RF Bandpass Filter Research Articles

GHz repetition rate tunable optical pulses generation using a SBS-based coupled optoelectronic oscillator

An optical pulse generator with a tunable repetition rate of GHz is proposed employing a coupled optoelectronic oscillator (COEO). The tunability is achieved with an equivalent tunable RF bandpass filter which is realized through phase modulation and stimulated Brillouin scattering (SBS) in a high nonlinear fiber. An injected seed laser is applied to stabilize the central wavelength of the mode-locked loop. The repetition rate of the generated optical pulses is the frequency difference between the Stokes wave and the seed laser. It is adjusted by changing the wavelength of the pump laser for SBS effect. In the experiments, optical pulse trains with a repetition rate of 7.3 GHz–9.3 GHz are generated, and RF oscillating signals at the corresponding frequency are simultaneously produced. The side-mode suppression ratios (SMSRs) of the generated RF signals are all higher than 50 dB, and the phase noise is lower than −80dBc/Hz @10-kHz offset frequency. The tunable range of the optical pulse rate is limited by the bandwidth of the used RF phase shifter in the oscillating loop.

Automatic Modulation Recognition Based on Deep-Learning Features Fusion of Signal and Constellation Diagram

In signal communication based on a non-cooperative communication system, the receiver is an unlicensed third-party communication terminal, and the modulation parameters of the transmitter signal cannot be predicted in advance. After the RF signal passes through the RF band-pass filter, low noise amplifier, and image rejection filter, the intermediate frequency signal is obtained by down-conversion, and then the IQ signal is obtained in the baseband by using the intermediate frequency band-pass filter and down-conversion. In this process, noise and signal frequency offset are inevitably introduced. As the basis of subsequent analysis and interpretation, modulation recognition has important research value in this environment. The introduction of deep learning also brings new feature mining tools. Based on this, this paper proposes a signal modulation recognition method based on multi-feature fusion and constructs a deep learning network with a double-branch structure to extract the features of IQ signal and multi-channel constellation, respectively. It is found that through the complementary characteristics of different forms of signals, a more complete signal feature representation can be constructed. At the same time, it can better alleviate the influence of noise and frequency offset on recognition performance, and effectively improve the classification accuracy of modulation recognition.

High Rejection and Frequency Agile Optical Filtering of RF Signals Using a Rare Earth Ion-Doped Crystal

While photonics is broadly considered as a leading solution for analog RF processing, photonic RF filters often show a limited out-of-band rejection. In this work we demonstrate a high rejection and high steepness photonic RF bandpass filter based on spectral hole burning in a rare earth ion-doped crystal. The filter is obtained by programming a frequency-selective absorption grating in the crystal. With an experimental and theoretical study we identify the optimal parameters for this filter. We achieve a remarkable rejection of 60 dB and a rejection of 45 dB at 50 MHz from the edge of the filter, compliant with most demanding applications.

A 1–5 GHz 22 mW receiver frontend with active‐feedback baseband and voltage‐commutating mixers in 65 nm CMOS

A CMOS baseband-active-feedback receiver frontend with passive voltage-commutating mixers is proposed. The active feedback baseband enables in-band signal amplification and out-of-band blocker interference suppression by constructing the RF bandpass filter and BB lowpass filter, simultaneously. The voltage-commutating mixers embedded in current mirrors significantly reduce the power requirement for the LO generator. The stacked n/pMOS structure is commonly adopted to further improve power efficiency. The receiver frontend is designed in a standard 65 nm CMOS process. Simulation results display an NF of 3.4 dB and a maximum gain of 32 dB from 1 to 5 GHz LO frequency range. The obtained in-band and out-of-band IIP3 are −12 dBm and 9 dBm, respectively. The receiver frontend core only consumes 22 mW at 1 GHz LO frequency and occupies the area of 645 × 543 μm2, which is suitable for the low-power application of handheld terminals.

Design of broadband RF transceiver front-end using highly selective diplexer and high Q-factor hybrid resonator bandpass filters

In this paper, a development of low cost, miniature, highly integration broadband RF transceiver front-end using the high selectivity hybrid resonator RF bandpass filters, and diplexer integrated with shielding case is presented. The proposed RF transceiver frontend operates at the 2.7 GHz for transmitting and 2.4 GHz for receiving, supporting a channel bandwidth of 100 MHz with frequency division duplexing mode. The designed low loss, high selectivity hybrid resonator bandpass filters are utilized to channel selection and reject the interference signal. The high isolation diplexer is employed to separate the Tx and Rx signals and reject the interferences from other systems to the RF receiver as well as filter out the harmonics generated by the RF transmitter. The measured performance of the proposed RF transceiver front-end module is superior to the requirements as well as can support high spectrum efficiency and high data rate communications with low error vector magnitude.

