Terminology » Microwave Devices » TRAPATT Diode: Advantages and Disadvantages

TRAPATT Diode: Advantages and Disadvantages

trapatt diode microwave device semiconductor oscillator radar system

This page explores the pros and cons of TRAPATT diodes. We’ll delve into their benefits and drawbacks to give you a comprehensive understanding.

What is a TRAPATT Diode?

In short, a TRAPATT (TRApped Plasma Avalanche Triggered Transit) diode is a microwave energy source used as both an amplifier and an oscillator. It’s a type of semiconductor diode that operates efficiently below frequencies of 10 GHz. One key characteristic is that it requires a greater voltage swing for its operation.

TRAPATT diode structure

Figure 1: TRAPATT diode structure

The structure of a TRAPATT diode, as shown in Figure 1, typically consists of a p+ - n - n+ (or n+ - p - p+) configuration. The n-type depletion region has a width ranging from 2.5 to 12.5 µm, while the diode diameter spans from 50 to 750 µm. These diodes are commonly manufactured using silicon, and the p+ region is kept very thin, usually between 2.5 and 7.5 µm.

TRAPATT diode waveforms

Figure 2: TRAPATT diode waveforms

Figure 2 illustrates TRAPATT diode waveforms, showing its operation at various points. You might also be interested in a comparison of BARITT, IMPATT, and TRAPATT diodes.

Applications of TRAPATT Diodes

TRAPATT diodes find use in a variety of applications, including:

  • Microwave beacons
  • Local oscillators in Radar systems
  • ILS (Instrument Landing System)
  • S-Band pulsed transmitters for phased array radar
  • Radio altimeters

Advantages of TRAPATT Diodes

Here are the key benefits of using TRAPATT diodes:

  • Higher Efficiency: They offer significantly higher efficiency compared to IMPATT diodes, achieving efficiencies of around 15 to 40%.
  • Low Power Dissipation: TRAPATT diodes dissipate very little power.
  • Suitable for Pulsed Operation: They are particularly well-suited for pulsed operation scenarios.
  • Wide Frequency Range: They can operate across a frequency range of approximately 3 to 50 GHz.

Disadvantages of TRAPATT Diodes

While offering several advantages, TRAPATT diodes also have some drawbacks:

  • Not Ideal for Continuous Operation: They are not typically used for continuous operation due to high power densities, ranging from 10 to 102 W/m2.
  • High Noise Figure: TRAPATT diodes exhibit a very high noise figure, around 60 dB.
  • Frequency Limitations: They are typically limited to frequencies below the millimeter wave band.