ADL5320

Rev. 0 | Page 12 of 16

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 6 were chosen to provide

−10 dB input return loss while maximizing OIP3. The load-pull

plots (Figure 28, Figure 29, and Figure 30) 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 7 and

Table 8 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 7 and Table 8 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 28 through Figure 30. 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 simulta-

neously.

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 28. Load-Pull Contours, 880 MHz

Figure 29. Load-Pull Contours, 2140 MHz

Figure 30. Load-Pull Contours, 2600 MHz