A Cavity-Backed Patch Antenna With Distributed Multi-Port Feeding, Enabling Efficient Integration With Doherty Power Amplifier and Band-Pass Filter

A joint design approach for cointegrated antenna and power amplifier (PA), employing a high-efficiency Doherty PA (DPA) architecture and including a bandpass RF filter, is proposed. This design is realized through the optimally distributed and balanced multiport feeding of the cavity-backed patch antenna element that provides the desired (unique) loading conditions for the main and auxiliary PA branches and tailored power combining. A novelty and advantage of this feeding solution is that each pair of feeding points forms a virtual common feeding center of the radiating element; as a result, the radiation pattern remains power invariant when the port excitations change. A joint optimization of the integrated antenna-DPA transmitter is carried out to enhance the overall performance and maximize the bandwidth. This optimization is demonstrated through an example design for the sub-6 GHz telecommunication applications that target high power efficiency (>50%) at the 6 dB backed-off power levels and require RF-filtering in a compact integrated design. The latter challenge leads to a nonconventional implementation, which generally does not require the filter to be inserted between the antenna and the final output stage of the PA, and can be embedded in the topology with complex-valued source/load impedance values. The results of numerical studies are supported by measurements obtained with the antenna-DPA-filter prototype system.

Tunable bandpass filter using double resistive feedback floating active inductor for 5 GHz wireless LAN Applications

It has been a challenging task for the designers to implement on-chip bandpass filter at high frequency with better performance. In this paper, a tunable RF bandpass filter using double resistive feedback floating active inductor (AI) based on gyrator-C topology has been proposed using 40 nm CMOS technology for 5 GHz WLAN applications. Small signal analytical modelling determines the design parameters affecting the performance of proposed floating AI, which ascertains that the double resistive feedback increases the quality factor as well as inductance value. The proposed AI attains a maximum quality factor of 964, high inductance ranging from 420 to 2080 nH and wide inductive bandwidth varying from 550 MHz to 7.85 GHz. Total current drawn by the AI is 2.66 mA at 1.2 V power supply and occupies an area of 17.1 × 9.1 µm2. In order to validate the performance of AI, a second-order tunable bandpass filter with frequency range 5.15–5.35 GHz has been implemented, with a small fractional 3-dB bandwidth, quality factor and 1-dB compression point of 15 MHz, 346 and − 2.8 dBm respectively. The Bandpass filter attains the figure of merit of 92.16 dB and dynamic range of 150 dB-Hz.

Designing RF and Microwave Band Pass Filters Using Coupled Resonators

ABSTRACT In this article, the authors have made an attempt to capture the recent developments taking place in the design of band pass filters (BPF) as a tutorial article. The article deals with the design of a reasonably good physical BPF from user specifications, followed by space mapping technique to translate the initial filter into the desired final filter. The authors believe that this tutorial article will benefit both students and engineers alike. A basic understanding of BPF and working knowledge of electromagnetic tool are sufficient pre-requisites to dive into this journey.

Design of Microwave Photonic Subsystems Using Brillouin Scattering

With the rapid development of microwave photonic functionalities to support 5G and defence systems, there has been an increased interest in employing stimulated Brillouin scattering (SBS)-based functionalities to perform tasks that are currently difficult to achieve with conventional electronic devices. Several advances have been made using on-chip SBS to demonstrate RF frequency phase shifters, bandpass and bandstop filters, measurement systems, and delay lines. In this article, we provide an overview of some of these developments made possible by strong on-chip SBS gain. We also provide the reader with design guidelines on the selection of the appropriate waveguide geometry, subsystem design, and analog photonic link configurations to aid them in the realisation of their requisite MWP subsystem. We also focus on some of the design trade-offs that need to be considered when using integrated SBS.

