How do I include Mismatch Uncertainty into the N5531S Measuring Receiver Absolute Amplitude accuracy?
The N5531S Measuring Receiver System is comprised of a PSA Series Spectrum Analyzer with Option 233 (measuring receiver personality), a P-Series or an EPM Series Power Meter, and an N5532B (or N5532A) Sensor Module.
- Convert the N5531S Absolute Amp Spec to Linear value.
- Divide by the coverage factor (K = 2.57) to get 1 sigma.
- Calculate the Source Mismatch error (1 sigma).
- RSS the Abs Amp and Mismatch terms.
- Multiply by the appropriate coverage factor (K).
- Convert the Linear result to dB.
Source Mismatch Calculation Example
Assume we are measuring a 2 GHz, 0 dBm signal. The N5531S Absolute Amplitude Accuracy is ± 0.190 dB. The Sensor Module VSWR is 1.28:1 (rho = 0.122). Assume the source VSWR is 1.5:1 (rho = .2).
- Convert Abs Amp to linear (%): 100 x [ 10^(0.190/10) -1] = 4.47%
- Normalize to 1 Sigma (K= 2.57): 4.47%/2.57 = 1.74%
- Determine Mismatch error: 100% x (0.2) x (0.122)/Sqrt(2) =1.73%
- RSS the terms: Sqrt [ (1.74)^2 + (1.73)^2 ] = 2.45%
- Multiply by the appropriate coverage factor (K): 2.57 x 2.45% = 6.30 %
- Convert % to dB: dB = 10 x Log[ 1 + (6.30/100)] = ± 0.265 dB