AD9786BSVRL datasheet(13/56 Pages) AD

13 / 56 page

AD9786

Rev. B | Page 13 of 56

Group Delay

Number of input clocks between an impulse applied at the

device input and peak DAC output current. A half-band FIR

filter has constant group delay over its entire frequency range

Impulse Response

Response of the device to an impulse applied to the input.

Adjacent Channel Leakage Ratio (ACLR)

A ratio in dBc between the measured power within a channel

relative to its adjacent channel.

Complex Modulation

The process of passing the real and imaginary components of a

signal through a complex modulator (transfer function = ejwt =

coswt + jsinwt) and realizing real and imaginary components

on the modulator output.

Hilbert Transform

A function with unity gain over all frequencies, but with a phase

shift of 90° for negative frequencies and a phase shift of –90° for

positive frequencies. Although this function cannot be imple-

mented ideally, it can be approximated with a short FIR filter

with enough accuracy to be very useful in single sideband radio

architectures.

Complex Image Rejection

In a traditional two-part upconversion, two images are created

around the second IF frequency. These images are redundant

and have the effect of wasting transmitter power and system

bandwidth. By placing the real part of a second complex modulator

in series with the first complex modulator, either the upper or

lower frequency image near the second IF can be rejected.

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