CiteULike: dcastros Eccleston

Investigation of a tessellated meta-material planar circuit

KW Eccleston — 2008-06-11T20:26:56-00:00

Microwave Conference, 2006. APMC 2006. Asia-Pacific (2006), pp. 927-930.

In this paper we investigate the propagation behavior of a square shaped planar meta-material guiding structure comprised of left-handed and right handed square unit cells each of the same size and arranged in a checker-board tessellation. The size of the planar structure is 19 cells by 19 cells and each cell is 8 mm by 8 mm. At 1 GHz, the left-handed unit cells have an insertion phase of 11deg and the right-handed unit cells have an insertion phase of -11deg. Both types of cells have the same Bloch impedance. The structure was fed at the centre unit cell, and there are a total of 76 peripheral ports each terminated in matched loads. At 1 GHz the power to each peripheral is equal and the phases at each port alternate between two values that differ by 11deg. Moreover, the planar structure exhibits the so-called infinite wavelength phenomenon in two dimensions and could be used in place of a circular radial power divider.

Optimum design of small-signal microwave amplifiers with specified stability safety margin

KW Eccleston — 2008-05-09T23:55:47-00:00

Microwave Conference, 2000 Asia-Pacific (2000), pp. 863-866.

When employing conditionally stable transistors in microwave amplifier design, it is impossible to have both parts perfectly matched. One can easily design for a perfect match at one of the parts, but the resulting mismatch at the remaining part may be unacceptable. Through trial and error using graphical methods, the designer may trade-off the perfect part match for improved match at the other part. In this paper, we propose a systematic approach whereby the maximisation of an objective function results in maximum gain and part match, for given stability safety margins

Stability safety margin based design of low noise microwave amplifiers

KW Eccleston — 2008-05-09T23:51:31-00:00

Microwave Conference, 1999 Asia Pacific, Vol. 1 (1999), pp. 1-4 vol.1.

In low noise microwave amplifier design, particularly when using conditionally stable transistors, it is impossible to simultaneously achieve maximum gain, minimum noise figure and maximum port match. Hence it is necessary to trade-off these performance parameters which is usually accomplished with the aid of stability, gain, noise figure and mismatch (or VSWR) circles described on the reflection coefficient planes. However, use of these graphical aids is often subjective, necessitating final optimisation using circuit design software. In this paper, we propose a different approach whereby the functional behaviour of two objective functions involving gain, noise figure and port mismatch are described as functions of the stability safety margin. This approach leads to an optimum design without requiring sophisticated optimisation algorithms and includes stability safety margin as a design parameter

Method for determination of parasitic resistances in microwave power MESFETs

KW Eccleston — 2008-05-06T18:33:16-00:00

Circuits, Devices and Systems, IEE Proceedings G, Vol. 136, No. 6. (1989), pp. 358-360.

A novel method of determining the source and drain series parasitic resistances of the MESFET is presented. This method is particularly suited to power devices since it eliminates the necessity to operate the Schottky gate with high forward bias. In addition, the values of parasitic resistances extracted from low-frequency measurements are confirmed at microwave frequencies.<<ETX>>

Nonlinear-dispersive GaAs FET drain-current model for harmonic balance simulation

KW Eccleston — 2008-05-06T18:33:12-00:00

Microwave Conference Proceedings, 1997. APMC '97, 1997 Asia-Pacific (1997), pp. 717-720 vol.2.

Popular GaAs FET large-signal drain conduction current models depend only on instantaneous terminal voltages, and ignore important phenomena that result in low frequency dispersion. To be valid at microwave frequencies, both the DC and time-varying components of current must be accurately modelled. This paper proposes a GaAs FET drain current model, which includes rate-dependent body and thermal effects, and therefore has the capability to accurately predict both the DC and time-varying components of drain current. Further, this model is particularly suited to harmonic balance simulation of microwave circuits

Consequences of port mismatch and finite isolation on power combining

KW Eccleston — 2008-05-06T18:33:10-00:00

Singapore ICCS '94. Conference Proceedings., Vol. 1 (1994), pp. 246-250 vol.1.

In solid-state power amplification, power combining is an important issue since the output powers from individual transistors are too small for many transmission applications. An important aspect of power combining is the combining efficiency being the ratio of the power delivered to the load to that available from the sources connected to the input. In a practical power combiner, waves incident on the input ports are scattered to all ports including the output port. The paper discusses the effects of port mismatch and finite combiner isolation on combining efficiency. For a lossless power combiner, it is shown that the efficiency may be optimised by optimising the matching at the combiner output

Analysis of the dual-fed distributed power amplifier

KW Eccleston — 2008-05-06T18:33:09-00:00

Microwave Conference, 1999 Asia Pacific, Vol. 3 (1999), pp. 638-641 vol.3.

