System and method for a switchable capacitance

Patent metadata

Field	Value
Publication number	US-9281802-B2
Application number	US-201313894096-A
Country	US
Kind code	B2
Filing date	May 14, 2013
Priority date	May 14, 2013
Publication date	Mar 8, 2016
Grant date	Mar 8, 2016

Abstract

In accordance with an embodiment, a switchable capacitance circuit includes a plurality of capacitance-switch cells that each has a first semiconductor switching circuit and a capacitance circuit having a first terminal coupled to the first semiconductor switching circuit. A resistance of the first semiconductor switching circuit of a first switch-capacitance cell of the plurality of capacitance-switch cells is within a first tolerance of a resistance of the first semiconductor switching circuit of a second capacitance-switch cell of the plurality of capacitance-switch cells, and a capacitance of the capacitance circuit of the first capacitance-switch cell is within a second tolerance of a capacitance of the capacitance circuit of the second capacitance-switch cell.

First claim

What is claimed is:

1. A switchable capacitance circuit comprising:
a plurality of capacitance-switch cells coupled to a common terminal, wherein each capacitance-switch cell comprises:
a first semiconductor switching circuit, and
a capacitance circuit having a first terminal coupled to the first semiconductor switching circuit;

wherein a resistance of the first semiconductor switching circuit of a first capacitance-switch cell of the plurality of capacitance-switch cells is substantially equal to a resistance of the first semiconductor switching circuit of a second capacitance-switch cell of the plurality of capacitance-switch cells, and a capacitance of the capacitance circuit of the first capacitance-switch cell is substantially equal to a capacitance of the capacitance circuit of the second capacitance-switch cell, and
wherein each of the plurality of capacitance-switch cells are matched cells having a same geometry, wherein a Q factor of the switchable capacitance circuit is substantially monotonic as a load capacitance is increased and decreased by switching in and out ones of the plurality of capacitance-switch cells.

2. The switchable capacitance circuit of claim 1 , wherein:
the first semiconductor switching circuit comprises a plurality of series connected semiconductor switches; and
the capacitance circuit comprises a plurality of series connected capacitors.

3. The switchable capacitance circuit of claim 2 , wherein each of the plurality of series connected semiconductor switches comprises a transistor and a resistor coupled in series with a gate of the transistor.

4. The switchable capacitance circuit of claim 2 , wherein
a number of series connected semiconductor switches is greater or equal to a maximum expected operating voltage of the switchable capacitance circuit divided by a maximum operating voltage of one of the semiconductor switches; and
a number of the series connected capacitors is greater or equal to a maximum expected operating voltage of the switchable capacitance circuit divided by a maximum operating voltage of one of the series connected capacitors.

5. The switchable capacitance circuit of claim 4 , wherein the maximum expected operating voltage is greater than 50 V.

6. The switchable capacitance circuit of claim 1 , wherein each of the plurality of capacitance-switch cells further comprises a second semiconductor switching circuit coupled to a second terminal of the capacitance circuit.

7. The switchable capacitance circuit of claim 6 , further comprising a third semiconductor switching circuit having a first end coupled to the first terminal of the capacitance circuit and a second end coupled to the second terminal of the capacitance circuit.

8. The switchable capacitance circuit of claim 7 , wherein:
the capacitance circuit comprises a metal-insulator-metal (MIM) capacitor; and
the first semiconductor switching circuit is disposed below the MIM capacitor.

9. A method of operating a switchable capacitance circuit, the method comprising:
increasing a load capacitance of the switchable capacitance circuit comprising switching-on at least one of a plurality of capacitance-switch cells coupled to a common terminal, wherein
each of the plurality of capacitance-switch cells comprises a first semiconductor switching circuit and a capacitance circuit having a first terminal coupled to the first semiconductor switching circuit, and
a resistance of the first semiconductor switching circuit of a first capacitance-switch cell of the plurality of capacitance-switch cells is substantially equal to a resistance of the first semiconductor switching circuit of a second capacitance-switch cell of the plurality of capacitance-switch cells, and a capacitance of the capacitance circuit of the first capacitance-switch cell is substantially equal to a capacitance of the capacitance circuit of the second capacitance-switch cell,
wherein each of the plurality of capacitance-switch cells are matched cells having a same geometry, and
switching-on comprises activating the first semiconductor switching circuit of the at least one of the plurality of capacitance-switch cells; and

decreasing the load capacitance of the switchable capacitance circuit comprising switching-off the at least of the plurality of capacitance-switch cells, wherein switching-off comprises deactivating the first semiconductor switching circuit of the at least one of the plurality of capacitance-switch cell, wherein a Q factor of the switchable capacitance circuit is substantially monotonic as the load capacitance is increased and decreased.

10. The method of claim 9 , wherein activating the first semiconductor switching circuit of the at least one of the plurality of capacitance-switch cells further comprises activating a plurality of semiconductor switches coupled in series.

11. The method of claim 9 , wherein:
each of the plurality of capacitance-switch cells further comprises a second semiconductor switching circuit coupled to a second terminal of the capacitance circuit; and
switching-on further comprises activating the second semiconductor switching circuit of the at least one of the plurality of capacitance-switch cells.

12. The method of claim 11 , wherein:
each of the plurality of capacitance-switch cells further comprises a bypass switch having a first end coupled to the first terminal of the capacitance circuit and a second end coupled to the second terminal of the capacitance circuit; and
the method further comprises bypassing the switchable capacitance circuit, wherein bypassing comprises activating the first semiconductor switching circuit, the second semiconductor switching circuit and the bypass switch for at least one of the plurality of capacitance-switch cells.

13. The method of claim 9 , further comprising applying a radio-frequency (RF) signal to the switchable capacitance circuit.

14. The method of claim 9 , further comprising:
coupling the switchable capacitance circuit to an antenna; and
tuning the antenna by increasing and decreasing the load capacitance of the switchable capacitance circuit.

15. The method of claim 9 , further comprising:
receiving a command from a digital interface; and
decoding the command, wherein increasing and decreasing the load capacitance further comprising selectively activating the first semiconductor switching circuit of the plurality of capacitance-switch cells according to the decoded command.

16. A tunable radio-frequency (RF) circuit comprising:
a semiconductor substrate; and
a plurality of capacitance-switch cells coupled to a common terminal and disposed on the semiconductor substrate, wherein each capacitance-switch cell comprises:
a capacitance circuit comprising a first end and a second end,
a first semiconductor switching circuit coupled between a first end of the capacitance circuit and a first output terminal of the RF circuit, and
a second semiconductor switching circuit coupled between a second end of the capacitance circuit and a second output terminal of the RF circuit;

wherein a resistance of the first semiconductor switching circuit of a first capacitance-switch cell of the plurality of capacitance-switch cells is substantially equal to a resistance of the first semiconductor switching circuit of a second capacitance-switch cell of the plurality of capacitance-switch cells, and a capacitance of the capacitance circuit of the first capacitance-switch cell is substantially equal to a capacitance of the capacitance circuit of the second capacitance-switch cell, wherein each of the plurality of capacitance-switch

Assignees

• Infineon Technologies Ag

Inventors

• Bakalski Winfried

Classifications

• H03J2200/10

  Tuning of a resonator by means of digitally controlled capacitor bank · CPC title

• H03J5/244 Primary

  using electronic means · CPC title