Frequency reconfigurable monopole antenna with harmonic suppression for IoT applications

This work proposes a new reconfigurable printed monopole antenna for IoT devices working with the promising wireless technology Wi-Fi 6. Based on effective resonant length value, the antenna has the ability to reconfigure its operating band between 2.4 GHz and 5 GHz ISM bands. Therefore, the designed antenna works as an RF band-pass filter which reduces receiver complexity and supports network scalability. One PIN diode with complete biasing circuit is integrated to the antenna radiator to obtain re-configurability. Furthermore, two stubs are added to the antenna structure in order to suppress harmonic component which appears near to the higher band (5 GHz) when antenna forced to work at the lower band (2.4 GHz). The design built over commercially available FR-4 substrate with a compact size of (33.5x16x1.6) mm 3 . CST software is used to simulate antenna performance in terms of flection coefficient, radiation pattern, efficiency, and gain.

An all-digital frequency tunable IR-UWB transmitter with an approximate 15th derivative Gaussian pulse generator

This work presents a new frequency-tunable, OOK–modulated, impulse-radio ultra-wideband (IR-UWB) transmitter, where approximate 15th derivative Gaussian pulses are produced by a monopulse-synthesis pulse generator. The center frequency of our output UWB pulses can be easily adjusted between 4 and 9 GHz by controlling delay time. Thus, the whole UWB frequency band from 3.1 to 10.6 GHz can be covered and utilized. Since the proposed monopulse-synthesis pulse generator already includes a pulse shaping function, RF bandpass filters are not required, thus realizing the extremely low complexity and small circuit area. The proposed IR-UWB transmitter has been implemented and fabricated in a standard 0.18 μm CMOS 1p6m process. The power supply voltage is 1.8 V and the targeted data rate is 31.25 Mbps. Chip measurement results show that the power spectrum density conforms to the FCC spectrum masks, and the peak-to-peak voltage of output UWB pulses is 56 mV. In addition, the core area of the chip is 0.02 mm2, the measured frequency tuning range is 3.1–10.6 GHz, and the measured energy dissipation is only 12.5 pJ/bit. Compared to the state-of-the-art designs in the literature, the chip area and tunable frequency range are improved by at least 33% and 53%, respectively.

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.

Implementation of RF Band-Pass Filter on UMTS Systems to Improve Quality of Service

A large number of cellular operators in an area causes high interference effects. One indicator is the problem with received total wideband power (RTWP) found in a universal mobile telecommunication system (UMTS). High RTWP is one of the causes of a decrease in the quality of service (QoS) in cellular communication networks. To solve this problem, an RF band-pass filter device can be implemented on a UMTS system, where RF band-pass filters have been designed and tested in previous studies. In this research, the RF band-pass filter was installed between the BTS node and bottom jumper. After implementing it, QoS measurements with the Huawei M2000 application and Drive Test were carried out. The QoS analysis included RTWP, Circuit-Switched access rate, Packet-Switched access rate, and Received Signal Code Power (RSCP) value. The results show that the RTWP value decreases, while the CS access rate, PS access rate, and RSCP value increase. These results indicate that QoS on the UMTS increases.

Symmetrical Quasi-Absorptive RF Bandpass Filters

A type of symmetrical RF bandpass filters (BPFs) with quasi-absorptive functionality are presented. They are composed of a bandpass section that is loaded at its input/output ports with nearly complementary resistively terminated bandstop sections. In this manner, the input-signal energy that is not transmitted by the bandpass section is dissipated by the loading resistors of the bandstop sections to attain the quasi-reflectionless behavior. The theoretical analysis of the first-order symmetrical quasi-absorptive BPF stage is detailed. In addition, synthesis examples of higher attenuation and sharper rejection designs based on in-series-cascade arrangements, higher order realizations, and cross-coupling techniques are illustrated. A coupling-matrix-level loss analysis of the devised symmetrical quasi-reflectionless BPF configuration for uniform and nonuniform quality-factor ( ${Q}$ ) distribution is also carried out. Furthermore, for experimental validation, 2.5-GHz microstrip BPF demonstrators consisting of an in-band linear-phase two-stage in-series-cascade circuit and a second-order prototype are manufactured and characterized.

Simple, Analytical Expressions of an Effect of Local Signal Imperfections on Four-Phase Passive-Mixer-Based Bandpass Filter

This paper describes simple, analytical expressions for a quadrature passive-mixer-based RF bandpass filter. We have analyzed the passive mixer clocked by the trapezoidal-shaped local (LO) signals with different rise and fall times. Obtained results show that the partially overlapping LO signals and/or large capacitance of low-noise amplifier load cause charge reduction of each baseband branch capacitance. This results in the filter characteristics degradation. To achieve good filter characteristics, short rise and fall time of the LO signal and/or appropriate mixer RF-node biasing is effective. Our analysis results agreed well with the data obtained from the Advanced Design System simulator.

