Sat, 19 Jul 2008 03:10:35 BST CiteULike: dcastro's Paul http://www.citeulike.org/user/dcastro/author/Paul CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dcastro/article/2782935 <i>Electronics Letters, Vol. 28, No. 22. (1992), pp. 2063-2064.</i><br /><br />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 Distributed channel model for HEMT signal and noise parameters P Gardner DK Paul Electronics Letters, Vol. 28, No. 22. (1992), pp. 2063-2064. 2008-05-10T14:14:37-00:00 1992 Electronics Letters 28 22 2063 2064 amplifier channel distributed microwave model noise parameter signal http://www.citeulike.org/user/dcastro/article/2782068 <i>Satellite Communications - ECSC-3, 1993., 3rd European Conference on (1993), pp. 394-398.</i><br /><br />Power amplifier nonlinearity limits the performance of communication systems, both on the ground and in space, through undesirable effects such as crosstalk, intermodulation distortion and reduced signal to noise ratio in the presence of multiple signals. Feedforward linearization is a promising technique for improving the performance of power amplifiers particularly in millimetre wave applications where the power output of currently available devices is limited Feedforward linearization of microwave amplifiers K Konstantinou P Gardner DK Paul Satellite Communications - ECSC-3, 1993., 3rd European Conference on (1993), pp. 394-398. 2008-05-10T00:03:29-00:00 1993 Satellite Communications - ECSC-3, 1993., 3rd European Conference on 394 398 amplifier linearization power http://www.citeulike.org/user/dcastro/article/2782066 <i>Microwave Symposium Digest, 1992., IEEE MTT-S International (1992), pp. 277-280 vol.1.</i><br /><br />Four models have been developed and assessed for fitting the measured noise parameters up to 26 GHz and S-parameters up to 400 GHz for a commercial HEMT (high electron mobility transistor) chip. The first treats the intrinsic noise sources as uncorrelated thermal sources. The second is an extension of this, allowing a better fit to be achieved by including the distributed nature of the gate and drain electrodes using a semidistributed, sliced model. The third model neglects the distributed effect but takes into account the partial correlation of the gate and drain noise sources. This causes a larger improvement in the quality of fit, allowing the model to fit the measured data within reasonable measurement limits. The addition of the distributed effect to the correlated model gives the fourth model, which allows a further marginal improvement, but the conditioning of the problem and the accuracy of the data appear to be insufficient to allow accurate extraction of the additional parameters needed HEMT models for S-parameter and noise parameter extrapolation MT Hickson P Gardner DK Paul doi:10.1109/MWSYM.1992.187966 Microwave Symposium Digest, 1992., IEEE MTT-S International (1992), pp. 277-280 vol.1. 2008-05-10T00:03:25-00:00 1992 Microwave Symposium Digest, 1992., IEEE MTT-S International 277 280 vol.1 model noise parameter http://www.citeulike.org/user/dcastro/article/2782036 <i>Electronics Letters, Vol. 30, No. 21. (1994), pp. 1772-1774.</i><br /><br />Unwanted even order modes in tunable microstrip ring resonators can be suppressed by providing a low resistance path to ground at an appropriate point on the ring. This suppression method is simple to implement, and has minimal effect on the Q factor and the resonance frequency of the wanted modes Suppression of even modes in microstrip ring resonators DK Paul P Gardner KP Tan Electronics Letters, Vol. 30, No. 21. (1994), pp. 1772-1774. 2008-05-09T23:51:31-00:00 1994 Electronics Letters 30 21 1772 1774 microstrip resonator http://www.citeulike.org/user/dcastro/article/2782026 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 45, No. 5. (1997), pp. 580-586.</i><br /><br />A new method, using the noise matrix approach, has been developed for determining the optimum reactive terminations for a transistor employed as a low-noise negative-resistance element in a reflection-mode amplifier. This new method corroborates the less efficient graphical method the authors reported earlier. It is established theoretically and demonstrated numerically that the optimum noise measure of a transistor used in a reflection-mode amplifier is independent of the choice of active terminal and is identical to the optimum noise measure of the same transistor when used in a conventional transmission-mode amplifier Optimum noise measure configurations for transistor negative resistance amplifiers P Gardner DK Paul doi:10.1109/22.575572 Microwave Theory and Techniques, IEEE Transactions on, Vol. 45, No. 5. (1997), pp. 580-586. 