Salih Demirel

Design of an Ultra-Wideband, Low-Noise Amplifier Using a Single Transistor: a Typical Application Example

In this work, a design method of an Ultra-Wideband (UWB), low-noise amplifler (LNA) is proposed exerting the perfor- mance limitations of a single high-quality discrete transistor. For this purpose, the compatible (Noise F, Input VSWR Vi, Gain GT) triplets and their (ZS, ZL) terminations of a microwave transistor are exploited for the feasible design target space with the minimum noise Fmin(f), maximum gain GT max(f) and a low input VSWR Vi over the available bandwidth B. This multi-objective design procedure is reduced into syntheses of the Darlington equivalences of the ZSopt(f), ZLmax(f) terminations with the Unit-elements and short-circuited stubs in the T-, L-, ƒ-conflgurations and Particle Swarm Intelligence is successfully implemented as a comparatively simple and e-cient optimization tool into both veriflcation of the design target space and the design process of the input and output matching circuits. A typical design exam- ple is given with its challenging performance in the simple ƒ- and ƒ-conflgurations realizable by the microstrip line technology. Further- more the performances of the synthesized ampliflers are compared us- ing an analysis programme in MATLAB code and a microwave system simulator and verifled to agree with each other.

Efficient scattering parameter modeling of a microwave transistor using Generalized Regression Neural Network

In this paper, a simple, accurate, fast and reliable black-box modeling is presented for the Scattering (S-) parameters of a microwave transistor from the reduced amount of the discrete data using General Regression Neural Network (GRNN). GRNN is a probability- based Neural Network and has been used in the generalization applications in the cases of the existence of the poor data bases. In this work, the GRNN-based modeling is implemented to the microwave transistor BFP640 with the separate interpolation and extrapolation applications and the comparative results are given. It can be concluded that the superior extrapolation ability of a GRNN can be used in generalization of the reduced amount of scattering parameter data accurately to the entire operation domain of device, thus in S- parameter modeling of a microwave transistor can be achieved.

A Compact Vivaldi Shaped Partially Dielectric Loaded TEM Horn Antenna for UWB Communication

Ultrawideband (UWB) antennas are of huge demand and Vivaldi antennas as well as the TEM horn antennas are good candidates for UWB applications as they both have relatively simple geometry and high gain over a wide bandwidth. The aim of this study is to design a compact antenna that achieves maximum gain over a bandwidth between 1.5 and 10.6 GHz while minimizing its size. The idea is to make use of combined respective advantages of Vivaldi and TEM horn antennas to achieve the desired goals by shaping the TEM horn antenna to look like a Vivaldi antenna. The antenna structure is modified by a dielectric load in the center to increase the gain bandwidth. It is placed in a surrounding box made of PEC material to reduce the undesired side lobes and to obtain more directive radiation pattern. The simulations are performed by using the CST STUDIO SUITE electromagnetic (EM) simulation software and they are later verified by the actual measurements. The Vivaldi shaped partially dielectric loaded (VS-PDL) TEM horn antenna is proposed as a compact UWB antenna for systems using the newly established UWB band and also for the communication systems of popular bands like ISM, Wi-Fi, and GSM.

Honey- bees mating algorithm applied to feasible design target space for a wide- band front- end amplifier

In this article, the feasible design target space is determined for the input stage-requirements of an ultra-wide band low-noise front end design using a single transistor. The problem is set as an optimization problem where honey-bees mating have been used as search and optimization tool within in the problem domain. The primary reason to use this algorithm is ease of its use, broad applicability and global perspective. The honey-bee mating process has been considered as a typical swarm-based approach to optimization, in which the search algorithm is inspired by the process of honey-bee mating in real life. In this paper, the honey-bee mating (HBMO) algorithm is presented as a new meta-heuristic optimizationtool to determine design target space for a microwave amplifier subject to the potential performance of the employed transistor.

Performance characterization of a microwave transistor subject to the noise and matching requirements

In this paper, the gain GT of a microwave transistor is expressed analytically in terms of the mismatchings Vini¾ź1, Vouti¾ź1 at the ports, noise figure Fi¾źFmin and the [z]-parameter and noise parameters. Firstly, because the input termination ZS determines the noise Fi¾źFmin, thus the input termination ZS is pre-determined to lie on the tangent constant noise and available gain circles so that the maximum power delivery is ensured for the given noise. Then, a design configuration is constructed in the input impedance Zin- plane covering the gain and the required input and output mismatch circles within the Unconditionally Stable Working Area for the predetermined input termination ZS. Finally, the compatible Fi¾źFmin, GT, Vini¾ź1, Vouti¾ź1 quadrates for either required or optimum Vini¾ź1, Vouti¾ź1 couples are obtained with their ZS, ZL couples from the analysis of the design configuration. Furthermore, a case study is also presented for the full flexible performance characterization of a selected microwave transistor. It can be concluded that the near future microwave transistor is expected to be identified by performance data base built by its compatible Fi¾źFmin, GT, Vini¾ź1, Vouti¾ź1 quadrates and the ZS, ZL terminations within the device operation domain to overview all the possible low-noise amplifier designs using the full device capacity. Copyright

Design of an ultrawide band low noise microstrip amplifier using 3D sonnet- based SVRM with particle swarm optimization for space applications

