Variable centre frequency resonator based bandpass Σ-Δ modulator

A novel resonator-based bandpass Σ-Δ modulator with an in-built variable centre frequency feature is presented. This structure is designed by analytically determining and subsequently verifying through behavioural level simulations the necessary compensation hardware to be placed in the feedback to ensure stability and good dynamic range performance.

Tunable centre frequency resonator based bandpass Σ-Δ modulators

This paper presents a methodology for the design of oversampled narrow-band single-loop and multi-stage resonator-based bandpass Σ-Δ modulators that can accommodate different passband centre to sampling frequency ratios. These tunable bandpass configurations are designed by analytically determining the required compensation hardware to deliver good resolution. Thorough simulations demonstrate that comparatively superior in-band signal-to-noise ratios (SNRs) and dynamic ranges (DRs) are attributed to the inclusion of appropriate feedforward and feedback compensators within these structures.

Effective-fourth-order resonator based MASH bandpass sigma-delta modulators

Two novel effective-fourth-order (eighth-order) resonator based MASH (MultistAge noise SHaping) bandpass Σ-Δ modulators are introduced at the behavioural level and subsequently examined by simulations utilising the ALTA SPW environment. The considered bandpass configurations have in their loop filter a cascade of standard second-order resonator structures in order to achieve appropriate noise shaping. The quantisation noise in each stage is suppressed by feeding the error of each section into the input of the following stage. It is demonstrated in this paper that the quadruple effective-first-order cascade configuration has significantly better performance as well as conforming more closely with theory in comparison with the effective-second-order effective-second-order cascade. The superior performance of the former can be attributed to the cumulative effect of the multi-bit outputs as well as the presence of more notch filters.

Anharmonic Helmholtz free energy to O(lambdaâ ´) in the non- leading term approximation /|nby Leslie Wilk. -- 260 St. Catharines, Ont. : [s. n.],

Expressions for the anharmonic Helmholtz free energy contributions up to o( f ) ,valid for all temperatures, have been obtained using perturbation theory for a c r ystal in which every atom is on a site of inversion symmetry. Numerical calculations have been carried out in the high temperature limit and in the non-leading term approximation for a monatomic facecentred cubic crystal with nearest neighbour c entralforce interactions. The numbers obtained were seen to vary by a s much as 47% from thos e obtai.ned in the leading term approximati.on,indicating that the latter approximati on is not in general very good. The convergence to oct) of the perturbation series in the high temperature limit appears satisfactory.

On the Ewald method and the quartic Helmholtz free energy of an anharmonic metallic crystal

Thesis (M. Sc.) - Brock University, 1978.

An anharmonic contribution to the Helmholtz free energy O(lambda 6)

The anharmonic contributions of order A6 to the Helmholtz free energy for a crystal in which every atom is on a site of inversion symmetry, have been evaluated The cor~esponding diagrams in the various orders of the perturbation theory have been presented The validity of the expressions given is for high temperatures. Numerical calculations for the diagrams which contribute to the free energy have been worked out for a nearest-n~ighbour central-force model of a facecentered cubic lattice in the high-temperature limit and in the leading term and the Ludwig approximations. The accuracy of the Ludwig approximation in evaluating the Brillouin-zone sums has been investigated. Expansion for all diagrams in the high-temperature limit has been carried out The contribution to the specific heat involves a linear as well as cubic term~ We have applied Lennard-Jones, Morse and Exponential 6 types of potentials. A comparison between the contribution to the free energy of order A6 to that of order A4 has been made.

Broadband Cylindrical Dielectric Resonator Antenna Excited by Modified Microstrip Line

The impedance bandwidth of a high permittivity cylindrical dielectric resonator antenna excited by a micro strip line was significantly improved by modifying the feed geometry. The 10 dB return loss bandwidth is enhanced from 12 to 26% without much affecting the gain and other radiation properties of the antenna. Good agreement has been observed between the predicted and measured results

Dielecting-resonator-loaded microstrip antenna for enhanced impedance bandwidth and efficiency

A new method for enhancing the 2.1 VSWR impedance bandwidth of microstrip antennas is presented. Bandwidth enhancement is achieved by loading the microstrip antenna by a ceramic microwave dielectric resonator (DR). The validity of this technique has been established using rectangular and circular radiating geometries. This method improves the bandwidth of a rectangular microstrip antenna to more than 10% (= 5 times that of a conventional rectangular microstrip antenna) with an enhanced gain of I dB

Excitation of low-profile equilateral-triangular dielectric resonator antenna using a conducting conformal strip

A new configuration that employs a conducting conformal strip to excite the low-profile equilaterial-triangular dielectric resonator antenna (DRA) of very high permittivity is proposed. As compared with the previous aperture-coupling configuration, the new configuration has a wider impedance bandwidth (- 5.5%) and a higher front-to-back radiation ratio. The return loss, radiation patterns, and antenna gain are measured and discussed

A Microstrip Patch Resonator with a Via Connecting Ground Plane

patch resonator with a via connecting ground plane is proposed and studied experimentally. The resonant frequency of this patch resonator is tunable up to about 34 % by adjusting the via position in the center line. The lowest resonant frequency of this patch resonator has been reduced by more than 64% of the same size patch resonator

A compact very-high-permittivity dielectric-eye resonator antenna for multiband wireless applications

very-high-permittivity (e, = 100) multiband dielectrice> e resonator antenna is presented. The compact antenna, excited by a m:'crostrip line, resonates at two frequencies centered around the 1.9- GHz and 2.4-GHz bands with identical polarization . The behavior of the antenna at different positions along the feed line is studied and optimized. Multiple resonances with the same polarization and broad radioticn patterns suggest the suitability of the antenna for multiband wireless application

Characteristics of a Microstrip-Excited High-Permittivity Tectangular Dielectric Resonator Antenna

The radiation characteristics of a microstrip-line-excited rectangular dielectric resonator antenna (DRA) are studied experimentally.The radiation charactristics and excitation of different modes are highly influenced by the orientation of the DR,feed line parameters ,and finite size of the ground plane

Wideband Oylindrioal Dielectric Resonator Antenna Excited Using an L-strip Feed

A broadband cylindrical dielectric resonator antenna (DRA) energized with an L-strip feed is presented The novel exciting technique achieves a 2:1 VSWR bandwidth of 18%. The variation of bandwidth for different feed parameters is also studied

T-strip-fed High-Permittivity Rectangular Dielectric Resonator Antenna for Broadband Applications

rectangular low-density, high-permittivity dielectric resona or antenna (DRA) excited by T-shaped microstrip feed offering a 2:1 VSWR bandwidth of -22% at 2.975 GHz is reported. The design methoaology and experimental results of the antenna are discussed. The excellent gain and radiation performance of the proposed antenna project: it as a potential candidate for telecommunication applications