Dimitra Psychogiou

Bio: Dimitra Psychogiou is an academic researcher from University of Colorado Boulder. The author has contributed to research in topics: Band-pass filter & Resonator. The author has an hindex of 18, co-authored 177 publications receiving 1292 citations. Previous affiliations of Dimitra Psychogiou include Purdue University & École Polytechnique Fédérale de Lausanne.

Reflectionless Adaptive RF Filters: Bandpass, Bandstop, and Cascade Designs

Abstract: A class of frequency-reconfigurable input-reflectionless/absorptive RF/microwave filters is presented. They consist of tunable complementary-duplexer architectures that are composed of a main and an auxiliary channel with opposite filtering transfer functions. By loading the auxiliary channel with a reference-impedance resistor and by taking the output node of the main channel as the output terminal of the overall circuit, a filtering network of the same type of the main channel with theoretically perfect input-reflectionless behavior at all frequencies can be realized. This technique can be applied to design spectrally agile completely input-reflectionless filters with any kind of transfer function, such as low-pass, high-pass, and single/multiband bandpass/bandstop filters. The theoretical analysis of the first-order absorptive bandpass/bandstop filtering sections based on a coupling-matrix formulation is detailed. Furthermore, the synthesis of high-selectivity reflectionless filters either by cascading multiple first-order cells or using high-order channels in a single complementary duplexer is also described. For practical-demonstration purposes, frequency-tunable lumped-element and microstrip prototypes are manufactured and characterized. They correspond to first- and second-order bandpass/bandstop filters. In addition, their in-series cascade connection is used to implement a bandpass filter with spectrally controllable passband and out-of-band notches.

Single/multi-band Wilkinson-type power dividers with embedded transversal filtering sections and application to channelized filters

Abstract: This paper addresses the exploitation of signal-interference concepts for the realization of single/multi-frequency Wilkinson-type filtering power dividers in planar/lumped-element technologies. By embedding transversal signal-interference filtering sections into the arms of conventional Wilkinson-type power-divider topologies, RF/microwave power-distribution actions with intrinsic mono/multi-band bandpass filtering capabilities can be obtained. Analytical equations and rules for the theoretical synthesis of this dual-function device are derived. The generalization of the approach to multi-stage schemes for enhanced-performance designs or for the shaping of frequency-asymmetrical responses is also discussed. Furthermore, for practical demonstration, three prototypes are developed and characterized. They are a microstrip quad-band circuit for the 1–5 GHz range, a dual-band lumped-element device for the band of 0.2–0.6 GHz, and a new type of two-branch channelized active bandpass filter at 3 GHz that makes use of single-band versions of this dual-behavior component as signal-division/combination blocks.

Balanced Symmetrical Quasi-Reflectionless Single-and Dual-Band Bandpass Planar Filters

Abstract: Microwave planar balanced single-/dual-band bandpass filters (BPFs) with symmetrical quasi-reflectionless differential-mode behavior are presented in this letter. They are made up of a direct single-/dual-band BPF branch with virtually short-ended stubs in differential-mode operation, whose input and output accesses are loaded with stub-loaded-type single-/dual-band bandstop filter (BSF) branches that are terminated with a resistor. These BSF branches exhibit a quasi-complementary transfer function with regard to the one of the BPF branch and absorb the differential-mode input-signal energy not transmitted by the filter to achieve quasi-reflectionless capabilities. The theoretical foundations of the proposed balanced quasi-absorptive single-/dual-band BPFs and synthesis examples are given. Furthermore, for experimental-demonstration purposes, microstrip prototypes of 3-GHz second-order single-band and 2.85/3.15-GHz first-order dual-band BPFs are manufactured and characterized.

Multi-Stub-Loaded Differential-Mode Planar Multiband Bandpass Filters

Abstract: A new type of RF $/$ microwave differential-mode planar multiband bandpass filters (BPFs) are presented. Each symmetrical half of the proposed balanced filtering architecture is composed of the in-series cascade of $K$ $N$ -stub-loaded cells through $K-1$ inter-connection transmission-line segments to synthesize a differential-mode transfer function with $N$ $K$ th-order passbands. Additional features of this balanced multiband BPF topology are as follows: 1) generation of transmission zeros at both sides of all differential-mode passbands; 2) high common-mode power-rejection levels within the differential-mode passband ranges; 3) scalability to any number of arbitrary-order differential-mode transmission bands; and 4) lack of electromagnetic couplings in its physical structure. The theoretical foundations of the engineered balanced filter approach, along with guidelines to design the differential-mode transfer function and to attain optimum in-band common-mode power-attenuation characteristics, are expounded. Furthermore, for experimental-demonstration purposes, a third-order triple-band microstrip prototype with differential-mode passbands that are located within the range 1.4–3 GHz is manufactured and characterized.

