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ADL5371 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADL5371
Beschreibung 500 MHz to 1500 MHz Quadrature Modulator
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 20 Seiten
ADL5371 Datasheet, Funktion
FEATURES
Output frequency range: 500 MHz to 1500 MHz
Modulation bandwidth: >500 MHz (3 dB)
1 dB output compression: 14.4 dBm @ 900 MHz
Noise floor: −158.6 dBm/Hz @ 915 MHz
Sideband suppression: −55 dBc @ 900 MHz
Carrier feedthrough: −50 dBm @ 900 MHz
www.DataSheeSt4inUg.cleomsupply: 4.75 V to 5.25 V
24-lead LFCSP
APPLICATIONS
Cellular communication systems at 900 MHz
CDMA2000/GSM
WiMAX/broadband wireless access systems
Cable communication equipment
Satellite modems
GENERAL DESCRIPTION
The ADL5371 is a member of the fixed-gain quadrature modulator
(F-MOD) family designed for use from 500 MHz to 1500 MHz.
Its excellent phase accuracy and amplitude balance enable high
performance intermediate frequency or direct radio frequency
modulation for communication systems.
The ADL5371 provides a >500 MHz, 3 dB baseband bandwidth,
making it ideally suited for use in broadband zero IF or low IF-
to-RF applications and in broadband digital predistortion
transmitters.
500 MHz to 1500 MHz
Quadrature Modulator
ADL5371
FUNCTIONAL BLOCK DIAGRAM
IBBP
IBBN
LOIP
LOIN
QUADRATURE
PHASE
SPLITTER
VOUT
QBBN
QBBP
Figure 1.
The ADL5371 accepts two differential baseband inputs and
a single-ended local oscillator (LO) and generates a single-
ended output.
The ADL5371 is fabricated using the Analog Devices, Inc.
advanced silicon-germanium bipolar process. It is available in a
24-lead, exposed-paddle, Pb-free, LFCSP. Performance is specified
over a −40°C to +85°C temperature range. A Pb-free evaluation
board is available.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2007 Analog Devices, Inc. All rights reserved.






ADL5371 Datasheet, Funktion
ADL5371
TYPICAL PERFORMANCE CHARACTERISTICS
VS = 5 V; TA = 25°C; LO = 0 dBm single-ended; baseband I/Q amplitude = 1.4 V p-p differential sine waves in quadrature with a 500 mV
dc bias; baseband I/Q frequency (fBB) = 1 MHz, unless otherwise noted.
10 16
9
TA = –40°C
8
15
TA = –40°C
14
7 13
6
5 TA = +85°C
12
TA = +85°C
11
4
www.DataSheet4U3.com
TA = +25°C
10 TA = +25°C
9
28
17
0
500 600 700 800 900 1000 1100 1200 1300 1400 1500
LO FREQUENCY (MHz)
Figure 3. Single Sideband (SSB) Output Power (POUT) vs.
LO Frequency (fLO) and Temperature
6
500 600 700 800 900 1000 1100 1200 1300 1400 1500
LO FREQUENCY (MHz)
Figure 6. SSB Output 1 dB Compression Point (OP1dB) vs. fLO and Temperature
10
9
VS = 5.0V
8
7
6
5 VS = 4.75V VS = 5.25V
4
3
2
1
0
500 600 700 800 900 1000 1100 1200 1300 1400 1500
LO FREQUENCY (MHz)
Figure 4. Single Sideband (SSB) Output Power (POUT) vs.
LO Frequency (fLO) and Supply
16
VS = 5.0V
15
14
13 VS = 5.25V
12
VS = 4.75V
11
10
9
8
7
6
500 600 700 800 900 1000 1100 1200 1300 1400 1500
LO FREQUENCY (MHz)
Figure 7. SSB Output 1 dB Compression Point (OP1dB) vs. fLO and Supply
5 90
120 60
0
–5
1 10 100 1000
BASEBAND FREQUENCY (MHz)
Figure 5. I/Q Input Bandwidth Normalized to
Gain @ 1 MHz (fLO = 900 MHz)
150 500MHz
30
S11 OF LOIP
S22 OF OUTPUT
180
210
1500MHz
1500MHz
500MHz
0
330
240 300
270
Figure 8. Smith Chart of LOIP S11 and VOUT S22
(fLO from 500 MHz to 1500 MHz)
Rev. 0 | Page 6 of 20

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ADL5371 pdf, datenblatt
ADL5371
OPTIMIZATION
The carrier feedthrough and sideband suppression performance
of the ADL5371 can be improved by using optimization
techniques.
