R-F switching circuit

Claim 2

In an electronic switching system comprising a source of at least one radio-frequency signal, utilization means for at least a portion of said radio-frequency signal, an insulated-gate field effect transistor with source and drain electrodes and a transmission channel of variable conductivity therebetween and with a gate electrode for controlling the conductivity of its transmission channel, said field-effect transistor having a source-to-drain capacitance and having a gate-to-channel capacitance including gate-to-source capacitance and gate-todrain capacitance components thereof, means for selectably coupling said source of radio-frequency signal and said utilization means in loop including said transmission channel, means for selectably applying a first or a second potential level to said gate electrode, said first potential level being of a polarity with respect to said radio-frequency signal as applied with respect to said transmission channel to render said transmission channel relatively conductive when applied to said gate electrode, said second potential level being of a polarity with respect to said radio-frequency signal as applied to said transmission channel to render said transmission channel relatively non-conductive when applied to said gate electrode, the improvement wherein said means for selectably applying a first or a second potential level applies said first potential level to said gate electrode at an impedance level higher for said radio-frequency signal than that presented by its gate-tochannel capacitance and applies said second potential level to said gate electrode at an impedance level lower for said radiofrequency signal than that presented by each of its said gate-tosource and gate-to-drain capacitances.

Claim 3

The improvement set forth in claim 1 wherein said means for selectably applying a first and a second potential comprises: an auxiliary transistor of the same conductivity type as said insulated-gate field-effect transistor, said auxiliary transistor having a principal conduction path between first and Second electrodes and having a control electrode, the conductance of said principal conduction path being responsive to potential applied between said control and first electrodes, said second electrode being connected to said gate electrode; a resistive element having a resistance higher than the impedance of said gate-to-channel capacitance for said radio-frequency signal, said resistive element being connected between said first and said second electrodes of said auxiliary transistor; means for selectably applying said first and said second potential to said first electrode of said auxiliary transistor at an impedance level for said radio-frequency signal lower than that of each of said gate-to-source and gate-to-drain capacitances; and means for applying a potential to said control electrode of said auxiliary transistor such that it is rendered relatively non-conductive when said first potential level is applied to its first electrode and relatively conductive when said second potential level is applied to its first electrode.

Claim 4

The improvement set forth in claim 2 wherein: said auxiliary transistor is of an insulated-gate field effect type and is formed together with said insulated gate field-effect transistor in an MOS integrated circuit, and a digital control apparatus provides first and second complementary logic output signals each switchable between said first and second potential levels, said first and said second output signals thereof being applied respectively to the first electrode and to the control electrode of said auxiliary transistor.

Claim 5

The improvement claimed in claim 3 wherein: a by-pass capacitor couples the first electrode of said auxiliary transistor to a radio-frequency signal ground.

Claim 6

Switching apparatus for selectably connecting an input terminal for an r-f signal to an output terminal, comprising, in combination: a field-effect transistor having a conduction path connected at one end to said input terminal and at its other end to said output terminal and having also a control electrode for controlling the impedance of said path; relatively high r-f impedance circuit means; relatively low r-f impedance circuit means; means for concurrently applying a control signal to said control electrode of a sense to place said conduction path in a relatively low r-f impedance condition while connecting said relatively high r-f impedance means between said control electrode and r-f ground; and means for concurrently applying a control signal to said control electrode of a sense to place said conduction path in a relatively high r-f impedance condition while connecting said relatively low r-f impedance means between said control electrode and r-f ground.

Claim 7

Switching apparatus for selectably connecting an input terminal for an r-f signal to an output terminal, comprising, in combination: a field-effect transistor having a conduction path connected at one end to said input terminal and at its other end to said output terminal and having also a control electrode for controlling the impedance of said path; relatively high r-f impedance circuit means; relatively low r-f impedance circuit means; means for concurrently applying a control signal to said control electrode of a sense to place said conduction path in a relatively low r-f impedance condition while connecting said relatively high r-f impedance means between said control electrode and r-f ground; and means for concurrently applying a control signal to said control electrode of a sense to place said conduction path in a relatively high r-f impedance condition while connecting said relatively low r-f impedance means between said control electrode and r-f ground.

Claim 8

Switching apparatus for selectably connecting an input terminal for an r-f signal to an output terminal comprising, in combination: a field-effect transistor having a conduction path connected at one end to said input terminal and at its other end to said output terminal and having also a control electrode for controlling the impedance of said path; means for applying control signals to said control electrode for switching said conduction path between relatively high and relatively low impedance conditions; and means for connecting said control electrode to r-f ground via a relatively low r-f impedance path when said conduction path is in its relatively high impedance condition and via a relatively high r-f impedance path when said conduction path is in its relatively low impedance condition.

