A surrogate-assisted defected ground structure design is proposed to suppress simultaneously E- and H-plane couplings in a 22 microstrip antenna array at 2.45 GHz. The DGS is designed and analyzed based on the magnetic current and mode theory. Machine learning is employed to sweep the DGS parameters within defined limits and fine-tune them to obtain optimal design, predominantly shortening the DGS design time. A 22 microstrip antennas array is used as a test case to corroborate the efficacy of the proposed scheme. Simulation and measurement results show that the proposed DGS can significantly reduce E- and H-plane couplings.

A very small focal-to-diameter (F/D) ratio transmitarray for compact antenna test range (CATR) application is proposed in this article. The transmitarray comprises a feed antenna, a metasurface for phase modulation (MPM), and another one for amplitude modification (MAM). MPM and MAM are implemented using the same metasurface cell but with different cell selections and arrangements. A holistic phase-only design method determines whether the metasurface is for amplitude modification or phase modulation. A CATR collimator with an overall low profile is realized through the joint design of MAM and MPM. The proposed technique overcomes the limits of the ordinary metasurface lenses and enables plane wave generation with a short focal length and sizeable quiet zone. The resulting CATR demonstrates a 50% quiet zone of the aperture size with ±0.5-dB amplitude and ±5° phase errors by full-wave simulation. For further verification, a prototype is fabricated, and its experimental results confirm the simulations.

An array with large element spacing is designed for wide scanning. The element is designed to suppress the grating lobe by combining two radiation modes. The two modes are the $\mathrm{T}{\mathrm{E}_{\boldsymbol{1}\delta 1}}$ mode of a square dielectric resonator antenna (DRA) and the TM ₀₁₁ mode of a monopole. The proper phase and magnitude combine the two modes to achieve the required radiation pattern. The element radiation pattern has an asymmetric radiation pattern with the main beam pointing to the anticipated scanning region and a low radiation level in the region of the expected grating lobe. A linear four-element array with an interelement spacing of 0.95 λ ₀ ( λ ₀ is the operation wavelength) is designed, fabricated, and measured for beam scanning in the E-plane to verify the design concept. The array's grating lobe is reduced by more than 11 dB within the scan angle of 15°–60° and bandwidth of 4.51–5.32 GHz. Good agreements between simulated and measured results are observed.

Throughput modeling in multiple-input multiple-output (MIMO) systems has attracted widespread attentions. Nevertheless, the current throughput model is confined to the case of fixed data streams (layers) and modulation and coding scheme (MCS). In the proposed study, we expand the conventional throughput model based on the transmit selection diversity and threshold translation mapping techniques to enable its use in systems, where the MCS and layers are adaptively modified depending on channel quality. Excellent agreement between the simulation and measurement results confirms the effectiveness and accuracy of the suggested throughput model.

The exploration of Internet-of-things has led to widespread of short-range multiple-input multiple-output (MIMO) communications. However, traditional throughput models, limited by the far-field propagation assumptions, often fail to accurately evaluate the spatial multiplexing capability and throughput performance in short-range line-of-sight (LOS) scenarios. Against this backdrop, this letter reveals the limitations of the conventional plane wave model (PWM) based throughput model from the perspective of effective degree of freedom (EDOF) and develops a MIMO throughput model for short-range LOS scenarios using a spherical wave model (SWM). The relationship between EDOF and throughput is analyzed and discussed. Our results show that EDOF can effectively indicate throughput variations across different transceiver layouts in short-range LOS scenarios. Throughput measurements of MIMO devices are conducted to show the superiority of the proposed SWM-based throughput model to the traditional one.

In multipath environments, multiple-input multiple-output (MIMO) terminals typically suffer from non-zero correlations due to limited handset space and power imbalances due to different antenna efficiencies or partial hand blockage. These antenna–channel impairments can lead to significant throughput performance degradation of MIMO terminals. The multiplexing efficiency was proposed to quantitatively assess this performance degradation. Previous work only derived the analytical expression of the throughput-based multiplexing efficiency of two-port MIMO antennas for user equipment (UE). However, the fifth-generation (5G) UE dictates four or more antennas. In this paper, we extend the multiplexing efficiency metric to high-order MIMO UEs. Both correlation-based channel models and geometry-based stochastic channel models were used for validation. Besides dipole antennas, two representative terminal antennas were also employed for simulation verifications in this work.