CMX994 Datasheet, PDF (45/61 Pages) CML Microcircuits – Local Oscillator

Direct Conversion Receivers
CMX994/CMX994A/CMX994E
Assuming a good PCB layout with minimal stray capacitance, Figure 25 shows the typical bandwidth of the Rx
mixer output.
0
-0.5
-1
-1.5
-2
-2.5
-3
-3.5
-4
-4.5
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
I/Q Output Frequency / MHz
Figure 25 Rx Mixer Output Bandwidth
8.1.10
Spurious Responses
An advantage of the direct conversion receiver approach is the inherently low number of spurious responses,
however the circuit still has responses at harmonics and sub-harmonics. The circuit designer will need to
provide suitable high-pass and low-pass filtering at the CMX994/CMX994A/CMX994E input (and/or between
LNA and mixers) to prevent such responses.
Note: large signals at sub-harmonic frequencies will generate harmonics in the LNA output which cannot be
removed after the LNA because they are on the wanted frequency of the receiver.
 2015 CML Microsystems Plc
Page 45 of 70
D/994_A_E/1