IEEE MTT/ED/AP/LEO Societies Joint Chapter. United Kingdom and Republic of Ireland Section. 1996 2nd High Frequency Postgraduate Student Colloquium

13-13 Feb. 1996

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  • 1996 2nd High Frequency Postgraduate Student Colloquium [front matter]

    Publication Year: 1996, Page(s):i - ix
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    Freely Available from IEEE
  • Lowpass filters using series stubs

    Publication Year: 1996, Page(s):1 - 6
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (256 KB)

    A number of short circuited series stubs have been measured. Based on parameters derived from these measurements, a range of lowpass filters have been constructed which show excellent agreement in cut-off frequencies but unexpected behaviour in their stopbands. Simulated results for filters with ideal stubs are presented with no observance of these peculiarities. It is proposed that these peculiar... View full abstract»

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  • Nonlinear transmission line (NLTL) design as a pulse generator

    Publication Year: 1996, Page(s):7 - 10
    Cited by:  Papers (1)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (345 KB)

    Computer simulations are performed to optimize the number of sections in a tapered NLTL generating a pulse signal. The Schottky diode model is used based on physical simulation using Silvaco. The extracted CV characteristics are fitted to a hyperbolic function. The effect of the input frequency on the output pulse is investigated. View full abstract»

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  • Analytical modelling of the heterojunction bipolar transistor based distributed amplifier

    Publication Year: 1996, Page(s):11 - 16
    Cited by:  Papers (2)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (427 KB)

    In this paper we introduce a technique for modelling the distributed amplifier (DA) and in particular, the Heterojunction Bipolar Transistor (HBT) based DA. This modelling takes into account all feedback and parasitic elements associated with the HBT. Simulations of DAs based on our model and existing models are compared to those of the full DA. Results indicate that our model shows significant im... View full abstract»

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  • Low field microwave power dependence as a function of temperature in Gd123 thin films

    Publication Year: 1996, Page(s):17 - 22
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (400 KB)

    Using a 5 GHz parallel plate resonator, several Gd123 thin films have been studied as a function of low microwave power and temperature. Two simple models which describe the power dependence of high temperature superconducting films are discussed. For this preliminary study, films were chosen whose microstructure appeared to be most suitable for modelling. View full abstract»

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  • Efficient equalisation of signal shaping filters

    Publication Year: 1996, Page(s):23 - 26
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (305 KB)

    A simple technique for the delay equalisation of microstrip signal shaping filters exhibiting dispersion is presented. The work identifies and targets the frequency range over which equalisation is most important so that equalisation can be achieved more efficiently. A compact solution is demonstrated using microstrip coupled allpass filter networks and the resulting improvement in signal shaping ... View full abstract»

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  • Characterisation of lightwave networks

    Publication Year: 1996, Page(s):27 - 32
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    The increasing use of microwave fibre-optic links requires that efficient and accurate lightwave network analysers and techniques are developed. This paper follows from previous work done on a bilateral test set for lightwave networks. Theoretical simulations have been carried out which have demonstrated the viability of this approach for lightwave measurements. The advantage of the proposed netwo... View full abstract»

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  • Feedback control of a linearised Mach-Zehnder modulator for SCM applications

    Publication Year: 1996, Page(s):33 - 38
    Cited by:  Patents (1)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (533 KB)

    This paper introduces a practical feedback control technique which stabilises the third-order linearisation performance of a Mach Zehnder modulator. Predistortion linearisation is performed to reduce non-linear intermodulation distortion generated by a Mach Zehnder modulator. Results that show the lineariser performance are presented and a method is identified of how the system can be extended to ... View full abstract»

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  • All-optical microwave frequency filters

    Publication Year: 1996, Page(s):39 - 44
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (392 KB)

    This paper introduces the field of all-optical signal processing at microwave frequencies, in which optical fibre networks are used to realise signal processing functions. The fundamental principles are explained, and the components of these structures described. An analysis of basic film structures, which can be used as building blocks for more complicated structures, is included with supporting ... View full abstract»

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  • Low loss phase shifter for dielectric waveguide

    Publication Year: 1996, Page(s):45 - 50
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (313 KB)

    This paper presents a design method for dielectric waveguide phase shifters. Phase shifting is achieved by varying the distance between a dielectric waveguide and an arbitrary piece of dielectric. Experimental results are given and are shown to be in good comparison with the theory. It is shown that phase shifters with very low loss can be realised if the dielectric is small in comparison to the w... View full abstract»

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  • Ideal absorption condition for FDTD method in isotropic lossy dispersive media

    Publication Year: 1996, Page(s):51 - 57
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (399 KB)

    The behaviour of the electromagnetic field in isotropic lossy media is described with the PML split field forms in a modified set of Maxwell's equations in stretched coordinates. The general expressions for propagation constants, impedance, reflection and transmission coefficients with original constitutive parameters in isotropic lossy media and stretched complex coefficients are derived. We call... View full abstract»

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  • Faster computations for segmentation method based on cavity model

    Publication Year: 1996, Page(s):58 - 63
    Cited by:  Papers (2)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (419 KB)

    The segmentation method based on cavity model for the analysis of microstrip patch antennas is treated here. The Green's function and subsequently the fields inside the patch, which are expressed as a double summation, are converted to single summation. The time for calculation of stored energy and radiated power, improves as a result. The sample calculations for a rectangular patch and a crossed-... View full abstract»

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  • Linear and circular polarised cylindrical dielectric resonator antennas

    Publication Year: 1996, Page(s):64 - 68
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    A circular polarised and a switchable cylindrical dielectric resonator antenna are reported. The switchable antenna provides two linear polarised, one circular polarised, and a non-radiating mode. The experimental results of the resonant frequency, boresight axial ratio, gain, unloaded Q-factor, impedance bandwidth and radiation efficiency for both the antennas are presented and compared with the ... View full abstract»

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  • Two element active antenna array mode stability

    Publication Year: 1996, Page(s):69 - 72
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (227 KB)

    It is known that when a passive antenna array is arranged to enable quasi-optical power-combining, a single phase distribution or mode will exist between the individual elements. However, when active antenna arrays are considered the individual active antenna oscillators can exhibit a number of array modes. In this paper, closed form analytical equations for the stability condition for the two mod... View full abstract»

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  • Retrodirective beam formation using switched amplifiers

    Publication Year: 1996, Page(s):73 - 76
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (302 KB)

    This paper presents experimental results for retrodirective beam formation using switched amplifiers. A two element retrodirective antenna array using this technique was built at 1 GHz, using microstrip patch antennas as array elements. Commercially available amplifiers and switches were used to make the amplifier switching circuitry. Initial results of the experiments conducted on this prototype ... View full abstract»

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