Single/Multi-Band Coupled-Multi-Line Filtering Section and Its Application to RF Diplexers, Bandpass/Bandstop Filters, and Filtering Couplers

Abstract: A type of compact single/multi-band coupled-multi-line filtering section and its application to the design of RF filtering devices are presented. This one-port filtering cell is made up of ${N+1}$ intercoupled quarter-wavelength transmission-line segments for the generation of a transfer function with a total of ${N+1}$ transmission zeros (TZs) distributed at both sides of all its ${N}$ first-order passbands when arranged in the transmission mode. Design formulas for the produced poles and TZs of its corresponding normalized coupling-routing diagram and illustrative theoretical responses are provided. Furthermore, for experimental demonstration purposes, microstrip prototypes of the following RF filtering components that exploit the conceived filtering section are manufactured and measured: 1) a quasi-elliptic-type diplexer with a dual-band bandpass filter (BPF) junction; 2) two input-reflectionless triple-band BPF and bandstop filter (BSF) circuits; and 3) an out-of-phase equal-power-division bandpass filtering coupler with input-quasi-reflectionless behavior.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

Abstract: Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

Reflectionless Adaptive RF Filters: Bandpass, Bandstop, and Cascade Designs

Abstract: A class of frequency-reconfigurable input-reflectionless/absorptive RF/microwave filters is presented. They consist of tunable complementary-duplexer architectures that are composed of a main and an auxiliary channel with opposite filtering transfer functions. By loading the auxiliary channel with a reference-impedance resistor and by taking the output node of the main channel as the output terminal of the overall circuit, a filtering network of the same type of the main channel with theoretically perfect input-reflectionless behavior at all frequencies can be realized. This technique can be applied to design spectrally agile completely input-reflectionless filters with any kind of transfer function, such as low-pass, high-pass, and single/multiband bandpass/bandstop filters. The theoretical analysis of the first-order absorptive bandpass/bandstop filtering sections based on a coupling-matrix formulation is detailed. Furthermore, the synthesis of high-selectivity reflectionless filters either by cascading multiple first-order cells or using high-order channels in a single complementary duplexer is also described. For practical-demonstration purposes, frequency-tunable lumped-element and microstrip prototypes are manufactured and characterized. They correspond to first- and second-order bandpass/bandstop filters. In addition, their in-series cascade connection is used to implement a bandpass filter with spectrally controllable passband and out-of-band notches.

Single/multi-band Wilkinson-type power dividers with embedded transversal filtering sections and application to channelized filters

Abstract: This paper addresses the exploitation of signal-interference concepts for the realization of single/multi-frequency Wilkinson-type filtering power dividers in planar/lumped-element technologies. By embedding transversal signal-interference filtering sections into the arms of conventional Wilkinson-type power-divider topologies, RF/microwave power-distribution actions with intrinsic mono/multi-band bandpass filtering capabilities can be obtained. Analytical equations and rules for the theoretical synthesis of this dual-function device are derived. The generalization of the approach to multi-stage schemes for enhanced-performance designs or for the shaping of frequency-asymmetrical responses is also discussed. Furthermore, for practical demonstration, three prototypes are developed and characterized. They are a microstrip quad-band circuit for the 1–5 GHz range, a dual-band lumped-element device for the band of 0.2–0.6 GHz, and a new type of two-branch channelized active bandpass filter at 3 GHz that makes use of single-band versions of this dual-behavior component as signal-division/combination blocks.

A Balanced-to-Unbalanced Microstrip Power Divider With Filtering Function

Abstract: In this paper, a balanced-to-unbalanced microstrip power divider based on branch lines with several stubs and one resistor is proposed. The functions of power dividing, frequency selectivity, isolation between output ports, and common-mode suppression can be realized at the same time. The even–odd-mode equivalent circuits combining with the standard S-parameters and the mixed-mode S-parameters are adopted to derive the analytical equations at the center frequency. One or two transmission zeros can be achieved to enhance the out-of-band suppression. The center frequency, bandwidth, isolation, common-mode suppression, and the frequencies of transmission zeros can be controlled by the design procedure. To verify the theoretical prediction, two fabricated prototypes are designed and compared. One gets 7.7% 1-dB bandwidth with 0.6-dB insertion loss and one transmission zero. The other gets 1-dB bandwidth of 5% with 0.7-dB insertion loss and two transmission zeros. The isolation and common-mode suppression for both prototypes are better than 15 and 20 dB within the whole passband, respectively.

A1 Resonators in 128° Y-cut Lithium Niobate with Electromechanical Coupling of 46.4%

Abstract: In this work, we present first-order antisymmetric (A1) mode resonators in 128° Y-cut lithium niobate (LiNbO3) thin films with electromechanical coupling coefficients ( $k^{2}$ ) as large as 46.4%, exceeding the state-of-the-art. The achievable $k^{2}$ of A1 in LiNbO3 substrates of different orientations is first explored, showing X-axis direction in 128° Y-cut LiNbO3 among the optimal combinations. Subsequently, A1 resonators with spurious mode mitigation are designed and fabricated. In addition to the large $k^{2}$ , the implemented devices show a maximum quality factor ( $Q$ ) of 598 at 3.2 GHz. Upon further optimization, the reported platform can potentially deliver a wideband acoustic-only filtering solution in 5G New Radio. [2020–0003]