Measurement chain
Track signal power, connection limits, and cascaded noise through cables, pads, couplers, and amplifiers.
Matched ports at one operating frequency. Gains and losses are small-signal values. Power is one CW tone; output limits apply to that estimated signal power. Compression, reflections, and peak-envelope limits require separate checks.
Blank gain or loss means 0 dB (unity). Noise figure and temperatures are required; a blank limit means no limit. Order stages from the source to the receiver. Use a passive stage for cable loss, a pad, or a coupler branch. Name its output connection (for example, “DUT input”). Limits are optional, in dBm at that output.
| Connection | Gain / loss | Signal | Output limit | Headroom |
|---|
Noise figure is referenced to 290 K. Passive-stage noise uses its physical temperature; amplifier noise figure is an input specification. Output noise uses the source temperature and equivalent noise bandwidth entered above.
| Stage output | Stage NF | Cumulative NF | Output noise |
|---|
Friis cascade: F = 1 + Σ (Fᵢ − 1)/Gbeforeᵢ, using linear power gain and noise factor. A passive loss L at temperature T has F = 1 + (L − 1)T/290 K. Noise output = kB[Tsource + 290 K(F − 1)]Gtotal.
Assumes matched stages, independent noise, and gain/noise figure constant over the chosen bandwidth. Coupler loss refers to the selected branch with other ports terminated. A filter's nominal bandwidth may differ from its equivalent noise bandwidth.
Static calculations in your browser. No measurement data is uploaded.