
Data Sheet ADL5320
Rev. A | Page 13 of 20
MATCHING PROCEDURE
The ADL5320 is designed to achieve excellent gain and IP3
performance. To achieve this, both input and output matching
networks must present specific impedance to the device. The
matching components listed in Table 7 were chosen to provide
−10 dB input return loss while maximizing OIP3. The load-pull
plots (Figure 36, Figure 37, and Figure 38) show the load
impedance points on the Smith chart where optimum OIP3, gain,
and output power can be achieved. These load impedance values
(that is, the impedance that the device sees when looking into
the output matching network) are listed in Table 8 and Table 9
for maximum gain and maximum OIP3, respectively. The contours
show how each parameter degrades as it is moved away from
the optimum point.
From the data shown in Table 8 and Table 9 it becomes clear that
maximum gain and maximum OIP3 do not occur at the same
impedance. This can also be seen on the load-pull contours in
Figure 36 through Figure 38. Thus, output matching generally
involves compromising between gain and OIP3. In addition,
the load-pull plots demonstrate that the quality of the output
impedance match must be compromised to optimize gain and/or
OIP3. In most applications where line lengths are short and
where the next device in the signal chain presents a low input
return loss, compromising on the output match is acceptable.
To adjust the output match for operation at a different frequency or
if a different trade-off between OIP3, gain, and output impedance
is desired, the following procedure is recommended.
For example, to optimize the ADL5320 for optimum OIP3 and
gain at 700 MHz use the following steps:
1. Install the recommended tuning components for a 800 MHz
to 960 MHz tuning band, but do not install C3 and C7.
2. Connect the evaluation board to a vector network analyzer
so that input and output return loss can be viewed
simultaneously.
3. Starting with the recommended values and positions for
C3 and C7, adjust the positions of these capacitors along
the transmission line until the return loss and gain are
acceptable. Push-down capacitors that are mounted on small
sticks can be used in this case as an alternative to soldering.
If moving the component positions does not yield satisfactory
results, then the values of C3 and C7 should be increased
or decreased (most likely increased in this case as the user
is tuning for a lower frequency). Repeat the process.
4. Once the desired gain and return loss are realized, OIP3
should be measured. Most likely, it will be necessary to go
back and forth between return loss/gain and OIP3
measurements (probably compromising most on output
return loss) until an acceptable compromise is achieved.
Figure 36. Load-Pull Contours, 880 MHz
Figure 37. Load-Pull Contours, 2140 MHz
Figure 38. Load-Pull Contours, 2600 MHz