Voltage controlled oscillator with correction of tuning curve non-linearities
First Claim
1. A scanning-superhetrodyne ESM receiver comprising:
- a stable combline source or harmonic oscillator for providing a stable reference signal, a frequency converting device, and a voltage controlled oscillator (VCO), and a frequency measurement device, said frequency converting device converting each stable reference signal component into an intermediate frequency using the voltage controlled as a local oscillator, and said frequency measurement device functions to provide a measure of said intermediate frequency; and
wherein said stable reference signal providesa stable combline frequency source to generate a set of known voltage/frequency points, andprocessor means having a means for providing and storing values in a tempory memory is provided for employing the points as input to an interpolation program of said processor means to create the coefficients of a set of polynomial curves that together characterize the transfer curve of the voltage controlled oscillator, andwherein said processor means is used in a method used during operation for temperature compensating the transfer curve by providing a new set of polynominal coefficients periodically; and
whereinthe voltage controlled oscillator has a local oscillator frequency calculated using a known combline frequency of said combline or harmonic oscillator and a known intermediate frequency, and wherein there is provided processor means for calculating the value of the equation "local oscillator frequency value=the known combline frequency±
the known intermediate frequency", where addition of a known intermediate frequency is used if the combline frequency is below the value of the local oscillator frequency and the known intermediate frequency is subtracted if the combline frequency is above the local oscillator frequency.
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Accused Products
Abstract
A scanning-superhetrodyne ESM receiver having a VCO for a local oscillator which is linearized and temperature compensated. A stable combline oscillator is used to generate known frequency signals which are frequency converted to an intermediate frequency (IF) using the local oscillator and frequency converter(mixer). The frequency of each combline signal is measured and a table of known voltage/frequency points is generated. The table is input to a Cubic Spline program which computes the coefficients for the best-fit third order polynomial for each pair of data points. When a particular local oscillator frequency is desired, the corresponding tune voltage is computed by solving the polynomial equation for the given frequency range. By repeating the calibration on a periodic, or an "as needed" basis, temperature compensation is achieved.
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Citations
19 Claims
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1. A scanning-superhetrodyne ESM receiver comprising:
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a stable combline source or harmonic oscillator for providing a stable reference signal, a frequency converting device, and a voltage controlled oscillator (VCO), and a frequency measurement device, said frequency converting device converting each stable reference signal component into an intermediate frequency using the voltage controlled as a local oscillator, and said frequency measurement device functions to provide a measure of said intermediate frequency; and
wherein said stable reference signal providesa stable combline frequency source to generate a set of known voltage/frequency points, and processor means having a means for providing and storing values in a tempory memory is provided for employing the points as input to an interpolation program of said processor means to create the coefficients of a set of polynomial curves that together characterize the transfer curve of the voltage controlled oscillator, and wherein said processor means is used in a method used during operation for temperature compensating the transfer curve by providing a new set of polynominal coefficients periodically; and
whereinthe voltage controlled oscillator has a local oscillator frequency calculated using a known combline frequency of said combline or harmonic oscillator and a known intermediate frequency, and wherein there is provided processor means for calculating the value of the equation "local oscillator frequency value=the known combline frequency±
the known intermediate frequency", where addition of a known intermediate frequency is used if the combline frequency is below the value of the local oscillator frequency and the known intermediate frequency is subtracted if the combline frequency is above the local oscillator frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A scanning-superhetrodyne receiver comprising:
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a stable oscillator for providing a stable reference source signal, a frequency converting device, and a voltage controlled oscillator (VCO), and a frequency measurement device, said frequency converting device converting each stable oscillator reference signal component into an intermediate frequency using the voltage controlled oscillator as a local oscillator, and said frequency measurement device functioning to provide a measure of said intermediate frequency, and wherein the voltage controlled oscillator has a local oscillator frequency calculated using a known source frequency of said stable oscillator and a known intermediate frequency, and wherein there is provided processor means for calculating the value of the equation "local oscillator frequency value=the known source frequency±
the known intermediate frequency", where addition of a known intermediate frequency is used if the source frequency is below the value of the local oscillator frequency and the known intermediate frequency is subtracted if the source is above the local oscillator frequency. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification