Showing papers on "Q factor published in 1970"
TL;DR: In this article, it was shown that the unconstrained layer technique can be equal in damping effectiveness to the four-layer beam construction with the same total thickness of damping layers only when the modulus of elasticity of the non-constraint layer is of the same order of magnitude as for metals.
66 citations
TL;DR: In this article, positive-impedance converting networks are used to realize driving-point inductance and frequency-dependent negative resistance, and three distinct types of Q-factor behavior are derived and it is shown that extended wideband operation may be achieved such that Q factor is virtually independent of amplifier phase shift.
Abstract: Positive-impedance converting networks may be used to realize driving-point inductance and frequency-dependent negative resistance. The Q factors of these immittances are evaluated over a wide frequency range in terms of the relevant parameters. Three distinct types of Q- factor behavior are derived and it is shown that extended wide-band operation may be achieved such that Q factor is virtually independent of amplifier phase shift. The use of design-value asymptotes is explained as a means of determining the behavior of practical circuits.
52 citations
11 May 1970
TL;DR: In this paper, a new coax-waveguide configuration has been developed for the 3-7 mm band, and it has been adopted for the power source of a path-length modulation transmitter.
Abstract: It is often required that a microwave source be of high power and fixed frequency and at the same time give low noise and be highly stable. Conventional coaxial circuits are somewhat impractical at millimetre wavelengths. The "hat" has been used with some success but its tuning characteristics are not readily understood, and so it is difficult to design for specific applications. A new coax-waveguide configuration has evolved which, it is believed, satisfies these requirements rather well in the 3-7 mm band, and it has accordingly been adopted for the power source of a path-length modulation transmitter. Results obtained have shown powers of 200 mw at 5% efficiency, temperature sensitivity as low as 300 kHz/ /spl deg/C, and external Q factor around 200.
23 citations
TL;DR: Equations are derived that give the electronic tuning range of solid-state microwave oscillators in terms of the Q factor of the tuning device and the available power output and it is shown that series tuning is superior to shunt tuning.
Abstract: Equations are derived that give the electronic tuning range of solid-state microwave oscillators in terms of the Q factor of the tuning device and the available power output. For currently available varactors the tuning range is severely limited by the Q factor but some exchange of power output for the tuning range is possible. It is shown that series tuning is superior to shunt tuning.
20 citations
TL;DR: For several active-filter configurations employing operational amplifiers, the variation of resonance frequency and Q factor is given as a function of the ratio of the resonance frequency to the gain-bandwidth product of the operational amplifier.
Abstract: For several active-filter configurations employing operational amplifiers, the variation of resonance frequency and Q factor is given as a function of the ratio of the resonance frequency to the gain-bandwidth product of the operational amplifier. Consideration of these equations leads to the choice of the Wien-bridge filter or its equivalents for applications requiring a high Q factor at high frequencies.
15 citations
TL;DR: In this article, the authors derived a very simple formula for the effect of small coupling holes in the mirrors on the Q factor of open resonators and showed that the effect is very small.
Abstract: Open resonators have a number of possible applications at microwave frequencies; the very high Q factor obtainable is one attraction. Coupling to the resonator usually takes place through small coupling holes in the mirrors. An important practical question is to what extent radiation of energy out of the resonator by these holes limits the Q factor obtainable. In this letter a very simple formula is derived. The effect is shown to be very small.
9 citations
TL;DR: In this paper, the Q factor of closed resonators of 30 Ω and 50 Ω impedances has been measured over the 1-10 GHz range, and it is found that the effective r.f. conductivity is about one half that of bulk material over the major portion of the band considered.
Abstract: The letter presents the results of an investigation aimed at minimising losses in thick-film screen-printed microstrip circuits. The Q factor of closed resonators of 30 Ω and 50 Ω impedances has been measured over the 1–10 GHz range. It is found that the effective r.f. conductivity is about one half that of bulk material over the major portion of the band considered.
6 citations
TL;DR: It has been found that, except at very low density levels, the q of a given material varies only slightly as the diffuse density changes, and does, however, increase significantly as the numerical aperture of the optical system decreases.
Abstract: The rms granularity values normally produced by an optical scanner are in terms of semispecular instrument density. It is shown that these semispecular values can be converted to a diffuse density basis by dividing by a quantity q that is defined as the ratio of the instrument density of the sample to the diffuse density. The q factor has been measured by two methods, one of which is convenient for use in the routine measurement of diffuse granularity with existing equipment. It has been found that, except at very low density levels, the q of a given material varies only slightly as the diffuse density changes. It does, however, increase significantly as the numerical aperture of the optical system decreases. When a range of samples is measured, maximum values of q occur at moderate values of sample granularity.
