Radio Frequency Bandpass Research Articles

Tunable kilohertz microwave photonic bandpass filter based on backscattering in a microresonator.

A tunable microwave photonic bandpass filter (MPBPF) with a kilohertz bandwidth based on the backscattering mode of a silica microsphere resonator is proposed and experimentally demonstrated. In this work, an ultrahigh-quality-factor microsphere resonator is used to generate a radio frequency bandpass response with a bandwidth of 600 kHz. Meanwhile, scattering-induced coupling between the clockwise mode and the counterclockwise mode is introduced to reduce the number of resonance modes, and a single backscattering mode which has a high extinction ratio is obtained. Therefore, an MPBPF with a tuning range of 40 GHz and a rejection ratio of 16.9 dB is realized. This MPBPF possesses advantages such as ultranarrow bandwidth, large tuning range, and compactness, and shows great potential for microwave photonic applications.

Tracking extraterrestrial signals using the Super SID and Radio JOVE kits

A 20.1MHz dipole radio telescope was assembled, characterized and tested to detect extraterrestrial signals from planet Jupiter. Two element dipole arrays were built for the detection of 20.1MHz radio emission from the Jupiter-Io interaction, strong solar burst, the galactic background and the transit of the galactic center. Using the specifications and the layout, the dipole array was constructed. The block diagram, the schematic diagram built for NASA was used to solder together the radio frequency band pass filter, audio Preamplifier and audio amplifier to make the radio JOVE receiver. This was characterized, tested and tuned by setting the tuning knob to 20.0MHz. The dipole antenna was connected to the receiver and a variety of radio frequency emissions were detected. These signals were captured on a personal computer via the radio Jupiter Pro 3.8.3 and radio skypipe 2.6.5 software compatible with windows 7 OS and has python programme which converts data from the sod format to ASCII format to conveniently analyzed them. The data locally captured was correlated with other stations of the world. Specifically the analyzed chart of 14th July 2022 shows a lot of similarities with that captured by radio telescope UNIVERSUM shared with the global web repository.

A Comparative Study of Birdcage RF Coil Configurations for Ultra-High Field Magnetic Resonance Imaging.

Improvements in transmission and reception sensitivities of radiofrequency (RF) coils used in ultra-high field (UHF) magnetic resonance imaging (MRI) are needed to reduce specific absorption rates (SAR) and RF power deposition, albeit without applying high-power RF. Here, we propose a method to simultaneously improve transmission efficiency and reception sensitivity of a band-pass birdcage RF coil (BP-BC RF coil) by combining a multi-channel wireless RF element (MCWE) with a high permittivity material (HPM) in a 7.0 T MRI. Electromagnetic field (EM-field) simulations, performed using two types of phantoms, viz., a cylindrical phantom filled with oil and a human head model, were used to compare the effects of MCWE and HPM on BP-BC RF coils. EM-fields were calculated using the finite difference time-domain (FDTD) method and analyzed using Matlab software. Next, to improve RF transmission efficiency, we compared two HPM structures, namely, a hollow cylinder shape HPM (hcHPM) and segmented cylinder shape HPM (scHPM). The scHPM and MCWE model comprised 16 elements (16-rad BP-BC RF coil) and this coil configuration demonstrated superior RF transmission efficiency and reception sensitivity along with an acceptable SAR. We expect wider clinical application of this combination in 7.0 T MRIs, which were recently approved by the United States Food and Drug Administration.

Impact of multi-finger MOSFET geometry on the electrical performance of RF circuits

The increasing demand of low-cost, low-power and high-efficiency integrated systems is making more complex to design radio frequency (RF) analog circuits. Using multi-finger (MF) Metal-Oxide-Semiconductor (MOS) Field Effect Transistors (MOSFETs) is an attractive technique to optimize the circuit performances. It reduces the silicon area, the gate resistance and parasitic capacitances compared to the single finger MOSFET, which mainly impact the high frequency and noise performances. However, selecting the optimal number of fingers remains a challenging issue. This paper investigates the number of fingers (nf) influence on the transistor parameters and assesses its effect on several key functions in RF transceivers. The study focuses specially on the obtained performances of civil RF circuits, implemented in 130 nm CMOS technology, as a function of nf. First, design of a differential RF bandpass filter (BPF) is presented. The results show that using multi-finger MOSFETs leads to reductions in chip area by 66.5%, in power consumption by 15% and in noise figure by 43% with an improvement in linearity and frequency range compared to the conventional approach. Then, an inductorless LC-Voltage Controlled Oscillator (VCO) and a Low Noise Amplifier (LNA) operating around 2.4 GHz have been designed using three different configurations depending on nf. Obtained results display an improvement in the area, power gain, frequency and noise performances by applying the multi-finger optimization, and show that keep increasing nf can degrade the stability, linearity and power consumption. The proposed circuits are also tested through Monte Carlo simulations confirming their robustness to process and mismatch variations. Detailed analytical comparison between the different proposed circuits and configurations of nf proves that the MF technique is reliable when nf is inferior to 5.

