Method and system for controlling frequency

• US 6,144,844 A
• Filed: 08/12/1997
• Issued: 11/07/2000
• Est. Priority Date: 02/14/1997
• Status: Expired due to Term

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: DSPC Technologies Limited
• Inventors: Rainish, Doron
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): BANKS HAROLD, MARSHA DENISE
• Application Number:
  US08/910,091
• Time in Patent Office: 1,183 Days
• Field of Search: 455/68, 455/70, 455/71, 455/75, 455/76, 455/77, 455/192.1, 455/192.2, 455/196.1, 455/256, 455/255, 455/257, 455/258, 455/259, 455/260, 455/264, 455/265, 455/318, 455/119 , 455/125, 455/126, 331/17, 331/18, 375/344, 375/326
• US Class Current: 455/257
• CPC Class Codes: H03J 7/02 Automatic frequency control H03J7/18 takes precedence

Abstract

A method and system for receiving a signal in a received frequency and shifting the received frequency to become a desired frequency is provided. The system includes a controllable oscillator for generating a first internal frequency, a frequency estimating unit connected to the controllable oscillator, a first frequency shift unit, connected to the controllable oscillator and to the frequency estimating unit, for shifting the received frequency according to the first internal frequency, thereby obtaining an initially shifted frequency and a second frequency shift unit connected to the first frequency shift unit and the frequency estimating unit for shifting the initially shifted frequency. The frequency estimating unit determines a total frequency shift value from the desired frequency, the received frequency and the first internal frequency and it also determines a first frequency shift value and a second frequency shift value from the total frequency shift value. Furthermore, the frequency estimating unit provides a first frequency change command to the controllable oscillator, so as to correct the first internal frequency according to the first frequency shift value, a second frequency change command to the second frequency shift unit, so as to shift the initially shifted frequency according to the second frequency shift value.

Claims

1. A system for receiving a signal in a received frequency and shifting the received frequency to become a desired frequency, the system comprising:

a. a controllable oscillator for generating a first internal frequency,

b. a frequency estimating unit connected to said controllable oscillator,

c. a first frequency shift unit, connected to said controllable oscillator and to said frequency estimating unit, for shifting said received frequency according to said first internal frequency, thereby obtaining an initially shifted frequency; and

d. a second frequency shift unit connected to said first frequency shift unit and said frequency estimating unit for shifting said initially shifted frequency,

e. said frequency estimating unit including;

f. means for determining a total frequency shift value from said desired frequency, said received frequency and said first internal frequency;

g. means for determining a first frequency shift value and a second frequency shift value from said total frequency shift value,

h. means for providing a first frequency change command to said controllable oscillator, so as to correct said first internal frequency according to said first frequency shift value, and

i. means for providing a second frequency change command to said second frequency shift unit, so as to shift said initially shifted frequency according to said second frequency shift value.

2. A system according to claim 1 wherein said frequency estimating unit provides said first frequency change command to said controllable oscillator as an electrical voltage.

3. A system according to claim 1 wherein said second frequency shift unit is a hardware unit.

4. A system according to claim 1 wherein said second frequency shift unit is a software unit.

5. A system according to claim 1 wherein said second frequency shift unit includes means for performing a frequency shift by multiplying said initially shifted frequency by e^j2π

Δ

f, wherein Δ

f is said second frequency shift value.

6. A system according to claim 1 wherein said controllable oscillator generates a second internal frequency, the system further comprising a first output frequency shift unit, connected to said controllable oscillator for shifting a transmittable signal according to said second internal frequency.

7. A system according to claim 6 further comprising a second output frequency shift unit connected before said first output frequency shift unit and to said frequency estimating unit,

wherein said frequency estimating unit provides a command to said second output frequency shift unit to shift said transmittable signal according to said second frequency shift value thereby producing an initially shifted transmittable signal, and

wherein said first output frequency shift unit shifts said initially shifted transmittable signal according to said second internal frequency.

8. In a system generating a controllable internal frequency f_IN, a method for shifting a signal from an initial frequency f_S towards a desired frequency f_D to a final frequency f_F, wherein |f_D -f_F | is less than a predetermined allowed frequency error f_ALLOWED, the method comprising the steps of:

a. determining a total frequency shift value f_TOTAL according to said internal frequency f_IN and said initial frequency value f_S ;

b. determining a first frequency shift value Δ

f₁ from said total frequency shift value f_TOTAL and said predetermined allowed frequency error f_ALLOWED ;

c. determining a second frequency shift value Δ

f₂ from said total frequency shift value f_TOTAL and said first frequency shift value Δ

f₁ ;

d. adjusting said internal frequency f_IN according to said first frequency shift value Δ

f₁ thereby shifting said initial frequency f_S so as to produce a shifted initial frequency f_SHIFTED ; and

e. shifting said shifted initial frequency f_SHIFTED according to said second frequency shift value Δ

f₂ thereby producing said final frequency f_F.

9. A method according to claim 8 wherein the sum of said first frequency shift value Δ

f₁ and said second frequency shift value Δ

f₂ equals said total frequency shift value f_TOTAL.

10. A method according to claim 8 wherein said first frequency shift value Δ

f₁ defines a frequency error f_ERROR which is less than said predetermined allowed frequency error f_ALLOWED.