5 citations
TL;DR: In this paper, bandpass transfer functions are obtained from an active circuit using Wien's bridge and a single operational amplifier, and the Q factor is controllable by a single resistance independently of the resonant frequency.
Abstract: Bandpass transfer functions are obtained from an active circuit using Wien's bridge and a single operational amplifier. The Q factor is controllable by a single resistance independently of the resonant frequency, and one version of the circuit has a low output impedance.
3 citations
TL;DR: In this paper, the small-signal oscillation frequency and growth rate for an avalanche diode having a general doping profile, allowing for accurate drift velocity and ionisation rate are calculated.
Abstract: The small-signal oscillation frequency and growth rate is calculated for an avalanche diode having a general doping profile, allowing for accurate drift velocity and ionisation rate. The analysis includes the case of a typical microwave load connected to the diode. A connection is found between this accurate growth rate and a properly defined Q factor for the whole circuit.
2 citations
TL;DR: In this article, a two-port active R.C. circuit with a single transistor has been analyzed in terms of twoport admittance parameters and a bandpass amplifier with such a simulated inductance has been designed and tested.
Abstract: A well-known active R.C. circuit with a single transistor gives a reasonably high value of simulated inductance with high Q, at one of its ports. This circuit has been analysed in terms of two-port admittance parameters. It has led to a new design procedure for such a circuit, to realize given values of inductance and Q factor. A bandpass amplifier with such a simulated inductance has been designed and tested.
TL;DR: In this article, it was shown that a transfer function with a high Q factor and zero sensitivity to temperature variations can be realized by an active RC circuit using a negative-immittance converter.
Abstract: It is shown that a transfer function with a high-Q factor and zero sensitivity to temperature variations can be realized by an active RC circuit using a negative-immittance converter. It is assumed that all resistors have the same temperature coefficient, and similarly with the capacitors. Experimental results confirm the theory.
TL;DR: In this article, the effect of changes in the sign and magnitude of the radius of the end surface on the frequency coefficient of the longitudinal oscillations, the temperature characteristics of the resonators, the Q factor, and the manner in which the resonance frequency varied with the position of the fixing points relative to the nodal surfaces and with the degree of beveIltng along the edge of the bar was studied.
Abstract: The bars were studied in a laboratory installation comprising a temperature-cont rol system with discrete setting of the temperature in the thermostat between 30 and 60~ a backing pump (rough vacuum line) and equipment for measuring the parameters of the quartz resonators. The temperature-regu lating system (thermostat volume 200 cm 3) is based on a proportional control system with a copper-magnesium measuring and heating bridge and a controlling magnetic amplifier having a current amplification factor of around 10,000. This arrangement gives a discrete setting of the temperature in the thermostat every 2 ~ with a nominal error of no greater than ~ 0.03~ The temperature gradient in the thermostat is no greater than - 0.02~ The control factor (coefficient) of the device is over 200. The thermostat is situated under the removable glass cover of the backing-pump system. For a pressure of some 1.33 N/m 2 under the cover the thermostat constant is equal to 33 mW/~ and the time constant for stabilizing the wall temperature of the inner thermostat is about 9 sec. Inside the thermostat is a laboratory clamp for fixing the bars. The rough vaccum system is mounted on a square metal slab fixed in level by two brackets in the main wall. There is a connection to the rough (backing-pump) vacuum system in the middle of the slab. The laboratory apparatus for measuring the parameters of the quartz resonators determines their Q-factor by the free-attenuation method [3] to an error of less than ~0.3%for various voltage on the resonators, and the resonance frequency, relative to a standard frequency of 100 kc/sec, with a relative error of some �9 1 "10 -9. We studied the effect of changes in the sign and magnitude of the radius of the end surface on the frequency coefficient of the longitudinal oscillations, the temperature characteristics of the resonators, the Q factor, and aIso the manner in which the resonance frequency varied with the position of the fixing points relative to the nodal surfaces and with the degree of beveIltng along the edge of the bar. Preliminary measurements showed that the ratio of the distance between the nodal surfaces 11 and the length of the bar along the axial direction Z0 was given by Z0 - 2ll, independently of the radius of the end surface (sign and magnitude), although the value of k0, and hence the frequency coefficient of the longitudinal oscillations of the bar,