RF Filter Synthesis Based on Passively Coupled N-Path Resonators

${N}$ -path circuits, consisting of an array of switched capacitors driven with non-overlapping clocks, have been used to create radio frequency bandpass and band-stop filters. This paper covers a synthesizing methodology of RF bandpass filters (BPFs) that uses multiple passively coupled ${N}$ -path resonators to realize a more selective transfer function with transmission zeros. Design details and measurement results of a proof-of-concept filter prototype with a 0.8–1.1-GHz tunable bandpass frequency realized in a 65-nm CMOS technology are presented.

On-Chip Brillouin Filtering of RF and Optical Signals

High-resolution signal processing will be a key aspect in current and future communication networks in crowded spectral environments. Signal processing based on the nonlinear optical process known as stimulated Brillouin scattering (SBS) are applicable in high-performance analog signal filtering for radio frequency (RF) communications and in coherent optical communication systems for carrier amplification. To meet the requirements of small size, low weight, and low power, the development of chip-based devices is critical. In this paper, we present an overview of on-chip SBS demonstrations of RF bandpass and bandstop filter functionalities with large frequency tuning and reconfigurability from tens of MHz to almost 0.5 GHz, applicable in RF communications. We also present our recent results on chip-based SBS filtering for optical communications. While traditionally SBS has been deemed to be incompatible with phase-sensitive communications, these latest results highlight the viability of SBS-enhanced high-capacity digital communication networks. We finally discuss the limitations of SBS filtering and also present some strategies to overcome them.

A Photonically Enabled Compact 0.5–28.5 GHz RF Scanning Receiver

An innovative and effective photonics-based radio frequency (RF) spectrum scanner is presented and demonstrated, enabling the detection in the 0.5–28.5 GHz range. The proposed receiver scans the whole frequency range at discrete steps, down-converting at baseband single portions of the detected spectrum, where they can be precisely acquired, without using RF bandpass filters nor optical filters. The wideband scansion is achieved by simply tuning an optical carrier only, avoiding the use of an RF synthesizer or of multiple parallel local oscillators. In more detail, the optical carrier is modulated by the detected RF signal through an electro-optical modulator, and photomixed with an optical local oscillator to down-convert the modulation sideband to baseband. The optical carrier also feeds an optical frequency comb generator—driven by a fixed RF oscillator at 1 GHz—whose output injects the local oscillator. This way, the optical carrier and oscillator are phase locked and can be tuned at steps of 1 GHz. The developed demonstrator achieves an input range up to 28.5 GHz, and a simulative analysis suggests the capability of exceeding the 0.5–40 GHz range employing commercially available devices. Moreover, it shows a linear dynamic range of 160 dB/Hz and a spuriousfree dynamic range of 109 dB/Hz2/3 , aligned with the state-of-the-art broadband RF receivers. The proposed solution appears to fulfill the performance requirements of the demanding electronic support measures applications, with the potentials for largely reducing the receiver size.

Arrays of suspended silicon nanowires defined by ion beam implantation: mechanical coupling and combination with CMOS technology

We present the fabrication, operation, and CMOS integration of arrays of suspended silicon nanowires (SiNWs). The functional structures are obtained by a top–down fabrication approach consisting in a resistless process based on focused ion beam irradiation, causing local gallium implantation and silicon amorphization, plus selective silicon etching by tetramethylammonium hydroxide, and a thermal annealing process in a boron rich atmosphere. The last step enables the electrical functionality of the irradiated material. Doubly clamped silicon beams are fabricated by this method. The electrical readout of their mechanical response can be addressed by a frequency down-mixing detection technique thanks to an enhanced piezoresistive transduction mechanism. Three specific aspects are discussed: (i) the engineering of mechanically coupled SiNWs, by making use of the nanometer scale overhang that it is inherently-generated with this fabrication process, (ii) the statistical distribution of patterned lateral dimensions when fabricating large arrays of identical devices, and (iii) the compatibility of the patterning methodology with CMOS circuits. Our results suggest that the application of this method to the integration of large arrays of suspended SiNWs with CMOS circuitry is interesting in view of applications such as advanced radio frequency band pass filters and ultra-high-sensitivity mass sensors.

