Waveguide Short
Understanding Waveguide Shorts
The waveguide short is the simplest and most accurate waveguide calibration standard. A flat metallic plate across the waveguide aperture provides nearly perfect reflection, making it an ideal reference for VNA calibration.
Waveguide Short Types
- Fixed short: Precision flat plate. Used for calibration. Defines the reference plane for phase measurements.
- Sliding short: Movable short that can be positioned along the waveguide. Used for tuning and impedance matching.
- Contacting: Metal-to-metal contact with waveguide walls. Simple but suffers from contact resistance at high frequency.
- Non-contacting (choke): Uses a choke gap to maintain electrical short without physical contact. Better RF performance at high frequencies.
Frequently Asked Questions
What is a waveguide short?
A waveguide short is a metallic plate that terminates a waveguide with total reflection. It provides a known reference for calibration (|Gamma|=1, phase = 180 degrees). Fixed shorts for cal; sliding shorts for tuning.
Why is a sliding short useful?
A sliding short can be positioned at any point along the waveguide, presenting different impedances at the measurement plane. Used for impedance matching, tuning, and measuring waveguide wavelength (by finding successive minima in a standing wave).
How good is a practical waveguide short?
A well-made waveguide short has return loss < 0.02 dB (|Gamma| > 0.998) across the full waveguide band. It is the most accurate calibration standard because it is simply a flat conducting plate with no critical dimensions.