AD8363ACPZ-R2 datasheet(22/29 Pages) AD

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AD8363

Data Sheet

400

350

300

250

200

150

100

2800

2450

2100

1750

1400

1050

700

350

100

CLPF CAPACITANCE (nF)

RESIDUAL RIPPLE (mV)

RISE TIME (µs)

FALL TIME (µs)

Figure 49. Residual Ripple, Rise Time, and Fall Time vs. CLPF Capacitance,

Single Carrier CDMA2000 9CH SR1 Signal at 2.14 GHz with 10 dBm Pulse

Table 5 shows the recommended values of CLPF for popular

modulation schemes. For nonpulsed waveforms, increase CLPF until

the residual output noise falls below 50 mV (±0.5 dB). In each case,

the capacitor can be increased to further reduce the noise. A 10% to

90% step response to an input step is also listed. Where the

increased response time is unacceptably high, reduce CLPF, which

increases the noise on the output. Due to the random nature of the

output ripple, if it is sampled by an ADC, averaging in the digital

domain further reduces the residual noise.

Table 5 gives CLPF values to minimize noise while trying to keep

a reasonable response time. For non-pulsed type waveforms,

averaging is not required on the output. For pulsed waveforms,

the smaller the noise, the less averaging is needed on the output.

System specifications determine the necessary rise time and fall

time. For example, the suggested CLPF value for WiMAX assumes

that it is not necessary to measure the power in the preamble.

Figure 50 shows how the rise time cuts off the preamble. Note

that the power in the preamble can be easily measured; however,

the CLPF value would have to be reduced slightly, and the noise in

the main signal would increase.

CH1 500mV

M 1.00ms

A CH1

600mV

CH1 RISE

81.78µs

CH1 FALL

1.337ms

T 10.00%

Figure 50. AD8363 Output Response to a WiMAX 802.16, 64 QAM, 256

Subcarriers, 10 MHz Bandwidth Signal with CLPF = 0.027 µF

As shown in Figure 49, the fall time for the AD8363 increases

faster than the rise time with an increase in CLPF capacitance.

Some pulse-type modulation standards require a fast fall time as

well as a fast rise time, and in all cases, less output ripple is desired.

Placing an RC filter on the output reduces the ripple, according

to the frequency content of the ripple and the poles and zeros of

the filter. Using an RC output filter also changes the rise and fall

time vs. the output ripple response as compared to increasing

the CLPF capacitance.

Table 5. Recommended CLPF Values for Various Modulation Schemes

Modulation/Standard

Crest Factor (dB)

CLPF

Residual Ripple

(mV p-p)

Response Time (Rise/Fall)

10% to 90%

W-CDMA, 1Carrier, TM1-64

0.1 µF

236 μs/2.9 ms

W-CDMA, 1Carrier, TM1-64 (EVDO)

3900 pF

150

8.5 μs/100 µs

W-CDMA 4Carrier, TM1-64

0.1 µF

240 μs/2.99 ms

CDMA2000, 1Carrier, 9CH

9.1

0.1 µF

210 μs/3.1 ms

CDMA2000, 3Carrier, 9CH

0.1 µF

215 μs/3.14 ms

WiMAX 802.16 , 64 QAM, 256 Subcarriers, 10 MHz Bandwidth

0.027 µF

83 µs/1.35 ms

6C TD-SCDMA

0.01 µF

24 μs/207 μs

1C TD-SCDMA

11.4

0.01 µF

24 μs /198 μs

Rev. B | Page 22 of 29

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