Millimeter-Wave Near-Field-Focused Full 2-D Frequency Scanning Antenna Array With Height-Modulated-Ridge Waveguide

A millimeter-wave near-field-focused (NFF) full 2-D frequency-scanning antenna array is presented in this article. The proposed antenna is achieved by combining an NFF ridged-waveguide slot array with a double-layer folded focused progressive feeding network. The linear ridged-waveguide slot array antenna is designed with a height-modulated ridge to focus on the power in one direction. The folded feeding line with different length is used to generate the desired focused phase and frequency-dependent progressive phase shift in the other direction. In this case, as the working frequency is swept in the considered range, the inherent frequency-dependent behavior of the linear NFF leaky-wave antenna (LWA) allows a single-scanning sweep in one direction, whereas the focused progressive feeding network ensures multiple-scanning sweeps in the other direction. A full 2-D electronic scanning with no coverage blindness in the scanning area is achieved. To the best of our knowledge, the proposed NFF antenna array is the first design to achieve the full 2-D scanning focus in the near-field (NF) region only by sweeping the frequency, which means that the testing information in the NF region can be directly obtained with a certain band of frequency. This type of antenna is a good candidate in NF fast-scanning applications, e.g., electromagnetic imaging/detecting systems.