AD8333 Datasheet, PDF (1/28 Pages) Analog Devices – DC to 50 MHz, Dual I/Q Demodulator and Phase Shifter

DC to 50 MHz,
Dual I/Q Demodulator and Phase Shifter
AD8333
FEATURES
Dual integrated I/Q demodulator
16 phase select on each output (22.5° per step)
Quadrature demodulation accuracy
Phase accuracy: ±0.1°
Amplitude balance: ±0.05 dB
Bandwidth
4 LO: 100 kHz to 200 MHz
RF: dc to 50 MHz
Baseband: determined by external filtering
Output dynamic range: 161 dB/Hz
LO drive > 0 dBm (50 Ω); 4 LO > 1 MHz
Supply: ±5 V
Power consumption: 190 mW/channel (380 mW total)
Power down
APPLICATIONS
Medical imaging (CW ultrasound beamforming)
Phased array systems (radar and adaptive antennas)
Communication receivers
GENERAL DESCRIPTION
The AD8333 is a dual-phase shifter and I/Q demodulator that
enables coherent summing and phase alignment of multiple
analog data channels. It is the first solid-state device suitable for
beamformer circuits, such as those used in high performance
medical ultrasound equipment featuring CW Doppler. The RF
inputs interface directly with the outputs of the dual-channel,
low noise preamplifiers included in the AD8332.
A divide-by-four circuit generates the internal 0° and 90° phases
of the LO that drive the mixers of a pair of matched I/Q
demodulators.
The AD8333 can be applied as a major element in analog
beamformer circuits in medical ultrasound equipment.
The AD8333 features an asynchronous reset pin. When used in
arrays, the reset pin sets all the LO dividers in the same state.
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 the RF signal applied to CH2 has an I/Q
phase lead of 45°, then the user can phase align CH2 with CH1
by choosing the correct code.
Rev. A
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FUNCTIONAL BLOCK DIAGRAM
CH1
PHASE
SELECT
CH1 ⁺
RF _–
0°
AD8333
90°
LOC
÷4
OSC
90°
Φ
I1
Φ
Q1
Φ
Q2
CH2 ⁺
RF
–
0°
Φ
I2
Figure 1.
CH2
PHASE
SELECT
Phase shift is defined by the output of one channel relative to
another. For example, if the code of Channel 1 is adjusted to
0000 and that of Channel 2 to 0001 and the same signal is
applied to both RF inputs, the output of Channel 2 leads that
of Channel 1 by 22.5°.
The I and Q outputs are provided as currents to facilitate
summation. The summed current outputs are converted to
voltages by a high dynamic-range, current-to-voltage (I-V)
converter, such as the AD8021, configured as a transimpedance
amplifier. The resultant signal is then applied to a high resolution
ADC, such as the AD7665 (16 bit/570 kSPS).
The two I/Q demodulators can be used independently in other
nonbeamforming applications. In that case, a transimpedance
amplifier is needed for each of the I and Q outputs, four in total
for the dual I/Q demodulator.
The dynamic range is 161 dB/Hz at each I and Q output, but the
following transimpedance amplifier is an important element in
maintaining the overall dynamic range, and attention needs to
be paid to optimal component selection and design.
The AD8333 is available in a 32-lead LFCSP (5 mm × 5 mm)
package for the industrial temperature range of −40°C to +85°C.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
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