Mohd Nizam Osman

Fabrication and Characterization of PZT Thin Film Capacitors for MMIC Applications

This paper reports on the use of thin lead zirconate titanate (PZT) films for monolithic microwave integrated circuit (MMIC) capacitors to replace existing materials for better size-reduction. The films were sputtered on Pt/Ti/SiO2 coated, undoped silicon wafers. Square Pt electrodes with sides ranging from 10 mum to 50 mum were patterned on the PZT layers to form the capacitors. Results of this study show that PZT thin films can be utilized for efficient size reduction in MMIC. The linewidth obtained for a 50 Omega transmission line is merely 300 nm - this results in a size reduction of approximately five times compared to conventional MMIC. For a 50 times 50 mum electrode area, capacitance values ranging from 5 to 20 pF were obtained at frequencies up to 20 GHz. Suitable de-embedding of S parameters using Cascade microwave probes revealed films with relative permittivities of the order of 100 to 500

Effect of Laser Bias Current to the Third Order Intermodulation in the Radio over Fibre System

Third order intermodulation (IM3) can cause non-linearity effects which result in interference and crosstalk between the subcarriers in radio over fibre (ROF) transmissions. This paper presents the experimental results of the effect of varying the magnitude of the laser bias current on the IM3 in an ROF system with direct modulation. We also investigate the behaviour of the system spurious free dynamic range (SFDR) with the bias current variation. The results show that there will be an optimum bias current range for a given range of the radio frequency (RF) input power in order to minimise the IM3 effect and obtain the best possible SFDR for the system

Fabrication and Characterization of Planar Dipole Antenna Integrated with GaAs Based-Schottky Diode for On-chip Electronic Device Application

The design and RF characteristics of planar dipole antennas facilitated with coplanar waveguide (CPW) structure on semi-insulated GaAs are performed and confirmed to work in super high frequency (SHF) range. As expected, the fundamental resonant frequency shifts to higher frequency when the length of antenna decreases. Interestingly, the resonant frequencies of antenna are almost unchanged with the variation of antenna width and metal thickness. It is shown experimentally that return loss down to −54 dB with a metal thickness of 50 nm is obtainable. Preliminary investigation on design, fabrication, and DC and RF characteristics of the integrated device (planar dipole antenna + Schottky diode) on AlGaAs/GaAs HEMT structure is presented. From the preliminary direct irradiation experiments using the integrated device, the Schottky diode is not turned on due to weak reception of RF signal by dipole antenna. Further extensive considerations on the polarization of irradiation etc. need to be carried out in order to improve the signal reception. These preliminary results provide a new breakthrough for on-chip electronic device application in nanosystems.

Gain and cut-off frequency analysis of multiple-gated AlGaAs/InGaAs HEMTs

A small signal analysis was performed on a specific 0.2 mum HEMT device to study the impact of multiple-gated layout towards the gain and cut-off frequency performance. The characterization process was using on-wafer measurement technique to AlGaAs/InGaAs HEMT devices which consisted of three types of layouts of various gate finger numbers and widths. The devices were biased at the optimum basing voltage obtained from DC characterization performed previously. From the result, it was observed that the device with higher number of gates exhibited higher gain only at low frequency, while at higher frequency the gain dropped significantly. This significant drop in gain was due to the increase of the gate-source capacitance in the device, thus leading to a reduction of the device cut-off frequency. The experimental findings were strongly supported by simulation which was based on related theory on the layout dimension contribution.

The Impact of Multiple-Gated Layout on the Drain-Source Current of pseudomorphic-HEMTS

The measurement and analysis to search the impact of multiple-gated structure of a GaAs based p-HEMT device towards the drain-source current (Ids) is presented here. The experimental works had been carried out on the GaAs wafer that consists of 2times60, 4times75 and 6times150 p-HEMT device layouts for the I-V characteristic. The I-V measurement was performed using on-wafer probing technique which applied semi-auto probe station and Keithley parameter analyzer to extract I-V curve. From the I-V data, it was found that the p-HEMT layout that had higher number of gates exhibited a significant impact on the Ids at the same Vgs bias value. The Ids of six-gated layout was improved about 40% as compared to 4-gated layout and about 60% to 2-gated layout. The effect on the I-V performance due to the number of gates in the layout has also been discussed in detail for circuit design applications

