Showing papers on "Insertion loss published in 2021"

60-GHz Compact Dual-Mode On-Chip Bandpass Filter Using GaAs Technology

Abstract: A 60-GHz compact dual-mode on-chip bandpass filter (BPF) is presented using gallium arsenide (GaAs) technology. To demonstrate the working mechanism of the proposed BPF, an LC equivalent circuit model is conceived and analyzed for further investigation of the transmission poles and zeros. Finally, a prototype of the BPF is fabricated and tested to validate the proposed idea, whose simulated and measured results are in good agreement. The measurements show that it has a center frequency of 58.7 GHz with a bandwidth of 18.4%, and the minimum insertion loss within the passband is 2.42 dB. The chip size, excluding the feedings, is about 0.158 mm $\times0.344$ mm.

Wideband and Low-Loss Surface Acoustic Wave Filter Based on 15° YX-LiNbO₃/SiO₂/Si Structure

Abstract: With the development of the radio frequency technique, the explosive growth of transmitted data in 5G era puts higher requirements on surface acoustic wave (SAW) filter bandwidth In this work, 15°YX-LiNbO3(LN)/SiO2/Si multilayer structure was proposed, where both LN and SiO2 films possess uniform thickness and the interfaces between films are quite clear With hierarchical cascading algorithm, the spurious resonance that resulted from Rayleigh mode was minimized through the modulation of Cu electrode thickness One-port resonators measurement results confirm a high electromechanical coupling coefficient of shear horizontal mode ranging from 225% to 252% Furthermore, a ladder-type filter with a center frequency of 1279 MHz and a large fractional bandwidth of 202% was successfully fabricated Excellent bandpass filtering properties were achievable with minimum insertion loss of 08 dB and in-band fluctuation less than 09 dB Multilayer structure SAW filters also exhibited a temperature coefficient of frequency of −577 ppm/°C and a power durability of 33 dBm, which are both significant improvements compared with that of devices built on bulk 15°YX-LN substrate This work provides an effective solution for wideband and low-loss radio frequency filters in 5G communication systems, suitable for large-scale application and commercial promotion

Wide-Angle Broadband Rasorber for Switchable and Conformal Application

Abstract: A novel wide-angle and broadband rasorber is presented incorporating several advances. To broaden the bandwidth, we introduce a new type of frequency selective surface (FSS) in the bottom layer of the rasorber. This strategy increases the upper and lower absorption bandwidths while reducing the insertion loss at transmission window. Furthermore, a new top resistive layer is proposed via the loading of electric field coupled resonator elements on a cross-dipole structure. The proposed design offers both, an angularly stable performance and a thin structure that can be fabricated on a single dielectric substrate. To enable switchability, p-i-n diodes are employed and a reconfigurable rasorber/absorber is designed where a new concept of “lossy/lossless” top layer is investigated and established as the best choice among other switchable designs. Equivalent circuit models are constructed for both active and passive designs to provide physical insight into their operation. Finally, to enable deployment of the rasorber over curved geometries, these advances are incorporated into a conformal structure. Three separate prototypes are fabricated and good agreement is obtained between design predictions and experimental results.

High-Performance Surface Acoustic Wave Devices Using LiNbO 3 /SiO 2 /SiC Multilayered Substrates

Abstract: The rapid development of the fifth-generation (5G) wireless system is driving strong demand for high-performance radio frequency filters. This work studies shear horizontal surface acoustic wave (SAW) devices using 15°-rotated $Y$ -cut $X$ -propagating (15°Y-X) LiNbO3/SiO2/SiC multilayered substrates. Single-crystalline 15°Y-X LiNbO3 films are bonded to SiO2/SiC handling substrates by the smart cut technology. On the basis of accurate finite-element-method simulations, LiNbO3/SiO2/SiC wafer configurations are optimized to suppress spurious resonance due to Rayleigh-mode and transverse-mode responses, and one-port resonators with a clean spectrum, a high electromechanical coupling coefficient of 22.00%, and an admittance ratio (impedance ratio) over 65 dB are successfully implemented. Based on the characteristics of the resonators, high-performance filters with a center frequency of 1.28 GHz, a large 3-dB fractional bandwidth of 16.65%, and a low minimum insertion loss of 1.02 dB are successfully designed and fabricated. Furthermore, no ripples in the passband of the filters are observed. Additionally, the filters exhibit a temperature coefficient of center frequency of −63.8 ppm/°C and a large power durability of 33.2 dBm. This work confirms the high performances of the SAW devices using the 15°Y-X LiNbO3/SiO2/SiC multilayered substrate, and this type of SAW device exhibits a prospect of commercial applications in the 5G wireless system.