2008-05-09T23:50:36-00:00 1997 Microwave Theory and Techniques, IEEE Transactions on 45 5 580 586 amplifier measurement noise http://www.citeulike.org/user/dcastro/article/2776127 <i>Electronics Letters, Vol. 29, No. 18. (1993), pp. 1633-1635.</i><br /><br />A systematic method for optimising the performance of feedforward linearised microwave power amplifiers has been developed. Simulated and practical feedforward systems optimised with this method achieve significant improvement in third order intermodulation product level and compression point Optimisation method for feedforward linearisation of power amplifiers K Konstantinou P Gardner DK Paul Electronics Letters, Vol. 29, No. 18. (1993), pp. 1633-1635. 2008-05-09T15:21:03-00:00 1993 Electronics Letters 29 18 1633 1635 amplifier power http://www.citeulike.org/user/dcastro/article/2776125 <i>Microwave Symposium Digest, 1995., IEEE MTT-S International (1995), pp. 83-86 vol.1.</i><br /><br />Tunable microstrip ring resonator oscillators and filters are described. Two alternative techniques for suppression of unwanted higher order modes are reviewed. The practical oscillator has a tuning bandwidth of nearly 30%, and phase noise better than -90 dBc, 10 kHz from carrier. This is encouraging performance for a compact planar device Microwave oscillators and filters based on microstrip ring resonators DK Paul P Gardner doi:10.1109/MWSYM.1995.406092 Microwave Symposium Digest, 1995., IEEE MTT-S International (1995), pp. 83-86 vol.1. 2008-05-09T15:20:58-00:00 1995 Microwave Symposium Digest, 1995., IEEE MTT-S International 83 86 vol.1 microwave oscillator resonator http://www.citeulike.org/user/dcastro/article/2776126 <i>Electronics Letters, Vol. 30, No. 21. (1994), pp. 1770-1771.</i><br /><br />A microwave oscillator incorporating a varactor-tuned microstrip ring resonator was developed using a single packaged varactor diode which together with other required components was mounted inside the ring structure. A tuning bandwidth of ~30% was achieved with forward and reverse biasing of the varactor diode. The measured phase noise of the new oscillator was found to be better than -90 dBc kHz from the carrier Microwave voltage tuned microstrip ring resonator oscillator P Gardner DK Paul KP Tan Electronics Letters, Vol. 30, No. 21. (1994), pp. 1770-1771. 2008-05-09T15:20:58-00:00 1994 Electronics Letters 30 21 1770 1771 microwave oscillator resonator ring http://www.citeulike.org/user/dcastro/article/2776114 <i>Millimetre Wave Transistors and Circuits, IEE Colloquium on (1991), pp. 10/1-10/4.</i><br /><br />Negative resistance, reflection mode amplification using GaAs FETs or HEMTs offers the possibility of realising the low noise performance associated with such devices whilst achieving a higher gain per stage than conventional transmission mode amplifiers. This possibility is of particular interest in the MM-wave region, where the gain per stage of conventional FET and HEMT amplifiers, when tuned for optimum noise measure, is low. An additional potential benefit, of particular interest for radar LNA applications, is the probable existence of a low loss bypass path through a reflection amplifier after failure of the active device. In this paper, the circuit conditions for optimum noise measure in negative resistance transistor amplifiers are determined, and several examples are given. Design details and measured results are given for an example in X-band. The suitability of the technique for MM-wave frequencies is assessed as far as possible using published S-parameter and noise data for a HEMT device, and a theoretical circuit design is presented Negative resistance low noise, reflection mode transistor amplifiers for microwave and millimetre wave applications DK Paul P Gardner Millimetre Wave Transistors and Circuits, IEE Colloquium on (1991), pp. 10/1-10/4. 2008-05-09T15:18:10-00:00 1991 Millimetre Wave Transistors and Circuits, IEE Colloquium on 10/1 10/4 amplifier low microwave noise http://www.citeulike.org/user/dcastro/article/2776113 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 39, No. 11. (1991), pp. 1869-1875.