Infineon BGT60ATR24C Istruzioni per l'installazione e il funzionamento

Application note

Please read the sections “Important notice” and “Warnings” at the end of this document

Revision 1.10

www.infineon.com

2023-02-14

AN620

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

B o a r d v e r s i o n V 2 . 0

About this document

Scope and purpose

This application note describes the function, circuitry, and performance of the BGT60ATR24C shield

(SHIELD_60ATR24ES_01) , part of Infineon’s XENSIV™ 60 GHz radar system platform. The shield provides the

supporting circuitry to the on-board BGT60ATR24C monolithic microwave integrated circuit (MMIC) Infineon’s

60 GHz radar chipset with external antennas. The shield offers a digital interface for configuration and transfer

of the acquired radar data to a microcontroller board, e.g., Radar Baseboard MCU7.

The MMIC-related parameters mentioned in the document are based on engineering samples (ES).

Intended audience

The intended audience for this document are design engineers, technicians, and developers of electronic

systems, working with Infineon’s XENSIV™ 60 GHz radar sensors, especially in automotive scenarios called in-

cabin sensing (ICMS). Among the many applications it can be used for are–rear occupancy alert (ROA) and –left

behind child (LBC) systems.

Related documents

Additional information can be found in the documentation provided with the Radar Development Kit tool in the

Infineon Developer Center (IDC), or from www.infineon.com/60GHz.

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

Table of contents

About this document....................................................................................................................... 1

Table of contents............................................................................................................................ 2

1Introduction .......................................................................................................................... 3

1.1 60 GHz radar system platform ................................................................................................................3

1.2 Key features.............................................................................................................................................3

2System specifications............................................................................................................. 4

2.1 Typical power consumption ...................................................................................................................4

3Hardware description............................................................................................................. 5

3.1 Overview..................................................................................................................................................5

3.2 Sensor supply..........................................................................................................................................5

3.3 Oscillator..................................................................................................................................................6

3.4 Connectors ..............................................................................................................................................7

3.5 EEPROM ...................................................................................................................................................7

3.6 Layer stackup ..........................................................................................................................................8

3.7 Metal layers overview..............................................................................................................................8

4Layout overview ...................................................................................................................10

4.1 Component side ....................................................................................................................................10

4.2 Antenna side..........................................................................................................................................10

5TX and Rx channels................................................................................................................12

5.1 Phase relationship between RF channels ............................................................................................12

5.1.1 TX outputs ........................................................................................................................................12

5.1.2 RX channels ......................................................................................................................................12

6Measurement results.............................................................................................................13

6.1 Transmitter and receiver antenna matching .......................................................................................13

6.2 System radiation characteristics..........................................................................................................14

References....................................................................................................................................19

Revision history.............................................................................................................................20

Disclaimer.....................................................................................................................................21

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

Introduction

1Introduction

1.1 60 GHz radar system platform

The 60 GHz radar system platform is the demo platform for Infineon’s 60 GHz radar solutions. It consists of the

Radar Baseboard MCU7 as the microcontroller board and a radar sensor board, like the BGT60ATR24C shield for

Infineon’s 60 GHz radar sensor chip. This application note focuses on the BGT60ATR24C shield. Detailed

information about the Radar Baseboard MCU7 can be found in the corresponding application note [1].

Figure 1 illustrates the Radar Baseboard MCU7 with the BGT60ATR24C shield. The shield has to be plugged into

the longer connectors on the baseboard’s bottom side with an orientation as shown below.

Sensor board (antenna side) b) Radar Baseboard MCU7 (bottom side)

Figure 1 Radar Baseboard MCU7 with the BGT60ATR24C shield

1.2 Key features

The BGT60ATR24C shield is designed to showcase the capabilities of the BGT60ATR24C. This device offers

customers design flexibility in terms of their desired antenna configuration. It consists of two transmit and four

receive channels. The BGT60ATR24C shield facilitates fast prototyping and system integration, as well as initial

product feature evaluation. This board offers developers the flexibility to choose their own platform depending

on their preferred use cases. The sensor it incorporates various use cases, serving a broad array of applications

–including presence detection, LBC, ROA, proximity sensing, people counting/tracking, gesture recognition,

monitoring vital signs, etc. Presence detection may only require 1 mW of power in the sensor under certain

circumstances. In an automotive context, it can be of value in ROA, LBC and dashboard control. Other areas

where it might be applied are smart speakers, home/building automations and security/safety.

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

System specifications

2System specifications

2.1 Typical power consumption

The typical power consumption of the whole 60 GHz radar sensor platform, consisting of a Radar Baseboard

MCU7 and a BGT60ATR24C shield, can be found in Table 1 and Table 2. The microcontroller on the Radar

Baseboard MCU7 will change its mode of operation depending on the sensor that is plugged in and the signal

processing that is required. This will be acutely reflected in the microcontroller’s power consumption.

