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I have been testing the GPS / GPRS development module A9G, Aithinker which uses an active GPS antenna, according to the schematic reference diagram, the value of the inductance is 82nH:

enter image description here

The question is how did they reach the value of 82nH? and how the other parameters of the inductor are chosen, taking into account that the data of the antenna are:

High performance Beidou + GPS Antenna

Frequency range 1561MHZ 1575.42MHZ

Gain 28dBi

SWR ≤2.0

Beam width right-handed circular polarization(RHCP)

Input impedance 50Ω

Voltage 3-5v

Thank you

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The question is how did they reach the value of 82nH? and how the other parameters of the inductor are chosen.

This inductor is to filter VBAT power noise as the GPS is very sensitive. I designed some GPS boards with different modules and in my experience the filter you need between the GPS module and the rest of the circuit depends heavily on the power source and the rest of the circuit and there is no rule of thumb that is cheap and also realible.

In my experience the best strategy is to test different filters until it works as you expect. A cheap and good option is to use a ferrite bead or ferrite choke that has high impedance at 1.5GHz (the GPS frequency). But if the power source is noisy you may need to add a linear low noise regulator.

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