A miniature lumped element LTCC bandpass filter with high stopband attenuation for GPS applications

We present a new fully embedded low-temperature co-fired ceramic (LTCC) bandpass filter with the highest reported stopband attenuation in its class. The filter occupies only 0.03 λ x 0.05 λ x 0.004 λ of conventional low permittivity LTCC substrate. An advantage of this filter is that it is a true fourth-order design utilizing four multilayer L-C resonators. For the first time, measured results are shown for this novel topology and indicate an insertion loss of 6.7 dB and a return loss of 17.2 dB at the center frequency of 1.64 GHz. The stopband attenuation is greater than 50 dB at frequencies beyond ±300MHz of the passband, making this filter suitable for GPS environments with harsh spectral interference. This is believed to be the highest performing filter, in terms of out of band attenuation, realized in LTCC.