This paper describes a new Wilkinson power divider on a single-layer microstrip line that can reduce the occupied area, suppress the harmonic components, and/or provide the arbitrary power division ratios. It consists of two-section transmission lines, two inductors, and one isolation resistor. Four different designs have been conducted to investigate the capabilities of the structure. In addition, a compact divider along with harmonic suppression and a practical divider with a large power-dividing ratio has been constructed and measured. The simulation and measurement results are in good agreement with each other. This indicates that the structure can effectively be used as a power divider for miniaturized or arbitrary power division ratio applications.

In this paper, one simple dual-band (28 and 38 GHz) circularly polarized slotted patch antenna, suitable for future millimeter wave mobile communication, is presented. The proposed monolayer circularly polarized patch antenna is considered without any 90° phase shifter and is excited by a single-feed microstrip line, which is very desirable for high gain antenna array implementation in millimeter wave band in order to compensate the link loss. From EM simulation, it has been found that the dimensions of the L-shaped slots significantly affect the performance of the antenna. The antenna has been prototyped and the measured results show that the antenna can simultaneously provide circular polarization in the two suggested millimeter-wave bands for the upcoming 5G mobile communications.

In this work, a mm-Wave vertically-polarized electric dipole array solution for 5G wireless devices is presented. The dipole is fabricated using vias in a standard PCB process to fit at the phone or tablet edges featuring wideband operation with broad half-power beamwidth in the elevation plane (HPBWELEV), high gain and high front-to-back radiation ratio (F/B). For enhanced gain, parasitic-vias are added in front of the dipole as directors. To improve HPBW without sacrificing gain, the directors are implemented as V-shaped bisection parasitic-vias. A via-fence surrounds the dipole structure to suppress back radiation and enhance F/B. The dipole is connected to a parallel-strip line (PS) which is interfaced to the main SIW feed through a novel SIW-to-PS transition. Thorough investigation, optimization, and parametric study are provided for each design parameter of the proposed structure. A single dipole, 2×1, and 4×1 arrays were designed and fabricated showing close agreement between the simulated and measured results. The single-dipole operates over 7.23-GHz bandwidth with stable radiation performance. The 4×1 array achieves HPBWELEV of 133.1∘, F/B of 36.6-dB, cross-polarization less than -39.6-dB and 12.61-dBi gain with 95.8% radiation efficiency. The low cost, compactness, and good performance of the proposed dipole make it a competing candidate for the future 5G mobile devices transceivers.

A novel double-layered vertically stacked substrate integrated waveguide leaky-wave antenna (SIW LWA) is presented. An array of vias on the narrow wall produces leakage through excitation of TE10 fast-wave mode of the waveguide. Attenuation and phase constants of the leaky mode are controlled independently to obtain desired pattern in the elevation. In the azimuth, top and bottom layers radiate independently, producing symmetrically located beams on both sides of broadside. A new near-field analysis of single LWA is performed to determine wavenumbers and as a way to anticipate radiation characteristics of the dual layer antenna. In addition to frequency beam steering in the elevation plane, this novel topology also offers flexibility for multispot illumination of the azimuth plane with flat-topped beams at every φ-cut through excitation of each layer separately or both antennas simultaneously. It is shown that the proposed antenna solution is a qualified candidate for 5G base station antenna (BSA) applications due to its capability of interference mitigation and latency reduction. Moreover, from the point of view of highly reliable connectivity, users can enjoy seamless mobility through the provided spatial diversity. A 15-GHz prototype has been fabricated and tested. Measured results are in good agreement with those of simulations.

This paper describes a new approach for the theoretical design of unequal multisection Wilkinson power dividers, using single-layer microstrip lines. Similar to most multisection structures, the presented unequal divider can provide a broadband performance. To provide the design guideline, closed-form formulas are derived for the divider with odd or even number of sections. In each case, various simulations have been conducted to investigate the performance of dividers over the frequency band. For experimental verifications, two 1:2 power dividers with a center frequency of 1 GHz are fabricated, having three and four sections. The simulated and measured results are presented, and good agreements between them are observed.

This paper proposes a new design method to achieve adverse-resistant microwave sensors using balanced structure of two sensors. Any kinds of sensors can be used in the presented balanced architecture. However, a new kind of high-resolution microwave material sensor, based on the injection locking phenomenon, is presented and used in this paper. By injecting a low-power level and low-phase noise signal to an oscillator, an injection-locked oscillator with a very small lock range is achieved with a very high sensitivity to its resonator condition. In the balanced structure, for a standard sample over one branch and an arbitrary sample over the other, the difference between center frequencies and lock ranges of oscillators can be measured at once. Therefore, the dielectric constant and loss tangent of unknown samples are calculated while the adverse environmental variations have the same effects on both branches and are compensated automatically without additional sensors and environmental controlling system. Moreover, it is indicated that using a simple frequency comparator with an output voltage instead of a spectrum analyzing system makes the system more practical and low cost. As an example for validation, a system is fabricated at 1 GHz and results of various states have been presented.