Analog Devices AD8341 Service Manual

1.5 GHz to 2.4 GHz

FEATURES

Cartesian amplitude and phase modulation

1.5 GHz to 2.4 GHz frequency range
Continuous magnitude control of −4.5 dB to −34.5 dB
Continuous phase control of 0° to 360°
Output third-order intercept 17.5 dBm
Output 1 dB compression point 8.5 dBm
Output noise floor −150.5 dBm/Hz @ full gain
Adjustable modulation bandwidth up to 230 MHz
Fast output power disable

4.75 V to 5.25 V single-supply voltage

APPLICATIONS

RF PA linearization/RF predistortion
Amplitude and phase modulation
Variable attenuators and phase shifters
CDMA2000, WCDMA, GSM/EDGE linear power amplifiers
Smart antennas

GENERAL DESCRIPTION

The AD8341 vector modulator performs arbitrary amplitude
and phase modulation of an RF signal. Since the RF signal path
is linear, the original modulation is preserved. This part can be
used as a general-purpose RF modulator, a variable attenu­ator/phase shifter, or a remodulator. The amplitude can be
controlled from a maximum of −4.5 dB to less than −34.5 dB,
and the phase can be shifted continuously over the entire 360°
range. For maximum gain, the AD8341 delivers an OP1dB of

8.5 dBm, an OIP3 of 17.5 dBm, and an output noise floor of

−150.5 dBm/Hz, independent of phase. It operates over a
frequency range of 1.5 GHz to 2.4 GHz.

The baseband inputs in Cartesian I and Q format control the
amplitude and phase modulation imposed on the RF input
signal. Both I and Q inputs are dc-coupled with a ±500 mV
differential full-scale range. The maximum modulation band­width is 230 MHz, which can be reduced by adding external
capacitors to limit the noise bandwidth on the control lines.

RF Vector Modulator

AD8341

FUNCTIONAL BLOCK DIAGRAM

VPRF

90°

RFIP

RFIM

0°

CMOP

Figure 1.

Both the RF inputs and outputs can be used differentially or
single-ended and must be ac-coupled. The RF input and output
impedances are nominally 50 Ω over the operating frequency
range. The DSOP pin allows the output stage to be disabled
quickly in order to protect subsequent stages from overdrive.
The AD8341 operates off supply voltages from 4.75 V to 5.25 V
while consuming approximately 125 mA.

The AD8341 is fabricated on Analog Devices’ proprietary, high
performance 25 GHz SOI complementary bipolar IC process. It
is available in a 24-lead, Pb-free LFCSP package and operates
over a −40°C to +85°C temperature range. Evaluation boards
are available.

VPS2QBBMQBBP

RFOP

RFOM

DSOPIBBMIBBP

04700-001

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. Trademarks and
registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

www.analog.com

AD8341

TABLE OF CONTENTS

Specifications..................................................................................... 3

Applications..................................................................................... 12

Absolute Maximum Ratings............................................................ 4

ESD Caution.................................................................................. 4

Pin Configuration and Function Descriptions............................. 5

Typical Performance Characteristics............................................. 6

Theory of Operation ...................................................................... 10

RF Quadrature Generator .........................................................10

I-Q Attenuators and Baseband Amplifiers .............................. 11

Output Amplifier........................................................................ 11

Noise and Distortion.................................................................. 11

Gain and Phase Accuracy.......................................................... 11

RF Frequency Range .................................................................. 11

REVISION HISTORY

7/04—Revision 0: Initial Version

Using the AD8341 ...................................................................... 12

RF Input and Matching ............................................................. 12

RF Output and Matching .......................................................... 13

Driving the I-Q Baseband Controls......................................... 13

Interfacing to High Speed DACs.............................................. 14

CDMA2000 Application............................................................ 14

WCDMA Application ................................................................ 15

Evaluation Board ............................................................................ 17

Outline Dimensions....................................................................... 20

Ordering Guide .......................................................................... 20

Rev. 0 | Page 2 of 20

AD8341

SPECIFICATIONS

VS = 5 V, TA = 25°C, ZO = 50 Ω, f = 1.9 GHz, single-ended, ac-coupled source drive to RFIP through 1.2 nH series inductor, RFIM
ac-coupled through 1.2 nH series inductor to common, differential-to-single-ended conversion at output using 1:1 balun.

Table 1.

