A filter block comprising a hybrid filter, the hybrid filter comprising a first signal splitter having a first input port and a first output port; a second signal splitter having a first input port and a first output port; each of the first and second splitters having first and second connection ports; the two first connection ports being connected together by a first signal path comprising a first filter; the second two connection ports being connected together by a second signal path comprising a second filter; the first and second signal paths each further comprising a transformer connected between the filter and one of the first and second signal splitters.