If the substrate of larger electromechanical coupling coefficient (such as YZ－LiNbO

3

substrate) is used for wavelet type of interdigital transducer (IDT)

its frequency characteristic curve is not smooth

but its insertion loss is smaller.If the substrate of smaller electromechanical coupling coefficient (such as X 112°Y－LiTaO

3

substrate) is used for wavelet type of IDT

its frequency characteristic curve is smooth

but its insertion loss is larger.The less the finger pairs

N

of surface acoustic wave (SAW) element

the larger its bandwidth Δ

f/f

and the larger its insertion loss

so the finger pairs

N

is appropriately taken

and is not too small.In wavelet transform element of SAW type

the finger pairs N of the transmitting IDT is 57

the finger pairs N of the receiving

IDT is between one-fourth of 57 and one-third of 57.