Limiting Amplifier Research Articles

In-operando microwave scattering-parameter calibrated measurement of a Josephson traveling wave parametric amplifier

Superconducting traveling wave parametric amplifiers (TWPAs) are broadband near-quantum limited microwave amplifiers commonly used for qubit readout and a wide range of other applications in quantum technologies. The performance of these amplifiers depends on achieving impedance matching to minimize reflected signals. Here, we apply a microwave calibration technique to extract the S-parameters of a Josephson junction based TWPA in-operando. This enables reflections occurring at the TWPA and its extended network of components to be quantified, and we find that the in-operation performance can be well described by the off-state measured S-parameters.

Josephson parametric amplifier based quantum noise limited amplifier development for axion search experiments in CAPP

Josephson parametric amplifier based quantum noise limited amplifier development for axion search experiments in CAPP

Evaluation on quantum illumination radar with quantum limited amplification.

Based on Quantum illumination (QI) protocol, researcshers have developed prototypes of quantum radar and demonstrated its quantum enhancement. Nevertheless, there are still difficulties in the practical application for QI radar, especially the trade-off between the detection range and quantum enhancement, as well as the construction of the optimized receiver. Some studies have suggested that the potential solutions to these difficulties are to deploy the quantum limited amplifiers in QI radars, and have envisioned different amplification schemes. In this paper, we establish a universal and effective method to evaluate the signal-to-noise ratio of QI radar. It connects QI radar theory with classical radar signal processing theory, providing support for researchers to evaluate the performance of various QI radar schemes from a radar perspective. Based on this method, we prove that any quantum limited phase-insensitive amplification scheme will seriously weaken the quantum enhancement of QI radar. Furthermore, we also demonstrate that the QI radar with phase-sensitive amplified idler has no advantage over the optimal classical illumination. These results can help us avoid some unreasonable QI radar schemes. In addition, we believe that the proposed method can also be applied to explore other potential QI radar schemes and contribute to promoting the application development of QI radar.

Formal relation between Pegg-Barnett and Paul quantum phase frameworks

The problem of defining a hermitian quantum phase operator is nearly as old as quantum mechanics itself. Throughout the years, a number of solutions was proposed, ranging from abstract operator formalisms to phase-space methods. In this work, we make an explicit connection between two of the most prominent approaches, by proving that the probability distribution of phase in the Paul formalism follows exactly from the Pegg-Barnett formalism by combining the latter with the quantum limited amplifier channel. Our findings suggest that the Paul framework may be viewed as a semi-classical limit of the Pegg-Barnett approach.

Superconducting Resonators with Voltage-Controlled Frequency and Nonlinearity

Voltage-tunable superconductor-semiconductor devices offer a unique platform to realize dynamic tunability in superconducting quantum circuits. By galvanically connecting a gated $\mathrm{In}\mathrm{As}$-$\mathrm{Al}$ Josephson junction to a coplanar waveguide resonator, we demonstrate the use of a superconducting element with wideband gate tunability. We show that the resonant frequency is controlled via a gate-tunable Josephson inductance and that the nonlinearity of the $\mathrm{In}\mathrm{As}$-$\mathrm{Al}$ junction is nondissipative as is the case with conventional ${\mathrm{Al}\mathrm{O}}_{\mathrm{x}}\text{-Al}$ junctions. As the gate voltage is decreased, the inductive participation of the junction increases up to $44\mathrm{%}$, resulting in the resonant frequency being tuned by over $2\phantom{\rule{0.2em}{0ex}}\mathrm{GHz}$. Utilizing the wide tunability of the device, we demonstrate that two resonant modes can be adjusted such that they strongly hybridize, exhibiting an avoided-level crossing with a coupling strength of $51\phantom{\rule{0.2em}{0ex}}\mathrm{MHz}$. Implementing such voltage-tunable resonators is the first step toward realizing wafer-scale continuous voltage control in superconducting circuits for qubit-qubit coupling, quantum limited amplifiers, and quantum memory platforms.

