Application Note
page 11 of 33
V1.7
2022-08-01
XENSIV™ BGT60LTR11AIP shield
60 GHz radar system platform
Hardware description
BGT60LTR11AIP
IFIAix
C
HP
C
hold
IFIAox
S&H switch
R
mixer_out
Pulsed mixer output
(AC + DC
superposed)
R
HP
V
CC
/2
External capacitors
Figure 11
External capacitors for BGT60LTR11AIP
Longer pulse width can have a higher
𝐶
ℎ𝑜𝑙𝑑
value. This leads to a reduced bandwidth (BW) of the RC filter
(
𝑅
𝑚𝑖𝑥𝑒𝑟_𝑜𝑢𝑡
&
𝐶
ℎ𝑜𝑙𝑑
). Consequently, there will be a lower baseband noise because of reduced noise folding
bandwidth.
For this RC structure, the low-pass 3dB cutoff frequency
(𝑓
𝐿𝑃
3𝑑𝐵
)
can be calculated under the following
conditions:
𝑡
𝑟𝑖𝑠𝑒
=
10% / 90% = S&H ON time = 4µs
Pulse width =
5 µs
𝑅
𝑚𝑖𝑥𝑒𝑟_𝑜𝑢𝑡
=
300 Ω
𝑓
𝐿𝑃
3𝑑𝐵
=
0.35
𝑡
𝑟𝑖𝑠𝑒
=
0.35
4µ𝑠
= 87.5 𝑘𝐻𝑧
Or based on the formula:
𝑓
𝐿𝑃
3𝑑𝐵
=
1
2𝜋 × 𝑅
𝑚𝑖𝑥𝑒𝑟_𝑜𝑢𝑡
× 𝐶
ℎ𝑜𝑙𝑑
𝐶
ℎ𝑜𝑙𝑑
= 6.1 𝑛𝐹
→ 5.6 𝑛𝐹 (
closest E12 series value)
The high-pass 3dB cutoff frequency
(𝑓
𝐻𝑃
3𝑑𝐵
)
can be calculated under the following conditions:
𝐶
𝐻𝑃
=
10 nF
𝑅
𝐻𝑃
=
4 M
Ω
𝑓
𝐻𝑃
3𝑑𝐵
=
1
2𝜋 × 𝑅
𝐻𝑃
× 𝐶
𝐻𝑃
=
1
2𝜋 × 4𝑀𝛺 × 10𝑛𝐹
= 4 𝐻𝑧
3.6
Connectors
The BGT60LTR11AIP shield can be connected to an MCU board, like the Radar Baseboard MCU7, with the P1 and
P2 connectors
.
Visible on the top and bottom side of the PCB are the castellated holes (P3 and P4). TD and PD
pins of the castellated holes correspond to the internal detector outputs of the MMIC.
