Microwave Filter Synthesis

Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GH...

Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GH...

A 2nd order bandpass filter topology is presented. It employs two single mode ring resonators that coupled via a quarter-wavelength coupled-line to exhibit a pseudo-elliptic bandpass response. The advantage of the topology is that, having only one coupled-line in the structure has reduced the complexity of the circuit to obtain a narrowband response of less than 9% with high rejection level. Prototypes filters were realized to validate the concept using microstrip technology. It was proven that the measurement results had shown good agreement with those from the simulation.

This paper presents a class of side-coupled shorted coupled-lines resonator topology for narrowband bandpass filter applications. The base topology is constructed by interconnecting two shorted quarter-wavelength coupled-line sections to exhibit a single resonance bandpass filter response. The degree of order of the resonator can be increased by inter-connecting additional shorted quarter-wavelength coupled-line sections to the base cell. Based on this concept, a 3 rd order bandpass filter is constructed by inter-connecting two new shorted quarterwavelength coupled-line sections into the base cell. The advantage of this new 3 rd order filter arrangement is that, the affect of inter-connecting the shorted coupled-line sections had caused cross-coupling between the adjacent coupled-lines to produce a transmission zero at the lower passband. For compactness, all the coupled-lines of the 3 rd order filter are meandered, resulting to 40% of size reduction. To prove the concept, the 3 rd order bandpass filter was simulated using fullwave electromagnetic simulation tool. The filter was designed at 1 GHz on microstrip substrate type Roger RO3210. A prototype of the 3 rd order bandpass filter was fabricated and the results are compared and are found agreable.

The detailed synthesis of a direct access ring filter topology fully controlled with the following targeted specification (center frequency, low transmission zero frequency, and matching level in the passband) is hereby presented. For this topology, the lowest achievable bandwidth is limited by technological constraints. Thereby a solution consisting in adding capacitive loads is proposed. The associated synthesis is also given and discussed. Both syntheses are illustrated with 60 GHz integrated planar filters implemented in the IHP 130 nm BiCMOS technology. Various 3 dB fractional bandwidths from 18 to 8% are targeted, some of them require the implementation of the capacitive loaded solution. The latter allows us to lower the bandwidth limit of the nominal topology as well as to get a high miniaturization, up to 3.4, depending on the capacitance value. Thanks to good measurement results, this implementation highlights the high efficiency, reliability, and versatility of the synthes...

We propose a compact planar passband frequency selective surface (FSS) operating at the resonance frequency of 3.81 GHz. The proposed FSS is composed of single layer of the Archimedean spiral type with the interdigital capacitance between the corners of metallic patches printed on one side of the substrate. Compared to the operating wavelength, the size of the proposed single layer FSS is 0.066λ0 (λ0 is the free space wavelength at 3.81 GHz). The performance such as transmission and reflection coefficient of the proposed FSS demonstrates excellent resonance stability for different polarization and different incident angles. Finally, the optimized simulated results are validated with measured results by a fabricated prototype of 31×31 array elements on 170×170 mm2 substrate area.

Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GH...

Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GH...

This paper presents a very selective wideband-bandpass filter topology, which is more compact, compared to a conventional coupled line filter and requires much lesser adjustment of parameters. The new topology consists of two identical onewavelength rings that are combined with four identical quarter-wavelength coupled-lines, resulting in 7th order bandpass response. The use of the rings allows larger bandwidth with lower coupling level of the coupled-lines. The filter is simulated and fabricated using microstrip technology on FR4 epoxy glass substrate and the measurement results are found to be in good agreement with the simulation results.

This paper presents two microwave bandpass filter topologies which are based on two different ways of seriescascading two quarter-wavelength side-coupled ring resonators. In the first topology, a quarter-wavelength impedance inverter is used to connect the two rings. As each ring gives two poles, a 4 th order bandpass filter is obtained from the topology. The impedance inverter is replaced by a quarter-wavelength coupled line in the second topology. In this case, two half-wavelength resonators are formed at the interconnection between the rings and the coupled line, leading to the creation of an extra of two poles in the passband response. Thus, a 6 th order filter is obtained from the second topology. Both topologies are realized at 2 GHz center frequency using microstrips on epoxy-glass substrate. Measurement results are found to be in good agreement with the simulations with very high out-of-band rejection level.