ADL5380ACPZ-R7 datasheet(24/36 Pages) AD

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ADL5380

Rev. 0 | Page 24 of 36

RF INPUT

The RF inputs have a differential input impedance of approximately

50 Ω. For optimum performance, drive the RF port differentially

through a balun. The recommended balun for each performance

level includes the following:

•

Up to 3 GHz is the Mini-Circuits TC1-1-13.

•

From 3 GHz to 4 GHz is the Johanson Technology

3600BL14M050.

•

From 4.9 GHz to 6 GHz is the Johanson Technology

5400BL15B050.

AC couple the RF inputs to the device with 100 pF capacitors.

Figure 79 shows the RF input configuration.

RF INPUT

RFIN

BALUN

RFIP

100pF

Figure 79. RF Input

The differential RF port return loss is characterized, as shown

in Figure 80.

0.51.01.52.02.53.03.54.04.55.05.56.0

–28

–26

–24

–22

–20

–18

–16

–14

–12

–10

–30

–8

RF FREQUENCY (GHz)

Figure 80. Differential RF Port Return Loss

BASEBAND OUTPUTS

The baseband outputs QHI, QLO, IHI, and ILO are fixed

impedance ports. Each baseband pair has a 50 Ω differential

output impedance. The outputs can be presented with differential

loads as low as 200 Ω (with some degradation in gain) or high

impedance differential loads (500 Ω or greater impedance yields

the same excellent linearity) that is typical of an ADC. The TCM9-1

9:1 balun converts the differential IF output to a single-ended

output. When loaded with 50 Ω, this balun presents a 450 Ω

load to the device. The typical maximum linear voltage swing for

these outputs is 2 V p-p differential. The output 3 dB bandwidth

is 390 MHz. Figure 81 shows the baseband output configuration.

IHI

ILO

QHI

QLO

ADL5380

Figure 81. Baseband Output Configuration

ERROR VECTOR MAGNITUDE (EVM) PERFORMANCE

EVM is a measure used to quantify the performance of a digital

radio transmitter or receiver. A signal received by a receiver has all

constellation points at their ideal locations; however, various

imperfections in the implementation (such as magnitude

imbalance, noise floor, and phase imbalance) cause the actual

constellation points to deviate from their ideal locations.

In general, a demodulator exhibits three distinct EVM

limitations vs. received input signal power. At strong signal

levels, the distortion components falling in-band due to non-

linearities in the device cause strong degradation to EVM

as signal levels increase. At medium signal levels, where the

demodulator behaves in a linear manner and the signal is well

above any notable noise contributions, the EVM has a tendency to

reach an optimum level determined dominantly by the quadrature

accuracy of the demodulator and the precision of the test equipment.

As signal levels decrease, such that noise is a major contribution,

the EVM performance vs. the signal level exhibits a decibel-for-

decibel degradation with decreasing signal level. At lower signal

levels, where noise proves to be the dominant limitation, the

decibel EVM proves to be directly proportional to the SNR.

The ADL5380 shows excellent EVM performance for various

modulation schemes. Figure 82 shows the EVM performance of

the ADL5380 with a 16 QAM, 200 kHz low IF.

–50

–45

–40

–35

–30

–25

–20

–15

–10

–5

–90

–70

–50

–30

–10

RF INPUT POWER (dBm)

Figure 82. EVM, RF = 900 MHz, IF = 200 kHz vs.

RF Input Power for a 16 QAM 160ksym/s Signal

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