C.Y. Ng

Analysis and design of a high-performance planar Marchand balun

This paper presents an enhanced Marchand balun that offers excellent amplitude and phase balance performance. The enhanced Marchand balun is designed using compensated coupled lines. It employs capacitive compensation, a renowned technique for compensating the unequal even- and odd-mode phase velocities encountered in parallel-coupled microstrips. Analysis carried out in this study has proven that the finite directivity of coupled lines significantly affects the balun performance. The proposed capacitively-compensated Marchand balun is demonstrated at 2.1 GHz and has offered excellent results.

On miniaturization isolation network of an all-ports matched impedance-transforming Marchand Balun

A technique for reducing the isolation networks size in a Marchand balun needed for perfect all-ports matching and isolation is proposed in this letter. The proposed isolation circuit is realized using a coupled-line phase-inverter in place of the bulky 180/spl deg/ line section that has been previously proposed. Analysis of the proposed circuit yields the required relationship between the coupling coefficient and the electrical length of the coupler. Based on the design equations, the circuit is experimentally demonstrated at 1.8 GHz and has shown excellent results.

X-band microstrip bandpass filter using photoimageable thick-film materials

The rapid growth in commercial microwave technology, particularly for wireless communication, has created a demand for low-cost, high quality microwave fabrication technologies that are also suitable for high volume production. Modern thick-film materials are well placed to meet these requirements, in that they offer low conductor and dielectric losses, with good surface finishes and the ability to realise fine conductor geometries. This paper studies the feasibility of realizing microwave bandpass filters using thick-film photoimaging techniques. This enhanced thick-film technology can realise very narrow line width and spacing, giving performance comparable to the more expensive thin-film techniques. This is an inexpensive and mature technology, which looks set to revolutionize the manufacturing of microwave and MM-wave circuits in the near future. The fabricated filter achieved an insertion loss of only 0.7 dB over the frequency range of 9-11 GHz.

Miniaturised and multilayer Wilkinson divider and balun for microwave and millimeter-wave applications

Two miniaturised passive circuits, lumped-distributed Wilkinson divider and the all-ports matched impedance transformer based on Marchand balun are proposed. Applying a shunted input capacitor and RC isolation network, the Wilkinson divider size is arbitrarily reduced. For the all-ports matched Marchand balun, a proposed isolation network has been applied to reduce the whole size. These two circuits were designed and simulated based on 2.5D electromagnetic simulation software package. Excellent results of X-band lumped-distributed Wilkinson and W-band CPW balun were achieved.

A balanced vector modulator for LMDS applications

The design and performance of a monolithic microwave I-Q type vector modulator operating at 26 GHz is presented. The MMIC chip which measures 1.75 mm /spl times/ 2.1 mm, employs direct carrier modulation to reduce hardware complexity and cost. The static constellation was obtained with swept bias voltage control, with this, modulation of 16-quadrature amplitude modulation (QAM) is demonstrated. Baseband input levels were applied at 2.5 MSample/s, by an arbitrary waveform generator to demonstrate a 10 Mbits/s data rate transmitter operating at 26 GHz.

Miniature Ka-band I/Q vector modulator using 3D-MMIC technology

A 3D-MMIC I/Q vector modulator for direct multilevel modulation at 38GHz is reported. The experimental 3D-MMIC process developed at Bookham Technology (Caswell) offers 5 metal layers with BCB dielectric, making it possible to miniaturise the passive components using the lumped-distributed technique, overlaid couplers and TFMS lines. This approach offers compactness and easy implementation as compared to the planar forms. The modulator measures only 1.9 × 0.9mm2 and achieves an exceptionally precise tuning response leading to a near-ideal square constellation plot, making the modulator suitable for advanced signal processing and modulation techniques.

Design of Planar and 3-D Components using Photoimageable process

For improved interconnection and 3D structure design, low cost manufacturing solution is possible using thick film photoimageable technology. This improved thick film processing technique made integration between planar circuit, 3D circuit and active components realizable on a single module, while reducing the cost and increasing component count. Further investigations are in development stage to design applications especially in satellite and telecommunication module.

A 140 GHz Wilkinson power divider/combiner

A 140 GHz Wilkinson power divider/combiner using microstrip is presented in this paper. The measurements are made using an on-wafer TRL calibration technique from 140 to 220 GHz. The fabricated single-stage power divider occupies an intrinsic area of 0.5 mm/spl times/0.5 mm, achieved an insertion loss of 4.0/spl plusmn/0.4 dB and isolation and port return losses better than 12 dB over a 20 GHz operational bandwidth. Measured results achieved are in good agreement with the simulations.

Reflection-Type Bi-Phase Amplitude Modulator with Improved Performance Using Feedback

The analogue reflection-type attenuator using FETs as variable resistance reflection terminations is widely used as a bi-phase amplitude modulator for digital communication. However, FET parasitics cause considerable performance degradation in terms of amplitude and phase error in the signal constellation. In this paper, it is shown for the first time that simple resistive feedback can be applied to the standard modulator to improve performance dramatically. The analysis of the technique is presented, along with practical results for a 900 MHz demonstration circuit.