Size reduction and performance improvement of a microstrip Wilkinson power divider using a hybrid design technique

Abstract: In the design of a microstrip power divider, there are some important factors, including harmonic suppression, insertion loss, and size reduction, which affect the quality of the final product. Thus improving each of these factors contributes to a more efficient design. In this respect, a hybrid technique to reduce the size and improve the performance of a Wilkinson power divider (WPD) is introduced in this paper. The proposed method includes a typical series LC circuit, a miniaturizing inductor, and two transmission lines, which make an LC branch. Accordingly, two quarter-wavelength branches of the conventional WPD are replaced by two proposed LC branches. Not only does this modification lead to a 100% size reduction, an infinite number of harmonics suppression, and highfrequency selectivity theoretically, but it also results in a noticeable performance improvement practically compared to using quarter-wavelength branches in the conventional microstrip power dividers. The main important contributions of this technique are extreme size reduction and harmonic suppression for the implementation of a filtering power divider (FPD). Furthermore, by tuning the LC circuit, the arbitrary numbers of unwanted harmonics are blocked while the operating frequency, the stopband bandwidth, and the operating bandwidth are chosen optionally. The experimental result verifies the theoretical and simulated results of the proposed technique and demonstrates its potential for improving the performance and reducing the size of other similar microstrip components.

SIW Cavity-Fed Filtennas for 5G Millimeter-Wave Applications

Abstract: In this article, novel millimeter-wave (mmWave) filtennas (filtering antennas) are proposed to realize compact size and low insertion loss for 5G applications. It is achieved by employing eighth-mode substrate-integrated waveguide (EMSIW) cavities fully shielded by metallized vias and cover as resonators, which are named as fully shielded EMSIW (FSD-EMSIW) cavities. Interdigital coupling between cavities is introduced in order to obtain higher coupling strength for wideband operation. The proposed single-polarized antenna consists of a feeding stripline, two FSD-EMSIW cavities, and two stacked square patches, generating the four-order filtering antenna response. Furthermore, this design has been extended to realize a dual-polarized filtenna by employing double sets of feeding network. For demonstration, single-/dual-polarized filtenna prototypes were fabricated and measured, the measured results show that the 5G mmWave band (24.25–29.5 GHz) can be covered with average gains of 4.5 dBi. Good bandpass filtering response is also observed. Finally, to validate the proposed idea in array applications, a 16-element filtenna array is designed and measured with good performance.

Magnetic-free silicon nitride integrated optical isolator

Abstract: Integrated photonics enables signal synthesis, modulation and conversion using photonic integrated circuits (PICs). Many materials have been developed, among which silicon nitride (Si3N4) has emerged as a leading platform particularly for nonlinear photonics. Low-loss Si3N4 PICs have been widely used for frequency comb generation, narrow-linewidth lasers, microwave photonics and photonic computing networks. Yet, among all demonstrated functionalities for Si3N4 integrated photonics, optical non-reciprocal devices such as isolators and circulators have not been achieved. Conventionally, they are realized based on the Faraday effect of magneto-optic materials under an external magnetic field; however, it has been challenging to integrate magneto-optic materials that are not compatible with complementary metal–oxide–semiconductors and that require bulky external magnet. Here we demonstrate a magnetic-free optical isolator based on aluminium nitride (AlN) piezoelectric modulators monolithically integrated on low-loss Si3N4 PICs. The transmission reciprocity is broken by spatio-temporal modulation of a Si3N4 microring resonator with three AlN bulk acoustic wave resonators that are driven with a rotational phase. This design creates an effective rotating acoustic wave that allows indirect interband transition in only one direction among a pair of strongly coupled optical modes. A maximum of 10 dB isolation is achieved under 300 mW total radiofrequency power applied to three actuators, with minimum insertion loss of 0.1 dB. An isolation bandwidth of 700 MHz is obtained, determined by the optical resonance linewidth. The isolation remains constant over nearly 30 dB dynamic range of optical input power, showing excellent optical linearity. Our integrated, linear, magnetic-free, electrically driven optical isolator could be a key building block for integrated lasers and optical interfaces for superconducting circuits. An electrically driven, magnetic-free optical isolator is demonstrated. The device, based on aluminium nitride piezoelectric modulators and a silicon nitride microring resonator, may be useful for integrated lasers and other opto-electric systems.

