The What, How and Why of RF Sensors


RF Power sensor circuit diagram | Ranatec

RF and microwave power meters are used in various areas of RF design and development, test, service repair and field service. RF power meters are available in different types such as in-line, absorptive, etc. Most of these types come with an RF sensor which is used to measure the RF power. The type of sensor that would be used for measuring the power usually depends upon the type of signal that needs to be measured.

For instance, a few types of sensors are suitable for measuring low powers, while others are applicable for modulation techniques. The following points give you a better understanding of the meaning, working and benefits of power sensors. Keep reading to know more.

What is an RF power sensor?

An RF power meter is an instrument, which can measure the electrical power mostly in the range of 100 MHz to 40 GHz. This meter consists of an RF power sensor that is connected to it via a cable and can display power reading. It is also referred to as a mount that operates by defining a sensitive volume and interrogating the values of the parameters for different materials that invade this volume. This volume can be then defined by a radio frequency antenna, which is tuned into the sensor electronics. 

How does an RF power sensor work?

Just like any other RF material, a power sensor has four electromagnetic parameters such as the real and imaginary of the electrical permittivity and magnetic sustainability. A power sensor operates by defining a sensitive volume and interrogating the value by these electromagnetic parameters. Then, a radio frequency antenna is used to define the sensitive volume, which is tuned into the sensor electronics. 

Types of RF power sensors

There is a large range of sensors that have their own distinctive features, advantages and disadvantages. The usage of a type of the sensor is directly dependent on the type of signal that needs to be measured. A few types are applicable to low powers, while the others are for modulation techniques. Based on these parameters, some of the common types of sensors are as follows:

Diode detector based RF sensors

This type is generally used for analogue power meters. However, this technology can also be used for high-performance power meters. The main advantage of using this type is that it can help measure signals of extremely low levels of power and respond quickly as compared to other types of heat-based varieties.

The main element of RF sensors based on diode detectors is that it uses diode rectifiers in order to produce an output. The RF power sensors using these diodes make it possible for RF power to get dissipated in a load. The detector then rectifies the voltage signal that appears across the load. This ultimately makes it possible to determine the power level entering the load. Diode based electrodes have two benefits. 

  • The first one involves their ability to measure low powers. Some of these diode based RF sensors can measure power levels as less as -70 dBm. This value is quite lower as compared to the measurements done by using heat based sensors
  •  The second benefit of these sensors involves their ability to respond quicker to signals as compared to the heat based ones

Heat-based RF sensors

This type is generally used to dissipate power from a source in a load and then measure the resulting temperature rise. The advantages of these sensors are that they measure the true average power of the heat that is dissipated in the form of a power integral input over time. Simply aids, this power sensor measures the RF power limit of a signal, regardless of its waveform. There mainly are two types of heat based sensors: 

  • Thermistor RF power sensors – These can enable DC power to get substituted so that the system can be properly calibrated. The thermistor power sensors make use of the principle that the rise in temperature can happen due to heat caused by radio frequencies passing through the medium used
  • Thermocouple RF power sensors – The thermocouple power sensors take into account the square-law characteristic. This indicates the input RF power to be proportional to DC output voltage from the thermocouple sensor

Why you should use RF sensors?

Every equipment has some key advantages that define the actual purpose of that device. Listed below are a few advantages of using RF sensors:

  • Do not require any additional components such as magnets, coils, etc
  • Have a high signal-to-noise ratio that you can maximize by optimising the sensor design for a particular application
  • The output is dependent on speed unlike inductive sensors (AZO Materials, RF PROXIMITY SENSORS – CHARACTERISTICS, OPERATION AND APPLICATION IN MATERIALS RECYCLING, n.d.).

Industrial Applications of Power Sensors

Power sensors are most commonly used for microwave-based systems. But, they are not limited to this industry. Whether you are working in telecommunications, Aerospace and Defense, Energy and Utilities, Automotive and similar ones, the sensor technologies can be used in all of these. The uses and functions of these sensors is different and it varies from industry to industry. Companies from different fields need to pay close attention on the specifications of the sensors before investing in one to ensure maximum ROI. 

The operations and benefits of all types of power sensors are different and it depends on individual companies of how and when they want to invest in one. Choosing the right type of RF sensor and using it for the right application can help you get desired results. For more details about the price or specifications of power meters, sensors, etc, contact a reputed retailer.

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