Performing Budget Simulations

This section describes the following example designs included with ADS and how to use the Budget controller with them to perform budget simulations:

• A Simple Budget Design performs a basic budget simulation of a two-port, two-pin cascaded network.
• Using Mixers and Multiple Paths performs a budget simulation of a two-port, two-pin cascaded network containing a mixer component.
• Using Two-Port, Two-Pin S-Parameter Files describes the special conditions about using the S2P component in a cascaded two-port, two-pin design.
• Using AGC Control Loops performs a basic budget simulation of a two-port, two-pin cascaded network containing an AGC loop.
• Using Budget with Sweep performs a budget simulation of a two-port, two-pin cascaded network containing a Parameter Sweep controller.
• Using Budget with Optimization and Yield performs a budget simulation of a two-port, two-pin cascaded network containing an Optimization controller.

For detailed descriptions of the Budget controller parameters, see Parameters for RF System Budget Analysis. For information on the use of the Data Display in the context of budget simulations, see Working with RF System Budget Analysis Results.

A Simple Budget Design

The following figure illustrates an example setup for performing a basic budget simulation of a two-port, two-pin cascaded network.

Note This design, Budget_Baseline.dsn, is in the examples directory under Tutorial/RF_Budget_Examples_prj. The results are in Budget_Baseline.dds.

Basic Budget simulation of a two-port, two-pin cascaded network

This design shows a typical RF system design used with budget analysis. It uses a P_1Tone as the source, Term to terminate the cascaded network, and contains a filter, a nonlinear amplifier, a mixer, a second filter, and a second nonlinear amplifier connected in a chain. The measurements selected in this design are typical ones including measurements for component performance, noise, power, and intercept points.

Using Mixers and Multiple Paths

The following figure illustrates an example setup for performing a budget simulation of a two-port, two-pin network with multiple paths to mixer components.

Note This design, Budget_Mixer.dsn, is in the examples directory under Tutorial/RF_Budget_Examples_prj. The results are in Budget_Mixer.dds.

Budget simulation of a network with two paths to mixers

This design shows the performance of a mixer ( MixerWithLO ) with and without an input image rejection filter. It also demonstrates use of the PathSelect2 switch which is useful in budget analysis to set up alternate paths for budget analysis. By using two paths, noise figure analysis can be performed both with and without rejection filters for each mixer. For details about MixerWithLO and PathSelect2, see the System Models documentation.

• The MixerWithLO is the only mixer component supported in an RF budget simulation. MixerWithLO is available from the Simulation-Budget and System-Amps & Mixers palettes, and the Component Library. It is based on the Mixer2 component and has a built-in LO.
• PathSelect2 is available from the Simulation-Budget and System-Switch & Algorithmic palettes, and the Component Library. It is based on two SPDT switches, and enables you to select from multiple paths in a simulation.

To measure the output of the mixer M1 with the image filter BPF1 at its input, set PathSelect2 parameter State=0. The system noise figure is 4.77 dB and includes noise from the mixer at the image frequency reflected by the input filter back to the mixer.

To measure the output of the mixer M2 without the image filter at its input, set PathSelect2 parameter State=1. The system noise figure is 6 dB and includes noise from the source at the image frequency. The TwoPort component is used in this path so the same number of components exist in each path. The number of component must be equal so the results have an equal number of rows and columns regardless of the PathSelect2 settings.

Using Two-Port, Two-Pin S-Parameter Files

If you use a two-port, two-pin S-parameter file as a component in a budget simulation, the S2P component may be used in the cascaded two-port, two-pin design, but its pin 3 must be connected to ground as shown here.

Using AGC Control Loops

The following figure illustrates an example setup for performing a basic budget simulation of a two-port, two-pin cascaded network that contains an AGC loop.

Note This design, Budget_AGC_Pilot.dsn, is in the examples directory under Tutorial/RF_Budget_Examples_prj. The results are in Budget_AGC_Pilot.dds.

Typical RF system design containing an AGC loop

This design shows a typical RF system design containing an AGC loop used with budget analysis. The AGC loop is controlled by the AGC_Amp and AGC_PwrControl components. For details about these two components, see the System Models documentation.

