## 1 Introduction  
In recent years, the scanning acoustic microscopy (SAM) system has been widely used in the field of nondestructive testing to detect defects such as voids inside rigid structures [1; 2; 3; 4]. The SAM system uses high-frequency ultrasonic signals to restore images of the internal structure of the object under examination [5; 6]. A high-frequency ultrasound (\(>\)20 MHz) allows small structures to be captured because of its good spatial resolution in the order of tens of micrometers. The SAM system has been used in many different fields, in which succession must be followed. [PERSON] et al. used the SAM system to analyze the impedance measurement of tissue. Their research plays an important role in ensuring the quality of ultrasound diagnostics [7]. [PERSON] et al. have developed a new calculation method for the SAM system to measure objects with a thickness of 1.95 um with an accuracy of 0.0016% [2]. [PERSON] et al. adopted SAM to evaluate power electronic components with a nondestructive testing (NDT) method [8]. [PERSON] et al. used SAM to identify battery defects [9]. [PERSON] et al. used SAM to scan interior images of electronic components [10]. The complete SAM system includes five main parts: a transducer, a pulser/receiver, a digitizer, a motion controller and image processing [1]. For high-frequency transducers with small focal zones, small dimensions can be detected in the structure to be tested [10]. Therefore, the ultrasonic transducer strategy, which converts electrical energy into high-frequency sound waves, is an important consideration for optimizing system performance and achieving high image quality [2; 7]. There have been many studies on how to generate a signal to the excitation transducer [11]. These studies mainly focused on generating arbitrary waveforms to the excitation transducer to increase the signal-to-noise ratio (SNR) and increase the resolution of the resulting images [11; 12; 13; 14; 15]. However, these studies have not focused on deploying a complete device for nondestructive testing (NDT) and SAM systems. In this study, we will discuss the complete pulser/receiver (P/R) device used in the SAM system and the methods for increasing the scanning speed of the SAM system [12; 16; 17; 18; 19; 20]. There are usually two types of pulses used to excite transducers: unipolar and bipolar pulses [2; 21; 22]. The bipolar pulses carry a high amount of energy, but the bandwidth is small [23; 24]. The bipolar pulse is often used with applications that use low-frequency transducers [2; 7; 9; 25]. Unipolar pulses with higher bandwidths bring smaller power, suitable for applications using high-frequency transducers. Therefore, unipolar pulses can produce a vertical resolution (interlayer resolution) better than that of bipolar pulses [9; 26]. In this study, we will present the design of a unipolar P/R device to stimulate the transducer for imaging applications [27]. The programed P/R is fully compatible with SAM systems and many transducers with different operating frequencies. Typically, traditional SAM systems use one transducer, but our P/R equipment is designed to be used simultaneously with four transducers. Thus, the scanning speed of the new SAM system is four times that of a traditional SAM system. One of the most critical problems of P/R devices is the generation of unipolar pulses with high voltages and small duty cycles (<10 ns) [8]. There are two steps to creating this pulse. The first step is using a field programmable gate array (FPGA) to generate pulses with small duty cycles and low voltage amplitudes. The second step is using this pulse to excite a high-frequency Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET) in order to generate high voltage signals that trigger the transducer [26]. However, this pulse is very difficult to perform and is often directly affected by elements on the printed circuit board (PCB). High frequency signals on the PCB often include overshooting and undershooting parts.