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PhaseFreqDetTuned (Phase Frequency Detector, Tuned)


Available in ADS and RFDE







Detector sensitivity (mA/degree)




Maximum unwrapped phase angle (+/− MaxAngle)




Maximum output voltage compliance (+/− Vlimit)




Nominal input frequency for VCO and REF inputs



  1. This tuned phase-frequency demodulator is used with circuit envelope simulation that models the ideal behavior of the phase frequency detectors used in phase-locked loops. (This model does not work with transient simulation.)
    On the REF and the VCO inputs, it selects the input carrier closest to the specified Fnom frequency. For proper operation, this cannot be the baseband (dc) envelope. It then generates a baseband output signal equal to the phase difference between the VCO and REF inputs, with an offset of 2 × π × Δ f  ×  time being generated if there is a frequency difference Δ f between the two inputs.
    As an example consider the sources
    V 1( t )=exp( j  ×  P 1( t )) at f 0 and
    V 2( t )=exp( j  ×  P 2( t )) also at f 0,
    as input to a PhaseFreqDetTuned component with the output terminated in a high impedance.

    NOTE Pn(t) is a function that is defined by phase or a phase descriptor.

    Envelope simulation at f 0 yields a DC output with a P 1( t ) - P 2 ( t ) time dependence. Changing the frequency of the second source from f 0 to f 0+Δ f for the same V 2( t ) is equivalent with keeping the frequency at f 0 but multiplying V 2( t ) by exp( j  × 2 × π × Δ f  ×  t) and results in the output signal P 1(t) - P 2 (t) - (2 × π × Δ f  ×  t).
    If there is no analysis harmonic frequency close enough to the Fnom frequency, then a warning is generated. The two input impedances are infinite. The output is a baseband-only infinite impedance current source with scaling defined by the Sensitivity parameter. If the output voltage exceeds Vlimit or is lower than −Vlimit, then a voltage limiter with an impedance of 10 Ohms is switched in.
    The MaxAngle parameter can be used to model special phase-frequency detectors that have greater than the traditional ±2π of input phase range.
  2. This model does not model any of the reference or VCO frequency components on the output. The output is a baseband-only signal, and the voltage limiting applies to the baseband component only. (See the baseband phase-frequency detector for a model that can overcome this limitation.) With this tuned model, though, the timesteps can actually be larger than the reference period, and it is only dependent on the PLL bandwidth and not the reference frequency; this enables faster performance for many types of simulation measurements.
    Another limitation is that only the phase of the selected input envelope is included. The effect of additional input spurs and harmonics are not included if they are in different carrier frequency envelopes.
  3. Phase-Frequency Detector Example and Simulation Results show a simple schematic and example of this phase-frequency detector's output. The reference input is a fixed frequency. The VCO input has sinusoidal frequency modulation.

Phase-Frequency Detector Example

Simulation Results
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