Echo-pulse technology

Medical Ultrasound Many of us have first seen our unborn children or grandchildren thanks to medical ultrasound technology. This application is somewhat related to sonar in that both use pulse echo methods to send and receive signals. However, in this short-range application, transducer arraj can be designed to form images. 

Sonar and imaging technologies are based on sending out ultrasound pulses and receiving the echoes. The resolution capabilities depend upon the emitted pulses being sharp, and the sharper the pulse the more Fourier components it has. Therefore, for a transducer to emit and detect a sharp pulse it must be able to respond to a wide frequency range - that is it must have the broad band characteristic associated with low mechanical Q. The very lossy nature of the polymer phase endows the composite with this (Q < 10). 

The electron spin echo (ESE) method is a kind of time-domain ESR using pulsed microwave radiation and it directly observes the relaxation behavior of electron spins. Since the construction of an ESE spectrometer was first reported by Kaplan early in 1962 [8], the ESE method has become more and more popular slowly but steadily. Owing to the progress in microwave technology and to the continual effort of pioneering workers such as Tsvetkov, Mims, Kevan and others [9, 10]. the ESE method has been extensively developed and improved. It is now considered to be requisite for studying the paramagnetic relaxation of radical species. 

---