The Experts below are selected from a list of 78129 Experts worldwide ranked by ideXlab platform
Matteo Rinaldi - One of the best experts on this subject based on the ideXlab platform.
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radio frequency magnet free circulators based on spatiotemporal modulation of surface acoustic wave filters
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Giuseppe Michetti, Ahmed Kord, Dimitrios L Sounas, Andrea Alu, Michele Pirro, Zhicheng Xiao, Cristian Cassella, Matteo RinaldiAbstract:In this article, a new generation of magnet-free circulators with high performance is proposed. Circulators are crucial devices in modern communication systems due to their ability to enable full-duplexing and double the spectral efficiency directly in the physical layer of the radio-frequency (RF) front end. Traditionally, the Lorentz reciprocity is broken by applying the magnetic bias to ferrite materials; therefore, conventional circulators are bulky and expensive. In this article, this problem is addressed by replacing the magnetic bias with periodic spatiotemporal modulation. Compared to previous works, the proposed circulator is constructed using surface acoustic wave (SAW) filters instead of transmission lines (TLs), which reduces the modulation frequency by at least a factor of 20 and ensures ultra-low power consumption and high linearity. The miniaturized high quality ( ${Q}$ ) factor SAW filters also lead to a low-loss nonreciprocal band with strong isolation (IX) and broad bandwidth (BW) on a chip scale, therefore addressing such limitations in previous magnet-free demonstrations. Furthermore, compared to the conventional differential circuit configuration, a novel quad configuration is developed, which doubles the intermodulation-free BW.
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radio frequency magnet free circulators based on spatiotemporal modulation of surface acoustic wave filters
arXiv: Signal Processing, 2019Co-Authors: Giuseppe Michetti, Ahmed Kord, Dimitrios L Sounas, Andrea Alu, Michele Pirro, Zhicheng Xiao, Cristian Cassella, Matteo RinaldiAbstract:In this paper, a new generation of magnet-free circulators with high performance is proposed. Circulators are crucial devices in modern communication systems due to their ability to enable full-duplexing and double the spectral efficiency directly in the physical layer of the radio-frequency (RF) front-end. Traditionally, Lorentz reciprocity is broken by applying magnetic bias to ferrite materials, therefore conventional circulators are bulky and expensive. In this paper, this problem is addressed by replacing the magnetic bias with periodic spatiotemporal modulation. Compared to previous works, the proposed circulator is constructed using surface acoustic wave (SAW) filters instead of transmission lines (TL), which reduces the modulation frequency by at least a factor of 20 and ensures ultra-low power consumption and high linearity. The miniaturized high quality (Q) factor SAW filters also lead to a low-loss non-reciprocal band with strong isolation (IX) and broad bandwidth (BW) on a chip scale, therefore addressing such limitations in previous magnet-free demonstrations. Furthermore, compared to the conventional differential circuit configuration, a novel quad configuration is developed, which doubles the intermodulation-free bandwidth.
Andrea Alu - One of the best experts on this subject based on the ideXlab platform.
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ultra compact ultra wideband dc 1ghz cmos circulator based on quasi electrostatic wave propagation in commutated switched capacitor networks
Radio Frequency Integrated Circuits Symposium, 2020Co-Authors: Aravind Nagulu, Andrea Alu, Mykhailo Tymchenko, Harish KrishnaswamyAbstract:Recent research has revealed the possibility to achieve non-magnetic non-reciprocity using time-variance. However, prior CMOS-based circulators rely on the interference between non-reciprocal switched-capacitor/transmission-line gyrators and reciprocal transmission-line rings, which increases form factor and restricts frequency tunability and bandwidth. On the other hand, recent works on quasi-electrostatic wave propagation in switched-capacitor media have demonstrated a new regime in multipath switched-capacitor network operation that enables an ultra-broadband, ultra-compact reciprocal/non-reciprocal true-time-delay element. In this work, we apply synthetic rotation across this quasi-electrostatic medium to realize an ultra-broadband N-port circulator with ultra-compact form-factor. This new architecture is showcased in a wideband 3-port circulator implemented in a standard 65nm CMOS process. This circulator exhibits symmetric performance across all 3 ports and DC-1GHz operation for a modulation frequency of 500MHz. The measured transmission losses range between 3.1-4.3dB, matching is 18dB and NF is consistent with the insertion loss. This device occupies an area of 0.19mm2 ($\lambda _{center}^2/1.9 \times {10^6}$), representing about 100-1000× higher miniaturization compared to the prior art.
