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Design methodologies for broadband voltage-controlled-oscillators / Chawki Ghennai 

Public ISBD Titre : Design methodologies for broadband voltage-controlled-oscillators Type de document : texte imprimé Auteurs : Chawki Ghennai, Auteur ; M. J. Howes, Directeur de thèse Editeur : University of Leeds Année de publication : 1993 Importance : 170 f. Présentation : ill. Format : 27 cm. Note générale : Thèse de Doctorat : Électronique : Angleterre, University of Leeds : 1993 Bibliogr. f. 160 - 164 . Annexe f. 171 - 173 Langues : Anglais (eng) Mots-clés : Broadband  --  voltage-controlled-oscillators Negative  resistance/conductance  technique Transferred-electron-device Computer-aided-design  program Index. décimale : D000793 Résumé : The aim of the work presented in this thesis is to establish a design strategy for broadband Voltage-Controlled-Oscillators (VCOs). The desing methodology is based on a one port negative resistance/conductance technique and an accurated charactérisation of the VCO circuit. The circuit optimisation for maximising the available tuning bandwidth concentrates on the coupling between the active device and the tuning device. Small-signal and large-signal characterisation of the active device (TED) is carried out and presented as a two terminal admittance over the desired frequency range. A suitable topology of the VCO is then chosen, taking into account the fabrication constraints due to the packages of the divices and the microwave medium. An aquivalent circuit model for the VCO is then established and experimental investigations of the tuning circuit, the output circuit and the active device are carried out over the desired frequency range. Finally, a Computer-Aided-Design program is developed for the circuit optimisation process and performance determination at small-and large-signals. Since the use of a two terminal active device is in principle straightforward in oscillator design, the Transferred-Electron-Device (TED) is used as the active device in this work. The nonlinear characterisation of the TED is accomplished by the use of a physical model based on a one-dimensional drift-diffusion description of the intrinsic device. The VCO is built on microstrip using packaged devices for both the varactor and the TED. Apart from the nonlinear admittance of the intrinsic TED, the rest of the equivalent circuit model of the VCO is described in the frequency domain. However, the evaluation of the VCO circuit performance required by the optimisation process requires fast synthesis of the microstrip circuitry and hence approximate empirical expressions are used. Both distributed and lumped elements of the equivalent circuit are treated as multi-ports. The synthesis of the VCO has demonstrated the dependence of the tuning bandwidth of the chosen configuration of the VCO on the parameters and dimensions of the coupling elements between the varactor diode and the TED. An efficient overall Computer-Aided-Design (CAD) program has been developed and the comparison between the experimental and computed results has validated the design strategy. Minor differences are thought to be due to uncertainties in the values of the equivalent circuit elements of the device packages. Design methodologies for broadband voltage-controlled-oscillators [texte imprimé] / Chawki Ghennai, Auteur ; M. J. Howes, Directeur de thèse . - [S.l.] : University of Leeds, 1993 . - 170 f. : ill. ; 27 cm. Thèse de Doctorat : Électronique : Angleterre, University of Leeds : 1993 Bibliogr. f. 160 - 164 . Annexe f. 171 - 173 Langues : Anglais (eng) Mots-clés : Broadband  --  voltage-controlled-oscillators Negative  resistance/conductance  technique Transferred-electron-device Computer-aided-design  program Index. décimale : D000793 Résumé : The aim of the work presented in this thesis is to establish a design strategy for broadband Voltage-Controlled-Oscillators (VCOs). The desing methodology is based on a one port negative resistance/conductance technique and an accurated charactérisation of the VCO circuit. The circuit optimisation for maximising the available tuning bandwidth concentrates on the coupling between the active device and the tuning device. Small-signal and large-signal characterisation of the active device (TED) is carried out and presented as a two terminal admittance over the desired frequency range. A suitable topology of the VCO is then chosen, taking into account the fabrication constraints due to the packages of the divices and the microwave medium. An aquivalent circuit model for the VCO is then established and experimental investigations of the tuning circuit, the output circuit and the active device are carried out over the desired frequency range. Finally, a Computer-Aided-Design program is developed for the circuit optimisation process and performance determination at small-and large-signals. Since the use of a two terminal active device is in principle straightforward in oscillator design, the Transferred-Electron-Device (TED) is used as the active device in this work. The nonlinear characterisation of the TED is accomplished by the use of a physical model based on a one-dimensional drift-diffusion description of the intrinsic device. The VCO is built on microstrip using packaged devices for both the varactor and the TED. Apart from the nonlinear admittance of the intrinsic TED, the rest of the equivalent circuit model of the VCO is described in the frequency domain. However, the evaluation of the VCO circuit performance required by the optimisation process requires fast synthesis of the microstrip circuitry and hence approximate empirical expressions are used. Both distributed and lumped elements of the equivalent circuit are treated as multi-ports. The synthesis of the VCO has demonstrated the dependence of the tuning bandwidth of the chosen configuration of the VCO on the parameters and dimensions of the coupling elements between the varactor diode and the TED. An efficient overall Computer-Aided-Design (CAD) program has been developed and the comparison between the experimental and computed results has validated the design strategy. Minor differences are thought to be due to uncertainties in the values of the equivalent circuit elements of the device packages.

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