</i><br /><br />The authors consider the use of microwave transistors in the negative resistance reflection mode and present the conditions for optimum noise performance. Possible advantages include the possibility of higher gain in the millimeter-wave region, which can be achieved by absorbing the parasitic common lead inductance into the feedback circuit designed to generate the negative resistance, and the existence of a failsafe mode of operation, in that the failure of the active device or its power supply is likely to lead a low return loss, resulting in a small insertion loss through the amplifiers, which may permit continued, although degraded, system operation. The latter potential advantage has proved to be of interest to radar system designers Aspects of the design of low noise, negative resistance, reflection mode transistor amplifiers P Gardner DK Paul doi:10.1109/22.97488 Microwave Theory and Techniques, IEEE Transactions on, Vol. 39, No. 11. (1991), pp. 1869-1875. 2008-05-09T15:18:10-00:00 1991 Microwave Theory and Techniques, IEEE Transactions on 39 11 1869 1875 amplifier low noise transistor http://www.citeulike.org/user/dcastro/article/2776111 <i>Electronics Letters, Vol. 29, No. 16. (1993), pp. 1408-1409.</i><br /><br />The limited gain available from GaAs FETs and HEMTs at millimetric frequencies can be overcome by using the devices in a negative resistance amplifier configuration. The advantage of the solid-state negative resistance amplifier over the transmission amplifier is that the gain available is not limited by the active device used. It has been shown that, over a narrow bandwidth, significantly higher gain can be obtained from a negative resistance amplifier, when compared to a transmission amplifier using the same device, while maintaining the same overall noise performance. This has been demonstrated experimentally using a 0.25 μm HEMT device High gain millimetric negative resistance low noise amplifiers MT Hickson P Gardner DK Paul Electronics Letters, Vol. 29, No. 16. (1993), pp. 1408-1409. 2008-05-09T15:18:07-00:00 1993 Electronics Letters 29 16 1408 1409 amplifier gain high low noise http://www.citeulike.org/user/dcastro/article/2776110 <i>Microwaves, Antennas and Propagation, IEE Proceedings -, Vol. 143, No. 2. (1996), pp. 184-188.</i><br /><br />Symmetrical transmission line ring resonators are studied using the generalised reflection coefficient concept and the odd- and even-mode analysis method. The mode distributions for closed, tunable and selectively damped rings are derived. A normalised tuning characteristic is generated for a capacitively tunable ring, showing agreement with derivations based on current continuity in the limit of loose coupling. The perturbation of resonant frequencies by nonzero coupling is also calculated. An optimum value for an even-mode damping resistance is derived. A circuit simulator is used to demonstrate that the features derived analytically for lossless lines persist when realistic values of loss and dispersion are introduced Transmission line analysis of symmetrical ring resonators P Gardner DK Paul Microwaves, Antennas and Propagation, IEE Proceedings -, Vol. 143, No. 2. (1996), pp. 184-188. 2008-05-09T15:18:05-00:00 1996 Microwaves, Antennas and Propagation, IEE Proceedings - 143 2 184 188 resonator ring tl http://www.citeulike.org/user/dcastro/article/2776103 <i>Microwave Theory and Techniques, IEEE Transactions on, Vol. 40, No. 8. (1992), pp. 1709-1712.</i><br /><br />A model is described for a low noise millimeter-wave HEMT device. It takes account of the distributed nature of the gate and drain electrodes by dividing the active region of the device into a number of slices. Each slice is modeled as an intrinsic HEMT with thermal noise sources and the slices are connected together through lossy reactances. The parameters of the first slice are made different from those of the remaining slices, in order to account for the inevitable differences in the field distribution in the gate feed region. The model parameters have been optimized numerically to fit the manufacturer's measured S-parameters and all four noise parameters, for a commercially available HEMT chip. A good fit has been achieved simultaneously to all of these parameters, and the model therefore provides a reasonable basis for extrapolation to higher frequencies. The significance of the distributed gate effect and the unequal slice effect is assessed by comparing the best fit achievable when these effects are not included A semidistributed HEMT model for accurate fitting and extrapolation of S-parameters and noise parameters MT Hickson P Gardner DK Paul doi:10.1109/22.149534 Microwave Theory and Techniques, IEEE Transactions on, Vol. 40, No. 8. (1992), pp. 1709-1712. 2008-05-09T15:16:17-00:00 1992 Microwave Theory and Techniques, IEEE Transactions on 40 8 1709 1712 fet model noise