RF Power Sensor Types: Selection Guide, Benefits & Manufacturers

RF power sensors play a crucial role in measuring signal strength within wireless systems. Selecting the right sensor involves careful consideration of key parameters such as frequency range, accuracy, and power handling capabilities.

Prominent manufacturers of RF Power Sensors include Boonton, Keysight, Anritsu, NI (National Instruments), Rohde & Schwarz (R&S), and Mini-Circuits. The advancement of wireless technologies and the increasing use of complex modulation schemes have made it essential to accurately measure the power output of transmitting devices.

Various instruments are employed for power measurement, including power meters, spectrum analyzers, and scalar/vector network analyzers. All these instruments rely on power sensors to measure average or peak power levels.

RF Power Sensor Types

RF Power sensors are classified based on their underlying measurement principles:

• Bolometer or Thermistor Sensor
• Thermocouple Sensor
• Diode Sensor

Thermistor Sensor

This sensor type utilizes a Wheatstone bridge design, with a thermistor as one of the arm elements. When RF energy is applied to the thermistor, its temperature changes, resulting in a change in its resistance.

To maintain balance in the bridge, a feedback loop adjusts the DC power. The change in DC power is directly proportional to the applied microwave power. This sensor type offers excellent linearity but has the lowest dynamic range.

Thermocouple Sensor

This sensor leverages the Thomson effect and Peltier effect for power measurement. It offers very accurate power readings. The thermocouple sensor measures RMS (Root Mean Square) power, which is independent of the modulation technique. This enables average power measurement for different types of signals. However, it’s the slowest measurement device due to its settling time.

Diode Sensor

In this sensor type, the power to be measured is applied to a load resistor connected in series with a diode and in parallel with a capacitor. As the applied power increases, the diode controls the current or voltage across the capacitor. This is then read and converted into a suitable power measurement.

Selection Guide

When selecting an RF Power Sensor, consider the following specifications:

• Power sensor measurement technology used
• Frequency range
• CW (Continuous Wave) dynamic range
• SWR (Standing Wave Ratio)
• Rise time
• Sensor linearity
• RF connectors used

Advantages of RF Power Sensor

The use of power sensors in RF design, development, and testing offers several benefits:

1. Accurate Power Measurement: Provides precise power readings for reliable analysis.
2. Broad Frequency Range Support: Operates across a wide range of frequencies, accommodating various applications.
3. Higher Sensitivity & Dynamic Range: Detects even small power variations with a wide range of measurable power levels.
4. Fast Response Time: Enables quick and efficient measurements, reducing testing time.
5. Compact & Portable Design: Available in USB or handheld formats for convenient use in various environments.

RF Power Sensor Manufacturers

The following table lists popular manufacturers of RF Power sensors:

Conclusion

A precise RF power sensor enhances overall system performance. Selecting the right sensor from leading manufacturers ensures accurate power measurement solutions for diverse applications.