Programmable transversal filter based adaptive line enhancer

A programmable transversal filter (PTF)-based adaptive line enhancer (ALE) subsystem is described. It covers the 30 to 58-MHz frequency range. The PTF-ALE can be utilized with frequency-hopping radio receivers to greatly reduce unwanted RF interference via a quickly programmable null. A subsystem configuration (adaptive line enhancer) and adaptive algorithm (differential steepest descent) are selected. A digitally controlled (TTL) PTF programmed by a standard personal computer with an off-the-shelf direct memory access interface is described. The PTF device has the capability to be reprogrammed at 3 μsec per tap weight plan. The ALE subsystem consists of a delayed, unity gain channel and a difference channel containing the PTF. The subsystem creates a 40-dB single null, software programmable to any frequency in the range 30 to 58 MHz. The null has a 3-dB bandwidth of 45 KHz. When combined with a fast microprocessor, the PTF-ALF is ideal for excision of narrowband interfering signals in fast hopping communication systems