CiteULike: dcastros distributed

Distributed channel model for HEMT signal and noise parameters

P Gardner — 2008-05-10T14:14:37-00:00

Electronics Letters, Vol. 28, No. 22. (1992), pp. 2063-2064.

A new simple model for the signal and noise properties of a microwave FET or HEMT avoids the need for any explicit correlation between gate and drain noise sources by distributing the drain-to-gate capacitance and the drain noise source along the conducting channel. The new model applied to a commercial HEMT chip demonstrates a very good fit to measured scattering and noise parameter data

A distributed-feedback antenna oscillator

Shin-Lin Wang — 2008-05-09T06:40:35-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 48, No. 5. (2000), pp. 857-860.

In this paper, a new design of the active transmitting antenna array, called the distributed-feedback antenna oscillator, is proposed. The active array is formed by serially connecting several unit cells to a closed loop. Each unit cell contains an amplifier and a two-port antenna, with an overall insertion gain larger than 0 dB and a phase delay equal to a multiple of 360°. The signal traveling on the loop is amplified and radiated in each unit cell. The radiation fields from all the antennas are then combined in free space. A four-element feedback antenna oscillator operating at 10 GHz is demonstrated by using two-port aperture-coupled microstrip antennas. Simulation results show that multiple oscillation modes with different frequencies and different radiation beams may be excited in the antenna oscillator. By experiment, it is found that each oscillation mode can be built by tuning the biases of the oscillator. The measured radiation pattern for each mode agrees very well with the predicted one. For a single-mode operation with a broadside pattern, bandstop filters of a simple geometry are designed and embedded in the oscillator to suppress the unwanted oscillation modes. Finally, the influence of the bias condition on the radiation power of the single-mode oscillator is investigated

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

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%.

Distributed amplifiers with composite left/right-handed transmission lines

J Mata-Contreras — 2007-11-14T17:48:40-00:00

Microwave and Optical Technology Letters, Vol. 48, No. 3. (2006), pp. 609-613.

The use of so-called ?composite left/right-handed transmission lines? in the design of distributed amplifiers is discussed using a simple model for the active device. The simplified analysis performed herein shows that it is possible to modify the frequency response of forward and reverse power gains, a significant development which could lead to innovative distributed amplifier designs. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 609-613, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21422

Planar distributed structures with negative refractive index

A Sanada — 2007-11-14T17:46:49-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 52, No. 4. (2004), pp. 1252-1263.

Planar distributed periodic structures of microstrip-line and stripline types, which support left-handed (LH) waves are presented and their negative refractive index (NRI) properties are shown theoretically, numerically, and experimentally. The supported LH wave is fully characterized based on the composite right/left-handed transmission-line theory and the dispersion characteristics, refractive indexes, and Bloch impedance are derived theoretically. In addition, formulas to extract equivalent-circuit parameters from full-wave simulation are given. Open (microstrip) and closed (stripline) structures with a 5/spl times/5 mm/sup 2/ unit cell operating at approximately 4 GHz are designed and characterized by full-wave finite-element-method simulations. A 20 /spl times/ 6 unit-cell NRI lens structure interfaced with two parallel-plate waveguides is designed. The focusing/refocusing effect of the lens is observed by both circuit theory and full-wave simulations. Focusing in the NRI lens is also observed experimentally in excellent agreement with circuit theory and numerical predictions. This result represents the first experimental demonstration of NRI property using a purely distributed planar structure.