Selectable band-pass filtering apparatus and method

A selectable band-pass filtering apparatus for use with a spectrum analyzer for testing a multi-channel communication system, said apparatus comprising:

• an input end for receiving a communication signal to be filtered;
• a high-pass filter section including a plurality of separate high-pass filters each characterized by a respective high-pass cut-off frequency within a predetermined input frequency spectrum characterizing said communication system;
• a low-pass filter section including a plurality of separate low-pass filters each characterized by a corresponding low-pass cut-off frequency within said input frequency spectrum;
• an output end to be coupled to an input of said spectrum analyzer;
• switch means capable of connecting a selected one of said high-pass filters in series with a selected one of said low-pass filters between said input and output ends to select a passband having center frequency and bandwidth characteristics being defined by corresponding said high-pass cut-off frequency and said low-pass cut-off frequency, said selected passband characteristics corresponding to one or more selected channels used by said communication system, said connected filters generating a band-pass filtered communication signal corresponding to said selected channels at said output end;
• and
• a control device capable of operating said switch means according to said selected filters.

A selectable band-pass filtering spectrum analyzer system for testing a multi-channel communication system, said apparatus comprising:

• a selectable band-pass filtering unit including:
• an input end for receiving a communication signal to be filtered;
• a high-pass filter section including a plurality of separate high-pass filters each characterized by a respective high-pass cut-off frequency within a predetermined input frequency spectrum characterizing said communication system;
• a low-pass filter section including a plurality of separate low-pass filters each characterized by a corresponding high-pass cut-off frequency within said input frequency spectrum;
• an output end;
• switch means capable of connecting a selected one of said high-pass filters in series with a selected one of said low-pass filters between said input and output ends to select a passband having center frequency and bandwidth characteristics defined by corresponding said high-pass cut-off frequency and said low-pass cut-off frequency, said selected passband characteristics corresponding to one or more selected channels used by said communication system, said connected filters generating a band-pass filtered communication signal corresponding to said selected channels at said output end;
• and
• a control device capable of operating said switch means according to said selected filters;
• and
• a spectrum analyzer unit for analyzing said filtered communication signal.

A method for selectively band-pass filtering an electrical signal, said method comprising the step of:

• providing a high-pass filter section including a plurality of separate high-pass filters each characterized by a respective high-pass cut-off frequency within a predetermined input frequency spectrum;
• providing a low-pass filter section including a plurality of separate low-pass filters each characterized by a corresponding low-pass cut-off frequency within said input frequency spectrum;
• and
• directing said signal through a selected one of said high-pass filters and through a selected one of said low-pass filters to generate a band-pass filtered signal having frequency corresponding to a passband having center frequency and bandwidth characteristics defined by corresponding said high-pass cut-off frequency and said low-pass cut-off frequency.

A method for selectively band-pass filtering a communication signal to be fed to a spectrum analyzer for testing a multi-channel communication system, said method comprising the steps of:

• providing a high-pass filter section including a plurality of separate high-pass filters each characterized by a respective high-pass cut-off frequency within a predetermined input frequency spectrum characterizing said communication system;
• providing a low-pass filter section including a plurality of separate low-pass filters each characterized by a corresponding low-pass cut-off frequency within said input frequency spectrum;
• and
• directing said signal through a selected one of said high-pass filters and through a selected one of said low-pass filters to generate a band-pass filtered communication signal corresponding to one or more selected channels and having frequency characteristics corresponding to a selected passband having center frequency and bandwidth characteristics defined by corresponding said high-pass cut-off frequency and said low-pass cut-off frequency.

A method for spectrally analyzing a communication signal supplied by a multi-channel communication system, said method comprising the steps of:

• providing a high-pass filter section including a plurality of separate high-pass filters each characterized by a respective high-pass cut-off frequency within a predetermined input frequency spectrum characterizing said communication system;
• providing a low-pass filter section including a plurality of separate low-pass filters each characterized by a corresponding low-pass cut-off frequency within said input frequency spectrum;
• directing said signal through a selected one of said high-pass filters and through a selected one of said low-pass filters to generate a band-pass filtered communication signal corresponding to one or more selected channels and having frequency characteristics corresponding to a selected passband having center-frequency and bandwidth characteristics defined by corresponding said high-pass cut-off frequency and said low-pass cut-off frequency;
• and
• spectrally analyzing said band-pass filtered communication signal.