Synthetic aperture imaging with arrays of arbitrary shape--part II: The annular array

It has been previously shown that full aperture resolution can be achieved with an annular transducer array by transmitting and receiving between all pairs of elements around the array circumference and applying an appropriate weighting function. If there are N elements in the array, this requires N transmissions. This paper shows that full aperture resolution can be obtained with a much smaller number of transmissions (two to four) by using a certain aperture phase weighting on transmit and receive. Thus, full aperture, real-time imaging from an annular array should be feasible.