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Doppler Estimator BJT  LNA
CMOS  LNA
Predictive ADC
CWDP


CONVENTIONAL CW DOPPLER

In CW Doppler, ultrasound is emitted 100% of the time. This requires the use of two separate transducers: one transmits the acoustic energy, the other receives echoes. Typically, a two-element transducer is arranged as a split disc. The transmit/receive beam patterns are angled with respect to each other as shown below.
Pencil Probe
Thus, determining by the region of overlap between those patterns, the active sample volume is located at a fixed depth. 
STEERABLE BEAM CW DOPPLER

Employing an array of transducer elements for CW Doppler, a group of the elements is used as a transmitter while other elements are arranged  as a receiver. 
Steerable Doppler
CW ARRAY DOPPLER  vs. CONVENTIONAL

Use of a transducer array for CW Doppler imaging has many advantages over pencil probe.  In particular, such a system provides:
Improved  Signal-to-Noise Ratio
Electronically steered & focused  beam
User-selectable sample volume
Larger aperture
The plots below illustrate the focal beam  steering (A) and axial beam profile (B) at  two focal length.
Beam Steering A
Beam Focusing
B
Simulations were performed for a 32- element linear array with wavelength pitch at 3 MHz and uniform apodization.
CW DOPPLER PROCESSOR

To expand the use of portable linear array machines for cardio- vascular imaging, Echoescan has developed a stand-alone CW Doppler Processor (CWDP). The CWDP provides the signal- processing path for up to 32 receive channels supporting, therefore, a 64-element array. Its key features are as follows:
The RF interface to acquire raw data via system T/R switches or from the LNA outputs
Capability of processing up to 32 CW Doppler signals at RF
Compact 32-channel CW beamformer  implementing our proprietary signal processing algorithms
A ± 450 beam steering range
Embedded stationary canceller with a 100 Hz cut-off frequency
I/Q component 20-Bits output
Serial control interface to select the sample volume
The proposed solution  is suitable for both SoC and PCB designs. We can also help to implement the CWDP concept for upgrading current and developing new products. 

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