{"id":7578,"date":"2023-04-22T17:48:28","date_gmt":"2023-04-22T12:18:28","guid":{"rendered":"https:\/\/nuclearrambo.com\/wordpress\/?p=7578"},"modified":"2024-10-03T15:04:04","modified_gmt":"2024-10-03T09:34:04","slug":"noise-figure-measurement-with-tinysa-ultra","status":"publish","type":"post","link":"https:\/\/nuclearrambo.com\/wordpress\/noise-figure-measurement-with-tinysa-ultra\/","title":{"rendered":"Noise Figure measurement with TinySA Ultra"},"content":{"rendered":"\n

In an article I wrote long time ago, I measured the noise figure<\/a> of an amplifier using only a spectrum analyzer. The method I used was relatively simple but it took some mathematical understanding and some manual calculations. <\/p>\n\n\n\n

A few years ago, compact, affordable RF instruments started making an entry into the hobbyist market. Being open-source, everyone loved them and a lot of people contributed into the betterment of those RF instruments. I reviewed the NanoVNA<\/a> and the NanoVNA v2<\/a> when they were just starting to become popular back in the day. I wrote quite a few articles about those instruments which you can find on this blog<\/a>. The low cost VNAs were far apart from the multi-thousand-dollar beasts that still dominate the market today but their performance was good enough for someone having no budget to purchase such costly instruments. They quickly found their way into the hands of startups, hobbyists and universities. The NanoVNAs were good to characterize 2-port networks such as filters, amplifiers, cables, etc. <\/p>\n\n\n\n

At the time, people with low budget preferred to use SDRs for signal analysis\/spectrum analysis. In no time, we had the TinySA show up in the online markets. It only worked up to 800 MHz but it was good enough for low frequency stuff. It did everything a large, expensive spectrum analyzer could do, only slowly. Later, the TinySA Ultra mode stretched the frequency limit all the way to 6GHz. <\/p>\n\n\n\n

In this article, I will be showing the noise figure measurement capability of the TinySA Ultra. It works on the same principle I described in my previous article here<\/a>. It only does it better and you don’t have to do manual calculations to arrive at the noise figure. <\/p>\n\n\n\n

Step 1: Measure the gain of your amplifier<\/h2>\n\n\n\n

The very first step involves obtaining the gain measurement of the amplifier. For this, we need some form of RF source to inject a signal into the input of the amplifier. Eventually, we measure the output power level from the amplifier. We would be performing our measurements at 500MHz.<\/p>\n\n\n\n

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  1. Connect the RF signal source directly to the spectrum analyzer. Make sure the RF source does not exceed the power level limit of the TinySA ultra. We don’t want to damage our instrument.<\/li>\n\n\n\n
  2. Note down the power level on the spectrum analyzer. <\/li>\n\n\n\n
  3. Now insert the amplifier between the RF source and the tinySA ultra. <\/li>\n\n\n\n
  4. Note down the power level you observe after the amplifier.<\/li>\n\n\n\n
  5. Compute the gain<\/li>\n<\/ol>\n\n\n\n\n\n\n\n

    \\(Gain(dB) = P_{out} – P_{in}\\)<\/p>\n\n\n\n

    Here, both the powers are in dBm. <\/p>\n\n\n\n

    If required, you can also use an attenuator to limit the power from exceeding. <\/p>\n\n\n\n

    Measuring the input power<\/h3>\n\n\n\n

    You can use any RF source for this purpose that’s capable of generating low output powers. It’s recommended to use lower power levels in the range of -50dBm to -30dBm while testing amplifiers. We don’t want to damage the input stage of the tinySA with excessive power. I used the PlutoSDR as my RF source controlled by the SATSAGEN<\/a> software. This is my first time using it and I totally recommend giving it a try. <\/p>\n\n\n\n

    I used the “generator” mode to use PlutoSDR<\/a> as an RF source and I set the frequency to 500MHz. Honestly, I would usually go for higher frequencies but I don’t have any amplifier at the moment to use. <\/p>\n\n\n\n

    \"satsagen<\/a>
    Satsagen with PlutoSDR for generating 500MHz CW<\/figcaption><\/figure>\n\n\n\n

    I connected the PlutoSDR’s TX port directly to the TinySA ultra and measured the power. <\/p>\n\n\n\n

    \"\"<\/a>
    The input power that would feed the amplifier after the cable as seen on tinySA ultra<\/figcaption><\/figure>\n\n\n\n

    I set the power level to -50dBm. Correspondingly, I connect the PlutoSDR to the tinySA ultra and observe the power level of -51.9 +<\/span> 0.1dBm. Additionally, I also enabled trace averaging for stable measurement. <\/p>\n\n\n\n