One of the key enablers of future wireless communications is constituted by massive multiple-input multiple-output (MIMO) systems, which can improve the spectral efficiency by orders of magnitude. In existing massive MIMO systems, however, conventional phased arrays are used for beamforming. This method results in excessive power consumption and high hardware costs. Recently, reconfigurable intelligent surface (RIS) has been considered as one of the revolutionary technologies to enable energy-efficient and smart wireless communications, which is a two-dimensional structure with a large number of passive elements. In this paper, we develop a new type of high-gain yet low-cost RIS that bears 256 elements. The proposed RIS combines the functions of phase shift and radiation together on an electromagnetic surface, where positive intrinsic-negative (PIN) diodes are used to realize 2-bit phase shifting for beamforming. This radical design forms the basis for the world's first wireless communication prototype using RIS having 256 two-bit elements. The prototype consists of modular hardware and flexible software that encompass the following: the hosts for parameter setting and data exchange, the universal software radio peripherals (USRPs) for baseband and radio frequency (RF) signal processing, as well as the RIS for signal transmission and reception. Our performance evaluation confirms the feasibility and efficiency of RISs in wireless communications. We show that, at 2.3 GHz, the proposed RIS can achieve a 21.7 dBi antenna gain. At the millimeter wave (mmWave) frequency, that is, 28.5 GHz, it attains a 19.1 dBi antenna gain. Furthermore, it has been shown that the RIS-based wireless communication prototype developed is capable of significantly reducing the power consumption.

Reconfigurable Intelligent Surface-Based Wireless Communications: Antenna Design, Prototyping, and Experimental Results

Antenna is one of the key components onboard small satellites as its design determines the performance of all the wireless systems including telemetry, tracking and control, high-speed data downlink, navigation, intersatellite communications, intrasatellite communications, wireless power transfer, radars and sensors, etc. This paper presents a review of recent development in advanced antennas for small satellites (MiniSat, MicroSat, NanoSat, CubeSat, etc.). A number of recent examples of antennas for small satellite applications are shown and discussed. A conclusion and future development in antennas for small satellites are given in the end.

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Advanced Antennas for Small Satellites

Pattern-reconfigurable antennas with multiple switchable beams, especially with both boresight and endfire directions, are highly desired for wireless communications. In this letter, a novel pattern-reconfigurable antenna is proposed that provides an efficient solution. By reconfiguring parasitic striplines placed around a radiating dipole and reflecting metal pieces under the dipole using p-i-n diodes, the antenna main beam can be switched to five directions in the elevation plane, approximately from $-90^{\circ }$ (left endfire), $-45^{\circ }$ , 0 $^{\circ }$ (boresight), $+45^{\circ }$ , to $+90^{\circ }$ (right endfire). The proposed antenna operates at 2.45 GHz with dimensions of about 0.57 $\lambda$ $\times\, 0.45\lambda$ $\times\, 0.28\lambda$ . An antenna prototype is fabricated and measured. For all five directional beams, the measured $|S_{11}|$ values are below $-$ 13 dB, and the measured realized gains range from 5.2 to 6.5 dBi. They agree reasonably well with the simulated ones.

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Pattern-Reconfigurable Antenna With Five Switchable Beams in Elevation Plane

Low sidelobe longitudinal slot array antennas are investigated based on substrate integrated waveguide (SIW) technology. The design method consists of the characterisation of the radiating element, the synthesis of the linear array and the development of the planar array including a feeding power divider by performing full-wave electromagnetic simulations for the final accurate design. Two planar slot array antennas are fabricated with a normal printed circuit board (PCB) process. Low sidelobe features are verified by the measured results which are in agreement with the simulated results. For an 8 times 8 SIW slot array antenna, the measured sidelobe levels (SLLs) are below -36 dB in the H-plane and below -25 dB in the E-plane with the Gain of 20.3 dB at 9.9 GHz. And for a 16 times 16 antenna, the SLLs are below -30 dB both in the E-plane and H-plane with the Gain of 24.4 dB at 10 GHz. The achieved design goals on the radiation patterns therefore validate the proposed low sidelobe SIW slot array antennas to be valuable candidates for high performance communication and radar applications.

