Skip to content

How do Microwave Motion Sensors Work

Everyone endeavors to secure their property – and you are not any different, especially for your home. It is common to find a security system here, a padlock there, and for the more astute, motion sensors. However, it can get a little murky trying to find the best motion sensor for the latter. So how then can you go about it?

First, motion sensors come in diverse types, though all with the same application of improving your home’s security. Of course, you can always get infra-red motion detectors or photosensors. However, the most straightforward – microwave motion sensor uses microwave or radar technology in detailing an intruder’s location within your house. So what do you need to know about microwave motion sensors before making your motion sensor decision?

What does a Microwave Motion Sensor Entail?

A microwave motion sensor is a simple gadget instrumental for your home security system. It utilizes electromagnetic radiation and emits waves that get reflected in your receiver. Electromagnetic waves or radiations comprise oscillating magnetic and electric fields that proliferate at very high speeds (comparable to light). The receiver acts as an analyzer of the bounced back waves. For example, a typical object moving across the room will alter the waves. The receiver will then identify such alterations whenever they happen.

For a microwave motion sensor to work, it must have a corresponding motion detector. The detectors become useful in measuring the time the signal takes to reflect onto the sensor. Such a period gets inferred as the echo time. It is instrumental in calculating the in-between distances of all stationary objects located in the detection zone. The echo time acts as the baseline upon which the system functions.  

Typically, the microwave motion sensor’s mode of action implies that it can either prove less or more sensitive. Therefore, you can calibrate the MMS to spot tiny changes or more elaborate movements of larger objects to avert false positives.  

Types of Microwave Sensors

The properties of electromagnetic radiation or waves imply that their corresponding sensors can get classified into different types. Some important properties include wavelength or frequency, strength or intensity, and polarization. Frequency implies the change rate of the electromagnetic wave’s amplitude. It is also related to the light’s wavelength or speed.

On the other hand, the intensity comes as the measure of the electromagnetic wave or radiation’s amplitude and correlates to the energy that the wave carries. Remember, the magnetic and electric fields in the electromagnetic wave come as vector quantities. As such, they have both a direction and a magnitude.

The electric field’s direction lies perpendicular to the propagation’s direction and often defines the wave’s polarization. It can have either a linear or circular polarization. Because of the vector nature of the radiation, you find an electromagnetic wave proving sensitive to the orientation of the object it scatters from. It thus gives extra details about the morphology of the surface.   

Passive Microwave Sensors

All microwave sensors operate within the electromagnetic frequency range of 0.3-40 GHz. In addition, a passive microwave sensor detects natural microwave radiations that a surface produces.

Active Microwave Sensors

It involves microwave motion sensors that emit microwaves before detecting the reflected microwaves from the object of interest under observation.

Classes of Microwave Motion Sensors

best microwave motion sensor

Microwave motion sensors come in diverse types that generally fall under the following classes. It includes the pulsed radar type, frequency-modulated, continuous-wave or FM-CW radars, Doppler-effect radars, and UWB systems. Other classes entail transmitter-receiver systems, resonator sensors, modulated targets, impedance meters, and radiometers.

Most of the microwave motion sensor classes utilize a transmitter or a signal generator and a receiver save for the radiometers. However, the distinguishing factor between the classes arises from the signal modulation type and the system’s design. Additionally, some microwave motion sensors can work when placed at a distance from the object, while others function while mechanically joined with the object.

Features of a Microwave Motion Sensor

Intrinsically Safe: Microwave motion sensors cannot generate sparks, especially from electrostatic discharge or friction.

No Contact: It can operate without establishing any contact with the object. Additionally, the microwave sensor can also successfully penetrate nonmetallic exteriors.    

Rugged: Microwave sensors possess no moving components or parts and thus prove reliable. It is especially true in comprehensive military applications.

Long-range: microwave motion sensors can detect objects located from distances spanning 25mm to 45000mm or more. However, this depends on the size, antenna design, and microwave availability.