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radio frequency magnet free circulators based on spatiotemporal modulation of surface acoustic wave filters
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Giuseppe Michetti, Ahmed Kord, Dimitrios L Sounas, Andrea Alu, Michele Pirro, Zhicheng Xiao, Cristian Cassella, Matteo RinaldiAbstract:In this article, a new generation of magnet-free circulators with high performance is proposed. Circulators are crucial devices in modern communication systems due to their ability to enable full-duplexing and double the spectral efficiency directly in the physical layer of the radio-frequency (RF) front end. Traditionally, the Lorentz reciprocity is broken by applying the magnetic bias to ferrite materials; therefore, conventional circulators are bulky and expensive. In this article, this problem is addressed by replacing the magnetic bias with periodic spatiotemporal modulation. Compared to previous works, the proposed circulator is constructed using surface acoustic wave (SAW) filters instead of transmission lines (TLs), which reduces the modulation frequency by at least a factor of 20 and ensures ultra-low power consumption and high linearity. The miniaturized high quality ( ${Q}$ ) factor SAW filters also lead to a low-loss nonreciprocal band with strong isolation (IX) and broad bandwidth (BW) on a chip scale, therefore addressing such limitations in previous magnet-free demonstrations. Furthermore, compared to the conventional differential circuit configuration, a novel quad configuration is developed, which doubles the intermodulation-free BW.
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radio frequency magnet free circulators based on spatiotemporal modulation of surface acoustic wave filters
arXiv: Signal Processing, 2019Co-Authors: Giuseppe Michetti, Ahmed Kord, Dimitrios L Sounas, Andrea Alu, Michele Pirro, Zhicheng Xiao, Cristian Cassella, Matteo RinaldiAbstract:In this paper, a new generation of magnet-free circulators with high performance is proposed. Circulators are crucial devices in modern communication systems due to their ability to enable full-duplexing and double the spectral efficiency directly in the physical layer of the radio-frequency (RF) front-end. Traditionally, Lorentz reciprocity is broken by applying magnetic bias to ferrite materials, therefore conventional circulators are bulky and expensive. In this paper, this problem is addressed by replacing the magnetic bias with periodic spatiotemporal modulation. Compared to previous works, the proposed circulator is constructed using surface acoustic wave (SAW) filters instead of transmission lines (TL), which reduces the modulation frequency by at least a factor of 20 and ensures ultra-low power consumption and high linearity. The miniaturized high quality (Q) factor SAW filters also lead to a low-loss non-reciprocal band with strong isolation (IX) and broad bandwidth (BW) on a chip scale, therefore addressing such limitations in previous magnet-free demonstrations. Furthermore, compared to the conventional differential circuit configuration, a novel quad configuration is developed, which doubles the intermodulation-free bandwidth.
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fully integrated non magnetic 180nm soi circulator with 1w p1db 50dbm iip3 and high isolation across 1 85 vswr
Radio Frequency Integrated Circuits Symposium, 2018Co-Authors: Aravind Nagulu, Andrea Alu, Harish KrishnaswamyAbstract:There has been recent progress on CMOS non-magnetic circulators based on switch-based spatio-temporal conductivity modulation, but these initial demonstrations remain limited in transmitter power handling, linearity, and ability to combat antenna variations. This paper describes a non-magnetic circulator in 180nm SOI CMOS that uses no external components, and employs various linearity enhancement techniques such as device stacking, optimal switch biasing, and localized ESD design to achieve >1W TX-ANT PldB and >+50dBm TX-ANT IIP3 at 1GHz. A new loss-free and inductor-free antenna balancing approach enables high isolation for as high as 1.85 ANT VSWR and beyond. The circulator also exhibits low insertion losses of 2.1dB/2.9dB in the TX-ANT and ANT-RX paths, and ANT-RX NF of 3.1dB. These results represent a 10–100×enhancement in linearity/power handling over prior CMOS non-reciprocal circulators, and are shown to lower the power consumption of a communication link when compared with state-of-the-art electrical balance duplexers in scenarios where dynamic range is limited by P1dB, NF.
