Siti Zuraidah Ibrahim

Directional and wideband antenna for ground penetrating radar (GPR) applications

This paper presents a directional and wideband antenna for ground penetrating radar (GPR) applications. The antenna is designed by introducing slots on bowtie patch. The design is implemented on FR4 board with dielectric constant of 4.7 and thickness of 0.8 mm. As a result of having thinner substrate, the design is compact and light weight. The bowtie antenna performance is investigated across 0.5 GHz to 3 GHz. The parametric study of the length and location of slot are also demonstrated in this paper to obtaining the best return loss across widest operational bandwidth. The both simulated and fabricated antenna bandwidth are more than 50% (fractional bandwidth). The additional reflector is included at the back of bowtie antenna in the simulation for obtaining directional radiation pattern and high gain. The comparison between simulated and measured reflection coefficient is also presented.

Tuneable dual-mode narrowband bandstop filter using loaded microstrip resonator

Novel tuneable dual-mode narrowband bandstop filter using loaded microstrip resonator is presented. The filter is designed by using coupled line coupling with the microstrip resonator. There is two different pair of loaded resonator that produces a dual band bandstop filter. The dual band bandstop resonance frequency can be tuned independently by adjusting the resonator width and length. To achieve high selectivity of the bandstop filter response, defected ground structure (DGS) is applied in the filter layout. The tapped lines structure (TLS) are used to suppress second harmonic frequency. The dual band bandstop filter is resonant at 2.4 GHz with 200 MHz of bandwidth and 5.8 GHz with 300 MHz of bandwidth. The bandstop filter layout is fabricated on RO 4003C with 0.508 mm of substrate thickness. It is compact dimension with 19.6mm × 38.8mm. The advantages of this bandstop filter are simple layout and it can be tuned to the specified frequencies.

QPSK modulation using multi-port device

This paper investigates digital modulation transmitter using multi-port device. The multi-port device is a 6-port replacing the high cost mixer in conventional transmitter. The main objective of this paper is to develop the digital modulator based on six-port network using Agilent ADS (Advanced Design Simulation) simulation tool. The S-parameters of a fabricated six-port network are measured using network analyzer. All the 2-port measured data of the six-port network are then mapped into matrix 6×6 by using MATLAB. The mapped 6×6 matrix is then used to model the six-port network in ADS simulation. The six-port network can be functioned as a digital modulation by connecting port 1 to local oscillator and port 3 to port 6 to either open and short termination. The RF modulated signal is going out from port 2 of the six-port network. The QPSK (Quadrature Phase Shift Keying) symbols are dependent on the combination of open and short terminations which are controlled by SPDT (Single Pole Double Throw) switches. The simulation and analysis of the output result are observed in terms of symbol rate and frequency of local oscillator.

The Design of Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) Reader Antenna

This paper presents the design of ultra-high frequency (UHF) radio frequency identification (RFID) reader antenna using low dielectric constant of microwave substrate. An RFID reader antenna emits electromagnetic signals to the microchip in the tag, and the microchip will be energized by modulating the wave and returns to the reader antenna. The process of wave emitting is known as backscattering due to the presence of tag been detected by the reader. High-dielectric constant substrate, for example flame-retardant-4 (FR4) which is commonly used for microstrip patch antenna, is high in dielectric constant and dielectric loss. Thus, this will lead to low gain and directivity properties of the antenna. To overcome this matter, low-dielectric constant substrate which is Taconic TLY-5 was proposed to be utilized for microstrip patch antenna design. The TLY-5 microstrip substrate thickness used is 1.6 mm, dielectric constant of 2.2, and loss tangent of 0.019. A high-conductivity metal which is typically a conductive copper is been used for the two layers of dielectric substrate, the top radiating patch layer and bottom ground layer where the copper thickness is 0.035 mm. Microstrip feed line is used for this UHF RFID reader antenna. The width of the feed line was tuned to obtain impedance matching of 50 Ω. The proposed antenna which is fork-shaped patch antenna was simulated using Computer Simulation Technology (CST) and Microwave Studio software at resonant frequency of 910 MHz with the outcome results of 7.985 dB gain and −11.11 dB return loss. Nevertheless, the typical value obtained for VSWR is less than 2.

MINIATURE TRIPLE-MODE DIPLEXER WITH GOOD SELECTIVITY

This paper presents a compact diplexer with high selectivity. The proposed diplexer employs two sets of triple-mode bandpass filters. Using this approach, the pair of even-mode resonant frequencies can be flexibly controlled by adjusting the characteristic impedance or electrical lengths of the two open-circuited stubs while the odd-mode resonant frequency remains at the fundamental resonant frequency. For a demonstration, a diplexer with two passbands centred at 1.50 and 1.70 GHz and the transmission zeros are created close to the passband edges which extremely improve the skirt selectivity. As a result, the proposed diplexer occupies an extremely small area, i.e., approximately 0.30λg × 0.35λg . The measured results are in good agreement with the simulated predictions.

Miniature microstrip bandpass filters based on quadruple-mode resonators with less via

This article aims to design of microstrip resonators in order to reduce size of microstrip bandpass filters in wireless communication systems. Characterized by both theoritical investigation and full-wave simulation, the proposed bandpass filters are designed consist of dual-band bandpass filters and quadruple mode bandpass filters with miniaturized size. The proposed filter is found to have benefits such that the even-mode resonant frequencies can be flexibly controlled while the odd-mode resonant frequency is reserved for the fundamental frequency. Since the structure of resonators is realized using common via holes, the difficulty and complexity of the fabrication process can be shortened. In order to achieve compact size, the total number of resonators is reduced so that the implemented resonators only occupy a small area.

Development of six-port baseband processing system for short range radar based sensor

This paper presents the development of the six-port baseband processing system for short range radar based sensor. Short range radar involved in many applications such as the used in the automotive system. The analog baseband circuit commercially exists nowadays, but it a little bit bulky and expensive. In this paper, the design of a RF power detector using microstrip technique is presented. The design of diode detector circuit is simulated using Keysight ADS software tool. The design of the diode detector includes the matching network, RF choke and the low pass matching. When the design of diode detector completed, the development of baseband processing system is accomplished using microcontroller board. The algorithm of obtaining Direction of Arrival (DOA) phase wave is executed using microcontroller board. The details of the theory, simulation and results are presented in this paper.

Target direction finding using port technique for short range radar based sensor

This paper presents a target direction finding using six-port technique for short range radar based sensor. Direction finding of the target is determined by performing phase measurement of the incident wave at the receiver side. This technique is also known as Direction of Arrival (DOA) detection method. In this paper, the operation of target direction finding is performed and simulated using Keysight Advanced Design Studio (ADS) simulation tool. The six-port device is modelled in ADS using measured scattering parameters (S-parameters). To convert the received RF signal to baseband signal, RF power detector is also designed and simulated independently in ADS. The simulated results of each stage is discussed and presented in this paper.

Development of branchline coupler using parallel coupled transmission lines

This paper investigates the development of branchline coupler using parallel coupled transmission lines on planar microstrip using CST Studio Suite 2010 design tool. This project operates within 4 GHz to 8 GHz frequency band. Two designs are proposed in this project which are basic branch line coupler and branch line coupler with parallel line feeding technique. The main purpose of this study is to improve bandwidth while compare the performance of both designed coupler. The designs are then investigated using CST Microwave Studio simulation tool. The designs are fabricated on microstrip printed circuit board and measured using vector network analyzer. The simulated and experimental results of both developed couplers are compared and analyzed. The overall simulated percentage bandwidth of the proposed coupler is covered from 4 to 8 GHz with percentage bandwidth of 32.32%.

Compact low pass filter with deep and wide stopband using H-shaped defected microstrip structure

A deep attenuation level and wide stopband bandwidth, sharp roll-off and low insertion loss in the passband using H-shaped defected microstrip structure (DMS) at open circuit stub resonator (OCSR) of the stepped-impedance low pass filter (SILPF) is presented in this paper. The proposed filter consists of H-shaped that is etching at the microstrip line of OCSR. The OCSR is embedded in the middle of high impedance line of the SILPF. The effect of the applying H-shaped DMS is investigated through parametric studies by comparing H-shaped with Y-shaped and U-shaped. It is observed that the comparison with conventional SILPF shows that the proposed modification filter exhibit a deep and large rejected band of 27 dB attenuation level from 8.21 GHz to 23.16 GHz up to 3 fc. The proposed filter also offers sharp roll-off at 7.31 GHz cut-off frequency and maximum ripple value in the range of DC to 6 GHz is less than 0.35 dB.