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.

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.

We review mechanically reconfigurable reflectarray (RA) and transmitarray (TA) antennas. We categorize the proposed approaches into three major groups followed by a hybrid category that is made up of a combination of the three major approaches. We discuss the examples in each category and compare their performance metrics including aperture efficiency, gain, bandwidth and scanning range and resolution. We also identify opportunities to build upon or extend these demonstrated approaches to realize further advances in antenna performance.

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.

In this article, a novel batteryless wireless sensor design is proposed and demonstrated. The proposed passive wireless sensor node integrates a ultrahigh-frequency (UHF) radio-frequency identification (RFID) chip, a filter, and a reactive sensor to enable the reading of environmental conditions wirelessly, without increasing the complexity of a typical RFID chip and substantial loss of the read range. The sensor changes the phase of the reflected RFID signal based on the sensed parameter; whereas, the filter helps in resolving any phase ambiguity that may arise due to the placement of the node at different distances. The phase change is detected at the reader using a noncoherent IQ demodulator. The design can easily integrate any type of sensors, such as temperature, humidity, and water-level sensor. A flood sensor and a temperature sensor were used to demonstrate the performance of the proposed design in a home and office environment.

Resonant cavity antennas (RCAs) are suitable candidates to achieve high-directivity with a low-cost and easy fabrication process. The stable functionality of the RCAs over different frequency bands, as well as, their pattern reconfigurability make them an attractive antenna structure for the next generation wireless communication systems, i.e., fifth generation (5G). The variety of designs and analytical techniques regarding the main radiator and partially reflective surface (PRS) configurations allow dramatic progress and advances in the area of RCAs. Adding different functionalities in a single structure by using additional layers is another appealing feature of the RCA structures, which has opened the various fields of studies toward 5G applications. This paper reviews the recent advances on the RCAs along with the analytical methods, and various capabilities that make them suitable to be used in 5G communication systems. To discuss different capabilities of RCA structures, some applicable fields of studies are followed in different sections of this paper. To indicate different techniques in achieving various capabilities, some recent state-of-the-art designs are demonstrated and investigated. Since wideband high-gain antennas with different functionalities are highly required for the next generation of wireless communication, the main focus of this paper is to discuss primarily the antenna gain and bandwidth. Finally, a brief conclusion is drawn to have a quick overview of the content of this paper.