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SNS Series Noise Sources

Technical Overviews

 Noise Sources Designed to Meet Specific Needs

The Keysight Technologies, Inc. SNS Series of noise sources work in conjunction with:

• NFA Series noise figure analyzers

• X-Series signal analyzers

To simplify measurement set-up and improve accuracy these noise sources automatically download electronically stored calibration data to the compatible Keysight noise figure measuring analyzers. The noise sources also have the capability to automatically measure their own temperature so that compensation can be applied to the calibration data. These capabilities increase the overall reliability and accuracy of noise figure measurements.

SNS Series key features and benefits

• Automatic download of ENR data to the analyzer speeds overall setup time

• Electronic storage of Excess Noise Ratio (ENR) calibration data decreases the opportunity for user error.

• Temperature sensing improves measurement accuracy, leading to tighter specification of device performance.

The N4000A and N4001A, which cover the 10 MHz to 18 GHz frequency range, come with an APC 3.5 (m) connector as standard, and offer the option of a Type-N (m) connector.

The N4002A, which covers the frequency range 10 MHz to 26.5 GHz, has an APC 3.5 (m) connector as standard-copy.

N4000A for Low Noise Figure or Mismatch Sensitive Devices Up to 18 GHz

The N4000A is designed to accurately measure devices with low noise figure, or devices whose gain is especially sensitive to small changes in source impedance. This includes most GaAs FET’s. The N4000A maintains the same impedance whether turned on or off. By maintaining the same impedance at the input to the device under test (DUT) gain changes are reduced. These gain changes can often masquerade as DUT noise and cause noise figure measurement errors.

The ENR of this noise source is nominally 6 dB from 10 MHz to 18 GHz. DUTs with noise figures up to 20 dB can be accurately and reliably measured with this device. The N4000A noise source has a choice of connectors, with an APC 3.5 (m) as standard.

N4001A for General Purpose Measurements from 10 MHz to 18 GHz

The N4001A noise source is ideal for general purpose use with a low reflection coefficient and a nominal ENR of 15 dB from 10 MHz to 18 GHz. DUT’s with noise figures up to 30 dB can be measured accurately and reliably with this device. The N4001A has a selection of connectors, with an APC 3.5 (m) as standard.

N4002A for Measurements Up to 26.5 GHz

The N4002A noise source was designed to measure DUT noise figures reliably and accurately up to 30 dB from 10 MHz up to 26.5 GHz accurately and reliably. This noise source comes with an APC 3.5 connector as standard.

Accurate Noise Power

The output of a noise source, usually given in terms of Excess Noise Ratio (ENR), must be known in order to make accurate noise figure measurements. Any uncertainty in the ENR transfers into uncertainty of the measured noise figure, dB for dB. Keysight provides accurate ENR calibration data with each noise source. ENR uncertainty and reflection coefficients at each frequency point are provided as well.

The Importance of Noise Source Reflection Coefficient

Two aspects of noise source reflection coefficient are important to note:

• A non-zero reflection coefficient contributes to re-reflections between the DUT and the source. The reflections cause uncertainty in the noise power emerging from the source. The measured noise figure, furthermore, refers to the actual noise source impedance rather than the desired 50 Ω value. The low reflection coefficient of Keysight SNS Series noise sources can keep this uncertainty under 0.1 dB.

• The change in reflection coefficient between On and Off can cause DUT Gain variations which, in turn, can cause noise figure measurement errors. This problem is effectively eliminated by the N4000A, whose complex reflection coefficient change is specified to be less than 0.01. 


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