Microwave Sensor or a Doppler Sensor Circuit

In this article we study the microwave sensor IC KMY 24 and try to understand its main features and its pinout implementation details.

How Doppler Sensor KMY24 Works

The KMY24 microwave sensor module is designed and built on the concept of Doppler effect. When correctly configured it radiates a low power microwave signal of around 2.45 GHz across the directed zone.

When an object (target) that could be even a human being, comes in the range of the emitted signal, the signals get reflected back to the sensor module with some disturbance relative to the original frequency, this is popularly known as the Doppler shift.

Once this reflected frequency shift is detected by the sensor, the in built circuitry instantly mixes the reflected frequency with the existing original frequency and produces two individual frequencies across its specified outputs.

What’s Doppler Effect

As per the principles of Doppler effect this frequency phase shift could be either positive or negative depending upon whether the object in the sensor zone was receding or approaching the sensor.

The function of the KMY24 concludes here, and the outputs from the device now needs to be amplified through suitable voltage amplifier configuration, for example through an differential opamp amplifier circuit etc.

Further on the opamp output may be appropriately terminated with a relay stage or a recorder or an alarm for distinguishing or identifying the sensed parameters.

Technical Features of the IC

The main features of the IC KMY24 may be learned as follows:

• High sensitivity and detection even when a relatively smaller target approaches the zone.
• Twin mixer circuitry for enabling directional movement detection of the target
• High reliability for achieving fool proof results
• Meager power consumption making it perfectly suitable for battery operated applications.
• Minimal harmonic emission for reduced RF disturbance in the atmosphere.
• Compact size.

The following image shows the pinout details of the KMY 24 microwave sensor

Pinout Detail of the Microwave Sensor IC

The next image provides the breakdown parameters or the absolute maximum voltage and current ratings that must be applied to the IC, these parameters must not be exceeded, to be precise these must be kept well below the shown values.

Maximum Electrical Tolerance Specs

The two images shown below depict the phase shift or the difference in the position of the reflected frequency relative to the original radiated frequency when the target is approaching (first image below), and when the target is receding or going back (the second diagram below).

Analyzing Phase Shift Difference

In the next (upcoming) article we'll try to understand regarding how to use a microwave sensor through a practical circuit.