Mehmet A. Belen

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.

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.

Microstrip frequency selective surface for use in horn Filtenna

This work presents design of Microstrip Frequency Selective Surface (MFSS)s to be fixed into the apertures of horn antennas for pre-filtering unwanted signals at 4GHz, 9 GHz. Thus integration of the antenna and band-pass filter is achieved into a single module so that a pre-filtering process can be carried out when signal is received by the antenna that makes the entire system be more compact and improves its performance. Furthermore since MFSS s consist of simply identical microstrip patch arrays, this constitutes a feasible solution especially when the unwanted signals are exceptionally strong compared to the desired in-band signals, which make required front-end RF filter performance be more rigorous. All the designs and analysis have been completed by the full-wave EM simulator CST using low-cost FR4 with the relative permittivity 4.4, thickness 1.58mm, loss tangent 0.0035 starting from the unit element. The paper briefly reviews the design and simulation stages compared to the measurements made by our research group and published in [8], [9] and [10]. From the measured results within 4GHz-9GHz bandwidth, it can be found that the proposed modules keep return loss characteristics of the horn antennas, meanwhile enhancing gain and beam width to effectively attenuate interference and noise signals at the out-band. Besides, this methodology implemented to design horn Filtennas to filter GSM signals at 1800 MHz for radar application. All the horn Filtennas will be presented in details in the workshop.

Design of Dielectric Lens Loaded Double Ridged Horn Antenna for Millimetre Wave Application

In this paper, designs of Dielectric Lens Loaded Double Ridged Horn Antenna for Millimetre Wave Applications is investigated. Firstly a double ridged horn antenna is designed and simulated in CST environment. After that, 2 dielectric lens architecture are designed and placed at the aperture of the antenna. It is seen that by placing spherical shaped dielectric lens, it is possible to achieve improvement in return loss and farfield gain of the antennas design in a 20–40 GHz bandwidth.

Coplanar stripline-fed Microstrip Yagi-Uda antenna for ISM band application

In this paper, design and experimental results of a coplanar stripline fed Microstrip Yagi-Uda antenna are presented. The proposed antenna consists of a microstrip line to coplanar stripline transition, reflector microstrip patch, coplanar stripline-fed driver dipole, and three director microstrip patches on low-cost FR4 with the relative permittivity 4.4, thickness 1.58mm, loss tangent 0.025. The 10-dB bandwidth and gain are measured as 130 MHz at the center frequency of 2.45 GHz, 7.5 dBi.

Design and realization of dual band Microstrip Monopole antenna

Herein, design and experimental results of a dual band Microstrip Monopole antenna are presented. The proposed antenna consists of a zig-zag microstrip line as monopole patch alongside of a Defected Ground structure under the fed-line of the antenna for size miniaturization propose, fabricated on FR4. The 10-dB bandwidth and gain performances are measured as 130 MHz and 6 dB at the centre frequency of 2.42 GHz, and140 MHz, and 2dB at the centre frequency of 5.92 GHz respectively.

A deterministic approach for designing flat gain ultra-wideband LNAs

In this paper, a deterministic approach is presented for designing flat gain, ultra-wideband single - stage Low Noise Amplifier LNAs. The approach is based upon the solutions of the nonlinear noise F, input VSWR V_in and gain GT equations of the employed microwave transistor with respect to its stable source Z_S and load Z_L terminations for the performance (F(f)≥F_min(f), V_in(f) ≥ 1, G_Tmin(f)≤G_T(f)≤ G_Tmax(f)) triplets, where F_min(f) and G_Tmax,(min)(f) are the achievable minimum noise and maximum (minimum) gain at f of the bias condition V_DS,I_DS respectively. A Performance Data Bank PDB is constructed by the compatible performance triplets so that it can be conveniently used to design any LNA with the required gain, noise and input VSWR characteristics along the available operation bandwidth of the device. Even the bias condition (VDS, IDS) can be selected subject to the sensitivity requirements by adding a black-box artificial model of the transistor in front of the PDB. In this work, finally we present the two flat gain ultra-wideband LNA design alternatives with respect to the tolerance and bandwidth choices using the microwave transistor NE3509M04 together with their (Z_S, Z_L) termination couples.