Understanding Spectrum Analyzers – Noise Figure

This video provides a brief technical introduction to noise figure measurements using a spectrum analyzer and the Y-factor method.

Timeline:
00:00 Introduction
00:13 About signal-to-noise ratio (SNR)
01:05 Ideal device
01:43 Real device
02:28 Defining noise figure
03:09 About noise figure (NF)
04:06 Measuring noise figure
05:15 The Y factor method
06:04 Two steps in the Y factor method
06:46 Details of the Y factor method
08:03 Additional NF measurement topics
08:29 About noise sources and ENR
09:56 About preamplifiers and NF measurements
10:54 About noise figure measurement uncertainty
11:58 About cascaded noise figure
13:28 Summary

[swadeshpoddar]

Wish everyone in RF industry had a simplified and amazing presentation skill like Paul has!!

[porkiedev]

Classic Paul with the world's best presentations!
I'm not sure how you manage to make everything so clear and easy to understand. At this point, I'm just watching presentations with your name attached because I know it'll always be something good to learn and I know that you'll explain it well.
Thank you! :)

[ernestb.]

Great series on RF theory. Very clear. Very well structured.

[NikolaiSiurdyna]

Excellent video! Very informative and easy to understand. Please do more of these.

[krishnasa]

Crystal clear explanation! Thank you very much.

[Bombayah]

Please share more :D Very clear presentation

[Remontlive-kc]

Hello, can you make a video about Additive noise measurements on FSWP?

[HamzaIshtiaq-eycg]

Key Concepts Covered:

Signal-to-Noise Ratio (SNR): SNR is defined as the ratio of the power of a signal to the adjacent noise power, typically expressed in decibels (dB). Higher SNR values indicate better signal quality relative to noise.

Ideal vs. Real Device Behavior: Ideal amplifiers theoretically amplify only the signal without adding noise. However, all real-world devices introduce some level of internal noise (denoted as
𝑁
𝑎
N
a
​
) when amplifying signals, thereby degrading SNR.

Noise Figure (NF): NF quantifies the amount of noise added by a device or component to a signal passing through it. It is crucial in RF applications, where lower NF values are preferred because they indicate less noise added.

Measuring Noise Figure: Two primary methods are discussed: using Spectrum analyzers and Vector Network analyzers. The presentation focuses on the Y-factor method with Spectrum analyzers. A noise source generates a known level of wideband noise, facilitating NF measurement.

Y-Factor Method: This method involves comparing the output noise power with the noise source off and on. The difference (Y-factor) is used to calculate NF. Calibration is essential to account for the Spectrum analyzer's own noise figure.

Additional Measurement Topics: Topics covered include the characteristics and importance of noise sources (specifically ENR - Excess Noise Ratio), the role of preamplifiers in reducing measurement uncertainty, and understanding cascaded noise figure calculations.

Measurement Uncertainty: Various factors, such as ENR values, impedance mismatches, and ambient temperature, contribute to uncertainty in NF measurements. Modern Spectrum analyzers often include uncertainty calculators to aid in accurate measurements.

Cascaded Noise Figure: The combined noise figure of multiple components in series (cascaded) is not simply additive but calculated using the Friis equation, considering gains and noise figures of each stage.

[juanpascual]

Hello. It would be very useful to have the subtitles generated automatically. It is easier to understand.
Thank you so much. Greetings.

[deepsjack]

Hello,
In the slide 8, DUT is connected to Noise source and SA source on both side. I guess it should be connected to SA Output.

[yurgen]

In slide 15 should we insert noise figure or noise factor into the equation? It looks more like noise factor

[anoorshuaib]

very nice, Please could i have this pdf copy of this presentaion

[MoTheG]

Understood, just one question: What is the point of this measurement? All I care for is the noise density of the amp and it's gain.
This number is completely dependant on frequency, bandwidth, input level, ...

[asankaliyadpita]

Can I use this method to find G/T of antenna?

[HamzaIshtiaq-eycg]

Signal-to-Noise Ratio (SNR):

SNR is the ratio of signal power to adjacent noise power, crucial in determining how well a signal can be detected and demodulated.
It's reported in logarithmic units (dB), where a higher SNR indicates better signal clarity and easier information extraction.
Ideal vs. Real Device Behavior:

Ideal Device: Amplifiers ideally increase signal power without altering SNR, but in reality, all devices add internal noise (N_a), degrading SNR.
Real Device: Real-world amplifiers introduce their own internal noise (N_a), which lowers the output SNR compared to the input SNR.
Defining Noise Figure (NF):

NF quantifies how much a device adds noise to a signal passing through it.
It's the ratio of input SNR to output SNR in linear form (noise factor, F), converted to dB (noise figure, NF).
Measurement Process:

Instruments: Spectrum analyzers are commonly used to measure noise figure.
Method: The Y-factor method is employed, involving a noise source connected to the device under test (DUT) input, and the Spectrum analyzer measures noise power at the DUT output with the source on and off.
Calibration: Calibration adjusts for analyzer noise, ensuring accurate measurement of DUT's noise figure.
Additional Topics:

Noise Sources and ENR: ENR (Excess Noise Ratio) specifies noise source performance, crucial for accurate measurements across frequencies.
Preamplifiers: Used to enhance measurement sensitivity by reducing analyzer noise contribution.
Measurement Uncertainty: Various factors affect accuracy, managed using uncertainty calculators in analyzers.
Cascaded Noise Figure: Calculated using the Friis equation, considers cumulative noise contribution of multiple components.
Summary:

NF quantifies signal degradation due to added noise.
Y-factor method with Spectrum analyzers is standard for NF measurement.
Preamp use and careful calibration minimize measurement uncertainties.
Cascaded NF calculation helps optimize signal chain design.