Ramazan Kopru

High Precision Synthesis of a Richards Immittance Via Parametric Approach

A Richards immitance is a positive real function expressed in terms of the Richards variable λ = tanh(pτ) = Σ+jΩ where p=σ+jω is the classical complex frequency. A Richards immittance can be synthesized as a lossless two port terminated in a resistance as in Darlingtons synthesis such that the two-port consists of commensurate transmission lines. In this paper, a high precision method is presented to synthesize a Richards immittance as a lossless two-port constructed with cascade connections of equal length transmission lines, as well as short and open stubs. The new method of synthesis utilizes Bode procedure (or Parametric Method) to correct an immitance function specified in the complex Richards variable λ at each step of the synthesis. It is verified that new technique can synthesize a randomly generated Richards immitance function yielding 25 commensurate lines with the accumulated numerical error less than 10-3. A complete synthesis package is developed in MatLab and successfully integrated with the Real Frequency Technique to design broadband matching networks. Examples are presented to show the merits of the new Richards synthesis tool.

A low loss, low voltage and high Q active inductor with multi-regulated cascade stage for RF applications

Numerous structural planning of active inductors have been proposed as of not long ago in literature which showing tuning conceivable outcomes, low chip area and offering integration facility, they constitute promising architecture to replace passive inductors in RF circuits. The modified of a conventional active inductor based on Gyrator-C topology consisting of both transconductance stages realized by common-source configuration with multi-regulated cascade stage is presented. The Q factor and value of active inductor is adjusted with bias current and flexible capacitance, respectively. Multi regulated cascade stage is used to boost gain of input impedance and inductor value and decrease series resistance of designed inductor witch caused loss. The circuit is suitable for low voltage operation, high quality factor and low power dissipation. Simulation results are provided for 90 nm TSMC CMOS process with 1 V supply voltage. Self-resonance frequency and power consumption of active inductor is 8.9 GHz and 1.2 mW, respectively.

Designing a new high Q fully CMOS tunable floating active inductor based on modified tunable grounded active inductor

A new Tunable Floating Active Inductor (TFAI) based on modified Tunable Grounded Active Inductor (TGAI) is proposed. Multi regulated cascade stage is used in TGAI to boost gain of input impedance and inductor value thus the Q factor enhancement obtained. The arrangement of Multi-Regulated Cascade (MRC) stage is caused the input transistor which determines AI self-resonance frequency to be as small as possible and it is free of body effect which is crucial in sub-micron technology. Compared to traditional CMOS spiral inductors, the active inductor proposed in this paper can substantially improve its equivalent inductance and quality factor. This TFAI was designed using the AMS 0.18 um RF CMOS process, which demonstrates an adjustable quality factor of 10~567 with a 6~284 nH inductance. The Q factor and value of active inductor is adjusted with bias current and flexible capacitance (varactor), respectively. The self-resonance frequency for both grounded and floating AI is about 6.2 GHz. The proposed active inductor also shows wide dynamic range and higher quality factor compared to conventional floating active inductor circuits.

A novel method to design wideband power amplifier for wireless communication

A new approach is presented to design microwave amplifiers to deliver maximum output power using Simplified Real Frequency Technique (SRFT). Proposed method tracks the maximum stable gain (MSG) curve of the active device (BJT, FET etc.) under consideration. Maximum Stable Gain Amplifier (MSGA) possesses higher gain than that of the constant or Flat Gain Amplifier (FGA) along the operating frequency band. Compared to FGA, it is this feature that makes MSGA high efficiency and low DC power consumption amplifier. Employing the proposed design method, a MSG power amplifier is constructed over the frequency band of 800-5200 MHz which can be utilized for GSM, UMTS, Wi-Fi and Wi-MAX applications.

Distributed wideband power amplifier using reactive coupled line feedback structure

A wideband and flat gain distributed power amplifier using a GaN high electron mobility (HEMT) transistor has been designed. The frequency range covers 700 MHz to 4.5 GHz. The small signal gain has the average value of 10 dB. A reactive distributed shunt feedback structure is introduced and implemented by means of microstrip coupled lines. Also, fully distributed input and output impedance matching networks are implemented. The design and simulations are accomplished by advanced design system tool (ADS). The design has undergone large signal, small signal and electromagnetic analysis (EM-simulation). At VDS = 28 V and IDS = 340 mA. Down to the output power back-off of 5 dB at 4.5 GHz, power performance obtained with PAE higher than 35% where the maximum output power is 40.4 dBm.

Unit element bandpass filter design via simplified real frequency technique for UWB microstrip patch antenna

Design of a UWB (Ultra Wideband) microstrip patch antenna to operate in the first channel of the UWB standard and a bandpass (BP) UE (Unit Element) microstrip filter (BPUEF) for this antenna are studied and presented with promising experimental results. A typical UE BP filter is a lossless 2-port network which is formed with certain number of cascade connected commensurate transmission lines. Based on the simplified real frequency technique (SRFT) in Richards domain, driving point Darlington impedance function of the BPUEF is obtained via optimization such that optimum power transfer would be possible between a PA (power amplifier) and the antenna. Using the UE synthesis, characteristic impedance values of each UE is extracted from the input impedance function. Theoretical design (Matlab), simulation (ADS, Agilent Inc.) and the measurements are shown to be in a high degree of agreement.

2W wideband microwave PA design for 824-2170 MHz band using Normalized Gain Function method

In this work, we present the design of a 2W linear wideband microwave PA (power amplifier) targeted to operate in 824-2170 MHz mobile frequency range covering GSM850, EGSM, DCS, PCS and WCDMA. The design is basically based on the NGF (Normalized Gain Function) method which is very recently introduced into the literature. NGF is defined as the ratio of T and |S21|2, i.e. TNGF=T/|S21|2, shape of the gain function of the amplifier to be designed and the shape of the transistor forward gain function, respectively. Synthesis of input/output matching networks (IMN/OMN) of the amplifier requires target gain functions, which are mathematically generated in terms of TNGF. The particular transistor used in the design is FP31QF, a 2W HFET from TriQuint Semiconductor. Theoretical PA performance obtained in Matlab is shown to be in a very high agreement with the simulated performance in MWO (Microwave Office) of AWR Inc.

A new high performance CMOS active inductor

A new high-performance active inductor with ability to tune its self-resonance frequency and quality factor without affecting each other is presented in this letter. Using the input transistor of active inductor in cascoding configuration gives this property to designed circuit. Furthermore, the input transistor topology make the device robust in terms of its performance over variation in process and temperature. On the other hand, RC feedback is used to cancel the parasitic components in input node of the active device, which results to improve circuit performance. Schematic and post-layout simulation results shows the theory validity of the design. Monte Carlo and temperature analysis is done to show structure robustness in PVT variation. Inductive behavior frequency range of suggested structure is 0.3-11.4 GHz. Maximum quality factor is obtained as high as 3.7k at 6.3 GHz. Total power consumption is as low as 1mW with 1.8 V power supply.

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.