Low-Power 60-GHz CMOS Radios for Miniature Wireless Sensor Network Applications - Ultra-Wideband and 60 GHz Communications for Biomedical Applications - page 196

Fig. 14 Measured antenna
resonant frequency and
bandwidth distribution over
20 replicas
Fig. 15 Block diagram of the
60-GHz FLL. OOK on-off
keying, VCO voltage-
controlled oscillator, PA
power amplifier, LP low pass
not enough to prevent two patch antennas from overlapping in frequency responses.
On the basis of the measured S11 of 20 dies from a single wafer, no missed alignment
between two antennas was observed.
Frequency-Locked Loop
Figure 15 shows the block diagram of the 60-GHz FLL. The FLL mainly consists
of two parts: a feed-forward RF part and a feedback baseband part. The RF part
comprises a differential voltage-controlled oscillator (VCO), a buffered output of
the VCO, a power amplifier (PA), and the on-chip patch antenna reference. The
baseband part functions as a Proportional Integral (PI) controller, and has two enve-
lope detectors, an error amplifier, an integrator, and a loop filter. The VCO signal is
amplified by the PA and radiated through the antenna. The frequency of the VCO is