Recently, the desired very high throughput of 5G wireless networks drives millimeter-wave (mm-wave) communication into practical applications. A phased array technique is required to increase the effective antenna aperture at mm-wave frequency. Integrated solutions of beamforming/beam steering are extremely attractive for practical implementations. After a discussion on the basic principles of radio beam steering, we review and explore the recent advanced integration techniques of silicon-based electronic integrated circuits (EICs), photonic integrated circuits (PICs), and antenna-on-chip (AoC). For EIC, the latest advanced designs of on-chip true time delay (TTD) are explored. Even with such advances, the fundamental loss of a silicon-based EIC still exists, which can be solved by advanced PIC solutions with ultra-broad bandwidth and low loss. Advanced PIC designs for mm-wave beam steering are then reviewed with emphasis on an optical TTD. Different from the mature silicon-based EIC, the photonic integration technology for PIC is still under development. In this paper, we review and explore the potential photonic integration platforms and discuss how a monolithic integration based on photonic membranes fits the photonic mm-wave beam steering application, especially for the ease of EIC and PIC integration on a single chip. To combine EIC, for its accurate and mature fabrication techniques, with PIC, for its ultra-broad bandwidth and low loss, a hierarchical mm-wave beam steering chip with large-array delays realized in PIC and sub-array delays realized in EIC can be a future-proof solution. Moreover, the antenna units can be further integrated on such a chip using AoC techniques. Among the mentioned techniques, the integration trends on device and system levels are discussed extensively.

A novel high-gain dielectric resonator antenna (DRA), featuring a peak realized gain of 11.3 dBi over a fractional bandwidth of 16.6% around 30 GHz, is presented. The proposed antenna structure, excited by a slot coupled microstrip line, is composed of a cylindrical dielectric resonator and of a truncated plastic-based conical horn useful to enhance the gain. An annular perturbation notch is realized in the dielectric horn to achieve a better focusing of the RF energy along the antenna boresight direction, while reducing the side-lobe levels (SSLs). The presented antenna design achieves SSLs below -10 dB for both the E- and H-plane so to meet the requirements of next-generation 5G wireless communication protocols and of low-cost satellite and mobile systems.

This article reviews the current state-of-the-art of millimeter-wave (mm-wave) antennas for communication and sensing applications in the D-band between 110 and 170 GHz. The most popular design techniques, including Antenna-on-Board (AoB), slotted waveguides, Antenna-in-Package (AiP) and Antenna-on-Chip (AoC), are described using relevant examples from scientific literature. Potential benefits and limitations of integration technologies, such as specialized packaging, chip post-processing steps and interconnects, are listed as well. The reported performances of all listed designs are compared against each other, taking the antenna size relative to operating frequency into account. This novel comparison indicates that small-scale integrated AiP and AoC designs can achieve competitive performance levels with short and low-loss interconnects.

A novel 2 2 array of microstrip antennas was developed that generates orthogonal circularly polarized waves at two frequencies simultaneously. This true shared aperture can be used as a building block in full-duplex wireless communication applications such as focal-plane arrays for satellite internet (VSAT) and wireless connectors. An alternative implementation of the sequential rotation technique was applied to create dual-frequency operation using only a single aperture. The concept was verified with experimental results from a prototype consisting of a 2 2 array of aperture coupled microstrip antennas (ACMAs) with corresponding feed network operating at 4 and 6 GHz. Measurements show that the axial ratio (AR) is below 1.2 dB for both the low-band as well as the high-band mode of operation. The isolation between both modes is larger than 26 dB, eliminating the need of high-performance duplexers.

A novel technique is presented for sidelobe and axial ratio control of circularly-polarized phased array antennas. Although our new random sequential rotation (RSR) concept uses a regular periodic array grid, it provides similar properties as randomly-spaced array antennas. In this way, a wideband behavior is provided, without the appearance of grating lobes. In addition, the gain is maximized, since a uniform amplitude distribution is used. A 4 GHz prototype consisting of 16 aperture-coupled microstrip antennas with a beamformer was developed to demonstrate the basic properties of RSR array antennas. Although the element spacing is much larger than half a wavelength, well-controlled sidelobes are provided, even in the worst-case diagonal plane. The measured cross-polarization level at 4 GHz is below -20 dB at a 20-degree scan angle in the diagonal-plane.

A novel wideband substrate integrated waveguide (SIW) antenna topology, consisting of coupled half-mode and quarter-mode SIW resonant cavities, is proposed for operation in the 60 GHz band. This innovative topology combines a considerable bandwidth enhancement and a low form factor with compatibility with low-cost printed circuit board manufacturing processes, making it excellently suited for the next generation, high data rate wireless applications. Moreover, exploiting SIW technology, a high antenna-platform isolation is obtained, enabling dense integration with active electronics without harmful coupling. The computer-aided design process yields an antenna that covers the entire 57–64 GHz IEEE 802.11ad band with a measured fractional impedance bandwidth of 11.7% (7 GHz). The measured maximum gain and radiation efficiency of the prototype are larger than 5.1 dBi and 65%, respectively, within the entire impedance bandwidth.