Through Glass Via (TGV) Based Microstrip Interdigital Bandpass Filters

Modern RF and microwave communication systems has imposed stringent requirements on filters including compact size, minimal insertion loss, low cost, and high selectivity. Glass has low-loss electrical characteristics and Through Glass Via (TGV) are suitable for advanced packaging and high-frequency applications. In this paper we present a 9th order asymmetrical coupled line interdigital bandpass filter with high selectivity and good stop band attenuation at the cut-off frequency. Interdigital bandpass filter has the characteristics of compact structure. Also the large spacing between the resonator elements, the tolerances required for manufacturing are relatively loose. The device is manufactured using laser processing and micro processing technology based on smooth and thin glass substrate to reduce the insertion loss. The thickness of the glass substrate is 0.45 mm. The loss tangent of the glass substrate is 0.0049. Design is implemented using High Frequency Structural Simulator (HFSS) v19 of ANSYS, a commercial software based on Finite Element Method (FEM). The RF performance of the prepared filter is in good agreement with the RF performance of the simulated filter. The measured insertion loss less than 1 dB with a center frequency of 9.8 GHz. The stop band with rejection peak below -50 dB in close proximity to two transmission poles in the pass band. And the total area of the device is 25.24 mm2.