Carrier Feedthrough Nulling
Carrier feedthrough results from minute dc offsets that occur
between each of the differential baseband inputs. In an ideal
modulator, the quantities (VIOPP − VIOPN) and (VQOPP − VQOPN)
are equal to zero, which results in no carrier feedthrough. In a real
modulator, those two quantities are nonzero, and, when mixed
with the LO, they result in a finite amount of carrier feedthrough.
www.DataTSheeAt4DUL.5co37m1 is designed to provide a minimal amount of carrier
feedthrough. Should even lower carrier feedthrough levels be
required, minor adjustments can be made to the (VIOPP − VIOPN)
and (VQOPP − VQOPN) offsets. The I-channel offset is held constant
while the Q-channel offset is varied until a minimum carrier
feedthrough level is obtained. The Q-channel offset required to
achieve this minimum is held constant, while the offset on the I-
channel is adjusted until a new minimum is reached. Through
two iterations of this process, the carrier feedthrough can be
reduced to as low as the output noise. The ability to null is
sometimes limited by the resolution of the offset adjustment.
Figure 24 shows the relationship of carrier feedthrough vs. dc
offset as null.
–60
–64
–68
–72
–76
–80
–84
–88
–300 –240 –180 –120 –60 0
60 120 180 240 300
VP – VN OFFSET (µV)
Figure 24. Typical Carrier Feedthrough vs. DC Offset Voltage
Note that throughout the nulling process, the dc bias for the
baseband inputs remains at 500 mV. When no offset is applied,
VIOPP = VIOPN = 500 mV, or
VIOPP VIOPN = VIOS = 0 V
When an offset of +VIOS is applied to the I-channel inputs,
VIOPP = 500 mV + VIOS/2, and
VIOPN = 500 mV − VIOS/2, such that
VIOPP VIOPN = VIOS
The same applies to the Q channel inputs.
It is often desirable to perform a one-time carrier null calibra-
tion. This is usually performed at a single frequency. Figure 25
shows how carrier feedthrough varies with LO frequency over a
range of ±50 MHz on either side of a null at 940 MHz.
–40
–45
–50
–55
–60
–65
–70
–75
–80
–85
–90
890 900 910 920 930 940 950 960 970 980 990
LO FREQUENCY (MHz)
Figure 25. Carrier Feedthrough vs. Frequency After Nulling at 940 MHz
Sideband Suppression Optimization
Sideband suppression results from relative gain and relative
phase offsets between the I/Q channels and can be suppressed
through adjustments to those two parameters. Figure 26
illustrates how sideband suppression is affected by the gain and
phase imbalances.
0
–10
2.5dB
–20 1.25dB
–30 0.5dB
0.25dB
–40 0.125dB
–50 0.05dB
0.025dB
–60 0.0125dB
–70
0dB
–80
–90
0.01
0.1 1 10
PHASE ERROR (Degrees)
100
Figure 26. Sideband Suppression vs. Quadrature Phase Error for Various
Quadrature Amplitude Offsets
Figure 26 underlines the fact that adjusting only one parameter
improves the sideband suppression only to a point, unless the
other parameter is also adjusted. For example, if the amplitude
offset is 0.25 dB, improving the phase imbalance more than 1°
does not yield any improvement in the sideband suppression. For
optimum sideband suppression, an iterative adjustment
between phase and amplitude is required.
The sideband suppression nulling can be performed either through
adjusting the gain for each channel or through the modification
of the phase and gain of the digital data coming from the digital
signal processor.
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