Environmental reliability: in most cases, you will find microwave sensors operating from a -55A °c to a 125A°c in dirty, dusty, polluted, and gusty poisonous areas.

The microwave sensor’s size: As technology develops, advances in microwave circuits have allowed the ultimate package to become smaller and cost less. The package often contains the transmission source, transceiver or signal processing receiver, and the focusing antenna.  

Factors that Determine the Frequency of Microwave Motion Sensors

Your choice of a microwave motion sensor concerning frequency needs to get determined by various factors. It encompasses your intended application, power constraints, platform, and the availability of the desired spectrum at the preferred frequency range. For instance, you will get the following frequency bands within the stipulated wavelengths.

Wavelength Range (CM)Frequency Band (MHz)
1.13 – 0.7526,500 – 40,000
1.66 – 1.1318,000 – 26,500
2.4 – 1.6612,500 – 18,000
3.75 – 2.48,000 – 12,500
7.5 – 3.754,000 – 8,000
15 – 7.52,000 – 4,000
30 – 151,000 – 2,000
100 – 33300 – 900

What Can a Microwave Motion Sensor Do?

You must think by now that a microwave motion sensor only detects motion through wave disruptions. However, the functional enhancements presently available on it will not only surprise you but convince you of its efficiency in securing not only your property but other advanced operations. For instance, the advanced microwave motion sensors can also sense motion towards a random motion or a motion moving away from it. Such a differentiation of motion becomes helpful in detecting normal movement from that of an intruder. Moreover, it is a feature that makes a microwave motion sensor highly reliable.

Microwave motion sensors also come as a safe product for use. You can use them outside or within your household or property. Further, you can place the sensors across a large area besides configuring them to sense or detect diverse activity types. For example, you can configure the sensor to ignore specific activities in specific areas of your property, like the kids or pet areas.

The Arduino Doppler Radar

For newbies, the term doppler radar can prove sophisticated and confusing. However, it has the same meaning as that of a microwave sensor. The Doppler radar is sensitive and reflects microwaves from objects within the detection area but devoid of any temperature disturbance. In most instances, you will find doppler radars as one of three types: the planar microstrip, coaxial, and wave-guide microwave sensors.

Doppler radars bounce microwave signals off the anticipated target and analyze the object motion’s effect in altering the returned signal’s frequency. Therefore, the target’s velocity can also get measured based on the received variation against the radar. In summary, you will find microwave motion sensors using microwave technology. It, in turn, gets classified into motion sensing, velocity sensing, presence sensing, and sensing of the motion direction. Another crucial category includes range sensing.

You will possibly find doppler radars in applications such as meteorology, aviation, healthcare, military, and radar guns. But to make your own Arduino doppler radar, consider the following section.

Making an Arduino Doppler Radar

By now, you know that any microwave motion sensor must have a microwave transmitter, a receiver, and most times a related circuit or alarm. However, you must use some crucial components to develop the three. Critical components entailed in building a functional Arduino Doppler Radar entail the Arduino Nano, jumper wires, breadboard, character LCD, LED, character LCD, Buzzer, resistor, etc. It never ends here as the hardware components must get controlled via a software system.

Follow the following steps once you have assembled all the necessary components required to build a functional Arduino Doppler Radar.

Wire the hardware up by connecting the Arduino, the RCWL, character LCD, the Led, and the buzzer in the prescribed sequence. It mostly involves LED and Content with Arduino PINs of 2 and 3, respectively. Arduino analog IO of A5 and A4 with SDA and SCL character LCD. The Arduino Nano encompasses the GND, 5V, and D2, while the RCWL encompasses the GND, VIN, OUT.

It is crucial to note that the Pin 3V3 located on the RCWL comes as the output pin. Additionally, the CDS pin allows you to incorporate an LDR into the breadboard. Such a light-dependent resistor will allow you to operate the system in low-power mode. Consequently, it will (sensor) can solely activate in darkness.

You must double-check all the connections before uploading the software’s source code.    

