Microwave frequency dividers are fundamental new devices which employ subharmonic generation to provide accurate frequency division by two over microwave octave bands. Unlike mixer-type down con-vertors, these devices require no local oscillator. Furthermore, each successive stage halves the bandwidth, permitting a wideband input to be mapped into a narrowband output where analogue or digital processing can easily be accomplished. These properties are directly applicable to improving the performance of electronic countermeasures equipment, communications systems and laboratory instruments. At the Defence Research Establishment Ottawa, an experimental ultrabroadband countermeasures system is being developed which uses frequency division, digital signal manipulation and frequency multiplication. The system compresses the frequency range from 125 MHz–15 GHz, in octave bands, into the 125–250 MHz band for digitisation. Once digitised, the signal may be analysed, classified or manipulated to produce coherent jamming signals to counter frequency-agile, Doppler or coded waveforms.