Abstract: A programmable interrupt controller having a plurality of interrupt request inquest inputs and an interrupt request output for connection to a central processing unit (CPU) includes means for interrupting the CPU over the interrupt request output responsive to an interrupt request from any one of the interrupt request inputs and a priority resolver for assigning a priority position to each of the interrupt request inputs to create an interrupt priority hierarchy. The interrupt controller is programmable such that each interrupt request input may be independently established as responsive to either edge-triggered or level-triggered interrupt requests on a per interrupt basis. An initialization command word register of the interrupt controller has a bit corresponding to each of the interrupt request inputs. Programming each of the bits of the register to one of two states determines whether corresponding interrupt request inputs are edge-sensitive or level-sensitive.

Abstract: A apparatus is provided for estimating the position of a rotor of a commutated brushless motor operating without a shaft position sensor. The apparatus includes a tank circuit that incorporates a phase winding of the motor. A low-power signal of a frequency F.sub.1 is injected into the tank circuit. The frequency F.sub.1 is much greater than the switching frequency F.sub.s of the phase winding. Because the effective inductance (L) of the phase winding incorporated into the tank circuit changes in a cyclic manner in response to changes in the mechanical angle .THETA. of the rotor, the characteristic resonant frequency F.sub.0 of the tank circuit varies between maximum and minimum values. The effect of the variation of the resonant frequency F.sub.0 on the output characteristics of the tank circuit are used by a detection circuit to resolve the mechanical angle .THETA. of the rotor and, thereby, control the timing of the phase firing sequence.

Abstract: The invention is a grounding/positioning clip for providing a DC ground return path, low inductance AC ground path between circuit boards and for positioning electronic components in relation to an electronic device. The assembly includes a heat spreader with an electronic device mounted thereon. The leads of the electronic device are physically and electrically attached to first and second circuit boards. A clip, which has electronic components mounted thereon, fits over the electronic device thereby positioning the electronic components in correct physical relationship to the electronic device and the first and second circuit boards. Also the clip acts as a low inductance AC ground path between the first and second circuit boards and also provides a DC ground path. Preferrably the electronic device is a power transistor and the electronic components mounted on the clip are miniature compression mica capacitors for RF matching.

Abstract: A stabilization circuit is provided for use with a ferroresonant power supply to maintain a steady output voltage during power line transients, rapid load changes, or no load condition. The stabilization circuit is responsive to the voltage output of the power supply and selectively connects a load across voltage output terminals. Stabilization circuit includes a voltage sensing circuit that enables a timing circuit that activates a switch to place the load across terminals. This stabilizes the power supply, without requiring a continuously dissipative minimum load.

Abstract: The invention is a limiter circuit with dynamic hysteresis for providing improved distortion immunity at the circuit output in response to an input signal. The limiter circuit includes a positive and negative peak detector. Two weighted averages are taken of the positive and negative peaks, preferably by means of a voltage divider network. The first input to a comparator circuit receives the input signal to the limiter circuit. Different voltages from the voltage divider network are applied to the second input of the comparator circuit so as to create a dynamic hysteresis effect in the comparator circuit. The different voltages are chosen in response to the output voltage from the comparator circuit by means of an analog switch. The comparator circuit includes a fixed hysteresis voltage for stabilizing the limiter circuit at low level voltage input signals.

Abstract: A helical cavity resonator having a grounded shield, a hollow coil form and associated quarter wavelength wire coil. A non-ferrous conductive slug can be adjusted to variable positions inside the hollow coil form. Placement of the slug in a region proximate to the inside of the wire coil tunes the cavity resonator in a predominately inductive manner. Changing the slug position in the bore so that it is proximate to the shield top and removed from the inside of the wire coil tunes the cavity resonator in a predominately capacitive manner. By utilizing both inductive and capacitive tuning a helical cavity resonator with a wide tuning range is realized while maintaining a simple, inexpensive construction.

Abstract: A high frequency RF gasket is disclosed which provides an electromagnetic seal between a first and second piece of a shielding enclosure. The gasket comprises highly resilient finger projections which are attached to and project out along the perimeter of the first enclosure piece. The relative mating arrangement of the gasket, and first and second enclosure piece is such that a small force imposed on said first enclosure piece is resisted by a much larger resistance force along the longitudinal dimension of the highly resilient finger projections as the fingers engage the second enclosure piece. The larger resistance force causes sufficiently high pressure at the point of contact between the finger projections and the second enclosure piece so that the surface of the second enclosure piece yields to the finger projections.