NIH Transducer Resource Center and Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
NIH Transducer Resource Center and Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA.
Ultrason Imaging. 2014 Oct;36(4):317-30. doi: 10.1177/0161734614524180. Epub 2014 Mar 12.
The purpose of the limiter circuits used in the ultrasound imaging systems is to pass low-voltage echo signals generated by ultrasonic transducers while preventing high-voltage short pulses transmitted by pulsers from damaging front-end circuits. Resistor-diode-based limiters (a 50 Ω resistor with a single cross-coupled diode pair) have been widely used in pulse-echo measurement and imaging system applications due to their low cost and simple architecture. However, resistor-diode-based limiters may not be suited for high-frequency ultrasound transducer applications since they produce large signal conduction losses at higher frequencies. Therefore, we propose a new limiter architecture utilizing power MOSFETs, which we call a power MOSFET-diode-based limiter. The performance of a power MOSFET-diode-based limiter was evaluated with respect to insertion loss (IL), total harmonic distortion (THD), and response time (RT). We compared these results with those of three other conventional limiter designs and showed that the power MOSFET-diode-based limiter offers the lowest IL (-1.33 dB) and fastest RT (0.10 µs) with the lowest suppressed output voltage (3.47 Vp-p) among all the limiters at 70 MHz. A pulse-echo test was performed to determine how the new limiter affected the sensitivity and bandwidth of the transducer. We found that the sensitivity and bandwidth of the transducer were 130% and 129% greater, respectively, when combined with the new power MOSFET-diode-based limiter versus the resistor-diode-based limiter. Therefore, these results demonstrate that the power MOSFET-diode-based limiter is capable of producing lower signal attenuation than the three conventional limiter designs at higher frequency operation.
超声成像系统中使用限幅电路的目的是传递由超声换能器产生的低电压回波信号，同时防止由脉冲器传输的高电压短脉冲损坏前端电路。基于电阻-二极管的限幅器（一个带有单个交叉耦合二极管对的 50 Ω 电阻）由于其低成本和简单的架构，已广泛应用于脉冲回波测量和成像系统应用中。然而，基于电阻-二极管的限幅器可能不适合高频超声换能器应用，因为它们在更高频率下会产生大的信号传导损耗。因此，我们提出了一种利用功率 MOSFET 的新型限幅器架构，我们称之为功率 MOSFET-二极管限幅器。我们评估了功率 MOSFET-二极管限幅器的插入损耗 (IL)、总谐波失真 (THD) 和响应时间 (RT) 性能。我们将这些结果与其他三种传统限幅器设计进行了比较，并表明在 70 MHz 时，功率 MOSFET-二极管限幅器在所有限幅器中提供了最低的 IL（-1.33 dB）和最快的 RT（0.10 µs），同时具有最低的抑制输出电压（3.47 Vp-p）。进行了脉冲回波测试，以确定新限幅器如何影响换能器的灵敏度和带宽。我们发现，当与新的功率 MOSFET-二极管限幅器结合使用时，换能器的灵敏度和带宽分别增加了 130%和 129%。因此，这些结果表明，在更高频率下，功率 MOSFET-二极管限幅器比三种传统限幅器设计能够产生更低的信号衰减。
