Direct conversion radio receiving system using digital signal processing for channel filtering and down conversion to base band

Abstract

A radio receiving system includes an orthogonally-modulated waveform detection/channel filter section 4, an I signal root Nyquist filter 20, a Q signal root Nyquist filter 21, and a signal detection/demodulation section 25. The orthogonally-modulated waveform detection/channel filter section 4 further includes a first filter (a band pass filter) 2 which permits passage of only a signal at a frequency band assigned to a communications system from which the radio receiving system receives a signal; a sample-and-hold circuit 5; a Hilbert transformer 6; a first channel filter 7 through N-th channel filter 9; and a clock signal shaping/controlling section 15. The band pass filter 2 is provided with the characteristics which cancel the aperture effect due to a sampling operation, thus compensating for the aperture effect due to a sampling operation.

Dependencies are inferred from the claim text.