Basic blocks for high-frequency interconnects: theory andexperiment

Proximity-coupled open-end microstrip transitions in double-layer planar structures are investigated through the method of moments solution of integral equations. Two types of EMC (electromagnetically coupled) microstrip lines are considered, namely, collinear lines and transverse lines. It is found that these transitions are broadband and provide a wide range of coupling coefficients. The theoretical model for the transverse microstrip transitions is in good agreement with measurements     

Resonant optical amplification in a laser diode: theory andexperiment

Resonant optical amplification is studied both theoretically and experimentally. Coupled rate equations for the signal field and the spontaneous emission field, valid for input signals with bit rates up to 10 Gb/s are derived. A special weighing procedure based on a dwell-time analysis is used to account for bistable filter operation. The measured amplification characteristics of a λ/4 DFB laser injected with a 2.5 Gb/s signal show good agreement with theory     

Q-factor of tuned microstrip resonator

The paper presents research of quality factor in the micro-mechanically tunable microstrip resonator and its change in response to tuning. In the presented design unloaded quality factor increases about 10% during tuning due to reduction of dielectric loss in substrate’s medium and ohmic loss in metal electrodes. When total loss in the device is relatively small, loss mechanisms contribute additively, so complex effective permittivity can be used to account loss reduction and frequency tuning.     

Lateral modes of broad area semiconductor lasers: theory andexperiment

Calculations of the lateral modes of an ideal broad area laser, including the nonlinear interaction between the carriers and the optical field, are made. The results include periodically modulated near fields and single- and double-lobed far fields similar to those previously measured. The unsaturable losses are higher and quantum efficiencies are lower than those determined from plane-wave approximations. Broad area InGaAs-GaAlAs-GaAs quantum-well lasers were fabricated and measured and found to closely agree with the theory in near, far, and spectrally resolved near fields. An occultation experiment on the far field confirms previously predicted unstable resonatorlike modes with V-shaped fronts     

The compound cavity optical parametric oscillator: theory andexperiment

We present the time dynamics of a compound-cavity optical parametric oscillator (OPO) using a mathematical model for the modes under the gain profile of the oscillator which accounts for pump depletion and the cavity-Q factors. The computational results show that this type of cavity is superior in that its threshold is lower than that of a simple narrow-band cavity with dispersive elements and its efficiency is increased, while its narrow linewidth remains nearly the same across the tunable range of the nonlinear crystals used. A diagram illustrating the operation state of a compound-cavity OPO is presented, which is applicable to the simple narrow-band cavity, simple broad-band cavity, compound cavity, and traveling-wave amplification. The theoretical results are compared to the experimental data from a compound-cavity OPO using a grazing-incidence prism and grating as dispersive elements     

Experimental investigation of microwave-optoelectronic interactionsin a microstrip ring resonator

Microwave optoelectronic mixing on a semi-insulating gallium arsenide substrate performed by monolithically integrating Schottky diode photodetectors into a microstrip ring resonator is discussed. When operated in the resistive mixing mode, a low frequency difference signal is extracted from the bias pad of the circuit. In the parametric mode, both degenerate and non-degenerate parametric amplification of an optical carrier signal takes place. The circuit shows good potential for application in wide-band fiberoptic systems     

Stabilisation of a W-band microstrip oscillator by a dielectric resonator

The effect of temperature on the performance of a dielectric resonator compensated W-band impatt diode microstrip oscillator is shown to be quite small. The frequency change was about 2 MHz/°C as compared to the uncompensated oscillator's 10 MHz/°C. The design of the oscillator is presented and the resonator used was a cuboid of temperature compensated barium nonatitanate.     

Carrier-density modulation effects in a traveling-wavesemiconductor optical amplifier: communications theory analysis andexperiment

A communications theory equivalent model suitable for analyzing carrier-density modulation effects within a traveling-wave semiconductor optical amplifier is derived by linearizing the amplifier rate equation. This model is used to analyze dual-channel amplification, and it is shown to give results which are in good agreement with those given by nonlinear polarization theory and experimental measurements. The effect of four-wave mixing on the amplification of many optical channels for worst-case operating conditions is studied, and it is shown that the individual channels experience different gains. It is also shown that if the individual channel gains are to be confined to lie within a ±1-dB band when operating the amplifier at high values of unsaturated power gain     

Chaos in semiconductor lasers with optical feedback: theory andexperiment

The authors present a detailed theoretical and experimental investigation of the nonlinear dynamics of a semiconductor laser with optical feedback. The results show that the coherence collapsed state is a chaotic attractor and that chaos is reached for increasing feedback level through a quasi-periodic route interrupted by frequency locking. Furthermore, the coexistence of two attractors, associated with the same external cavity mode, but having different relaxation oscillation frequencies, is demonstrated and explained     

Dynamic permittivity of microstrip ring resonator

A simplified method for calculation of the dynamic dielectric constant for a microstrip ring resonator is presented. Attention is also given to the sectors of the annular structure. The new results are compared with earlier work.     

