Amplifier (Obsolete RF System Amplifier)

Amplifier (Obsolete RF System Amplifier)

Symbol

Available in ADS

Parameters

Range of Usage

NF ≥ 0 dB
NFmin > 0
0 < | Sopt | < 1
0 < Rn
GainCompFreq > 0
For S21 = mag/ang
|S₂₁| > 0

Gain Compression Parameters

Range of Usage for Gain Compression Parameters

When specifying gain compression using model parameters, only certain combination of parameters will produce stable polynomial curve fitting. The recommended parameter combinations are listed here.

• Third-order intercept and 1dB gain compression parameters:
  TOI, GainCompPower with GainComp=1dB
  Range of validity: TOI > GainCompPower + 10.8
• Third-order intercept and power saturation parameters:
  TOI, Psat, GainCompSat
  Range of validity: TOI > Psat + 8.6
• 1dB gain compression and power saturation parameters:
  GainCompPower with GainComp=1dB, Psat, GainCompSat
  Range of validity: Psat > GainCompPower + 3
• Third-order intercept, 1dB gain compression and power saturation parameters:
  TOI, GainCompPower with GainComp=1dB, Psat, GainCompSat
  Range of validity: Psat > GainCompPower +3, TOI > GainCompPower + 10.8
• Second-order intercept and third-order intercept parameters: SOI, TOI
• AM to PM with 1dB gain compression parameters:
  AM2PM, PAM2PM, and GainCompPower with GainComp=1dB
  The value for AM2PM must satisfy this condition to avoid a square root of a negative number:
  
  
• AM to PM with third-order intercept parameters:
  AM2PM, PAM2PM, and TOI
  The value for AM2PM must satisfy this condition to avoid a square root of a negative number:
  
  If SOI is not specified, the amplifier is modeled using a polynomial of odd orders:
  y = a1 × x + a3 × x³ + a5 × x⁵ + . . . .
  As a result, only odd order harmonics (m × f, where m is an odd number) and odd order intermods (m × f1 + n × f2, where m+n is an odd number) are taken into account.
  If SOI is specified, the amplifier polynomial has an even order term:
  y = a1 × x + a2 × x² + a3 × x³ + a5 × x⁵ + . . . .
  As a result, both odd and even order harmonics and intermods are taken into account in the simulation.

Warning Messages

When values for TOI, 1 GainCompPower, and Psat are properly related, the DC input-output transfer characteristic has the form shown in DC Input-Output Transfer Characteristics.

• No Saturation. A warning is displayed if a polynomial is generated that does not have a maximum where the transfer characteristics can be clipped (when the amplifier cannot reach saturation). Refer to No Saturation Warning.

• Non-Monotonic Transfer Curve. A warning is displayed if the value specified for Psat is lower than GainCompPower. Refer to Non-Monotonic Transfer Curve Warning.

The result of this specification is that the saturated output is lower than the output at the 1 dB compression point, and the input-output characteristics have a non-monotonic characteristic transfer curve.

DC Input-Output Transfer Characteristics

No Saturation Warning

Non-Monotonic Transfer Curve Warning

Notes/Equations

1. If NFmin, Sopt, and Rn are used to characterize noise, the following relation must be satisfied for a realistic model.
   
   A warning message will be issued if Rn does not meet this criterion. If the noise parameters attempt to describe a system that requires negative noise (due to Rn being too small), the negative part of the noise will be set to zero and a warning message will be issued.
2. Use the function polar(mag,ang), or dbpolar(dB, ang), or VSWRpolar(VSWR, ang) to convert these specifications into a complex number.
3. For an S-parameter or a noise figure sinusoidal ripple, use the function ripple (mag, intercept, period, variable); for example ripple(0.1, 0, 10 MHz, freq).
   example: S21=dbpolar(10+ripple( ),0.)
4. When you define the gain using S21, keep in mind that this gain is applied to the forward incident wave into the input of the amplifier. This is in keeping with the measurement standards used to define amplifier gain at a system level. This means that if you change S11 from 0 to 0.9 for example, you will see no change in output power because the reflect wave is not taken into account by the amplifier's definition of gain, only the incident wave.
5. Z1 and Z2, the reference impedance parameters for ports 1 and 2, are used in conjunction with the parameters S11/S21/S12/S22. This is because S-data is always used with respect to a particular reference impedance.
6. This model blocks dc.
7. For circuit envelope simulation, baseband signals are blocked.
8. OmniSys used GComp1-GComp7 data items for specifying gain compression. Gain Compression Data for OmniSys and ADS summarizes the gain compression data for OmniSys and ADS. Refer to OmniSys Parameter Information for OmniSys parameter information.

GComp1-GComp6 can be specified by using the corresponding ADS gain compression parameters and setting GainCompType=LIST. Or, they can also be contained in an S2D format setting GainCompType=FILE. Also note that an S2D file could contain other data such as small signal S-parameters and noise; these data are ignored by the RF System Amplifier.

OmniSys Parameter Information

1. The AM to PM option uses parabolic amplitude dependence to describe the amplitude to phase modulation conversion. When a signal of type V_in(τ)=ACos(Wφ), is applied to the input of a device with parabolic AM to PM, the output phase exhibits:
   
   Therefore, this phase depends on the input signal amplitude A in a parabolic manner. Because the conversion of amplitude to phase is amplitude dependent, the AM to PM (AM2PM) is specified in degrees per decibel at a given output power (PAM2PM). k is calculated from these two parameters.
   
   When AM to PM is specified, the third-order intermod and gain compression are side effects. If AM2PM is specified to be very large compared to the third-order intercept or gain compression, a warning is issued.