Digital phase shifter
First Claim
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1. A digital phase shifter comprising:
- means for heterodyning an input continuous wave signal with a local oscillator frequency to output a difference frequency, the local oscillator frequency being an integer multiple of the difference frequency;
means for counting the cycles of the local oscillator frequency to produce a digital count;
means for comparing the digital count with an input digital phase shift value; and
means for combining the output of the comparing means with the local oscillator frequency to produce a phase shifted continuous wave signal corresponding to the input continuous wave signal.
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Abstract
A digital phase shifter uses a heterodyne concept to mix a continuous wave (cw) signal with a local oscillator which is an integer multiple of the difference frequency. The difference frequency is phase-locked, and the local oscillator frequency is divided into N increments by a counter. The count of the counter is compared to a microprocessor generated phase shift value which is added to the difference frequency. The phase shifted difference frequency is then converted up to produce the phase shifted continuous wave signal.
22 Citations
10 Claims
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1. A digital phase shifter comprising:
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means for heterodyning an input continuous wave signal with a local oscillator frequency to output a difference frequency, the local oscillator frequency being an integer multiple of the difference frequency; means for counting the cycles of the local oscillator frequency to produce a digital count; means for comparing the digital count with an input digital phase shift value; and means for combining the output of the comparing means with the local oscillator frequency to produce a phase shifted continuous wave signal corresponding to the input continuous wave signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A digital phase shifter comprising:
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means for heterodyning an input cw signal with a local oscillator frequency to produce a difference frequency, the difference frequency being an integer dividend of the local oscillator frequency; a phase-lock loop for controlling the local oscillator frequency; means for counting the cycles of the local oscillator frequency to produce a digital count and a second difference frequency; means for comparing the digital count with an input count, the input count being variable and representative of a desired phase shift of the input cw signal; means for dividing the local oscillator frequency by N, the dividing means being initiated each time the digital count equals the input count from the comparing means, to produce a difference frequency frequency phase shifted with respect to the second difference frequency by the amount specified by the input count; and means for converting the phase shifted difference frequency up to the input cw signal frequency to produce a phase shifted cw signal corresponding to the input cw signal. - View Dependent Claims (10)
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Specification