Fabrication and Characterization of n-AlGaAs/GaAs Schottky Diode for Rectenna Device Application

Schottky diode was designed and fabricated on n-AlGaAs/GaAs high electron mobility transistor (HEMT) structure for rectenna device application. Rectenna is one of the most potential devices to form the wireless power supply which is really good at converting microwaves to DC. The processing steps used in the fabrication of Schottky diode were the conventional steps used in standard GaAs processing. Current-voltage (I–V) measurements showed that the device had rectifying properties with a barrier height of 0.5468 eV for Ni/Au metallization. The fabricated Schottky diode detected RF signals and the cut-off frequency up to 20 GHz was estimated in direct injection experiments. These preliminary results will provide a breakthrough for the direct integration with antenna towards realization of rectenna device application.

Characterization of wideband square spiral inductors based on 0.15 µm GaAs pHEMT technology

This paper reports on the characterization of non-scalable square spiral inductors based on 0.15 µm GaAs pHEMT technology. The effect of number of turns on the electrical characteristics of the spiral inductors were characterized up to 40 GHz with inductances values obtained from 0.241 to 2.436 nH. The inductance and self resonant frequency (SRF) of the square spiral inductors were determined by S-parameter simulations from the Smith chart. Results show that the spiral inductors have resonance frequencies ranging from 13.52 GHz to more than 30 GHz for spiral inductors values from 2.436 nH to 0.241 nH. Using tune-tank circuit topology, the Q factor obtained for the spiral inductors have values ranging from 11 to 16. The spiral inductors behavior was finally represented by a π-network equivalent circuit based from on-wafer S-parameter measurement.

Development of 2.4 and 3.5 GHz 0.15 μm GaAs PHEMT medium‐power amplifier employing core‐based design approach

Purpose – The purpose of this paper is to discuss medium‐power amplifier (MPA) design using parasitic‐aware core‐based approach.Design/methodology/approach – This paper discusses a core‐based design approach, which can also deliver multi‐band radio frequency integrated circuit.Findings – A fabricated 3.5u2009GHz MPA achieved a P1dB of 16.81u2009dBm, power‐added efficiency (PAE) of 16.74 percent and gain of 6.81u2009dB at the 10u2009dBm of input power under a low‐power supply of 3u2009V. The maximum current, Imax is 80.7u2009mA and the power consumption of the device is 242.10u2009mW. A fabricated 2.4u2009GHz MPA achieved a P1dB of 14.83u2009dBm, PAE of 11.73 percent and gain of 9.83 dB at the 5.0u2009dBm of input power under a low‐power supply of 3.0u2009V. The maximum current, Imax is 84.4u2009mA and the power consumption for this device is 253.20u2009mW.Originality/value – This paper shows the merits of the parasitic‐aware design methods used in designing the core circuit.

The effect of multiple gate for P1dB and PAE of AlGaAs/InGaAs HEMT

The impacts of numbers of gate fingers on large signal of High Electron Mobility Transistor (HEMT) were studied in this paper. The analysis was carried out measurement using Maury Automated Tuner System (ATS) at frequency of 2.4GHz and 5.8GHz. The measurement results shows that the transistor that has higher number of gate fingers is less preferred for high P1dB compression and Power Added Efficiency (PAE) performance. This is due to the parasitic existed in larger transistors that cause P1dB and PAE to drop significantly. Moreover, higher input impedance of the transistors further contributions to the degradation of these performance indicators. Finally, the optimum transistors is proposed.

Short-range point-to-point gigabit wireless transmission at 50 GHz

In this paper, we present a short-range point-to-point gigabit wireless transmission at 50 GHz utilising prototypes of simple transmitter and receiver front-ends. The particular prototypes have been assembled from millimetre-wave (MMW) components with WR15 and coaxial ports. The MMW transmitter generates an amplitude shift keying (ASK) modulated signal by mixing a polar non-return-zero (NRZ) of pseudo-random binary sequence (PRBS) with a word length of 211−1 and a local oscillator (LO) signal of 50 GHz. MMW coherent receiver with a low-pass filter has been employed to demodulate the ASK signal. For the digital baseband transmission at 50GHz, a BER of 10−11 has been achieved for 3.125Gbps wireless transmission with received RF power greater than -61dBm. The prototype MMW receiver imposes 3dB sensitivity penalty when bit rate is increased from 2.125 to 3.125Gbps.