As a means to reduce the loss in an SAW filter, the IDT (interdigital transducer) called the internal reflection‐type transducer has been studied extensively recently. This IDT is believed to be useful as a filter for video and broadband data transmission since it is simple in structure and has low loss over a broadband while its fabrication process and external circuit are simple. So far, the filter constructed with this IDT has had a large ripple in the passband due to a large spurious reflection. To alleviate this problem, a new distributed acoustic reflection transducer is proposed as an internal reflection type IDT in which suppression of the unwanted spurious reflection is possible over a broad frequency range. Next, the operation mechanism of this IDT is investigated and a first‐order design method is presented. It is pointed out that a low‐loss filter with an insertion loss less than 10 dB and spurious reflection suppressed by more than 45 dB can be realized with this IDT over a broad frequency range.

The DC Decay Testing Method is quite useful at testing large-capacity machines, because it is a simple standstill response testing method and needs only a small capacity of dc power supply equipments. When authors held a field test of the large-capacity alternating current generator (6000KVA-18P), we found that there was an unnecessary small curl in operational impedance locus. And it lead to the error at predicting the machine constants of its generator. So we consider that it is a problm in practice.In this paper, the investigation of measured data and approximate analytical calculation shows that the curl in operational impedance locus is caused by truncating the dc decay current data. So, authors propose a data processing method by data extrapolation which predicts the decay current after the measured data. And the result of applying the Expanded Dalton-Cameron Method to the total decay current is good agreement with the result of the other measuring methods. The proposed method is also applicable in testing the small and middle-capacity machines and expands the usefulness of the DC Decay Testing Method.