No abstract

The superharmonic imaging of tissue has the potential for high spatial and contrast resolutions, compared to the fundamental and second harmonic imaging. For this technique, the spectral bandwidth of an ultrasound transducer is divided for transmission of ultrasound and reception of its superharmonics (i.e., higher than the second harmonic). Due to the spectral division for the transmission and reception, transmitted ultrasound energy is not sufficient to induce superharmonics in media without using contrast agents, and it is difficult that a transducer has a −6 dB fractional bandwidth of higher than 100%. For the superharmonic imaging of tissue, thus, multi-frequency array transducers are the best choice if available; transmit and receive elements are separate and have different center frequencies. However, the construction of a multi-frequency transducer for intravascular ultrasound (IVUS) imaging is particularly demanding because of its small size of less than 1 mm. Here, we report a recently developed dual-element focused IVUS transducer for the third harmonic imaging of tissue, which consists of a 35-MHz element for ultrasound transmission and a 105-MHz element for third harmonic reception. For high quality third harmonic imaging, both elements were fabricated to have the same focus at 2.5 mm. The results of tissue mimicking phantom tests demonstrated that the third harmonic images produced by the developed transducer had higher spatial resolution and deeper imaging depth than the fundamental images.

No abstract

The superharmonic imaging of tissue has the potential for high spatial and contrast resolutions, compared to the fundamental and second harmonic imaging. For this technique, the spectral bandwidth of an ultrasound transducer is divided for transmission of ultrasound and reception of its superharmonics (i.e., higher than the second harmonic). Due to the spectral division for the transmission and reception, transmitted ultrasound energy is not sufficient to induce superharmonics in media without using contrast agents, and it is difficult that a transducer has a -6-dB fractional bandwidth of higher than 100%. For the superharmonic imaging of tissue, thus, multi-frequency array transducers are the best choice if available; transmit and receive elements are separate and have different center frequencies. However, the construction of a multi-frequency transducer for intravascular ultrasound (IVUS) imaging is particularly demanding because of its small size of less than 1 mm. Here, we report a recently developed dual-element focused IVUS transducer for the third harmonic imaging of tissue, which consists of a 35-MHz element for ultrasound transmission and a 105-MHz element for third harmonic reception. For high quality third harmonic imaging, both elements were fabricated to have the same focus at 2.5 mm. The results of tissue mimicking phantom tests demonstrated that the third harmonic images produced by the developed transducer had higher spatial resolution and deeper imaging depth than the fundamental images.

X 대역에서 능동 위상 배열 레이더에 적용할 수 있는 타일형 능동 송수신 모듈을 구현하였다. 제안한 타일형 구조의 구현을 위한 수직 연결은 fuzz button을 이용한 solderless 방식으로 삽입 손실은 0.6 dB, 반사 손실의 VSWR은 1.7 이하를 만족하며 X 대역에서 약 30 %의 대역폭을 가지는 광대역 특성을 가진다. 광대역 특성을 가지는 수직 연결 구조를 이용하면 수직 연결 시에 발생할 수 있는 부정합을 최소한으로 하여 우수한 이득 평탄 도를 가지는 타일형 구조의 송수신 모듈을 구현할 수 있다. AbstractA tile type active T/R(Transmit/Receive) module for X-band active array radar is demonstrated in this paper. Proposed tile type structure based on fuzz button solderless vertical interconnection shows wide band characteristic of about 30 % bandwidth in X-band with insertion loss of below 0.6 dB and input and output VSWR of less than 1.7. Moreover, the mismatching generally appeared in the vertical interconnection which shown wide band characteristic can also be minimized and, therefore, good gain flatness can be achieved.