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High Power BJT Amplifier
This example demonstrates a single tone harmonic balance simulation on a BJT amplifier using the Freescale MRA0500-19L device. Standard power amplifier measurements performed include swept power, power added efficiency (PAE), DC/RF efficiency, output power spectrum, IP3, IP5, Intermodulation products. Several measurements are configured to plot at a constant output power. The DC-IV curves are also plotted with the dynamic load line which can be tuned over power. DC annotations are also added to calculate and display the voltages at each node in the amplifier circuit. Use the tuning bar the drive power and bias voltages to see the effect on the dynamic load-line, the power spectrum plots and the gain and efficiency vs. output power plots.
Important features of this project are the integral display of the load line on the IV curve plot, the use of dc annotations to detect the voltage and current to construct the load line, the use of the XSwp block to look at gain and power added efficiency vs. output power, and the CONSPOUT block to plot measurements versus a constant output power. Notice the nice use of the User Folders at the bottom of the Project Browser to see how the different test benches and measurements are logically organized.
• DC IV / Dynamic Load Line: The load line is constructed using the current and voltage calculated from the annotated voltage (Vc) and current (Ic) at the collector of the transistor in the amplifier circuit, while the IV characteristic is measured using the IV meter.
• Annotated Voltage and Current: The annotations are added to the circuit schematics by right clicking on the schematic name and choosing Add Annotation. For this project annotations were added for the “High_Power_BJT_Amp” circuit. The DCVA_N annotation measurement is used to measure the dc voltages at all nodes. The DCIA annotation measurement is used to measure the dc input current for all the elements.
• Gain and Efficiency vs. Output Power: The PGain and PAE measurements are plotted vs. output power (Pcomp) using the PlotVs measurement. The graph shows gain and efficiency at all bias points (base and collector voltages are swept), as well as an overlay trace that can be changed by using the tuner to select individual bias points.
Gain and Efficiency at a Fixed Output Power: The Pcomp (input and output) and PAE measurements are plotted a constant 38 dBm output power. This is achieved with the CONSTPOUT block on a schematic and is only available with the Aplac HB simulator.
• Gain and Efficiency at the 1 dB Compression Point: The Pcomp (input and output) and PAE measurements are plotted a constant 38 dBm output power. This is achieved with the XDB block on a schematic and is only available with the Aplac HB simulator.
• Output Intercept Points and Carrier to Intermodulation Products: Several measurements are setup to show how these values can be plotted without the use of equations.
The dc annotation is added in a manner similar to the process of adding a measurement to a graph.
Double click on the annotation name (at left in project tree) and observe the properties of the DCVA_N annotation measurement. Also note that after simulation the DC voltages are displayed at each node in the circuit “High_Power_BJT_Amp”.
Dynamic Load Line setup with tuner control
The dynamic load line is set up to be tunable by choosing Select with tuner from the drop-down menu for PORT_1. Double click the IVDLL measurement under the “Dynamic Load Line” graph to view the setting for PORT_1. The current and voltage input for the IVDLL measurement are chosen by selecting Ic and Vc (@Port 2) for the BJT in the circuit.
DC/RF Efficiency (DC/RF), PAE and Total Power (PT) Measurements
These measurements can be found in the 'Nonlinear' measurement type under 'Power' subgroup. (see Power and Efficiency plot)
The voltage waveform measurement uses the Vtime measurement found in the 'Nonlinear' measurement type under 'Voltage' subgroup. (see Power and Efficiency plot)
Power Spectrum setup and resulting plot
The power spectrum is plotted using the Pharm measurement found in the 'Nonlinear' measurement type under 'Power' subgroup. "Select with tuner" is chosen from the drop-down menu for Port_1 for tuner control (same as the load-line setup above).
PAE and Gain vs. Output Power
The Output Power is defined in the XSwp block in corresponding schematic referenced in the measurement dialog.