1 Bit Dual-Linear Polarized Reconfigurable Transmitarray Antenna Using Asymmetric Dipole Elements With Parasitic Bypass Dipoles

Abstract: Reconfigurable transmitarray antennas with independent dual-linear polarization phase controlling capability are essential for wireless communications applications. This work proposes a novel 1 bit transmitarray element design at Ku -band, which adopts the receiver–transmitter structure with an active receiving dipole and a passive asymmetric transmitting dipole. The 1 bit phase shift is achieved by alternating two p-i-n diodes integrated on the active dipole to reverse its current direction. To mitigate the influence of p-i-n diodes and reduce the element insertion loss, a parasitic bypass dipole is added next to each dipole. Element simulations show that a low loss of only 1.0 dB is achieved. The dual-linear polarization capability is obtained by orthogonally interlacing two sets of proposed receiver–transmitter structures. A 100-element transmitarray prototype is designed, fabricated, and measured. The measured gain is 18.3 dB at 12.2 GHz, corresponding to an aperture efficiency of 22.6%. The 2-D beam-scanning capability for independent dual-linear polarization is experimentally verified and the scan angle covers ±50°. The measured maximum scan gain loss is 2.9 and 3.5 dB in the two principal planes, respectively.

High-precision digital terahertz phase manipulation within a multichannel field perturbation coding chip

Abstract: Direct phase modulation is one of the most urgent and difficult issues in the terahertz research area. Here, we propose a new method employing a two-dimensional electron gas (2DEG) perturbation microstructure unit coupled to a transmission line to realize high-precision digital terahertz phase manipulation. We induce local perturbation resonances to manipulate the phase of guided terahertz waves. By controlling the electronic transport characteristics of the 2DEG using an external voltage, the strength of the perturbation can be manipulated, which affects the phase of the guided waves. This external control permits electronic manipulation of the phase of terahertz waves with high precision, as high as 2−5° in the frequency range 0.26–0.27 THz, with an average phase error of only 0.36°, corresponding to a timing error of only 4 fs. Critically, the average insertion loss is as low as 6.14 dB at 0.265 THz, with a low amplitude fluctuation of 0.5 dB, so the device offers near-ideal phase-only modulation. A terahertz phase modulator based on the switchable perturbation resonance in two-dimensional electron gas is demonstrated. Phase manipulation with precision ranging from 2° to 5° is obtained at frequencies in the range from 0.26 to 0.27 THz.

A 200-225-GHz Manifold-Coupled Multiplexer Utilizing Metal Waveguides

Abstract: This article presents a 220-GHz four-channel, noncontiguous, and manifold-coupled waveguide multiplexer for future terahertz (THz) multichannel communication application. The multiplexer is composed of four Chebyshev bandpass filters based on metal waveguide technology. Through a unique design in which the tuning dimensional variables are reduced to 14 and a co-design of low-order electromagnetic (EM) distributed models and full-wave EM models, the design optimization is achieved with a good computational efficiency and design accuracy. The proposed multiplexer is fabricated by high-precision computer numerical control (CNC) milling technology, in which the fabrication errors are evaluated to be within ±3 μm. The measured results exhibit 1.7 dB of in-band insertion loss and better than 15 dB of average common-port return loss for each of the channel filter. The measured results are all in good agreement with the simulated ones, thereby validating the complete design procedure.

