AD7002

–5–

REV. B

GMSK Phase Trajectory Error

This is a measure of the phase error between the transmitted

phase of an ideal GMSK modulator and the actual phase trans-

mitted by the AD7002, when transmitting a random sequence

of data bits. It is specified as a peak phase error and also as an

rms phase error.

Group Delay Linearity

The group delay linearity, or differential group delay, is the

group delay over the full band relative to the group delay at one

particular frequency. The reference frequency for the AD7002 is

1 kHz.

Group Delay Between Channels

This is the difference between the group delay of the I and Q

channels and is a measure of the phase matching characteristics

of the two.

Integral Nonlinearity

This is the maximum deviation from a straight line passing

through the endpoints of the DAC or ADC transfer function.

Maximum Phase Effect Instance

This is the time at which a transmitted data bit will have its

maximum phase change at the ITx and QTx outputs (see fig-

ure). This time includes the delay in the GMSK modulator and

in the Analog low-pass filters. Maximum phase effect instance is

measured from the Tx CLK falling edge, which latches the data

bit, to the ITx and QTx analog outputs.

90

°

0

°

≈ 9µs

DATA BIT

CLOCKED IN BY TxCLK

MAXIMUM PHASE

EFFECT INSTANT

45

°

Transmit Channel Maximum Phase Effect Instance

Output Rate

This is the rate at which data words are made available at the

Rx DATA pin (Mode 0) or the IDATA and QDATA pins

(Mode 1). There are two rates, depending on whether the de-

vice is operated in RATE0 or RATE1.

Offset Error

and the auxiliary DACs and is expressed in mVs for the Trans-

mit section and in LSBs for the Auxiliary section.

Output Impedance

This is a measure of the drive capability of the auxiliary DAC

outputs and is expressed in k

Ωs.

Output Signal Span

This is the output signal range for the Transmit Channel section

and the Auxiliary DAC section. For the transmit channel the

span is

±1.25 volts centered on 2.5 volts, and for the Auxiliary

Output Signal Full-Scale Accuracy

This is the accuracy of the full-scale output (all 1s loaded to the

DACs) on each transmit channel measured w.r.t. 25 V and is

expressed in dBs.

Phase Matching Between Channels

This is a measure of the phase matching characteristics of the I

and Q transmit channels. It is obtained by transmitting all ones

and then measuring the difference between the actual phase

shift between the I and Q outputs and the ideal phase shift of

90

°.

Sampling Rate

This is the rate at which the modulators on the receive channels

sample the analog input.

Settling Time

This is the digital filter settling time in the AD7002 receive

section. On initial power-up, or after returning from the sleep

mode, it is necessary to wait this amount of time to obtain use-

ful data.

Signal Input Span

The input signal range for the I and Q channels is biased about

±1.25 volts about this point.

Signal to (Noise + Distortion) Ratio

This is the measured ratio of signal-to-(noise + distortion) at the

output of the receive channel. The signal is the rms amplitude of

the fundamental. Noise is the rms sum of all amplitude of the

fundamental. Noise is the rms sum of all nonfundamental sig-

ratio is dependent upon the number of quantization levels in the

digitization process; the more levels, the smaller the quantiza-

tion noise. The theoretical signal-to-(noise+distortion) ratio for

a sine wave is given by:

Signal to (Noise + Distortion) = (6.02N + 1.76) dB