What is Noise Figure & How to Measure It - What the RF (S01E05)
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- čas přidán 2. 08. 2024
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Transcript:
When working on your product’s design you’ll often want to optimize the sensitivity of your receiver. That’s where being able to characterize and improve your system’s noise figure becomes one of the important factors to consider.
What’s up everyone!! The name is Nick Ben and I’m an engineer here at Keysight… and welcome to the 5th episode of ‘What the RF!’
In today’s episode we’ll be discussing noise figure, including what it is and how to measure it.
Noise figure is one of the most important design considerations in the sense that it is a very efficient way to evaluate the performance of your device.. You can make noise figure measurements on complete systems or components. These include almost all multi-port devices from passive devices to active devices. Let's learn more about it.
Noise figure is the degradation of the SNR as a signal passes through a system or device. Noise figure tells us the relative amount of noise being added to the signal.
In our case, the device is this low noise amplifier.
To calculate noise figure we determine the ratio of the respective signal-to-noise power ratios at the input and output of the device. Device must be at a reference room temperature of 290 degrees kelvin.
Noise contribution in electronics is also caused by thermal agitation of electrons - or thermal noise. 290 kelvin was adopted by institutions as the standard temperature for determining noise figure.
The noise figure value is a number expressed in dB and indicates the performance of a device’s internal components like this amplifier.
A low noise figure is good and high noise figure is bad.
We see an example of a signal at an amplifier’s input in (a) and at its output in (b).
As you can see on the right, the noise level rises more than signal level due to the noise added by the amplifier’s circuits. This is the amplifier’s noise figure value.
By knowing your device’s noise figure value you can calculate a system’s sensitivity from its bandwidth. Noise figure is a key parameter when handling small signals, and quantifies the network’s added noise.
All you need to characterize your device’s noise figure is a signal analyzer, a noise source to calibrate with, and your device.
For a noise figure measurement there are only 2 main steps you’ll need to follow -
1. Calibrate your test system; and
2. Measure your DUT’s noise figure
Yes, it’s really that simple.
As mentioned earlier in the video, the DUT we’ll be testing is this low noise amplifier, but we’ll first need to calibrate our signal analyzer.
In this first step, we’re calibrating our signal analyzer. All we’ll need is a noise source and a signal analyzer.
Switching over to the noise figure application on our signal analyzer, we see that our signal analyzer is uncalibrated, and we know this by the cal-state indicated at the top right hand corner.
So let’s go ahead and calibrate this. Going into the measurement setup menu, we press the DUT setup & the calibration button.
Today, we're just going to set up one DUT - this amplifier - which has a frequency range from 10 MHz to 1 GHz. But, I'm going to set the maximum frequency range parameters for the test to 3 GHz. By doing this, we'll be able to see the amplifier's performance roll off as we scan past its operating range. You can see where you would need to spec the amplifier.
Now it’s time to measure the noise figure of our amplifier. To do so, we just have to remove the noise source from the front end of the analyzer and in its place connect the DUT, with the noise source at the input of the DUT.
Looking at the graph here we see that our noise figure is a little above 6 dB and the gain is about ~20 dB which isn’t terrible … but ideally we would like to see our noise figure be under 3 dB.
Noise figure is an easy measurement for characterizing a device’s signal-to-noise ratio (SNR) as a signal passes through a system or device.
#noisefigure #noisefiguremeasurement #signalanalyzer #spectrumanalyzer #rfengineering #signalsource #signalgenerator #keysight #rfengineering - Věda a technologie
![Noise Figure Measurement [Gain Method]](http://i.ytimg.com/vi/IgXKS0yJ1-E/mqdefault.jpg)
![Noise Figure Measurement [Gain Method]](/img/tr.png)
Some of the nerdiest thing I've ever seen on youtube, and I love it. Used to be an electrician but changed career path :)
I will try to watch all of your videos. Great work!!
Good episode on the measurement of NF. Thank you !
#dwdmotn #NortelTn #Ciena32slot
Digital modulation, coding, and error correction also enabled small aperture antennas.
Very clear and informative video.
The noise source has to be powered from the back of the PXA unit?
hi, one question: why ,in this case , NF have to be under 3 Db?! why not less? thx .-)
You could have at least shown the DUT connected to Analyzer. For new engineer, it will be helpful.
Everyone has that one coworker that's blown a powerhead
God I want that signal analyser!
Great video! Thank you for posting.
Nice I’m an RX designer Will ask my boss for one 😊
What's different Noise Figure Analyzer vs Spectrum Analyzer with Opt NFA
Not much at that point. You can still do NF measurements and without the NFA option. If your noise is about 10 dB above the DANL of the spectrum analyzer you can resolve the NF with nearly identical accuracy. We don’t have a NF analyzer so I do it with a spectrum analyzer, which is so much slower but it can still be done!
What is the diff between spectrum analyser and signal analyser?
I'm going to pull from an app note for this:
"Traditionally, spectrum analyzers are referred to as swept-tuned, super-heterodyne receivers that
provide a display of amplitude versus frequency. Today’s analyzers offer both swept-tuned and Fast
Fourier transform (FFT) architectures.
While the terms spectrum analyzer and signal analyzer are used interchangeably, signal analyzer is a
more accurate term for today’s analyzers that combine the superior dynamic range of a swept tuned
spectrum analyzer with vector signal analyzer (VSA) capabilities and enable in-channel measurements
such as error vector magnitude (EVM), requiring both magnitude and phase information. The signal
analyzer’s versatility comes from the implementation of a fully digital intermediate frequency (IF)
replacing the analog IF used in traditional spectrum analyzers."
Are you in 290 degrees kelvin environment temperature ?
Nice #dwdmotn #NortelTn #Ciena32slot
Show connection boss... See the videos by R&S and improve the quality
Be careful with that beasty analyzer. Almost skipped a beat when you tended to fall. Having that noise generator signal at front of the panel would be helpful when accessibility is concerned.
Why we don't care about noise analysis in the power amplifier, even though its noise contribution is less in the system (being the last stage)?
Because typically the signal is so much greater then the noise it can be easily seen. Typically the amplifier also won’t be the largest source of noise in a system. For the most part SFDR is the most important number as it combines everything into one
what the f is that intro supposed to be? a new tv program for little kids?
*what the RF is that intro supposed to be?
sorry
Shit for nigga 'engineers'
Just when you feel you get the gist of what's going to happen in the video, the unnecessary intro ruins it.
Sure, you could have fun adding the goofy scenes, but try changing when you add them.
To learn more about this, watch electroboom XD.
I want a fieldfox. OH our RF
Field foxs are nice, I set them up for a university lab, but they’re time domain devices and are limited in ability compared to a RF swept device
This is just a demo of equipment and no much educational value
BS video! Is this cartoon?!!! where did you connect the noise source to? why didn't you take its noise into consideration?!!!