• AGC_Amp and AGC_PwrControl are the only components supported in an RF budget simulation for defining AGC loops. They are available from the Simulation-Budget and System-Amps & Mixers palettes, and the Component Library.

This example uses a Signal tone and an AGC Pilot tone. The AGC Pilot tone controls the AGC loop. The Signal tone is defined in the P_nTone source by Freq[1]=RFfreq and P[1]=dbmtow(Power_RF). The Pilot tone is defined in the P_nTone source as Freq[2]=RFpilot and P[2]=dbmtow(Power_Pilot). Using Freq[2] to set the Pilot tone identifies which signal the feedback loop should use; this is a defined operation of the P_nTone source. The AGC_PwrControl component's TargetPwr parameter is set to 10 dBm. Feedback to the AGC_Amp drives the AGC_Amp within its limits of Min_dB and Max_dB to achieve the TargetPwr level. In this example, the AGC_Amp stabilizes to the required Pilot tone gain of 10 dB to achieve the TargetPwr level of 10 dBm for the Pilot tone. This also results in an output power for the Signal tone at 0 dBm.

Using Budget with Sweep

The following figure illustrates an example setup for performing a budget simulation of a two-port, two-pin cascaded network that includes a Parameter Sweep controller.

Note This design, Budget_PSweep.dsn, is in the examples directory under Tutorial / RF_Budget_Examples_prj. The results are in Budget_PSweep.dds.

This example demonstrates an RF system budget analysis where the Parameter Sweep controller sweeps the source power ( Power_RF ). Other component parameters can be swept as allowed by ADS. Typical budget measurements are used for component performance, noise, power, and intercept points.

Performing a Budget simulation of a two-port, two-pin cascaded network including a Parameter Sweep controller

Using Budget with Optimization and Yield

The following figure illustrates an example setup for performing a budget simulation of a two-port, two-pin cascaded network that includes an Optim controller.

Note This design, Budget_Power_Optimization.dsn, is in the examples directory under Tutorial/RF_Budget_Examples_prj. The results are in Budget_Power_Optimization.dds.

This design demonstrates an RF system budget analysis with power optimization. Typical budget measurements are used for component performance, noise, power, and intercept points.

The optimization type is set to Random because budget analysis cannot be used with Gradient-like optimization types such as Gradient, Gradient Minmax, Quasi Newton, Least Path, Minmax, Hybrid, and Sensitivity.

Performing a Budget simulation of a two-port, two-pin cascaded network including an Optimization controller

You must use MeasEqn to identify the goal for specific budget results.

• You can define their measurements in the Schematic using MeasEqn.
• Budget data is used in MeasEqn using indexed numbering, where indexing starts at zero for the first component after the source. For example, OutPwr_dBm[4] refers to the output power for the fifth component after the source.
• SysPwrOut can be used for optimization, yield, etc. as shown in the example in the previous figure.

For a complete listing of names for all available Budget measurements, see the tables in RF Budget Cascade Measurements and RF Budget Summary Measurements. These tables show the short names for the Budget measurements. The long name for a Budget measurement is defined as:

<schematic_design_name>.Budget.<measurement_name>

When setting up system summary measurements to use for optimization:

• The independent variable is Index.
• The name to be used in the MeasEqn is System_Value[x], where x is the Index for the Summary Measurement desired.
• For example, the SystemNF_dB system summary measurement has Index=5, so the MeasEqn should use System_Value[5].

When setting up system cascade measurements to use for optimization:

• On the Setup tab, when Components In is set to Columns:
  • The independent variable is Cmp_Index.
  • The name to be used in the MeasEqn is the actual cascade measurement name associated with the specific component.
  • For example, the OutPwr_dBm system cascade measurement for the fourth component should use OutPwr_dBm[3].
• On the Setup tab, when Components In is set to Rows:
  • The independent variable is Meas_Index.
  • The name to be used in the MeasEqn is the system reference designator associated with the specific cascade measurement.
  • For example, the fourth measurement for the component with reference designator A1 should use A1[3]. If you had defined the fourth measurement to be OutPwr_dBm, then A1[3] means the OutPwr_dBm is associated with the component whose reference designator is A1.