Survey of Transient Radio Sources with Digital Interferome

六年来研制的元件射电干涉仪，用新的HEMT接收器使灵敏度提高了三倍。它正在监测像Cyg X-3这样的瞬变射电源，并观察伽马射线类星体和快速变化的BLLac天体。干涉仪使世界上第一次能够以奈奎斯特速率获得射电图像。目前世界上使用的所有射电干涉仪都是傅里叶合成(间接成像干涉仪)，可以制作出精细的射电地图。利用维纳-金钦定理，对剑桥大学提出的方法进行了优化，用较少的天线数目获得了较好的图像。它要求接收信号的遍历性(时间平均值=集合平均值)，因为来自天文射电源的信号通常不会迅速变化，并且遍历性是令人满意的。由于脉冲星或通信信号的非遍历性，傅里叶合成不利于脉冲的搜索。早稻田大学研制的直接成像干涉仪通过空间FFT处理将空间接收到的波变换为方向幅度，其中坐标表示与动量表示有关。该处理器还可以对通信信号进行处理，在同时通信和多向通信领域有很大的应用价值。我们已经获得了该加工机的专利。

64 element radio interferometer developed for these six years has achieved three times higher sensitivity than before with new HEMT receivers. It is monitoring transient radio sources like Cyg X-3, and watching gamma-ray quasars and rapidly varying BL Lac objects. The interferometer has made it possible to get radio images at Nyquist rate for the first time in the world.All radio interferometers currently used in the world are Fourier synthesis (indirect imaging interferometer), which could make fine radio maps. The method developed by Cambridge University is optimized to get fine images with less number of antenas, using Wiener-Khinchin theorem. It requires ergodicity(time average = ensamble mean) in received signals.Since signals from the astronomical radio sources usually do not change rapidly, and the ergodicity is satisfied. However signals from pulsars or comunication are non-ergodic, so Fourier synthesis is inapropiate to search pulsars.Direct imaging interferometer developed by Waseda University transforms the spatially received waves to the directional amplitudes using spatial FFT processing, in which cordinate representation is related to momentum representation by Fourier transform. Comunication signals could also be processed by this processor, and it is usefull in the fields of simultaneous and multi-directionai comunications. We have got a patent of the procesor.