ADRF6510ACPZ-R7 datasheet(19/32 Pages) AD

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Data Sheet

ADRF6510

Rev. B | Page 19 of 32

The most challenging scenario in terms of dynamic range is the

presence of a large out-of-band blocker accompanying a weaker

in-band wanted signal. In this case, the maximum input level is

dictated by the blocker and its inclination to cause distortion.

After filtering, the weak wanted signal must be amplified to the

desired output level, possibly requiring maximum gain. Both

the distortion limits associated with the blocker at the input and

the SNR limits created by the weaker signal and higher gains are

present simultaneously. Furthermore, not only does the blocker

scenario degrade the dynamic range but it also reduces the

range of input signals that can be handled because a larger part

of the gain range is used to simply extract the weak desired

signal from the stronger blocker.

KEY PARAMETERS FOR QUADRATURE-BASED

RECEIVERS

The majority of digital communication receivers makes use of

quadrature signaling, in which bits of information are encoded

onto pairs of baseband signals that then modulate in-phase (I)

and quadrature (Q) sinusoidal carriers. Both the baseband and

modulated signals appear quite complex in the time domain with

dramatic peaks and valleys. In a typical receiver, the goal is to

recover the pair of quadrature baseband signals in the presence

of noise and interfering signals after quadrature demodulation.

In the process of filtering out-of-band noise and unwanted inter-

ferers and restoring the levels of the wanted I and Q baseband

signals, it is critical to retain their gain and phase integrity over

the bandwidth.

The ADRF6510 delivers flat in-band gain and group delay,

consistent with a six-pole Butterworth prototype filter as

described in the Programmable Filters section. Furthermore,

careful design ensures excellent matching of these parameters

between the I and Q channels. Although absolute gain flatness

and group delay can be corrected with digital equalization,

mismatch introduces quadrature errors and intersymbol inter-

ference that degrade bit error rates in digital communication

systems.

ADRF6510ACPZ-R7 Datasheet(PDF) 19 Page - Analog Devices