A phase-locked loop circuit having improved phase noise characteristics includes a voltage-controlled oscillator developing an oscillating output signal responsive to a voltage control input. A reference source provides a reference frequency signal. A phase detector is operatively connected to the voltage-controlled oscillator and the reference source developing an output proportional to a phase difference between the oscillating output signal and the reference frequency signal. A loop filter connects the phase detector output to the voltage control input. The loop filter includes a switched-capacitor equivalent resistor.

Claims

19 · 2 independent · depth 4

19 granted claims

›1.independentA phase-locked loop circuit having improved phase noise characteristics comprising: a voltage-controlled oscillator developing an oscillating output s…+9

›2.↳ 1The phase-locked loop circuit of claim 1 wherein the loop filter further comprises a second capacitor connected between the switching circuit and the …d2

›3.↳ 1The phase-locked loop circuit of claim 1 wherein the loop filter further comprises an additional capacitor connected between the phase detector output…d2

›4.↳ 1The phase-locked loop circuit of claim 1 wherein the switching circuit comprises a first transistor connecting the capacitor to the phase detector out…d2+2

›7.↳ 1The phase-locked loop circuit of claim 1 wherein the phase detector comprises a phase frequency detector.d2

›8.↳ 1The phase-locked loop circuit of claim 1 wherein the phase detector includes a charge pump circuit and the loop filter converts current pulses from th…d2+1

›10.↳ 1The phase-locked loop circuit of claim 1 further comprising dividers connecting the oscillating output signal and the reference frequency signal to th…d2

›11.independentA phase-locked loop circuit having improved phase noise characteristics comprising: a voltage-controlled oscillator developing an oscillating output s…+8

›12.↳ 11The phase-locked loop circuit of claim 11 wherein the integrator further comprises a second capacitor connected between the switching circuit and the …d2

›13.↳ 11The phase-locked loop circuit of claim 11 wherein the integrator further comprises an additional capacitor connected between the phase detector output…d2

›14.↳ 11The phase-locked loop circuit of claim 11 wherein the switching circuit comprises a first transistor connecting the capacitor to the phase detector ou…d2+2

›17.↳ 11The phase-locked loop circuit of claim 11 wherein the phase frequency detector includes a charge pump circuit.d2+1

›19.↳ 11The phase-locked loop circuit of claim 11 further comprising dividers connecting the oscillating output signal and the reference frequency signal to t…d2

Classifications

2 codes

USPC · US Patent Classification

327/156327/159

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