Where To Find This Example
AWR Version 14
This example was named in V14, please see RFI_Double_Conversion_Receiver
AWR Version 13
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 you can open the project directly from this page using this button.
This example illustrates the new capabilities of Visual Systems Simulator (VSS) to analyze spur generation in systems. RF Inspector, a component of VSS is used for this analysis. This new technology for VSS is most important when dealing with complex systems making use of multiple conversions.
The system diagram "Double Down Conversion" has two mixers to down convert a 38GHz to 200MHz.
The default settings have been used for RF Inspector. To see these, click on Options, Default System Options and then click on the RF Inspector tab. The other important settings when dealing with cascaded systems is to be found within the RF Settings tab in the Default System Options dialog window. For example, here one can turn on the modelling of interstage mismatch.
In this system, filters have been used in the microwave and RF sections of the design to limit the number of unwanted signals generated by intermodulation, mixing and distortion processes. The algorithm used by RF Inspector tracks all the signals according to the user defined settings controlling level, intermodulation order etc, and the more unwanted signals the longer the algorithm takes to tacks these signals. Experiment by removing one or more filters.
Measurements and Results
There are several graphs in this project; the naming convention is as follows. Several Test Point probes have been placed within the RF, 1st and 2nd IF sections within the system. Thus, the first probe used in the second IF has the name "TPIF2_n1". To keep the spectral information from becoming too complex each Test Point probe has its own graph.
RFI measurements are found on the "RF Inspector" node under "System" measurements. In the example below we are using the TPin Test Point probe to define the primary signal of interest (in this case the RF signal) and we are examining the signals present at the first test node in the first IF.
Note that if you click/hold the mouse on the RF Inspector traces, you get a display of frequency, power, and also information on where the frequency product came from.
Further, if you double-click on the RF Inspector trace, you will get an interactive display that allows you to explore detailed information on exactly where each tone comes from.
System Diagram - Double Down Conversion
Graph - TPIF1_n3
Graph - TPIF2_n1
Graph - TPIF2_n2
Graph - TPIF1_n2
Graph - TPIF1_n1