Control of coexisting periodic oscillations in an optoelectronic oscillator

We investigate the dynamics of a modified optoelectronic oscillator (OEO) through theoretical and numerical analysis. The OEO under study is different from the conventional OEO in the sense that it contains a van der Pol oscillator (VDPO) in its feedback loop, in place of the RF band pass filter. Two coexisting limit cycle oscillations are identified, known as birhythmicity. Subsequently, a simple self-feedback scheme is introduced to control the birhythmic behavior of the oscillator. To the best of our knowledge, the control of birhythmicity in an intrinsic time-delayed oscillator has not been studied earlier.

Integrated ferroics for sensing, power, RF, and µ-wave electronics

Abstract

RF and microwave reconfigurable bandpass filter design using optimized active inductor circuit

In this article, a design methodology of an active bandpass filter (BPF) using tunable active inductor (TAI) achieving wide frequency contiguous tuning range (FTR) is presented. The tunable BPF is realized with a differential TAI (DTAI) employing two-reconfiguration mechanisms one for coarse-tuning using a controllable current source while the fine-tuning is performed through a variable feedback resistance. The center frequency tuning is performed through the variation of the DTAI control voltages. A cross-coupled pair based negative resistance technique is also applied to compensate the resistive losses of equivalent RLC resonator. The filter performances are significantly improved using several optimization techniques such as voltage scaling and multigate finger techniques. The proposed BPF is simulated using 0.13 μm CMOS technology. The filter achieves an insertion loss (IL) of 26.62-33.45 dB over the tuning range 1.16-3.27 GHz with a relative bandwidth of 1.3%-3.4%. The noise figure and input 1-dB compression point at 1.84 GHz are 14.93 dB and 2.72 dBm, respectively. The designed RF filter consumes an average power of 5 mW at 1 V supply voltage.

Enhanced-Selectivity High-Linearity Low-Noise Mixer-First Receiver With Complex Pole Pair Due to Capacitive Positive Feedback

A mixer-first receiver (RX) with enhanced selectivity and high dynamic range is proposed, targeting to remove surface acoustic-wave-filters in mobile phones and cover all frequency bands up to 6 GHz. Capacitive negative feedback across the baseband (BB) amplifier serves as a blocker bypassing path, while an extra capacitive positive feedback path offers further blocker rejection. This combination of feedback paths synthesizes a complex pole pair at the input of the BB amplifier, which is upconverted to the RF port to obtain steeper RF bandpass filter roll-off and reduced distortion. This paper explains the circuit principle and analyzes RX performance. A prototype chip fabricated in 45-nm partially depleted silicon on insulator (SOI) technology achieves high out-of-band linearity (input-referred third-order intercept point (IIP3) = 39 dBm and input-referred second-order intercept point (IIP2) = 88 dB) combined with sub-3-dB noise figure. Desensitization due to a 0-dBm blocker is only 2.2 dB at 1.4 GHz.

Reliable and $Q$ -Enhanced Floating Active Inductors and Their Application in RF Bandpass Filters

This paper presents three new floating active inductor (FAI)-based bandpass filter (BPF) topologies, namely, the nominal- $Q$ BPF (NQF), $Q$ -enhanced BPF-1 (QF1), and $Q$ -enhanced BPF-2 (QF2). The filters utilize voltage differencing transconductance amplifier (VDTA) as an active building block and are implemented in a 45-nm CMOS process. Negative resistance techniques are used to enhance the quality factor and an addition-based current reference technique reduces the sensitivity of filter’s design metrics to process, voltage, and temperature (PVT) variations. The performances of the filters are analyzed in the presence of parasitics and analytical expressions are derived. The proposed filters consume minimal power, possess a high $Q$ and good dynamic range, and are reliable despite being implemented in the nanoscale regime. The NQF/QF1/QF2 exhibits a center frequency of 4.36/3.63/3.02 GHz, quality factor of 17.84/54/46.2, the 3-dB bandwidth of 244.4/67.22/65.36 MHz, the dynamic range of 122.49/118.58/119.46 dB, and a 1-dB compression point of −3.06/−5.48/−5.45 dBm. The filter topologies consume 0.552/0.608/0.634 mW from ±1-V supply voltage. The above-mentioned parameters translate into a figure-of-merit FOM1(FOM2) of 125.07 dB-Hz/mW (80.59 dB)/120.74 dB-Hz/mW (81.33 dB)/121.44 dB-Hz/mW (79.81 dB) for NQF/QF1/QF2.