US 7,320,247 B2
Tire pressure detection side receiving circuit and tire monitor system provided therewith
Michiya Katou, Ogaki (Japan)
Assigned to Pacific Industrial Co., Ltd., Ogaki (Japan)
Filed on Oct. 11, 2006, as Appl. No. 11/545,576.
Claims priority of application No. 2006-123645 (JP), filed on Apr. 27, 2006.
Prior Publication US 2007/0251309 A1, Nov. 01, 2007
Int. Cl. G01M 17/02 (2006.01)
U.S. Cl. 73—146  [340/447] 12 Claims
OG exemplary drawing
 
1. A tire pressure detection side receiving circuit provided in a tire pressure detector mounted on a wheel for detecting tire pressure and transmitting a result of detection to a body of a vehicle by radio, the receiving circuit receiving a radio signal from the vehicle body, the receiving circuit comprising:
an antenna resonance circuit having an antenna, a capacitor and a coil with two terminals;
a capacitance changing circuit for changing a capacitance of the capacitor of the antenna resonance circuit;
an oscillation circuit capable of imparting a test wave to the antenna resonance circuit;
a resonance level detector capable of detecting a resonance level of the antenna resonance circuit;
a memory storing data of preset reference frequency;
a resonance frequency detector changing a frequency of the test wave to be imparted to the antenna resonance circuit while the capacitor of the antenna resonance circuit is maintained at a constant capacitance, thereby detecting, as a measured resonance frequency, a frequency in a case where an amplitude level of the test wave has reached a peak; and
a tuning control controlling the capacitance changing circuit so that the measured resonance frequency is approximated to the reference frequency, thereby changing the capacitance of the capacitor of the antenna resonance circuit.