Showing papers on "Q factor published in 1986"

Switched-capacitor high-Q bandpass filters for IF applications

Abstract: Experimental results for a sixth-order switched-capacitor bandpass filter with a selectivity Q of 55 at a center frequency of 3.1 MHz are presented. A simple noise analysis of active bandpass filters composed of coupled identical resonators is introduced to explain the dynamic range reduction in high-Q active filters resulting from loose high-Q couplings between resonators. Theoretical predictions of noise in coupled resonator-type bandpass filters agree well with measured results. The prototype chip occupies 2 mm/SUP 2/ and dissipates 45 mW with a single 5-V supply.

Design of a Bragg cavity for a millimeter wave free‐electron laser

Abstract: This letter concerns a design of a Bragg cavity for TM modes that can be used with a free‐electron laser (FEL) or other electron beam generator. If the corrugated wall in the FEL section meets the Bragg condition, the distributed feedback mechanism can function like mirrors in the usual laser cavity; however, the Bragg cavity eliminates the dead space between the interaction region and the reflectors so that it is a preferred design where the pulse duration of the electron beam is limited. The calculations indicate that high reflection coefficients that correspond to high cavity Q factor can be obtained if we carefully choose the parameters of the corrugated wall, such as period, amplitude, and length. Finally, we discuss factors to be considered in the design of a Bragg cavity for a FEL based on an intense relativistic electron beam and an electromagnetic pump wave.

A lead-on-sapphire superconducting cavity of superior quality

Abstract: A cavity consisting of a superconducting lead film on a sapphire substrate has been fabricated to obtain the enhanced frequency stability possible with this configuration. The cavity exhibits a quality value Q exceeding 2 x 10 to the 9th in its TE011 mode with a resonant frequency of 2.689 GHz. Methods of fabrication and testing of the cavity are presented. Since the interface between the film and substrate is exposed ot the full value of the resonant magnetic field, the present experiment is the most sensitive test to date for enhanced losses at the interface itself. No evidence of such losses is used. In fact, the measured values of the surface resistance match very well predictions for RF losses based on the BCS theory.

Invariant Definitions of the Unloaded Q Factor (Short Paper)

Abstract: Equations are presented for computing the unloaded Q factor of a microwave resonator embedded in an impedance-transforming lossIess, reciprocal two-port. Knowledge of the transformation properties of the two-port is not required.

Variational Analysis of GT Cut Quartz Crystal Resonators with the Supporting Portions at the Ends

Abstract: It is well known that a GT cut quartz crystal resonator coupled between two extensional mode vibrations has a cubic curve in frequency-temperature characteristics as well as an AT cut quartz crystal resonator. This paper studies frequency-temperature characteristics and electrical characteristics of the GT cut quartz crystal resonator with the supporting portions at both ends of the vibrational portion. First, a secular equation is derived from a vibration analysis of the resonator consisting of the vibrational portion and the supporting portions, by applying the energy method. From this secular equation, a relationship of resonant frequency, frequency temperature coefficients vs. a cut angle, a dimensional ratio and a mass ratio for the GT cut quartz crystal resonator is clarified theoretically. At the same time, from comparison of the calculated values with the experimental values, it is confirmed that they agree very well. Next, electrical characteristics of the quartz crystal resonators manufactured for trial experiments are measured. As a result, it is confirmed that a GT cut quartz crystal resonator with excellent frequency temperature characteristics, low crystal impedance and a high quality factor is realized.

A High Q Cavity Stabilized Gunn Oscillator at 94 GHz

Abstract: The set up and the performance of a 94 GHz second harmonic Gunn oscillator that is cavity stabilized at its fundamental frequency is described. The cavity has a quality factor of about 7000 and reduces the phase noise by nearly 40 dB. The oscillator generates an output power of 40 mW, sufficient to drive low noise balanced mixers, to synchronize Impatt oscillators or to operate as a reference source in coherent radar systems.

Yttrium aluminate sources of ultrashort radiation pulses with a controlled resonator Q factor

Abstract: An experimental investigation was made of the output characteristics of a solid-state yttrium aluminate laser with passive and mode locking, operated in the regime of a controlled resonator Q factor. This made it possible to generate radiation pulses of 15 psec duration with a duration stability of ±5% and with the second harmonic energy constant to within ±6%. An electric synchronizing pulse was generated: it preceded a train of picosecond pulses by a time interval which could be varied continuously in the range 300–1500 nsec with an accuracy to within ±5 nsec.

Unloaded Q-Factor of Stepped-Impedance Resonators

Abstract: The paper presents general expressions for the unloaded Q-factor of stepped-impedance resonators partially loaded with high-dielectric constant ceramics to realize miniaturized microwave bandpass filters. Some theoretical calculations for coaxial resonators are also presented in diagrams to show a correct design optimization of coaxial miniaturized filters. The formulas presented in this paper take into account the imaginary component of the characteristic impedance Z of the lines constituting the resonator; the results previously presented by other authors neglected such an imaginary component of Z. The relevant influence that this imaginary component has for the calculation of the correct unloaded Q of the resonator is pointed out by this paper through a comparison between correct calculations and calculations performed by neglecting the imaginary component of Z. Some experimental results are compared with theoretical calculations.

