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AGC_PwrControl (Power Control Block for AGC loops)

Symbol

Available in ADS

Parameters

Name

Description

Units

Default

ZRef

Reference impedance for ports 1 and 2

Ohm

50

S11

Port 1 reflection coefficient, complex number

None

polar(0,0)

S22

Port 2 reflection coefficient, complex number

None

polar(0,180)

Fnom

Nominal input frequency for detection and power control

GHz

1

TargetPwr

Target power output level

dBm

10

BW

Closed loop −3dB frequency

kHz

4.5

DampingFactor

Loop damping factor

None

0.707

NormalizedZero

Loop normalized zero

None

1

ExternalGain

Open loop gain (voltage ratio) external to this block

None

0.025

Range of Usage

ZRef > 0
| Sij | > 0 (ij=11; 22)
Fnom > 0
TargetPower > 0 (Watts)
BW > 0
DampingFactor > 0
NormalizedZero > 0
ExternalGain > 0

Notes/Equations
  1. AGC_PwrControl is used with AGC control loops; it incorporates an OpAmp loop filter with output at pin 3 for driving a preceeding AGC amplifier toward the gain required to achieve the TargetPwr level at the AGC_PwrControl input.
  2. This component uses internal components IQ_DemodTuned, FDD (used as a log amp), and OpAmp active filter, as shown in the schematic.
  3. The control voltage at pin 3 is used for feedback to an AGC amplifier (pin 3 of AGC_Amp) to achieve an RF amplitude control loop.
  4. AGC_PwrControl depends on time-varying RF waveforms, so it is typically used for Envelope simulations when an input modulated RF signal exists at Fnom.
  5. For Budget simulations, AGC_PwrControl is used with AGC_Amp to define AGC loops. Budget simulation AGC control loops work with one tone and only the steady state value of the loop is used.
    For Budget simulations, Fnom, BW, DampingFactor, NormalizedZero, and ExternalGain parameters are not used.
  6. The time-domain RF control loop dehavior is defined for second-order control loop operation in which the OpAmp loop filter internal to this model establishes the second-order control loop filter characteristics for the combined circuit external to AGC_PwrControl plus AGC_PwrControl.
  7. The control loop drives the external AGC amplifier to a gain level that is sufficient for maintaining the output power of the AGC system at the user-specified value of TargetPwr.
  8. Loop dynamics follow second-order control loop theory whereby the user defines TargetPwr, -3 dB closed loop bandwidth (BW), loop gain external to AGC_PwrControl, and second-order loop parameters (NormalizedZero and DampingFactor) and AGC_PwrControl sets the internal OpAmp reference voltage (RefVolt) and loop filter capacitance and resistance values (R1, R2, C1, C2). Refer to the schematic for the defining equations. AGC_PwrControl uses a log detector defined by use of an FDD model.
  9. For HarmonicBalance use, this model behavior defaults with output of a DC signal voltage at pin 3 equal to the reference voltage at the non-inverting input of the internal OpAmp.
  10. The output impedance at pin 3 is zero.
  11. For details regarding second-order loop theory, refer to the Second-Order Control Loop Filters section in chapter 2 of Timed Components documentation.
  12. Example designs demonstrating AGC_PwrControl in AGC control loops are located in ADS; access the designs from the ADS Main window: File > Example Project > Tutorial > RF_Budget_Examples_prj ; see Budget_AGC.dsn and AGC_loop_CE_test.dsn .
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