PURPOSE: To ensure an easy D/A conversion of a serial pulse train without lowering the accuracy and regardless of an increment of the number of bits of the pulse train to be converted for an elastic surface wave device that performs a D/A conversion of a serial input pulse.
CONSTITUTION: The electrode having an electrode finger logarithm of normal M pairs (M≥1) is connected is common to the pairs of output electrodes 3-1 and 3-2 as the input electrode 2 of an elastic surface wave device. At the same time, several pairs of electrodes corresponding to the electrodes 3-1 and 3-2 are connected in series or parallel to each other. On the other hand, the electrodes 3-1 and 3-2 have M×N pairs (N≥2) of electrode finger pair number with an equal pitch between the electrode plates, and are turned into an weighted electrode in which the electrode finger crossin width changes with every N pairs and in the ratio of 2i or 2-i(i=0, 1...N- 1) in the order of the distance nearer the electrode 2. Then the distance between the electrodes 3-1 and 3-2 and each pair of input electrodes is made different each by M×N×λ (λ: wavelength of elastic surface wave).
ISHIGAKI MASAHARU
HAZAMA TAKESHI
