ADL5246ACPZN-R7 datasheet(27/36 Pages) AD

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Data Sheet

ADL5246

Rev. A | Page 27 of 36

RFOUT3

RFIN3

VCC2

2.2pF

1nH

GND

ADL5246

λ2

λ3

C23

100pF

0Ω

GND

VPOS2

λ1

1pF

C21

100pF

100nH

NIC

Figure 79. AMP3 Matching Circuit at 2.6 GHz

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.

Figure 80 shows the EVM vs. the mean output power for a full

chain connection (AMP1 driving AMP2 driving AMP3)

operating at 2.2 GHz.

In general, a receiver exhibits three distinct EVM limitations vs.

received input signal power.

•

At strong signal levels, the distortion components falling in

band due to nonlinearities in the device components cause

strong degradation to EVM as signal levels increase.

•

At medium signal levels, where the signal chain behaves in a

linear manner and the signal is well above any notable noise

contributions, EVM has a tendency to reach an optimum level

determined dominantly by the quadrature accuracy 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.

–25

–20

–15

–10

–5

MEAN OUTPUT POWER (dBm)

Figure 80. EVM vs. Mean Output Power (POUT) of Full Chain Connection at

2.2 GHz, 64 QAM, 5 MSPS, α = 0.2 Root Raised Cosine Filter, PIN = −3.7 dBm

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