LT5572

13

5572f

APPLICATIO S I FOR ATIO

Application Measurements

The LT5572 is recommended for basestation applications

using various modulation formats. Figure 10 shows a typical

application. Figure 11 shows the ACPR performance for

W-CDMA using 1-, 2- or 4-channel modulation. Figures

12, 13 and 14 illustrate the 1-, 2- and 4-channel W-CDMA

VCO/SYNTHESIZER

EN

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

I-CH

Q-CH

BALUN

V-I

BASEBAND

GENERATOR

V-I

LT5572

5V

14

16

1

7

5

8, 13

5572 TA01a

11

PA

RF = 1.5GHz

TO 2.5GHz

3

I-DAC

Q-DAC

90

°

0

°

100nF

×2

Figure 10. 1.5GHz to 2.4GHz Direct Conversion Transmitter Application

Figure 11. W-CDMA ACPR, ALTCPR and Noise vs RF

Output Power at 2140MHz for 1, 2 and 4 Channels

Figure 12. 1-Channel W-CDMA Spectrum

Figure 13. 2-Channel W-CDMA Spectrum

Figure 14. 4-Channel W-CDMA Spectrum

RF OUTPUT POWER PER CARRIER (dBm)

–30

–70

–60

–10

5572 TA01b

–80

–90

–25

–20

–15

–5

–50

–145

–135

–155

–165

–125

DOWNLINK TEST

MODEL 64 DPCH

4-CH ACPR

2-CH ACPR

1-CH

ACPR

4-CH AltCPR

2-CH AltCPR

1-CH AltCPR

2-CH NOISE

4-CH NOISE

1-CH NOISE

RF FREQUENCY (GHz)

2.1275

–120

–110

–90

–80

–70

2.1375

2.1475

2.1525

–30

5572 F12

–100

2.1325

2.1425

–60

–50

–40

CORRECTED

SPECTRUM

DOWNLINK TEST

MODEL 64 DPCH

UNCORRECTED

SPECTRUM

SPECTRUM

ANALYSER

NOISE FLOOR

RF FREQUENCY (GHz)

2.125

–120

–110

–90

–80

–70

2.145

–30

5572 F13

–100

2.135

2.13

2.15

2.14

2.155

–60

–50

–40

CORRECTED

SPECTRUM

DOWNLINK

TEST MODEL

64 DPCH

UNCORRECTED SPECTRUM

SPECTRUM

ANALYSER

NOISE

FLOOR

RF FREQUENCY (GHz)

2.115

–120

–110

–90

–80

–70

2.135

2.155

2.165

–30

5572 F14

–100

2.125

2.145

–60

–50

–40

CORRECTED

SPECTRUM

DOWNLINK TEST

MODEL 64

DPCH

UNCORRECTED SPECTRUM

SPECTRUM

ANALYSER

NOISE

FLOOR

measurement. To calculate ACPR, a correction is made for

the spectrum analyzer noise floor (Application Note 99).

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 obtained.