Millimeter-wave and terahertz integrated circuits and chips are expected to serve as the backbone for future wireless networks and high resolution sensing. However, design of these integrated circuits and chips can be quite complex, requiring years of human expertise, careful tailoring of hand crafted circuit topologies and co-design with parameterized and pre-selected templates of electromagnetic structures. These structures (radiative and non-radiative, single-port and multi-ports) are subsequently optimized through ad-hoc methods and parameter sweeps. Such bottom-up approaches with pre-selected regular topologies also fundamentally limit the design space. Here, we demonstrate a universal inverse design approach for arbitrary-shaped complex multi-port electromagnetic structures with designer radiative and scattering properties, co-designed with active circuits. To allow such universalization, we employ deep learning based models, and demonstrate synthesis with several examples of complex mm-Wave passive structures and end-to-end integrated mm-Wave broadband circuits. The presented inverse design methodology, that produces the designs in minutes, can be transformative in opening up a new, previously inaccessible design space.

A dual-band differential shifted-feed microstrip grid array antenna (DSF-MGAA) with two parasitic patches is presented in this communication. By moving the feed location, a conventional MGAA (C-MGAA) can be turned into a SF-MGAA for dual-band operation. The high-frequency band of SF-MGAA corresponds to the operation mode of the C-MGAA, and its low-frequency band is similar to that of the patch or meshed patch antenna. A new differential feeding scheme and two parasitic patches are adopted to improve the impedance bandwidth of SF-MGAA. The proposed DSF-MGAA can cover a dual-band of 3.7 and 28.5 GHz. The measured -10 dB impedance bandwidths of 3.4% and 4.5%, which correspond to the peak gains of 8.98 and 19.2 dBi, are obtained in the low-and high-frequency bands, respectively. The DSF-MGAA can be a potential candidate for the future dual-band wireless communication.

A new approach for the design of wideband multilayer stacked patch antennas is proposed based on bat algorithm (BA). Differential topology is described for normal multilayer stacked patch antennas to achieve stable and symmetry radiation patterns as well as high cross-polarization suppression within the design band. Fabricated antenna prototypes show 25.5% and 34.9% impedance bandwidth for the two-layer and three-layer design, respectively. Measured results validated the design.

In this communication, a compact wideband dual-decoupling technique is proposed for wideband microstrip patch antennas (WMPAs) at the X-band. The wideband decoupling property is achieved by integrating the defected ground structure (DGS) and the coplanar inductance (CI) on the ground plane and patch layer, respectively. To validate the feasibility of the proposed method, both the aperture-coupled and probe-fed WMPAs with the proposed novel decoupling scheme are simulated, fabricated, and measured, respectively. An equivalent circuit and characteristic mode analysis (CMA) of this wideband decoupling scheme are developed to provide physical insight succinctly. Experimental results demonstrate that the poor isolation of the two proposed antennas has been improved from 6 dB to better than 20 dB with an extremely close edge-to-edge distance of 1 mm ( $0.033 \lambda _{0}$ ). The achieved decoupled bandwidths (BWs) are up to 17.6% and 22.2% for the aperture-coupled and probe-fed schemes, respectively. In addition, the proposed method has been extended to the decoupling of multielement antenna arrays, demonstrating its potential for large-scale wideband massive multiple-input and multiple-out (MIMO) applications.

The modification of a conventional single-ended microstrip planar inverted F antenna (SE-PIFA) into a novel differentially-driven microstrip planar inverted F antenna (DD-PIFA) and the comparison of their performances are first made. It will be shown that the DD-PIFA provides better performance than the SE-PIFA does. Then the frequency trimming and more importantly the miniaturization of the DD-PIFA are described. A simple formula for determining the resonant frequency of a DD-PIFA is given. Calculated, simulated and measured results at 2.45 GHz are discussed, indicating the potential applications of the DD-PIFA in highlevel integration of radio transceivers for wireless communication systems.

A new method to miniaturize patch antennas is presented by using coupled microstrip patches. A design example is given at 8.45 GHz. The resultant patch antenna has an electrical size of 0.146 × 0.146 × 0.04 λ ₀ ³ , which is about 60% area reduction with respect to a conventional patch antenna. The miniaturized patch antenna shows similar broadside radiation patterns and a lower cross-polarization level as compared with the conventional one. It exhibits a realized gain of 5.4 dBi with the half-power beamwidths of 107° in the E-plane and 87° in the H-plane, respectively. Both simulated and measured results demonstrate that the miniaturized patch antenna exhibits excellent impedance and radiation characteristics and is a promising candidate for highly integrated wireless systems.