Ilona Piekarz

Coupled-Line Sensor With Marchand Balun as RF System for Dielectric Sample Detection

A novel nondestructive method for effective permittivity measurement and detection of samples permittivity change in microwave frequency range has been proposed, utilizing a Marchand balun and a coupled-line sensor. The out-of-phase excited coupled-line section is used to obtain high sensitivity on the covering sample, which can be as narrow as the spacing between coupled strips. Formulas describing balanced to unbalanced impedance transformation of a Marchand balun have been provided, hence the proposed method requires only one-port measurement to determine effective permittivity in a wide frequency range. The proposed setup has been theoretically and experimentally investigated. The obtained measurement results proved the usefulness of the proposed approach for dielectric sample detection.

Microstrip Antenna Array With Series Feeding Network Designed With the Use of Slot-Coupled Three-Way Power Divider

A novel concept of a series feeding network of a microstrip antenna array has been shown. The proposed feeding network utilizes a four-port slot coupler as a three-way power divider, which is composed of two microstrip lines appropriately coupled through a slot within a common ground plane. The proposed power divider is used for simultaneous power distribution between two consecutive linear subarrays and between two 4 × 1 linear arrays constituting a single 8 × 1 linear subarray, where equal-amplitude and out-of-phase signals are required. Such a solution allows for realization of antenna arrays, in which all linear subarrays designed with the use of the “through-element” series feeding technique are fed at their centers from single transmission lines. The theoretical analysis as well as measurement results of the 8 × 8 antenna array operating within 10.5-GHz frequency range are shown.

Input Match and Output Balance Improvement of Marchand Balun With Connecting Line

A novel method allowing for improvement of input match and output balance of Marchand balun with connecting line has been presented. The proposed compensation technique together with the ideal Marchand balun design formulas allow for achieving an arbitrary impedance transformation ratio even for the circuit having a long connecting line. The theoretical analysis has been verified by EM simulations and measurements of a Marchand balun composed of 3 dB coupled-line sections and 30° transmission line operating at the center frequency f 0 = 1.15 GHz and terminated at input and outputs with 50 Ω and 100 Ω, respectively.

Right/Left-Handed Transmission Lines Based on Coupled Transmission Line Sections and Their Application Towards Bandpass Filters

Novel metamaterial structures featuring left-handed (LH) and composite right/left-handed (CRLH) character are presented. The proposed unit cells utilize sections of coupled transmission lines. It is shown that by taking advantage of the coupling between transmission lines an additional degree of freedom is achieved, and therefore, the design process of artificial transmission lines is more flexible. The general behavior of each of the proposed circuits is presented and analyzed. Moreover, the design equations are formulated and the design process of each unit cell is described. The usefulness and validity of the proposed unit cells are illustrated and verified by the design and measurements of compact artificial transmission line sections utilizing the presented structures. Moreover, possible applications are discussed.

Semi-Distributed Approach to Dual-Composite Right/Left-Handed Transmission Lines and Their Application to Bandstop Filters

In this letter, an innovative approach for realization of artificial transmission lines featuring a dual-composite right/left-handed character is presented. The circuits utilize a novel semi-distributed unit cell which is composed of sections of conventional transmission lines and a lumped capacitor. Such an approach allows for efficient modeling and convenient translation of model parameters (characteristic impedance and electrical length of transmission lines) into physical realization. Moreover, a single-layer microstrip realization is possible, making the unit cell attractive in practical applications. The proposed concept has been experimentally verified by the design and measurements of an exemplary transmission line section, and discussed in a context of possible applications in bandstop filters.

Microwave Sensors for Dielectric Sample Measurement Based on Coupled-Line Section

In this paper, a novel class of sensors composed of coupled-line sections dedicated for complex permittivity measurements of dielectric samples have been proposed. The end-shorted and open-ended coupled-line sections have been used as sensing elements for nonresonant and nondestructive measurements allowing for characterization of dielectric samples. It has been shown that by utilization of an iterative procedure, the complex permittivity of a dielectric material under test can be determined based on the measured complex odd-mode effective permittivity of the system. Since the complex odd-mode effective permittivity is mainly related to the mutual capacitance between coupled strips, high sensitivity on the covering sample has been obtained and the measured sample can be as narrow as the spacing between the coupled strips. The proposed sensors have been theoretically investigated and experimentally validated. The obtained results have been compared and the sensors’ advantages and limitations have been discussed. The obtained measurement results have proved the correctness and usefulness of the proposed approach.

Effective permittivity measurement with the use of coupled-line section sensor

In this paper, a new method for measurement of effective permittivity in microwave range with the use of coupled-line section sensor is presented. In the proposed technique, a differential measurement is performed to obtain high sensitivity on the covering sample, which can be as small as the distance between sensor s coupled strips. The proposed approach has been theoretically and experimentally investigated and verified. The obtained measurement results prove the usefulness of the proposed sensor in terms of unknown dielectric sample detection.

Wide-beam microstrip antenna for application in 24 GHz short-range Doppler sensors

A wide-beam microstrip antenna for applications in short-range Doppler sensors has been developed. Beam widening has been achieved with the use of appropriately fed three radiating patches. To ensure a proper signal distribution along the array, a center radiating element has been designed as an aperture coupled patch fed at its center thorough the slot. Moreover, the center patch serves as a two-way power divider allowing for feeding two outer patches with appropriate amplitudes and phases ensuring simultaneously central symmetry of the antenna which improves radiation pattern.

Sensitivity investigation of coupled-line microwave sensor on dielectric material-under-test

In this paper, sensitivity analysis of the recently developed coupled-line sensor has been presented. The proposed sensor allows for detection of dielectric materials permittivity change in a wide frequency range, which is an essential property for e.g. environmental monitoring. The previously conducted theoretical investigation of the sensitivity has been now confirmed by experimental results, proving correctness and usefulness of the presented approach.

Calibration method of microwave measurement system for dielectric samples detection

In this paper, calibration method of microwave measurement system for dielectric samples detection composed of two baluns and coupled-line sensor inserted in-between is presented. The presented sensor allows for detection of dielectric sample having size comparable to the distance between the sensors coupled strips and therefore is dedicated for biomedical or industrial applications. To directly measure the coupled-line sensor and eliminate the influence of the baluns on the obtained measurement results, the recently published calibration method has been adopted and utilized. The obtained results prove the correctness of the presented approach.