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IQ_Demod_Data (IQ Demodulator Behavioral Model)

Symbol

Available in ADS

Parameters

Name

Description

Units

Default

Dataset

Name of dataset generated by IQ_Demod_Setup

None

dataset.ds

Freq

Carrier Frequency

GHz

1.0

Notes/Equations
  1. IQ_Demod_Data is a data-based system model of a circuit-level I/Q demodulator. The circuit-level demodulator is characterized by a dataset generated by the system component IQ_Demod_Setup. The use of this component is highlighted in the example project IQ_Demod_prj.
  2. The demodulation behaviors are extracted for a single carrier frequency. Only the demodulation distortions are characterized, so it is possible to set the frequency parameter in IQ_Demod_Data to differ from the value set in IQ_Demod_Setup. The demodulation will occur at the frequency set in IQ_Demod_Data. The extracted distortions to the baseband signal as it passes through IQ_Demod_Data will be applied at this frequency. IQ_Demod_Data does not model any dispersion in these distortions across the baseband bandwidth.
  3. IQ_Demod_Data is designed for Circuit Envelope system verification where various filters typically eliminate unwanted frequency components. Therefore, IQ_Demod_Data makes no attempt to model harmonic components. The signals generated on the I and Q output ports are purely baseband signals. IQ_Demod_Data does not generate any frequency components at any carrier frequency.
  4. In order for IQ_Demod_Data to produce an accurate model of the circuit-level demodulator characterized via IQ_Demod_Setup, the IQ_Demod_Setup Order parameter must be large enough to prevent aliasing of higher-order frequency components. For mildly non-linear circuits, an Order of about 5 should suffice, while an Order in the range of 10-15 is recommended for highly non-linear circuits. Providing this criterion is met, the Order parameter for the simulation controller can be very low when using IQ_Demod_Data in a Circuit Envelope simulation. Typically, an Order of around 3 should suffice for accurate demodulation modeling. Note, however, that accurate modeling of other components of the complete system may necessitate a larger value for this parameter.
  5. For a circuit-level demodulator, the impedances presented by the input and output pins will generally be a complicated function of all state variables within the demodulator. For the IQ_Demod_Data, a certain simplification is necessary as no information about the environment in which the demodulator will later reside is known at the time of extraction. The input impedance at the RF input pin is extracted at the RF carrier frequency specified in IQ_Demod_Setup, and is a function of the input power. The impedances at the I and Q output pins are extracted at DC, and are modeled as constant impedances.
  6. The extrapolation properties of IQ_Demod_Data above Pin-Stop are very poor. When using IQ_Demod_Data, ensure that the RF input signal does not exceed the Pin_Stop value set in IQ_Demod_Setup when the model was extracted. Extrapolation to signal levels below the Pin_Start value set in IQ_Demod_Setup will generally be good as long as the Pin_Start value lies within the linear operating range of the demodulator.
  7. IQ_Demod_Data does not model noise.
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