US Patent 7738593 Pre-equalisation for UMTS base station

An arrangement (100) and method for RF filtering in a Node B of a UMTS TDD system by providing: a DAC converter (130) converting digital signals to analog signals; providing a narrow band analogue channel filter (150) filtering the analog signals; and providing a digital pre-equaliser FIR filter (120) coupled before the DAC (120) to filter the digital signals, the digital pre-equaliser filter means substantially correcting for non linear phase response (122) non-ideality and amplitude response non-ideality (124) in the analogue channel filter (150). This provides the following advantage(s): it enables 3GPP Node B co-location specifications to be met while providing both good transmit accuracy and acceptable ISI performance; and it allows filter centre frequency to be field tuned in software, permitting a basic RF single-channel filter to used with its centre frequency being field adjustable to a desired value centred on a UMTS channel.