| 摘要 |
PURPOSE:To perform calibration easily and to increase precision by obtaining the difference frequency signal between the output of a crystal oscillator and a surface acoustic wave oscillator with a large temperature coefficient and a reference frequency signal and performing temperature detection, and varying the reference frequency externally. CONSTITUTION:A temperature detector 41 consists of the surface acoustic wave oscillator 43 equipped with a surface acoustic wave resonator 42, and generates a signal of oscillation frequency corresponding to temperature, which is radiated from an antenna 45 through an amplifier 44. This is received by an antenna 46 and passed through a high frequency amplifier 47, whose output is mixed with the output of the 1st local oscillator 49 by the 1st mixer 48 to obtain an intermediate frequency output. The oscillation frequency of the oscillator 49 is varied by a PLL circuit 51, etc. Its output is supplied through an amplifier to the 2nd mixer 55, which mixes it with an oscillation output corresponding to an intermediate frequency of 0 deg.C to extract only variation in oscillation frequency which varies with the temperature of a detector 41. This signal is ANDed 58 with the reference signal and the result is supplied to a counter 60, whose output is inputted to a microcomputer 61 to display the temperature on a display device 63. |