Thermally Actuated SOI RF MEMS-Based Fully Integrated Passive Reflective-Type Analog Phase Shifter for mmWave Applications

Abstract: This article presents a monolithically integrated reflective-type phase shifter (RTPS) utilizing silicon-on-insulator (SOI) radio frequency (RF) microelectromechanical systems (MEMS). The analog phase shifter employs a hybrid coupler and two identical reflective loads optimized to achieve a large phase shift range. The hybrid coupler is designed using two CPW-based couplers connected in a folded tandem configuration to achieve a compact size design. Various reflective load topologies are studied for optimum phase shift range and phase linearity over the bandwidth of interest. Measurement results demonstrate a continuous 120° tunable range from 26 to 30 GHz. The mmWave phase shifter exhibits a low insertion loss of 5.35 dB ± 0.6 dB at 28 GHz. The fabricated phase shifter has an overall device footprint of 4.0 $\text {mm}\times 2.6$ mm. All the components of the phase shifter module are co-fabricated in the 20 $\mu \text{m}$ device layer of a SOI wafer, which provides the flexibility of monolithic integration with other RF modules in phased array antenna systems. Contactless thermally actuated MEMS varactors are used in the reflective loads which do not suffer from the conventional contact-based reliability issues.

All-optical reversible single-photon isolation at room temperature

Abstract: Nonreciprocal devices operating at the single-photon level are fundamental elements for quantum technologies. Because magneto-optical nonreciprocal devices are incompatible for magnetic-sensitive or on-chip quantum information processing, all-optical nonreciprocal isolation is highly desired, but its realization at the quantum level is yet to be accomplished at room temperature. Here, we propose and experimentally demonstrate two regimes, using electromagnetically induced transparency (EIT) or a Raman transition, for all-optical isolation with warm atoms. We achieve an isolation of 22.52 ± 0.10 dB and an insertion loss of about 1.95 dB for a genuine single photon, with bandwidth up to hundreds of megahertz. The Raman regime realized in the same experimental setup enables us to achieve high isolation and low insertion loss for coherent optical fields with reversed isolation direction. These realizations of single-photon isolation and coherent light isolation at room temperature are promising for simpler reconfiguration of high-speed classical and quantum information processing.

Characterization of ABF/Glass/ABF Substrates for mmWave Applications

Abstract: Glass-based packaging presents unique opportunities for supporting 5G and beyond frequencies. In this work, we present the first broadband characterization results for the electrical properties of Ajinomoto build-up film (ABF) laminated on glass substrates. ABF/glass/ABF-based stack up has been characterized from 20 to 170 GHz. We also report the low-loss performance of ABF/glass/ABF transmission lines. The material stack up consists of a 100- $\mu \text{m}$ -thick EN-A1 glass core from Asahi Glass Company (AGC) with 15- $\mu \text{m}$ ABF GL102 laminated on both sides. Semiadditive process (SAP) has been used to metalize the stack up. A microstrip ring resonator (MRR) method has been used to extract the dielectric constant and loss tangent of the stack up. The dispersive model estimates the dielectric constant of the stack up to be ~4.72 for the entire frequency range with a variance of +0.1. The measured loss tangent values were 0.004, 0.009, and 0.012 at 23, 103, and 140 GHz, respectively. The electrical characterization results with a confidence interval of 95% have been reported. The average insertion loss for coplanar waveguide (CPW) lines in the frequency range was measured to be between 0.055 and 0.50 dB/mm. The average insertion loss for microstrip in the same frequency range was measured to be 0.12–0.62 dB/mm. Along with the good model to hardware correlation, the performance of the transmission lines has been compared with the insertion loss published for other substrate technologies.

