A continuously adjustable programmable harmonic microwave attenuator and linear phase controller (HAPC) uses mobile signal couplers (wave-probes) in a slabline structure which is terminated with 50 Ohms. The coupled ports of the wave-probes are connected with the output port of the unit via a power combiner using flexible RF cables. The wave-probes are attached to the vertical axes of mobile carriages, which are placed at variable distances from the input port, corresponding to the expected transmission phases, whereas the depth, at which the wave-probes are inserted into the slabline, determines the coupling factors and thus the value of the attenuation. The unit can be calibrated at a number of harmonic frequencies typically equal to the number of the wave-probes used.