VCA8500_0803 Datasheet, PDF (30/40 Pages) Texas Instruments – 8-Channel, Ultralow-Power, Variable Gain Amplifier with Low-Noise Pre-Amp

VCA8500
SBOS390A – JANUARY 2008 – REVISED MARCH 2008
The resulting signal current then passes through the
8×10 switch matrix. Depending on the programmed
configuration of the switch matrix, any V/I amplifier
current output can be connected to any of 10 CW
outputs. This design is a simple current-summing
circuit such that each CW output can represent the
sum of any or all of the channel currents. The CW
outputs are typically routed to a passive LC delay
line, allowing coherent summing of the signals.
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After summing, the CW signal path further consists of
a high dynamic range mixer for down-conversion to
I/Q base-band signals. The I/Q signals are then
band-limited (that is, low-frequency contents are
removed) in a filter stage that precedes a pair of
high-resolution, low sample rate ADCs.
L 220mH
CW0
CW1
CW2
CW3
VCA8500 _CW4
CW Out
8 In By 10 Out CW5
CW6
CW7
CW8
CW9
V_CM0
(+2.5V)
Amplifier
Passive
Delay
Line
0
90
I and Q
Channel
ADC
ADC
Clock
CW0
CW1
CW2
CW3
VCA8500 _CW4
CW Out
8 In By 10 Out CW5
CW6
CW7
CW8
CW9
Figure 69. Conceptual CW Doppler Signal Path Using Current Summing and a Passive Delay Line for
Beamforming
30
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