RF Electronics Chapter 5: Frequency Mixers Page 114
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
level for passive FET mixers. Passive FET mixers however have a much narrower
bandwidth.
Figure 5.5. Third order input and output intercept points.
The third order intercept point is useful in determining the RF level required for a
specified 3IM distortion performance. If for example, the 3IM signal is to be 40 dB below
the required signal, then the RF level must be 20 dB below the Third Order Intercept
Point, since then the desired signal will be 20 dB below the intercept point and the 3IM
signals will be 3*20 = 60 dB below the intercept point.
LO Level
Figure 5.6. Different diode configurations for different mixer levels [3].
Frequency mixer manufacturers make mixers to operate at different LO power levels. For
standard level mixers, the LO power required is +7 dBm. Other mixer power levels are
+10, +13, +17, +23, +27 dBm. Mini-Circuits [1, 2] denote their mixer according to the
LO power required, so a Level 7 mixer requires a LO power of +7 dBm. For a good
Double Balanced Mixer, the third order IIP3 is 10 dB above the LO level. By having a
higher power level available, the manufacturers are able to control the diode I-V
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