CMX994 Datasheet, PDF (38/61 Pages) CML Microcircuits – Local Oscillator

Direct Conversion Receivers
CMX994/CMX994A/CMX994E
0
0
Attenuation/ dB
-6 -12 -18 -24 -30 -36 -42
-5
-10
I
-15
Q
-20
-25
-30
8.1.3
Figure 19 Example Variation in V_offset with Gain Control Setting
Gain Control
The CMX994/CMX994A/CMX994E has gain control mechanisms in the LNA and the baseband (see Figure 20)
with a total control range of 60dB. The gain can be controlled using the Rx Gain Control Register, $16; see
section 7.7.1.
The LNA gain control steps can be adjusted to achieve the required accuracy using the step size control bits in
the Rx Gain Control Register. The effect of the step size control varies with frequency, as shown in Table 15,
Table 16 and Table 17 so for optimum accuracy the best settings should be selected to suit the particular
application. (Suggested settings for optimum gain accuracy are shaded grey in the tables.)
LO Input
18dB
Gain
Contol,
6dB Steps
42dB
Gain
Contol,
6dB Steps
Figure 20 Gain Control
I Channel
Q Channel
 2015 CML Microsystems Plc
Page 38 of 70
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