TRAPATT Diode: Advantages and Disadvantages

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.

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.

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.