| 摘要 |
A receiving circuit for generating an intermediate frequency signal having the frequency characteristics independent of variations in the temperature includes an antenna, a voltage controlled oscillating circuit (4) outputting a first oscillation frequency signal, a surface acoustic wave resonator (2), a local oscillating circuit (5) which is connected to the surface acoustic wave resonator (2) and outputs a second oscillation frequency signal, and a multiplying circuit (8) for multiplying the first oscillation frequency signal by the second oscillation frequency signal to output a local signal. A first frequency converting circuit (7) produces a first intermediate frequency signal, which has a frequency determined by a frequency of the second oscillation frequency signal, from the received signal and the local signal. An intermediate frequency filter (1) is constituted by a surface acoustic wave filter formed on the same piezoelectric substrate together with the surface acoustic wave resonator (2) and filters the first intermediate frequency signal. A second frequency converting means (9) generates a second intermediate frequency signal, which has a frequency independent of a frequency of the second oscillation frequency signal, from an output signal from the filter means and the second oscillation frequency signal. <IMAGE> |
