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Just starting to gain understanding on how various Radio components work (PA, LNA, LO, Mixer, etc.). Every component has ratings from the component manufacturer. I am curious to know, what effect we may see when these radio components are exercised to extreme temperatures. How does temperature affect the Radio performance?

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As far as radio performance goes, temperature has a measurable effect on receiver performance. A receiver is rated for a certain sensitivity, and if thermal noise exceeds it, you have a reduction in signal-noise ratio as thermal noise contributes to the overall noise floor. Thermal noise power is calculated in dBm/Hz by the formula 10Log_10(kTB*10^3) where k is Boltzmann's constant (1.3803*10^-23), T is temperature in Kelvin, and B is bandwidth in Hz. At room temperature with a receive bandwidth of 1 Hz, thermal noise is usually about -174 dBm/Hz. To see the effect on a receiver, you need to subtract thermal noise from your receive signal level (RSL). This gives you your SNR. All of these will change at any given time due to bandwidth, frequency, temperature, and a myriad of other variables, so it is beneficial to learn the calculations and put them in a spreadsheet to make quick use of them when you need them.

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The ratings might indicate temperatures at which the component completely fails - either temporarily or permanently. Less dramatic effects are changes in phase/group delay, voltage fluctuations, etc. Additionally, boards can flex causing weak connections or causing problems at any cold solder joints.

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With FETs in radio circuits, at higher temperatures the amps/volt drops off and the FETS provide less charge/picosecond thus the frequency response drops off.

When you say "extreme" does that mean outside the semiconductor process models?

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