Broadband frequency synthesizer
First Claim
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1. A tuner for receiving RF signals, said tuner comprising:
- an input filter receiving an RF signal having a plurality of channels and removing frequencies in said RF signal above an input cutoff frequency;
a first mixer having a first input coupled to said input filter and a second input coupled to a first reference signal, wherein said first mixer generates a first IF signal;
a first IF filter coupled to said first mixer and filtering said first IF signal;
a second mixer having a first input coupled to said first IF filter and a second input coupled to a second reference signal, wherein said second mixer generates a second IF signal;
a coherent reference phase lock loop fed by said second IF signal for generating a third reference signal; and
a frequency synthesizer comprising wide band phase locked loops (PLLs) for generating said first and second reference signals, said frequency synthesizer having a phase noise characteristic that allows said coherent reference phase lock loop to have a narrow loop bandwidth.
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Abstract
A broadband frequency synthesizer including a first local oscillator signal generated in a first phase locked loop. A second local oscillator signal is generated in a second phase locked loop. Third and fourth phase locked loops provide inputs to the second phase locked loop to control the second local oscillator frequency. The system and method provides for small step size tuning while maintaining wide phase lock loop bandwidth.
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Citations
31 Claims
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1. A tuner for receiving RF signals, said tuner comprising:
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an input filter receiving an RF signal having a plurality of channels and removing frequencies in said RF signal above an input cutoff frequency; a first mixer having a first input coupled to said input filter and a second input coupled to a first reference signal, wherein said first mixer generates a first IF signal; a first IF filter coupled to said first mixer and filtering said first IF signal; a second mixer having a first input coupled to said first IF filter and a second input coupled to a second reference signal, wherein said second mixer generates a second IF signal; a coherent reference phase lock loop fed by said second IF signal for generating a third reference signal; and a frequency synthesizer comprising wide band phase locked loops (PLLs) for generating said first and second reference signals, said frequency synthesizer having a phase noise characteristic that allows said coherent reference phase lock loop to have a narrow loop bandwidth. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 22, 23, 28, 29)
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10. The method of receiving RF signals comprising the steps of:
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removing from an RF signal all frequencies above a cutoff frequency to create a filtered input signal; creating a first reference frequency signal for mixing with said filtered input signal to establish a first IF signal; creating a second reference frequency signal for mixing with said first IF signal to create a second IF signal; and generating said first and second reference signals using a plurality of wideband PLL circuits where said first reference frequency signal achieves coarse tuning and said second reference frequency signal achieves fine tuning. - View Dependent Claims (11, 12, 13, 14, 15, 16, 24, 25, 30, 31)
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17. A circuit for use in a system for selecting frequencies within a broad band, each said selected frequency having its own bandwidth, such providing first and second reference signals, said circuit comprising:
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a plurality of wideband PLLs, wherein a first wideband PLL accepts a reference signal which is out of said band width of each selected frequency, said wideband PLLs having low phase noise and a step size resolution smaller than the loop band width of the individual wideband PLLs; and wherein said wideband PLLs operate from input reference signals, some of which are out of said bandwidth, and at least one of which is within said band width and wherein said one within said bandwidth is isolated from said output reference signals. - View Dependent Claims (18, 19, 20, 21, 26, 27)
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Specification