Use SHARC 2147x processor to enhance portable continuous wave Doppler processing capability

Floating-point digital signal processing has become a consistent demand for precision technology, and applications that require higher precision in fields such as aviation, industrial machinery, and medical care usually have this demand. Medical ultrasound equipment is one of the most complex signal processing machines currently in use, and is gradually expanding into the portable field. The challenge is to achieve this intensive signal processing without sacrificing system performance. With the introduction of the low-power SHARC 2147x” title=”SHARC 2147x”>SHARC 2147x processor, ADI has been able to solve the challenge of providing precision processing while reducing the power budget for portable ultrasound applications. This article discusses the challenges of portable ultrasound equipment. The use, the processing technology used, and how the SHARC 2147x series processors provide the necessary functions at the lowest power consumption level.

Portability without sacrificing performance

Key nursing technologies such as ultrasound systems require sufficient reliability and consistent quality whether they are used clinically or remotely. Although the advancement of low-power technology has promoted the development of portable devices, there are still many basic components in the design of medical ultrasound systems that need to bring all hospital functions to disaster areas where ultrasound cannot be used before. This is the unshirkable responsibility of medical device developers. The products they provide should be able to provide the highest image integrity performance under a variety of environmental, commercial and technical constraints. Especially for portable ultrasound equipment, system performance means being able to interpret images with the same clarity and accuracy as some specific systems-but now it carries the weight, size, battery life, and cost of specific categories. Restrictions. These design constraints require components to have real-time computing capabilities, low power consumption, and low cost and compactness for product design considerations. With the rise of portable ultrasound equipment, the challenge of simultaneously meeting low power consumption and maintaining the same level of performance has become more and more difficult.

Continuous Wave Doppler” title=”Continuous Wave Doppler”>Continuous Wave Doppler Imaging

“Ultrasound imaging” title=”Ultrasound imaging”>Ultrasound imaging technology is based on Johann Christian’s Doppler principle, that is, moving objects emit detectable frequencies-“Doppler frequency shift” or sound. For example, ultrasound images of blood density It is created by introducing beams into blood vessels and then detecting blood flow (the “sound”). Doppler ultrasound imaging has two main modes, pulse wave (PW) Doppler and continuous wave (CW) Doppler. Pulse wave Doppler transmits ultrasound pulses along the scan line, and uses the relative time between the received signals to calculate the Doppler frequency-so the pulse characteristics of the transmitter can be used to obtain blood flow position information.

Continuous Wave Doppler Ultrasound

This article mainly discusses the second, continuous wave Doppler ultrasound, which can detect and measure the velocity of moving tissues in the body. Because it produces continuous waves, continuous wave Doppler has higher sensitivity and lower bandwidth requirements, usually less than 100kHz, so it is particularly effective for evaluating higher blood flow speeds. Continuous wave Doppler high-speed detection can be used for the diagnosis of congenital or valvular heart disease, because high blood flow configuration tracking is the basis for detecting these diseases.

As the name implies, when using continuous wave Doppler ultrasound technology, the sending sensor (piezoelectric crystal) will send a continuous single-frequency tone, while the receiving sensor records the acoustic echo ultrasonic signal. Because the interpretation of beat frequency (Doppler shift) determines the speed and direction of blood flow in the cardiovascular system, high-performance signal processing in the continuous wave path is a key element of measurement accuracy. The dynamic range of CW Doppler signals is the largest of all signals in the ultrasound system, partly due to leakage from the transmitted signal (caused by the half-duplex characteristics of signal transmission) across the receiving path and the fixation close to the body surface Reflexes produced by body parts. Detecting blood flow in deeper blood vessels in the body will produce a very weak Doppler signal, so the entire continuous wave signal chain requires a wide dynamic range. The performance of a high-quality ultrasound system is directly related to the realization of a good signal chain integration.

Dynamic range of floating point processing

The inherent exponentiation in floating-point arithmetic ensures that a much larger dynamic range can be obtained-the largest and smallest values ​​can occur-which is especially important when dealing with extremely large data sets or data sets whose range may be unpredictable. Therefore, floating-point processors are ideal for computing-intensive applications such as Doppler ultrasound. This kind of dynamic range processing enables portable ultrasound systems using continuous wave Doppler technology to detect these very low signals. The function of the digital signal processing unit in the continuous wave path is to at least implement wall filtering, envelope detection and fast Fourier transform (FFT).

