RF Attenuator Design Tool | Qucs-S S-parameter Viewer Documentation

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# RF Attenuator Design Tool

## Overview

The RF Attenuator Design Tool provides synthesis of resistive attenuators in various topologies. All designs include automatic power dissipation calculations for proper component selection.

## Attenuator Topologies

The tool supports 10 different attenuator topologies, categorized by matching characteristics and structure:

Topology | Notes
--- | ---
Pi | Matched
Tee | Matched
Bridged-Tee | Matched
Reflection attenuator | Matched
Quarter-wavelength series | Frequency-dependent. Output port unmatched
Quarter-wavelength shunt | Frequency-dependent. Output port unmatched
L-pad 1st series | Very broadband matching
L-pad 1st shunt | Very broadband matching
Series resistor | Two ports unmatched
Shunt resistor | Two ports unmatched

See individual topology documentation for detailed design equations and schematics.

## Design Flow

1. Select topology based on matching requirements and bandwidth

2. Set attenuation (dB)

3. Define impedances (Zin, Zout)

4. Enter input power for dissipation calculation

5. For quarter-wave: specify frequency and TL implementation

6. Generate schematic → Tool outputs resistor values and power dissipation

## Topology Selection Guide

Requirement | Recommended Topology
--- | ---
Broadband match, simple | Pi or Tee
Widest bandwidth | Reflection (DC to multi-GHz)
Narrowband, low insertion loss | Quarter-Wave
Impedance transformation + attenuation | L-pad
Simplest (no matching) | R-series or R-shunt

## References

[1] Vizmuller, P. (1995). RF Design Guide: Systems, Circuits, and Equations. Artech House.

[2] Doherty, W. E., & Joos, R. D. (1998). The PIN Diode Circuit Designer’s Handbook. Microsemi Corp.

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