In this paper, a dual-band on-chip meander-line monopole antenna is proposed and demonstrated for emerging 5G-compatible IoT-served sensor nodes. The targeted 28/60-GHz compact antenna is a hybrid structure of meander-line monopole antenna and packaging substrate to both shield the antenna from its deployed environment and to enhance the antenna radiation efficiency as well as the gain over the two bands of interest. The antenna model and design analysis are presented in this work together with a fabricated and tested 65-nm-bulk CMOS chip. The prototyped on-chip antenna exhibits a measured gain of -10 dBi at 28 GHz with a bandwidth of 5.3% and 0 dBi at 60 GHz with a bandwidth of 5.9%. A radiation efficiency of 45% and 30% is obtained at 28 and 60 GHz, respectively. The antenna occupies a space of 0.25 x 0.3 mm2 (λ/43 x λ/35.7 at 28 GHz). The on-chip antenna solution proposed in this work addresses the highly desirable yet challenging overall design of future wireless systems (5G and beyond) which hit the mark on compactness, cost and compatibility. In addition, this work provides a viable design platform for achieving frequency diversity and multi-functionality of future wireless involving power harvesting, data transfer and sensing operation.

A rectangular WR12 waveguide to microstrip line (MSL) transition using a very thin high-permittivity ceramic substrate (ϵr = 9.9 and h = 127 μm) is presented and analyzed. The proposed configuration uses a gradually extending metal ridge over a thin-film MSL to ensure electric field transformation, and an accurate impedance matching, while maintaining a good electrical contact, without any soldering or gluing. The fabricated prototype has been successfully tested in terms of insertion and return losses. The obtained results exhibit a bandwidth of more than 37% at -10 dB with an insertion loss of 1.5-2.7 dB, over the entire 60-90-GHz frequency band. The design simplicity and suitability for high-permittivity thin-film substrates, as well as the very broadband operation capability, enable it to be easily integrated with various planar monolithic microwave integrated circuits/miniaturized hybrid microwave integrated circuits microstrip circuits for different millimeter-wave applications.

In this article, a tunable ferrite-loaded isolator working at millimeter-wave (mm-Wave) frequency for applications in multi-function systems is presented. The device is based on nonreciprocal coupling between a ferrite slab and a half-mode substrate-integrated waveguide (HMSIW). The HMSIW offers a compact design and, more important here, the ability of energy coupling to adjacent resonators. The ferrite slab is placed outside the HMSIW, close to the H-wall symmetry of the HMSIW, providing the possibility of movement for the ferrite slab and low insertion loss of the transmission mode. Any change in the position of the ferrite slab changes the propagation constant of the mode traveling across the ferrite-coupled HMSIW, which, consequently, results in different center frequencies of the isolation. To the best of our knowledge, the proposed design is one of the first tunable isolators for such a high frequency. Despite previously reported isolators that require a strong magnetic bias field for mm-Wave range applications, the proposed isolator requires a relatively low magnetic bias (less than 20 KA/m), which is provided by a small and lightweight permanent magnet. The 10 dB isolation bandwidth of the design is about 2 GHz varying from 34 to 37 GHz based on the position of the ferrite slab. The insertion loss of the device is measured between 2 and 3 dB.

A highly reconfigurable and switchable patch coupler is presented with controllability of the operating frequency, power-dividing ratio, and switching coupling direction for millimeter-wave applications. A patch coupler is loaded with varactors at the two sides edges and an array of five p-i-n diodes in the middle of the patch to realize this unique property. Varying the capacitance across two sides of the patch enables varying the electrical length and tuning the frequency. The array of p-i-n diodes in the middle of the patch controls the size of the common region, providing power-division ratio controllability. Based on the investigation of the developed lumped-element models, the design requirements and physical parameters to achieve the envisaged reconfigurability are defined. For experimental/demonstration purposes, a prototype is fabricated and characterized. It demonstrates a tunable operating frequency of the five sections from 22 to 30.5 GHz, a controllable power-dividing ratio between output ports from $-$ 21 to 25 dB with a loss of 1.5 dB, and a switchable operational direction between ports. The capabilities to control the power-dividing ratio and frequency simultaneously allow high reconfigurability to be achieved.

This communication presents a circularly polarized (CP) antenna array with ultra-broadband characteristics and a high gain for millimeter-wave applications. The CP is achieved by arranging eight linearly polarized (LP) tapered slot antenna elements in a circular arrangement based on sequential rotation techniques. The hybrid structure takes advantage of microstrip line (MSL) compactness in the feeding network and the capabilities of the substrate integrated waveguide (SIW) in antenna element design. A new T-junction MSL-to-SIW transition with a wide range of coupling ratios is used to serve as a wide power divider in the compact sequential rotation-feeding network. A detailed parametric study is carried out to demonstrate the effects of the coupling mechanism between the two transmission lines and to find the optimal configuration for the elements of the proposed antenna array. A trade-off is made between antenna coupling, phase deviation, and overall size to achieve a compact structure with robust performances. An 8 element antenna array prototype is fabricated through the PCB process with a size of 57 × 48 × 96 mm3. Measured results show a 3 dB axial ratio bandwidth of about 49% over the entire 22.8 – 37.7 GHz range and a maximum gain of 18 dBi.

High gain antennas play an essential role in future wireless applications by ensuring sufficient compensation for propagation losses in long-range communication. This work presents a novel design of metasurface-inspired high gain miniaturized antenna for 28 GHz millimeter wave applications. Firstly, to improve the radiation gain of the suggested antenna, only two metallic shorting pins are inserted between radiating patch and ground of antenna.The total size of the proposed shorting pin based microstrip patch antenna is 18\(\times\)14 mm². This approach differs from traditional methods of increasing the radiating area or using bulky techniques. For further gain enhancement, the antenna incorporates a single layer of metasurface made up of a compact and uniquely designed reflecting metamaterial unit cell array. The distinctiveness of these unit cell design is centered on a simple 2\(\times\)2 array created by combining circular and hexagonal split rings. This innovative configuration improves antenna gain while maintaining a compact form factor.This metamaterial array is positioned at approximately 0.5 \(\lambda _{0}\) (where \(\lambda _{0}\) is the wavelength in millimeters) above the antenna, thus creating a Fabry-Perot cavity, and substantially improves the gain exceeding 13 dBi.The metasurface, which is made up of specially designed unit cells, modifies the electromagnetic field distribution and surface waves to produce better radiation properties. Furthermore, the final optimized bandwidth achieved is 26.62–29.79 GHz with peak radiation efficiency up to 94%, respectively. The findings provide satisfactory agreement when comparing simulation results with experimental data. The presented antenna system is developed to meet stringent gain requirements for 5G antennas operating in the millimeter wave frequency band.