Method for harmonic number determination in a microwave frequency counter

• US 5,008,610 A
• Filed: 07/31/1989
• Issued: 04/16/1991
• Est. Priority Date: 07/31/1989
• Status: Expired due to Fees

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Peregrino, Luiz, Ingman, Eric M., Nelson, Nancy W., Cosart, Lee D. III
• Primary Examiner(s): Tokar, Michael J.
• Application Number:
  US07/388,208
• Time in Patent Office: 624 Days
• Field of Search: 324/77 R, 324/78 R, 324/78 D, 324/79 R, 324/79 D, 324/84, 333/218, 375/1, 375/82, 375/99, 342/352, 342/386, 455/337, 455/619, 329/315, 364/443
• US Class Current: 324/84
• CPC Class Codes: G01R 23/14 by heterodyning; by beat-frequency comparison

Abstract

Method and apparatus for determining a generalized harmonic number in a harominic heterodyne converter wherein the frequency of an input signal is determined from a local oscillator frequency, an intermediate frequency obtained by mixing the local oscillator frequency with the input signal, and a harmonic number. The likelihood of error in determining harmonic number is reduced by providing a large separation between local oscillator frequencies that are used in determining harmonic number. The method involves the steps of determining an estimated harmonic number utilizing closely-spaced local oscillator frequencies and then utilizing the estimated harmonic number to compute widely-spaced local oscillator frequencies which are utilized for determining a corrected generalized harmonic number. One variation of the technique is utilized for high harmonic numbers, and another variation of the technique is utilized for low harmonic numbers.

Claims

1. In a harmonic heterodyne converter wherein the frequency of an input signal is determined from a local oscillator frequency, an intermediate frequency obtained by mixing the local oscillator frequency with the input signal, and a harmonic number, a method for determining a generalized harmonic number H, comprising the steps of:

computing an estimated generalized harmonic number H1_est from closely-spaced first and second local oscillator frequencies f₀₁ and f₀₂ and first and second intermediate frequencies f_i1 and f_i2 obtained by successively mixing said first and second local oscillator frequencies with the input signal;

selecting a third local oscillator frequency f₀₃ such that the corresponding generalized harmonic number H3 differs from the estimated harmonic number by a predetermined integer, k;

measuring a third intermediate frequency f_i3 obtained by mixing the third local oscillator frequency with the input signal; and

computing a corrected generalized harmonic number H1_crc from the first and third local oscillator frequencies and the first and third intermediate frequencies.

2. A method as defined in claim 1 wherein the step of selecting a third local oscillator frequency includes the steps of selecting a value of k and selecting a value of s₃ where s₃ represents the sign of H3.

3. A method as defined in claim 2 wherein the step of selecting a third local oscillator frequency includes the step of computing the third oscillator frequency f₀₃ in accordance with the equation

4. A method as defined claim 3 wherein the third local oscillator frequency is selected such that k=±

1 and s₁ =s₃.

5. A method as defined in claim 3 wherein the step of computing a corrected generalized harmonic number includes the step of computing a corrected generalized harmonic number H1_crc in accordance with the equation

6. In a harmonic heterodyne converter wherein the frequency of an input signal is determined from a local oscillator frequency, an intermediate frequency obtained by mixing the local oscillator frequency with the input signal, and a harmonic number, a method for determining a generalized harmonic number, comprising the steps of:

computing an estimated harmonic number from closely-spaced first and second local oscillator frequencies and first and second intermediate frequencies obtained by successively mixing said first and second local oscillator frequencies with the input signal;

selecting third and fourth local oscillator frequencies that produce intermediate frequencies within an allowable range at the same harmonic number as the estimated harmonic number and that are widely spaced;

measuring third and fourth intermediate frequencies obtained by successively mixing the third and fourth local oscillator frequencies with the input signal; and

computing a corrected generalized harmonic number from the third and fourth local oscillator frequencies and the third and fourth intermediate frequencies.

7. A method as defined in claim 6 wherein the step of selecting third and fourth local oscillator frequencies includes the steps of

computing a local oscillator center frequency consistent with the estimated harmonic number and the intermediate frequency range, and

selecting the third and fourth local oscillator frequencies above and below the local oscillator center frequency by a predetermined frequency difference.

