Achmad Munir

Microstrip patch antenna miniaturization using artificial magnetic conductor

This paper deals with an alternative technique for microstrip patch antenna miniaturization is investigated. The technique employs a 2 layer structures with an artificial magnetic conductor (AMC) structure used as the bottom layer replacing the ground plane. The AMC structure is constructed using a textured high impedance surface (HIS) that takes form of a doubly periodic square patches on top of a dielectric substrate. The miniaturization effect that is introduced especially in the reduction of patch size by use of this 2 layer structures will be numerically investigated. The proposed antenna is designed to have a resonant frequency of 2.45MHz suitable for wireless local area network (WLAN) application and is deployed on an FR-4 Epoxy substrate. To obtain the optimum design, numerical analysis is carried out using 3D simulation software. To verify the miniaturization effect, the proposed antenna will be compared to some reference antenna resonates at the same resonant frequency placed on a 2 layers FR-4 Epoxy substrate with the same thickness but without AMC structure. From the result, it is shown that the incorporation of AMC structure can reduce the size of antenna patch by more than 31%.

GNU Radio based software-defined FMCW radar for weather surveillance application

In this paper, a GNU Radio based software-defined FMCW (Frequency Modulated — Continuous Wave) radar is studied for weather surveillance application. The FMCW radar that has been gaining popularity due to the use of solid state microwave amplifier to generate a signal source is proposed for the design since the current weather surveillance radar is usually using a pulse-radar type that needs high power in pulse generation and high cost in the deployment. In addition, by using software-defined radar, therefore the designed FMCW radar can be implemented and configured at a reduced cost and complexity. The FMCW radar prototype is implemented using both open sources of software and hardware. The software part of the radar is realized using GNU Radio, whilst the hardware part is implemented using USRP (Universal Software Radio Peripheral) N210. Based on the design specification, an FMCW radar prototype based on GNU Radio is then realized and examined. From the performance-test, the prototype that works at a center frequency of 2.1GHz with a bandwidth of 750kHz is able to perform range detection of targets after utilizing the FFT (Fast Fourier Transform) function using MATLAB. In addition, the discussion of system design of software defined FMCW radar and performance-test of its prototype are presented.

Tunable Frequency Selective Surfaces Characterisation

In this paper a new means for accurate characterisation of active varactor loaded frequency selective surfaces (FSS) is demonstrated. The varactor loaded active doubly periodic wire FSS acts as a variable impedance surface, in which its surface reflectivity and transmitivity can be modified by adjusting by d.c. bias voltage control. The properties of the active FSS are characterised using a specially designed parallel plate waveguide (PPW) simulator. This permits normal incidence excitation of the FSS under test over the frequency range of 2.6 GHz to 3.95 GHz. In addition we present a novel hybrid de-embedding technique to remove the influence the PPW simulator and reveal the true property of active FSS. Typical results are presented and validated against a new 3D EM modelling led de-embedding method for the composite FSS and PPW structure.

Development of microstrip BPF using open split ring resonator with square groundplane window

This paper presents the development of microstrip bandpass filter (BPF) using open split ring resonator (OSRR) incorporated with square groundplane window. The microstrip BPF is comprised of 2 pairs of 3 cascaded OSRR connected with microstrip lines. Here, the incorporation of square groundplane window underneath the OSRR is applied to improve the passband bandwidth response of proposed BPF. In the design process, some parametrical study is performed to optimize the BPF in achieving the optimum bandwidth response. The proposed microstrip BPF is then realized on a 0.8mm thick FR4 Epoxy dielectric substrate with the dimension of 35mm × 60mm. The measurement result shows that realized microstrip BPF has the bandwidth response of 1.12GHz ranges from 1.50GHz to 2.62GHz which is comparable with the design result.

Parallel plate waveguide simulator design, characterisation and DUT de-embedding

In this paper, a new hybrid measurement/3D EM simulation technique to obtain reflection and transmission properties of an FSS under normal incidence has been investigated. The measurement fixture, a specially designed PPW simulator operating with normal incidence excitation, can be very accurately computed by commercial 3D EM simulation. To reveal the de-embedded characteristics of the DUT, (in this paper a wire FSS), a de-embedding method employing half structure models has been performed. This results in good agreement with theoretical prediction.

Performance enhancement of directional coupler using split ring resonator

In this paper, a technique to enhance the performance of directional coupler is proposed by incorporating the structure of split ring resonator (SRR). The directional coupler which is conventionally design on a grounded dielectric substrate is reconstructed by inserting the structure of SRR between the microstrip lines and the groundplane. This construction is expected to improve the performance of directional coupler, i.e. reflectivity and transmitivity. The number of SRR incorporated in the structure is limited into 9 per line due to the available space of directional coupler. The proposed directional coupler with SRR is then deployed on 2 stacked layers of FR4 Epoxy dielectric substrate with total thickness of 1.6mm and the dimension of 130mm 53mm. Prior to the hardware realization, the geometry of SRR is investigated numerically to obtain the optimum performance of directional coupler. From the results, it shows that the measured results of reflectivity (11) and transmissivity (21) are comparable to the simulated results. The 11 value for each port is less than -20dB, while the 21 value is closed to -20dB. However, at some frequency ranges the measured results show the reflectivity less than -10dB and the transmissivity is more than -5dB.

