This paper presents the design of a class of highly selective microstrip bandpass filters that consist of microstrip open-loop resonators that exhibit a single pair of attenuation poles at finite frequencies. A practical design technique for this class of filters is introduced, including tables and formulas for accurate and fast filter synthesis. Two design examples of a six-pole filter with a fractional bandwidth of 7.331% at 955 MHz and an eight-pole filter with a fractional bandwidth of 10.359% at 985 MHz are described. Theoretical and experimental results are presented. The compact size and the excellent performance of this class of filters have been demonstrated.

/pdf/design-of-highly-selective-microstrip-bandpass-filters-with-m2f7ovdm1t.pdf

Design of highly selective microstrip bandpass filters with a single pair of attenuation poles at finite frequencies

A novel bandpass filter using microstrip quarter-wavelength resonators is proposed. The proposed filter consists of the open stub inverter between quarter-wavelength resonators, which results in a compact design as well as low loss. The tapped open stub not only works as a K-inverter but also introduces an attenuation pole. The attenuation pole can be located at the upper or lower side of the passband by adjusting the open stub length. A two-pole Chebyshev bandpass filter is designed and tested at 1.99 GHz. A four-pole bandpass filter of elliptic-type performance is also designed and tested at 2.015 GHz.

New compact bandpass filter using microstrip /spl lambda//4 resonators with open stub inverter

In this paper, it is shown that the application of metamaterial resonators to the design of planar microwave filters provides a high level of miniaturization for such devices. Specifically, split-ring resonator, complementary split-ring resonator, and spiral resonator are used to synthesize microwave filters using the coupling coefficient approach. Some considerations in order to improve and control the coupling coefficients between resonators are exposed. The magnetic and electric character of the coupling coefficient is analyzed in detail, and a method to identify this coupling is proposed. Finally, several prototype device filters operative at S-band are provided to illustrate the proposed techniques

Miniaturized microstrip and CPW filters using coupled metamaterial resonators

In this paper, it is shown that the application of metamaterial resonators to the design of planar microwave filters provides a high level of miniaturization for such devices. Specifically, split-ring resonator, complementary split-ring resonator, and spiral resonator are used to synthesize microwave filters using the coupling coefficient approach. Some considerations in order to improve and control the coupling coefficients between resonators are exposed. The magnetic and electric character of the coupling coefficient is analyzed in detail, and a method to identify this coupling is proposed. Finally, several prototype device filters operative at S-band are provided to illustrate the proposed techniques.

This paper presents the design, fabrication, and characterization of a non-contact microwave resonator sensor for liquid–liquid interface detection. The core of this sensor is a microwave planar ring resonator tuned at 5.25 GHz with a Q factor of 180. The geometry and materials of the designed sensor were optimized for higher sensitivity by finite element modeling and simulations. Here we demonstrate the detection of different liquid–liquid interfaces such as water–olive oil, water–olive oil–ethanol, and rag layer samples using microwave resonator method. In the proposed sensor, the resonance frequency demonstrated a maximum variation of 5.7% for water to rag layer interface. To increase the accuracy of the sensor in the interface detection, quality factor is also measured and demonstrated a maximum variation of 85% depending on the materials. The proposed sensor provides a non-contact real time, cost-effective, robust method for interface detection, which has potential applications in the oil sands industry.

Microwave ring resonator-based non-contact interface sensor for oil sands applications

Novel compact elliptic-function narrow-band bandpass filters have been designed and fabricated. This new configuration consists of two identical microstrip open-loop resonators with coupled and crossing lines. A theoretical investigation has confirmed that this novel configuration is capable of providing elliptic-function filtering. Furthermore, the feasibility of this filter is verified experimentally. Centered at 2.039 GHz, the fabricated microstrip bandpass filter shows a measured 3-dB bandwidth of 2% and two deep notches in its stopband. In addition, the main circuit of this filter occupies only 2.5 cm/spl times/1.5 cm using a substrate with dielectric constant of 10.5, making it very attractive for applications in the mobile and personal communication systems (PCS's).

Kai Chang

Papers

Novel compact elliptic-function narrow-band bandpass filters using microstrip open-loop resonators with coupled and crossing lines