BIDIRECTIONAL
VARIABLE PHASE
SHIFTER (BVPS) OUT A OUT B
1.85 mm
INPUT1 INPUT2 INPUT3 INPUT4
2.5 mm
A 60 GHz RF-combined 4-ele-
ment phased array front-end is implemented in silicon using a novel hybrid parallel/series-fed approach that
reduces on-chip phase shifter requirements. The array, which includes amplitude control as well as
continuous phase adjustment, provides for simultaneous illumination of
two angles of incidence. We combine
the series-fed and parallel-fed array
architectures to further relax the RF
phase-shifter requirements to enable
RF signal-combining. As shown in
the simplified block-diagram of
Figure 3a, discrete phase shifters (DP)
in every element choose one of two
phase-shift settings (e.g., 0° or 180°
in Element 2). The signals are then
fed into bidirectional series phase
shifters, each of which provides a certain amount of phase shift. The important point is that the signals on the
series phase shifters travel in both directions, yielding the following signal
summations at the two outputs providing for two concurrent receive
beams. The input to each element is
first amplified by a four-stage 60 GHz
LNA that has variable gain to compensate for downstream gain variation. The fourth stage of each LNA
provides variable
gain by current
steering. The output of the LNA is
provided to a DP
that can choose between two phase-shift settings. The
front-end has a
noise figure lower
than 6. 9 dB at 60
GHz and the array
achieves full spatial
coverage with better than 20 dB
peak-to-null ratio.
The four-element
60 GHz front-end
consumes 270 mW and occupies 4. 6
mm of die area. Figure 3b shows a
2
die photo of the array, which was implemented in a SiGe process with a
BJT cut-off frequency of 200 GHz.
TRANSCONDUCTANCE
STAGE (Gm_STAGE)
DISCRETE PHASE
SHIFTER (DPS)
VARIABLE GAIN
LNA (VG-LNA)
▲ Fig. 3b Die photograph of 60 GHz phased-array receiver
front-end.
DENSE LOW POWER
RADAR NETWORKS
Today’s weather forecasting and
warning infrastructure uses data
from high-power radars that have
helped meteorologists improve forecasts significantly in the past 20-plus
years.
Despite having substantial capability to measure wind and rainfall and
to diagnose storms, these long-range
radars have limited ability to observe
the lowest and most critical part of
the atmosphere owing to the Earth’s
curvature. This prevents the radars
from observing the behavior of tornadoes and other hazards at or near
ground level. As a result, one in five
tornadoes goes undetected by current
technology, and 80 percent of all tornado warnings turn out to be false
alarms. Raytheon, in partnership with
a team of academic, government and
industrial collaborators, has formed a
National Science Foundation Engi-
▲ Fig. 4a 128 T/R channel panel arrays,
radiator side.
▲ Fig. 4b 128 T/R channel panel arrays,
active components side.