Parameter Conditions Min Typ Max Unit

OVERALL FUNCTION

Frequency Range 1.5 2.4 GHz
Maximum Gain Maximum gain setpoint for all phase setpoints −4.5 dB
Minimum Gain

= V

V

BBI

= 0 V differential

BBQ

(at recommended common-mode level)
Gain Control Range Relative to maximum gain 30 dB
Phase Control Range Over 30 dB control range 360 Degrees
Gain Flatness Over any 60 MHz bandwidth 0.5 dB
Group Delay Flatness Over any 60 MHz bandwidth 50 ps

RF INPUT STAGE RFIM, RFIP (Pins 21 and 22)

Input Return Loss From RFIP to CMRF (with 1.2 nH series inductors) 12 dB

CARTESIAN CONTROL INTERFACE (I AND Q) IBBP, IBBM, QBBP, QBBM (Pins 16, 15, 3, 4)

Gain Scaling 2 1/V
Modulation Bandwidth 500 mV p-p, sinusoidal baseband input single-ended 230 MHz
Second Harmonic Distortion 500 mV p-p, 1 MHz, sinusoidal baseband input differential 41 dBc
Third Harmonic Distortion 500 mV p-p, 1 MHz, sinusoidal baseband input differential 47 dBc
Step Response

For gain setpoint from 0.1 to 0.9

(V

BBP

= 0.5 V, V

= 0.55 V to 0.95 V)

BBM

For gain setpoint from 0.9 to 0.1

(V

= 0.5 V, V

BBP

= 0.95 V to 0.55 V)

BBM

Recommended Common-Mode Level 0.5 V

RF OUTPUT STAGE RFOP, RFOM (Pins 9, 10)

Output Return Loss Measured through balun 7.5 dB

f = 1.9 GHz

Gain Maximum gain setpoint −4.5 dB
Output Noise Floor Maximum gain setpoint, no input −150.5 dBm/Hz
P

= 0 dBm, frequency offset = 20 MHz −149 dBm/Hz

IN

Output IP3 f1 = 1900 MHz, f2 = 1897.5 MHz, maximum gain setpoint 17.5 dBm
Adjacent Channel Power

CDMA2000, single carrier, P

= -4 dBm,

OUT

maximum gain, phase setpoint = 45° (See Figure 35)
Output 1 dB Compression Point Maximum gain 8.5 dBm

POWER SUPPLY

VPS2 (Pins 5, 6, and 14), VPRF (Pins 19 and 24),

RFOP, RFOM (Pins 9 and 10)
Positive Supply Voltage 4.75 5 5.25 V
Total Supply Current Includes load current 105 125 145 mA

OUTPUT DISABLE DSOP (Pin 13)

Disable Threshold (See Figure 24) Vs/2 V
Attenuation DSOP = 5 V 33 dB
Enable Response Time

Delay following high-to-low transition until

RF output amplitude is within 10% of final value.
Disable Response Time

Delay following low-to-high transition until

device produces full attenuation

−34.5 dB

45 ns

45 ns

−76 dBm

30 ns

15 ns

Rev. 0 | Page 3 of 20

AD8341

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameters Rating

Supply Voltage VPRF, VPS2 5.5 V
DSOP 5.5 V
IBBP, IBBM, QBBP, QBBM 2.5 V
RFOP, RFOM 5.5V
RF Input Power at Maximum Gain 13 dBm, re: 50 Ω

(RFIP or RFIM, Single-Ended Drive)

Equivalent Voltage 2.8 V p-p
Internal Power Dissipation 825 mW
θJA (With Pad Soldered to Board) 59 °C/W
Maximum Junction Temperature 125°C
Operating Temperature Range −40°C to +85°C
Storage Temperature Range −65°C to +150°C
Lead Temperature Range (Soldering 60 sec) 300°C

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the
human body and test equipment and can discharge without detection. Although this product features proprie­tary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic
discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of
functionality.

