ADRF5720BCCZN-R7 datasheet(18/19 Pages) AD

18 / 19 page

ADRF5720

Data Sheet

Rev. 0 | Page 18 of 19

PROBE MATRIX BOARD

The probe matrix board is a 4-layer board. Similar to the evaluation

board, the probe matrix board also uses a 12 mil Rogers RO4003

dielectric. The top and bottom copper layers are 0.5 oz (0.7 mil)

plated to 1.5 oz (2.2 mil). The RF transmission lines are designed

using a CPWG model with a width of 16 mil and ground

spacing of 6 mil to have a characteristic impedance of 50 Ω.

Figure 41 and Figure 42 show the cross sectional view and the

top view of the board, respectively. Measurements are made

using GSG probes at close proximity to the RF pins (ATTIN

and ATTOUT). Unlike the evaluation board, probing reduces

reflections caused by mismatch arising from connectors, cables,

and board layout, resulting in a more accurate measurement of

the device performance.

Figure 41. Probe Matrix Board Stackup, Cross Sectional View

Figure 42. Probe Matrix Board Top View

The probe matrix board includes a thru reflect line (TRL)

calibration kit, allowing board loss de-embedding. The actual

board duplicates the same layout in matrix form to assemble

multiple devices at one time. All S-parameters were measured

on this board.

Impedance Matching

Impedance matching at the RF pins (ATTIN and ATTOUT) can

improve insertion loss, return loss, and attenuation accuracy at

high frequencies. Figure 43 and Figure 44 show the difference in

the transmission lines at the ATTIN and ATTOUT pins.

The dimensions of the 50 Ω lines are 16 mil trace width and

6 mil gap. To implement this impedance matched circuit, the

pad length is extended by 5 mil (from 17 mil to 22 mil). The

calibration reference kit does not include the 5 mil matching

line and, therefore, the measured insertion loss includes the

losses of the matching circuit.

Figure 43. Without Impedance Match

Figure 44. With Impedance Match

RO4003

1.5oz Cu (2.2mil)

0.5oz Cu (0.7mil)

1.5oz Cu (2.2mil)

W = 16mil

G = 6mil

T = 2.2mil

H = 12mil

6mil

10mil

17mil

10mil

22mil

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