PCB Blog - Automation of Millimeter Wave Radar Sensing

The MMW radar IoT human perception scheme optimizes the design for indoor scenes, solves the interference problem of radar in indoor use through a unique algorithm, and has broad application scenarios in various IoT schemes such as smart office and smart lighting.

Millimeter wave radar human perception can also be installed in the conference area to achieve intelligent management in combination with the conference reservation system.

For example, in the conference room reservation scenario, if the sensing radar installed in the conference room does not detect that the meeting personnel enter the conference room within the preset time, the conference room resources can be automatically released, thus ensuring the efficient utilization of conference room resources.

The intelligent human breath presence sensor realizes the static human body monitoring. Using millimeter wave radar technology, select appropriate ISM radar frequency bands according to different environmental characteristics (space size, environmental complexity).

In order to better meet the customization needs of customers in diverse scenarios, the equipment's sensitivity, delay and distance can be adjusted through APP or dialing, thus greatly improving the adaptability of the product to the environment and achieving seamless connection with the depth of the application scenarios. It supports photosensitive detection (not enabled by default), automatically detects day and night, and automatically activates to enter the radar sensing mode when the day is dark and the night is dark. It can be well applied to inductive lamps and security alarm devices, such as corridors, corridors, garages, balconies, etc. It can also be used as energy-saving switching devices. In terms of interface, smart radar human presence sensor provides diversified interfaces including dry contact, strong current, PLC, 485, and communication methods can also support graffiti/private cloud/LORA/NB and other mainstream communication methods. The sensing sensitivity (sensing distance), sensing time and light control illuminance can be adjusted and controlled, and the sensing range is more accurate. In the future, it will be widely used in smart home, Internet of Things, intelligent lighting and other fields.

Engineers and architects who design new office buildings and factories are increasingly looking for improved sensors to achieve various energy-saving safety and security functions. These sensors are used to detect the movement and position of people in office buildings and robots or other machines in factories. In the early design, a variety of sensor types were used and some success was achieved, but the designers have just discovered the millimeter wave (mmWave) sensor. Low cost millimeter wave single chip radar can act as a sensor and provide many advantages that other sensors cannot provide. With the construction and/or transformation of new buildings and factories, millimeter wave sensors can add improvements and new functions that were previously impossible.

The main value of detection and tracking personnel is energy saving. In buildings with many workers, the location and density of personnel vary greatly over time. It is meaningful to adjust heating, air conditioning and lighting according to the occupancy of people. If someone is present, the best amount of heating or cooling and lighting can be provided to maintain productivity. If no one is present, cooling and heating can be greatly reduced and lighting can be turned off, thus saving a lot of energy.

The security system can also be enhanced through automatic monitoring. Personnel location, counting and tracking are the basic data required to protect certain spaces and ensure the control of doors and gates to comply with the required security protocols.

Security is another use of proximity detection, especially in factories where mobile robots and other machinery may pose a threat to humans. Motion sensing with appropriate warnings can significantly reduce accidents. Other applications include traffic monitoring at intersections and parking lots, and liquid or solid level sensing in tanks.The success of all these applications depends on the reliability and accuracy of personnel detection and tracking. Millimeter wave sensors can provide this.

Sensor surveys provide the best heating, air conditioning, and lighting for office buildings or factories, saving significant operating budgets. For example, if there is no one in the room, changing the temperature and turning off the lights can significantly save energy. Energy Star points out that, if the existence of personnel is not considered, the average commercial building will waste 30% of its energy consumption. The key to reducing costs is to provide appropriate environmental conditions at the right time.

Building and factory automation systems rely on all types of sensors to monitor a wide range of physical properties. Some examples include temperature, humidity, and ambient light sensors, and smoke detectors. Other sensors are magnetic detectors for door and window monitoring and detectors for carbon monoxide and other toxic gases or dust and pollen. All these sensors send signals as feedback to the central control system that operates the heating and air conditioning (HVAC) and lighting systems. Proper temperature and lighting conditions can improve employee comfort and productivity.

The key factor is the monitoring process, which determines how many people are in the building and where they are. Special sensors are required to detect and count the number of people. Proximity sensors or detectors are used for this purpose.A popular proximity detector is passive infrared (PIR) sensor. It detects body temperature and sends a signal to the controller to take action. The simple PIR detector in Figure 1 has a single wide coverage area and has no discrimination except for coarse motion. More complex infrared detectors use multiple infrared lasers or LEDs to illuminate an area to create a 3D scene that can be captured by the infrared detector. Then analyze the digital scene in the software to determine the number of people.Basic passive infrared detectors cover a large area but cannot distinguish details.

Similar options can be used for ultrasonic sensors or cameras. The ultrasonic detector plots the area with high-frequency sound in the range of 40-kHz to 80-kHz, and recovers the reflection that can be analyzed in the software for personnel detection. Cameras are becoming more and more common, and machine vision software can be used to perform similar functions, but there are privacy issues.

A typical business space, such as a conference room, can be covered by a radar sensor, and the number of people on the table can be accurately calculated.

One type of radar equipment is the frequency modulated continuous wave (FMCW) type operating in the range of 76-GHz to 81-GHz. The best way to consider a single chip radar system is to consider it as another type of sensor. Facts have proved that millimeter wave radar is excellent in object proximity detection, motion sensing and measuring the distance to the detected object.

Recall that radar is used to measure distance, direction (angle) and speed. Police speed radar and baseball speed gun are good examples. The transmitter on chip (TX) transmits signals and then reverses them from a remote object.

A simplified radar transceiver is shown. The frequency of the return signal is mixed with the transmission frequency at the receiver (RX) to produce a digitized intermediate frequency (IF). Using these data with the on-chip processor can measure the transmission time and calculate the distance when the radio wave speed is known. The position and angle (azimuth) can also be detected by using a highly oriented antenna. FM radar also allows you to measure movement and speed. The result is a very flexible and programmable sensor that can produce very accurate personnel sensing equipment. Millimeter wave radar sensor is optimized for indoor complex environment, supports networking deployment, can accurately detect human existence, and can be applied to building automation, air conditioning and lighting control in the field of intelligent buildings. The frequency of millimeter wave radar induction signal is more accurate, more stable, and lower in cost. It has a good use effect in smart homes, such as smart lighting. 

Compared with other proximity sensors, radar has some main advantages:

They saw it in the dark, but the camera didn't. They are not affected by smoke or dust in the air or bright sunlight.

Their high frequency provides higher accuracy in resolving closely spaced objects. They can determine the position and direction of movement. Multiple antennas form a phased array through beamforming to help improve the accuracy of population statistics.

They measure the fineness of motion and speed. The test of PIR sensor and millimeter wave sensor proves that the radar sensor can capture fine movements such as human respiration.

They can detect people and movement through the walls. Tests have shown that radar sensors can easily penetrate gypsum boards or plastic walls and provide accurate counting. However, two layers of dry walls or plywood do greatly weaken the radar signal, making detection difficult.

Although millimeter wave radar sensors perform well in human statistics, remember that most of the credit for detecting and recognizing objects goes to the processing software. To get the best results, complex algorithms and DSP microcontrollers are required.

Millimeter wave radar sensor is optimized for indoor complex environment, supports networking deployment, can accurately detect human existence, and can be applied to building automation, air conditioning and lighting control in the field of intelligent buildings. The frequency of millimeter wave radar induction signal is more accurate, more stable, and lower in cost. It has a good use effect in smart homes, such as smart lighting.