High Rejection Miniaturized Bandpass Filter with Controllable Transmission Zero using LTCC Technology

A miniaturized and high rejection band pass filter (BPF) realized by low-temperature cofired ceramic technology are presented in this paper. The design consists of conducting patterns distributed on different dielectric layers. Grounded combline resonators loaded with capacitors are used as a basic topology for the design of the proposed filter. The capacitor has been realized using metal-insulator-metal concept in LTCC technology. To achieve the rejection in the BPF, a transmission zero has been realized by introducing a non-adjacent coupling. The location of transmission zeros can be controlled using the length of this U-shaped coupling transmission line. An extra coupling pad has been introduced to maintain the coupling coefficients between the resonators. A filter has been designed and simulated for Ku-band (12.7-13.0) GHz with 1-dB absolute bandwidth of 310 MHz. A rejection of 80 dB has been achieved at 16.10 GHz. The overall size of the filter is 6.5 mm x 2.58 mm x 0.48 mm.

I. Introduction

Low temperature co-fired ceramic (LTCC) technology is a multilayer technology for the production of RF and microwave components, it is based on combination of ceramic and metal layers, therefore, it is suitable for passive component realization. Depending on the configuration, passive inner structure occupies several layers where the connection between them is through via hole to the top layer. LTCC technology has several advantageous: high thermal conductivity, low resistance, dielectric losses and multilayer integration of passive components. These advantages can be utilized in systemin-package (SiP) developments where passive and active components are integrated into a single package. But the realization of compact RF SiPs, are limited due to the large size of the highly selective higher-order filter. Fig. 1.

Proposed bpf.