Cagatay Aydin

A frequency tunable broadband amplifier utilizing tunable capacitors and inductors

Software Defined Radio (SDR) technology aims employing commercial communication standards within a single transceiver unit. Therefore, the design of broadband frequency tunable microwave components; particularly tunable amplifiers have gained considerable importance in recent years. In this work, a tunable inductor topology is proposed, theoretically analyzed and simulated. By using tunable capacitors, tunable inductors were obtained and broadband tunable matching networks are designed. Eventually a frequency tunable broadband amplifier covering 800-7500 MHz band has been realized.

Wideband bandpass filter design for X band horn antenna via numerical techniques

Design of an X band horn antenna and a wideband unit element microstrip bandpass filter (UEBPF) for this antenna are presented with satisfactory agreement between theoretical and simulation results. Numerical methods known as real frequency techniques (RFTs) have been utilized in Richards domain to yield optimum driving point Darlington input impedance function belonging to the UEBPF that enables a maximum RF power transmission between the designed horn antenna and an RF driving source. Using a “high precision Richards immittance synthesis package” in Matlab, characteristic impedance values of each UE, out of k number of commensurate (equal length) transmission lines forming the UEBPF, is extracted from the input impedance function. Theoretical design (Matlab of Mathworks Inc.) and simulation (ADS of Agilent Inc., HFSS of ANSYS Corp.) results are shown to be very promising and in a high degree of agreement with each other.

Transformerless bandpass matching network design for Y-shaped monopole antenna

In this paper, a transformerless bandpass matching network design procedure is presented. The Real Frequency Techniques are powerful numerical methods to design wideband lossless 2-port networks such that filters and matching networks. In these techniques, the value of the termination resistance of the designed network could not be yielded as 50 Ω by numerical package. Hence, a transformer is also required for 50 Ω termination which is not practical for high frequency applications. Also in this study a novel wideband monopole antenna is presented. The proposed antenna is consisting of two major elements; Y-shaped impedance matching plate and hemi-circular radiator. Moreover Y-shaped impedance matching plate connected to a feeding probe excites the suspended hemi-circular radiator via air gap. and its frequency band is expanded by using transformerless bandpass design procedure.

A high precision cascade synthesis technique for real frequency matching involving Brune and Darlington Type-C sections

In this work, we introduce a high precision cascade synthesis technique for lossless matching networks involving Brune and Darlington Type-C sections. In the present manuscript, we generalized our previously introduced high precision LC-ladder synthesis algorithm to include the extraction of finite real frequency and right half plane (RHP) transmission zeros of an impedance function as Brune and Darlington Type-C sections respectively. In the modified synthesis algorithm, after each finite frequency and RHP transmission zero extraction, remaining immittance function is corrected using a parametric approach. It is shown that proposed high precision algorithm can synthesize immittance functions of up to 40 reactive elements with accumulated relative error in the order of 10-1. The modified high precision synthesis package is developed in MatLab environment and it is integrated with the real frequency techniques to design high complexity matching networks over broad bands. An illustrative example is presented to exhibit the usage of the proposed high precision synthesis algorithm.

A tunable inductance topology to realize frequency tunable matching networks and amplifiers

Coverage of commercial communication standards such as GSM, UMTS, Wi-Fi and Wi-Max within a single transceiver chip is one of the most desired properties by wireless communication manufacturers. In this regard, communication companies are keenly interested in the design of high power amplifiers for broadband cellular communications to achieve this coverage. In this work, design of broadband tunable matching networks is investigated using Real Frequency Techniques. In practical applications, tunability is needed to compensate for the load impedance variations with environmental effects. In order to be able to work on sample structures, impedance transforming filters with proper topology are chosen and a broadband tunable matching network with a tunability strategy is developed. Eventually a broadband amplifier has been designed using the tunable inductor concept.

Bandpass network function realization in Richards domain and its application to UWB patch antenna matching

In the literature, it is well known that complex Richards-Plane is a transformed domain of Laplace-Plane which is obtained under a tangent hyperbolic mapping. Network functions generated in terms of Richards frequency are periodic in actual frequencies with periodicity π. Once a lowpass prototype network function is designed in Richards domain it is this periodic feature that makes the corresponding periodic bandpass network function to appear at certain bands repetitively in the frequency axis. Designer can choose the interested band among these repetitive bands depending on the application requirements. In the work, a matching network built with microstrip commensurate transmission lines is designed for a microstip patch antenna which is designed to operate in 3.2448-3.744 GHz band, potentially to be used in UWB applications. SRFT (Simplified Real Frequency Technique) is used in the design and very good agreement found between the theoretical design and simulations done in MWO (AWR).

Design of tunable amplifier using digital capacitors

In recent days, radio manufacturers are increasingly interested in broadband amplifiers for cellular communication. Demands of customers enforce manufacturers to develop systems compatible for all standards and it is mandatory to accommodate more than one amplifier or tunable amplifier in front end of communication systems. In this paper, design of tunable amplifier is investigated by using Real Frequency Technique and agility of tunable components is provided by digital tunable capacitors.

Ultra wideband matching network design for a V-shaped square planar monopole antenna

In this paper, design, manufacture, and measurement of a wideband matching network for a broadband V-shaped square planar monopole antenna (V-SPMA) is presented. Matching network design is unavoidable in most cases even vital to facilitate a maximally flat power transfer gain for an antenna. In the work, a bandpass matching network (BPMN) design is done for a particular square monopole antenna with V-shaped coupling element that has essentially bandwidth increasing effect. Designed BPMN and the antenna forms a VSPMA–BPMN matched antenna structure. “real frequency technique” is employed in the BPMN design. BPMN prototype circuit has been constructed on an FR4 laminate with commercial microwave chip inductors and capacitors. Vector network analyzer gain and reflectance measurements of the matched antenna structure have shown highly compatible results to those of the theoretical design simulations along the passband ( 0.8–4.7 GHz). Furthermore, newly proposed distributed capacitor–resistor lossy model for microstrip lines used in the BPMN circuit have exhibited that it can successfully mimic the measured gain and reflectance performance of the matched structure in passband and even in stopband upto 8 GHz. Designed structure can be utilized as a one single wideband broadcasting medium suitable for many communication standards such as GSM, 3G, and Wi-Fi.

Design and investigation of 12–50 Ohm tunable microstrip impedance transforming filter

In practical applications, compensating the changes in transistors input and output impedances due to environmental and thermal effects requires tunable matching networks. Having tunability property is critical in manufacturing as well, since manufacturing errors may be compensated by post-production tuning. In this paper, a 12-50 Ω impedance transforming filter over 800-2200 MHz frequency band is chosen and a broadband tunable matching network has been designed using Real Frequency Direct Computational Technique.