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 also be possible for the gain section, 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 450MHz:
C11: change from "not installed" to 4.7pF
C1: change from 8.2pF to 330pF
L1: change from 5.6nF to 15nH
C12: change from "not installed" to 4.7pF
L2: change from 5.6nF to 15nH
Figure 1. MAX2010 EV kit schematic.
Resulting Phase-Expansion Characteristics at 450MHz
The plot in Figure 2
depicts the typical phase expansion possible at 450MHz after employing the changes outlined in the previous section.
Figure 2. MAX2010 phase expansion characteristics at 450MHz.
Parasitic Gain-Compression Characteristics at 450MHz
The graph in Figure 3
displays the typical gain-compression characteristic that can be achieved after changing the aforementioned components to their new values.
Figure 3. MAX2010 parasitic gain-compression characteristics at 450MHz.
Input-Matching Characteristics at 450MHz
Figure 4. MAX2010 input match at 450MHz.
Output-Matching Characteristics at 450MHz
Figure 5. MAX2010 output match at 450MHz.