Noise Figure Measurement System

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"With this approach, our customer can use a VSA for both NF and other RF measurements instead of buying special stand-alone hardware for concrete NF measurement. The NFMT installation package we developed includes a driver (fully integrated in user program) and a user-friendly noise figure software front panel for fast measurements."

- Davit Zargaryan, 10X Engineering

The Challenge:
Developing a noise figure measurement system to test low-noise amplifiers.

The Solution:
Using LabVIEW software and a vector signal analyzer (VSA) to develop a precise and cost-effective noise figure measurement system.

Author(s):
Davit Zargaryan - 10X Engineering
Levon Grigoryan - 10X Engineering

About 10X Engineering

10X Engineering LLC, founded in 2013, is an NI Alliance Partner with the knowledge and experience to deliver innovative engineering solutions for RF product (units, devices, components) quality and line testing, custom-designed automated test equipment (ATE) system assembly, verification, and development. Our solutions cover a variety of industrial sectors such as RF software defined radio, radiolocation, spectrum monitoring, and more. For every request we receive, we follow procedures for technical and software functional requirements clarification, RF measurement methodology selection, and hardware configurations. If needed, we take responsibility to prove a concept and demonstrate the flexibility and reliability of our solution.

Theory

The noise figure of a device is specified as a degradation of the signal-to-noise ratio (SNR), caused by variety of noises in the RF signal chain. The noise figure provides a quantifiable measure of the noise that a device under test (DUT) adds to a signal as that signal passes through it. This means that the SNR at the output is worse than the SNR at the input. We measure the noise factor to minimize the problem of noise generated in receiving systems.

Where:

F is the ratio of input SNR to output SNR at a standardized reference temperature. T = T0, designated by IEEE to be 290 °K (~17 °C). Temperature comes into the definition because the dominant contribution of noise in electronics is thermal agitation of the electrons in conductive media of the devices.

System

There are various methods to perform a noise figure measurement, including the direct method, Y-factor method, and the cold method. We used the Y-factor method to measure noise figure as described in this case study.

The Y-factor method of measuring noise figure is the method that is used behind the scenes in most noise figure meters and analyzers. It involves applying a noise source to the input of the DUT and making noise power measurements at the output of the DUT. By doing this, we can determine a ratio of noise power measurements, the Y-factor, and derive noise figure from that.

The Y-factor method uses a noise source applied to the input of the DUT. We powered it on and then off. Each time, we performed a power measurement at the output of the DUT. The Y-factor is defined as the ratio of “hot” to “cold” measured noise power (in watts).

Our main goal was to make a noise figure and measure RF and microwave devices using the Noise Figure Toolkit (NFT) by 10X Engineering, an NI VSA, and the Y-factor method.

The System Developed for Noise Figure

Our noise figure measurement system consists of four main parts:

NI PXIe-5665 high-performance vector signal analyzer up to 14 GHz, -165 dB m/Hz average noise floor at 1 GHz

PXI-4132 precision source measure unit. This part should be compatible with all NI analyzers (NI PXIe-5660/5661/5663/5665/1470) including vector signal transceivers (NI PXIe-5644R/5645R/5646R), able to work with both NI and external power supplies for noise source, and may require external LNA depending on analyzer’s sensitivity.

Noisecom NC346 ENR 15 dB

Noise Figure Measurement Toolkit (NFMT), which includes a DUT control program along with automated report generation

There are also the correlation results between the Agilent (NFA) N8975A and the NI PXIe-5665, which include tables for both the Gain and NF measurements taken during this study. For additional information please contact 10X Engineering.

Testing Parameters:

  • Measurement accuracy: ± 0.1 dB
  • Frequency range: 100 MHz–3.6 GHz
  • Average noise floor: -165 dB m/Hz
  • Absolute amplitude accuracy: ± 0.1 dB
  • VSWR2: 100 MHz to ≤ 3.6 GHz: ≤1.4:1

NFT features:

  • Noise figure and gain measurement
  • Self-calibration function
  • Compatibility with external power supplies
  • Graphical representation of measured results
  • User-friendly interface (pop-up messaging)

Conclusion

With this approach, our customer can use a VSA for both NF and other RF measurements instead of buying special stand-alone hardware for concrete NF measurement. The NFMT installation package we developed includes a driver (fully integrated in user program) and a user-friendly noise figure software front panel for fast measurements.

Author Information:
Davit Zargaryan
10X Engineering
Hovsep Emin 123
Yerevan
Armenia
Tel: (+374)77212193
zargaryandavid@yahoo.com

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