8. A method as defined in claim 7 wherein the step of computing a local oscillator center frequency includes the steps of

computing two local oscillator frequencies, f_oU and f_oL, in accordance with the equations

9. A method as defined in claim 8 wherein the step of selecting the third and fourth local oscillator frequencies includes the step of calculating a third local oscillator frequency f₀₃ and a fourth local oscillator f₀₄ in accordance with

10. A method as defined in claim 8 further including the step of reducing the local oscillator frequencies f_oU or f_oL to a maximum local oscillator frequency if either local oscillator frequency f_oU or f_oL is greater than the maximum local oscillator frequency.

11. A method as defined in claim 8 further including the step of increasing the local oscillator frequencies f_oU or f_oL to a minimum local oscillator frequency if either local oscillator frequency f_oU or f_oL less than the minimum local oscillator frequency.

12. In a harmonic heterodyne converter wherein the frequency of an input signal is determined from a local oscillator frequency, an intermediate frequency obtained by successively mixing the local oscillator frequency with the input signal, and a harmonic number, a method for determining a generalized harmonic number, comprising the steps of:

computing an estimated harmonic number from closely-spaced first and second local oscillator frequencies and first and second intermediate frequencies obtained by successively mixing said first and second local oscillator frequencies with the input signal;

when the estimated harmonic number is equal to or greater than a predetermined value,

selecting a third local oscillator frequency f₀₃ such that the corresponding harmonic number N3 differs from the estimated harmonic number by a predetermined integer, k;

measuring a third intermediate frequency f_i3 obtained by mixing the third local oscillator frequency with the input signal; and

computing a corrected generalized harmonic number from the first and third local oscillator frequencies and the first and third intermediate frequencies; and

when the estimated harmonic number is less than said predetermined value,

selecting fourth and fifth local oscillator frequencies that produce intermediate frequencies within an allowable range at the same harmonic number as the estimated harmonic number and that are widely spaced;

measuring fourth and fifth intermediate frequencies obtained by successively mixing the fourth and fifth local oscillator frequencies with the input signal; and

computing a corrected generalized harmonic number from the fourth and fifth local oscillator frequencies and the fourth and fifth intermediate frequencies.

13. Apparatus for determining harmonic number in a harmonic heterodyne converter wherein the frequency of an input signal is determined from a local oscillator frequency, an intermediate frequency obtained by mixing the local oscillator frequency with the input signal and a generalized harmonic number, said apparatus comprising:

means for computing an estimated generalized harmonic number H1_est from closely-spaced first and second local oscillator frequencies f₀₁ and f₀₂ and first and second intermediate frequencies f_i1 and f_i2 obtained by successively mixing said first and second local oscillator frequencies with the input signal;

means for selecting a third local oscillator frequency f₀₃ such that the corresponding harmonic number N3 differs from the estimated harmonic number by a predetermined integer k;

means for measuring a third intermediate frequency f_i3 obtained by mixing the third local oscillator frequency with the input signal; and

means for computing a corrected generalized harmonic number H1_crc from the first and third local oscillator frequencies and the first and third intermediate frequencies.

14. Apparatus for determining a harmonic number in a harmonic heterodyne converter wherein the frequency of an input signal is determined from a local oscillator frequency, an intermediate frequency obtained by mixing the local oscillator frequency with the input signal, and a generalized harmonic number, said apparatus comprising;

means for computing an estimated harmonic number from closely-spaced first and second local oscillator frequencies and first and second intermediate frequencies obtained by successively mixing said first and second local oscillator frequencies with the input signal;

means for selecting third and fourth local oscillator frequencies that produce intermediate frequencies within an allowable range at the same harmonic number as the estimated harmonic number and that are widely-spaced;

means for measuring third and fourth intermediate frequencies obtained by mixing the third and fourth local oscillator frequencies with the input signal; and

means for computing a corrected generalized harmonic number from the third and fourth local oscillator frequencies and the third and fourth intermediate frequencies.

15. In a harmonic heterodyne converter wherein the frequency of an input signal is determined from a local oscillator frequency, an intermediate frequency obtained by mixing the local oscillator frequency with the input signal, and a harmonic number, a method for determining a generalized harmonic number comprising the steps of:

computing an estimated harmonic number from closely-spaced first and second local oscillator frequencies and first and second intermediate frequencies obtained by successively mixing said first and second local oscillator frequencies with the input signal;

selecting widely-spaced local oscillator frequencies that have a known relationship to the estimated harmonic number and that correspond to intermediate frequencies within the intermediate frequency band of the converter;

measuring intermediate frequencies obtained by mixing the widely-spaced local oscillator frequencies with the input signal; and

computing a corrected generalized harmonic number from the widely-spaced local oscillator frequencies and the corresponding intermediate frequencies.