AD6623BCSLASHPCB datasheet(20/40 Pages) AD

20 / 40 page

REV. 0

AD6623

–20–

All of these phase locations are represented in rectangular coor-

dinates by only four unique magnitudes in the positive and negative

directions. These four values are read from four channel registers

that are programmed according to the following table, which

gives the generic formulas and a specific example. The example

is notable because it is only 0.046 dB below full-scale and the

16-bit quantization is so benign at that magnitude, that the rms

error is better than –122 dBc. It is also worth noting that because

none of the phases are aligned with the axes, magnitudes slightly

beyond 0.16 dB above full-scale are achievable.

Table VI. Program Registers

Channel

Magnitude M

Magnitude E 0x7F53

0x12

M 3 cos(p/16)

0x7CE1

0x13

M 3 cos(3p/16)

0x69DE

0x14

M 3 cos(5p/16)

0x46BD

0x15

M 3 cos(7p/16)

0x18D7

Using the four channel registers from the preceding table, the PSK

Modulator assembles the 16 phases according to Table VII.

Table VII. PSK Modulator Phase

Phase

I Value

Q Value

0x12

0x15

0x13

0x14

0x13

0x15

0x12

–0x15

0x12

–0x14

0x13

–0x13

0x14

–0x12

0x15

–0x12

–0x15

–0x13

–0x14

–0x13

–0x15

–0x12

0x15

–0x12

0x14

–0x13

0x13

–0x14

0x12

–0x15

The following three sections show how the phase values are

created for each PSK modulation mode.

/4-DQPSK Modulation

IS-136 compliant

/4-DQPSK modulation is selected by setting

the channel register 0x0C: 6–4 to 001b. The phase word is calculated

according to the following diagram. The two LSBs of the serial

input word update the payload bits once per symbol. The QPSK

Mapper creates a data dependent static phase word (Sph) which

is added to a time dependent rotating phase word (Rph). The Rph

starts at zero when the RCF is reset or switches modes via a sync

pulse. Otherwise, the Rph increments by two on every symbol.

SERIAL

QPSK

MAPPER

SPH

[1:0]

[3:0]

PHASE

[3:0]

RPH

Figure 22. QPSK Mapper

The Sph word is calculated by the QPSK Mapper according to

the following truth table.

Table VIII. QPSK Mapper Truth Table

Serial [1:0]

Sph [3:0]

00b

01b

11b

10b

8-PSK Modulation

IS-136+ compliant 8-PSK modulation is selected by setting the

channel register 0x0C: 6–4 to 101b. The Phase word is calculated

according to the following diagram. The three LSBs of the serial

input word update the payload bits once per symbol.

SERIAL

8PSK

MAPPER

[2:0]

PHASE

[3:0]

Figure 23. 8-PSK Mapper

The Phase word is calculated by the 8-PSK Mapper according

to the following truth table:

Table IX. 8-PSK Mapper Truth Table

Serial [2:0]

Sph [3:0]

111b

011b

010b

000b

001b

101b

100b

110b

/8-8-PSK Modulation

EDGE compliant 3 /8-8-PSK modulation is selected by setting the

channel register 0x0C: 6–4 to 110b. The phase word is calculated

according to the following diagram. The three LSBs of the serial

input word update the payload bits once per symbol. The 8-PSK

Mapper creates a data-dependent static phase word (Sph) which is

added to a time-dependent rotating phase word (Rph). The 8-PSK

Mapper operates exactly as described in the preceding 8-PSK

Modulation section. The Rph starts at zero when the RCF is reset

or switches modes via a sync pulse. Otherwise, the Rph increments

by three on every symbol.

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