PhaseNoiseMod (Phase Noise Modulator)
Symbol
Available in ADS and RFDE
Parameters
Name |
Description |
Units |
Default |
---|---|---|---|
Fnom |
Nominal input frequency |
GHz |
1 |
Rout |
Output resistance |
Ohm |
50 |
Fcorner |
Corner frequency for 1/f noise performance |
MHz |
1 |
NF |
Broadband noise figure |
dB |
3 |
QL |
Loaded Q of resonator |
None |
500 |
Notes/Equations
- This device uses Leeson's equation to model oscillator phase noise, then modulates the input carrier with this phase noise.
The input can be from any signal source, including the VCO models. This model behaves as a tuned modulator by selecting and modulating just the carrier defined by the Fnom parameter. If there are no analysis frequencies close enough to this value, a warning is generated and no signal is output. The Leeson's equation models the oscillator phase using the equation
where
Fnom is used as an approximation to carrier frequency
F is the noise factor
is the input signal power
T is the absolute temperature
B is the analysis bandwidth
k is the Boltzmann constant
Q_{L} is the loaded Q value of the oscillator's resonator
Fcorner is the frequency at which the low frequency 1/f noise is equal to the broadband noise.
This model is usable in frequency domain and circuit envelope time domain noise analyses. To avoid the divide-by-zero problems as the analysis offset frequency approaches 0, both the 1/f^{2} and 1/f terms are rolled off at frequencies below 1 Hz. In the time-domain mode, the 1/f frequency response is implemented by doing a convolution simulation. The duration of this impulse response is set to 2000 timesteps. This effectively rolls off this 1/f response at a frequency determined by the analysis tstep parameter. - This circuit phase modulates one large signal frequency with noise to produce pure phase noise without amplitude noise. Because of the nature of harmonic balance, the noise exists at sidebands above and below this one large signal tone, but around no other large signal frequencies. Thus, if phase noise is specified at an offset frequency large enough that it could appear around another large signal frequency, the noise will not appear if viewed around that other large signal frequency. This can be a limitation when attempting to combine two sources that are close together in frequency. In that case, the P_1Tone with phase noise should be used instead for harmonic balance analysis.