Hybrid Absorptive-Diffusive Frequency Selective Radome

Abstract: This article proposes a hybrid absorptive–diffusive frequency-selective radome (AD-FSR) that has a broadband transmission window with wide absorption and diffusion bands located at two sidebands, respectively. The proposed hybrid AD-FSR consists of a resistive sheet and a bandpass frequency-selective surface (FSS) integrated with a coding metasurface separated by a certain distance. The wide absorption band is realized by the combined effect of the resistive sheet and the FSS integrated with a metasurface as a reflector in its lower stopband, while a broad passband is obtained when the electromagnetic (EM) wave penetrates through the resistive sheet in the passband of the FSS. In the upper side of the passband, the EM wave is diffused to reduce the radar cross section (RCS) of the surface by arranging the unit cell of the AD-FSR and its mirror based on the phase cancellation theory. Equivalent circuit and relevant theoretical formulas are utilized to better comprehend the physical mechanism of the proposed hybrid AD-FSR. A design example is then fabricated and measured, and the experimental results show that a broad transmission band is achieved from 6.92 to 13.12 GHz with a minimum insertion loss of 0.43 dB in a wide low reflectivity ( $\pmb {|S_{11} |} dB) band from 2.24 to 18 GHz.

Electrically driven optical isolation through phonon-mediated photonic Autler–Townes splitting

Abstract: Optical isolators today are exclusively built on magneto-optic principles but are not readily implemented within photonic integrated circuits. So far, no magnetless alternative1–22 has managed to simultaneously combine linearity (that is, no frequency shift), linear response (that is, input–output scaling), ultralow insertion loss and large directional contrast on-chip. Here we demonstrate an electrically driven optical isolator design that leverages the unbeatable transparency of a short, high-quality dielectric waveguide, with the strong attenuation from a critically coupled absorber. Our concept is implemented using a lithium niobate racetrack resonator in which phonon-mediated13 photonic Autler–Townes splitting10,16,23,24 breaks the chiral symmetry of the resonant modes. We demonstrate isolators at wavelengths one octave apart near 1,550 nm and 780 nm, fabricated from the same lithium-niobate-on-insulator wafer. Linear isolation is demonstrated with simultaneously 39 dB contrast and 10 dB bandwidth up to ~200 MHz. Non-magnetic optical isolators are demonstrated using phonon-mediated photonic Autler–Townes splitting. The on-chip lithium niobate devices simultaneously achieve ultralow insertion loss and high contrast.

Modeling and Analysis of Novel CSRRs-Loaded Dual-Band Bandpass SIW Filters

Abstract: Dual-band substrate integrated waveguide (SIW) bandpass filter (BPF) operating at 6 GHz and 12 GHz is presented. The two identical complementary split-ring resonators (CSRRs) make up the resonant unit. And the two CSRRs are strongly coupled. For the first time, two resonant units are horizontally etched on the upper metal of SIW. The equivalent circuit model of the novel dual-band SIW BPF is established and analyzed in detail. To realize the miniaturization design of the filter, a dual-band half-mode SIW BPF is proposed. The center frequencies of the passbands are located at 4.56 GHz and 9.36 GHz. The filter exhibits the characteristics of higher slope selectivity, lower insertion loss, wider 3 dB fractional bandwidths and compact size.

Design and Synthesis of Multi-Mode Bandpass Filter for Wireless Applications

Abstract: In this paper, a compact bandpass filter with improved band stop and band pass characteristics for wireless applications is built with four internal conductive poles in a single resonating cavity, which adds novel quad-resonating modes to the realization of band pass filter. This paper covers the design and testing of the S-band combline coaxial cavity filter which is beneficial in efficient filtering functions in wireless communication system design. The metallic cavity high Q coaxial resonators have the advantages of narrowband, low loss, better selectivity and high potential for power handling, as compared to microstrip filter in the application to determine the quality factor of motor oils. Furthermore, the tuning of coupling screws in the combline filter allows in frequency and bandwidth adjustments. An impedance bandwidth of 500 MHz (fractional bandwidth of 12.8%) has been achieved with an insertion loss of less than 2.5 dB and return loss of 18 dB at the resonant frequency. Four-pole resonating cavity filters have been developed with the center frequency of 4.5 GHz. Insert loss at 0 dB and estimated bandwidth at 850 MHz and a quality factor of 4.3 for the band pass frequencies between 4 and 8 GHz is seen in the simulated result.

Low loss and high performance interconnection between standard single-mode fiber and antiresonant hollow-core fiber.

