Overview of Modifications
Experimentation has shown that the frequency range of the MAX2010
adjustable RF predistorter can be extended below 500MHz by implementing simple changes to the input and output matches of the phase section. Note that these changes pertain to the phase section only. Similar changes may be possible for the gain section as well, though Class AB applications are best served by employing only the phase expansion from the MAX2010.
Using the standard MAX2010 EV kit (Figure 1
), modify the following components to yield optimal performance at 360MHz:
C1: change from 100pF to 330pF
C11: change from 2.2pF to 5.6pF
L1, L2: change from 5.6nH to 19nH (Coilcraft 0402CS-19NXJB)
C12: change from 2.2pF to 5.6pF
C10: change from 100pF to 220pF
Figure 1. MAX2010 EV kit schematic.
Resulting Phase-Expansion Characteristics at 360MHz
The plot in Figure 2
depicts the typical phase expansion possible at 360MHz after employing the changes outlined in the previous section.
Figure 2. MAX2010 phase-expansion characteristics at 360MHz.
Input-Matching Characteristics at 360MHz
Figure 3. MAX2010 input match at 360MHz.
Output-Matching Characteristics at 360MHz
Figure 4. MAX2010 output match at 360MHz.