To meet the requirements of ever-changing wireless communications on the small band pass filter

and to solve the problems of linearity

rectangular coefficient

insertion loss

size and other issues exist in the traditional type of filter

the author presented the design of corss-coupled microstrip bandpass filters that consist of coupled microstrip square open-loop resonators.These filters exhibit a single pair of attenuation poles

so it represents sharper filter shirt and higher selectivity.The synthesis method of this class of filters has been given.One design example of a six-pole filter was described.Full wave simulation result was presented.The compact size and high selective of this class of filters have been demonstrated.