G-patch dualband printed monopole antenna for GPS and WLAN application

This paper discusses numerical design and experimental characterization of dualband printed monopole antenna with center frequency of 1.6GHz and 2.4GHz. The antenna that takes a shape of G letter is proposed to overcome the special need of GPS and WLAN application. The antenna which is fed by microstrip line extended from a center pin of 50Ω connector type has 2 distinct arms in different length arrangements to obtain the desired different resonant frequencies. After obtained the appropriate numerical design, the antenna is then deployed on an FR4-Epoxy dielectric substrate with the dimension of 50mm × 50mm and the thickness of 1.6mm. From the measurement results, it shows that the characteristics of realized antenna have good agreements each other with the numerical design. The realized antenna is able to operate at dual frequency bands where the working bandwidths for lower and higher frequency band are up to 220MHz and 150MHz, respectively.

Printed multiband antenna for mobile and wireless communications

In this paper, a low profile printed multiband antenna is numerically investigated and experimentally measured. The antenna is proposed to be used for GSM-850, GSM-900, UMTS-2100, WiMAX-2.3 and WiMAX-3.3. It is developed from the existing tripleband microstrip antenna that works on frequency of 2GHz, 3.5GHz and 5.5GHz. To improve the coverage of frequency bands, the existing antenna structure is totally redesigned using FR-4 Epoxy substrate with permittivity of 4.3 and thickness of 0.8mm to produce a new antenna configuration that works at desired frequency bands. To have the proposed antenna to be as compact as possible, the meandering strip technique is applied to minimize the antenna dimension. Hence, to be possible being fed in planar, the microstrip line technique is used to feed the antenna. Prior to the fabrication, the proposed antenna is numerically designed in which some parameters of antenna including return loss, VSWR, bandwidth, gain, and radiation pattern are used as design indicators. Based on the design result, the antenna with total dimension of 32mm × 32mm is then realized to be experimentally characterized. From the measured result, it is shown that the proposed antenna has working bandwidths (VSWR<2) for frequency ranges of 800–920MHz, 1900–2400MHz and 3300–3420MHz that corresponds to frequency ranges of GSM-850, GSM-900, UMTS-2100, WiMAX-2.3 and WiMAX-3.3, respectively. In addition, the measurement results of antenna parameters show good agreements with the numerical results.

Unidirectional broadband microstrip antenna for through walls radar application

We present a design and simulation of broadband microstrip antenna with unidirectional radiation pattern for through walls radar application. Design and simulation with computer was confirmed the implementation of the proposed design. The results were validated by measurements in the laboratory. This research is a continuing from our previous research in developing antennas for through walls radar application. In previous research, we have developed a broadband microstrip antenna for through walls radar application in a bidirectional radiation pattern. Based on the laboratory experiment results, bidirectional radiation pattern still have weaknesses on detecting objects movement behind radar antenna. Unidirectional antenna has proven to have greater gain than bidirectional antenna. To obtain unidirectional radiation pattern antenna we added reflector behind the antenna to detect moving objects from in front of the antenna only. The previous bidirectional antenna for through walls application showed 4–5 dBi gain. In this research, the design and simulation of unidirectional antenna for through walls application showed 5.5 to 7.5 dBi gain. The unidirectional antenna will be printed using FR4 material with a dielectric constant and substrate thickness of 4.4 and 1.6 mm respectively. This antenna has a bandwidth of 1.5 GHz (66.67%) with frequency of 1.5 to 3 GHz.

Compact SRR-based microstrip BPF for wireless communication

A development of novel compact microstrip bandpass filter (BPF) made of split ring resonator (SRR) is presented. The proposed microstrip BPF is intended to be used for 2.4GHz wireless communication application. It is designed on a grounded 1.9mm thick high relative permittivity Roger RT/Duroid® 6010 dielectric substrate with the dimension of 25mm 25mm. Some parametrical studies to obtain the optimum design of filter are carried out by varying the width of rings as well as the gap of rings. From the measurement, it shows that the fabricated SRR-based microstrip BPF has a center frequency at 2.4GHz with -3dB bandwidth response of 130MHz ranges from 2.34GHz to 2.47GHz. Although the measured -3dB bandwidth response is 30MHz narrower than the simulated one, however the prototype of microstrip BPF has satisfied specification required for wireless communication application.