Abstract: We demonstrate halving the record-low loss of interconnection between a nested antiresonant nodeless type hollow-core fiber (NANF) and standard single-mode fiber (SMF). The achieved interconnection loss of 0.15 dB is only 0.07 dB above the theoretically-expected minimum loss. We also optimized the interconnection in terms of unwanted cross-coupling into the higher-order modes of the NANF. We achieved cross-coupling as low as −35 dB into the LP $$_{11}$$ mode (the lowest-loss higher-order mode and thus the most important to eliminate). With the help of simulations, we show that the measured LP $$_{11}$$ mode coupling is most likely limited by the slightly imperfect symmetry of the manufactured NANF. The coupling cross-talk into the highly-lossy LP $$_{02}$$ mode ( $$>2000$$ dB/km in our fiber) was measured to be below −22 dB. Furthermore, we show experimentally that the anti-reflective coating applied to the interconnect interface reduces the insertion loss by 0.15 dB while simultaneously reducing the back-reflection below −40 dB over a 60 nm bandwidth. Finally, we also demonstrated an alternative mode-field adapter to adapt the mode-field size between SMF and NANF, based on thermally-expanded core fibers. This approach enabled us to achieve an interconnection loss of 0.21 dB and cross-coupling of −35 dB into the LP $$_{11}$$ mode.

Frequency Tunable Non-Reciprocal Bandpass Filter Using Time-Modulated Microstrip λ g /2 Resonators

Abstract: This brief presents a novel frequency reconfigurable microstrip non-reciprocal bandpass filter based on time-modulated microstrip $\lambda _{g}/2$ resonators. The modulation is achieved by loading both ends of the $\lambda _{g}/2$ transmission line resonators with time-modulated capacitors. The modulation voltage source is connected at the center of the resonator, where there is a natural voltage null, and a single inductor is used to further enhance the biasing isolation. The wideband nature of this isolation scheme enables the tuning of the devices over a wide frequency range. With more than 30-dB RF to modulation isolation, the proposed resonator structure also enables low insertion loss by eliminating RF signal leakage to the modulation ports. A 3-pole bandpass filter example is simulated and measured, showing a minimal insertion loss of 3.9dB, a 20-dB isolation bandwidth of 42MHz at 1.0GHz, and frequency tuning range of 885–1031MHz.

Optoelectromechanical phase shifter with low insertion loss and a 13π tuning range

Abstract: We present an on-chip optoectromechanical phase shifter with low insertion loss and low half-wave voltage using a silicon nitride platform. The device is based on a slot waveguide in which the electrostatic displacement of mechanical structures results in a change of the effective refractive index. We achieve insertion loss below 0.5 dB at a wavelength of 1550 nm in a Mach-Zehnder Interferometer with an extinction ratio of 31 dB. With a phase tuning length of 210 µm, we demonstrate a half-wave voltage of Vπ = 2.0 V and a 2π phase shift at V2π = 2.7 V. We measure phase shifts up to 13.3 π at 17 V. Our devices can be operated in the MHz range and allow for the generation of sub-µs pulses.

A Broadband and FSS-Based Transmitarray Antenna for 5G Millimeter-Wave Applications

Abstract: This letter describes the design of a broadband and FSS-based transmitarray (TA) antenna for 5G millimeter-wave applications. Two different elements are proposed to avoid the issues of the geometrical parameter resizing of the elements to obtain a 2 bit transmission phase of {−π, −π/2, 0, π/2} to achieve a TA antenna with wideband behaviors. Both of the two proposed elements show low insertion loss of below 1 dB from 24 to 38 GHz. Moreover, the two elements can achieve two sets of discrete transmission phases of {– π, 0} and {−π/2, π/2} without resizing their dimensions, respectively. A TA prototype based on the proposed two elements is designed and fabricated. The measured results agree very well with the simulated ones. The measured 1 and 3 dB gain bandwidth is 28.0–37.5 GHz (29.0%) and 25.1–39.1 GHz (43.7%), respectively. A peak aperture efficiency of 44.7% at 30 GHz is experimentally obtained with a realized gain of 26.1 dBi.

