Fabrizio Gentili

Design and Multiphysics Analysis of Direct and Cross-Coupled SIW Combline Filters Using Electric and Magnetic Couplings

In this paper, combline substrate integrated waveguide (SIW) filters using electric and magnetic couplings are thoroughly studied. Thus, a negative coupling scheme consisting on an open-ended coplanar probe is proposed and analyzed in detail. Several in-line 3-pole filters at C-band are designed, manufactured and measured showing how the presented approach can be used for implementing direct couplings while enabling an important size reduction and improved spurious-free band compared to conventional magnetic irises. A fully-packaged quasi-elliptic 4-pole filter is also designed at 5.75 GHz showing how the negative coupling structure can be used for introducing transmission zeros by means of cross-couplings between non-adjacent resonators. Finally, average and peak power handling capabilities of these filters have been also analyzed from a multiphysics point of view. Measured results validate the theoretical predictions confirming that combline SIW filters can handle significant levels of continuous and peak power, providing at the same time easy integration, compact size and advanced filtering responses.

Quasi-elliptic filter based on SIW combline resonators using a coplanar line cross-coupling

In this paper, a novel electric coupling for Substrate Integrated Waveguide (SIW) bandpass filter is proposed, designed and applied in combline SIW structure. The electric coupling is obtained by means of an open-ended coplanar transmission line which couples combline SIW resonators. The proposed coupling structure can introduce mixed electric and magnetic coupling thus helping to enhance the filter selectivity. To prove the concept, a quasi-elliptic cross-coupled 4-pole SIW filter is designed including transmission zeros (TZs) at both sides of the pass-band. The filter is centred at 5.75 GHz with absolute bandwidth of 114 MHz (2%). The TZs are set at 5.63 GHz and 5.87 GHz. The measured results confirm the performances of the proposed structure, showing the advantages of wider upper stop-band, higher compactness and easy integration with planar structures.

Practical considerations in the design of monoblock TM dielectric resonator filters with additive manufacturing

This paper describes the practical aspects involved in the development of TM dielectric resonator filters in a single block made out of ceramic material. In order to manufacture these structures, the additive manufacturing technique known as Lithography-based Ceramic Manufacturing (LCM) has been employed. To demonstrate the feasibility of this approach, a simple prototype has been manufactured and measured.

PCB RF probe landing pads for multiline deembedding

The interface between a probe station and an active or passive component on a printed circuit board is of great importance for RF systems operating in the mm-wave frequency range. The landing pads provide the transition between a coplanar measurement device and a microstrip interface. This paper addresses the design issues of such landing pads focusing on finding the optimal design enabling multiline deembedding with a measurement error better than 0.1dB.

Triple mode dielectric-loaded cavity band pass filter

This paper presents a compact triple mode band pass filter (BPF) using dielectric-loaded cylindrical cavity that allows the realization of three transmission zeros. This class of triple mode resonator utilizes the degenerate TE11 modes and the single TM01 mode. Coupling structure is based on choosing the proper resonator height and input/output feeding probe position (angle Ø) to achieve the desired perturbation between the degenerate modes. Therefore, no additional space nor coupling screws is needed. A three-pole BPF is designed to verify this approach at 2.08 GHz centre frequency with bandwidth of 42 MHz at -20 dB return loss. The introduced triple mode resonator can be used as a building block in the design of diplexers and sophisticated higher-order filters.

A TE 11 dual-mode monoblock dielectric resonator filter

A novel TE11 monoblock dual-mode dielectric resonator filter is presented in this paper. The proposed filter is made of a single piece of ceramic with silver plated external surfaces and metallic lids for hosting tuning elements. The dominant TE11 dual-mode is supported by H-shape dielectric resonator having εr =45. The resonator is ultra-compact in size and offers a maximized space utilization since no metallic housing is required. In addition, the proposed resonator offers a high unloaded quality factor, reasonably wide spurious window and lend itself to implement tunability. One prototype filter operating at 1.96 GHz with 50-MHz bandwidth is designed.

Fully reconfigurable filter based on a microstrip patch resonator with low-voltage driving

An approach to bandwidth- and frequency-reconfigurable planar filters is proposed. Switching elements are used in a modified dual-mode microstrip resonator to independently tune the centre frequency (up to 10 %) and the bandwidth (4%) of the filter. In order to demonstrate the feasibility of the proposed approach the design of a 2nd-order tunable filter is presented along with simulation and measurement results. Measurement results showed an average Insertion Loss (IL) of 2 dB and return loss better than 12 dB. Bandwidth and frequency tuning range are 4% and 10% respectively as simulated.

p-i-n-Diode-Based Four-Channel Switched Filter Bank With Low-Power TTL-Compatible Driver

The design of a four-channel switched filter bank in the S- and C-band using p-i-n-diode switches is described. Narrowband filters (3.2%-3.5%) are designed on suspended substrate stripline. The biasing circuit allows the switches to be driven with transistor-transistor-logic-compatible voltages and minimum biasing current. The average insertion loss measured is 3.6 dB corresponding to a Q-factor of 580. Spurious responses were suppressed from dc to roughly 19 GHz.