Hardware Setup - Infineon BGT24LTR11 User Manual

User's guide to BGT24LTR11
XENSIV™ 24 GHz radar MMIC
Table of contents
4.3 VCO control using a software based open-loop concept
It is possible to control BGT24LTR11 using a software-based open loop concept. In this approach, a loop is
needed with a voltage source and feedback which is used to adapt the needed frequency changes. This
implementation has the advantage of reducing the PCB space, BOM cost and power consumption by
eliminating the HW PLL.
In this software based open-loop concept – often called as "Software PLL" – there is no VCO phase and
frequency locking to a reference signal. Frequency is measured periodically and VCO is tuned accordingly. VCO
Phase Noise (PN) is comparable to the freewheeling VCO (best case) and not improved like the HW PLL can do.
However, VCO PN is less critical in Short Range Radar applications, because PN in the TX, RX and LO path stays
mainly correlated for short target distances, resulting is a strong reduction of residual PN in the down-mixed IF.
(referring to: Range Correlation Effect).
Both Doppler radar and stepped-FMCW radar can be realized with this software based open-loop VCO
adjustment/sweeping concept. System-performance might be lower than a HW PLL, but is often sufficient for a
lot of applications like smart lighting or proximity detection etc.
4.3.1

Hardware setup

TX_ON
Figure 20 Block diagram of VCO control using a software-based open-loop concept
Application note
VCC
VCC
TX
MPA
f-Div
(/8192)
DIV
VCC_DIV
DECISION
CCU
FUNCTION
GPIO
IFI IFQ
BGT24LTR11
IFQ
90°
LNA
0°
IFI
R_TUNE
PTAT
V_PTAT
VTUNE
RC filter
Temperature
DAC
LUT ADC
MCU
17
RFIN
VCC
Revision 1.50
2023-02-14