Independent tuning of quality factor and unity-gain frequency in a transconductance-capacitance integrator

Abstract: It is shown that the quality factor and unity-gain frequency of a recently proposed transconductance-capacitance integrator can be tuned practically independently of each other, without using extra devices. Computer simulation is used to verify the concept.

Quality factor of the piezoelectric thin film on semiconductor composite resonator resulting from radiation into the semiconductor wafer

Abstract: The composite resonator consists of a uniform thin layer etched in a small well‐defined region of a semiconductor wafer to form a diaphragm, upon which is deposited a thin piezoelectric film along with the electrodes to form a resonant region directly on the wafer. Although the composite resonator, which operates in an essentially thickness‐extensional mode, can be constructed to employ energy trapping, almost all existing experimental work in the literature is for the case when trapping is not present. All previous analytical work expressly ignores radiation into the bulk semiconductor except one treatment, which unrealistically ignores the junction between the etched diaphragm and the bulk semiconductor. In this work an analysis of the composite resonator driven into essentially thickness‐extensional vibrations by the application of a voltage to strip electrodes is performed. The analysis includes all radiating plate waves in the thick portion of the semiconductor. The solution consists of a sum of term...

Planar Radial Resonator Oscillator

Abstract: The input and output coupling coefficients associated with planar radial resonator oscillator having two degrees of freedom are derived. It is shown, that (a) the input coupling coefficient can be controlled by the separation between the centers of the radial disk resonator and the active device and (b) the output coupling coefficient is controlled by the amount of overlap between the radial disk resonator and the inner conductor of the microstrip transmission media.

Threshold power transfer for the gyrotron and peniotron oscillators operating at the harmonic cyclotron frequencies using coaxial electron beam-circuit configurations

Abstract: Recently we have solved for the linearized displacement in a thin beam in a constant axial magnetic field inside a cylindrical waveguide propagating TEsn or TMsn waveguide mode [Shrivastava and Grow (1984)]. The displacement vector indicates the existence of two modes at the s harmonic and one mode each at (s + 1) and (s − 1) harmonics of the cyclotron frequency. This paper extends the analysis for the start oscillation conditions for the monotrons based on these interactions. Using the polarization variable approach, the RF surface current density is evaluated in terms of the RF displacement. Then the RF beam power transfer in terms of TEsnl or TMsnl mode, is evaluated for each of these interactions. The power transfer is also evaluated for a magnetron resonator supporting TE-mode RF fields. A method to evaluate threshold DC beam power in terms of the RF beam power transfer, Q factor, and the stored energy in the resonator is suggested. Good agreements between this theory with other published re...

Low power measurements of the quality factor of an open resonator with stepped mirrors

Abstract: Open resonators in which both mirrors have a central step have been predicted to exhibit mode selection properties. This is advantageous for the design of quasi-optical gyrotrons. Quality factor measurements of a 36 cm resonator at 120 GHz are presented and compared with theory. Although the effect of the step is clearly seen, the quality factor Q of the resonator is lower than that predicted.

Automatic technique for the characterisation of a dielectric resonator coupled to a microstrip line

Abstract: An automatic computer controlled technique is proposed to measure the resonant frequency, loaded quality factor and coupling factor of a dielectric resonator coupled to a microstrip line. The complex transmission coefficient of the system is measured, as a function of frequency, by means of a network analyzer. At each frequency, the reflection coefficient is calculated and its magnitude is processed to obtain the characteristic parameters of the resonator. Estimated errors for Q- and coupling factors are in the order of 1% and for the resonance frequency are about 1 part in 106.

Linearly frequency-modulated high-frequency oscillator with high external Q factor

Abstract: A high-frequency modulator which is linearly modulated in a frequency range around a center frequency and comprises a high-gain field effect transistor whose output is fed-back to the input from a coupler constituted by two relatively fine lines which are sufficiently remote from each other to provide that at the input of the transistor the majority of the high power available at its output is reinjected, and thus a high external Q factor is obtained. The modulation circuit which is arranged in parallel with the feedback network includes a varicap which is arranged in series with three line elements and a fixed capacitor calculated for optimizing the linearity of the frequency modulation as a function of the control voltage of the varicap. The circuit may be used for example, in equipment such as radio altimeter sources or proximity fuses, auto-directional systems and long-range radar.

Device for measuring the magnetic properties of layers, which are applied by sputtering or vapour-deposition, during the machining process

Abstract: In order to measure the magnetic properties of layers, which are applied by means of sputtering or vapour-deposition and consist of magnetic material, it is proposed to arrange a coil within the vacuum chamber, for example as a component of an oscillator circuit whose element which governs the frequency is a tuned circuit having the coil and a capacitor. The coil is acted on by the deposited magnetic material. This changes the inductance and quality (Q factor) of the coil, the quality and the resonant frequency of the tuned circuit, and the frequency and the output voltage of the oscillator circuit as a function of the magnetic properties of the deposited material. These changes are measured, evaluated and used for controlling the coating process.

