A computer aided design method, for designing a Ku-band miniature waveguide low pass filter, wherein the waveguide low pass filter acts like a band pass filter due to the high pass features of the waveguides of the waveguide low pass filter, suitable for suppressing harmonic and higher order mode signals generated in multiplexers in satellites by use of an electrical device consisting of a memory unit storing a filter synthesis software having a graphical user interface, a processor unit adapted for running said filter synthesis software, a data input interface for receiving design parameters from a user and a monitor for graphical display of designed filter circuit simulation, wherein the band pass filter design is started in form of a distributed parameter low pass filter comprising transmission lines and short circuit stubs subsequently converted into equivalent impedance waveguides (RectWG), the method consisting of; - Selection of the following filter parameters via the graphical interface of the filter synthesis software by use of the data input interface, ∘ frequency range of pass band of the band pass filter, ∘ frequency range of stop band, ∘ cutoff frequency of the waveguide low pass filter to be designed, quarter wave length frequency of the distributed parameter eflow pass filter to be synthesized, ∘ width (a) and height (b) of waveguides to be used in the waveguide low pass filter, ∘ number of transmission lines and short circuit stubs to be used in the distributed parameter low pass filter, - Forming a distributed parameter low pass filter circuit consisting of transmission lines interconnected in series with short circuit stubs, between a source resistance (Rs) and a load resistance, - Raising circuit impedance level by locating an inverter on each end of formed circuit, - Conversion of the transmission lines to equivalent waveguides (RectWG), - exchange of impedances at circuit ends with impedances of waveguides (RectWG) used at the input and output of the waveguide low pass filter at the cutoff frequency of the waveguide low pass filter, - Conversion of the short circuit efstubs into equivalent cavities, - Adjustment of stub lengths (h) in a manner to create transmission zeros at more than one frequency in stop band, - Adjustment of stub lengths (h) and waveguide heights (b) and thus adjustment of return loss in pass band and filter selectivity, - Display of synthesized filter on screen. - Selection of the following filter parameters via the graphical interface of the filter synthesis software by use of the data input interface, ∘ frequency range of pass band of the band pass filter, ∘ frequency range of stop band, ∘ cutoff frequency of the waveguide low pass filter to be designed, quarter wave length frequency of the distributed parameter eflow pass filter to be synthesized, ∘ width (a) and height (b) of waveguides to be used in the waveguide low pass filter, ∘ number of transmission lines and short circuit stubs to be used in the distributed parameter low pass filter, ∘ frequency range of pass band of the band pass filter, ∘ frequency range of stop band, ∘ cutoff frequency of the waveguide low pass filter to be designed, quarter wave length frequency of the distributed parameter eflow pass filter to be synthesized, ∘ width (a) and height (b) of waveguides to be used in the waveguide low pass filter, ∘ number of transmission lines and short circuit stubs to be used in the distributed parameter low pass filter, - Forming a distributed parameter low pass filter circuit consisting of transmission lines interconnected in series with short circuit stubs, between a source resistance (Rs) and a load resistance, - Raising circuit impedance level by locating an inverter on each end of formed circuit, - Conversion of the transmission lines to equivalent waveguides (RectWG), - exchange of impedances at circuit ends with impedances of waveguides (RectWG) used at the input and output of the waveguide low pass filter at the cutoff frequency of the waveguide low pass filter, - Conversion of the short circuit efstubs into equivalent cavities, - Adjustment of stub lengths (h) in a manner to create transmission zeros at more than one frequency in stop band, - Adjustment of stub lengths (h) and waveguide heights (b) and thus adjustment of return loss in pass band and filter selectivity, - Display of synthesized filter on screen.