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Infineon BGT24LTR11 User Manual

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AN472
User's guide to BGT24LTR11
XENSIV™ 24 GHz radar MMIC
About this document
Scope and purpose
This application note describes the key features of Infineon's EVAL BGT24LTR11 board equipped with the
XENSIV™ 24 GHz BGT24LTR11N16 MMIC, and helps the user quickly get started with the evaluation board. It
provides:
Description of all the different building blocks of the MMIC.
•
Operation of the different blocks.
•
Measurement data showing behavior over temperature.
•
VCO control using different methodologies – PTAT, PLL, and a software-based open loop.
•
Intended audience
The intended audience for this document are design engineers, technicians, and developers of electronic
systems, working with Infineon's XENSIV™ 24 GHz radar sensors.
Related documents
Additional information can be found in the documentation from www.infineon.com/24GHz.
Application note
www.infineon.com
Please read the sections "Important notice" and "Warnings" at the end of this document
Revision 1.50
2023-02-14

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Summary of Contents for Infineon BGT24LTR11

  • Page 1 XENSIV™ 24 GHz radar MMIC About this document Scope and purpose This application note describes the key features of Infineon’s EVAL BGT24LTR11 board equipped with the XENSIV™ 24 GHz BGT24LTR11N16 MMIC, and helps the user quickly get started with the evaluation board. It provides: Description of all the different building blocks of the MMIC.
  • Page 2 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents Table of contents About this document ........................1 Table of contents ..........................2 Introduction .......................... 3 Building blocks ........................4 Transmitter .............................. 4 Receiver ..............................5 Voltage controller oscillator (VCO) ......................7 Proportional to absolute temperature (PTAT) voltage source ..............
  • Page 3 Table of contents Introduction BGT24LTR11 is a Silicon Germanium radar MMIC for signal generation and reception, operating in the 24.0 GHz to 24.25 GHz industrial, scientific and medical (ISM) band. It is based on a 24 GHz fundamental voltage- controlled oscillator (VCO). The device was designed with Doppler-radar applications in mind—as it is capable of keeping the transmit signal inside the ISM band without any external phase-locked loop (PLL) —...
  • Page 4 Building blocks Transmitter BGT24LTR11 has a single-ended transmitter output TX (pin 11) with a typical output power of 6 dBm. The transmitter’s output may be enabled and disabled by applying appropriate voltages to TX_ON (pin 5) as shown in Table 1.
  • Page 5 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents TX Output Power over Temperature Temperature [°C] Figure 3 TX output power with VTUNE connected to V_PTAT vs. temperature Receiver The receiver consists of an LNA followed by a quadrature direct-conversion mixer. Its input (RX, pin 3) is single ended.
  • Page 6 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents Noise Figure over RX Frequency and Temperature 24.05 24.1 24.15 24.2 24.25 RX Frequency [GHz] T=-40°C T=-20°C T=0°C T=25°C T=40°C T=60°C T=85°C Figure 5 Noise figure vs. RX frequency and temperature Conversion Gain over Rx Frequency and Temperature Temperature [°C]...
  • Page 7 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents Noise Figure over Rx Frequency and Temperature Temperature [°C] Rx=24GHz Rx=24.05GHz Rx=24.1GHz Rx=24.15GHz Rx=24.2GHz Rx=24.25GHz Figure 7 Noise figure vs. temperature and RX frequency Voltage controller oscillator (VCO)
  • Page 8 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents VCO Frequency over Temperature controlling with V_Ptat 24180 24170 24160 24150 24140 24130 24120 24110 24100 Temperature [°C] Figure 9 VCO frequency vs. temperature, VCO controlled by PTAT voltage source. Measured at random sample.

  • Page 9: Frequency Divider

    XENSIV™ 24 GHz radar MMIC Table of contents Frequency divider BGT24LTR11’s frequency divider has two divider ratios, divide by 16 and divide by 8182 which result in output frequencies of 1.5 GHz and 3 MHz respectively. Table 2 Setting the divider ratio...

  • Page 10: Evaluation Board

    Table of contents Evaluation board Schematic diagram Vctrl to VCC_PTAT BGT24LTR11 90° RFIN TX_ON 0° R_TUNE f-Div PTAT VTUNE V_PTAT VCC_PTAT VCC_DIV Figure 11 Schematic diagram of the BGT24LTR11 EVAL board Figure 12 Component placement Application note Revision 1.50 2023-02-14...
  • Page 11 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents Table 3 Bill of materials (BOM) Designation Part type Value Package Manufacturer C1, C5, C8 Chip capacitor 1 µF 0402 Various C2, C3, C6, C7, C9 0402 Chip resistor 16 kΩ...
  • Page 12 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents Layout Figure 14 Layout with description of pin headers BGT24AT2_Cross_Section_View.vsd Figure 15 Layer stackup Layout version improving TX to RX isolation The isolation between the TX port and the RX port on the standard evaluation board is typically about 25 dB.
  • Page 13 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents Conpensation Structures (Stubs) at TX Port Figure 16 Addition of compensation structures to increase TX to RX isolation Conpensation Structures (Stubs) at TX Port Via to GND 0.3x0.3mm²...
  • Page 14 Block diagram of using V_PTAT to keep BGT24LTR11 in the ISM band BGT24LTR11 was designed to keep its transmit frequency inside the ISM band without the need for a dedicated frequency control circuit like a PLL or an LUT based control of VTUNE. In Doppler radar mode, frequency adjustment via V_PTAT is the most efficient way.
  • Page 15 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents There are two reasons for toggling VCC and VCC_PTAT: Turning off VCC and VCC_PTAT reduces current consumption (45 mA and 1.5mA, respectively) • The PTAT source generates noise at its output when running, and this noise on the tuning voltage will •...
  • Page 16 VCO control using a PLL A PLL can be connected to the BGT24LTR11 to control the VCO as shown in Figure 19. To implement this, the frequency divider needs to be set to a ratio of 16 by connecting VCC_PTAT to GND.

  • Page 17: Hardware Setup

    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.
  • Page 18 VCO frequency to be in a steady state at the end of step-time when the baseband analog-to-digital converter (ADC) is triggered for measurement. As an option, connect the V_PTAT output from BGT24LTR11 to an ADC channel of the MCU to determine the •...
  • Page 19 MCU master clock – e.g., 80 MHz – are counted) results in a lower impact of this systematic error on VCO frequency measurement accuracy. However, longer counting gate time results in a longer ON time for the BGT24LTR11 and impacts the overall power consumption. T_gate =N*t_q1= counting gate time...

  • Page 20: Operation

    User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Table of contents For a divider output frequency of ~3 MHz and an MCU master clock of 80 MHz, we recommend counting over 100 periods (N=100) of the divider output signal, to get a maximal frequency measurement error < 10 MHz.
  • Page 21 User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC References References Infineon Technologies AG. BGT24LTR11N16 MMIC Datasheet Application note Revision 1.50 2023-02-14...

  • Page 22: Revision History

    User's guide to BGT24LTR11 XENSIV™ 24 GHz radar MMIC Revision history Revision history Document Date Description of changes revision 1.30 2017-11-03 Initial version 1.40 2019-07-09 8 f: Corrections to PTAT source Section 4: Detailed description of the VCO control through PTAT, PLL and Software-controlled loop 1.50...
  • Page 23 Infineon Technologies hereby Infineon Technologies’ products may not be used in disclaims any and all warranties and liabilities of any applications where a failure of the product or any any kind (including without limitation warranties of © 2023 Infineon Technologies AG.

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