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ADL5390ACPZ-WP

RF/IF Vector Multiplier

Analog Devices 

QUADRATURE MODULATOR

The ADL5390 can be used as a quadrature modulator by driving

the RF I and Q inputs (INPI and INPQ) single-ended through a

90o phase splitter to serve as the LO input. I/Q modulation is

applied to the baseband I and Q gain control inputs (IBBP/IBBM

and QBBP/QBBM). A simplified schematic is shown in Figure

38.

I DATA

LO IN

50Ω

SUM

PORT

PORT 1

QCN-12

TERM

PORT

PORT 2

90° PHASE

SPLITTER

10nF

INPI

66.5Ω

10nF

66.5Ω

INPQ

ADL5390

10nF 1

5

RFOM

RFOP

10nF

3

4

ETC1-1-13

(M/A-COM)

ROFP

Q DATA

Figure 38. Quadrature Modulator Application

Single sideband performance of a quadrature modulator is

determined by the magnitude and phase balance (compared to

a 90o offset) at the summation point of the I and Q signals.

Because the ADL5390 has matched amplifiers and mixers in

the I and Q channel, most of the single sideband performance

will be determined by the external 90o phase splitter. Good

single sideband performance can be achieved by choosing a

well-balanced 90o phase splitter. However, phase and magnitude

differences in the 90o phase splitter can be corrected by adjusting

the magnitude and phase of the I and Q data. Figure 39 shows

the performance of the ADL5390 used in conjunction with Mini-

Circuits QCN-12 90o power splitter. Figure 40 shows the single

sideband improvement as the I and Q data is adjusted in magnitude

and phase to achieve better single sideband performance.

For maximum dynamic range, the ADL5390 should be driven

as close to the output 1 dB compression point as possible. The

output power of the ADL5390 increases linearly with the RF

(LO) input power and baseband gain control input voltage until

the ADL5390 reaches compression. At the 1 dB compression

point, the lower sideband starts to increase. Figure 41 demon-

strates the output spectrum of a 3-carrier CDMA2000 signal

applied to the I/Q baseband gain control inputs. As the RF (LO)

power is increased, the relative amount of noise is reduced until

the ADL5390 goes into compression. At this point, the relative

noise increases, as shown in Figure 42.

Analog Devices has several quadrature/vector modulators that

have highly accurate integrated 90o phase splitters—AD8340,

AD8341, AD8345, AD8346, AD8349—that cover a variety of

frequency bands.

ADL5390

REF 7dBm

ATT 35dB

* RBW 3kHz

VWB 10kHz

SWT 780ms

DESIRED SIDEBAND

0 –16.20dBm

900.998397436MHz

A

1 AP

CLRWR

–10

UNDESIRED SIDEBAND

–23.27dB

1

–20 –1.996794872MHz

THIRD BASEBAND HARMONIC

–30

–37.38dB

–4.004807692MHz

LO FEEDTHROUGH

2

–40 –41.27dB

–998.397435897kHz

–50

3

4

–60

–70

-80

-90

CENTER 900MHz

700kHz/

SPAN 7MHz

Figure 39. SSB Quadrature Modulator Result Using External 90° Phase Splitter,

RF PIN = −15 dBm, VIBB = VQBB = 0.5 V

(With Reference to a Common-Mode Voltage of 0.5 V)

REF 7dBm

ATT 35dB

* RBW 3kHz

VWB 10kHz

SWT 780ms

DESIRED SIDEBAND

0 –16.78dBm

A

900.998397436MHz

1 AP

CLRWR

–10

UNDESIRED SIDEBAND

–51.81dB

1

–20 –1.996794872MHz

THIRD BASEBAND HARMONIC

–30

–38.45dB

–4.004807692MHz

LO FEEDTHROUGH

–40 –41.49dB

–998.397435897kHz

–50 3

4

–60

2

–70

–80

–90

CENTER 900MHz

700kHz/

SPAN 7MHz

Figure 40. SSB Modulator Applications with Gain and Phase Errors Corrected,

RF Pin = −15 dBm, VIBB = VQBB = 0.5 V (With Reference to a Common-Mode

Voltage of 0.5 V), I/Q Phase Offset by 3o, and Magnitude Offset by 0.5 V

Rev. 0 | Page 17 of 24

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