Claim 9

Switching apparatus for selectably connecting an input terminal for an r-f signal to an output terminal comprising, in combination: a field-effect transistor having a conduction path connected at one end to said input terminal and at its other end to said output terminal and having also a control electrode for controlling the impedance of said path; means for applying control signals to said control electrode for switching said conduction path between relatively high and relatively low impedance conditions; and means for connecting said control electrode to r-f ground via a relatively low r-f impedance path when said conduction path is in its relatively high impedance condition and via a relatively high r-f impedance path when said conduction path is in its relatively low impedance condition.

Claim 10

Swtiching apparatus for selectably connecting an input terminal for an r-f signal to an output terminal comprising, in combination: a field-effect transistor having a channel connected between said input and said output terminals and having a gate electrode for controlling the conduction of said channel, and a source for controllably and alternatively applying a first control potential to said gate electrode of a sense to make said channel conductive or applying a second control potential to said gate electrode of a sense to make said channel non-conductive, said source characterized by offering a high impedance to r-f signal when applying said first potential and a low impedance to r-f signal when applying said second potential.

Claim 11

Swtiching apparatus for selectably connecting an input terminal for an r-f signal to an output terminal comprising, in combination: a field-effect transistor having a channel connected between said input and said output terminals and having a gate electrode for controlling the conduction of said channel, and a source for controllably and alternatively applying a first control potential to said gate electrode of a sense to make said channel conductive or applying a second control potential to said gate electrode of a sense to make said channel non-conductive, said source characterized by offering a high impedance to r-f signal when applying said first potential and a low impedance to r-f signal when applying said second potential.

Claim 12

Swtiching apparatus for selectably connecting an input terminal for r-f signal to an output terminal comprising, in combination: a field-effect transistor having a channel connected between said input and said output terminals and having a gate electrode for controlling the conduction of said channel, a source for applying a first control potential to said gate electrode, of a sense to make said channel conductive and at relatively high r-f impedance; and a source for controllably applying a second control potential to said gate electrode, of a sense to make said channel non-conductive and at relatively low r-f impedance.

Claim 13

Swtiching apparatus for selectably connecting an input terminal for r-f signal to an output terminal comprising, in combination: a field-effect transistor having a channel connected between said input and said output terminals and having a gate electrode for controlling the conduction of said channel, a source for applying a first control potential to said gate electrode, of a sense to make said channel conductive and at relatively high r-f impedance; and a source for controllably applying a second control potential to said gate electrode, of a sense to make said channel non-conductive and at relatively low r-f impedance.

Claim 14

A radio-frequency signal selector system comprising: means for supplying radio-frequency signals of which one is to be selected; a plurality of radio-frequency amplifiers tuned to different portions of the frequency spectrum from each other, each having an input circuit and an output circuit; a plurality of insulated-gate field-effect transistors, each having source and drain electrodes and a transmission channel therebetween, each having its transmission channel connecting said means for supplying radio-frequency signals to a respective input circuit of one of said radio-frequency amplifiers, each having a gate electrode for controlling the conductivity of its transmission channel, each having a source-to-drain capacitance, each having a gate-to-channel capacitance including gate-to-source capacitance and gate-to-drain capacitance components thereof; and frequency selection circuitry means for selectably applying a first potential level to the gate electrode of a selected one of said plurality of field-effect transistors, from an impedance higher at said radio-frequencies than the gate-to-channel capacitance of said selected field-effect transistor, and applying a second potential level to the gate electrode of each non-selected one of said plurality of field-effect transistors, from an impedance lower at said radio frequencies than that presented by its respective said gate-to-source and gate-to-drain capacitances, the polarity and value of said first potential level chosen with respect to the potential exhibited by said supplied radio-frequency signals to render the transmission channel of said selected field-effect transistor relatively conductive and the polarity of and value of said second potential level chosen with respect to the potential exhibited by said supplied radio-frequency signals to render the transmission channels of said non-selected field-effect transistors relatively non-conductive.

