ABS speed signal input filter having mid-frequency attenuation

A system for controlling at least one vehicle wheel brake, said system comprising:

• a speed sensor having an output port, said speed sensor adapted to monitor the speed of a vehicle wheel associated with the controlled wheel brake and operable to generate a wheel speed signal at said sensor output port, said wheel speed signal having a frequency which is proportional to the speed of said associated vehicle wheel;
• a filter having an input port and an output port, said filter input port electrically coupled to said speed sensor output port, said filter including at least one low pass filter section which is electrically connected to said filter input and output ports, said low pass filter section operative to pass wheel speed signals within a range from zero hertz to a predetermined first frequency which is greater than zero, said low pass filter section attenuating wheel speed signals which have a frequency which is greater than said first predetermined frequency and rejecting noise signals at frequencies above said first predetermined frequency, said filter also including a mid-range frequency filter section electrically coupled to said low pass filter section, said mid-range frequency filter section having an attenuation which first increases and then becomes generally constant as the frequency of said wheel speed signal increases over a predetermined mid-range frequency band, said mid-range frequency filter section operable to reject noise signals having magnitudes which are less than said wheel speed signal over said mid-range frequency band, said mid-range frequency band extending from a second predetermined frequency to said first predetermined frequency, said second predetermined frequency being less than said first predetermined frequency and greater than zero hertz, said low pass filter section co-operating with said mid-range filter section to produce a filtered speed signal at said filter output port;
• and
• a brake system control module having a speed signal input port which is electrically coupled to said filter output port, said control module adapted to be connected to the controlled wheel brake and being responsive to said filtered wheel speed signal to selectively control the actuation of the controlled wheel brake.