Microstrip bandpass filter using degenerate modes of a microstrip ring resonator

It is shown that two degenerate modes can be excited on a microstrip ring resonator. These modes can be used to realise a double-tuned circuit bandpass filter in microstrip technique.     

Simple resonator method for measuring dispersion of microstrip

The method uses the resonant frequencies of a simple straight microstrip resonator, short-circuited at both ends. It is excited by passing a current through one of the short circuits. Graphs of effective relative permittivity against frequency are given for resonators on alumina and quartz substrates, with an error of within only ±0.1%.     

Microwave performance of nonlinear optoelectronic microstrip ring resonator

Difference and sum frequency generation at frequencies from 0 to 14 GHz has been obtained by mixing of a microwave local oscillator and a modulated optical carrier in a microstrip ring resonator with Schottky contacts on a semi-insulating GaAs substrate.<>     

Incremental theory of diffraction: a new-improved formulation

In this paper, a general systematic procedure is presented for defining incremental field contributions. They may provide effective tools to describe a wide class of scattering and diffraction phenomena at any aspect, within a unitary, self-consistent framework. This procedure is based on a generalization of the incremental theory of diffraction (ITD) localization process for uniform cylindrical, local canonical problems with elementary source illumination and arbitrary observation aspects. In particular, it is shown that the spectral integral formulation of the exact solution for the local canonical problem may also be represented as a spatial integral convolution along the longitudinal coordinates of the cylindrical configuration. Its integrand is then directly used to define the relevant incremental field contribution. For the sake of convenience, but without loss of generality, this procedure is illustrated for the case of local wedge configurations. Also, a specific suitable asymptotic analysis is developed to derive new closed form high-frequency expressions from the spectral integral formulation. These expressions for the incremental field contributions explicitly satisfy reciprocity and are applicable at any incidence and observation aspect. This generalization of the ITD localization process together with its more accurate asymptotic analysis provides a definite improvement of the method.     

Analytic theory of a tapered gyrotron resonator

An analytic theory has been derived for determining the eigenfrequencies, RF-field distribution and Q of the TE_mpq modes of a gyrotron resonator consisting of a circular cylinder joined to a slowly tapered section. Explicit results are obtained for a linear taper. The cavity modes are found to have an RF-field distribution which is useful for prebunching the electron beam and enhancing efficiency. For high Q cavities, the cavity Q depends on axial mode number q as q^?2, which is important for mode discrimination. Proper selection of taper length is found to reduce the Q of high q modes, also aiding in mode discrimination. The present approach may be applied to other forms of weakly irregular cavities, such as cavities with nonlinear tapers.     

Directivity of linear microstrip arrays

An analytical expression for the directivity is derived for uniformly excited linear arrays of rectangular printed antennas. Each antenna is assumed to radiate as two identical slots with a spacing which depends on the dielectric substrate. The directivity is plotted against distance between printed elements for two dielectric substrates, PTFE and alumina.     

Dual-mode microstrip bandpass filter using ring of arrows resonator

A dual-mode microstrip bandpass filter using the degenerate modes of a modified square ring structure is proposed. The size of the new structure is 50% less than conventional dual-mode bandpass microstrip square resonator filters at the same centre frequency. Measurements are in good agreement with designed values.     

A Lagrangian formulation of Zador's entropy-constrainedquantization theorem

Zador's (1963, 1966) classic result for the asymptotic high-rate behavior of entropy-constrained vector quantization is recast in a Lagrangian form which better matches the Lloyd algorithm used to optimize such quantizers. The equivalence of the two formulations is shown and the result is proved for source distributions that are absolutely continuous with respect to the Lebesgue measure which satisfy an entropy condition, thereby generalizing the conditions stated by Zador under which the result holds     

Bandpass filter design using a microstrip triangular loop resonator with dual-mode operation

A bandpass filter (BPF) design using a dual-mode microstrip triangular loop resonator is presented for the first time. The circuit produces frequency responses with one real finite frequency transmission zero and one imaginary finite frequency zero on either side of the passband. Depending on the perturbation arrangement, the nature of the coupling between degenerate modes causes the zeros to exchange their axis locations from real to imaginary and from imaginary to real while keeping their magnitude. This behavior results in frequency responses that are suitable for applications with asymmetrical requirements. Results show 8% bandwidth filters with insertion loss ranging from 0.82 dB to 1.4dB at 10 GHz. Advantages in size reduction and design flexibility are demonstrated when the triangular loop is compared to other dual-mode resonators.