Low-Power 60-GHz CMOS Radios for Miniature Wireless Sensor Network Applications - Ultra-Wideband and 60 GHz Communications for Biomedical Applications - page 189

Fig. 7 Layout cross section
of an on-chip patch antenna
integrated in complementary
metal-oxide semiconductor
(CMOS) technology
efficiency due to the higher ground plane, but allows for reusing the area below the
patch for circuits and routing in a system-on-a-chip (SoC) application. For example,
conventional digital circuits typically use four to six metal layers for wire routing;
fewer metal layers is feasible, but at the cost of lower circuit density. Consequently,
the patch antenna is a good candidate for system integration in CMOS technology
because of the better performance (ground shielding) and reusable area beneath the
patch ground plane.
A 60-GHz Transmitter for WSNs
The 60-GHz band is an emerging field for miniature radio design because the sizes
of the antenna and passive components are at or below mm scale. Recently, sev-
eral highly integrated CMOS radio systems with on-chip antennas operating at the
mm-wave range have been reported [ 26 - 29 ], showing promising opportunities for
complete SoC integration. In this section, we will discuss the 60-GHz band allocation
and show a design example of a low-power 60-GHz frequency-locked loop (FLL)
that can serve as a fully integrated transmitter for WSNs. The transmitter described
in this section was designed in a 130-nm CMOS process with eight metal layers,
including a thick top metal for RF routing.
60-GHz Wireless Communication
The industrial, science, and medical (ISM) band approved by Federal Communica-
tions Commission (FCC) has 7 GHz of bandwidth from 57 to 64 GHz [ 30 ]. At 60