ADL5380ACPZ-R7 datasheet(29/36 Pages) AD

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ADL5380

Rev. 0 | Page 29 of 36

As the load impedance of the filter increases, the filter design

becomes more challenging in terms of meeting the required

rejection and pass band specifications. In the previous W-CDMA

example, the 500 Ω load impedance resulted in the design of a

sixth-order filter that has relatively large inductor values and small

capacitor values. If the load impedance is 200 Ω, the filter design

becomes much more manageable. Figure 92 shows a fourth-order

filter designed for a 10 MHz wide LTE signal. As shown in Figure 92,

the resultant inductor and capacitor values become much more

practical with a 200 Ω load.

2.2µH

1.5µH

Figure 92. Fourth-Order Low-Pass LTE Filter Schematic

Figure 93 and Figure 94 illustrate the magnitude response and

group delay response of the fourth-order filter, respectively.

–35

–25

–15

–5

–30

–20

–10

–40

FREQUENCY (MHz)

Figure 93. Fourth-Order Low-Pass LTE Filter Magnitude Response

1520253035

FREQUENCY (MHz)

Figure 94. Fourth-Order Low-Pass LTE Filter Group Delay Response

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