adl5387 Analog Devices, Inc., adl5387 Datasheet - Page 17

• Manufacturer Part Number: adl5387
• Description: 50 Mhz To 2 Ghz Quadrature Demodulator
• Manufacturer: Analog Devices, Inc.

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.
Figure 51. RF = 140 MHz, IF = 0 Hz, EVM vs. Input Power for a 16 QAM
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Figure 52 shows the EVM performance of the ADL5387 when
ac-coupled, with an IEEE 802.16e WiMAX signal.
Figure 53 exhibits the zero IF EVM performance of a WCDMA
signal over a wide RF input power range.
10 MHz Bandwidth Mobile WiMAX Signal (AC-Coupled Baseband Outputs)
Figure 52. RF = 750MHz MHz, IF = 0 Hz, EVM vs. Input Power for a 16 QAM
Figure 53. RF = 1950 MHz, IF = 0 Hz, EVM vs. Input Power for a WCDMA
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ADL5387
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