ADRF6807ACPZ-R7 datasheet(24/36 Pages) AD

24 / 36 page

ADRF6807

Data Sheet

Rev. B | Page 24 of 36

EVM MEASUREMENTS

Figure 42 shows the excellent EVM of the ADRF6807 being better

than −40 dB over an RF input range of about 40 dB for a 4 QAM

modulated signal, at a 5 MHz symbol rate and at a 0 Hz IF. The

roll-off, or alpha, of the pulse shaping filter was set to 0.35.

The reported RF input power is the power integrated across

the bandwidth of

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.

BW = (1 + α) × (Symbol Rate)

EVM was tested for both power modes: low power mode disabled

(LPEN = 0) and low power mode enabled (LPEN = 1). When

the low power mode is enabled, the EVM is better at lower RF

input signal levels due to less noise while running in the low

power mode.

In general, a demodulator exhibits three distinct EVM limitations

vs. received input signal power. As signal power increases, the

distortion components increase. At large signal levels, where the

distortion components due to the harmonic nonlinearities in the

device are falling in-band, EVM degrades as signal levels increase.

At medium signal levels, where the demodulator behaves in a

linear manner and the signal is well above any notable noise

contributions, the EVM has a tendency to reach an optimal level

determined dominantly by either quadrature accuracy and I/Q

gain match of the demodulator or the precision of the test

equipment. As signal levels decrease, such that the 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.

–50

–35

–45

–30

–40

–25

–20

–15

–10

–5

RF INPUT POWER (dBm)

LPEN = 1

LPEN = 0

–60

–50

–40

–30

–20

–10

The basic test setup for testing the EVM of the ADRF6807

consisted of an Agilent E4438C, which was used as a signal source.

The 900 MHz modulated signal was driven single ended into

the RFIN SMA connector of the ADRF6807 evaluation board.

The IQ baseband outputs were taken differentially into a pair of

AD8130 difference amplifiers to convert the differential signals

to single ended. The output impedance that the ADRF6807 drove

was set to 450 Ω differential. The single-ended I and Q signals

were then sampled by an Agilent DSO7104B oscilloscope. The

Agilent 89400 VSA software was used to calculate the EVM

of the signal. The signal source that was used for the reference

input was a Wenzel 100 MHz quarts oscillator set at an amp-

tude of 1 V p-p. The reference path was set to a divide-by-four,

thus making the PFD frequency 25 MHz.

Figure 42. EVM Measurements at 900 MHz 4 QAM, Symbol Rate = 5 MHz,

Baseband Frequency = 0 Hz IF

ADRF6807ACPZ-R7 数据表(PDF) 24 Page - Analog Devices

ADRF6807ACPZ-R7 数据表(HTML) 24 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

数据表下载