar.

Frequency diverse array (FDA) radar have attracted great interests due to the range-angle-dependent transmit beampattern which is different from phased array radar providing only angle-dependent transmit beampattern. In this paper, we firstly proposed a receiver processing strategy based on signal separation method which eliminates the need for employing a bank of bandpass filters at the receiver of FDA radar. In the proposed separation scheme, the received signal at each receiving element was separated into M channels, where M represents the transmitting element number. After time-invariant processing of the separated signal, the angle and range were estimated by two-stage multiple signal classification (MUSIC) algorithm. For velocity estimation, we proposed a novel unambiguous velocity estimation algorithm. This novel algorithm was implemented to calculate the phase of each element and then the differential phase within the adjacent elements is calculated. The velocity of the target was estimated by the differential phase. This mechanism for extending the Nyquist velocity range is that the differential phase of the two adjacent channels has a much smaller variance than the individual channel phase estimated. All estimated parameter performance is verified by analyzing the Cramér-Rao lower bound (CRLB) and the root mean square errors (RMSE).

Frequency diverse array (FDA) radar with non-uniform frequency increasing offset is the most potent method to decouple the range-angle dependent beampattern and form a dot-shaped beampattern. However, little known empirical research has focused on the joint range-angle estimation of FDA radar with non-uniform frequency offset. The aim of this letter is to investigate a decoupling model and propose a range-angle estimation algorithm of FDA radar with uniform or non-uniform frequency offset. First, the blind source separation algorithm is performed to process the observation signal and obtain the separation matrix. Then, the array manifold matrix of observation signal is estimated by separation matrix correction. Next, a decoupling model is formulated to separate the range and angle component from the estimated array manifold matrix. Finally, an independent range and angle estimation algorithm via pulse-pair technique is developed. The numerical simulations are performed to indicate the effectiveness and superior performance.

Velocity ambiguity is one of the main challenges in accurately measuring velocity for the future Geostationary Spaceborne Doppler Weather Radar (GSDWR) due to its short wavelength. The aim of this work was to provide a novel velocity dealiasing method for frequency diversity for the future implementation of GSDWR. Two different carrier frequencies were transmitted on the adjacent pulse-pair and the order of the pulse-pair was exchanged during the transmission of the next pulse-pair. The Doppler phase shift between these two adjacent pulses was estimated based on the technique of the frequency diversity pulse-pair (FDPP), and Doppler velocity was estimated on the sum of the Doppler phase within the adjacent pulse repetition time (PRT). From the theoretical result, the maximum unambiguous velocity estimated by FDPP is only decided by the interval time of the two adjacent pulses and radar wavelength. An echo signal model on frequency diversity was established to simulate echo signals of the GSDWR to verify the extension of the maximum unambiguous velocity and the accuracy of the velocity estimation for FDPP used on GSDWR. The study demonstrates that the FDPP algorithm can extend the maximum unambiguous velocity greater than the Stagger PRT method and the unambiguous range and velocity are no longer limited by the chosen value of pulse repetition frequency (PRF). In the Ka band, the maximum unambiguous velocity can be extended to 105 m/s when the interval time is 10 μs and most velocity estimation biases are less than 0.5 m/s.