 The number of teeth , their size , and the gap between them are all design parameters that can be used to control the design of the filter . As an example , a filter with a 3 : 1 stopband might have five teeth across the width of the waveguide . The number of rows of teeth down the length of the waveguide primarily affects the stopband attenuation . The more rows of teeth , the better the attenuation , each row being equivalent to a lumped element circuit filter section . A filter with ten rows of teeth has a theoretical stopband rejection of around 80 dB and one with seven rows around 60 dB . 
