A technique for reducing intermodulation distortion in ACSB transmitters

Amplitude Compandored Sideband (ACSB) promises to open up many new channels for land mobile radio.[1],[2] Transmitter intermodulation distortion (IMD) directly affects adjacent channel protection of these new closer spaced channels. [3] This is especially critical in fixed station applications since the base station or repeater may be transmitting a high percentage of the time and is often radiating a higher ERP signal from a higher location than mobile stations. There are several techniques that could be employed to provide lower transmitter intermodulation distortion. One technique described here is especially suitable in fixed station applications and can provide a significant reduction in intermodulation distortion using standard components that are readily available.