Tunable Filter
Understanding Tunable Filters
Tunable filters enable wideband systems to select any channel within a wide frequency range using a single filter. This reduces hardware complexity compared to filter banks and enables frequency-agile operation.
Tunable Filter Technologies
| Technology | Tuning Range | Q | Speed |
|---|---|---|---|
| Varactor-tuned | 2:1 | 50-200 | < 1 us |
| YIG (magnetically tuned) | 4:1 (octave+) | 200-500 | 1-10 ms |
| MEMS-switched | 2:1 | 100-500 | 10-100 us |
| Mechanically tuned cavity | 10-20% | 5000+ | Seconds |
Frequently Asked Questions
What is a tunable filter?
A filter with adjustable center frequency. Technologies: varactor (fast, moderate Q), YIG (widest range, best Q), MEMS (low loss), and mechanical cavity (highest Q). Enables wideband receivers and frequency-agile systems.
What is a YIG filter?
YIG (Yttrium Iron Garnet) filters use a magnetically biased YIG sphere as a resonator. The resonant frequency is linearly proportional to the applied magnetic field: f = 2.8 MHz/Gauss. Tuning range 2-20+ GHz. Q of 200-500. Used in spectrum analyzers.
How fast can tunable filters switch?
Varactor: < 1 us (electronic). MEMS: 10-100 us (mechanical switch). YIG: 1-10 ms (magnetic coil inertia). Mechanical cavity: seconds (motor-driven). Application speed requirement determines the technology choice.