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optical circulation in a multimode optomechanical resonator
Nature Communications, 2018Co-Authors: Freek Ruesink, Andrea Alu, John P Mathew, Mohammadali Miri, Ewold VerhagenAbstract:Breaking the symmetry of electromagnetic wave propagation enables important technological functionality. In particular, circulators are nonreciprocal components that can route photons directionally in classical or quantum photonic circuits and offer prospects for fundamental research on electromagnetic transport. Developing highly efficient circulators thus presents an important challenge, especially to realise compact reconfigurable implementations that do not rely on magnetic fields to break reciprocity. We demonstrate optical circulation utilising radiation pressure interactions in an on-chip multimode optomechanical system. Mechanically mediated optical mode conversion in a silica microtoroid provides a synthetic gauge bias for light, enabling four-port circulation that exploits tailored interference between appropriate light paths. We identify two sideband conditions under which ideal circulation is approached. This allows to experimentally demonstrate ~10 dB isolation and <3 dB insertion loss in all relevant channels. We show the possibility of actively controlling the circulator properties, enabling ideal opportunities for reconfigurable integrated nanophotonic circuits.
Harish Krishnaswamy - One of the best experts on this subject based on the ideXlab platform.
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ultra compact ultra wideband dc 1ghz cmos circulator based on quasi electrostatic wave propagation in commutated switched capacitor networks
Radio Frequency Integrated Circuits Symposium, 2020Co-Authors: Aravind Nagulu, Andrea Alu, Mykhailo Tymchenko, Harish KrishnaswamyAbstract:Recent research has revealed the possibility to achieve non-magnetic non-reciprocity using time-variance. However, prior CMOS-based circulators rely on the interference between non-reciprocal switched-capacitor/transmission-line gyrators and reciprocal transmission-line rings, which increases form factor and restricts frequency tunability and bandwidth. On the other hand, recent works on quasi-electrostatic wave propagation in switched-capacitor media have demonstrated a new regime in multipath switched-capacitor network operation that enables an ultra-broadband, ultra-compact reciprocal/non-reciprocal true-time-delay element. In this work, we apply synthetic rotation across this quasi-electrostatic medium to realize an ultra-broadband N-port circulator with ultra-compact form-factor. This new architecture is showcased in a wideband 3-port circulator implemented in a standard 65nm CMOS process. This circulator exhibits symmetric performance across all 3 ports and DC-1GHz operation for a modulation frequency of 500MHz. The measured transmission losses range between 3.1-4.3dB, matching is 18dB and NF is consistent with the insertion loss. This device occupies an area of 0.19mm2 ($\lambda _{center}^2/1.9 \times {10^6}$), representing about 100-1000× higher miniaturization compared to the prior art.
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analysis and design of a full duplex two element mimo circulator receiver with high tx power handling exploiting mimo rf and shared delay baseband self interference cancellation
IEEE Journal of Solid-state Circuits, 2019Co-Authors: Mahmood Baraani Dastjerdi, Sanket Jain, Negar Reiskarimian, Arun Natarajan, Harish KrishnaswamyAbstract:In this article, we present how full-duplex (FD) operation can be integrated with multi-input multi-output (MIMO) operation using RF and baseband (BB) self-interference cancellation (SIC). MIMO operation increases the SIC requirements by a factor of $N^{2}$ , resulting in severe area, power consumption, and noise penalty. We present the detailed analysis, design, and implementation of RF/BB cancellers that address this challenge, as well as a bootstrapping technique to enhance the power handling of integrated circulator-receivers (circ.-RX). A 65-nm CMOS scalable two-element MIMO FD circ.-RX array with integrated $N$ -path-filter-based nonmagnetic circulators is described that: 1) exploits bootstrapping in the circulator $N$ -path filters to enhance Transmitter (TX) power handling by 8 dB and 2) features area- and power-efficient passive RF and active BB wideband MIMO cancellation with shared-delay elements to address the O( $N^{2}$ ) cancellation challenge. The prototype exhibits: 1) up to 35-/45-dB average SIC across 40-/20-MHz BW; 2) more than 42-/53-dB average crosstalk (CT)-SIC across 40-/20-MHz BW with <2.1-dB degradation in RX NF; and 3) overall TX power handling of +14 dBm enabled by clock bootstrapping.
