RF measurements with non-hysteretic SQUID

A theoretical analysis not restricted to the small signal regime for the behavior of a non-hysteretic RF SQUID in RF measurements application is given. The modulation depth of the in-phase and out-of-phase components of the SQUID output voltage are calculated. It is shown that the dc magnetic flux bias should be adjusted to the value nΦ
0
/2, where Φ
0
is the flux quantum. At that point it is possible to use a simple amplitude detector and the SQUID input resistance does not affect RF power measurements. The condition for the coupling between the SQUID ring and resonant circuit which has to be fulfilled is also found.