The Working Process of a Microwave Motion Sensor

For a microwave motion sensor to work, it needs all the components necessary for its proper function (transceiver, sensor, etc.) In addition, the sensors need a narrow beam and a high-gain antenna to reflect the energy to the module. However, the amount of energy will depend on the shape and composition of the object of interest.  

Operational Principles

The sensor module gets developed through the Doppler radar principle. Further, the sensor module’s role encompasses the transmission of a low-power microwave from the transmitting antenna besides receiving the microwave energy reflected by objects to the receiving antenna.

When the object’s movement is detected, the reflected frequency (microwave) gets shifted from the transmit bandwidth or frequency to the receiving antenna. The shifted and reflected microwave frequency gets mixed with the microwave frequency transmit and results in a low-frequency voltage at the sensor’s output.

Detection Factors

In almost every incidence, six probable factors affect the Pd or the probability of detection in volumetric sensors – though at varying degrees. It includes the pattern and amount of energy emitted, the size of the objects, the object’s distance, speed, the direction of the movement, and the absorption or reflection features of the waves (environment or the intruder)

It is beneficial to have a more defined energy pattern in theoretical terms. Similarly, if the intruder or the moving object proves larger, you also get a higher detection probability. In the same way, the shorter the sensor distance to the object or intruder, the quicker the intruder’s movement, the higher the detection probability. Additionally, a lateral and fast movement typically has a higher detection probability than a straight and slow movement.        

Upon returning the reflected energy to the transceiver, your mixer diode combines this energy with the transmitted signal. But remember, the target either moves towards or away from the module, which implies that the phase relationships between the two will change. As a result, the signal emanating from the mixer will prove audio frequency and also proportional to the target’s speed. The phenomenon gets inferred as the Doppler frequency.

Further, microwave motion sensors or detectors must be combined with PIR technology to limit false alarms. In most instances, you will come across the tech combination as a dual technology detection approach.

Prices of Microwave Motion Sensors

If you want to get a quality and efficient microwave motion sensor, you must consider different aspects. Firstly, understand the functionality of the microwave motion sensor, the different types available, and the cons and pros of each system. Additionally, it would help if you considered the available manufacturers and their reputations. Finally, but most importantly, the price vis-à-vis the quality of the Doppler Radar needs to guide your decision-making.

However, the general microwave motion sensor price range of microwave motion sensors begins from $ 0.8 to about $52.5. however, the specific range depends on the minimum order quantity the seller offers besides the type of microwave sensor. Further, wholesale prices will always prove cost-effective though this often needs a large order – otherwise not feasible for most end users.

Factors that Influence the Microwave Motion Sensor Price

microwave motion sensor range

The Brand of the Manufacturing Company

Microwave motion sensors will always come under different brand names and product lines. It implies that each will have distinct features depending on the manufacturer and product line. Such often indicate their differential quality, which then influences the microwave motion sensor price. Other price determinants of microwave motion sensors attributable to the manufacturer include the reputation of the brand or manufacturer (industry experience), size of the manufacturer, location of the manufacturing plant, and the type of microwave motion sensor. For instance, RayMing PCB and Assembly has a demonstrated history of over fifteen years in manufacturing and assembly of printed circuit boards crucial for sensor devices. Its production plant in diverse areas over the globe also makes it suitable for the global clientele.

Further, bigger companies with excellent reputations have established supplier relationships. Such relationships lead to discounts on raw materials and reduce the cost of production. What’s more? The company easily takes advantage of the affordable production costs (quality and affordable labor in China, raw materials, world-class technology and infrastructure, etc.) As such, you will not only trust the world-class products and services offered but enjoy incomparable prices with competitor companies within the industry. The result of all this entails getting high-quality microwave sensors and allied components at relatively affordable prices.

Finally, the type of microwave under a specific brand name will either drive the cost of the sensor up or down. For instance, experimental active microwave sensors will cost higher than passive microwave sensors regardless of the brand.

The proximity of the Manufacturing Company

Once the fabrication of the different components of a microwave motion sensor gets completed, assembly and distribution ensue. The latter part can drive the cost of the final product owing to shipping, especially when they have to get transported for longer distances. It is thus advisable to always go for a manufacturer or decent brand located near you.

