Synthesis of Vertical Interdigital Filters Using Multilayered Technologies

Abstract

International audienceTaking advantage of multilayer technologies, a vertical evolution of the interdigital topology is proposed with its associated synthesis method. In order to validate this filter topology, a 4-pole filter, centered at 10 GHz, and an 11-pole filter, centered at 6 GHz, have been designed and fabricated using low-temperature co-fired ceramic (LTCC) technology. Two other multipole filters have also been designed showing a large surface reduction with respect to equivalent interdigital filters. LTCC technology has been chosen for fabricating the filters, but the proposed topology can also be implemented with other multilayer technologies

Self‐packaged miniature high‐order bandpass filter for wideband applications

“…A small discrepancy can be found between the simulated and measured results in Figure . Due to the loss from the roughness, copper and the substrate, the quality factor of the resonator reduces a little bit, which results in a round edge at the passband edge of the filter as well as a relatively narrow passband . The tolerance of fabrication leads to a little bit worse S11, which is smaller than −20 dB from 9.5 to 14.5 GHz.…”

“…It should be noted that a transmission zeros located at around 17.0 GHz is found in the simulated and measured results although it is not existed in the response of the coupling matrix in Equation 1. This is due to couplings among nonadjacent resonators and can be adjusted by modifying the geometry shapes of the resonators, as investigated in the literature . Moreover, to reduce effectively the footprint of the filter, a high‐order filter can be designed using a multiple‐layer technology such as the low‐temperature co‐fired ceramic technology or liquid crystal polymer technology, which, however, is sensitive to the fabrication tolerance, requires a high cost and sophisticated process, and has a relatively large insertion loss because of the small quality factor of the resonators embedded inside the substrate .…”

“…In addition, as the frequency space among fundamental and superior resonating modes of the SIW resonator is relatively narrow, it is hard to design wideband, that is, more than 30% fractional bandwidth, filters using the SIW technique. Instead, quasi lump resonators, dissimilar quarter wavelength resonators or interdigital topologies are more adorable for the design of miniature wide bandpass filters.…”

Improved side‐coupled three‐line wideband bandpass filter

“…The popular way to design wideband and UWB filters is multimode resonators, but these filters often present large size. Another easy method to achieve wideband filters is multiple vertical coupled single‐mode resonators, however, the fabrication cost of multilayer structure is expensive.…”

A dual‐band balanced amplifier using three‐layer technology

“…To decrease the circuit area, the multilayer circuit technique has become a common circuit minimization method in radio frequency integrated circuits. The low‐temperature cofired ceramic (LTCC) technology is the representative method in the radio or microwave circuits to reduce circuit areas . However, the LTCC owns complex production process in practical applications.…”