Product Details
●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-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.
●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 159 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.
●Applications
● Medical imaging (CW ultrasound beamforming)
● Phased array systems (radar and adaptive antennas)
● Communication receivers
●### Features and Benefits
● 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: 10 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
