A transmission / reception
system includes a
transmitter and a
receiver. The
transmitter includes a
voltage converter for generating a
voltage according to transmission data, a
voltage-controlled oscillator for generating a
signal of a frequency corresponding to the voltage generated by the
voltage converter under non-
feedback control, and a first antenna for emitting the
signal generated by the voltage-controlled oscillator. The
receiver includes a second antenna for receiving the
signal emitted from the first antenna, a first
amplifier for amplifying the signal received by the second antenna, an oscillator for generating a local oscillation signal, a mixer for mixing the signal amplified by the first
amplifier with the local oscillation signal and converting the signal amplified by the first
amplifier into an intermediate-frequency (IF) signal, a
detector for detecting the IF signal, and a controller for changing a frequency of the local oscillation signal according to the frequency of the received signal, so that the IF signal has a predetermined frequency.