Tunable Low-Jitter Low-Drift Spurious-Free Transposed-Frequency Optoelectronic Oscillator

We propose and theoretically and experimentally demonstrate a novel tunable spurious-free single-loop optoelectronic oscillator (OEO) with low drift and low-phase noise. In the proposed transposed-frequency OEO (TF-OEO), a nonreciprocal bias unit and an optical phase modulator in a fiber Sagnac interferometer function jointly as an intrinsically drift-free intensity modulator, which improves the long-term drift. Besides, a transposed-frequency low-noise filtered amplifier is used which replaces the conventional radio frequency (RF) bandpass filter (BPF) and RF amplifier with an intermediate frequency (IF) BPF, an ultralow phase noise IF amplifier, and a tunable local oscillator, to attain frequency tuning and single-frequency selection with ultralow phase noise at the same time. The quality of the generated microwave signals is theoretically investigated and verified by experiments. Preliminary phase noise, frequency stability, spurious noise levels, and frequency tunability of the photonically generated microwave signal are also investigated. A microwave signal with a frequency tunable range of 15 MHz around 10.833 GHz is generated with no spurs. The generated microwave oscillation has a single-sideband phase noise of −120 dBc/Hz at 10 kHz offset from 10.833 GHz carrier, with 36 fs RMS timing jitter integrated from 1 kHz to 10 MHz. Long-term frequency stability measurements show ±0.05 ppm maximum fractional frequency deviation over 60 h, which is mainly limited by drift of the fiber delay line. The measured results show the long-term frequency stability (in terms of overlapping Allan deviation) within $8.7\times 10^{-9}$ at 1000 s averaging time.

A comparative study on the design and simulation of TFBAR and polyimide-TFBAR based RF bandpass filters

The present work focusses on the design and simulation of a thin film bulk acoustic resonator (TFBAR) and a polyimide based TFBAR (PI-TFBAR) and compares the radio frequency (RF) bandpass filter response designed from these resonators. The Polyimide layer in the PI-TFBAR acts as an acoustic wave reflector along with providing mechanical strength to the device. The designed third order bandpass filter has a ladder topology. The insertion loss of the TFBAR filter is 1.69 dB and the return loss is 39.60 dB whereas the insertion loss and return loss are 1.71 and 23.7 dB respectively for the PI-TFBAR filter. The bandwidth of the TFBAR filter is 68.0 MHz and for PI-TFBAR it is 25 MHz. The proposed filter designs, with further optimization, may have application in the 2.6 GHz band, which has been identified by the International Telecommunication Union as a global band for International Mobile Telecommunications and is one of the core bands of LTE-Advanced technology.

An Enhanced Design of Multi-Band RF Band Pass Filter Based on Tunable High-Q Active Inductor for Nano-Satellite Applications

This paper describes the design of a novel cascode-grounded tunable active inductor and its application in an active band-pass filter (BPF) suitable for multi-band radio frequency (RF) front-end circuits. The proposed active inductor circuit uses feedback resistance to improve the equivalent inductance and the quality factor. The novelty of this work lies on the use of a few number of multi-finger transistors, which allows reducing strongly the power consumption and the silicon area. In other words, we demonstrate that the use of variable P-type Metal-Oxide-Semiconductor (PMOS) resistor and controllable current source have a good potential for wide tuning in terms of inductance value, quality factor and frequency operation. The RF BPF is realized using the proposed active inductor with suitable input and output buffer stages. The tuning of the center frequency for multi-band operation is achieved through control voltages. The designed active inductor and RF BPF have been implemented in a standard 0.13[Formula: see text][Formula: see text]m Complementary Metal Oxide Semiconductor (CMOS) technology. The simulation results are compared between schematic and post-layout design for inductance value, quality factor, transmission coefficient S21 and noise. This design yields encouraging results: the inductance value can be tuned from 10.94 to 44.17[Formula: see text]nH with an optimal quality factor around 2,581. In addition, the center frequency of the BPF can be tuned between 2 and 4.84[Formula: see text]GHz with an average insertion loss of [Formula: see text][Formula: see text]dB. Throughout this range, the noise figure is between 10.49 and 9.22[Formula: see text]dB with an input referred 1[Formula: see text]dB compression point of [Formula: see text][Formula: see text]dBm and IIP3 of 7.36[Formula: see text]dBm. The filter occupies 25.43[Formula: see text][Formula: see text]m of active area without pads and consumes between 2.38 and 2.84[Formula: see text]mW from a 1[Formula: see text]V supplying voltage.

