### Where To Find This Example

Select **Help > Open Examples...** from the menus and type either the example name listed above or one of the keywords below.

Or in Version 13 or higher you can open the project directly from this page using this button. Make sure to select the **Enable Guided Help** before clicking this button.

### Design Notes

**Circuit Envelope Simulation of a High Power BJT Amp**

This example demonstrates a circuit envelope simulation of a multi-carrier QPSK modulated signal using a Freescale MRA0500-19L device. As is important with any circuit envelope simulation this device was simulated in the time domain and the performance was verified against the frequency domain performance. The verification was done in the example **Circuit_Envelope_Cosimulation_with_VSS** so we did not include it here as well.

**Overview**

The multi-carrier QPSK signal was generated from the system diagram **QPSK_Generator**. This system diagram does require a VSS license, but simulating circuit envelope in APLAC with the generated I/Q data does not require a VSS license, only the appropriate APLAC license. If any errors appear regarding VSS licensing, simply disable the **PWR_SPEC** measurement in the **QPSK Spectrum Verification** graph. It is only needed to verify the input to the APLAC circuit envelope simulator is correct.

**Schematics/System Diagrams**

**QPSK_Generator** - System diagram that generates the multi-carrier QPSK signal. The** FILE_SNK** element captures the I/Q data and writes it to the datafile **Multi_Carrier_QPSK**.

**Envelope_TB** - Uses the **PORTIQ_ENV** port to source the amplifier with the multi-carrier QPSK signal. The **PORTIQ_ENV** source uses the datafile **Multi_Carrier_QPSK** that was generated in the **QPSK_Generator** system diagram. The **Pwr** parameter is left blank so the total power in the source is the same as when the I/Q data was captured.

**HB_TB** - A swept input power and frequency harmonic balance simulation of the amplifier to show the BJTs continuous wave performance.

**High_Power_BJT_Amp** - The amplifier we are simulating including the bias network as well as the input and output matching networks.

**Data Files**

**Multi_Carrier_QPSK **- I/Q file containing the QPSK waveform.

**Graphs**

**CW Gain** - The sine wave gain of the BJT amplifier across frequency.

**CW Power and Efficiency** - The sine wave output power, and power added efficiency of the BJT amplifier.

**QPSK Fundamental Carrier Voltage** - The time domain voltage of the Fundamental carrier at the input and output.

**QPSK Gain and Average PAE** - The total power gain and power added efficiency of the amplifier when driven by the multi-carrier QPSK signal. The method of computing the gain is comparing the integral of the power spectrums at the input and output. The method of computing the power added efficiency looks at the instantaneous input, output, and DC powers.

**QPSK PAE vs Time** - The instantaneous power added efficiency of the amplifier over the full duration of the modulated signal.

**QPSK Spectrum **- The envelope input and output spectrum of the Fundamental carrier and the original VSS waveform spectrum.

**QPSK Voltage Waveform** - The envelope voltage over time of the QPSK signal at the input and output of the amplifier.