Dynamic Range
Understanding Dynamic Range
Dynamic range determines how well a receiver handles the real-world signal environment, where strong interferers and weak desired signals coexist. A receiver with insufficient dynamic range will either miss weak signals (below noise floor) or distort/saturate from strong signals.
Dynamic Range Definitions
- Linear DR: Range from noise floor to P1dB (1 dB compression). Single-signal.
- SFDR (Spur-Free DR): Range from noise floor to the input level where the largest spur equals the noise floor. Multi-signal. The most useful specification.
- Blocking DR: Range from sensitivity to the input level that causes desensitization.
Typical Dynamic Range Values
- Consumer receiver: 70-90 dB SFDR.
- Base station receiver: 85-100 dB SFDR.
- Military/SIGINT receiver: 100-120 dB SFDR.
- Spectrum analyzer: 80-110 dB SFDR.
Frequently Asked Questions
What is dynamic range?
Dynamic range is the ratio of the largest to smallest signals a system can process. The lower limit is the noise floor; the upper limit is compression or distortion. It determines how well a receiver handles mixed strong and weak signal environments.
What is SFDR?
SFDR (Spurious-Free Dynamic Range) is the input power range from noise floor to the level where the worst spur equals the noise floor. For a system with IIP3 and noise figure: SFDR = 2/3 x (IIP3 - noise floor). It is the most meaningful dynamic range specification.
How do you increase dynamic range?
Lower noise figure (reduces noise floor), higher IP3 (raises distortion threshold), wider IF bandwidth increases noise floor but may be necessary for signal bandwidth. Better ADCs with higher SFDR. Pre-selection filtering to reject out-of-band interferers.