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a single antenna full duplex radio using a non magnetic cmos circulator with in built isolation tuning
International Conference on Communications, 2019Co-Authors: Aravind Nagulu, Tingjun Chen, Gil Zussman, Harish KrishnaswamyAbstract:Wireless systems which can simultaneously transmit and receive (STAR) are gaining significant academic and commercial interest due to their wide range of applications such as full-duplex (FD) wireless communication and FMCW radar. FD radios, where the transmitter (TX) and the receiver (RX) operate simultaneously at the same frequency, can potentially double the data rate at the physical layer and can provide many other advantages in the higher layers. The antenna interface of an FD radio is typically built using a multi-antenna system, or a single antenna through a bulky magnetic circulator or a lossy reciprocal hybrid. However, recent advances in CMOS-integrated circulators through spatio-temporal conductivity modulation have shown promise and potential to replace traditional bulky magnetic circulators. However, unlike magnetic circulators, CMOS-integrated non-magnetic circulators will introduce some nonlinear distortion and spurious tones arising from their clock circuitry. In this work, we present an FD radio using a highly linear CMOS integrable circulator, a frequency-flat RF canceler, and a USRP software-defined radio (SDR). At TX power level of +15 dBm, the implemented FD radio achieves a self-interference cancellation (SIC) of +55 dB from the circulator and RF canceler in the RF domain, and an overall SIC of +95 dB together with SIC in the digital domain. To analyze the non-linear phenomena of the CMOS circulator, we calculated the link level data-rate gain in an FD system with imperfect SIC and then extended this calculation to count the effect of TX-RX non-linearity of the circulator. In addition, we provide a qualitative discussion on the spurious tone responses of the circulator due to the clocking imperfections and non-linearity.
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non magnetic cmos switched transmission line circulators with high power handling and antenna balancing theory and implementation
IEEE Journal of Solid-state Circuits, 2019Co-Authors: Aravind Nagulu, Harish KrishnaswamyAbstract:Recently, CMOS non-magnetic circulators have been demonstrated based on switch-based spatio-temporal conductivity modulation, but these initial demonstrations remain limited in transmitter power handling, linearity, and ability to combat antenna variations. This paper describes a non-magnetic circulator architecture that uses no external components, and employs a variety of linearity enhancement techniques, such as device stacking, optimal switch biasing, and localized electrostatic discharge (ESD) design to achieve watt-class power handling and high IIP3. A new antenna balancing approach is described that uses no inductors or lossy resistors and yet allows high isolation in the face of strong antenna reflections. The concepts are validated through a 1-GHz 180-nm SOI CMOS prototype that achieves >1-W TX–ANT $\text{P}_{1~{\mathrm{ dB}}}$ , >+50-dBm TX–ANT IIP3, and high isolation for as high as 1.85 ANT VSWR and beyond. The circulator also exhibits low insertion losses of 2.1/2.9 dB in the TX–ANT and ANT–RX paths, and ANT–RX noise figure (NF) of 3.1 dB. These results represent a 10–100 $\times $ enhancement in linearity/power handling over prior non-magnetic circulators and are shown to lower the power consumption of a communication link when compared with the state-of-the-art electrical balance duplexers in scenarios, where dynamic range is limited by $\text{P}_{1~{\mathrm{ dB}}}$ and NF.
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28 5 non magnetic 60ghz soi cmos circulator based on loss dispersion engineered switched bandpass filters
International Solid-State Circuits Conference, 2019Co-Authors: Aravind Nagulu, Harish KrishnaswamyAbstract:There has been significant recent research on non-magnetic non-reciprocal components at RF and mm-waves, such as circulators and isolators, based on spatio-temporal modulation [1-3]. Circulators enable simultaneous transmit and receive (STAR) on a shared antenna for applications such as full-duplex wireless communication and FMCW radar. While there has been exciting initial progress, existing architectures do not scale well to mm-waves, whether they are based on switch-based conductivity modulation [1, 2]or varactor-based permittivity modulation [3]. Loss levels increase due to losses in the switches or varactors, isolation is degraded due to reflections produced by parasitics, and power consumption is high due to the relatively high modulation frequencies required. In this work, we present a non-magnetic CMOS 60GHz circulator based on spatiotemporal conductivity modulation (STCM) across a loss/dispersion-engineered bandpass filter. This new architecture improves the insertion loss, isolation, power consumption, and spurious response compared to prior art. The 60GHz circulator achieves 3.6dB/3.1dB insertion loss for TX-to-ANT/ANT-to-RX paths, respectively, TX-to-RX isolation $> 40$dB over 1.3GHz, 3.2dB of ANT-to-RX NF, $> +19.5$dBm TX-to-ANT/ANT-to-RX IP 1dB S and spurious tones lower than -30dBc at both ANT and RX ports at a power consumption of 41mW from 1.2V.
