High Q structure

• US 6,433,658 B1
• Filed: 04/04/2000
• Issued: 08/13/2002
• Est. Priority Date: 01/25/2000
• Status: Expired due to Term

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Rastegar, Ali
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): TAKAOKA, DEAN O
• Application Number:
  US09/542,183
• Publication Number:
  US 20020060601A1
• Time in Patent Office: 861 Days
• Field of Search: 334/55, 333/174, 327/337, 327/94, 327/554, 327/345
• US Class Current: 334/55
• CPC Class Codes: H03B 2201/0208 the means being an element with a variable capacitance, e.g. capacitance diode
• CPC Class Codes: H03B 2201/025 the means being an electronic switch for switching in or out oscillator elements
• CPC Class Codes: H03B 2201/0266 the means comprising a transistor
• CPC Class Codes: H03B 5/08 with frequency-determining element comprising lumped inductance and capacitance
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 3/191 Tuned amplifiers H03F3/193, H03F3/195 take precedence
• CPC Class Codes: H03J 1/0008 using a central processing unit, e.g. a microprocessor digital tuning in general H03J5/0245
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H03J 5/246 using electronic means H03J5/244 takes precedence
• CPC Class Codes: H03M 1/804 with charge redistribution

Abstract

A structure (110, 150) for enhancing the quality factor (Q) of a capacitive circuit (112, 152). The capacitive circuit (112, 152) includes a first resistance (122, 164), a capacitance (124, 166), and a second resistance (126, 168). The capacitance (124, 166) represents the net capacitance of the capacitive circuit (112, 152), and the first resistance (122, 164) and second resistance (126, 168) represent elements of the intrinsic resistance of the capacitive circuit (112, 152). In a one embodiment the structure (110) includes a first capacitor (128) which is connected in parallel with the capacitive circuit (112), and second capacitor (130) which is connected in series with the capacitive circuit (112). In a second embodiment the structure (150) includes a first inductor (164), connected in series between the capacitive circuit (152) and a node (162) where the first capacitor (174) and one end of the second capacitor (176) connect, and a second inductor (172) connected in series between the capacitive circuit (152) and the other end of the second capacitor (130).

Claims

1. A quality factor enhancing structure for a capacitive circuit exhibiting a first internal resistance, an internal capacitance, and a second internal resistance in series between a first node and a second node, the structure comprising:

a first terminal node and a second terminal node;

a first capacitor having a first pole and a second pole;

said first pole of said first capacitor being directly connected to said first terminal node;

said second pole of said first capacitor being directly connected to the first node of the capacitive circuit;

a second capacitor having a first pole and a second pole;

said first pole of said second capacitor being directly connected to the first node of the capacitive circuit;

said second pole of said second capacitor being directly connected to said second terminal node; and

said second terminal node being directly connected to the second node of the capacitive circuit.

2. The structure of claim 1, further comprising an inductor, said inductor being directly connected between the first node of the capacitive circuit and both of said second pole of said first capacitor and said first pole of said second capacitor.

3. The structure of claim 1, further comprising an inductor, said inductor being directly connected between the second node of the capacitive circuit and both of said second pole of said second capacitor and said second terminal node.

4. The structure of claim 1, further comprising:

a first inductor;

said first inductor being directly connected between the first node of the capacitive circuit and both of said second pole of said first capacitor and said first pole of said second capacitor;

a second conductor; and

said second inductor being directly connected between the second node of the capacitive circuit and both of said second pole of said second capacitor and said second terminal node.

5. The structure of claim 1, wherein the capacitive circuit has intrinsic resistance consisting of the first internal resistance and the second internal resistance together.

6. The structure of claim 5, wherein at least one of the first internal resistance or the second internal resistance is contributed to by resistance through at least one switch connecting the internal capacitance to the first node.

7. The structure of claim 6, wherein the capacitive circuit includes a first set of at least one of the switches and the first set directly connects the internal capacitance to the first node in a manner contributing resistance to the first internal resistance.

8. The structure of claim 7, wherein the capacitive circuit further includes a second set of at least one of the switches and the second set directly connects the internal capacitance to the second node in a manner contributing resistance to the second internal resistance.

9. The structure of claim 1, wherein:

the capacitive circuit includes an electronically trimable capacitor exhibiting a unit capacitance; and

the electronically trimable capacitor includes a plurality of branches each including an increment capacitor directly connected in series with a switch, wherein the respective switches permit electrically directly connecting the respective branches so that the respective increment capacitors contribute to the unit capacitance selectively.

10. The structure of claim 1, wherein the capacitive circuit includes a trim capacitor and the structure directly connects into a tuning circuit at said first terminal node and said second terminal node.