ADI’s full signal chain integration

ADI’s SHARC 2147x series of DSP and analog front ends” title=”Analog Front End”>Analog Front End (AFE) components can process ultrasonic signals in the entire signal chain. Like any complex technology, highly integrated components can improve overall system efficiency And performance. For signal processing-intensive applications like portable ultrasound, the speed and efficiency of the entire signal chain will directly affect the quality of maintenance, despite the portable form. In order to achieve precise analysis, from receiving, to front-end analog signal processing components to digital Signal processing and maintaining strong signal integrity at the back end are key.

ADI’s new SHARC 2147x series processors are mainly used for computationally intensive floating-point applications. SHARC 2147x series processors integrate a 32-bit floating-point arithmetic unit with a 40-bit extended precision capability, support a wide dynamic range and very high-precision calculations, and are designed to work at high frequencies with very low power consumption. These processors use low-power process technology to reduce overall power consumption, and also use other power-reduction technologies, the power consumption is very small in the idle state. This combination of low active power consumption and very low idle power consumption can extend battery life. Low power consumption also means that there is no need for any forced heat dissipation technology, allowing the processor to be used in places where space is quite tight. SHARC 2147x series processors have a very small form factor, so it can achieve high space efficiency-all these features are extremely suitable for portable ultrasound applications.
SHARC 2147x series processors have 5Mb of on-chip memory, so the need for external memory is minimized, thereby improving the overall performance of the system. In some compact embedded application implementations, only on-chip memory is sufficient, and external memory is no longer needed, thereby reducing bill of materials (BOM) costs. With 5Mb of on-chip memory, ultrasound system development can achieve the lowest BOM cost and maximum portability. In order to maximize the performance of the chip, the SHARC 2147x series processors also integrate a dedicated hardware accelerator with independent arithmetic unit and DMA memory mapping function, which can be used to realize the parallelization of various speed components in the Doppler signal returned from decoding and analysis. FFT processing function. In addition, offloading the FFT operation to this parallel engine can also reduce the power consumption of the FFT processing cycle.

Analog front-end (AFE) components can be used to optimize the performance of the analog signal chain while limiting the number of circuit board components to minimize power consumption. ADI’s AD9276 eight-way receiver not only includes the processing capabilities of B-mode and pulse wave Doppler mode imaging, but also includes an integrated I/Q demodulator, so it can be used in a small form factor and ultra-low power consumption. Realize continuous wave Doppler processing. With 8-channel variable gain amplifier (VGA) with low noise preamplifier (LNA), time gain control (TGC) channel, anti-aliasing filter (AAF), 12-bit 10MSPS to 80MSPS analog-to-digital converter (ADC) Provide high-quality imaging systems for high-end ultrasound systems. The built-in I/Q demodulator with programmable phase delay function for each channel allows the system to process continuous wave Doppler signals with a particularly large dynamic range.

Implementation of ultrasound equipment using ADI’s SHARC 2147x as the core floating-point processor and AD9276 as the analog front end

ADI’s SHARC DSP (such as the SHARC 2147x series) and analog front-end products can help medical product designers convert complex, highly reliable, and computationally intensive technologies such as continuous wave Doppler ultrasound into portable designs. The SHARC 2147x series DSP achieves the design goals of system developers by keeping low costs, reducing system complexity through integration, and shortening the development cycle. All these measures will not sacrifice the key design goals: ultrasonic function and reliability in the field. It can make the diagnosis ability no less than the system used in the hospital.

ADI SHARC floating point digital signal processor

ADI’s 32-bit floating point SHARC digital signal processor adopts the super Harvard architecture, which can achieve a good balance between excellent core and memory performance and outstanding I/O throughput. This super-Harvard architecture adds an I/O processor with a related dedicated bus, thus expanding the traditional concept of separate program and data memory buses. In addition to meeting the requirements of the most computationally intensive real-time signal processing applications, the SHARC processor also integrates a large memory array and dedicated peripherals to simplify product development and shorten the time to market.

Complete development and support ecosystem

ADI’s software and hardware development tools are designed to provide engineers with a simpler and more robust system development and optimization method, which can simplify the product development process and shorten the time to market. The SHARC processor series uses well-known development tools, including VisualDSP++ integrated development and debugging environment (IDDE) and EZ-Kit Lite evaluation and application prototyping platform. A rich third-party software support network can further help developers design smarter and more efficient solutions for a wide range of applications.

ADI’s healthcare solutions

ADI provides healthcare customers with a comprehensive portfolio of linear, mixed-signal, MEMS and digital signal processing technology products that can be used in medical imaging, patient monitoring, medical instruments, and consumer/home healthcare. Backed by leading design tools, application support, and system expertise, ADI’s products and technologies play a pivotal role in medical design, helping to determine the future of diagnostic and monitoring equipment, as well as health and healthcare equipment. For more information about ADI’s healthcare products, please visit: http://healthcare.analog.com.