Resonant cylinder for internal friction measurement

Abstract: Similar to the resonant‐sphere method in its experimental aspect, a resonant‐cylinder technique is developed for the measurement of the internal friction of solids. The solutions of the theoretical problems of using the cylinder instead of sphere are presented: the computation of the resonance spectrum of the cylinder (axially symmetric modes only); the evaluation of the Q factor from the experimental resonance spectrum, characterized by a low (peak/background) ratio; and the separation of the dilatational and shear oscillation components in the total value of internal friction, measured for a given resonance mode. The anisotropy of viscoelastic parameters in a rolled bar of commercial steel has been measured as a method sensitivity check. Other preliminary experimental data are also presented as illustrative examples.

Measurement of the Complex Permittivity of Curved Dielectric Radome Specimens using an Open Resonator

Abstract: A technique for the measurement of the complex permittivity of curved dielectric radome specimens using an open resonator is reported. By using perturbation theory, a modified compensation term has been derived to deal with relatively large deviation of the specimen geometry from that ideally required in such measurements. Preliminary measurements, made at 11.6 GHz on concave perspex samples having various radii of curvature down to 300mm and with a judicious choice of resonator configuration, show errors in the relative permittivity and loss tangent of less than 3% and 20% respectively. The large errors in the loss tangent are thought to be due to the energy refracted out of the resonator not yet having been taken into account.

External Q of probe-coupled dielectric resonator

Abstract: We have investigated the external Q of the dielectric resonator considering the probe length and probe distance between the resonator. The input impedance is calculated using Green's function and the current distribution on the probe.

Fabry–Perot resonator with volume-distributed phase inhomogeneities

Abstract: The Born approximation is used to solve the problem of the influence of inhomogeneities of the refractive index of a medium filling a resonator on the resonator parameters. The attention is concentrated on finding the effective optical path (phase fluctuations) allowing for diffraction, which should give the expression for the Q factor of a resonator with an inhomogeneous medium. It is shown that diffraction has a positive influence reducing the role of distributed homogeneities and thus increasing the Q factor.

Circular cylindrical cavity loaded with a dielectric sleeve for Gunn-effect oscillator stabilisation application

Abstract: A circular cylindrical cavity is loaded with a dielectric sleeve which has a length shorter than that of the cavity. In general, the unloaded sections of the cavity can be such that the pure H11 mode is either propagating or cutoff at the resonance frequency of the loaded cavity, but the emphasis in the paper will be on the cutoff case. An electromagnetic model of this cavity structure is developed using the modal-matching method. The possibility of using the cutoff version of the sleeve-loaded cavity for stabilising the frequency of a microwave solid-state oscillator is investigated experimentally.

Analysis of the Coupling Coefficient Between a Cylindrical Dielectric Resonator and a Fin-Line

Abstract: The external quality factor of a cylindrical dielectric resonator coupled to a finline is evaluated using the finite element method to analyse the transmission line and the resonator. The effects of varying the location of the resonator on the coupling are studied. Experimental results compared with the theoretical ones are presented.

A low-sensitivity, low-capacitance ratio realization of high-Q biquads

Abstract: A new biquad configuration with inherent low sensitivities and low capacitor area for high- Q equalizers is proposed. A simple procedure for optimal design is presented and the design example is compared with that of Laker et al [1]. The results show that apart from low sensitivities, the new configuration saves more than 50 percent total capacitor area over what is achieved in [1].

Fabry–Perot interferometer with random phase inhomogeneities

Abstract: A study is made of the influence of phase inhomogeneities of mirrors in a Fabry–Perot interferometer on its pass band, average intensity (transfer function) and variance of the intensity fluctuations. A study is made of phase inhomogeneities with a Gaussian statistics and also in the form of a random stop process. In the latter case the role of phase fluctuations increases on expansion of the beam. The results obtained are of interest when a Fabry–Perot interferometer is used as a resonator. An expression is obtained for the Q factor of the resonator and this expression allows for phase inhomogeneities of the mirrors.

Non-piezoelectric resonator with a high Q factor

Abstract: Resonator non-piezoelectric material to large quality factor. The resonator (10) comprises a single crystal (11) of a non-piezoelectric material having a low attenuation of the elastic waves of volume, such as corundum, single crystal support means fixed to the latter in the points corresponding to nodes of vibration, thermal means (40) for directly cause own excitation of the single crystal (11) and optical means (50) for contactless detection, periodic displacement of the resonator. Application in particular to the realization of oscillators.

Computer Controlled System of Open Resonators Having a Fast Measurement Capability at Microwave and Millimetre Wave Frequencies

Abstract: A system of three open resonators which is controlled by a microprocessor is described. This facility allows simultaneous measurements of scattering phenomena to be made at chosen frequencies within the range of 10 GHz to 90 GHz. The microprocessor records the experimental data and provides output of results in graphical form either directly or in association with a mainframe computer. The system provides an advance in open resonator technology, allowing measurements to be made very quickly and at frequencies widely separated over the microwave and millimetre-wave bands.