RF Quadrature Transceiver / RF Quadrature Receiver
CMX991/CMX992
4.2
Receiver (CMX991 and CMX992)
The receiver relies on an external LNA, filtering and a transmit/receive switch; details can be found in
section 5.2.
4.2.1 Rx 1st Mixer
The Rx 1st Mixer has a differential input with a nominal impedance of 300 and series capacitance of 8pF.
To ensure optimum performance a balun is required when driving from typical single-ended (un-balanced)
LNAs or filters. The balun may be a transformer type or implemented using LC networks. A typical
matching circuit to the Rx 1st Mixer is shown in Figure 6. In a particular implementation the shunt resistors
R1 and R2 may be replaced by a single component across the balun T1 output. The blocking capacitors
C3 and C4 may be omitted if the input signals are 0V dc biased. DC should not be applied to the input
pins, otherwise damage to the internal protection diodes may result.
CMX991
R1
CMX992
L1
C3
Input
MIXINP
MIXINN
T1
L2
C4
R2
Figure 6 Example External Components – Receive 1st Mixer Input
L1 27nH
C3 1nF
C4 1nF
L2 33nH
T1 TC1-1-13M+
R1 and R2 NF
Table 4 Typical Rx 1st Mixer Input Matching Components for 455MHz
2012 CML Microsystems Plc
11
D/991_992/18
CMLMICRO [ CML MICROCIRCUITS ]