Agile High-Q RF Photonic Zooming Filter

We report on the development of an agile radio frequency (RF) photonic receiver front-end based on a tunable single pole band-pass RF photonic filter with reconfigurable pass band. The filter center frequency is tunable from 30 MHz to 3 GHz (VHF-UHF frequency band) in a microsecond time interval, and its bandwidth is adjustable from 100 kHz to 100 MHz in less than 10 $\mu \text{s}$ time interval. The filter out-of-band rejection ratio exceeds 35 dB. The filter features 23 dB frequency independent insertion loss and −140 dBm/Hz noise floor with respect to input, as well as 110 dB $\cdot $ , Hz $^{2/3}$ spurious free dynamic range measured at 100 MHz filter bandwidth. The use of photonics technology allows adjusting the center frequency of the filter to any frequency within 30 MHz–100 GHz range without performance degradation.

Tunable optoelectronic oscillator with an embedded delay-line oscillator for fine steps

Tunable optoelectronic oscillator (OEO) with an embedded delay-line oscillator (EDO) for fine steps is presented. A delay-line oscillator consisting of an amplifier, phase shifter, and electrical delay line is embedded in the general single loop OEO. The oscillation frequency is controlled by the EDO loop phase, which is adjusted by the phase shifter. Without any narrow radio frequency bandpass filter, about 340 MHz tunable range with a fine step of ∼100 kHz is realized by directly tuning the direct current voltage of the phase shifter for 8 GHz oscillation. We also experimentally demonstrate κ-band tunable microwave signal generation within 22.18 to 23.32 GHz. The tunable accuracy and tunable range have a better performance compared to other OEO schemes with a fine frequency tunable step. The phase noise of the generated 22.25 GHz microwave signal is −108.7 dBc∕Hz at 10 kHz offset. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI: 10.1117/1.OE.55.3.031117)

Experimental Measurement of Fiber-Wireless Transmission via Multimode-Locked Solitons From a Ring Laser EDF Cavity

This paper describes a demonstration of soliton transmission over fiber-wireless (Fi-Wi) networks using mode-locked stable solitons over a 50-km-long fiber and a short-distance wireless link. Ultrashort optical pulse sources in the 1.5- $\mu\hbox{m} $ region are seen as increasingly important for achieving ultrahigh-speed optical transmission and signal processing at optical nodes. Mode-locked solitons were generated by a simple ring laser cavity incorporating a very thin layer of carbon nanotube (CNT), together with an erbium-doped fiber (EDF) laser used as an active bulk gain medium. Experimental measurements involved the transmission of the generated mode-locked soliton over a 50-km-long single-mode fiber (SMF), and a radio-frequency (RF) spectrum subsequently generated was a result of beating frequency of wavelengths launched into the photodetector at the other end of the SMF. This RF spectrum array was in the range of WiFi frequencies. System performance was evaluated by first selecting one of the RF carriers centered at 2.5 GHz via an RF bandpass filter and subsequently using this carrier to transmit quadrature phase-shift keying (QPSK) and 16-quadrature amplitude modulation (16-QAM) data signals. The described optical circuit, containing an EDF laser, a CNT, an SMF, and a wireless link, was shown to achieve ultrastable transmission of mode-locked soliton over a long-distance Fi-Wi network.

Arbitrary frequency tunable radio frequency bandpass filter based on nano-patterned Permalloy coplanar waveguide (invited)

A well designed coplanar waveguide (CPW) based center frequency tunable bandpass filter (BPF) at 4 GHz enabled with patterned Permalloy (Py) thin film has been implemented. The operating frequency of BPF is tunable with only DC current without the use of any external magnetic field. Electromagnetic bandgap resonators structure is adopted in the BPF and thus external DC current can be applied between the input and output of the filter for tuning of Py permeability. Special configurations of resonators with multiple narrow parallel sections have been considered for larger inductance tenability; the tunability of CPW transmission lines of different widths with patterned Py thin film on the top of the signal lines is compared and measured. Py thin film patterned as bars is deposited on the top of the multiple narrow parallel sections of the designed filter. No extra area is required for the designed filter configuration. Filter is measured and results show that its center frequency could be tuned from 4 GHz to 4.02 GHz when the DC current is applied from 0 mA to 400 mA.

