AD8333_15 Datasheet, PDF (1/32 Pages) Analog Devices – DC to 50 MHz, Dual I/Q Demodulator and Phase Shifter

Data Sheet
DC to 50 MHz, Dual I/Q Demodulator and
Phase Shifter
AD8333
FEATURES
Dual integrated I/Q demodulator
16 phase select options 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: 159 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
FUNCTIONAL BLOCK DIAGRAM
PH12
PH13
COMM
CH 1 ΦSEL
LOGIC
4LOP
4LON
BUF ÷4
PH23
PH22
CH 2 ΦSEL
LOGIC
0°
90°
90°
0°
BIAS
Φ
Φ
Φ
Φ
I1NO
I1PO
Q1PO
Q1NO
Q2NO
Q2PO
I2PO
I2NO
Figure 1.
GENERAL DESCRIPTION
The AD8333¹ 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-4 circuit generates the internal 0° and 90° phases
of the local oscillator (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 Channel 1 is used
as a reference and the RF signal applied to Channel 2 has an I/Q
phase lead of 45°, Channel 2 can be phase aligned with Channel 1
by choosing the correct code.
1 _{Protected by US Patent 7,760,833.}
Rev. E
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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 is adjusted 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 159 dB/Hz at the I and Q outputs, 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.
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