Polarization-Insensitive Cross-Polarization Converter

Abstract: A transmission-type cross-polarization converter is designed based on a frequency selective surface (FSS) and is investigated theoretically and experimentally. The FSS structure is built up with rotationally asymmetric fourfold supercell. The subcell of each supercell is a monopole-via-monopole (MVM) module, which consists of a receiving monopole, a transmitting monopole, and a quasi-wave-guiding structure (a through-via hole passing through the perforated shielding ground) to connect the monopole pair. In each supercell, the receiving and transmitting monopoles are orthogonally oriented to form a chiral geometry. The cross-polarization converter allows an incident wave linearly polarized at arbitrary azimuth to pass through and convert it into its cross-polarization state, while it operates as an FSS filter (without polarization state conversion) for the incidence of both circularly polarized waves. It exhibits a 3.0-dB transmission bandwidth ranging from 5.5 to 6.18 GHz (12%) with the peak insertion loss less than 0.16 dB at 5.8 GHz. The novelties of the reported cross-polarization converter lie in the insensitivity to the incident linear polarization azimuth and very low insertion loss within the investigated frequency band. To verify the proposed concept, a prototype is designed, fabricated, and measured, and good agreement between the simulated and experimental results is observed.

Multifunctional Switchable Filter Using Coupled-Line Structure

Abstract: A compact multifunctional switchable filter based on parallel-coupled lines with three different filtering functions is presented in this letter. By using p-i-n switches to connect or disconnect microstrip line and shorted coupled lines, three different modes, i.e., wideband bandpass filter (BPF), bandstop filter (BSF), and dual-band BPF, can be realized. For demonstration, the switchable filter prototype is designed and fabricated. For the wideband BPF mode, the measured 3-dB fractional bandwidth is about 53.1% (1.41–2.43 GHz) with the measured insertion loss of 0.9 dB. For the BSF mode, the measured 10-dB fractional bandwidth is about 30.2% (1.63–2.21 GHz) with in-band suppression level of over 15.5 dB. For the dual-band BPF mode, the measured 3-dB bandwidths of the two passbands are around 3.8% and 2.7%, respectively.

Fabrication-Tolerant CWDM (de)Multiplexer Based on Cascaded Mach–Zehnder Interferometers on Silicon-on-Insulator

Abstract: We demonstrate a cascaded Mach–Zehnder interferometer (MZI) based coarse wavelength division multiplexing (CWDM) (de)multiplexer on silicon-on-insulator with its spectral responses well aligned to the defined wavelength grids and are highly tolerant to the manufacturing linewidth variability. This was achieved by optimizing the waveguide widths and lengths of two arms in every MZI. As-realized CWDM (de)multiplexer exhibits a spectral shift of 0.487 nm, an insertion loss of less than 2.1 dB, and a channel crosstalk of lower than −20 dB, while reference devices fabricated on the same chips suffer from serious spectral shift of 15.4 nm to the shorter wavelength and higher insertion loss/channel crosstalk. The proposed MZI design concept can be applied to all MZI-based photonic devices and related photonic integrated circuits, so this work validates a promising design path towards practical WDM applications on silicon-on-insulator.

A compact coupler design using meandered line compact microstrip resonant cell (MLCMRC) and bended lines

Abstract: In this paper, a novel branch-line coupler using meandered line compact microstrip resonant cell (MLCMRC) and bended lines is proposed. The presented coupler works at 0.9 GHz, with good specifications. The measured values of S12 and S13 at 0.9 GHz are 3.2 dB and 3.3 dB, respectively, which show better than 0.3 dB insertion loss in the pass band. The measured value of S14 is better than 36 dB and S11 is better than 31 dB. The proposed design can eliminate 3rd and 5th harmonic with high suppression level (more than 40 dB) and reduce the size of the circuit more than 64% compared to the conventional branch-line coupler. The presented coupler has a very simple structure, which can be used in modern communication applications.

