Generating a frequency switching local oscillator signal

• US 20090245447A1
• Filed: 03/27/2008
• Published: 10/01/2009
• Est. Priority Date: 03/27/2008
• Status: Active Grant

• Current Assignee: Novanta Inc.
• Original Assignee: TZero Technologies Incorporated (Novanta Inc.)
• Inventors: Schwartz, Adam L.
• Granted Patent: US 8,014,486 B2
• Time in Patent Office: Days
• US Class Current: 375/362
• CPC Class Codes: G06F 1/022 Waveform generators, i.e. devices for generating periodical functions of time, e.g. direct digital synthesizers G06F1/025, G06F1/03 take precedence
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

Methods and systems of generating a frequency switching local oscillator signal are disclosed. One method includes generating a reference clock signal, and clocking a counter with the reference clock signal. The counter controls selection of a one of a plurality of analog values stored in at least one of a plurality of periodic signal generators. The frequency switching local oscillator signal is generated by selecting an output of a one of the plurality of periodic signal generators.

Claims

1. A method of generating a frequency switching local oscillator signal, comprising:

generating a reference clock signal;

clocking a counter with the reference clock signal;

the counter controlling cyclical selection of a one of a plurality of analog values stored in a periodic signal generator, the cyclical selection producing a periodic signal at an output of the periodic signal generator;

controlling a frequency of the periodic signal at the output of the periodic signal generator by controlling an order of the cyclical selection of the plurality of analog values stored in the periodic signal generator;

generating the frequency switching local oscillator signal based on the periodic signal.

2. The method of claim 1, wherein controlling the order of the cyclic selection comprises directing each of a different plurality of subsets of counter bits to switch control lines of the periodic signal generator, and choosing one counter bit from each of the subsets.

3. The method of claim 2, wherein a size of each of the subsets determines a number of available frequencies of the periodic signal that can be generated by at least one periodic signal generator

4. The method of claim 1, further comprising generating the frequency switching local oscillator signal by selecting an output of one of a plurality of periodic signal generators.

5. The method of claim 4, further comprising generating the frequency switching local oscillator signal by frequency translating the reference clock signal with the periodic signal.

6. The method of claim 4, further comprising generating the frequency switching local oscillator signal by frequency dividing the reference clock signal, and frequency translating the frequency divided reference clock signal with the periodic signal.

7. The method of claim 1, further comprising the periodic signal generator storing N/2 samples of N samples of one period of the periodic signal, and generating the N samples of the periodic signal by the counter controlling selection of the stored values in an appropriate order and inverting every other repetition of the N/2 samples.

8. The method of claim 1, further comprising the periodic signal generator storing N/4 samples of N samples of one period of the periodic signal, and generating the N samples of the periodic signal by the counter controlling selection of the stored values in an appropriate order and inverting every other repetition of N/2 samples.

9. The method of claim 5, wherein frequency translation further comprises:

generating a phase-shifted reference clock from the reference clock;

generating a phase-shifted periodic signal that is phase shifted relative to the periodic signal;

frequency translating the phase-shifted reference clock with the phase-shifted periodic signal;

generating the frequency switching local oscillator signal by summing the frequency translated reference clock signal and the frequency translated phase-shifted reference clock signal.

10. The method of claim 9, wherein the phase-shifted periodic signal is generated by a second periodic signal generator which generates similar periodic signals as the periodic signal generator but shifted by a number of samples.

11. The method of claim 1, further comprising:

setting the analog values by setting a value of current for each of the plurality of analog values.

12. The method of claim 1, further comprising:

setting the analog values by setting a value of voltage for each of the plurality of analog values.

13. A method of generating a frequency switching local oscillator signal, comprising:

generating a reference clock signal;

clocking a counter with the reference clock signal;

the counter controlling cyclical selection of a one of a plurality of analog values stored in at least one of a plurality of periodic signal generators, the cyclical selection producing a periodic signal at an output of the one of the plurality of periodic signal generators;

generating a frequency switching local oscillator signal by selecting an output signal of one of the plurality of periodic signal generators.

14. The method of claim 13, further comprising generating a second frequency switching local oscillator signal by frequency dividing the reference clock signal, and frequency translating the frequency divided reference clock signal with the frequency switching local oscillator signal.

15. The method of claim 13, further comprising at least one of the plurality of periodic signal generators storing N/2 samples of N samples of one period of a periodic signal, and generating the N samples of the periodic signal by the counter controlling selection of the stored values in an appropriate order and inverting every other repetition of the N/2 samples.

16. The method of claim 13, further comprising at least one of the plurality of periodic signal generator storing N/4 samples of N samples of one period of a periodic signal, and generating the N samples of the periodic signal by the counter controlling selection of the stored values in an appropriate order and inverting every other repetition of N/2 samples.

17. The method of claim 13, further comprising:

controlling a frequency of a periodic signal of at least one of the plurality of periodic signal generators by adjusting an increment value of the counter.

18. The method of claim 13, further comprising:

controlling a frequency of the periodic signal at the output of at least one of the plurality of periodic signal generators, by controlling an order of the selection of the plurality of analog values stored in the at least one of the plurality of periodic signal generators.

19. The method of claim 18, wherein controlling the order of selection comprises directing each of a different plurality of subsets of counter bits to the switch control lines of the at least one periodic signal generator, and choosing one counter bit from each of the subsets.

20. The method of claim 19, wherein a size of the subsets determines a number of available frequencies that can be generated by the at least one periodic signal generator.

21. The method of claim 13, further comprising:

setting the analog values by setting a value of current for each of the plurality of analog values.

22. The method of claim 13, further comprising:

setting the analog values by setting a value of voltage for each of the plurality of analog values.

23. The method of claim 14, wherein frequency translation further comprises:

generating a phase-shifted reference clock from the reference clock;

generating a phase-shifted frequency switching local oscillator signal that is phase shifted relative to the frequency switching local oscillator signal;

frequency translating the phase-shifted reference clock with the phase-shifted frequency switching local oscillator signal;

generating a third frequency switching local oscillator signal by summing the frequency translated reference clock signal and the frequency translated phase-shifted reference clock.

24. The method of claim 23, wherein the phase-shifted frequency switching local oscillator signal is generated by a second plurality of periodic signal generators.

25. A frequency switching local oscillator, comprising:

a fixed-frequency reference clock for providing a reference clock signal;

a counter, the counter receiving the reference clock signal, and controlling cyclical selection of a one of a plurality of analog values stored in a periodic signal generators, the cyclical selection producing a periodic signal at an output of the periodic signal generators;

means for controlling a frequency of the periodic signal at the output of the periodic signal generator by controlling an order of the selection of the plurality of analog values stored in the periodic signal generators;

means for generating a frequency switching local oscillator signal based on the periodic signal.