PURPOSE: To omit a hybrid transformer and also set an optional pass band by connecting two-port SAW resonators of different frequencies in parallel with each other so that the phase shift amount of (2n+1)π(n=0,1,2...) is secured between the input/output terminals of both resonators.

CONSTITUTION: The two-port SAW resonators 4 and 5 have different resonance frequencies f1 and f2 and an equal phase shift amount between both input/output terminals. Here input terminals 6 and 8 and 6' and 8' are connected to each other among those paired input/output terminals 6,6'∼9,9'. Thus a new pair of input terminals are obtained with terminals 6' and 8' grounded respectively. While output terminals 7 and 9' and 7' and 9 are paired respectively in parallel connection with terminals 7' and 9 grounded. Thus a new two-port circuit is obtained. Both resonators 4 and 5 have a 180° phase difference between then with each output terminal to the same signal since the polarities are inverted between output terminals 7/7' and 9/9' in case both resonators are viewed independently of each other. Thus a band-pass filter is obtained through the combined connection between the input/output terminals of both resonators 4 and 5.