Page 331 - System on Package_ Miniaturization of the Entire System

Radio Fr equency System-on-Package (RF SOP) 305

Tree-junction
LCP
Tree-
junction
Gold

RF Silicon
Probe nitride
pad

Bias pad
MEMS
LCP

(a)

0 −0.5
−1
−10 −1.5
S21
S11 −2
S 11 (dB) −20 −2.5 S 21 (dB)
−3
−30
−3.5
−4
−40
−4.5
−50 −5
10 12 14 16 18
Frequency
(b)
FIGURE 5.41 (a) Fabricated MEMS phase-shifter substrate. The superstrate has been removed,
and cutouts represent the location of the cavities and probing windows. (b) Measurement results
for MEMS switches bonded using tension or epoxy. The presence of the epoxy adds a minimal
amount of insertion loss. [76]

on the phase-shifter performance due to its low-loss characteristics, but enables the
device to remain flexible and provides protection against various environmental
conditions. A comparison of the measured loss for a tension and epoxy bonded
MEMS switch is shown in Figure 5.41b. The average variations in S and S are 3.69 dB
11 21
and 0.087 dB, respectively, at 14 GHz.

5.4.11 RFIDs
The demand for radiofrequency identification tags (RFIDs) has rapidly increased due to
the need for automatic identification in various areas, such as item-level tracking, access
control, electronic toll collection, and vehicle security. Compared with the use of lower-
frequency tags in the LF and HF bands, which suffer from a limited read range (1 to 2 feet),
RFID tags in the UHF band see the widest use due to their higher read range (over 10 feet)