
5-6 Sensors and Sensor Technology
5.2.2 Bi-SQUID
e standard dc SQUID (Figure 5.2) can be modied by adding a nonlinear inductance, in the form of
a th
ird
Jo
sephson
(F
igure
5.5a
)
ju
nction
[1
2]
. i
s
th
ird
ju
nction,
wh
en
co
mbined
wi
th
th
e
ma
in
in
duc-
tance
in th
e
lo
op,
ac
ts
as a sin
gle-junction
SQ
UID
yi
elding
a de
vice
(k
nown
as a bi
-SQUID)
th
at
ha
s
a
tr
iangular
V–Φ t
ransfer
f
unction
(
Figure
5.5b
)
w
ith
si
gnicantly
i
mproved
l
inearity
.
5.2.3 Superconducting Quantum Interference Filters
An array of dierent superconducting loop sizes, in-series or in-parallel conguration or in a 2-D com-
bination
of bo
th,
ac
ting
as gr
ating
st
ructures,
ca
n
be us
ed ...