The dual-fed distributed amplifier is a variation of the conventional single-fed distributed amplifier. Namely, the input signal is fed to both ends of the input line and the power appearing at the ends of the output line is combined. This approach has the advantages of utilising power in both the forward and backward travelling waves on the output line, and the drain output power can be equalised among the FETs. In this paper, the operational behaviour of the dual-fed distributed power amplifier is investigated and the optimum operating conditions are identified. It has been shown that uniform power distribution can be achieved when the spacing between each FET is of the order of the guide wavelength and is dependent on the phase difference of the two input signals

Multiband power amplifier for multiband wireless applications

KW Eccleston — 2008-05-06T18:33:07-00:00

Microwave and Millimeter Wave Technology, 2002. Proceedings. ICMMT 2002. 2002 3rd International Conference on (2002), pp. 1142-1145.

RF sub-systems in multimode/multiband wireless communication systems need to operate on different bands that are typically narrow but sparsely separated. We show that a single-ended dual-fed distributed amplifier can operate efficiently over several sparsely separated bands. This approach therefore alleviates the need for separate amplifiers for each band.

Class-B balanced single-ended dual-fed distributed power amplifier

O Kyaw — 2008-05-06T18:33:06-00:00

Microwave and Millimeter Wave Technology, 2002. Proceedings. ICMMT 2002. 2002 3rd International Conference on (2002), pp. 919-922.

The distributed amplifier approach allows the output powers of several FETs to be combined without the need for multi-way power combiners. In this paper we demonstrate that a balanced amplifier employing two single-ended dual-fed distributed amplifiers can operate effectively under class-B operation. Class-B operation and dual-feeding allow distributed amplification with significantly improved efficiencies compared to conventional distributed power amplifiers. The FETs are spaced 180 degrees to allow all FETs operate into identical optimum loadlines. The configuration uses all FET output power and has good port match.

Design considerations for the dual-fed distributed power amplifier

KW Eccleston — 2008-05-06T18:33:03-00:00

Microwave Conference, 2000 Asia-Pacific (2000), pp. 205-208.

The dual-fed distributed amplifier is a variation of the conventional single-fed distributed amplifier whereby the input signal is fed to both ends of the input line using a hybrid, and signals appearing at both ends of the output line are combined using another hybrid. Such a configuration allows utilisation of output power in the backward as well as forward waves. Much of the previous work in the literature only considered small-signal analysis and small electrical spacing between FETs, and did not lend insight into the operational behaviour. This paper therefore considers the development of a design method for the dual-fed distributed power amplifier with large electrical spacing. The simulations demonstrate optimum loadlines are achieved for all FETs and that all FET output power is utilised

Compact dual-fed distributed power amplifier

KW Eccleston — 2008-05-06T18:31:05-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 53, No. 3. (2005), pp. 825-831.

The dual-fed distributed amplifier (DFDA) allows efficient combining of field-effect transistors (FETs) at the device level without using n-way power combiners. However, the FETs must be spaced 180/spl deg/, resulting in physically large circuits. In this paper, meandered artificial transmission lines (TLs) comprised of microstrip lines periodically loaded with short open-circuit stubs can be used in place of TLs to reduce the size. The approach incorporates FET input and output capacitances with the artificial TLs, thereby eliminating their detrimental effects on bandwidth and performance. Both simulation and experimental results of a class-A three-FET single-ended DFDA designed to operate at 1.8 GHz demonstrate the feasibility of this approach and the validity of the design method. The size reduction is approximately one-third compared to realization using microstrip lines only, and the maximum efficiency is greater than 35% over a bandwidth of 15%.

Design and performance of a balanced single-ended dual-fed distributed power amplifier

KW Eccleston — 2008-05-06T18:31:02-00:00

Microwave Conference, 2001. APMC 2001. 2001 Asia-Pacific, Vol. 3 (2001), pp. 1187-1190 vol.3.

In this paper we demonstrate a design method for the balanced amplifier employing two single-ended dual-fed distributed power amplifiers. The method ensures that all FET output power is utilised, all FETs have equal output power at the centre frequency and operate into identical, optimum loadlines. The amplifier has improved efficiency compared to the conventional distributed amplifier and has improved input and output match compared to the dual-fed distributed amplifier

Compact planar microstripline branch-line and rat-race couplers

KW Eccleston — 2007-11-20T08:39:30-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 51, No. 10. (2003), pp. 2119-2125.

Both branch-line and rat-race couplers are easily realized using planar circuit technology as they employ only transmission lines without additional components. However, as the electrical lengths of the transmission line elements are either 90/spl deg/ or 270/spl deg/, such couplers consume a significant amount of circuit area. This paper shows the development of branch-line and rat-race couplers that use artificial transmission lines (ATLs) in place of conventional transmission lines resulting in significant size reduction. As the ATLs are constructed entirely from microstriplines, the couplers are easily fabricated using conventional printed-circuit processes. The design formulas developed for the ATLs are explicit. Full-wave simulation and experimental results were used to confirm the design approach for hybrids operating at 1.8 GHz. The frequency response of the proposed hybrids is similar to conventional hybrids.