Claim 15

A radio-frequency signal selector system comprising: means for supplying radio-frequency signals of which one is to be selected; a plurality of radio-frequency amplifiers tuned to different portions of the frequency spectrum from each other, each having an input circuit and an output circuit; a plurality of insulated-gate field-effect transistors, each having source and drain electrodes and a transmission channel therebetween, each having its transmission channel connecting said means for supplying radio-frequency signals to a respective input circuit of one of said radio-frequency amplifiers, each having a gate electrode for controlling the conductivity of its transmission channel, each having a source-to-drain capacitance, each having a gate-to-channel capacitance including gate-to-source capacitance and gate-to-drain capacitance components thereof; and frequency selection circuitry means for selectably applying a first potential level to the gate electrode of a selected one of said plurality of field-effect transistors, from an impedance higher at said radio-frequencies than the gate-to-channel capacitance of said selected field-effect transistor, and applying a second potential level to the gate electrode of each non-selected one of said plurality of field-effect transistors, from an impedance lower at said radio frequencies than that presented by its respective said gate-to-source and gate-to-drain capacitances, the polarity and value of said first potential level chosen with respect to the potential exhibited by said supplied radio-frequency signals to render the transmission channel of said selected field-effect transistor relatively conductive and the polarity of and value of said second potential level chosen with respect to the potential exhibited by said supplied radio-frequency signals to render the transmission channels of said non-selected field-effect transistors relatively non-conductive.

Claim 16

A radio-frequency signal selector system comprising: means for supplying radio-frequency signals of which one is to be selected; means for utilizing said selected radio-frequency signal; a plurality N in number, of radio-frequency amplifiers tuned to different portions of the frequency spectrum from each other, each having an input circuit and an output circuit; first and second pluralities, N in number, of insulated-gate field-effect transistors, each of said transistors having source and drain electrodes and a transmission channel therebetween, each of said transistors having a gate electrode for controlling the conductivity of its transmission channel, each of said transistors having a source-to-drain capacitance and having a gate-to-channel capacitance including gate-to-source capacitance and gate-to-drain capacitance components thereof, each of the transistors in said first plurality having its transmission channel connecting said means for supplying radio-frequency signals to respective input circuit of one of said radio-frequency amplifiers, and each of the fieLd-effect transistors in said second plurality having its transmission channel connecting a respective output circuit of one of said radio-frequency amplifiers to said means for utilizing said selected radio-frequency signal; and frequency selection circuitry means for selectably applying gate potentials to a selected pair of field-effect transistors to render their transmission channels relatively conductive, said selected pair being those with their transmission channels respectively connected to the input circuit and to the output circuit of the one of said radio-frequency amplifiers tuned to the portion of the frequency spectrum being selected, those gate potentials being supplied at impedances higher at said radio-frequencies than the respective gate-to-channel capacitances of said selected field-effect transistors, and for applying gate potentials to the rest of said field-effect transistors to render their transmission channels relatively non-conductive, from impedances lower at said radio-frequencies than that of its respective said gate-to-source and gate-to-drain capacitances.

Claim 17

A radio-frequency signal selector system comprising: means for supplying radio-frequency signals of which one is to be selected; means for utilizing said selected radio-frequency signal; a plurality N in number, of radio-frequency amplifiers tuned to different portions of the frequency spectrum from each other, each having an input circuit and an output circuit; first and second pluralities, N in number, of insulated-gate field-effect transistors, each of said transistors having source and drain electrodes and a transmission channel therebetween, each of said transistors having a gate electrode for controlling the conductivity of its transmission channel, each of said transistors having a source-to-drain capacitance and having a gate-to-channel capacitance including gate-to-source capacitance and gate-to-drain capacitance components thereof, each of the transistors in said first plurality having its transmission channel connecting said means for supplying radio-frequency signals to respective input circuit of one of said radio-frequency amplifiers, and each of the fieLd-effect transistors in said second plurality having its transmission channel connecting a respective output circuit of one of said radio-frequency amplifiers to said means for utilizing said selected radio-frequency signal; and frequency selection circuitry means for selectably applying gate potentials to a selected pair of field-effect transistors to render their transmission channels relatively conductive, said selected pair being those with their transmission channels respectively connected to the input circuit and to the output circuit of the one of said radio-frequency amplifiers tuned to the portion of the frequency spectrum being selected, those gate potentials being supplied at impedances higher at said radio-frequencies than the respective gate-to-channel capacitances of said selected field-effect transistors, and for applying gate potentials to the rest of said field-effect transistors to render their transmission channels relatively non-conductive, from impedances lower at said radio-frequencies than that of its respective said gate-to-source and gate-to-drain capacitances.