AN472 User's Guide to BGT24LTR11N16 24GHz Radar About this document Scope and purpose This application note is intended to put flesh on the bones of BGT24LTR11N16's datasheet. The datasheet gives technical data and limits of the device itself but it is not explaining the device in greater detail. This application note takes care of this issue. The reader will find here: Discussion of all different building blocks How to operate the different blocks Additional measurement data showing behavior over temperature Intended audience Hardware engineers and software engineers working on designs with Infineon's BGT24LTR11N16. Table of Contents About this document......................................................................................................................................................................... 1 Table of Contents ............................................................................................................................................................................... 1 List of Figures...................................................................................................................................................................................... 2 List of Tables ....................................................................................................................................................................................... 2 1 Introduction to BGT24LTR11 ................................................................................................................................. 3 2 Building Blocks ........................................................................................................................................................... 4 2.1 Transmitter .......................................................................................................................................................................... 4 2.2 Receiver ................................................................................................................................................................................. 5 2.3 Voltage Controlled Oscillator (VCO) .......................................................................................................................... 7 2.4 Proportional to Absolute Temperature (PTAT) Voltage Source ................................................................... 8 2.5 Frequency Divider ............................................................................................................................................................. 9 3 Evaluation Board ...................................................................................................................................................... 10 3.1 Schematic Diagram ......................................................................................................................................................... 10 3.1.1 Matching Structures ................................................................................................................................................. 11 3.2 Layout of Evaluation Board ......................................................................................................................................... 12 3.3 Layout Version improving TX to RX Isolation ..................................................................................................... 13 4 Controlling the VCO ................................................................................................................................................. 14 4.1 Controlling the VCO using V_PTAT ........................................................................................................................... 14 4.1.1 Controlling the VCO with the PTAT source in detail................................................................................... 14 4.2 Controlling the VCO using a PLL ................................................................................................................................ 15 4.3 Controlling the VCO using a Software Based Open-Loop Concept .............................................................. 16 5 Authors........................................................................................................................................................................ 17 Revision History ............................................................................................................................................................................... 