A radio wave sensor is not always used in an environment that is suitable or convenient for the sensor itself. When installed outdoors, it will be frequently exposed to dirt, dust, heavy rain, fog and other adverse conditions. The sensor or target themselves may get soiled by mud or other contaminants.

Conventionally, most sensors used infrared or ultrasonic waves but these sensors had the drawback of degraded performance or unstable operation if subjected to radical temperature fluctuations or if the sensor surface becomes dirty. To solve this problem, OMRON focused on radio waves, which are invulnerable to various adverse conditions.

A specific frequency is assigned to each TV/radio broadcaster or mobile phone. In these cases, interference of waves at other frequencies is kept to a minimum. Transmitting and receiving only at a pre-determined frequency, however, demands exceptional accuracy, which in turn makes the equipment very costly. To reduce costs, OMRON's radio wave sensors are designed to use a range of frequencies, instead of being limited to a single one. This, however, means that the sensor is more frequently exposed to interfering waves from TVs, mobile phones, portable wireless equipment, etc. Therefore, developing effective measures to overcome interference problems was instrumental in OMRON's development of radio wave sensors.

If a pulse echo is affected by interfering waves, the waveform of the pulse will become distorted or intermittent, which in turn makes accurate detection of information difficult. This is unavoidable in today's world where we are constantly surrounded by many different radio waves. During the course of development and repeated prototyping, the early prototypes could not avoid malfunctioning when a mobile phone was placed within the room. After much trial and experience, however, OMRON succeeded in completing a sensor capable of providing high sensing performance and accuracy even when interfering waves from devices such as mobile phones were as close as several centimeters.

As discussed earlier, the distance to a person can be determined by measuring the time it takes for a radio wave transmitted from the sensor to return after hitting the person. From a distance, the person's position can also be detected, along with body movements such as approaching or reaching for the door. Once various situations are factored in, it will even become possible to deduce the intention or meaning of a person's particular motion, such as whether that person wants to open the door, or is attempting to break open the door. With the ability to understand human behavior, and by incorporating increasingly higher-performance functions, the sensor of the future will be able to comprehend the meaning of a complex sequence of gestures. In this way, a sensor-embedded system will be able to fulfill the desire and wishes of people to an extremely sophisticated degree.

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