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.

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

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.

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

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.

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

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.

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

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]

/pdf/a1-resonators-in-128-y-cut-lithium-niobate-with-7qzey9qrsr.pdf

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

A novel MEMS enabled W-band waveguide transmission phase shifter is presented. It consists of a ridge waveguide half-wavelength long resonator and an electrostatically actuated tilting micro-mirror MEMS. Operation is described as a distributed variable shunt capacitance realized by rotating, anti-parallel oriented MEMS conductive fingers. A deflection of the fingers of 0o...7.5o results in a phase shift variation of 0o...35 at 102GHz with an insertion loss of less than 0.73 dB.

Waveguide-Mounted RF MEMS for Tunable W-band Analog Type Phase Shifter

This paper presents an implementation of an ISM RFID module capable of simultaneous wireless information and power transfer, that is implemented in a three-layer configuration. The top two layers of the RFID module are used for the low profile, high gain (8 dBi), circular polarization antenna implementation. The proposed antenna consists of four radiating L-shaped patches on the top layer, which are fed from a circular power divider. The energy harvesting (EH) system and the communication module are implemented on the bottom third layer. A four-port coupler is used to direct 85-90% of the received power from the antenna to the EH system and the remaining to the communication module. TI CC2530 IC is used, and it is powered from the PMU of the EH system. With -13 dBm input power, at the coupler’s port 3, the communication module can support TX/RX communication cycle lasting up to 3.5 ms.

An ISM-Band RFID Module for Simultaneous Wireless Information and Power Transfer with High Gain Antenna in Multi-Layer Configuration

This letter reports on a new class of agile helical resonators and bandpass filters (BPFs) with continuously-tunable center frequency. RF tuning is achieved by altering the liquid metal (LM) volume within an additively-manufactured plastic tube that has the shape of a helix and forms the inner conductor of the helical resonator. A low-cost and versatile integration scheme using 3-D printing and pneumatically-actuated Galinstan is proposed. For proof-of-concept validation purposes, a helical resonator with center frequency tuning between 1 and 1.5 GHz, and unloaded quality factor between 131 and 145 was manufactured and measured. Two BPF porotypes namely: 1) two-pole BPF with center frequency tuning between 1.16 and 1.49 GHz and insertion loss (IL) < 2 dB and 2) three-pole BPF with center frequency tuning between 1.18 and 1.49 GHz, and IL < 2.1 dB, were manufactured and tested at $L$ -band.

https://ieeexplore.ieee.org/ielx7/7260/4357983/09727089.pdf

Continuously Tunable 3-D Printed Helical Resonators and Bandpass Filters Using Actuated Liquid Metals

Surface acoustic wave (SAW) resonator-based bandpass filters (BPFs) with enhanced fractional bandwidth (FBW)-i.e, that is wider than the electromechanical coupling coefficient $kt^{2}$ - quasi-elliptic transfer functions are reported. They are based on cascaded acoustic-wave-lumped element (AWLR) multi-resonant stages that are shaped by one SAW resonator and one or more lumped-element (LE) resonators. Each of the multi-resonant stages contributes to the overall transfer function one pole and two transmission zeros (TZs). Thus, the proposed three-stage BPF configuration exhibits a transfer function shaped by three poles and six TZs. A detailed RF design methodology using analytical equations is provided for each multi-resonant AWLR stage. Various design examples for each stage and the overall three-pole/6-TZ BPF are presented. For proof-of-concept demonstration purposes a three-pole/six-TZs filter prototype was designed, manufactured and measured at 916.6 MHz. It exhibits the following characteristics: Center frequency: 916.6 MHz, FBW: $1.26kt^{2}$ and minimum insertion loss 1.88 dB that corresponds to an effective quality factor of 6000.

Quasi-elliptic SAW Filters Using Multi-Resonant Acoustic-Wave Lumped-Element Resonator Stages

Two architectures of fully-planar differential-mode dual-band bandpass filters (DB-BPFs) with enlarged common-mode-suppression bandwidth are reported. The first one, which aims at designs with broadly-separated wide passbands, exploits the loading of extra lines in its balanced symmetry plane. Thus, multiple common-mode transmission zeros (TZs) are created to make wider the DB-BPF common-mode-rejection range. The second one can be used for realizations with closely-spaced passbands and employs a properly-balanced quasi-bandpass-type DB-BPF topology. In this case, the common-mode-mitigation bandwidth broadening is performed by adequately selecting the type of implementation for the short-circuit terminations of its resonating lines— i.e., virtual or physical short circuits in the differential-mode operation—. For experimental-validation purposes, two microstrip DB-BPF prototypes are manufactured and tested.

Dimitra Psychogiou

Papers

Waveguide-Mounted RF MEMS for Tunable W-band Analog Type Phase Shifter

An ISM-Band RFID Module for Simultaneous Wireless Information and Power Transfer with High Gain Antenna in Multi-Layer Configuration

Continuously Tunable 3-D Printed Helical Resonators and Bandpass Filters Using Actuated Liquid Metals

Quasi-elliptic SAW Filters Using Multi-Resonant Acoustic-Wave Lumped-Element Resonator Stages

Two Topologies of Balanced Dual-Band Bandpass Filters with Extended Common-Mode-Suppression Bandwidth