ADL5382

Rev. 0 | Page 16 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 magnitude

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

constellation points to deviate from the ideal locations.

The ADL5382 shows excellent EVM performance for various

modulation schemes. Figure 45 shows the EVM performance of

the ADL5382 with a 16 QAM, 200 kHz low IF.

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RF INPUT POWER (dBm)

Figure 45. EVM, RF = 900 MHz, IF = 200 kHz vs.

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

Figure 46 shows the zero-IF EVM performance of a 10 MHz

IEEE 802.16e WiMAX signal through the ADL5382. The

differential dc offsets on the ADL5382 are in the order of a few

millivolts. However, ac coupling the baseband outputs with

10 μF capacitors eliminates 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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RF INPUT POWER (dBm)

Figure 46. EVM, RF = 2.6 GHz, IF = 0 Hz vs. RF Input Power for a 16 QAM

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

Figure 47 exhibits multiple W-CDMA low-IF EVM

performance curves over a wide RF input power range into the

ADL5382. In the case of zero-IF, the noise contribution by the

vector signal analyzer becomes predominant at lower power

levels, making it difficult to measure SNR accurately.

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0Hz

7.5MHz

5MHz

RF INPUT POWER (dBm)

2.5MHz

Figure 47. EVM, RF = 1900 MHz, IF = 0 Hz, 2.5 MHz, 5 MHz, and 7.5 MHz vs. RF

Input Power for a W-CDMA Signal (AC-Coupled Baseband Outputs)