EV9900 Datasheet, PDF (17/27 Pages) CML Microcircuits – Evaluation Kit

Evaluation Kit for CMX990
EV9900
Differential Amplifiers
Simple circuits are provided to allow evaluation of the differential amps on the CMX990 (R117,
R118, R119, R120, R121, R122, R123, R124, C156 and C157).
Temperature Sensors
Two temperature sensors are provided, one (U21) adjacent to the PAs and the other (U19)
adjacent to the VCTCXO. These are connected to the CMX990 Aux ADC inputs 0 and 1
respectively.
Tx/Rx Switch
Although not configured in the default EV9900, circuits are provided to implement a Tx / Rx switch
using PIN diodes. (See section 6.2.2)
Interface
The EV9900 provides access to the CMX990 parallel interface via connector J13.
The EV9900 has test pins to allow measurement of aux DAC outputs and test pins that allow the
user to apply test signals to the aux ADC inputs.
All RF connectors are SMA type.
The power connector provides two separate power connections: one for the power amplifier and
the other to supply all other circuits.
6.2 Adjustments and Controls
The user has the ability to configure the EV9900 for a number of different operational scenarios.
6.2.1 Mixer Bypass / 400MHz Operation
The CMX990 contains a mixer intended for the 1^st mixer in a superhetrodyne receiver
architecture. The mixer is an image reject type intended for a 45MHz IF output. The
intermodulation performance of this mixer does not meet some performance standards, such as
EN 300 113, so the user may wish to use an external mixer with the CMX990 if such performance
is desired. The EV9900 has been supplied with a typical mixer bypass circuit, using a diode ring
mixer, which may be used as an alternative to the CMX990 mixer. By default the EV9900 is
configured to use the CMX990 mixer.
To use the external mixer the following changes should be made:
• C56 and C168 should be fitted with a 1nF capacitor.
• Remove C191 unless 400MHz LNA is to be used.
• R177 should be fitted with 0R resistor unless 400MHz LNA is to be used.
• R151 should be fitted with 18R resistor.
• L28 and T3 should be removed.
• The user will need to match the IF Filter (F2) to the output of the buffer.
Components C46, L3 and C56 are likely to need optimisation.
© 2005 CML Microsystems Plc
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