17 Application Note www.infineon.com Please read the Important Notice and Warnings at the end of this document Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Table of Contents List of Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 BGT24LTR11N16 Block Diagram .......................................................................................................................... 3 TX output power vs. frequency and temperature ........................................................................................... 4 TX output power with VTUNE connected to V_PTAT .................................................................................... 5 Gain vs. frequency......................................................................................................................................................... 5 Noise figure vs. frequency ......................................................................................................................................... 6 Conversion gain vs. temperature ........................................................................................................................... 6 Noise figure vs. temperature .................................................................................................................................... 7 VCO frequency over tuning voltage and temperature ................................................................................... 7 VCO frequency over temperature, VCO controlled by PTAT voltage source ....................................... 8 Voltage generated by PTAT voltage source vs. temperature...................................................................... 9 Schematic diagram .................................................................................................................................................... 10 Component placement ............................................................................................................................................. 10 Matching structures to be used on a Ro4350B substrate with a thickness of 0.254 mm ............ 11 Layout of evaluation board with description of pin headers .................................................................. 12 Layer stack.................................................................................................................................................................... 12 Adding compensation structures will increase TX to RX isolation ....................................................... 13 Compensation structures in detail. (Unit is mm) ......................................................................................... 13 Block diagram: Using V_PTAT to keep BGT24LTR11N16 in the ISM band ....................................... 14 Bock diagram: Controlling BGT24LTR11N16 with a PLL ......................................................................... 15 Block diagram: Controlling BGT24LTR11N16 with an Open-Loop concept..................................... 16 List of Tables Table 1 Table 2 Table 3 Table 4 Enabling/disabling TX output ................................................................................................................................. 4 Setting the divider ratio ............................................................................................................................................. 9 Bill of materials ........................................................................................................................................................... 11 13 Application Note 2 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Introduction to BGT24LTR11 1 Introduction to BGT24LTR11 BGT24LTR11 is Silicon Germanium radar MMIC for signal generation and reception, operating in the 24.0 GHz to 24.25 GHz 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 PLL -- and may also be used in other types of radar such as FMCW or FSK. A built-in voltage source delivers a VCO tuning voltage which is proportional to absolute temperature (PTAT). When connected to the VCO tuning pin it compensates for the inherent frequency drift of the VCO over temperature thus stabilizing the VCO within the ISM band eliminating the need for a PLL/Microcontroller. An integrated 1:16 frequency divider also allows for external phase lock loop VCO frequency stabilization. The receiver section uses a low noise amplifier (LNA) in front of a quadrature homodyne down-conversion mixer in order to provide excellent receiver sensitivity. Derived from the internal VCO signal, a RC-polyphase filter (PPF) generates quadrature LO signals for