Q

I

Error

Vector

Magnitude Error

(IQ Error Magnitude)

Measured

Signal

Ideal (Reference)

Signal

Phase Error

(IQ Error Phase)

f

Q

I

Error

Vector

Range of

Worst-Case

Error

Ideal

Constellation

Point

Measured

Point

PC with SmartRF Studio installed

SmartRF Eval Board

and Eval Module

Spectrum Analyzer

Transmission Tests

www.ti.com

5.3

Error Vector Magnitude

Purpose: Transmission modulation accuracy is measured using error vector magnitude (EVM). EVM, as

illustrated in Figure 6 and Figure 7, is the magnitude of the phase difference as a function of time between

an ideal reference signal and the measured transmitted signal.

Figure 6. Error Vector Magnitude

Figure 7. EVM and Related Quantities

Pass Condition: See the respective standards document for specifications and pass conditions.

Test Environment: Figure 8 illustrates the setup for the EVM test.

Figure 8. Error Vector Magnitude Test Setup

Procedure:

Step 1.

Connect the instruments and test board as shown in Figure 8.

Step 2.

Set the EM to continuous TX mode with random modulated data through SmartRF Studio.

Step 3.

Measure EVM with the spectrum analyzer after setting up the instrument by following the

steps described in the tool user manual. (See Appendix A for more information.)

Example: EVM measurements on ZigBee signals using a Rohde

& Schwarz FSQ can be set up

following the instructions in Ref. 2.

Table 8. Error Vector Magnitude Test Results

Design Specification

EVM (%) at ____ kbp/s

(%)

Pass/Fail?

Freq 1 (MHz)

Freq 2 (MHz)

Freq 3 (MHz)

xx

xx

Test Results:

14

Basic RF Testing of CCxxxx Devices

SWRA370

– August 2011

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