Method and circuit for deriving a second clock signal from a first clock signal

• US 7,248,658 B2
• Filed: 10/02/2001
• Issued: 07/24/2007
• Est. Priority Date: 10/02/2000
• Status: Active Grant

• Current Assignee: Lenovo Innovations Ltd Hong Kong (Lenovo Group Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Zalio, Filip
• Primary Examiner(s): Kumar; Pankaj
• Application Number:
  US09/968,524
• Publication Number:
  US 20020039396A1
• Time in Patent Office: 2,121 Days
• Field of Search: 375/355, 375/354, 375/377, 375/395.62, 375/395.61, 375/395.6, 375/395.1, 375/389, 375/351
• US Class Current: 375/355
• CPC Class Codes: G06F 1/0328 in which the phase increment is adjustable, e.g. by using an adder-accumulator

Abstract

A clock generation circuit for a dual system radio frequency station is provided. The station includes a digital synthesis circuit clocked by a first clock signal for a first RF system that is adapted to generate a base signal output of a predetermined frequency. A second clock signal is derived from the sum of the frequency of the base signal and the frequency of the first clock signal.

Claims

1. A clock generation circuit for a dual communications technology system radio frequency (RF) station, including:

a digital clock synthesis circuit clocked by a first clock signal for a first communications technology RF system and adapted to generate an analog base clock signal of a predetermined frequency; and

means for deriving a second clock signal for a second communications technology RF system from an output of said digital clock synthesis circuit as a Nyquist image derived from said first clock signal.

2. A clock generation circuit for a dual communications technology system radio frequency (RF) station, including:

a digital clock synthesis circuit clocked by a first clock signal for a first communications technology RF system and adapted to generate an analog base clock signal of a predetermined frequency; and

means for deriving a Nyquist image derived from said first clock signal, said Nyquist image having the frequency of a second clack signal for a second communications technology RF system.

3. A method for deriving a second clock signal for a second communications technology system from a first clock signal of a first communications technology system, where a frequency of said second clock signal is greater than half of a frequency of said first clock signal, including:

clocking a direct digital clock synthesis circuit with said first clock signal of a first communications technology system to generate an analog base clock signal;

applying a phase step in said synthesis circuit such that a sum of a frequency of said analog base clock signal and the frequency of said first clock signal has the frequency of said second clock signal for a second communications technology system; and

deriving said second clock signal from an output of said digital clock synthesis circuit.

4. A method for deriving a second clock signal from a first clock signal according to claim 3, wherein the frequency of said second clock signal is greater than the frequency of said first clock signal.

5. A method for deriving a second clock signal from a first clock signal according to claim 3, wherein the frequencies of said clock signals are those used by different radio frequency communications systems.

6. A method for deriving a second clock signal from a first clock signal according to claim 3, wherein said phase step is such that said base clock signal frequency represents a difference in frequency between said first clock signal and said second clock signal.