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Design Notes

Super-Heterodyne Receiver

This satellite receiver consists of a dual down-conversion system with the RF input at 12GHz, the first IF at 3.99GHz and the second IF at 140MHz.  This project demonstrates the subsystems analysis capabilities of the AWR Design Environment by using behavioral models as part of an overall top-down design methodology. System engineers can specify performance of the functional blocks without the need for performing detailed circuit designs on the filters, amplifiers, mixers and oscillators. Circuit designers can then design the blocks and replace the behavioral models with real circuits to verify correct performance.

Overview

The project starts out as a purely behavioral systems study in the “Behavioral_Sub_System” schematic.  In addition to the behavioral models, however, this project includes a real 12GHz amplifier, “FET_Amp”, and a real distributed filter “1st_IF_Filter” at the 1st IF.  These circuits are simulated independently (see “FET Amp” and “Filter Response” graphs). These circuits make parts of the “Analytic_Sub_System” schematic, so to view the actual circuits click either "FET_Amp" or "1st_IF_Filter" subcircuit block to select it and click the "Edit Subcircuit" button (blue arrow pointing down). Simply click "Exit Subcircuit" button to go back to the main schematic. Both the behavioral and analytic systems are analyzed and the results are compared.  The most dramatic results are seen in the "Output Voltage Waveform" and "Output Spectrum Detail" graphs.  The analytic system has a significant spectral component at 310MHz, which can be clearly seen as a beat frequency in the "Output Voltage Waveforms" graph.

"Power Budget Analysis" graph shows the fundamental output power of each stage for both the behavioral and analytic systems. 

Output Equations

The budget analysis measurements were created using Output Equations.  Double-click "Output Equations" in the project browser to see the equations.  The appropriate frequency component of each selected element's output power is measured, and assigned to a variable.  These variables are then used to construct the vectors of values in appropriate order, and those vectors are plotted in the "Power Budget Analysis" graph.

Schematic - FET_Amp

Schematic - 1st_IF_Filter

Schematic - Analytic_Sub_System

Graph - Power Budget Analysis

Graph - Filter Response

Graph - Output Spectrum Detail at 2nd IF

Graph - Output Voltage Waveforms