A Ku -Band CMOS Power Amplifier With Series-Shunt LC Notch Filter for Satellite Communications

Abstract: This article presents a $Ku$ -band power amplifier with a series-shunt $LC$ notch filter in 65-nm CMOS. The notch filter is integrated into the inter-stage matching network to attenuate the receiver-band noise, thereby reducing transmitter-to-receiver interference. A comprehensive analysis of the series and the shunt notch filters, as well as the position to apply the notch filter is discussed. Besides, a systematic method of optimizing passive devices in the notch filter is proposed to further improve network $Q$ and minimize the influence on the power amplifier. Fabricated in 65-nm CMOS technology, the power amplifier prototype delivers a measured gain of 21.9 dB with 3-dB bandwidth from 13.7 GHz to 16.7 GHz at the nominal state. At 14.2 GHz, it can offer a saturated output power of 14.5 dBm with peak power added efficiency of 24.1%. The notch frequency is adjustable from 10.3 to 11.9 GHz to offer the best attenuation at the receiver band. From 10 to 12 GHz, a maximal attenuation of 30 dB is achieved. The design occupies a core area of $0.35\times 0.85$ mm2.

Multifunctional Frequency Selective Rasorber With Dual Mode and Continuous Tunability

Abstract: This article introduces a multifunctional polarization insensitive frequency selective rasorber (MF-FSR) comprised of periodic metallic patterns printed on two dielectric substrates and separated by an air-spacer. The novelty of the proposed MF-FSR lies in its combined feature of mode switching and frequency tuning characteristics. This uniquely offers a real-time and multifunctional capability to switch from “rasorber mode (FSA-T)” into an “absorber with notch band (FSA-N)” mode where both modes support continuous tunability of their “transmission” or “notch” band. By controlling the reverse bias voltage of the embedded varactor, the transmission band in FSA-T mode can be tuned from 3.76 to 4.26 GHz with a very low insertion loss in the range of 0.62–0.95 dB. In complementary FSA-N mode, the notch band is also tunable from 4.17 to 4.71 GHz. Moreover, the same varactor set can control the tuning of transmission or the notch band depending upon MF-FSR’s basic state of operation which is further independently controllable by the p-i-n diode. Equivalent circuit models are also thoroughly examined. Finally, a prototype is fabricated and experimentally tested, showing a good agreement with the predicted results.

Low Insertion-Loss MMIC Bandpass Filter Using Lumped-Distributed Parameters for 5G Millimeter-Wave Application

Abstract: Millimeter-wave (mm-wave) monolithic-microwave-integrated-circuit (MMIC) bandpass filters (BPFs) usually feature high insertion loss (IL). To this concern, an analytical method for low-loss MMIC BPFs is presented by using lumped-distributed parameters in this article. To reduce the IL, the enhanced-quality-factor resonator and low-loss coupling topology are both investigated. First, the proposed resonator and filter are realized by combining quasi-lumped elements and distributed mutual coupling. Both compact size and multiple transmission zeroes are accordingly realized. Second, a low-loss coupling topology is further introduced for MMIC filter by using mixed electric and magnetic couplings. For theoretical analysis, the lossy equivalent circuit modeling for mm-wave MMIC BPF is investigated, as well as an analytical parameter extraction. Based on the circuit analysis, a fast synthesis of low-loss mm-wave MMIC filter is presented. For demonstration, two compact MMIC BPFs are designed by using the gallium arsenide (GaAs) process. Low IL of only 0.95 dB, sharp rejection skirt of passband, and wide stopband are simultaneously obtained. The features of the proposed MMIC BPFs indicate promising applications in the fifth-generation (5G) mm-wave systems.

Fiber optic hydrogen sensor based on a Fabry-Perot interferometer with a fiber Bragg grating and a nanofilm.

Abstract: Hydrogen is widely used in industrial production and clinical medicine, and as fuel. Hydrogen becomes explosive when the hydrogen-air mixture ranges from 4 to 76 vol%; thus, a rapid hydrogen concentration measurement is particularly important in practical applications. We present a novel fiber optic hydrogen sensor with fast response fabricated from a graphene-Au-Pd sandwich nanofilm and an ultrashort fiber Bragg grating. The response time is only 4.3 s at a 3.5 vol% hydrogen concentration. When the measured hydrogen concentration was increased from 0 to 4.5 vol%, the optical resonance dip in the sensor near 1550 nm shifted by 290 pm. In addition, the sensor has an insertion loss of only -2.22 dB, a spectral contrast of 10.8 dB, and a spectral finesse of 5. Such a flexible, fast-response sensor is expected to be used in the development of hydrogen sensors with low power consumption.