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Compact microstrip bandpass filters (second- and fourth-order) are proposed based on the folded quarter-wavelength (λ/4) resonators, which are mainly coupled through the shunt inductors connected to the ground. By introducing a cross-coupling capacitance directly between the input and output ports of the second-order filter, a pair of transmission zeros may be created to improve the selectivity. Moreover, by an extension of the proposed second-order filter with the incorporation of an additional cross-coupling capacitance, a fourth-order filter is also proposed in which two pairs of transmission zeros may be created to improve both the selectivity and stopband rejection. The proposed fourth-order filter also has the merits of small circuit area and no spurious response up to 3f0, where f0 is the passband center frequency. To provide effective design tools, simple equivalent-circuit models are also established.