Application Areas of a Microwave Motion Sensor

Different microwave motion sensor exists for diverse applications—the diversity in application demands different capabilities of the sensors. For example, a microwave motion sensor for home security will not have the same capacity as one used for geospatial studies. One will rely on passive microwave technology while others will entirely depend on active microwave technology. Size also plays a crucial role here as different applications prefer specific sizes. The smaller the microwave motion sensor, the less material it uses and hence lowers the cost of material in production.

Here are some of the Applications

Medicine and Physical Wellbeing. Microwave motion detectors find application in detecting patients’ breathing rates and heartbeats in hospitals.

Monitoring your Building Lighting System

You can also use a doppler radar for monitoring your light system in the house or office. It is a common feature in elevator shaft-ways besides your property’s security. You will also find it getting used in enforcing traffic rules and regulations.

Microwave motion technology not only applies in the traffic arena but also industry. For instance, you will find microwave technology in measuring the speed in vehicles, automated doors, automation lights, reversing radar, alarm systems, etc.

Another crucial application area for the microwave motion sensor entails securing areas like banks, museums, military installations or warehouses, prisons, transformer substations, etc. however, for such applications, the microwave technology needs to get combined with the PIR motion detectors. Such a combination of technologies for motion sensors enhances reliability and performance.

How Can You Benefit from a Microwave Motion Sensor?

  • A universal truth about microwave motion sensors entails using them in almost any environment. You can use it in most environments; especially those many can deem unhospitable for sensors. For instance, you can comfortably use it in high-heat environments that can fry photo-electric sensors. The MMS ranks as among the versatile sensor system types available in the market.
  • A microwave motion detector can also go through holes and walls. Therefore, it implies that you can use it to cover larger areas of your home or property, including your large outdoor area. If you, therefore, have a large area to secure, then this microwave motion sensor can prove the best option for your motion detection.
  • You can program a microwave motion sensor to limit the volume or number of false alarms devoid of minimizing correct positives. Consequently, you get to enhance your motion sensor’s ease of use and accuracy. Further, you comparatively spend less to buy a microwave motion detector compared to other motion detector types. It is, however, imperative to understand that running them can become more expensive.
  • A microwave motion sensor also covers a 360 degree-wide scope compared to other systems like the PIR, which only covers a 90 degree-wide scope.

Drawbacks of a Microwave Motion Detector

  • A major challenge you will most likely experience with a microwave motion detector entails the countless false alarms that may occur from slight object vibrations. It can include swinging signs, curtains, etc. Further, a microwave motion detector operates in intervals and not continuously. Because of this, it increases the probability of any intrusion.

However, the enhanced detector combats this challenge by having every component of a typical sensor besides two mixer/receiver diodes. Additionally, some sensors possess diodes that enable the sensing of the intruder’s direction to the detector.

  • Microwave beams have special properties that enable them to permeate almost any type of surface (around the detection shield). However, for metallic surfaces, this never proves the case. Therefore, the sensor can detect a motion in undesirable detection areas and fail to detect motion where it proves desirable. Further, metallic objects act as shields that create dead zones or shadows behind them. It is in such areas that the sensor fails to detect any motion.

Microwave motion sensors also have the predictable ability of sensing motion behind walls because of their beam. As such, it will not discriminate the motion even if it proves typical because of the sensitivity of the sensors to motion. It can always become a challenge in a home setup, especially with false alarms.

Final Thoughts?

The specter of microwave motion sensors in terms of their capability and related costs makes it an ideal fit for your domestic or commercial use. You can not only enhance the security of your premises or household with such powerful security tools but use them for other investigative, security, and explorative ventures. However, understanding what a microwave motion sensor entails, how it functions, the different types, and possible application areas will effectively kickstart your journey. Hopefully, at this juncture, you have managed to answer some of the pertinent questions you had about microwave motion sensors. You also understand where and what price range you can secure your microwave motion sensor.