No abstract

Multi-band antennas have received significant interest because they can support multiple wireless communication services with a single antenna. However, an array antenna consisting of these element antennas can suffer from non-periodic arrangement due to the irregular sizes of the elements. In this paper, various shapes of patch antennas with fractal antennas are used to ensure the periodic arrangement of the array antenna, and antenna array incorporated with a feed network is proposed. Four different antenna arrays operating at 2.45/3.7/4.3/5.0 GHz are aggregated in an antenna with interleaved disposition of the different element antennas. It is observed that mutual couplings between two elements are sufficiently low, at less than −23 dB. Peak antenna gain ranging from 11.1 dBi to 14.4 dBi at the four different bands is obtained.

This study introduces a new scheme for resolving the ambiguity in a pulse‐Doppler radar. While ambiguity resolution is typically performed before tracking, the proposed approach, Track‐Before‐Resolving, is resolving ambiguity utilising tracking filters. A specific Doppler ambiguity resolution algorithm is provided for demonstrating that the Track‐Before‐Resolving method is useful. In order to resolve the ambiguity, which is equivalent to finding the ambiguity number, this algorithm investigates the maximum probability calculated in the multiple model estimation, each with a tracking filter of a different ambiguity number. Simulation shows that the proposed algorithm performs effectively, even at low SNR.

Multiple-input multiple-output (MIMO) technology has recently attracted attention with regard to improving the angular resolution of small antennas such as automotive radars. If appropriately placed, the co-located transmit and receive arrays can make a large virtual aperture. This paper proposes a new method for designing arrays by adopting a structure with minimum redundancy. The proposed structure can significantly increase the virtual array aperture while keeping the transmit and receive antennas at the same size. We describe the application of the proposed method to subarray-type antennas using multi-channel transceivers, which is essential for arranging RF hardware in a small antenna operating at high frequency. Further, we present an analysis of the final beam pattern and discuss its benefits and limitations.

Noise radar has become attractive owing to progress in hardware technology. Aside from the low probability of exploitation, the use of noise waveform is likely to grow due to its low interference features, especially in circumstances where multiple radars operate in the same band. In this study, we developed and tested a wideband noise radar for a ground-moving vehicle. It operates in the X-band with an instantaneous bandwidth of 1.5 GHz. The true time delay (TTD) was applied to correct the distortion of the beam pattern by the wide bandwidth, and the correlators were implemented by high-speed parallel processing using a field programmable gate array (FPGA). The outdoor experimental results were presented.