VGA

Model variable gain amplifier

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Libraries:
RF Blockset / Circuit Envelope / Elements

Description

The VGA block models a RF Blockset™ variable gain amplifier (VGA). The Simulink^® signal controls the non-linear gain.

The three Simulink input ports are Gain, IP2 (second-order intercept point), and IP3 (third-order intercept point). The port, In is the RF Blockset voltage input and the port OUT is RF Blockset voltage output.

Ports

Input

Gain — Power gain signal

scalar

Power gain signal, specified as a scalar in dB. The power gain signal is a Simulink signal.

Data Types: double

IP2 — Second-order intercept point signal

scalar

Second-order intercept point signal, specified as a scalar in dBm. The second-order intercept point signal is a Simulink signal.

Data Types: double

IP3 — Third-order intercept point signal

scalar

Third-order intercept point signal, specified as a scalar in dBm. The third-order intercept point signal is a Simulink signal.

Data Types: double

Parameters

Input impedance (Ohm) — Input impedance of VGA

50 (default) | scalar

Input impedance of the VGA, specified as a scalar in ohms.

Output impedance (Ohm) — Output impedance of VGA

50 (default) | positive scalar

Output impedance of the VGA, specified as a scalar in ohms.

Intercept points convention — Input-referred or output-referred convention

Output (default) | Input

Input-referred or output-referred convention for IP2 or IP3 intercept points, specified as Input or Output.

Ground and hide negative terminals — Ground and hide negative terminals

on (default) | off

Ground and hide negative terminals, specified as on or off. Select this parameter to internally ground and hide the negative terminals. Clear the option to expose the negative terminals. By exposing these terminals, you can connect them to other parts of your model.

More About

Coefficient Formulae

The VGA output voltage is a function of the input voltage:

$$V_{out}=g*V_{in}+c_2*V_{in}{}^2+c_3*V_{in}{}^3$$

The table shows the formulas for the coefficients, g, c₂, and c₃

	Input Referred	Output Referred
g	$$g=\frac{2\sqrt{G*Z_{out}*Z_{in}}}{\left|Z_{in}\right|}$$
c2	$$C_2=\frac{g}{\sqrt{2*IP2*Z_{in}}}volt{s}^{-1}$$	$$C_2=\frac{g^2}{\sqrt{8*IP2*Z_{out}}}volt{s}^{-1}$$
c3	$$C_3=\frac{4}{3}.\frac{g}{2*IP3*Z_{in}}volt{s}^{-2}$$	$$C_2=\frac{4}{3}.\frac{g^3}{8*IP3*Z_{out}}volt{s}^{-2}$$

Version History

Introduced in R2015b