Dimitrios L Sounas - One of the best experts on this subject based on the ideXlab platform.
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radio frequency magnet free circulators based on spatiotemporal modulation of surface acoustic wave filters
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Giuseppe Michetti, Ahmed Kord, Dimitrios L Sounas, Andrea Alu, Michele Pirro, Zhicheng Xiao, Cristian Cassella, Matteo RinaldiAbstract:In this article, a new generation of magnet-free circulators with high performance is proposed. Circulators are crucial devices in modern communication systems due to their ability to enable full-duplexing and double the spectral efficiency directly in the physical layer of the radio-frequency (RF) front end. Traditionally, the Lorentz reciprocity is broken by applying the magnetic bias to ferrite materials; therefore, conventional circulators are bulky and expensive. In this article, this problem is addressed by replacing the magnetic bias with periodic spatiotemporal modulation. Compared to previous works, the proposed circulator is constructed using surface acoustic wave (SAW) filters instead of transmission lines (TLs), which reduces the modulation frequency by at least a factor of 20 and ensures ultra-low power consumption and high linearity. The miniaturized high quality ( ${Q}$ ) factor SAW filters also lead to a low-loss nonreciprocal band with strong isolation (IX) and broad bandwidth (BW) on a chip scale, therefore addressing such limitations in previous magnet-free demonstrations. Furthermore, compared to the conventional differential circuit configuration, a novel quad configuration is developed, which doubles the intermodulation-free BW.
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radio frequency magnet free circulators based on spatiotemporal modulation of surface acoustic wave filters
arXiv: Signal Processing, 2019Co-Authors: Giuseppe Michetti, Ahmed Kord, Dimitrios L Sounas, Andrea Alu, Michele Pirro, Zhicheng Xiao, Cristian Cassella, Matteo RinaldiAbstract:In this paper, a new generation of magnet-free circulators with high performance is proposed. Circulators are crucial devices in modern communication systems due to their ability to enable full-duplexing and double the spectral efficiency directly in the physical layer of the radio-frequency (RF) front-end. Traditionally, Lorentz reciprocity is broken by applying magnetic bias to ferrite materials, therefore conventional circulators are bulky and expensive. In this paper, this problem is addressed by replacing the magnetic bias with periodic spatiotemporal modulation. Compared to previous works, the proposed circulator is constructed using surface acoustic wave (SAW) filters instead of transmission lines (TL), which reduces the modulation frequency by at least a factor of 20 and ensures ultra-low power consumption and high linearity. The miniaturized high quality (Q) factor SAW filters also lead to a low-loss non-reciprocal band with strong isolation (IX) and broad bandwidth (BW) on a chip scale, therefore addressing such limitations in previous magnet-free demonstrations. Furthermore, compared to the conventional differential circuit configuration, a novel quad configuration is developed, which doubles the intermodulation-free bandwidth.
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Pseudo-Linear Time-Invariant Magnetless Circulators Based on Differential Spatiotemporal Modulation of Resonant Junctions
IEEE Transactions on Microwave Theory and Techniques, 2018Co-Authors: Ahmed Kord, Dimitrios L SounasAbstract:In this paper, we present voltage-mode and current-mode differential magnetless nonreciprocal devices obtained by pairing two single-ended (SE) circulators, each consisting of three first-order bandpass or bandstop LC filters, connected in either a wye or a delta topology. The resonant poles of each SE circulator are modulated in time with 120° phase-shifted periodic signals, resulting in synthetic angular-momentum biasing achieved through spatiotemporal modulation (STM). We tailor the two SE circulators to exhibit a constant 180° phase difference between their STM biases. Unlike conventional differential time-variant circuits, for which only the even or odd spurs are rejected, we show that the proposed configuration cancels out all intermodulation products, thus making them operate alike linear time-invariant (LTI) circuits for an external observer. In turn, this property enhances all metrics of the resulting circulator, overcoming the limitations of SE architectures, and improving insertion loss, impedance matching, bandwidth, and noise figure. We show that this differential architecture also significantly relaxes the required modulation parameters, both in frequency and amplitude. We develop a rigorous small-signal model to guide the design of the proposed circuits and to get insights into their pseudo-LTI characteristics. Then, we validate the theory with simulations and measurements showing remarkable performance compared to the current state-of-the-art of magnetless nonreciprocal devices.
