A Hybrid Design Technique to Improve the Structure and Performance of Microstrip Components

A hybrid approach to improving the structures of microstrip devices is presented in this study. The proposed technique includes a combination of simple series inductor (L) and capacitor (C) circuits with microstrip-based structures and transmission lines. In this method, the LC circuits are replaced with those parts of the microstrip components that need to act like a bandpass filter. Not only does this simple modification lead to a 100% size reduction, an infinite number of harmonics suppression and high frequency selectivity theoretically, but it will also result in a noticeable performance practically compared to the conventional arrangements of microstrip lines. To show the capability of the proposed method, two quarter-wavelength branches of a Wilkinson Power Divider (WPD) have been rectified and implemented using the LC circuit, which is called LC branches in this paper. Extreme size reduction and harmonic suppression in this implementation of the Filtering Power Divider (FPD) can be considered two important outcomes of this design technique. Furthermore, by tuning the LC circuit, the arbitrary numbers of unwanted harmonics can be blocked, and the operating frequency, the stopband bandwidth and the operating bandwidth could be opted optionally. The experimental result has verified the theoretical and simulated results of the proposed technique. The results clearly demonstrate the considerable potential of this technique to improve the design process of the microstrip devices with desirable specifications.

Bending Limit Tests for Ultra-Thin Liquid Crystal Polymer Substrate Based on Flexible Microwave Components

In this paper, bending limit tests for one ultra-thin liquid crystal polymer (LCP) substrate (Rogers 3850) based on the mechanical properties of flexible microwave microstrip components are presented. First, a set of 50 Ω microstrip lines, a band-pass filter, and a stepped impedance filter in X-band, are designed by using double clapped LCPs with 50 μm thickness of substrate and 18 μm thickness of copper, which is fabricated by conventional photolithography. Then, the limit tests of the flexibility of the LCP microwave microstrip components are presented, and the range of the bending limit radius, from 1 mm to 0.75 mm, is demonstrated from the testing results. It is found that the cause for component failure is fracture of the copper (18 μm thickness) laminate, according to the bending limit test experiments. Finally, the analysis of the reasons for the collapse of the microwave components, under bending situations, is explored. The results from this work would be useful for further designs of the flexible microwave devices and systems on LCP substrates, with compact sizes and good performance.