CMX991 Datasheet, PDF (11/56 Pages) CML Microcircuits – Two-mode demodulator

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 1^st Mixer
The Rx 1^st 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 1^st 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.
L1
Input
T1
L2
R1
C3
MIXINP
C4
MIXINN
CMX991
CMX992
R2
Figure 6 Example External Components – Receive 1^st Mixer Input
L1 27nH
C3 1nF
C4 1nF
L2 33nH
T1 TC1-1-13M+
R1 and R2 NF
Table 4 Typical Rx 1^st Mixer Input Matching Components for 455MHz
 2015 CML Microsystems Plc
11
D/991_992/20