Wireless phone system with voltage controlled oscillator

• US 6,593,826 B2
• Filed: 05/07/2001
• Issued: 07/15/2003
• Est. Priority Date: 08/02/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: See, Puay Hoe
• Primary Examiner(s): Mis, David C.
• Application Number:
  US09/850,508
• Publication Number:
  US 20010017575A1
• Time in Patent Office: 799 Days
• Field of Search: 331/36.C, 331/117.R, 331/117.FE, 331/167, 331/175, 331/179, 331/177.V, 375/295, 375/296, 375/344, 375/350, 455/255, 455/260, 455/261, 455/262
• US Class Current: 331/179
• CPC Class Codes: H03J 5/244 using electronic means
• CPC Class Codes: H03L 2207/06 Phase locked loops with a controlled oscillator having at least two frequency control terminals
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop

Abstract

An RF Voltage Controlled Oscillator (VCO) design having improved power supply noise immunity. More particularly, a VCO resonant circuit that provides a high circuit Q, immunity to noise, and is tunable over multiple distinct bands. The resonant circuit is implemented in conjunction with an integrated circuit oscillator that requires a tuned circuit to determine the frequency of operation. When the integrated circuit oscillator is used as a Local Oscillator (LO) within a wireless phone it is subjected to numerous sources of power supply noise. In a Code Division Multiple Access (CDMA) wireless phone system the power supply to portions of the RF transmit path are cycled on and off depending on the transmitted data rate. The present invention provides an oscillator with increased immunity to the noise induced on the power supply due to power supply cycling.

Claims

1. A Voltage Controlled Oscillator (VCO) in a wireless phone system comprising:

an amplifier; and

a resonant circuit connected to the amplifier for tuning the oscillator to a desired operating frequency, said resonant circuit comprising;

a variable circuit whose impedance is determined by a control voltage set to a first state for a first data rate for transmitted data and set to a second state for a second data rate for transmitted data in said wireless phone system; and

a low frequency attenuating filter between an input to the resonant circuit and the variable circuit.

2. The VCO of claim 1 wherein the low frequency attenuating filter is a high pass filter.

3. The VCO of claim 1 wherein the low frequency attenuating filter is a bandpass filter.

4. The VCO of claim 1 wherein the resonant circuit is implemented as a balanced circuit configuration.

5. The VCO of claim 4 wherein the resonant circuit further comprises a second low frequency attenuating filter between a second input and the variable circuit.

6. The VCO of claim 5 wherein the resonant circuit further comprises a switch and a switched element for retuning the oscillator operating frequency.

7. The VCO of claim 6 wherein the switched element is a capacitor.

8. The VCO of claim 6 wherein the switch is a diode switch.

9. The VCO of claim 8 wherein the switched element is a capacitor.

10. The VCO of claim 1 wherein the resonant circuit further comprises a switch and a switched element for retuning the oscillator operating frequency.

11. The VCO of claim 10 wherein the resonant circuit further comprises an inductor and the switched element is connected in parallel to the inductor.

12. The VCO of claim 10 wherein the resonant circuit further comprises an inductor and the switched element is connected in series with the inductor when the switch is open circuited.

13. A method for increasing the noise immunity of a Voltage Controlled Oscillator (VCO) in a wireless phone system comprising:

implementing a resonant circuit with a variable circuit whose impedance is determined by a control voltage set to a first state for a first data rate for transmitted data amd set to a second state for a second data rate for transmitted data in said wireless phone system and a low frequency attenuating filter between an input to the resonant circuit and the variable circuit; and

connecting the resonant circuit to an amplifier.

14. A multiple band resonant circuit in a wireless phone system capable of tuning across a range of resonant frequencies within each band comprising:

an inductor;

a switched capacitor connected in series with the inductor;

a variable circuit whose impedance is determined by a control voltage set to a first state for a first data rate for transmitted data and set to a second state for a second data rate for transmitted data in said wireless phone system;

a first tuning capacitor connecting a first end of the series combination of the inductor and the switched capacitor to a first end of the variable circuit;

a second tuning capacitor connecting a second end of the series combination of the inductor and switched capacitor to a second end of the variable circuit;

a first coupling capacitor connected to the junction of the first tuning capacitor and the inductor;

a second coupling capacitor connected to the junction of the second tuning capacitor and the switched capacitor; and

a switch connected in parallel to the switched capacitor to selectively provide a short circuit connection across the switched capacitor thereby electrically removing the switched capacitor from the resonant circuit.

15. A multiple band resonant circuit in a wireless phone system capable of tuning across a range of resonant frequencies within each band comprising:

an inductor;

a first coupling capacitor connected to a first end of the inductor;

a second coupling capacitor connected to a second end of the inductor;

a switched capacitor;

a switch connected in series with the switched capacitor, whereby the series combination of the switch and the switched capacitor is connected in parallel to the inductor;

a variable circuit whose impedance is determined by a control voltage set to a first state for a first data rate for transmitted data and set to a second state for a second data rate for transmitted data in said wireless phone system;

a first tuning capacitor connecting the first end of the inductor to a first end of the variable circuit; and

a second tuning capacitor connecting the second end of the inductor to a second end of the variable circuit;

wherein the switched capacitor contributes to the resonant frequency of the resonant circuit when the switch is enabled and the switched capacitor does not contribute to the resonant frequency of the resonant circuit when the switch is disabled.