A parallel resonant circuit with excellent distortion and saturation characteristics is provided at low power consumption. A first power-supply voltage is applied to the parallel resonant circuit. In the parallel resonant circuit, a variable resistor includes one or more parallel-connected branches. Each of the branches includes a series circuit of a resistor and a MOS switch. A second power supply supplies power of control signals applied to respective gates of the MOS switches, and supplies back gate voltages to the MOS switches. A power-supply voltage of the second power supply is higher than the first power-supply voltage.

A parallel resonant circuit with excellent distortion and saturation characteristics is provided at low power consumption. A first power-supply voltage is applied to the parallel resonant circuit. In the parallel resonant circuit, a variable resistor includes one or more parallel-connected branches. Each of the branches includes a series circuit of a resistor and a MOS switch. A second power supply supplies power of control signals applied to respective gates of the MOS switches, and supplies back gate voltages to the MOS switches. A power-supply voltage of the second power supply is higher than the first power-supply voltage.

A device comprises a first capacitor block comprising a plurality of first capacitors connected in a first configuration, a second capacitor block comprising a plurality of second capacitors connected in the first configuration, a third capacitor block comprising a plurality of third capacitors connected in a second configuration, a fourth capacitor block comprising a plurality of fourth capacitors connected in the second configuration, a first switch connected between the first capacitor block and the second capacitor block, a second switch connected between the third capacitor block and the fourth capacitor block, a third switch connected between the first capacitor block and the fourth capacitor block and a fourth switch connected between the third capacitor block and the second capacitor block.

A compact mobile high-frequency Antenna that quickly and quietly self-adjusts to minimize Voltage Standing Wave Ratio (VSWR). Includes a compact tuning coil and a rolling contact. A Reentrant cap serves as a capacitive top hat. A spiral cut enhances the efficiency is this very short antenna. A tough insulating tube covers the antenna to serve as a radome protect the user from RF burns. The use of rolling contacts on a smooth inside diameter of the tuning coil greatly reduces the force to move the contactor as well as the acoustical noise generated when tuning. A controller drives a servo motor to position the contactor to the optimal position within the tuning coil and selects the impedance to connect between the unused end of the tuning coil and the feed point of the antenna to optimize VSWR.

A compact mobile high-frequency Antenna that quickly and quietly self-adjusts to minimize Voltage Standing Wave Ratio (VSWR). Includes a compact tuning coil and a rolling contact. A Reentrant cap serves as a capacitive top hat. A spiral cut enhances the efficiency is this very short antenna. A tough insulating tube covers the antenna to serve as a radome protect the user from RF burns. The use of rolling contacts on a smooth inside diameter of the tuning coil greatly reduces the force to move the contactor as well as the acoustical noise generated when tuning. A controller drives a servo motor to position the contactor to the optimal position within the tuning coil and selects the impedance to connect between the unused end of the tuning coil and the feed point of the antenna to optimize VSWR.

A compact mobile high-frequency Antenna that quickly and quietly self-adjusts to minimize Voltage Standing Wave Ratio (VSWR). Includes a compact tuning coil and a rolling contact. A Reentrant cap serves as a capacitive top hat. A spiral cut enhances the efficiency is this very short antenna. A tough insulating tube covers the antenna to serve as a radome protect the user from RF burns. The use of rolling contacts on a smooth inside diameter of the tuning coil greatly reduces the force to move the contactor as well as the acoustical noise generated when tuning. A controller drives a servo motor to position the contactor to the optimal position within the tuning coil and selects the impedance to connect between the unused end of the tuning coil and the feed point of the antenna to optimize VSWR.

A compact mobile high-frequency Antenna that quickly and quietly self-adjusts to minimize Voltage Standing Wave Ratio (VSWR). Includes a compact tuning coil and a rolling contact. A Reentrant cap serves as a capacitive top hat. A spiral cut enhances the efficiency is this very short antenna. A tough insulating tube covers the antenna to serve as a radome protect the user from RF burns. The use of rolling contacts on a smooth inside diameter of the tuning coil greatly reduces the force to move the contactor as well as the acoustical noise generated when tuning. A controller drives a servo motor to position the contactor to the optimal position within the tuning coil and selects the impedance to connect between the unused end of the tuning coil and the feed point of the antenna to optimize VSWR.

Disclosed are a capacitive element (CE) and a circuit structure including CE(s). The CE includes series-connected first, second, and third transistors (dual-gate n-type field effect transistors). Shared source/drain regions between the second and first transistors and between the first and third transistors are connected to capacitors, respectively. The first transistor is larger than the second and third transistors. The front gate of the first transistor and back gates of all three transistors receive a first control voltage (VC1). The front gates of the second and third transistors receive a second control voltage (VC2). VC1 and VC2 are concurrently switchable to concurrently switch the three transistors between on and off states. High and low voltage levels of VC1 are at a first positive voltage level and at ground. High and low voltage levels of VC2 are at the first positive voltage level and at a second positive voltage level.