Table 1 Typical current consumption of the BGT60ATR24C shield

Table 2 Typical current consumption of the 60 GHz radar sensor platform

Condition

Power consumption of the BGT60ATR24C shield

Sensor attached but deactivated

(BGT60ATR24C in deep sleep mode)

~ 0.25 mW (BGT) + ~ 10 mW (crystal osc.)

BGT60ATR24C shield attached and in CW operation

(both TX on –maximum power consumption)

~ 500 mW

Condition

Power consumption of the radar system

MCU in reset

~ 10 mW

No sensor attached

~ 150 mW

Sensor attached but deactivated

(BGT60ATR24C in deep sleep mode)

~ 550 mW

BGT60ATR24C shield attached and in CW operation

(both TX on –maximum power consumption)

~ 1500 mW

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

Hardware description

3Hardware description

This section of the document presents a detailed overview of the BGT60ATR24C shield’s hardware specifications.

It covers BGT60ATR24C considerations, as well as the power supply, oscillator and board interfaces.

3.1 Overview

Top view

26 mm

Bottom view

16 mm

Figure 2 Top and bottom views of the BGT60ATR24C shield

The dimensions of the BGT60ATR24C shield are 26 mm x 16 mm. The BGT60ATR24C sensor is mounted on top

of the PCB, while on the bottom patch antennas have been located. The current design of the shield uses two

Rogers laminate layers for top and bottom (RO3003 top and RO4350B bottom). More details of the PCB stackup

are mentioned in section 3.6.

To provide the correct level shifter voltage for the MCU board, the 1.8 Vsensor supply line is connected with Vdigital –

refer to “Level shifters” section of application note AN599 [1]. When the shield is plugged into the Radar

Baseboard MCU7, the sensor’s supplies are initially deactivated. Only the EEPROM is powered. The

microcontroller will read the content of the EEPROM’s memory to determine which sensor is plugged into the

sensor interface. Actually, it is not mandatory to use this EEPROM with the BGT60ATR24C, as it has an internal

chip ID which can be read by SPI directly. The EEPROM is only for ensuring compatibility with other Infineon

chips that do not have the chip ID feature.

Radar sensors are very sensitive to noise and cross-talk on the supply domains. Therefore, the different supply

domains must be decoupled. On the BGT60ATR24C shield, this is realized by a pi-shaped low-pass filter on each

supply domain (and the oscillator supply). Communication with the radar sensor is mainly performed via a

serial peripheral interface (SPI) bus. Additionally, two more digital lines are required for operation. One line

signals the microcontroller when new data needs to be fetched. The other allows the microcontroller to

perform a hardware reset of the sensor. Furthermore, an LED indicator is mounted on the board. This allows

the microcontroller to signal (for example) if the sensor is activated or deactivated at that time.

3.2 Sensor supply

Since radar sensors are very sensitive to supply voltage fluctuations or cross-talk between different supply

domains, a low-noise power supply with properly decoupled supply rails will prove vital. The Radar Baseboard

MCU7 provides a low-noise supply (see section 2.2 of application note AN599 for further details). Figure 3

depicts the schematics of the pi-shaped low-pass filters employed to decouple the supplies of the different

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

Hardware description

power rails in the chip. High attenuation of voltage fluctuations in the MHz range is provided by ferrite beads.

For example, the SPI (which runs at up to 50 MHz) induces voltage fluctuations in the digital domain. These

fluctuations would then transfer into the analog domain if not for the decoupling filters incorporated. The

ferrite beads are chosen because they can handle the maximum current of the sensor (approximately 200 mA)

with a low DC resistance (below 0.25 Ω) and an elevated inductance. The high inductance figure will reduce the

cut-off frequency of the low-pass filter, thereby providing better decoupling at lower frequencies.

Figure 3 Schematics of the low-pass filters

3.3 Oscillator

Infineon’s XENSIV™BGT60ATR24C radar sensor requires an external 80 MHz oscillator with low phase jitter and

low phase noise to provide a stable system reference clock. Therefore, the BGT60ATR24C shield employs an

NDK NZ2520SHA quartz oscillator, as depicted in Figure 4. This oscillator source will output a stable 1.8 V digital

signal. The most important parameters when choosing an oscillator are phase jitter and phase noise. Other

oscillators should have similar phase jitter and phase noise to the NDK NZ2520SHA. The R6 series resistor

reduces the RF level at the sensor so that it is at the optimal range for the BGT60ATR24C. If a redesign of the

board contains a different signal source or a vastly different layout is implemented, the value of R1 (150 Ω) may

have to be adjusted. A higher resistance results in a lower signal at the radar sensor. If the signal level is too

low, the phase noise of the sensor will degrade. With a low resistance, the signal level at the sensor will be

heightened. Consequently, in the range-Doppler illustration of the radar data, a peak (or ghost target) will

appear for low distances.

