Abstract: A signal receiver adaptive to a noise level includes a first comparator, a second comparator, a control unit, and a reference voltage changing unit. The first comparator compares a voltage of a received signal with a first reference voltage, and the second comparator compares the voltage of the received signal with a second reference voltage. The control unit outputs a control voltage having a voltage level corresponding to the number of output pulses per unit time of the first comparator. The reference voltage changing unit changes the magnitudes of the first reference voltage and the second reference voltage in response to a voltage level of a control voltage. The second comparator compares the changed second reference voltage with the received signal to output a transmission signal from which noise is cancelled. A voltage level of noise to be cancelled from the received signal varies according to a noise level, so the noise cancellation adaptive to the noise level is performed.

Abstract: An antenna having wide-band characteristics and a radio signal detecting device using the antenna are provided. The antenna having wide-band characteristics includes: an insulating substrate; a first conductive layer formed on the top surface of the insulating substrate, the first conductive layer having a predetermined width from the front end of the insulating substrate to the rear end thereof; a second conductive layer formed on the bottom surface of the insulating substrate; and first and second conductive plates. The rear end of the first conductive plate is attached to the first conductive layer, the rear end of the second conductive plate is attached to the second conductive layer, and the front ends of the first and second conductive plates are parallel to and separated from each other. The wide-band antenna has a simple structure thereby reducing the overall size of a device.