Self-calibrating circuit for wireless transmitter or the like

• US 20030216129A1
• Filed: 05/16/2002
• Published: 11/20/2003
• Est. Priority Date: 05/16/2002
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Chang, Tsung-Yuan, Nikjou, Bobby, Khalil, Waleed
• Granted Patent: US 7,050,781 B2
• Time in Patent Office: Days
• US Class Current: 455/197.2
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H03J 2200/29 Self-calibration of a receiver
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes

Abstract

A circuit in a wireless transmitter or other apparatus is automatically calibrated using a calibration circuit to accommodate provide a desired characteristic such as a filter response, where the component values of the filter circuit may vary such as in an integrated circuit. In one embodiment, the calibration circuit is coupled to one or more adjustable capacitors in the filter circuit to select a capacitor value so that the filter circuit exhibits the desired filter response. In one particular embodiment, the adjustable capacitor is charged in an RC circuit for each clock cycle at power up. The value of the adjustable capacitor is changed for each clock cycle until the capacitor charges to a level greater than or equal to predetermined reference voltage. When the capacitor is charged to a predetermined reference voltage, a desired capacitance value is indicated, and the adjustable capacitor is maintained at the desired capacitance value to provide the desired filter output. The calibration circuit causes the circuit to be self-calibrating to the desired characteristic such as a desired filter response.

Claims

1. An apparatus, comprising:

at least one adjustable value capacitor; and

a calibration circuit coupled to said at least one adjustable value capacitor for calibrating said at least one adjustable value capacitor to a predetermined value to provide a desired characteristic for the apparatus.

2. An apparatus as claimed in claim 1, said adjustable value capacitor comprising an array of capacitors connected in a network, each capacitor in said array of capacitors having a corresponding switch to operatively couple each corresponding capacitor to the network, each corresponding switch being controllable by said calibration circuit.

3. An apparatus as claimed in claim 1, said adjustable value capacitor comprising an array of capacitors connected in a network, each capacitor in said array of capacitors having a corresponding switch to operatively couple each corresponding capacitor to the network, each corresponding switch being controllable by said calibration circuit, said adjustable value capacitor further comprising at least one unswitched capacitor.

4. An apparatus as claimed in claim 1, further comprising a second adjustable value capacitor, said calibration circuit being connected to said second adjustable value capacitor for calibrating said second adjustable value capacitor to a predetermined value to provide a desired characteristic for the apparatus.

5. An apparatus as claimed in claim 1, further comprising a second adjustable value capacitor disposed in a feedback arrangement between the output and the input of said second amplifier, said calibration circuit being connected to said second adjustable value capacitor for calibrating said second adjustable value capacitor to a predetermined value to provide a desired characteristic for the apparatus, and a third adjustable value capacitor, said calibration circuit being connected to said second and third adjustable value capacitors for calibrating said second and third adjustable value capacitors to a predetermined value in order provide a desired characteristic for the apparatus.

6. An apparatus as claimed in claim 1, said at least one adjustable value capacitor having at least one switch being coupled to a virtual ground.

7. An apparatus as claimed in claim 1, said calibration circuit comprising means for charging said at least one adjustable value capacitor for varying values of said at least one adjustable value capacitor until said at least one adjustable value capacitor is charged to a threshold voltage within a predetermined time to select a desired value for said at least one adjustable value capacitor.

8. An apparatus as claimed in claim 1, said calibration circuit comprising a state machine structure to control charging of said at least one adjustable value capacitor for varying values of said at least one adjustable value capacitor until the adjustable value capacitor is charged to a threshold voltage within a predetermined time to select a desired value for said adjustable value capacitor.

9. A method for calibrating a circuit, comprising:

varying a value of an adjustable value component at predetermined intervals;

charging the component during each of the predetermined intervals;

measuring a level to which the component is charged during each of the predetermined intervals; and

when the component is charged to a threshold level, selecting the value of the adjustable value component that caused the component to be charged to the threshold level.

10. A method as claimed in claim 9, the adjustable value component being at least one of a capacitor, an inductor, and a resistor.

11. A method as claimed in claim 9, wherein the component is charged in one of a resistor-capacitor (RC) circuit, an inductor-capacitor (LC) circuit, a resistor-inductor (RL) circuit, and a resistor-inductor-capacitor (RLC) circuit.

12. A method as claimed in claim 9, said measuring a level to which the component is charged including comparing a voltage across the component to a threshold voltage to determine when the component is charged to threshold level.

13. An apparatus, comprising:

at least one adjustable value component; and

means for charging said at least one adjustable value component for varying values of said at least one adjustable value component until said at least one adjustable value component is charged to a threshold level within a predetermined time to select a desired value for said at least one adjustable value component.

14. An apparatus as claimed in claim 13, said means for charging comprising a comparator structure having a threshold voltage level set by a voltage divider circuit at a first input, a charging circuit structure including said at least one adjustable value component coupled to a second input of the comparator, and state machine structure to control charging of said at least one adjustable value component.

15. An apparatus as claimed in claim 13, said at least one adjustable value component being one of a resistor, a capacitor, and an inductor.

16. An apparatus as claimed in claim 13, said at least one adjustable value component being one of a resistor array, a capacitor array, and an inductor array.

17. An apparatus as clamed in claim 13, said at least one adjustable value component being one of:

a resistor array having a switch for at least one or more resistors in the resistor array to select a value of the resistor array by switching a corresponding resistor in or out of the resistor array, a capacitor array having a switch for at least one or more capacitors in the capacitor array to select a value of the capacitor array by switching a corresponding capacitor in or out of the capacitor array, and an inductor array having a switch for at least one or more inductors in the inductor array to select a value of the inductor array by switching a corresponding inductor in or out of the inductor array.

18. An apparatus, comprising:

an RC circuit in which at least one of a capacitor and a resistor is an adjustable value element to calibrate a circuit;

a circuit to vary a value of the adjustable value element according to a cycle of a clock signal to provide an updated value for the adjustable value element during successive cycles of the clock signal;

a charge control switch coupled to the RC circuit to charge and discharge the capacitor according to the clock signal; and

a comparator coupled the RC circuit at a first input and coupled to a reference voltage at a second input, to provide an output indicative of the updated value of the adjustable value element used to calibrate the circuit when the RC circuit is charged to a voltage greater than or equal to the reference voltage.

19. An apparatus as claimed in claim 18, the adjustable value element including at least one element coupled to a value selector switch to selectively connect the at least one element to at least one other element to provide an adjustable element value corresponding to a selected combination of the at least one element and the at least one other element, the circuit to vary a value of the adjustable value element including a binary counter coupled to the value selector switch to control the value of the adjustable valuable element according to an output of the binary counter.

20. An apparatus as claimed in claim 18, the adjustable value element including at least one element coupled to a value selector switch to selectively connect the at least one element to at least one other element to provide an adjustable element value corresponding to a selected combination of the at least one element and the at least one other element, the circuit to vary a value of the adjustable value element including a binary counter coupled to the value selector switch to control the value of the adjustable valuable element according to an output of the binary counter, the circuit to vary a value of the adjustable value element further including a state machine to control the binary counter and to terminate calibration of the circuit according to the output of the comparator.