Kimberley W. Eccleston

Compact planar microstripline branch-line and rat-race couplers

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.

Mode Analysis of the Corrugated Substrate Integrated Waveguide

The corrugated substrate integrated waveguide (CSIW) is compatible with substrate integrated waveguides (SIWs) but permits ease of integration of active devices. The CSIW differs from the SIW by using quarter-wave open-circuit stubs in place of vias to form the electric sidewalls. In this paper, an efficient analysis method has been formulated that distributes the loading effect of each stub across its width. The formulation was used to calculate CSIW dispersion characteristics and identify mode behavior in the vicinity of the desired TE10 mode. Simulations and measurements of X-band CSIWs were used to validate the calculations. Apart from normal waveguide mode behavior, surface wave-like behavior was also identified.

Compact dual-fed distributed power amplifier

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%.

Substrate integrated waveguide with corrugated wall

In this work we propose a new SIW structure, called the corrugated SIW (CSIW), which does not require conducting vias to achieve TE10 type boundary conditions at the side walls. Instead, the vias are replaced by quarter wavelength microstrip stubs arranged in a corrugated pattern on the edges of the waveguide. This, along with series interdigitated capacitors, results in a waveguide section comprising two separate conductors, which facilitates shunt connection of active components such as Gunn diodes.

Design considerations for the dual-fed distributed power amplifier

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.

Half-Mode Buried Corrugated Substrate Integrated Waveguide

A half-mode buried corrugated substrate-integrated waveguide is proposed. Its dominant mode propagation behavior is almost identical to that of the half-mode substrate-integrated waveguide but offers a floating top conductor thereby permitting active devices connected to its longitudinal open-edge to be biased without the need for extra biasing chokes. The corrugations comprise open-circuit stubs buried in the substrate that are connected to the top wall of the waveguide by vias. These stubs are quarter-wave in length at a frequency twice the dominant mode cut-off frequency. The corrugations and vias are used to obtain an electric wall. Burying stubs in the substrate results in a low stub input impedance over a wide bandwidth which allows a monomode bandwidth of 3:1 to be obtained. Experiments for waveguides with a TE0.5,0 mode cut-off frequency of 2.8 GHz demonstrate its effectiveness.

Implementation of a Microstrip Square Planar

This paper describes a compact square-shaped 20-way metamaterial power divider implemented in microstrip technology and lumped capacitors and inductors. The divider comprises 12 square tiles exhibiting left-handed behavior and 13 square tiles exhibiting right-handed behavior arranged in a checkerboard tessellation (or mosaic). The divider relies upon the infinite wavelength phenomena in two dimensions and this requires the left-handed tiles have an insertion phase between any two of its sides equal to, but with opposite sign, of that of the right-handed tiles. To achieve tessellation, both tile types must be the same size. The design method is based upon an analytic formulation, and was applied to the realization of a 20-way power divider operating at 1 GHz that uses surface-mount lumped components. The resulting divider was 50 mm by 50 mm. Over a 10% bandwidth, the measured insertion loss was less than 1.3 dB, the measured couplings track within plusmn1 dB and plusmn6deg , and the measured input port return loss and isolation was greater than 20 dB. This level of isolation was achieved without isolation resistors. Equal in-phase power division to output ports on the square-shaped periphery allows compact integration with other planar circuit modules in a combined amplifier. The design method can be extended to N-way power division where N is an odd integer multiple of 4.

N

The class-F power amplifier is known for its high efficiency. The class-F single-ended dual-fed distributed amplifier integrates both class-F amplification and efficient power combining in the one circuit, without using additional n-way power combiners. In this letter the earlier reported circuit topology and design method is modified to account for drain parasitic reactances. A 1.8-GHz amplifier employing two packaged field effect transistors was designed and tested. The measured drain dc efficiency and corresponding output power with an input generator available power of 14 dBm was 71% and 22dBm, respectively.

-Way Metamaterial Power Divider

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.

Modified class-F distributed amplifier

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.