We present a novel approach for the photonic filtering of microwave signals based on a direct- synthesis technique with optical phase modulation of the microwave signal and employing two tunable laser sources and a fixed optical passband filter. Both center frequency and bandwidth of the MPF can be controlled independently by proper selection of the respective laser wavelength detunings with respect to the filter cutoffs and therefore wide bandwidth fixed optical filters can be employed irrespective of the required MPF center frequency and bandwidth.