Examples of Transient and Convolution Simulation

This section provides an example using a Gilbert cell mixer, and lists other examples shipped with ADS that demonstrate transient simulations with other types of circuits.

The following figure illustrates the setup for a basic transient/convolution simulation.

Note This design, TRAN1.dsn, is in the Examples directory under Tutorial/SimModels_prj. The results are in TRAN1.dds.

Setup for Transient/Convolution simulation

To perform a basic transient/convolution simulation:

1. From the Component Palette, choose Sources-Time Domain or Sources-Freq Domain and select appropriate sources. Place the source at the input of the component or circuit under test, then define input power and edit other parameters as required. In a circuit employing a mixer, provide a source for the local oscillator (LO).

   Note Transient sources, available in the Time Domain Sources palette, are available for these simulations, and are identified by the small "t" in their names (for example, VtStep:Voltage Source: Step). However, standard frequency sources (in the Freq Domain Source palette) can also be used.

2. Ensure that the inputs and outputs of nodes at which you want data to be reported are appropriately labeled.
3. If they are needed, select from among various transient measurement equations in the Transient Simulation palette, place these on the schematic, and edit them as required. (See Troubleshooting a Simulation.) Their results can be plotted later in a Data Display window.
4. From the Component Palette, choose Simulation-Transient. Select and place the Tran simulation component on the schematic. You can run a basic simulation by editing the parameters StopTime and MaxTimeStep on the schematic.

   Note The Max time step value should be small enough to adequately sample the highest frequency expected in the circuit. The simulator may use a smaller timestep if needed but will never use a larger value.

5. To edit the frequency of the fundamental and any other frequencies to be considered, select the Freq tab. This frequency information is required only if the frequency is not set explicitly in the frequency domain sources.
6. The parameters that make it possible to obtain the most accurate model are Max Frequency and Max impulse sample points, under the Convolution tab of the simulation component. It is recommended that you leave the other parameters under this tab at their default settings and edit them only in special cases.
7. For details regarding all Transient parameters, double-click the simulation component to edit it, select the tab of interest, and click the Help button. Many parameters in this simulator apply only to special cases.
8. Launch the simulation. The data resulting from this simulation will be identified by TRAN1. The large trace is a plot of Vif versus time, the output of the filter showing all harmonic components. The small sinusoid is a plot of Vload following the filter. The filter output has been given enough time to approach a steady-state amplitude.
   
9. A plot of fs(Vif,,,,,,,4ns,16ns) shows a time-to-frequency transform from 4 to 16 ns for the mixer output before filtering. (The seven commas represent fs parameters not used here.) Run the simulation longer to observe the noise floor drop.
   
10. Finally, an fs plot of the filter output (Vload) between 24 and 32 ns shows the response after steady-state amplitude has been approximated. Essentially only the bandpass frequency remains.
    

Additional ADS Examples

For a list of additional examples demonstrating transient simulation, see the following table. The table gives you the locations of their descriptions in the Examples documentation, and the location of the example projects available in the $HPEESOF_DIR/examples directory.

Example	Documentation Location	Example Project Location
Cosimulation of Baseband Sine Wave and Amplifier Circuit	Examples > Communication Systems > Baseband Sine Wave and Amplifier Cosimulation	/examples/Com_Sys/Co_Sim_prj/Co_sim_1.dsn
Frequency and Time Domain Simulation of Multi-Coupled Microstrip Lines	Examples > RF Board > Multi-Coupled Microstrip Lines	/examples/RF_Board/MultilayerMeas_prj/
Basic PLL Simulation using Circuit Envelope	Examples > RF Board > PLL Examples > PLL Simulations using Circuit Envelope	/examples/RF_Board/PLL_Examples/PLL_VideoExamples_prj
TDR and S-parameter Simulations of Microstrip Step Discontinuities	Examples > RF Board > Microstrip Step Discontinuities	/examples/RF_Board/TDRmeas_vs_model_prj
Various Simulations of A Power Amplifier	Examples > RFIC > Power Amplifier	/examples/RFIC/amplifier_prj
RFIC Oscillator Simulations	Examples > RFIC > RFIC Oscillator	/examples/RFIC/RFICoscillator_prj
Oscillator Simulations using Transient, Harmonic Balance and Envelope Simulators	Examples > Tutorial > Oscillator Simulations	/examples/Tutorial/Osc_Tran_HB_Env_prj