Modulation And Filtering Options; Transmit Latency; Test Pattern Generator - Analog Devices ADF7021-V Manual

MODULATION AND FILTERING OPTIONS

The various modulation and data filtering options for the
ADF7021-V are described in Table 10.
Table 10. Modulation and Filtering Options
Modulation
Binary FSK
2FSK
1
MSK
OQPSK with Half Sine
Baseband Shaping 2
GFSK
GMSK 3
RC2FSK
Oversampled 2FSK
Three-Level FSK
3FSK
RC3FSK
Four-Level FSK
4FSK
RC4FSK
1 MSK is 2FSK modulation with a modulation index = 0.5.
2
Offset quadrature phase shift keying (OQPSK) with half sine baseband
shaping is spectrally equivalent to MSK.
3 GMSK is GFSK with a modulation index = 0.5.

TRANSMIT LATENCY

Transmit latency is the delay time from the sampling of a
bit/symbol by the TxRxCLK signal to when that bit/symbol
appears at the RF output. The latency without any data filtering
is 1 bit. The addition of data filtering adds a further latency as
indicated in Table 11.
It is important that the ADF7021-V be left in transmit mode
after the last data bit is sampled by the data clock to account for
this latency. The ADF7021-V should stay in transmit mode for
a time equal to the number of latency bit periods for the applied
modulation scheme. This ensures that all of the data sampled by
the TxRxCLK signal appears at RF.
Register 2,
Data Filtering Bits[DB6:DB4]
None 000
None 000
None 000
Gaussian 001
Gaussian 001
Raised cosine 101
None 100
None 010
Raised cosine 110
None 011
Raised cosine 111
The figures for latency in Table 11 assume that the positive
TxRxCLK edge is used to sample data (default). If the TxRxCLK
is inverted by setting Register 2, Bits[DB29:DB28], an additional
0.5 bit latency can be added to all values in Table 11.
Table 11. Bit/Symbol Latency in Transmit Mode for Various
Modulation Schemes
Modulation
2FSK
GFSK
RC2FSK, alpha = 0.5
RC2FSK, alpha = 0.7
3FSK
RC3FSK, alpha = 0.5
RC3FSK, alpha = 0.7
4FSK
RC4FSK, alpha = 0.5
RC4FSK, alpha = 0.7

TEST PATTERN GENERATOR

The ADF7021-V has a number of built-in test pattern generators
that can be used to facilitate radio link setup or RF measurement.
A full list of the supported test patterns is shown in Table 12.
The data rate for these test patterns is the programmed data rate
set in Register 3.
The PN9 sequence is suitable for test modulation when carrying
out adjacent channel power (ACP) or occupied bandwidth
measurements.
Table 12. Transmit Test Pattern Generator Options
Test Pattern
Normal
Transmit carrier only
Transmit +f tone only
DEV
Transmit −f tone only
DEV
Transmit 1010 pattern
Transmit PN9 sequence
Transmit SWD pattern repeatedly
Rev. 0 | Page 27 of 60
ADF7021-V
Latency
1 bit
4 bits
5 bits
4 bits
1 bit
5 bits
4 bits
1 symbol
5 symbols
4 symbols
Register 15,
Bits[DB10:DB8]
000
001
010
011
100
101
110