Application Note
page 18 of 32
V1.0
2021-03-31
Distance2GoL (Software-Controlled FMCW) low-power radar shield using
BGT24LTR11 for range detection and human tracking
Hardware description: BGT24LTR11 Shield
4.8
Analog baseband section
The BGT24LTR11 provides both in-phase and quadrature-phase Intermediate Frequency (IF) signals from its
receiver. Depending on the target in front of the radar antennas, the analog output signal from the BGT24LTR11
chipset can be very low in amplitude (
µ
V to mV range). To process these low-amplitude signals, it is necessary
to amplify the IF signals.
The BGT24LTR11 Shield offers two stages of signal amplification using low-noise op-amps. As shown in Figure
12 and Figure 13, the I/Q outputs of the BGT are filtered and amplified in the first gain stage. The second gain
stage consists of a multiple-feedback active filter topology, which provides additional gain and bandpass
filtering to the output of the first gain stage. The low-gain and high-gain output signals are low-pass filtered to
avoid aliasing. A voltage divider is used to create the 1.65 V reference voltage. Both stages of op-amps are duty
cycled for low power consumption.
IFI_LG
IFI_HG
IFQ_LG
IFQ_HG
Base band section
IFI
IFQ
BGT24LTR11
C
o
n
n
ec
to
r to
R
ad
ar
B
aseb
o
ar
d
XMC
47
00
LP anti-aliasing filter
Multiple feedback LPF
LP anti-aliasing filter
Multiple feedback LPF
Figure 12
Baseband amplifier chain
–
block diagram
Non-inverting BPF
Multiple feedback LPF
LP anti-aliasing filter
Figure 13
Baseband amplifier chain
–
schematic
