EV9900 Datasheet, PDF (21/27 Pages) CML Microcircuits – Evaluation Kit

Evaluation Kit for CMX990
EV9900
6.5 Application Information
6.5.1 TX Loop Operating Power Levels
The range of input powers to the feedback port (TxFB) of the offset loop is designed to allow
operation over an 80dB range. This is to permit the loop to lock prior to commencing power
ramping however initial CMX990 silicon has a slightly reduced operating range.
6.5.2 90MHz Operation
Operation of the Tx Loop with a 90MHz IF results in a small degradation of adjacent channel
power. The loop can also have problem locking if the free-running VCO frequency is below the
wanted Tx frequency.
Operation with a 45MHz IF is correct.
6.5.3 Transmitter Adjacent Channel Power
The following commands should be written to the CMX990 to improve the Tx Modulation
spectrum.
Address
0x1C
0x1B
0x1E
0x1D
0x1A
0x1C
0x1B
0x1E
0x1D
0x1A
Value
0x00
0x3D
0x20
0x00
0x0C
0x00
0x3E
0x20
0x00
0x0C
6.6 Evaluation Tests
The EV9900 is intended to allow evaluation of CMX990 RF and baseband performance. The
following is a list of typical test from radio modem standards. Some guidance notes on likely
EV9900 performance are provided.
Frequency Error
Compliant, based on a selected 19.2MHz VCTCXO.
Adjacent Channel Power (ACP)
60dB adjacent channel power can be demonstrated for 12.5kHz channels with G(M)FSK, B_t = 0.3
and 8kbit/s. To achieve this an external LO is required and a TxIF of 45MHz selected.
Spurious Emissions
EV9900 is not designed to be compliant with spurious emissions limits as transmitter filtering is
not included.
Transmitter Attack and Release Time, Transient Behaviour of the Transmitter
See section 6.5.
© 2005 CML Microsystems Plc
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