RF Quadrature Transceiver / RF Quadrature Receiver
CMX991/CMX992
4.3
Transmitter (CMX991 only)
4.3.1 Transmitter
Details of the transmitter are contained in the Transmitter description, section 5.3. The components used
around the CMX991 will depend on application requirements, however a typical configuration is shown in
Figure 10.
VCCRF
TXOUTP
Tx Output
R1
AVDD
CMX991
C1
T1
TXOUTN
VCCRF
Figure 10 Example External Components – Transmitter
C1 10nF (note 1)
T1 4:1 balun with centre tap (note 2)
R1 3.3Ω
Table 8 Transmitter Components
Notes:
1
Value of C1 is dependant on frequency of operation. At higher frequencies an additional low value
decoupling capacitor in parallel (e.g. 33pF) may be required for optimum performance. C1 should be located
as close to the centre tap of T1 as possible.
2
3
Example component for T1 is Mini-Circuits TC4-14+.
Additional components may be required at the T1 output for optimum match to 50Ω.
4.3.2 IF I/Q Modulator Output
The I/Q modulator can be used on its own, without the up-conversion mixers, by switching the I/Q
modulator output to the output pin, TXIFOUT (pin 48) – see section 6.5. A typical configuration for this
output is shown in Figure 11.
2012 CML Microsystems Plc
15
D/991_992/18
CMLMICRO [ CML MICROCIRCUITS ]
