Evaluation Kit for CMX990
EV9900A
Transmitter
The transmitter provides at least +30dBm in the default configuration (410-430MHz). The
420MHz PA is tuneable (by component changes) over the range 150 to 900MHz, however lower
output power is available over 750MHz. The transmit VCO (U8) also has very broad tuning range
typically from below 400MHz to above 450MHz with a 3.3V charge pump. U8 would need to be
changed for operation on other bands, for example 800MHz (contact CML for further information).
The CMX990 RAM DAC output (DAC 0) is connected to the PA control line via a diode and
transistor (D10 and TR4) to provide sufficient current to the PA control pin.
Local Oscillators
VCO’s are provided for the main and aux synthesizers. The aim is to cover the frequency bands
of 410-430MHz (Rx and Tx).
This requires the following local oscillator frequencies, based on the following frequency plan:
Rx Band / MHz
Tx Band / MHz
Tx IF / MHz
Rx IF / MHz
LO Range / MHz
729.8-769.8
730-770
410-430
45.1
410-430
45
Table 6 – Local Oscillator Frequencies
The VCOs are packaged parts from Z-Communications, who provide a range of VCO’s in the
same package outline, so that the user can evaluate other frequency bands if required. These
VCOs have some performance limitations and are marginal for EN 300 113 adjacent channel
requirements for transmitter and receiver.
The facility to use a discrete, high performance, low phase noise VCO circuit, is also provided
(TR11, TR12 and coaxial resonator TL6), However this is not enabled in the default configuration.
This may be re-tuned by component changes if required by the user.
The aux VCO is a discrete design operating at around 180MHz. Again this may be re-tuned by
component changes if required by the user.
© 2007 CML Microsystems Plc
17
UM9900A/3
CMLMICRO [ CML MICROCIRCUITS ]
