Microstrip bandpass filters on substrates with high permittivities

Abstract

A new class of compact microstrip bandpass filters, the stepped impedance resonators of which are located close together at a gap of 0.1-0.2 mm, is described. Basic two and three element sections of microstrip filters, which are designed around stepped impedance impedance resonators used to implement tiny selective devices with overall sizes and characteristics comparable to those of microwave ceramic filters, are proposed. It is justified that the mentioned filters can be equipped with closely neighboring metallic shields whose heights are equal to the substrate thickness. As a consequence, these filters turn out to be thin ner. The frequency responses of experimental microstrip filters operating at frequencies of 1.75-2 GHz and manufactured on the 1 mm thick substrates with the permittivity ε r = 100 have been analyzed. The three pole microstrip filter with a shield (its operating frequency is 1.96 GHz, and sizes are 5 × 5 × 1.5 mm) has been simulated. It is demonstrated that new microstrip filters can be competitive with low sized ceramic filters in certain applications.

Duplexer designed on the basis of microstrip filters using high dielectric constant substrates

“…V. Zakharov and S. A. Rozenko section of a microstrip line placed "near" these reso nators. The results presented below were borrowed from [3], they are of great interest for construction of the filters used in duplexers. In Fig.…”

“…Table 2 does hot contain data on the height of the microstrip duplexer, because measurements were per formed without a metal screen. It is shown in [3] that a bandpass filter with small gaps between resonators (see Fig. 2a) can operate with a closely placed metal screen.…”

“…Yesterday [3], compact microstrip bandpass filters manufactured on high dielectric constant substrates were proposed. These filters contain stepped imped ance resonators placed near each other with a gap of 0.1-0.2 mm.…”