ADL5321

Rev. 0 | Page 11 of 16

MATCHING PROCEDURE

The ADL5321 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 5 were chosen to provide

−14 dB input return loss while maximizing OIP3. The load-pull

plots (see Figure 22, Figure 23, and Figure 24) 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 22 through Figure 24. Therefore, 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 ADL5321 for optimum OIP3 and

gain at 2300 MHz, use the following steps:

1.

Install the recommended tuning components for a 2500 MHz

to 2700 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 because 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. It may 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.

LOAD

FIXED LOAD PULL

FREQ = 2.6000 GHz

IP3

MAX = 41.70dBm

AT 0.4705< 86.63

10 CONTOURS, 1.00dBm STEP

(32.00 TO 41.00dBm)

POUT MAX = 14.16dBm

AT 0.6100< 136.24

10 CONTOURS, 1.00dBm STEP

(5.00 TO 14.00dBm)

GT

MAX = 15.02dBm

AT 0.6100< 136.24

10 CONTOURS, 1.00dBm STEP

(6.00 TO 15.00dB)

SPECS: OFF

0.404< 93.05

Figure 22. Load-Pull Contours, 2600 MHz

LOAD

FIXED LOAD PULL

FREQ = 3.5000 GHz

IP3

MAX = 41.37dBm

AT 0.6911< 142.11

10 CONTOURS, 1.00dBm STEP

(32.00 TO 41.00dBm)

POUT MAX = 14.96dBm

AT 0.7686< 162.58

10 CONTOURS, 1.00dBm STEP

(5.00 TO 14.00dBm)

GT

MAX = 14.02dBm

AT 0.7686< 162.58

10 CONTOURS, 1.00dBm STEP

(5.00 TO 14.00dB)

SPECS: OFF

0.875< –147.48

Figure 23. Load-Pull Contours, 3500 MHz

LOAD

FIXED LOAD PULL

FREQ = 3.6000 GHz

IP3

MAX = 41.29dBm

AT 0.7070< 140.65

10 CONTOURS, 1.00dBm STEP

(32.00 TO 41.00dBm)

POUT MAX = 15.63dBm

AT 0.7057< 161.81

10 CONTOURS, 1.00dBm STEP

(6.00 TO 15.00dBm)

GT

MAX = 13.44dBm

AT 0.7057< 161.81

10 CONTOURS, 1.00dBm STEP

(4.00 TO 13.00dB)

SPECS: OFF

Figure 24. Load-Pull Contours, 3600 MHz