LT5568-2_15 datasheet(13/16 Pages) LINER

13 / 16 page

LT5568-2

55682f

RF OUTPUT POWER PER CARRIER (dBm)

–30

–70

–60

–10

55682 F11

–80

–90

–25

–20

–15

–5

–50

–145

–135

–155

–165

–125

DOWNLINK TEST MODEL 64 DPCH

1-CH. NOISE

3-CH. NOISE

1-CH. AltCPR

1-CH.

ACPR

3-CH. ACPR

3-CH. AltCPR

RF FREQUENCY (MHz)

896.25

–70

–50

–30

902.25

55682 F12

–90

–110

–80

–60

–40

–100

–120

–130

897.75

899.25

900.75

903.75

SPECTRUM ANALYSER NOISE FLOOR

UNCORRECTED

SPECTRUM

CORRECTED

SPECTRUM

DOWNLINK TEST

MODEL 64 DPCH

RF FREQUENCY (MHz)

894

–70

–50

–30

902

904

55682 F13

–90

–110

–80

–60

–40

–100

–120

–130

896

898

900

906

CORRECTED

SPECTRUM

UNCORRECTED

SPECTRUM

DOWNLINK

TEST

MODEL 64

DPCH

SPECTRUM ANALYSER

NOISE FLOOR

APPLICATIO S I FOR ATIO

Application Measurements

The LT5568-2 is recommended for base-station applica-

tions using various modulation formats. Figure 10 shows a

typical application. Figure 11 shows the ACPR performance

for CDMA2000 using 1- and 3-carrier modulation. Figures

12 and 13 illustrate the 1- and 3-carrier CDMA2000 RF

spectrum. To calculate ACPR, a correction is made for the

spectrum analyzer noise ﬂoor. If the output power is high,

the ACPR will be limited by the linearity performance of the

part. If the output power is low, the ACPR will be limited

by the noise performance of the part. In the middle, an

optimum ACPR is observed.

Because of the LT5568-2’s very high dynamic range, the

test equipment can limit the accuracy of the ACPR mea-

surement. See Application Note 99. Consult the factory

for advice on the ACPR measurement, if needed.

The ACPR performance is sensitive to the amplitude match

of the BBPI and BBMI (or BBPQ and BBMQ) inputs. This

is because a difference in AC current amplitude will give

rise to a difference in amplitude between the even-order

harmonic products generated in the internal V-I converter.

As a result, they will not cancel out entirely. Therefore, it

is important to keep the currents in those pins exactly

Figure 10. 850MHz to 965MHz Direct

Conversion Transmitter Application

LT5568-2

BASEBAND

GENERATOR

VCO/SYNTHESIZER

2, 4, 6, 9, 10, 12, 15, 17

V-I

I-CHANNEL

Q-CHANNEL

BALUN

8, 13

VCC

55682 F10

I-DAC

Q-DAC

RF = 850MHz

TO 965MHz

100nF

Figure 12. 1-Carrier CDMA2000 Spectrum

Figure 13. 3-Carrier CDMA2000 Spectrum

Figure 11. ACPR, AltCPR and Noise

CDMA2000 Modulation

LT5568-2 Folha de dados(PDF) 13 Page - Linear Technology

LT5568-2 Folha de dados(HTML) 13 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Folha de dados Download

Ligação URL