Evaluation Kit for the CMX998
|EV9980 User Manual (rev8)|
- Allows Full Evaluation of the CMX998 IC
- Operational Frequency Range: 100MHz to 1GHz
- Complete Demonstration of CFBL Functionality
- Access to RF, Control and Baseband Signals
- Support and Interfacing for Customer PAs
- Differential or Single-ended I and Q Inputs
- 360 Loop Phase Shift Control
- Can utilise PE0003 EvKit interface to work with a PC or can be used with custom interface equipment
- For the Evaluation, Demonstration and Design-In of the CMX998
- 7.2V (typ) power supply
- 1.2V and 3.6V for on-board RF PA
The EV9980 EvKit allows rapid and full evaluation of the CMX998
Cartesian Feedback Transmitter IC.
In the form of a populated PCB, this flexible platform enables
users, using a control interface, to configure and evaluate the
CMX998 to various applications and frequency bands.
Access is provided to all CMX998 RF, baseband and control signals
by either connector or test points. Test access points are
available to accept common test equipments such as RF and baseband
signal generators and spectrum analysers.
All signal paths are matched by suitable components and the EvKit
provides a power amplifier (PA) device at 450MHz which can be
modified to provide operation at 800MHz. The EvKit can also be
configured for an external PA. The overall operating evaluation
frequency range of the EvKit is for RF frequencies between 100MHz
The EV9980 can be configured to work with the CMX981 Digital Radio
Baseband processor IC, standard test equipment or with a custom
No software is required for use of the EvKit; the on-board CMX998
is controlled via its C-BUS serial interface and control system.
This can be controlled by a PE0003 interface card (available
separately) or, alternatively, a custom C-BUS interface and control
system can be used.
Design Support Information
Q. When using the CMX998 Cartesian loop IC with its evaluation kit
(EV9980) I have seen degradation in carrier leakage when I enable
the RF detector after the DC calibration phase.
What can I do to ensure a stable carrier leakage when I enable the
A. In some configurations of the EV9980 the DC offset adjustment
appears degraded when DCMEAS is set to "0" to "1".
That is to say when the RF detector output is connected to the
DCMEAS pin following a DC calibration procedure. The cause of this
is internal offsets that result in a small, (nominally 5mV), shift
in VREF and BVREF when the change is made.
The effect is shown in Table 1 (below):
|DC On||RF Det.||DCMEAS||Carrier leakage with DC offset adjusted on|
RV1/RV2 with Fixed bias offset
|Carrier leakage with DC offset adjusted on|
RV1/RV2 with BVREF used for bias offset
|1||0||0||-33dBm (-63dBc)||-26dBm (-56dBc)|
|1||1||0||-33dBm (-63dBc)||-27dBm (-57dBc)|
|0||1||0||-24dBm (-54dBc)||-27dBm (-57dBc)|
|0||1||1||-4dBm (-34dBc)||-22dBm (-52dBc)|
|1||1||1||-4dBm (-34dBc)||-22dBm (-53dBc)|
|0||0||1||-23dBm (-53dBc)||-28dBm (-58dBc)|
Table 1 - Carrier leakage achieved with for various conditions of DCMEAS
and associated control signals, PA enabled (+30dBm mean power with
modulation), 450MHz, Divide by 2 LO.
The transmitter is configured for +30dBm mean output power, TETRA
pi/4-DQPSK or two-tone modulation, so a carrier null of 33dBm is
-63dBc, where 'c' is based on the mean signal power.
When DCMEAS = '1' and the RF detector is enabled a degradation in
carrier offset is observed with a previously adjusted carrier-null.
This effect can be avoided by using BVREF to bias the input signal
rather than using a resistor network tied to 3.3V.
With PCB555D in 'Mod State' 3 or 5 the BVREF signal is already used