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

Rev. 0 | Page 4 of 20

AD8341

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

VPRF

CMRF

RFIP

RFIM

CMRF

2322212019

PIN 1
INDICATOR

11

10

RFOP

RFOM

CMOP

CMOP

VPRF

12

CMOP

18
17
16
15
14
13

IFLP
IFLM
IBBP
IBBM
VPS2
DSOP

04700-002

24

QFLP

1

QFLM

2

QBBP

3
4
5
6

AD8341

TOP VIEW

(Not to Scale)

789

CMOP

QBBM

VPS2
VPS2

Figure 2. 24-Lead Lead Frame Chip Scale Package (LFCSP)

Table 3. Pin Function Descriptions

Pin No. Mnemonic Function

1, 2 QFLP, QFLM

Q Baseband Input Filter Pins. Connect optional capacitor to reduce Q baseband channel low-pass

corner frequency.
3, 4 QBBP, QBBM Q Channel Differential Baseband Inputs.
5, 6, 14, 19, 24 VPS2, VPRF Positive Supply Voltage. 4.75 V − 5.25 V.
7, 8, 11, 12, 20, 23 CMOP, CMRF Device Common. Connect via lowest possible impedance to external circuit common.
9, 10 RFOP, RFOM Differential RF Outputs. Must be ac-coupled. Differential impedance 50 Ω nominal.
13 DSOP Output disable. Pull high to disable output stage.
15, 16 IBBM, IBBP I Channel Differential Baseband Inputs.
17, 18 IFLM, IFLP

I Baseband Input Filter Pins. Connect optional capacitor to reduce I baseband channel low-pass

corner frequency.
21, 22 RFIM, RFIP Differential RF Inputs. Must be ac-coupled. Differential impedance 50 Ω nominal.

Rev. 0 | Page 5 of 20

AD8341

TYPICAL PERFORMANCE CHARACTERISTICS

0

–5

PHASE SETPOINT = 270°

–10

–15

–20

GAIN (dB)

–25

–30

–35

–40

0.1

0 0.3 0.5 0.9 1.00.80.70.60.40.2

Figure 3. Gain Magnitude vs. Gain Setpoint at Different

Phase Setpoints, RF Frequency = 1900 MHz

6

PHASE SETPOINT = 315°

5
4

PHASE SETPOINT = 270°

3
2
1

0
–1
–2
–3
–4
–5

GAIN CONFORMANCE ERROR (dB)

–6
–7
–8

PHASE SETPOINT = 0°

PHASE SETPOINT = 90°

PHASE SETPOINT = 180°

PHASE SETPOINT = 135°

0 0.1 1.00.2 0.3 0.4 0.5 0.6 0.7 0.8

Figure 4. Gain Conformance Error vs. Gain Setpoint at

Different Phase Setpoints, RF Frequency = 1900 MHz

–2
–4
–6

–8
–10
–12
–14
–16

GAIN (dB)

–18
–20
–22
–24
–26
–28

45

Figure 5. Gain Magnitude vs. Phase Setpoint at Different

Gain Setpoints, RF Frequency = 1900 MHz

PHASE SETPOINT = 0°

PHASE SETPOINT = 180°

PHASE SETPOINT = 90°

GAIN SETPOINT

PHASE SETPOINT = 45°

PHASE SETPOINT = 225°

GAIN SETPOINT

GAIN SETPOINT = 1.0

GAIN SETPOINT = 0.5

GAIN SETPOINT = 0.25

GAIN SETPOINT = 0.1

PHASE SETPOINT (Degrees)

04700-003

04700-004

0.9

315270 36018090 135 2250

04700-005

1.0

0.5
0

–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5

GAIN CONFORMANCE ERROR (dB)

–4.0
–4.5

GAIN SETPOINT = 0.5

GAIN SETPOINT = 0.25

45 315270 36018090 135 2250

GAIN SETPOINT = 1.0

GAIN SETPOINT = 0.1

PHASE SETPOINT (Degrees)

Figure 6. Gain Conformance Error vs. Phase Setpoint at

Different Gain Setpoints, RF Frequency = 1900 MHz

360

315

270

225

180

135

PHASE (Degrees)

90

45

0

GAIN SETPOINT = 0.1

0 3603152702251801359045

GAIN SETPOINT = 0.25

GAIN SETPOINT = 0.5

GAIN SETPOINT = 1.0

PHASE SETPOINT (Degrees)

Figure 7. Phase vs. Phase Setpoint at

Different Gain Setpoints, RF Frequency = 1900 MHz

25

20

15

10

5

0

PHASE ERROR (Degrees)

–5

–10

–15

0 45 90 135 360180 225 270 315

GAIN SETPOINT = 0.1

GAIN SETPOINT = 0.25

GAIN SETPOINT = 0.5

PHASE SETPOINT (Degrees)

GAIN SETPOINT = 1.0

Figure 8. Phase Error vs. Phase Setpoint at Different Gain Setpoints,

RF Frequency = 1900 MHz

04700-006

04700-007

04700-008

Rev. 0 | Page 6 of 20