I’ve read some articles about anti-jamming GNSS antennas. Some antennas are said to resist jamming signal of 50V/m while others have 15dB J/S ratio. Well, both seem to be the specification describing the anti-jamming capability. Can they be compared somehow?
Input power varies according to antenna, the primary unit of received signal strength is power density or field strength, both are related by impedance of free space. The field strength probably varies with satellite elevation angle.
A typical GPS receive field strength is in a µV/m range, e.g. 2 µV/m corresponds to -135 dBm with 0 dBi antenna gain.
You can refer to an R&S application note for the calculation