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Completely Autonomous Radar Sensor for Smart Motion Sensing

In addition, the sensor can be integrated
into systems such as laptops, tablets, TVs,
speakers, and thermostats to “wake” them
up based on motion or direction-of-motion
detection. It can also put devices to sleep or
into auto-lock when no motion is detected
for a defined amount of time to save energy,
increase lifetime, protect privacy, and
enhance the user experience overall.
USER-FRIENDLY AND LOW-POWER CHIP
Figure 4 shows the block diagram of the
BGT60LTR11AIP monolithic microwave
integrated circuit (MMIC). The integrated
voltage-controlled oscillator (VCO) generates
the high-frequency signal, which is stabilized
by a phase-locked loop. Moreover, the trans-
mitter section consists of a medium-power
amplifier with configurable output power. It
can be controlled via the serial peripheral
interface (SPI), while integrated power detec-
tors monitor the transmitted power.
The chip features a low-noise quadrature
receiver stage, wherein the receiver uses a
Figure 2: Infineon’s completely autonomous BGT60LTR11AIP low-noise amplifier in front of a quadrature
homodyne down-conversion mixer, to provide
excellent receiver sensitivity. Derived from
motion and direction-of-motion detectors as away with an 80° field of view. The power the internal VCO signal, an RC poly-phase
well as antennas-in-package (AIP). A state consumption remains below 5 mW because filter generates quadrature local oscillator
machine enables operation of the device of duty-cycling implementation, and it can signals for the quadrature mixer.
without an external microcontroller. Two even be lower than 2 mW in certain settings. The integrated analog baseband units
integrated detectors provide two digital Compared with common radar sensors, consist of a sample-and-hold circuit for
output signals — one indicating motion the BGT60LTR11AIP specifically addresses low-power duty-cycle operation, followed by
and the other indicating the direction of smart-building and smart-home applica- an externally configurable high-pass filter, a
motion (approaching or departing) of a tions. Without great effort, the sensor adds variable-gain amplifier stage, and a low-pass
target. Instead of the usual processing of “smartness” to traditional motion-sensing filter. The digital detectors generate pulses
the radar raw signal, these two signals can applications like lighting systems, automated based on target movements in front of the
be used directly. In this autonomous mode, door opening, or security systems, including radar. For maximum flexibility and robustness
the sensor detects a person up to 5 meters intruder alarms and cameras (Figure 3). against false alarms, the detector circuitry
offers a user-configurable hold time, a hit
counter, and a detection threshold.
Within its two-layer laminate package, the
small, 3.3 × 6.7 × 0.56-mm³ MMIC includes
integrated antennas, eliminating the complex
antenna design at the user end. PCB designs
with this MMIC do not require special base
materials, so customers can use standard
FR4 materials. Figure 5 shows a PCB with
the BGT60LTR11AIP MMIC. The supporting
circuitry on it includes a low-noise voltage
regulator, a crystal oscillator source of
38.4 MHz for the reference clock, and external
capacitors. The output of the sensor is illus-
trated by two LEDs: A green LED lights up
when a target is detected, while the red LED
turns on when a target is moving away from
the sensor and turns off when it is moving
toward the sensor.
This shield demonstrates the features of
the BGT60LTR11AIP MMIC and provides a
complete turnkey radar solution. By con-
necting a power supply to VCC and GND
Figure 3: The BGT60LTR11AIP adds a smart motion-detection feature to many castellated holes, it is possible to “plug” the
smart-home devices. MMIC motion sensor into an existing system.

www.eetimes.eu | FEBRUARY 2021