the quadrature mixer. I/Q IF outputs are available through single-ended terminals. The device is manufactured in a 0.18 m SiGe:C technology offering a cutoff frequency of 200 GHz. It is packaged in a 16-pin leadless RoHS compliant TSNP package. IFI VCC IFQ Balun LNA Balun Balun Polyphase Filter Balun TX VEE MPA Balun VEE Balun 90 VEE RFIN VEE 0 TX_EN f-Div VCC_DIV DIV PTAT VTUNE R_TUNE V_PTAT VCC_PTAT 20141208_BGT24LTR11_Block Diagram_TX_ON.vsd Figure 1 Application Note BGT24LTR11N16 Block Diagram 3 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Building Blocks 2 Building Blocks 2.1 Transmitter BGT24LTR11N16 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 the table below. Disabling the TX output will not save power as the output will be switched to an internal load while the rest of the chip is still running. This is necessary in case one wants to implement a software controlled oscillator (see section 4.3). Table 1 Enabling/disabling TX output Enable TX Voltage at TX_ON > 2 V Disable TX Voltage at TX_ON < 0.8 V TX Output Power over VCO Frequency and Temperature 10 9 TX Output Power [dBm] 8 7 6 5 4 3 23200 23400 T=-40C Figure 2 Application Note 23600 T=-20C 23800 24000 24200 VCO Frequency [MHz] T=0C T=25C T=40C 24400 T=60C 24600 24800 T=85C TX output power vs. frequency and temperature 4 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Building Blocks TX Output Power over Temperature 10 9 TX Output Power [dBm] 8 7 6 5 4 3 -40 Figure 3 -30 -20 -10 0 10 20 30 Temperature [C] 40 50 60 70 80 90 TX output power with VTUNE connected to V_PTAT 2.2 Receiver The receiver consists of an LNA followed by quadrature direct-conversion mixer. Its input (RX, pin 3) is single-ended. The voltage conversion gain is typically 20 dB with a single side-band noise figure of 10 dB. Conversion Gain over RX Frequency and Temperature 25 24 Conversion Gain, G [dB] 23 22 21 20 19 18 17 16 15 24 24.05 T=-40C Figure 4 Application Note 24.1 24.15 RX Frequency [GHz] T=-20C T=0C T=25C T=40C 24.2 T=60C 24.25 T=85C Gain vs. frequency 5 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Building Blocks Noise Figure over RX Frequency and Temperature 15 14 13 Noise Figure, NF [dB] 12 11 10 9 8 7 6 5 24 24.05 T=-40C Figure 5 24.1 24.15 RX Frequency [GHz] T=-20C T=0C T=25C T=40C 24.2 T=60C 24.25 T=85C Noise figure vs. frequency Conversion Gain over Rx Frequency and Temperature 24 23 Conversion Gain, G [dB] 22 21 20 19 18 17 16 -40 -20 Rx=24GHz Figure 6 Application Note 0 Rx=24.05GHz 20 40 Temperature [C] Rx=24.1GHz Rx=24.15GHz 60 Rx=24.2GHz 80 100 Rx=24.25GHz Conversion gain vs. temperature 6 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Building Blocks Noise Figure over Rx Frequency and Temperature 13 12 Noise Figure, NF [dB] 11 10 9 8 7 6 5 -40 -20 Rx=24GHz Figure 7 0 20 40 Temperature [C] Rx=24.05GHz Rx=24.1GHz 60 Rx=24.15GHz 80 Rx=24.2GHz 100 Rx=24.25GHz Noise figure vs. temperature 2.3 Voltage Controlled Oscillator (VCO) VCO Frequency over tuning voltage (V_Tune) and Temperature 24800 24600 VCO Frequency [MHz] 24400 24200 24000 23800 23600 23400 23200 0.7 0.8 0.9 T=-40C Figure 8 Application Note 1 T=-20C 1.1 1.2 T=0C 1.3 1.4 V_Tune [V] T=25C 1.5 T=40C 1.6 T=60C 1.7 1.8 1.9 2 T=85C VCO frequency over tuning voltage and temperature 7 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Building Blocks VCO Frequency over Temperature controlling with V_Ptat 24180 24170 VCO Frequency [MHz] 24160 24150 24140 24130 24120 24110 24100 -40 Figure 9 2.4 -20 0 20 40 Temperature [C] 60 80 100 VCO frequency over temperature, VCO controlled by PTAT voltage source Proportional to Absolute Temperature (PTAT) Voltage Source The PTAT voltage source generates a voltage VPTAT at the V_PTAT pin (pin 15) which is proportional to the chip temperature. It is powered separate from VCC via the VCC_PTAT pin (pin 16). The PTAT voltage source serves two purposes: Generating tuning voltage for the VCO in Doppler mode. See section 4.1. Temperature sensor measuring chip temperature. The chip temperature Tchip can be calculated from VPTAT using the following equation: Tchip / C = 158.7 * (VPTAT / V) - 217.0 with VCC_PTAT = VCC =3.3 V and VCC_DIV open. Application Note 8 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Building Blocks V_PTAT over Temperature 2 1.9 1.8 V_PTAT [V] 1.7 1.6 1.5 V_PTAT = 0.0063V*(Temp/C) + 1.3669V R = 0.9986 1.4 1.3 1.2 1.1 1 -40 Figure 10 2.5 -20 0 20 40 Temperature [C] 60 80 100 Voltage generated by PTAT voltage source vs. temperature Frequency Divider BGT24LTR11N16's frequency divider has two divider rations, 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 Divider ratio 16 