In this work, a determinististic, efficient design methodology is put forward to design a wide-band, low-noise microstrip amplifier, where the microstrip widths, lengths {W^→,ℓ^→} of the input/ output matching networks are obtained accurately and fast for a substrate {ε_r, h, tanδ} using the cost-effective 3D EM- based Support Vector Regression Machine (SVRM) microstrip model provided that ensuring the stable source Z_S(ω) and load Z_L(ω) terminations for the compatible {Noise F(ω) ≥ F_min(ω), Input VSWR Vi(ω) ≥1, Gain G_Tmin(ω)>G_T(ω)≥G_Tmax(ω), Bandwidth B} quadrates of the employed transistor. The 3D EM- based SVRM microstrip model provides the accurate and fast characterization of the equivalent transmission line in terms of the characteristic impedance Z₀ and the dielectric constant ε_eff within the continuous domain of {0.1mm ≤ W ≤ 4.6 mm, 2 ≤ ε_r ≤ 10, 0.1mm ≤ h ≤ 2.2mm, 2GHz ≤ f ≤ 14GHz} in an efficient manner. In the modeling process, the substantial reduction (up to %64) is obtained utilizing sparseness of SVRM in the number of expensive fine discretization training data with the negligible loss in the predictive accuracy using the quasi-TEM microstrip synthesis formulas as the coarse model that allow to identify the regions of the design space requiring denser sampling. Moreover, the multi-objective amplifier design problem is reduced into the two single-objective design problems of the input(IM)/ output (OM)matching networks to provide the source Z_S(ω) and load Z_L(ω) terminations to the transistor, respectively. Finally the design methodology is applied to the design of typical wideband low-noise amplifiers of the transistor NE3512S02 within 3GHz and 8GHz using T-, II- L types of microstrip matching circuits satisfying the maximum gain provided the available minimum noise and a permitted amount of input mismatching at each operation frequency. In the design optimization of the IM/OM networks, a Memetic Algorithm (MA) in which a simple local optimizer called Nelder-Mead (NM) algorithm is used along with the global optimizer Particle Swarm (PSO) algorithm is used. Furthermore, typical T-T designed amplifier is validated using the Circuit Simulator AWR and 3 D EM Simulator SONNET.

Front-end design for Ka band mm-Wave radar

In this paper front-end design for a Ka band milimeter wave (MMW) radar which consists of an antenna, a low noise amplifier (LNA) and a band pass filter is presented. The operation frequency of the designed system is between 24-25 GHz in Ka band. A high gain axially displaced elliptical (ADE) dual reflector antenna is employed on the antenna structure. ADE sub-reflector with 5 cm diameter is illuminated by a feeder horn and a main reflector 30 cm diameter parabola focuses incoming waves from the ADE sub-reflector. According to the simulation results narrow half power beam width (HPBW=30) and high gain (G=35 dBi) are obtained with good efficiency (%58). An HJ-FET that has low noise figure (NF<;1 dB) and high gain (>13 dB) is utilized to design a LNA. Double transistors are connected as cascaded to achieve higher transducer gain (Gt>19 dB). Matching circuits and feeder resonators are designed by microstrip lines to obtain low input and output VSWR (Vin<;2.1, Vout<;2.1). A microstrip band pass filter (BPF) is designed to receive required signals and to suppress other bands. The BPF is formed by combination of a radial stub low pass filter (LPF) and a short stub high pass filter. Low insertion loss (S21>-2.5dB) and low return loss (S11<;-15 dB) are aimed to take signal as lossless as at pass band. The simulated designs are manufactured and measured. It is seen that there are good agreements between measurement and simulation results.

Millimeter wave short range radar system design

In this paper, a 24 GHz millimeter wave (mm-wave) short range radar system is presented. In the designed radar system, there is one transmitter and one receiver channel. The transmitter channel has +9 dBm output power and 24 GHz output carrier signal is modulated with 20 ns square wave by SPDT switch. At the receiver channel, there are two LNAs, which have totally 40 dB gain, a microstrip band pass filter (BPF) and a double balanced IQ mixer. The designed radar system is measured using an oscilloscope at output of IF channel. According to the results, it is seemed that 200 mV and 50 mV reflection levels are received from metal and human target, respectively, at 2 meters without IF amplifier. ADE reflector antennas and horn antennas are utilized for transmitting and receiving.

Microstrip SIW patch antenna design for X Band Application

In this paper, designs of both circular and octagonal microstrip patch antennas are presented on the Substrate Integrated Waveguide (SIW) for X- Band Applications. Both antennas are modelled and simulated using the full -wave simulator CST MWS. It can be concluded that the proposed antenna designs are able to achieve high gain and directivity with the miniature, compact, light, cost effective and easy to fabricate structures.

Frequency-selective surfaces to enhance performance of TEM horn antenna

This article presents the analysis and investigation of the effect of loading a TEM horn antenna with a frequency selective surface (FSS) of finite size. It is simulated on FR4 (lossy) of relative permittivity 4.4, thickness 1.58mm and loss tangent 0.0035. This structure is called a filtering antenna (filtenna). Basically it is applied for filtering and minimizing the interference and noise in the desired band. The filtration is carried out using a finite FSS of double square loop of overall dimensions 20mm×20mm. The structure is simulated using CST MWS.