AD9083BBCZ datasheet(27/93 Pages) AD

27 / 93 page

Data Sheet

AD9083

Rev. 0 | Page 27 of 93

TERMINOLOGY

Noise Spectral Density (NSD)

The NSD is the noise power normalized to 1 Hz bandwidth (at

a particular frequency) relative to the full-scale of the ADC

(dBFS). NSD is given in units of dBFS/Hz. Unlike a descrete-

time flash type ADC, a Σ-Δ ADC displays uneven NSD across

the spectrum from dc up to fS. Typical NSD at various

inflection points are reported in the specifications. The total

SNR is not always a straightforward calculation and it is often

useful to think in terms of noise density instead of SNR.

Achieving a good SNR is dependent on filtering out the

wideband CTSD ADC quantization noise.

ADC DATA OUTPUT

1/f NOISE

fs/64

fs/16

fs/2

THERMAL NOISE

BAND OF

INTEREST

QUANTIZATION

NOISE

ADC NOISE

Figure 54. Noise Regions of a Σ-Δ ADC

In-Band Noise

In-band noise is the integrated noise power measured over a

user defined bandwidth relative to the full-scale of the ADC (in

dBFS). This bandwidth is typically equal to an intermediate

frequency (IF) pass-band.

Third-Order Intermodulation Distortion (IMD3)

IMD3 is a figure of merit used to quantify the linearity of a

component or system. Two equal amplitude, unmodulated

carriers at specified frequencies (f1 and f2) injected in a nonlinear

system exhibiting third-order nonlinearities produce IMD

components at 2f1 − f2 and 2f2 − f1. Note that the IMD3

performance of an ADC does not necessarily follow the 3:1 rule

that is typical of RF/IF linear devices. IMD3 performance is

dependent on dual tone frequencies, signal input levels, and the

ADC clock rate.

Harmonic Distortion (HD2, HD3 and SFDR)

A harmonic tone that falls within the IF band of interest when a

single tone is swept across the user defined frequency range.

Signal Transfer Function (STF)

STF is the frequency response of the ADC output signal relative

to a swept single tone at the ADC input. The Typical

Performance Characteristics section shows the STF over the IF

pass-band to highlight pass-band flatness. The STF also affects

aliasing of undesired signal near fS.

AD9083BBCZ Datasheet(PDF) 27 Page - Analog Devices

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