CMX971 Datasheet, PDF (19/25 Pages) CML Microcircuits – Small 16-lead VQFN Package

Quadrature Modulator
25
CMX971
20
15
10
5
0
0
100
200
300
400
500
600
700
800
900
1000
Frequency / MHz
Figure 11 Linearity Measured as Output Third Order Intercept Point (OIP3) Variation with
Frequency
8.2.3 Wideband Noise
The CMX971 noise floor does not vary significantly with LO input level: with LO levels between -5dBm and
-15dBm, less than 0.5dB of variation from the typical value of -150dBm/Hz can be expected.
For optimum wideband noise during modulation the F bits in the Control Register ($1E, b3-b0) should be
set to ‘1111’. Wideband noise during modulation measured at a 5MHz offset from a 390MHz signal is
shown in Table 5.
Freq Setting
($1E, b3-b0)
‘0000’
‘1111’
Output Level
(dBm)
3.9
4.2
Noise at 5 MHz
offset (dBc/Hz)
-143.7
-146
Table 5 Typical Wideband Noise at 5MHz Offset with Different Frequency Control Settings
 2015 CML Microsystems Plc
19
D/971/4