Figure 4 The oscillator circuit on the BGT60ATR24C shield

For this reason, the phase noise needs to be measured as well as the radar data. This can be illustrated with a

range-Doppler plot to optimize the series resistance of the layout. The series resistance must be varied by

soldering different resistors into the circuit. An optimized series resistance will show ideal phase noise behavior

of the sensor, paired with a clean range-Doppler plot. If the phase noise behavior is non-ideal, the resistance

value must be lower. If a peak appears in the range-Doppler plot, the resistance must be higher.

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

Hardware description

3.4 Connectors

The BGT60ATR24C shield is an extension board of Infineon’s XENSIV™60 GHz radar system platform (without a

microcontroller included). The shield must be connected to a microcontroller board, like the Radar Baseboard

MCU7.

The main connector interface of the BGT60ATR24C shield contains two Hirose DF40C-20DP-0.4V connectors. On

the microcontroller side, the Radar Baseboard MCU7 contains the corresponding DF40HC(3.5)-20DS-0.4V(51)

connectors on its bottom side. Figure 5 describes the pin-out and the pad layout of the Hirose connectors on

the BGT60ATR24C shield. To provide the information of the correct digital signal level to the host board, the

line Vdigital is shorted with the 1.8 V supply. The RF shield and the MCU7 board have to be properly aligned, as

depicted in Figure 1.

There is a risk of the Hirose connectors wearing out when regularly plugged into and unplugged from the

shield. To prevent this, it is recommended not to lift the board out of the connector on the short side. Instead,

simply pull on the long side of the board, thereby tilting the short side. This will significantly increase the

operational lifetime of the connectors.

Figure 5 Pin-out of the sensor connectors on the BGT60ATR24C shield

3.5 EEPROM

The BGT60ATR24C shield contains an EEPROM memory to store data such as the board identifier. Its

connections can be seen in Figure 6.

Figure 6 Schematics of the EEPROM

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

Hardware description

3.6 Layer stackup

Since the antennas are integrated on the PCB, the stackup must be chosen carefully. For low loss and enhanced

performance, the stackup shown in Figure 7 is selected. All the vias in Figure 7 are mechanically drilled except

for the blind vias between L1_Top and L2_GND, which are laser drilled.

Note: IS400 is similar to FR4 material

Figure 7 Layer stackup and via types

3.7 Metal layers overview

Figure 8 through to Figure 12 show the different metal layers of the PCB. Layer 1 comprises SMD components,

the BGT60ATR24C chipset and matching networks. Layer 2 consists of the ground plane for RF structures

situated on Layer 1. Layer 3 consists of signal lines and power planes with the voltage domains required for

BGT60ATR24C and other components. Layer 4 is the ground plane for the antennas that are placed on layer 5.

Figure 8 Layer 1 –RF layer, component side

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

Hardware description

Figure 9 Layer 2 –GND plane for component side

Figure 10 Layer 3 –signal/power layer

Figure 11 Layer 4 –GND plane for antenna side

Figure 12 Layer 5 –RF layer, antenna side

Application note

Revision 1.10

2023-02-14

BGT60ATR24C ES shield

XENSIV™60 GHz radar system platform

Layout overview

4Layout overview

4.1 Component side

Layer 1 is the component side. It comprises important elements for the RF performance of the shield.

•BGT60ATR24C radar chip

•TX matching structures

•RX matching structures

•Lines to the feed-throughs to the antenna side

The matching structures transform BGT60ATR24C’s chip impedances at the package side into 50 . The

transmission lines to the feed-throughs correct for phase differences between the channels (see section 5.1) so

that all RX channels and TX channels are in phase at the antenna side.

In order to work correctly, all these RF structures on the component side need a certain distance between the

board and the other objects. Simulation has shown that this distance should be more than 1.8 mm. This is the

reason why the shield should be plugged into the MCU7 board at the side with the higher connectors.

The copper areas between the matching structures and transmission lines, as well as the vias next to them, will

help to increase the isolation between the single RX and TX channels.

The solder mask was removed in all RF relevant areas of the board, as otherwise it would degrade the RF

performance.

BGT60ATR24C TX matching structuresRX matchingstructures

TX feed-through

RX feed-through

Figure 13 Top layer overview, component side

4.2 Antenna side

The antenna side consists of the six different antennas. The structures between the TX and RX side will increase

the TX to RX isolation. The structures around the single sides prevent radiation in unwanted directions.

There is no solder mask on the antenna side, again in order to improve RF performance.

The single TX and RX antennas are placed in such a way that the board, if MIMO techniques are being used, has

multiple virtual antennas - three for horizontal scanning, and four for vertical scanning. Figure 16 explains the

principle behind this.

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