Multirate Charge-Domain Filter Design for RF-Sampling Multi-Standard Receiver

This paper proposes a reconfigurable decimator architecture for a multi-standard receiver front-end. This architecture is based on direct radio-frequency bandpass sampling and analog discrete-time multirate signal processing. The overall front-end consists of a low-noise amplifier followed by a tunable charge-domain sampler, a reconfigurable decimator, and an analog-to-digital converter. The proposed decimator is constructed as a cascade of four switched-capacitor filtering stages. The frequency responses and the decimation factors of these stages are digitally controllable thus enabling high reconfigurability. The advantages of the proposed design are a high image rejection, a low overall implementation complexity, and high flexibility. The feasibility of the design is evaluated by computer simulations.

Inkjet printing RF bandpass filters on liquid crystal polymer substrates

This study investigates inkjet-printed radio frequency bandpass filters on liquid crystal polymer (LCP) substrates. Silver nanoparticle colloidal solution was used as a printing ink. A plasma polymerization technique was used to improve the LCP surface by optimizing the printing contact angle. Silver lines were then inkjet printed on the LCP substrate and cured in an oven to remove excess solvent and material impurities. The lines were printed with varied numbers of passes to study the changes in surface roughness and line width. The silver-film conductivity of the conductive ink was approximately 4×106Siemens/m. The third-order dual-behavior resonators bandpass filter was simulated using software and printed with an inkjet printing system. The minimal insertion loss and maximal return loss were −2.18 and −27.8dB at 5.4GHz, respectively. This study describes the optimization of the inkjet printing process and discusses the surface treatment study of the inkjet-printed seed layer and process integration is presented in detail.

Design of electronically switchable single‐to‐balanced bandpass low‐noise amplifier

In this work, the design of novel electronically switchable single-to-balanced bandpass low-noise amplifier (LNA) is proposed so as to improve the level of integration for radio frequency (RF) front-end design. By realising the input matching circuit with an electronically switchable bandpass filter and the output matching circuit as a bandpass balun, the LNA can also exhibit the functions of RF switch, bandpass filter and balun simultaneously. In this way, more compact circuit size and less mismatch loss can then be obtained in RF front-end design. To demonstrate the performance and effectiveness of the proposed design method, a 2-GHz electronically switchable single-to-balanced bandpass LNA is implemented on printed circuit board using packaged E-pHEMT transistor.

Radio‐frequency amplifier with tunable high‐Q RF bandpass filtering for SAW‐less wireless receivers

An inductor-less on-chip radio frequency bandpass filtering (RF-BPF) technique with tunable centre frequency is proposed to replace the bulky and expensive external SAW filter. The centre frequency of the BPF not only tracks the local oscillation (LO) frequency (f LO ), but also can be shifted from f LO to a controllable offset for low-IF applications. The RF-BPF has been embedded into a single-ended-input differential-output radio frequency amplifier (RFA) and implemented in 65nm CMOS. The RFA draws 3.5 mA DC current from a 2.5 V power supply. Measurement results show that the BPF achieves 16 dB attenuation at 150 MHz offset from the 1.5 GHz centre frequency, and 7 MHz tunable range without changing the LO frequency.

A SINGLE-BALANCED QUADRUPLE SUBHARMONICAL MIXER WITH A COMPACT IF EXTRACTION

A novel 21{35GHz single-balanced quadruple subhar- monic monolithic passive mixer is fabricated using the 0:15m GaAs pHEMT process. This mixer consists of a local oscillation (LO) spiral balun and a radio frequency (RF) band pass fllter which has an inter- mediate frequency (IF) extracted feature utilizing a pair of anti-parallel Schottky barrier diode to achieve quadruple subharmonic mixing mech- anism. The RF band pass fllter formed with an interdigital coupler and a low-pass network is used to reduce the chip dimension while oper- ating at a low frequency band and to improve the isolation between the RF and IF ports with a broadband operation. From the measured results, the mixer exhibits 11.3{15.1dB conversion loss, 28.8dB-high RF-to-IF isolation, 40dB-high LO-to-RF isolation, 60dB-high 3LO- to-RF isolation over a 21{35GHz RF bandwidth, and an input 1dB compression power of 4dBm. The compact IF extraction circuit sup- ports an IF frequency ranging from DC to 3.1GHz. The core chip size is only 0:67 £ 0:75mm 2 .