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pseudo linear time invariant magnetless circulators based on differential spatiotemporal modulation of resonant junctions
arXiv: Signal Processing, 2017Co-Authors: Ahmed Kord, Dimitrios L Sounas, Andrea AluAbstract:In this paper, we present voltage- and current-mode differential magnetless non-reciprocal devices obtained by pairing two single-ended (SE) circulators, each consisting of three first-order bandpass or bandstop LC filters, connected in either a wye or a delta topology. The resonant poles of each SE circulator are modulated in time with 120 deg phase-shifted periodic signals, resulting in synthetic angular-momentum biasing achieved through spatiotemporal modulation (STM). We tailor the two SE circulators to exhibit a constant 180 deg phase difference between their STM biases. Unlike conventional differential time-variant circuits, for which only the even or odd spurs are rejected, we show that the proposed configuration cancels out all intermodulation (IM) products, thus making them operate alike linear time-invariant (LTI) circuits for an external observer. In turn, this property enhances all metrics of the resulting circulator, overcoming the limitations of SE architectures, and improving insertion loss, impedance matching, bandwidth and noise figure. We show that this differential architecture also significantly relaxes the required modulation parameters, both in frequency and amplitude. We develop a rigorous small-signal model to guide the design of the proposed circuits and to get insights into their pseudo-LTI characteristics. Then, we validate the theory with simulations and measurements showing remarkable performance compared to the current state of the art of magnetless non-reciprocal devices.
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differential magnetless circulator using modulated bandstop filters
International Microwave Symposium, 2017Co-Authors: Ahmed Kord, Dimitrios L Sounas, Andrea AluAbstract:In this paper, we present a differential magnetless circulator by combining two angular-momentum-biased single-ended circulators, each of which consists of three first-order bandstop LC filters connected in a delta topology and modulated in time with a phase difference of 120 deg between each other. Compared to a single-ended architecture, the differential one drastically reduces even-order intermodulation products, improves insertion loss, extends the bandwidth, and significantly decreases the required modulation frequency. We present the theory of such a circulator and validate it with simulated and measured results.
Ahmed Kord - One of the best experts on this subject based on the ideXlab platform.
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radio frequency magnet free circulators based on spatiotemporal modulation of surface acoustic wave filters
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Giuseppe Michetti, Ahmed Kord, Dimitrios L Sounas, Andrea Alu, Michele Pirro, Zhicheng Xiao, Cristian Cassella, Matteo RinaldiAbstract:In this article, a new generation of magnet-free circulators with high performance is proposed. Circulators are crucial devices in modern communication systems due to their ability to enable full-duplexing and double the spectral efficiency directly in the physical layer of the radio-frequency (RF) front end. Traditionally, the Lorentz reciprocity is broken by applying the magnetic bias to ferrite materials; therefore, conventional circulators are bulky and expensive. In this article, this problem is addressed by replacing the magnetic bias with periodic spatiotemporal modulation. Compared to previous works, the proposed circulator is constructed using surface acoustic wave (SAW) filters instead of transmission lines (TLs), which reduces the modulation frequency by at least a factor of 20 and ensures ultra-low power consumption and high linearity. The miniaturized high quality ( ${Q}$ ) factor SAW filters also lead to a low-loss nonreciprocal band with strong isolation (IX) and broad bandwidth (BW) on a chip scale, therefore addressing such limitations in previous magnet-free demonstrations. Furthermore, compared to the conventional differential circuit configuration, a novel quad configuration is developed, which doubles the intermodulation-free BW.