Design and implementation of low sidelobe substrate integrated waveguide longitudinal slot array antennas

This article presents a low-cost, high-efficiency, and full-metal reflectarray (RA) antenna with mechanical beam-steerable capabilities. A unit cell (UC) implemented by a metal cylinder with a cuboid-shaped notch is proposed to achieve a 1 bit reflection phase (0 and $\pi $ ) for the transverse electric (TE) and transverse magnetic (TM) normal incidence waves. The proposed UCs can be employed to construct an RA antenna with 2-D beam-steerable abilities. For demonstration, the RA antennas with six different beam directions are presented as examples, by simply adjusting the rotations of the UCs. The impedance matches of the RA antenna are all below −10 dB from 22 to 33 GHz, and the measured radiation patterns of the RA antenna are all highly consistent with the simulated counterparts for the six different beam direction scenarios. A 1.5 dB gain drop bandwidth of approximately 20% from 24.7 to 30 GHz and a peak realized gain of 18.9 dBi at 26 GHz are experimentally obtained for the RA antenna with radiation patterns at broadside. Compared to the substrate-based UCs loaded with p-i-n diodes, the proposed UCs have full-metal structures without using any active RF components and dielectric substrates, leading to the high total efficiency of the proposed RA antenna. Due to the low-cost, high-efficiency, and high-power handling properties, the proposed RA antenna can provide a fixed or scanning beam and is a good candidate for 5G millimeter-wave communication applications.

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A Low-Cost, High-Efficiency and Full-Metal Reflectarray Antenna With Mechanically 2-D Beam-Steerable Capabilities for 5G Applications

Waveguide slot antennas integrated on microwave laminate are presented, and single and dual slot antennas are described, which operate at 10 GHz.

Integrated waveguide slot antennas

Reconfigurable reflectarray antennas operating in Ku-band are presented in this paper. First, a novel multilayer unit-cell based on polarization turning concept is proposed to achieve the single-bit phase shift required for reconfigurable reflectarray applications. The principle of the unit-cell is discussed using the current model and the space match condition, along with simulations to corroborate the design and performance criteria. Then, an offset-fed configuration is developed to verify performance of the unit-cell in antenna application, and its polarization transformation property is elaborated. Finally, an offset-fed reflectarray with $10 \times 10$ elements is developed and fabricated. The dual-polarized antenna utilizes the control code matrices to accomplish a wide angle beam-scanning. A full-wave analysis is applied to the reflectarray, and detailed results are presented and discussed. This electronically steerable reflectarray antenna has significant potential for satellite applications, due to its wide operating band, simple control and beam-scanning capability.

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Design of Novel Reconfigurable Reflectarrays With Single-Bit Phase Resolution for Ku-Band Satellite Antenna Applications

This letter provides an approximate analysis of a slotted substrate integrated waveguide with periodic loading elements using the transverse resonance technique. The technique is used to design a travelling wave attenuator whereby pin diodes are capacitively coupled to the waveguide slot. By changing the bias, and therefore loading resistance, a very constant, variable attenuation is produced over the waveguide band.

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Analysis of Loaded Substrate Integrated Waveguides and Attenuators

This communication presents a substrate integrated waveguide (SIW) switched beam antenna operating at 2.45 GHz. The design allows the beam to be switched between six discrete directions giving 360° coverage. The switch beam control is achieved using only four PIN diodes that are integrated directly to the structure allowing its nature to be electrically controlled. The design is no bigger than a single SIW slot antenna although a perpendicular reflector is used. The antenna is shown to be in good agreement with simulated results achieving measured gains between 3 and 6 dBi.

Substrate Integrated Waveguide Switched Beam Antenna

This paper outlines a new variant of a Half-Mode Substrate Integrated Waveguide which enables direct interaction with the wave energy; the rotated Half-Mode SIW. SIW discontinuities are normally vias, but the rHMSIW allows SIW discontinuities to be fabricated directly in copper and hence improved manufacturing tolerances.

A. J. Farrall

Papers

Integrated waveguide slot antennas

Design of Novel Reconfigurable Reflectarrays With Single-Bit Phase Resolution for Ku-Band Satellite Antenna Applications

Analysis of Loaded Substrate Integrated Waveguides and Attenuators

Substrate Integrated Waveguide Switched Beam Antenna

Rotated Half-Mode Substrate Integrated Waveguide