Quad I/Q Demodulator And Phase Shifter
AD8339
Preliminary Technical Data
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Quad Integrated I/Q Demodulator
16 Phase Select on each Output (22.5° per step)
Quadrature Demodulation Accuracy
Phase Accuracy ±1°
RF1
2
0
φ
φ
I1
BIAS
90
Q1
Amplitude Balance ±0.25 dB
Bandwidth
90
0
φ
φ
Q2
I2
4LO: LF – 100 MHz; RF: LF - 25 MHz
Baseband: determined by external filtering
Output Dynamic Range 158 dB (1 Hz Bandwidth)
LO Drive > –10 dBm (50 Ω); 200 mVpp
Supply: ±5 V
RSET
RF2
4
2
2
SCLK
SDI
SDO
Serial
Interface
/4
4xLO
RF3
CSB
Power Consumption 73 mW/channel (290 mW total)
Power Down via SPI (Each Channel and Complete Chip)
4
2
0
φ
I3
90
φ
VPOS
Q3
APPLICATIONS
COMM
VNEG
Medical Imaging (CW Ultrasound Beamforming)
Phased Array Systems
Radar
90
0
φ
φ
Q4
I4
2
Adaptive Antennas
Communication Receivers
RF4
Figure 1. Functional Block Diagram
GENERAL DESCRIPTION
Q signals, will need to be converted to a voltage by a high dynamic
range current-to-voltage (I-V) converter. A good choice for this
transimpedance amplifier is the AD8021 because of its low noise.
Following the current summation the combined signal is presented to
a high resolution AD converter (ADC) like the AD7665 (16b/570
ksps).
The AD8339 is a Quad I/Q demodulator intended to be driven by a
low noise preamplifier with differential outputs; it is optimized for the
LNA in the AD8332/4/5 family of VGAs. The part consists of four
identical I/Q demodulators with a 4x local oscillator (LO) input that
divides this signal and generates the necessary 0° and 90° phases of
the internal LO that drive the mixers. The four I/Q demodulators can
be used independently of each other (assuming that a common LO is
acceptable) since each has a separate RF input.
An SPI compatible serial interface is provided for ease of
programming the phase of each channel; the interface allows daisy-
chaining by shifting the data through each chip from SDI to SDO. The
SPI also allows for power down of each individual channel and the
complete chip. During power down the serial interface remains active
so that the device can be programmed again.
The major application is continuous wave (CW) analog beamforming
in ultrasound. Since in a beamforming application the outputs of
many channels are summed coherently, the signals need to be phase
aligned. A reset pin for the LO divider that synchronizes multiple ICs
to start in the same quadrant is provided. Sixteen discrete phase
rotations in 22.5° increments can be selected independently for each
channel. For example, if CH1 is used as a reference and CH2 has an
I/Q phase lead of 45°, then by choosing the correct code one can
phase align CH2 with CH1.
The dynamic range is >158 dB (1 Hz BW) at the I and Q outputs.
Note that the following transimpedance amplifier is an important
element in maintaining this dynamic range and attention needs to be
paid to component selection.
The AD8339 will be available in a 6x6 mm 40 pin LFCSP for the
industrial temperature range of -40°C to +85°C.
The mixer outputs are provided in current form so that they can be
easily summed. The summed current outputs, one each for the I and
Rev. PrA - 12/19/06
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 companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.326.8703
www.analog.com
© 2007 Analog Devices, Inc. All rights reserved.
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