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radio frequency magnet free circulators based on spatiotemporal modulation of surface acoustic wave filters
arXiv: Signal Processing, 2019Co-Authors: Giuseppe Michetti, Ahmed Kord, Dimitrios L Sounas, Andrea Alu, Michele Pirro, Zhicheng Xiao, Cristian Cassella, Matteo RinaldiAbstract:In this paper, a new generation of magnet-free circulators with high performance is proposed. Circulators are crucial devices in modern communication systems due to their ability to enable full-duplexing and double the spectral efficiency directly in the physical layer of the radio-frequency (RF) front-end. Traditionally, Lorentz reciprocity is broken by applying magnetic bias to ferrite materials, therefore conventional circulators are bulky and expensive. In this paper, this problem is addressed by replacing the magnetic bias with periodic spatiotemporal modulation. Compared to previous works, the proposed circulator is constructed using surface acoustic wave (SAW) filters instead of transmission lines (TL), which reduces the modulation frequency by at least a factor of 20 and ensures ultra-low power consumption and high linearity. The miniaturized high quality (Q) factor SAW filters also lead to a low-loss non-reciprocal band with strong isolation (IX) and broad bandwidth (BW) on a chip scale, therefore addressing such limitations in previous magnet-free demonstrations. Furthermore, compared to the conventional differential circuit configuration, a novel quad configuration is developed, which doubles the intermodulation-free bandwidth.
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Pseudo-Linear Time-Invariant Magnetless Circulators Based on Differential Spatiotemporal Modulation of Resonant Junctions
IEEE Transactions on Microwave Theory and Techniques, 2018Co-Authors: Ahmed Kord, Dimitrios L SounasAbstract:In this paper, we present voltage-mode and current-mode differential magnetless nonreciprocal devices obtained by pairing two single-ended (SE) circulators, each consisting of three first-order bandpass or bandstop LC filters, connected in either a wye or a delta topology. The resonant poles of each SE circulator are modulated in time with 120° phase-shifted periodic signals, resulting in synthetic angular-momentum biasing achieved through spatiotemporal modulation (STM). We tailor the two SE circulators to exhibit a constant 180° phase difference between their STM biases. Unlike conventional differential time-variant circuits, for which only the even or odd spurs are rejected, we show that the proposed configuration cancels out all intermodulation products, thus making them operate alike linear time-invariant (LTI) circuits for an external observer. In turn, this property enhances all metrics of the resulting circulator, overcoming the limitations of SE architectures, and improving insertion loss, impedance matching, bandwidth, and noise figure. We show that this differential architecture also significantly relaxes the required modulation parameters, both in frequency and amplitude. We develop a rigorous small-signal model to guide the design of the proposed circuits and to get insights into their pseudo-LTI characteristics. Then, we validate the theory with simulations and measurements showing remarkable performance compared to the current state-of-the-art of magnetless nonreciprocal devices.
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pseudo linear time invariant magnetless circulators based on differential spatiotemporal modulation of resonant junctions
arXiv: Signal Processing, 2017Co-Authors: Ahmed Kord, Dimitrios L Sounas, Andrea AluAbstract:In this paper, we present voltage- and current-mode differential magnetless non-reciprocal devices obtained by pairing two single-ended (SE) circulators, each consisting of three first-order bandpass or bandstop LC filters, connected in either a wye or a delta topology. The resonant poles of each SE circulator are modulated in time with 120 deg phase-shifted periodic signals, resulting in synthetic angular-momentum biasing achieved through spatiotemporal modulation (STM). We tailor the two SE circulators to exhibit a constant 180 deg phase difference between their STM biases. Unlike conventional differential time-variant circuits, for which only the even or odd spurs are rejected, we show that the proposed configuration cancels out all intermodulation (IM) products, thus making them operate alike linear time-invariant (LTI) circuits for an external observer. In turn, this property enhances all metrics of the resulting circulator, overcoming the limitations of SE architectures, and improving insertion loss, impedance matching, bandwidth and noise figure. We show that this differential architecture also significantly relaxes the required modulation parameters, both in frequency and amplitude. We develop a rigorous small-signal model to guide the design of the proposed circuits and to get insights into their pseudo-LTI characteristics. Then, we validate the theory with simulations and measurements showing remarkable performance compared to the current state of the art of magnetless non-reciprocal devices.
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differential magnetless circulator using modulated bandstop filters
International Microwave Symposium, 2017Co-Authors: Ahmed Kord, Dimitrios L Sounas, Andrea AluAbstract:In this paper, we present a differential magnetless circulator by combining two angular-momentum-biased single-ended circulators, each of which consists of three first-order bandstop LC filters connected in a delta topology and modulated in time with a phase difference of 120 deg between each other. Compared to a single-ended architecture, the differential one drastically reduces even-order intermodulation products, improves insertion loss, extends the bandwidth, and significantly decreases the required modulation frequency. We present the theory of such a circulator and validate it with simulated and measured results.
