ADRF6518ACPZ-R7 datasheet(28/39 Pages) AD

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ADRF6518

Data Sheet

Rev. A | Page 28 of 39

the out-of-band blockers, because this can corrupt the data in

the signal and degrade the EVM. For examples of this, see the

applications information section in the ADRF6510 and the

ADRF6516 data sheets. Figure 83 also shows this trade-off

between filter corner and signal bandwidth.

In Figure 73 through Figure 77, the x-axis is appropriately

labeled in units of a voltage ratio, which is defined as

20 × log10(x/1 V p-p)

where x is any number in units of V p-p.

This is done because the 100 Ω differential baseband source

(Agilent MXG N5182B) drives the 400 Ω differential input

impedance of the ADRF6518. The standard unit of power ratio,

dBm, is only applicable in a 50 Ω system.

Figure 73 and Figure 74 show EVM vs. input voltage over

different symbol rates in filter mode (filter corner = 63 MHz)

and in filter bypass mode, respectively. EVM is generally better

for higher symbol rates while in filter bypass mode. This is

mainly due to the absence of noise and distortion components

that the filter introduces. For the same 80 MSPS signal, EVM

improves 11 dB when switching from a 63 MHz filter corner to

filter bypass mode. For the lower symbol rates, the difference in

EVM between a 63 MHz filter corner and filter bypass mode is

negligible.

Figure 73. EVM vs. Input Voltage over Symbol Rates; Filter Corner = 63 MHz,

QPSK, Gain Code = 0000000, 1.5 V p-p Differential Output Level Maintained

Figure 74. EVM vs. Input Voltage over Symbol Rates; Filter Bypass Mode,

QPSK, Gain Code = 0000000, 1.5 V p-p Differential Output Level Maintained

Figure 75 and Figure 76 show EVM vs. input voltage over

different modulation types at 50 MSPS in filter mode and in

filter bypass mode, respectively. EVM improves for the high-

order modulation types when the filter is in bypass mode.

Figure 75. EVM vs. Input Voltage over Modulation Type; Filter Corner =

63 MHz, QPSK, 50 MSPS, Gain Code = 0000000, 1.5 V p-p Differential Output

Level Maintained

Figure 76. EVM vs. Input Voltage over Modulation Type; Filter Bypass Mode,

QPSK, 50 MSPS, Gain Code = 0000000, 1.5 V p-p Differential Output Level

Maintained

–50

–45

–40

–35

–30

–25

–20

–15

–10

–5

–40

–30

–20

–10

VIN (dBV p-p)

5MSPS

10MSPS

50MSPS

–50

–45

–40

–35

–30

–25

–20

–15

–10

–5

–40

–30

–20

–10

VIN (dBV p-p)

5MSPS

10MSPS

50MSPS

–50

–45

–40

–35

–30

–25

–20

–15

–10

–5

–40

–30

–20

–10

VIN (dBV p-p)

QPSK

16QAM

256QAM

–50

–45

–40

–35

–30

–25

–20

–15

–10

–5

–40

–30

–20

–10

VIN (dBV p-p)

QPSK

16QAM

256QAM

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