The NIST 30 MHz Linear Measurement System.

Area of Science:

• Electrical Engineering
• Metrology

Background:

• Power detectors are crucial for accurate RF/microwave measurements.
• Nonlinearity in power detectors can introduce significant measurement errors.
• Existing methods for characterizing detector nonlinearity may be time-consuming or less precise.

Purpose of the Study:

• To develop and validate an automated linear measurement system (LMS) for characterizing power detector nonlinearity.
• To quantify the nonlinearity of a specific tuned 30 MHz power detector.
• To establish the uncertainty associated with the nonlinearity measurements.

Main Methods:

• Development of an automated linear measurement system (LMS) for precise electrical measurements.
• Utilizing a single thermistor bead power detector with thermal isolation.
• Characterizing detector performance over a 6.021 dB input power range.

Main Results:

• The developed LMS accurately determined the nonlinearity of the 30 MHz power detector.
• The detector exhibited nearly linear tracking over a 4:1 input power change.
• A nonlinear correction of approximately 1.00030 (130 μB) was determined.
• An expanded uncertainty of ±0.138% (598 μB) was achieved.

Conclusions:

• The automated LMS is effective for precise nonlinearity assessment of power detectors.
• The single thermistor bead design with thermal isolation provides good linearity.
• The established correction factors and uncertainty provide confidence in measurement accuracy.