Radio Frequency Channel Arrangements for Digital Radio Systems

Many digital radio-relay routes use radio-frequency channel arrangements originally designed to accommodate analog radio-relay systems. Because of the broader spectrum of digital signals, new considerations must be taken into account. When a common transmit-receive antenna is used, intermodulation among transmitters in the passive antenna, waveguide and branching networks can interfere with receivers. Properly accounting for these can result in an increased number of digital radio channels without degraded performance, compared with previous plans. IN some cases additional mid-band separation between transmitters and receivers may be required for single antenna operation. Specific frequency plans for high capacity digital radio RF channel arrangements in the 6- and 11-GHz common carrier bands are presented.