ADL5387ACPZ-R71 datasheet(17/28 Pages) AD

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ADL5387

Rev. 0 | Page 17 of 28

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

would have all constellation points at the ideal locations; however,

various imperfections in the implementation (such as carrier

leakage, phase noise, and quadrature error) cause the actual

constellation points to deviate from the ideal locations.

The ADL5387 shows excellent EVM performance for various

modulation schemes. Figure 51 shows typical EVM performance

over input power range for a point-to-point application with

16 QAM modulation schemes and zero-IF baseband. The

differential dc offsets on the ADL5387 are in the order of a

few mV. However, ac coupling the baseband outputs with 10 μF

capacitors helps to eliminate dc offsets and enhances EVM

performance. With a 10 MHz BW signal, 10 μF ac coupling

capacitors with the 500 Ω differential load results in a high-pass

corner frequency of ~64 Hz which absorbs an insignificant

amount of modulated signal energy from the baseband signal.

By using ac coupling capacitors at the baseband outputs, the dc

offset effects, which can limit dynamic range at low input power

levels, can be eliminated.

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Figure 51. RF = 140 MHz, IF = 0 Hz, EVM vs. Input Power for a 16 QAM

10 Msym/s Signal (AC-Coupled Baseband Outputs)

Figure 52 shows the EVM performance of the ADL5387 when

ac-coupled, with an IEEE 802.16e WiMAX signal.

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Figure 52. RF = 750MHz MHz, IF = 0 Hz, EVM vs. Input Power for a 16 QAM

10 MHz Bandwidth Mobile WiMAX Signal (AC-Coupled Baseband Outputs)

Figure 53 exhibits the zero IF EVM performance of a WCDMA

signal over a wide RF input power range.

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INPUT POWER (dBm)

Figure 53. RF = 1950 MHz, IF = 0 Hz, EVM vs. Input Power for a WCDMA

(AC-Coupled Baseband Outputs)

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