Method of calibrating PLL frequency synthesizers to precise frequencies with low tolerance crystals in their master reference oscillators

• US 7,228,118 B2
• Filed: 06/27/2002
• Issued: 06/05/2007
• Est. Priority Date: 06/27/2002
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Stevenson, Carl
• Primary Examiner(s): Urban; Edward F.
• Assistant Examiner(s): Le; Nhan T.
• Application Number:
  US10/180,027
• Publication Number:
  US 20040002316A1
• Time in Patent Office: 1,804 Days
• Field of Search: 455/255, 455/265, 455/256, 455/258, 455/259, 455/315, 455/316, 455/317, 455/318, 455/71, 455/230, 455/257, 455/313, 455/314, 331/18, 331/25, 331/55, 331/146
• US Class Current: 455/259
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence
• CPC Class Codes: H03L 1/027 by using frequency conversion means which is variable with temperature, e.g. mixer, frequency divider, pulse add/substract logic circuit H03L1/023, H03L1/026 take precedence
• CPC Class Codes: H03L 1/028 of generators comprising piezoelectric resonators H03L1/021, H03L1/022 take precedence; oscillation generators with a piezoelectric resonator H03B5/32
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop

Abstract

A frequency tracking circuit and method comprising a master crystal oscillator circuit is used for frequency tracking between a handset and a base station comprising a calibration subsystem for taking a temperature measurement, a reference control circuit for determining a numerical value needed to align a handset frequency with a base station frequency, an adder for adding the numerical value to a previous numerical value determined by the reference control circuit, a latch for latching the output of the adder, and a low precision master crystal oscillator for clocking the frequency of the latch. The most significant bit from the latch is input into a phase/frequency detector for forcing a voltage controlled oscillator to track a desired frequency.

Claims

1. A master crystal oscillator circuit for use in frequency tracking between a transmitter and a receiver comprising:

a reference control circuit pre-configured with a numerical value needed to compensate for a low precision master crystal;

an adder to add said numerical value to a previous numerical value determined by said reference control circuit;

a latch receiving an output of said adder, said latch being clocked by said low precision master crystal; and

a phase/frequency detector;

wherein said latch outputs a most significant bit of a latched data as a square wave reference frequency for comparison by said phase/frequency detector; and

said low precision master crystal is used to clock at least one of a high precision frequency in said receiver and a high precision frequency in said transmitter.

2. The master crystal oscillator circuit for use in frequency tracking between a transmitter and a receiver according to claim 1, wherein:

said numerical value is determined by a software algorithm.

3. The master crystal oscillator circuit for use in frequency tracking between a transmitter and a receiver according to claim 1, wherein:

an output from said latch is a second input to said adder.

4. The master crystal oscillator circuit for use in frequency tracking between a transmitter and a receiver according to claim 1, wherein:

said latch is 8 bits wide.

5. The master crystal oscillator circuit for use in frequency tracking between a transmitter and a receiver according to claim 1, wherein:

said latch is 16 bits wide.

6. The master crystal oscillator circuit for use in frequency tracking between a transmitter and a receiver according to claim 1, wherein:

said numerical value is adjustable to compensate for a variation in a particular master crystal oscillator.

7. The master crystal oscillator circuit for use in frequency tracking between a transmitter and a receiver according to claim 1, wherein:

said numerical value is set permanently.

8. A method of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit comprising:

pre-configuring a numerical value needed to compensate for a low precision master crystal with a reference control circuit;

adding said numerical value with a previous value determined by said reference control circuit to provide an added value; and

latching said added value, said latching outputting a most significant bit of a latched data as square wave reference frequency for comparison by a phase/frequency detector; and

clocking said latched added value with a said low precision master crystal;

wherein said low precision master crystal is used to clock at least one of a high precision frequency in said receiver and a high precision frequency in said transmitter.

9. The method of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 8, wherein:

said numerical value is determined by a software algorithm.

10. The method of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 8, wherein:

an output from said latching is a second input added by said step of adding.

11. The method of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 8, wherein:

said latching latches 8 bits.

12. The method of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 8, wherein:

said latching latches 16 bits.

13. The method of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 8, wherein:

said numerical value is adjusted during manufacture to compensate for a variation in a particular master crystal oscillator.

14. The method of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 8, wherein:

said numerical value is set permanently.

15. A means of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit comprising:

means for pre-configuring a numerical value needed to compensate for a low precision master crystal with a reference control circuit;

means for adding said numerical value with a previous value determined by said reference control circuit to provide an added value; and

means for latching said added value, said means for latching outputting only a most significant bit of latch data as square wave reference frequency for comparison by a phase/frequency detector; and

means for clocking said latched added value with a said low precision master crystal;

wherein said low precision master crystal is used to clock at least one of a high precision frequency in said receiver and a high precision frequency in said transmitter.

16. The means of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 15, wherein:

said numerical value is determined by a software algorithm.

17. The means of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 15, wherein:

an output from said means for latching is a second input added by said means for adding.

18. The means of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 15, wherein:

said means for latching latches 8 bits.

19. The means of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 15, wherein:

said means for latching latches 16 bits.

20. The means of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 15, wherein:

said means for pre-configuring determines a numerical value during manufacture to compensate for variations in a particular master crystal oscillator.

21. The means of frequency tracking between a transmitter and a receiver using a master crystal oscillator circuit according to claim 15, wherein:

said means for pre-configuring sets said numerical value permanently.