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Ideal Envelope Detector: ENVDET



ENVDET models an ideal envelope detector. The detector can be configured as a linear detector, in which the output voltage is proportional to the magnitude of the RF input voltage, or as a square-law detector, in which the output voltage is proportional to RF input power. You can also select the post-detection time constant.


Name Description Unit Type Default
ID Element ID Text E1
*MODE Operating mode (Linear or Square Law) Vector Text (drop-down) Linear
*POLARITY Polarity (Negative or Positive) Vector Text (drop-down) Positive
*SQSNS Square law sensitivity V/W (MODE=Linear only)   1000.0
*Z0 Input impedance Resistance 50.0 ohm
*TC Envelope detector video time constant Time 1e-3 Sec
*ROUT Video output resistance Resistance 1000.0 ohm
*SCALE Output level scale factor   1.0

* indicates a secondary parameter

Parameter Restrictions and Recommendations

Accuracy is best between -60 dBm and 30 dBm for Z0=50Ω. Above that level, the square-law response (MODE=Linear) may degrade slightly, and convergence may be more difficult. At low levels, it may be necessary to decrease the Absolute current-error parameter in the harmonic-balance simulator to achieve good accuracy.

Implementation Details

SCALING - When MODE=Square Law, the output-scaling parameter SCALE multiplies SQSNS. When the MODE=Linear, the default scaling gives a video output voltage equal to the input RF envelope-voltage amplitude, and SQSNS is the only means to scale the output.

CIRCUIT - The circuit shown in the symbol is somewhat stylized and does not represent the equivalent circuit of the model. The output impedance, for example, is linear, and the input impedance is only very weakly nonlinear. In contrast to the behavior of many real detectors, the video time constant is the same for positive- and negative-going pulses.


This element does not have an assigned layout cell. You can assign artwork cells to any element. See “Assigning Artwork Cells to Layout of Schematic Elements” for details.


This model was developed under research performed at Cadence Design Systems, Inc. The full set of details of the implementation are considered proprietary in nature.

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