lt5558 Linear Technology Corporation, lt5558 Datasheet - Page 13

• Manufacturer Part Number: lt5558
• Description: 600mhz To 1100mhz High Linearity Direct Quadrature Modulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
Figure 11. ACPR, ALTCPR and Noise for CDMA2000 Modulation
Figure 12. 1-Channel CDMA2000 Spectrum
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
–30
–40
–50
–60
–70
–80
–90
–30
896.25
DOWNLINK TEST
MODEL 64 DPCH
RF OUTPUT POWER PER CARRIER (dBm)
UNCORRECTED
1-CH ALTCPR
SPECTRUM
–25
SPECTRUM ANALYSER NOISE FLOOR
897.75
3-CH ALTCPR
3-CH NOISE
–20
RF FREQUENCY (MHz)
3-CH ACPR
899.25
GENERATOR
–15
BASEBAND
Figure 10. 600MHz to 1.1GHz Direct Conversion Transmitter Application
Q-DAC
I-DAC
900.75
–10
DOWNLINK TEST
MODEL 64 DPCH
EN
1-CH NOISE
1-CH ACPR
CORRECTED
SPECTRUM
902.25
2, 4, 6, 9, 10, 12, 15, 17
–5
5558 TA01b
5558 F12
903.75
0
14
16
1
7
5
–110
–120
–130
–140
–150
–160
Q-CHANNEL
V-I
V-I
I-CHANNEL
90°
0°
VCO/SYNTHESIZER
V
CC
Example: RFID Application
In Figure 15 the interface between the LTC1565 (U2, U3)
and the LT5558 is designed for RFID applications. The
LTC1565 is a seventh-order, 650kHz, continuous-time,
linear-phase, lowpass fi lter. The optimum output com-
mon-mode level of the LTC1565 is about 2.5V and the
optimum input common-mode level of the LT5558 is
around 2.1V and is temperature dependent. To adapt the
common-mode level of the LTC1565 to the LT5558, a level
shift network consisting of R1 to R6 and R11 to R16 is
used. The output common-mode level of the LTC1565 can
be adjusted by overriding the internally generated voltage
on pin 3 of the LTC1565.
8, 13
3
BALUN
–100
–110
–120
–130
Figure 13. 3-Channel CDMA2000 Spectrum
–30
–40
–50
–60
–70
–80
–90
LT5558
894
UNCORRECTED
CORRECTED SPECTRUM
SPECTRUM
11
896
SPECTRUM ANALYSER NOISE FLOOR
RF FREQUENCY (MHz)
PA
100nF
×2
898
5V
RF = 600MHz
TO 1100MHz
900
5558 F10
902
DOWNLINK
64 DPCH
MODEL
TEST
904
5558 F13
906
LT5558
13
5558fa