**3.1. General system's overview**

As we have said, our goal is centred in the design of ultrasonic imaging systems based on solutions which require fewer resources and storage capacity than conventional systems. Thus, in Figure 10 is schematically represented our vision of the system, which is composed by three parts:


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Strategies for Hardware Reduction on the Design of Portable Ultrasound Imaging Systems

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As we study in section 2.1.1, it is basically composed of one channel in emission and two channels in reception. Figure 11 shows the complete architecture for 2R-SAFT implementation. As we can see, a multiplexer is connected to the transmission channel for sequentially activate each element as an emitter, and a second multiplexer will be on charge

All the acquisition process is managed by a hardware control system which is located in a field-programmable gate array (FPGA). In addition, a local memory is also used to store every received signal. Finally, the signals are transferred to the imaging system using any communication interface (USB, Ethernet, PCI Express). In the imaging system, raw data is stored in a RAM memory of 2*N* − 1 signals of capacity to be used for compose and beamform

As we see in sections 2.1.2 and 2.2, and in order to combine 8xA-SAFT with Golay codes, we will double the number of channels in reception to maintain the number of original firings. Thus, in this case the system is composed of one channel in emission and 32 channels in reception as Figure 12 suggests. A multiplexer connects the transmission channel to elements for sequentially activate one of them, in steps of 8 elements, to transmit an A or B code for odd or even shots respectively. A second multiplexer will be on charge of connecting the 32 reception channels to the receiving aperture ensuring that every coded signal is stored in a local memory. Therefore, two signals per coarray element are overlapped, each one belonging to an A or B code respectively. Additionally, an offset is added to the coarray structure in order to centre its elements, and the boundary coarray elements are removed from it as we

Now the software imaging system requires a bigger memory and an additional decoding stage, where the complete set of signals is deconvolved, generating a 2*N* − 8 data set. Later

In recent years, computing industry has been opened a way to parallel computing. Nowadays, all consumer computers ship with multi-core processors. Dual-core processors (CPUs) were introduced in personal systems at the beginning of 2006, and it is currently common to find them in laptops as well as 8 and 16-core workstation computers, which

on, as usual, the data will be beamformed using the graphics processing unit.

**3.3. Image generation subsystem: Parallel beamforming**

of connecting the selected elements to both reception channels.

**Figure 10.** Hardware/Software system proposed

the ultrasonic images using a GPU.

illustrated in section 2.2.2.

*3.2.2. 8xA-SAFT with Golay encoding architecture*

*3.2.1. 2R-SAFT architecture*

**Figure 9.** Experimental images from tissue phantom. (a) 2R-SAFT + Golay, (b) 2xA-SAFT + Golay , (c) Lateral profiles comparison between 2R-SAFT + Golay and 2xA-SAFT + Golay, (d) 4xA-SAFT + Golay, (e) 8xA-SAFT + Golay, (f) Lateral profiles comparison between 4xA-SAFT and 8xA-SAFT + Golay , (g) 16xA-SAFT + Golay, (h) TFM , (i) Lateral profiles comparison between 16xA-SAFT and TFM

#### **3.2. Acquisition subsystem**

In this section, two acquisition architectures are exposed. On one hand, a minimal system for 2R-SAFT strategy which allows a low-cost and small imaging system and, in the other hand, the architecture which implements 8xA-SAFT plus Golay encoding strategy and uses more hardware but yields better quality images. Which strategy to use depends on the concrete application. Any of these configurations can be carried out using boards systems available in the market.

Strategies for Hardware Reduction on the Design of Portable Ultrasound Imaging Systems 13

**Figure 10.** Hardware/Software system proposed
