| 摘要 |
A modulating device applicable to a digital radio communications system which is adaptable to a 16 or greater multi-level QAM modulation system. The device has two multi-input digital filters (22a, 22b) to implement the role of cosine roll-off filters. A logic circuit precedes the digital filters to logically manipulate n-bit data streams except for m bits (m < n) thereof which should be modulated, in a predetermined manner. The logic circuit is capable of correcting deviations of signal points of a QAM wave or changing the contour of signal constellation to a circular contour or the like, as desired. |
