Ooi Ban Leong

A novel Doherty amplifier for enhanced load modulation and higher bandwidth

We are reporting a new topology for the Doherty amplifier to increase its bandwidth and enhance the load modulation. A varactor-based impedance transformer has been employed to replace the bulky and narrowband quarter-wave impedance inverter. Load modulation is carried out adaptively using the proposed varactor-based structure based on the input power level. An envelope detector is employed for adaptive impedance transformation of the carrier amplifier as well as bias adaptation of the peak amplifier. Based on the proposed topology, a 2W Doherty amplifier has been fabricated using discrete pHEMT transistors and low loss varactors. In order to evaluate the broad-band/multi-band performance of the proposed topology, measurements have been carried out at three sample frequencies (1.8GHZ, 2GHz and 2.2GHz) over a 400 MHz bandwidth. Power added efficiency of better than 45.3% has been achieved at maximum power level and 6-dB power back-off and maintained over the entire bandwidth. Measured IM3 is better than −42.2dBc at P1dB of 33dBm for all design frequencies.

PLL based high speed functional testing

A PLL based at-speed functional testing concept, which eliminates the need for a tester-driven high-speed clock interface is presented. Jitter tolerance circuits have been implemented to provide immunity, to clock jitter. The concept was verified on a 100 mm/sup 2/ silicon device built in 0.18 /spl mu/m technology, above 200 MHz speed. Simulation results show that the concept can be extended to higher speeds.

A Miniaturized Wideband Wilkinson Power Divider

A miniaturized wideband Wilkinson Power Divider realized using OMMIC ED02AH Technology is presented. Simulation and optimization are accomplished by Advanced Design System (ADS). The final optimization results shows that it has a bandwidth of 76.5% (8.4 - 18.8 GHz), 1 dB insertion loss and good isolation (< -12 dB) between the output ports. The layout of the presented power divider is given, which shows that compacted size (0.75 × 0.45 mm2) is achieved successfully.

A new triple-band slot antenna with EBG feed

The use of photonics materials has been driving the relative theory to the propagation of optical waves. The theory of photonic band-gap (PBG) or electromagnetic band-gap (EBG) was developed initially for optical frequencies and can easily be applied to millimeters waves, microwaves and antenna. The PBG or EBG lattice can usually offer more flexibility to design the transmission line. Generally, EBG can diminish the propagation constant causing the wave to move slowly. In the relative researches, we have found that the EBG lattice can offer more flexibility to design the transmission line. The inductance and capacitance values of EBG can be adjusted by varying the dimensions of EBG lattice geometries, thus can effectively cancel the reactive part of the antenna impedance. If the spacing between CPW center conductor and ground remains the same, the optimization variables can be further reduced. Therefore, in this paper, we utilize the spiral EBG into the antenna design and attempt to achieve better antenna performances.

A scaling technique for partial element equivalent circuit analysis using SPICE

A scaling technique for partial element equivalent circuit (PEEC) analysis using SPICE is introduced in this letter. The perturbation series based scaling is applied to the component values extracted by the standard PEEC method to get up to an order of magnitude improvement in relative accuracy of scattering parameters with SPICE simulation. The effectiveness of the technique is verified by using the numerical example of a stripline structure and comparing the results with that of the method of moments (IE3D).

A novel circuit model for two-layer spiral inductor with Eddy current effects

In this paper, an improved two layered spiral inductor lumped-element circuit model, which takes into account the effect of eddy current within the silicon substrate, is proposed. Physical explanation on the modifications of the circuit is given. Compared to the conventional model, our proposed model provides a better agreement between the simulated and measured responses for a sample of circular spiral inductors fabricated using silicon substrate

Test bench modeling and characterization for fine pitch wafer level packaged devices

This work describes an interposer hardware for testing fine pitch wafer level packaged devices. It is built to handle multi-gigahertz signal propagation using 100 micron pitch GSG probes. All the components of the test hardware socket such as the SMA connectors, coplanar transmission lines on the PCB and trampoline mesh have been modeled. A sample chip, without bumps on the pads, has also been measured. The measurement and models demonstrate that the test socket performs at 5 GHz with an insertion loss of about 3dB.

Blind source separation and bearing estimation using Fourier- and wavelet-based spectrally condensed data and artificial neural networks for indoor environments

A new method for blind separation and bearing estimation of wavefronts in a smart antenna scheme, which is based on the usage of artificial neural networks (ANN) is presented here. Because of ldquothe curse of dimensionality,rdquo especially in the cases having many antenna elements, in uniform linear, circular or planar arrays, it is important to find a method which makes it feasible to use the ANNs. The proposed method, do not walk along the road of well-known method of correlation-coefficient training. In contrast this method uses the truncated version of their spectral representations. The fast Fourier transform (FFT) and discrete wavelet transform (DWT) are employed to provide the spectral representations. The simulation scenario is set up to demonstrate that the results is applicable to realistic cases such as urban, non-line of sight, and indoor environments. For the sake of this purpose, coherent signals are employed in simulations. In this case, most conventional methods are not applicable, because they are built on some statistical assumptions which implies that the received signals by array must be independent.

ENERGETICS OF COPPER NANOWIRES

The present work calculates the size dependent behaviour of Fermi energy, work function, and the ionization potential of finite copper nanowire by using a free electron model. A uniform conductor of finite length and a square cross section is assumed to model the copper nanowires. The energy spectrum of the wire is determined by solving the one-electron Schrodinger equation with the potential described by a square well potential. The details of size dependence of electronic characteristics of the copper nanowires are illustrated in this present work.

Efficient methods for inductance calculation with non-uniform current distribution in spiral inductor

Two efficient methods of inductance calculations for spiral inductor with special emphasis on the non-uniform current distribution on the metallic trace are presented. Based on the conventional magnetic flux method and the energy method, a unified approach for modeling the eddy current and skin depth of the spiral inductor has been presented. Our proposed method is validated with experimental results, and good agreement has been obtained