| 摘要 |
PURPOSE:To eliminate the need for a variable resistor and to attain miniaturization, by amplifying each output of a surface acoustic wave element outputting plural phase outputs at a variable gain amplifier, synthesizing the outputs at a synthetic element and feeding back the outputs to an input electrode of the surface acoustic wave element. CONSTITUTION:The surface acoustic wave excited at the input electrode 2a is converted into electric signals at two output electrodes 2b, 2c. Since the output electrodes 2b, 2c are placed at a location shifted with each other in the propagating direction of the surface acoustic wave, output signals B, C of different phase are outputted from the output electrodes 2a and 2c. Taking the wavelength of the surface wave at the operating center frequency as lambda, and the shift of location of the output electrodes 2b, 2c as mlambda+lambda/4 (where m=0, 1, 2,...), the phase difference alpha is 90 deg.. The phase of the output signal of the synthetic element 6 is changed by changing the gain of the variable gain amplifiers 4, 5. Thus, the oscillating frequency of the oscillators is made variable. |