8192 Voltage at VCC_PTAT (pin 16) < 0.8 V 3.3 V Setting the divider to a 3 MHz output will cause the PTAT to consume current. This ratio is usually used only in case of a software controlled VCO and for this use cases a temperature sensor is required anyways to check the validity of the used look-up table. Application Note 9 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Evaluation Board 3 3.1 Evaluation Board Schematic Diagram VCC R5 Vctrl C8 IFI R6 IFQ to VCC_PTAT VCC Balun RFIN Balun LNA TX_ON Balun Polyphase Filter MPA Balun Balun TX Balun 90 0 R_TUNE f-Div VTUNE PTAT V_PTAT C1 C5 DIV R1 VCC_PTAT VCC_DIV Schematic_Evalboard_general.vsd Figure 11 Schematic diagram Figure 12 Component placement Application Note 10 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Evaluation Board Table 3 Bill of materials Designation C1, C5, C8 C2, C3, C6, C7, C9 R1 R2,R3 R5 R6 Q1 IC1 3.1.1 Part type Chip capacitor Value 1 F DNP 16 k 0 100 k 1 k BSS209PW BGT24LTR11N16 Chip resistor Chip resistor Chip resistor Chip resistor p-MOSFET Radar MMIC Package 0402 0402 0402 0402 0402 0402 SOT-323 TSNP-16-9 Manufacturer Various Various Various Various Various Infineon Infineon Matching Structures 1 W=600 um 3 L=1300um 2 W=1100um L=1290um W=1100um 2 1 3 4 W50=520 um TX Application Note 4 L=1300um W50=520 um 5 5 5 Figure 13 W=600 um L=1100um RX W1=300 um W2=600um L=950um Matching structures to be used on a Ro4350B substrate with a thickness of 0.254 mm 11 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Evaluation Board 3.2 Figure 14 Layout of Evaluation Board Layout of evaluation board with description of pin headers Blind-Vias Vias Ro4350B, 0.254mm Copper 35um FR4, 0.5mm FR4, 0.25mm BGT24AT2_Cross_Section_View.vsd Figure 15 Application Note Layer stack 12 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Evaluation Board 3.3 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. This isolation can be improved to 35dB by adding a grounded length of line at the ground pins next to the TX output pin as shown in Figure 16. Details of the used compensation structures can be found in Figure 17. Table 4 TX to RX isolation / dB PCB with compensation structures 35 0.16 Adding compensation structures will increase TX to RX isolation Via to GND 0.03 0.15 Figure 16 Standard evaluation PCB 25 0.3x0.3mm Package Pad 0.34 Figure 17 Application Note 0.26 1.75 0.09 Compensation structures in detail. (Unit is mm) 13 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Controlling the VCO 4 4.1 Controlling the VCO Controlling the VCO using V_PTAT VCC R5 Vctrl C8 IFI R6 IFQ to VCC_PTAT VCC Balun RFIN Balun LNA TX_ON Balun Polyphase Filter Balun MPA Balun TX Balun 90 0 R_TUNE f-Div VTUNE PTAT V_PTAT Schematic_Self_control1.vsd C5 Figure 18 R1 from Vctrl Block diagram: Using V_PTAT to keep BGT24LTR11N16 in the ISM band Exact frequency control in Doppler radars in the 24 GHz ISM band is not really necessary for most applications. If we assume the transmit frequency to be at the lower edge of the band while it is actually at the upper edge the introduced error is only 0.8 %. BGT24LTR11N16 was designed to keep its transmit frequency inside the ISM band without the need for a dedicated frequency control circuit like a Phase Locked Loop (PLL) or a look-up table based control of VTUNE. To achieve this capacitor C5 is charged by V_PTAT while the rest of the chip is turned off to save power. Once C5 is fully charged VCC_PTAT is disconnected while VCC is applied and VTUNE gets its voltage from C5. There are two reasons for toggling VCC and VCC_PTAT. The first one is obvious: Turning off VCC and VCC_PTAT reduces current consumption (45 mA and 1.5mA, respectively). The second reason for turning off VCC_PTAT is that the PTAT source generates noise at its output when running and this noise on the tuning voltage will degrade the signal to noise ratio (SNR) of the system. Of course for some short range this SNR might still be acceptable. 4.1.1 Controlling the VCO with the PTAT source in detail One duty-cycle works as follows: 1. TX_ON = 0 V. Disables TX output to prevent out of band emissions. 2. Vctrl = 3.3 V. This turns on the PTAT source (VCC_PTAT = 3.3 V) while VCC is disconnected from power supply. Application Note 14 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Controlling the VCO 3. Wait for C5 to be charged. At the start-up of the system when the capacitor is fully discharged this will require a longer time. During normal operation the capacitor is only slightly discharged and will be very quickly recharged. 