Abstract: In a radio receiver apparatus of an orthogonal detection type, a voltage controlled first local oscillator generates a first local oscillation signal, and mixers mix an inputted reception signal with the first local oscillation signal and a 90.degree. shifted signal thereof, respectively, the mixed signals respectively being passed through first and second band-pass filters to obtain desired first intermediate frequency signals. Further, a second local oscillator generates a second local oscillation signal. Further mixers mixes the first intermediate frequency signals from the first and second band-pass filters with the second local oscillation signal and a 90.degree. shifted signal thereof, respectively. Then there is calculated either one of a sum of and a difference between the resulting mixed signals, the calculated signal being passed through a third band-pass filter to obtain a second intermediate frequency signal to be demodulated.

Abstract: This serial data receiving apparatus is intended to realize the receiving process of serial data having an inferior SN ratio with a simple arrangement and at low cost. A one-bit length of the serial data is divided into several blocks. The sampling data is input at the multiple points of each block by using a shift register built in a microcomputer. The data is temporarily held so that the data at the same number block of each block is accumulated for several bits. The accumulation of the data results in cancelling the noise components and leaving the original signal components. This overlapping type receiving system makes it possible to clarify the receiving phase of a preamble signal for bit synchronization and to establish the bit synchronization. Next, the sampling data signals are entered at the multiple points based on the resulting receiving timing and the logic value of the bit is determined according to the ratio of the number of values of "1" to "0" contained in the data.