| 摘要 |
PURPOSE:To make easy circuit integration, by enabling frequency modulation without using a varactor diode, through the use of a surface acoustic wave element as the phase shift element of frequency selectivity. CONSTITUTION:Two signals having a phase difference of 90 deg. are picked up from output terminals 23, 24 of a surface acoustic wave element 13. A signal applied to an input terinal 23 is amplified with a differential amplifier composed of composite connection with common base type transistors (TR) Q13, Q14 and common emitter tyep of TRs Q15, Q16 and a balanced signal is picked up at load resistors R11, R12. Similarly, from a signal inputted to an input terminal 24, a balanced type signal having the flat frequency characteristics are picked up through load resistors R18, R19 by means of a differential amplifier with the same constitution as the input terminal 23. Those balanced type signals are inputted to a phase synthesizer, and a balanced signal which enables the phase change in 90 deg. is picked up at load resistors R1, R2 through the operation of the phase synthesizer, and it is amplified with a differential amplifier consisting of TRs Q7-Q10 to be positive feedback loop outputs 21, 22. |