4. Vctrl = 0 V. Turns off PTAT and turns on the rest of the chip. 5. Wait for VCO to settle its frequency. Settling time of the VCO is maximum 100 ns. 6. TX_ON = 3.3 V. Enables TX output. 7. Sample IF frequency. 8. Goto 1. Further reduction of the power consumption is possible by introducing a time frame when both VCC and VCC_PTAT are disconnected. This would mean that VCC_PTAT needs to be disconnected from Vctrl and one more GPIO pin needs to be available at the microcontroller in the system. 4.2 Controlling the VCO using a PLL VCC IFI IFQ VCC Balun RFIN Balun LNA TX_ON Balun Polyphase Filter Balun MPA Balun TX Balun 90 0 R_TUNE f-Div PTAT V_PTAT VCC_PTAT C1 DIV VTUNE VCC_DIV Block-diagram_PL.vsd PLL Figure 19 Bock diagram: Controlling BGT24LTR11N16 with a PLL Controlling BGT24LTR11N16's VCO with a RF Phase Locked Loop (PLL) is straight forward. The frequency divider needs to be set to a ratio of 16 by connecting VCC_PTAT to GND. The 1.5 GHz can then be used to feed the PLL, which in turns generates the tuning voltage. Application Note 15 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Controlling the VCO 4.3 Controlling the VCO using a Software Based Open-Loop Concept VCC IFI IFQ VCC Balun RFIN Balun LNA Balun Polyphase Filter MPA Balun Balun TX Balun 90 0 TX_ON R_TUNE f-Div PTAT V_PTAT VTUNE VCC_DIV VCC DIV Temperature CCU LUT DAC MCU Block-diagram_software_loop.vsd Figure 20 Block diagram: Controlling BGT24LTR11N16 with an Open-Loop concept It is possible to control BGT24LTR11N16 using an Open-Loop concept, sometimes also called Software-Loop concept. Figure 20 shows a block diagram on how to set-up the system. The frequency divider is set to an 8192 division ratio and fed to a Capture Compare Unit (CCU) of the microcontroller to determine the frequency of the oscillator. The PTAT source is used as a chip temperature sensor and V_PTAT is fed to an ADC of the microcontroller. The microcontroller's DAC is used to generate the tuning voltage of the VCO. A GPIO port of the microcontroller enables / disables BGT24LTR11N16's TX output. Controlling BGT24LTR11N16 with an Open-Loop concept works as follows: 1. Disable TX output 2. Check the chip temperature 3. Generate a Look-Up Table (LUT) that gives the DAC values corresponding to different VCO frequencies. Use this LUT for the modulation of the VCO. 4. Enable TX output 5. Generate transmit signal using DAC 6. Check chip temperature. If chip temperature changed goto 1 else goto 5 Application Note 16 Revision 1.1 2017-07-11 User's Guide to BGT24LTR11N16 24GHz Radar Authors 5 Authors Dietmar Stolz, Senior Staff Engineer of Business Unit "Radio Frequency and Sensors" Revision History Major changes since the last revision Page or Reference 12 f Application Note Description of change Added section on improving TX to RX isolation 17 Revision 1.1 2017-07-11 Trademarks of Infineon Technologies AG HVICTM, IPMTM, PFCTM, AU-ConvertIRTM, AURIXTM, C166TM, CanPAKTM, CIPOSTM, CIPURSETM, CoolDPTM, CoolGaNTM, COOLiRTM, CoolMOSTM, CoolSETTM, CoolSiCTM, DAVETM, DI-POLTM, DirectFETTM, DrBladeTM, EasyPIMTM, EconoBRIDGETM, EconoDUALTM, EconoPACKTM, EconoPIMTM, EiceDRIVERTM, eupecTM, FCOSTM, GaNpowIRTM, HEXFETTM, HITFETTM, HybridPACKTM, iMOTIONTM, IRAMTM, ISOFACETM, IsoPACKTM, LEDrivIRTM, LITIXTM, MIPAQTM, ModSTACKTM, mydTM, NovalithICTM, OPTIGATM, OptiMOSTM, ORIGATM, PowIRaudioTM, PowIRStageTM, PrimePACKTM, PrimeSTACKTM, PROFETTM, PRO-SILTM, RASICTM, REAL3TM, SmartLEWISTM, SOLID FLASHTM, SPOCTM, StrongIRFETTM, SupIRBuckTM, TEMPFETTM, TRENCHSTOPTM, TriCoreTM, UHVICTM, XHPTM, XMCTM Trademarks updated November 2015 Other Trademarks All referenced product or service names and trademarks are the property of their respective owners. Edition 2017-07-11 Published by Infineon Technologies AG 81726 Munich, Germany ifx1owners. (c) 2017 Infineon Technologies AG. All Rights Reserved. Do you have a question about this document? Email: erratum@infineon.com Document reference AN_472_2016_03_PL32_001 IMPORTANT NOTICE The information contained in this application note is given as a hint for the implementation of the product only and shall in no event be regarded as a description or warranty of a certain functionality, condition or quality of the product. Before implementation of the product, the recipient of this application note must verify any function and other technical information given herein in the real application. Infineon Technologies hereby disclaims any and all warranties and liabilities of any kind (including without limitation warranties of non-infringement of intellectual property rights of any third party) with respect to any and all information given in this application note. 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