Mohammad Mahdi Honari

Compact Microstrip Wilkinson Power Dividers With Harmonic Suppression and Arbitrary Power Division Ratios

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.

High-Resolution Balanced Microwave Material Sensor With Extended Dielectric Range

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.

A Dual-Band Low-Profile Aperture Antenna With Substrate-Integrated Waveguide Grooves

This communication presents a new dual-band low-profile aperture antenna with relatively high gain using substrate-integrated waveguide (SIW) corrugated structures. It consists of a cavity excited by a transmission line and four SIW grooves that produce good reflection coefficient and enhanced gain. By designing corrugated structure using constructive superposition of electric fields of patch and grooves, the antenna with high performance in both bands is achieved. In the proposed structure, three simple printed circuit boards (PCBs) for implementing a resonant transmission line and specific SIW structures are employed instead of waveguide feeder and grooves on metallic plate in conventional corrugated antennas. Removing the metallic plate reduces the weight and cost of the structure and provides ease of fabrication. Dual-band characteristic is achieved using resonant slot (cavity) and resonant transmission line. Fabrication results show that the SIW grooves significantly increase the antenna gain with respect to the simple slot antenna.

Microfluidic liquid metal based mechanically reconfigurable antenna using reversible gecko adhesive based bonding

This paper describes a new fabrication method for flexible electronics made of microfluidic structures filled with liquid metal in a thermoplastic elastomer, styrene ethylene butylene styrene (SEBS). The devices can reversibly be bonded to a larger system with gecko inspired dry adhesives. To demonstrate the feasibility of the method, a mechanically reconfigurable folded dipole has been fabricated and 55% frequency tuning with a 20% to 40% bandwidth for various frequencies has been achieved.

Theoretical Design of Broadband Multisection Wilkinson Power Dividers With Arbitrary Power Split Ratio

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.

Aperture-coupled multi-layer broadband ring-patch antenna array

An aperture-coupled multi-layer broadband microstrip array antenna with coupling ring slots and modified ring patches is presented. The structure of the array consists of a 3-dB 180°-phase shifter, two 1-ports and two 2-ports aperture-coupled microstrip antennas. All parts of the array antenna are designed for broadband operation. The array antenna works based on the back coupling to the microstrip line of 2-port aperture-coupled antenna. Simulation results of the array display encouraging properties, such as wide impedance bandwidth of 77% for |S11| < -10dB and nearly stable gain. The maximum gain of the array antenna is almost 12.65dBi at 5GHz. The radiation efficiency, radiation pattern, side-lobe level and cross-polarization are also adequate within the impedance bandwidth between of 3.34 and 7.53GHz.

High-Resolution Dielectric Sensor Based on Injection-Locked Oscillators

The structure of a high-resolution microwave material sensor is presented based on the injection locking phenomenon. For a sample under test, the variation of center frequency and lock range of the oscillator with respect to a reference sample are measured to indicate the resonance frequency and quality factor of the resonator. A low power level and low phase noise injection locking can significantly reduce the lock range of the oscillator. Therefore, even small variations in the loop filter of the oscillator change the response and can be determined with a high sensitivity. The unknown sample is characterized based on the measured center frequency and quality factor of the resonator. An output power control (OPC) system increases the dynamic range of the sensor with respect to the dielectric constant of samples. Moreover, a method of material detection in the microwave frequency is proposed based on data from the OPC to eliminate the frequency analyzer from the system for Internet of Things (IoT) applications. As an example for validation, a 1-GHz sensor is fabricated and the measurement results are presented.

Two-Layered Substrate Integrated Waveguide Filter for UWB Applications

In this letter, an ultra-wideband (UWB) substrate integrated waveguide (SIW) filter using ridge resonator is presented. The filter relies on designing SIW ridge resonator. The comb-shaped resonator makes the filter to be realizable for UWB characteristics. The upper edge of the passband can easily be adjusted by the width of small rod in the ridge resonator. A parametric study is done to show how bandwidths can be adjusted. The measurement results show that a reflection coefficient of better than −14 dB has been obtained over the frequency band of 3.1–10.6 GHz. The maximum insertion loss in passband is almost 1 dB. Moreover, a stopband from 11.4 to 17.4 GHz with a suppression magnitude better than 47 dB has been achieved.

An efficient power recycling method for multi-port receivers

In this paper, we introduce a power recycling method for multiport receivers. A general formulation for multi-port structures as a demodulator is presented. This is followed by proposing the recycling method based on harmonic separation at the outputs. Then, the method is tested on an implemented six-port receiver at 2.4 GHz. The results shows about 17% power recovery without any degradation in the performance.

Ground de-embedded source reconstruction using a planar array of H-field probes

This paper presents an introduction to a new source reconstruction method SRM which tries to deal with a special measurement scenario involving a finite ground plane. In this particular scenario, an array of H-field probes is placed slightly on top of a finite rectangular ground plane as such the normal SRM techniques are not the best choice when it gets to source reconstruction. Our primary goal in this work is to improve the accuracy of near-field to far-field transformation via the reconstruction method. We verify our method by comparing the far-field radiation pattern calculated by this application to that of the typical plane wave spectrum method (PWS).