W band is a part of the electromagnetic spectrum that ranges from (75–110 GHz) and has a wide variety of applications, including long-range, high-resolution radars, sensors, and nondestructive imaging due to their low atmospheric absorption, short wavelength, and wide available frequency bandwidth. Due to their small size aperture, microstrip antennas have been a promising candidate for RADAR applications. At W band, MIMO RADAR is an excellent alternative to stream data at the same time continuously. Multiple Input Multiple Output (MIMO) RADAR provides the advantage of streaming various datasets simultaneously. Concurrently, operating such a system at millimeter-wave (mm-wave) implies a significant reduction in the size of RF circuitry. A major drawback is the mutual coupling between antenna elements. We present an mm-wave MIMO system operating at 78GHz with an integrated bandstop filter (BSF) to improve isolation between antenna elements. Simulations show that the filter leads to a 27dB reduction in mutual coupling without impacting the radiation pattern. W band imaging has also been extensively studied due to its high-resolution capability. There are lots of research going on in this field. A W band array will be simulated for an imaging application. A 20 dBi gain is achieved for an eight-by-eight array. Then, a compact dual-frequency (78/95 GHz) microstrip patch antenna with a novel design is proposed, combining RADAR and imaging applications. The proposed antenna is composed of two electromagnetically coupled patches. The first patch is directly fed through a grounded co-planar waveguide (GCPW) and is mainly responsible for the lower band’s radiation (78 GHz). The second patch is provided through capacitive coupling from the first patch and is primarily accountable for radiation in the upper-frequency band (95 GHz). The GCPW configuration is chosen to ensure the planar arrangement. Numerical and experimental results show good performance regarding return loss, bandwidth, radiation patterns, and realized gain. The impedance-matching bandwidths achieved in the 78 GHz and 95 GHz bands are about 2 GHz and 9 GHz, respectively. The minimum value of the return loss is -24 dB for the 78 GHz bands and -18dB for the 95 GHz bands. The surface current distribution is demonstrated to understand independent resonance at both frequencies. Radiation patterns are directional for both bands, which makes the proposed single antenna an excellent candidate for both applications. Finally, an array of both bands is designed to achieve higher gain for long-distance RADAR and imaging applications such as disaster or war zone.
