Abstract: A variable capacitor includes: capacitors connected in series between first and second signal terminals, capacitances of the capacitors varying in accordance with variable voltage applied to a variable terminal; a first resistor connected between a first node between adjacent capacitors of the capacitors and the variable terminal, a second resistor connected between a second node between adjacent capacitors of the capacitors and a fixed terminal applied with fixed voltage, and a third resistor connected between a third node and the fixed terminal, the third node being located between the first and/or second signal terminal and a capacitor located closest to the first and/or signal terminal among the capacitors, wherein a resistance of the second resistor is less than 1 and ½ or greater with respect to a resistance of the third resistor, and the resistance of the second resistor is not equal to a resistance of the first resistor.

Abstract: A tunable LC circuit is used to trigger an electron discharge from an accelerator device, such as a Betatron. The circuit includes a coil as a first inductor having a first inductance electrically coupled in series with a capacitor. A second inductor having a variable inductance is electrically coupled, either in series or parallel, to the first inductor. The time to capacitor discharge is governed by: ?LC=?{square root over ((L+LTUNE)C)}. Adjusting the inductance of the variable inductor (LTUNE) facilitates continuous adjustment of the discharge time. This is particularly useful when the LC values change in response to external stimuli, such as borehole temperature when a Betatron is used to log borehole features.

Abstract: A Radio Frequency (RF) circuit includes an active portion and a tuned portion. The active portion receives an RF signal and that operates upon the RF signal. The tuned portion couples to the active portion and includes a first inductor, a second inductor, and a switch. When the switch is closed, the second inductor couples to the first inductor and the tuned portion has first tuning characteristics. When the switch is open, the second inductor is decoupled from the first inductor and the tuned portion has second tuning characteristics. The tuned portion may include lumped or parasitic capacitance. The tuned portion alternately includes an inductor having a first terminal, a second terminal, an intermediate tap, and a switch that couples between the second terminal and the intermediate tap. When the switch is closed the tuned portion has first tuning characteristics and when the switch is open, the tuned portion has second tuning characteristics.

Abstract: A segmented inductor for use with a tuning circuit, a method of increasing a self-resonant frequency of a tuning circuit and an oscillator employing the circuit and method. In one embodiment, the tuning circuit includes a first inductive element having a first intrinsic shunt capacitance. The tuning circuit also includes a second inductive element, coupled in series with the first inductive element, having a second intrinsic shunt capacitance. The first and second inductive elements cooperate to reduce a total shunt capacitance associated therewith thereby increasing a self-resonant frequency of the tuning circuit.

Abstract: The invention relates to a resonator (200,300) with variable resonance frequency, intended for connection to an amplifier, thus forming an oscillator, said resonator comprising a resonator circuit (205,305) for deciding the resonance frequency of the resonator and the oscillator, said resonator circuit comprising an inductance (L), a variable capacitance (Cj), and means (Vtune) for varying the capacitance. The resonator also comprises connection means (C1, Ck; C1, Ck, C2) for connecting the resonator to an amplifier. The resonator is provided with means (Vtune) for varying the capacitance of the connection means in proportion to the variation of the capacitance (Cj) of the resonator circuit. Preferably, the means (Vtune) for varying the capacitance (Ck) of the connection means are arranged such that an essentially constant relationship (Ck/Cj) is maintained between the capacitance (Ck) of the connection means and the first capacitance (Cj) of the resonator across all resonance frequencies.

Abstract: A double-tuned circuit of a tuner that can be switched for tuning to a plurality of frequency bands by turning a switching diode ON or OFF restrains degradation of a selectivity caused by an undesirable additional tuning circuit or parasitic tuning circuit formed by a capacitance generated when the switching diode is OFF and inter-terminal capacitance of a resistor. A double-tuned circuit of a tuner is also provided that exhibits good selectivity with reduced damping to a tuning circuit in a low-band receiving mode, and also exhibits a wider tuning range. A feed resistor for high-band receiving is directly connected to a switching diode in a primary tuning circuit, and the feed resistor for high-band receiving is connected to a switching diode via a coil in a secondary tuning circuit.

Abstract: The relationship between the input and output of a signal transfer circuit, such as a tune circuit, a filter, a phase shifter, an amplifier, etc., is determined by the circuit response to the input signal. The value of the circuit response (R) is controlled by the value (V) of a control signal supplied thereto. According to the invention, the relationship between the latter values is approximated by a linear regression function based on a number of measured first pairs of response/control signal values and based on such regression function a transcoder determines control signal values for providing response values of the circuit in accordance with second pairs of response/control signal values.

Abstract: An RF signal input circuit for a UHF tuner of a television receiver comprises a series-tuned circuit including a varactor diode and an inductance element connected in series, in the order named, between signal ground and a gate electrode of a field-effect transistor RF amplifier. The series-tuned circuit has a relatively uniform bandwidth throughout the UHF range. A capacitor connected in shunt with the gate electrode completes a "split-capacitor" configuration in which the varactor diode and the shunt capacitor form a variable impedance transformation network for making the relationship between the effective impedances of the series-tuned circuit and FET amplifier relatively uniform throughout the UHF range. The order of the varactor diode and inductance element allows a low cost adjustable capacitor comprising a grounded shield wall as one plate and a movable tab as a second plate to be connected directly across the varactor diode.