Digital and Mixed Signal RF ADC and DAC for RF Informational

What is the role of dithering in improving the dynamic range of an ADC in an RF receiver?

Dithering adds a small random signal to the ADC input to break up the correlation between the quantization error and the input signal. Without dithering: the quantization error is deterministic, creating spurious spectral lines (especially for small or periodic signals). With dithering: the quantization error becomes white noise spread uniformly across the Nyquist band, improving SFDR at the cost of a slight increase in the noise floor. Subtractive dither (where the dither signal is digitally subtracted after conversion) provides the SFDR improvement without increasing the noise floor, but requires knowledge of the exact dither signal. Typical dither amplitude: 0.5-1 LSB RMS. In RF receivers: dithering is critical for detecting weak signals in the presence of strong signals, where deterministic spurs from the strong signal could mask the weak one.

Category: Digital and Mixed Signal RF

Updated: April 2026

Product Tie-In: ADCs, DACs, Clock Sources

ADC Dithering

Dither types: additive dither adds random noise to the analog input before conversion. Subtractive dither adds a known pseudo-random sequence and subtracts it digitally after conversion. Non-subtractive dither is simpler to implement but increases the noise floor by the dither power. Many modern high-speed ADCs include built-in dither generators that can be enabled to improve SFDR by 5-15 dB at the expense of 1-3 dB noise floor increase.

Parameter	Pipeline ADC	SAR ADC	Sigma-Delta ADC
Sample Rate	100 MS/s - 10 GS/s	1-100 MS/s	10 kS/s - 50 MS/s
Resolution	8-14 bits	10-20 bits	16-24 bits
Latency	Several clock cycles	1 conversion cycle	Many cycles (decimation)
Power	High	Low-moderate	Low
Typical RF Use	Direct sampling, DPD	Control, monitoring	Audio, baseband

Performance verification: confirm specifications against the application requirements before finalizing the design
Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades

Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture

Common Questions

Frequently Asked Questions

When should I use dithering?

When SFDR is more important than SNR. In wideband receivers with process gain (spreading or integration), the noise floor increase from dithering is recovered while the spur-free dynamic range improvement is retained. Dithering is most beneficial for ADCs with fewer bits (8-12 bits) where quantization spurs are large.

Does dithering reduce effective resolution?

Non-subtractive dithering reduces SNR by the dither power (typically 1-3 dB for 0.5-1 LSB RMS dither). This is equivalent to losing 0.2-0.5 bits of ENOB. Subtractive dithering recovers the SNR loss but requires more complex implementation.

Keep Reading

Related Terms

Need expert RF components?

Request a Quote

RF Essentials supplies precision components for noise-critical, high-linearity, and impedance-matched systems.

Get in Touch