A Ka-Band Series Structure Switchable Power Detector System

In this letter, a Ka-band series structure switchable power detector (PD) system equipped with a switchable transformer is proposed for switching detected regions at different input powers. To simultaneously achieve high gain and save dc power, the main RF path is included in a four-stage limiting amplifier (LA) that relies on the double-transformer-coupling (DTC) and current re-used (CR) technique. By switching different detectable paths containing the switchable transformer and PD, the detectable region is changed to a different power region. At a log error of ±1 dB, the measured results indicate that the minimum detectable power (MDP) and dynamic range (DR) are -42 dBm and 49 dB, respectively, at 26 GHz. In the four modes, the measured peak slope values are 30/35/36/34 mV/dB, respectively. At a supply voltage of 1.2 V, the dc power of the PD system is 8.4 mW. These results indicate that, compared with amplifier-based PD systems, the proposed system has a better MDP and DR, and the lowest dc power.

Noise Reduction in Qubit Readout with a Two-Mode Squeezed Interferometer

Fault-tolerant quantum information processing with flawed qubits and gates requires highly efficient, quantum nondemolition qubit readout. In superconducting circuits, qubit readout using coherent light with fidelity above 99% has been achieved by using quantum limited parametric amplifiers such as the Josephson parametric converter (JPC). However, further improvement of such measurement faces many challenges, including the vacuum fluctuation of the coherent light that limits measurement fidelity. In this work we demonstrate dispersive qubit readout with a two-mode squeezed light interferometer formed by two JPCs. The first JPC generates two-mode squeezed vacuum at its output, which is coherently recombined by the second JPC after one branch is phase shifted and displaced by its interaction with the qubit-cavity system on that arm of the interferometer. We observe a 31% improvement in the power signal-to-noise ratio (SNR) of projective readout after replacing vacuum fluctuation in the readout cavity with two-mode squeezed vacuum containing on average one photon. This demonstrates a more efficient way of improving SNR than by increasing readout power. Furthermore, we investigate the quantum properties of the two-mode squeezed light in the system through weak measurement. Surprisingly, we find that tuning the interferometer to be less projective increases the measurement efficiency relative to the optimum setting for projective measurement. These enhancements may enable remote entanglement with lower efficiency components in a system with qubits in both arms of the interferometer.

CAN YOU HEAR ME? A MEDICAL STUDENT-LED QUALITY IMPROVEMENT INITIATIVE FOR HOSPITALIZED PATIENTS WITH HEARING LOSS

Abstract In acute care settings hearing loss (HL) is associated with impaired patient-provider communication, increased length of stay, and increased mortality. COVID-19 has exacerbated this problem with the widespread use of masks and eye shields which muffle speech and prevent lip reading. Our 800-bed tertiary care medical center lacked a standardized approach to identify patients with HL and address communication barriers. Three first year medical students spearheaded the initiative as part of a health systems improvement curriculum with support from a faculty coach and a faculty researcher. From September 2020 to October 2021, the students met with stakeholders, leadership and champions and unit staff, identified the current state and completed a gap analysis through interviews, surveys, and direct observation. The pilot in May 2021 included two week-long PDSA cycles on one hospital unit to: 1) screen patients aged 65 and older using the validated 10-item HHIE-S questionnaire, 2) implement an education and awareness campaign with bedside signage, posters, and conferences and 3) provide a personal amplifier (purchased in bulk by the medical center) with verbal and written instructions. A total of 29 patients screened positive and were given personal amplifiers. Post-pilot interviews reported increased provider awareness and knowledge around best communication practices. Patients and staff reported limited amplifier use due to poor sound quality, small dials, poorly fitting ear buds and a short battery life. Based on these results the team recommended discontinuing the personal amplifiers and identifying other communication tools including higher quality personal amplifiers and speech to text applications.

A 27–35 GHz wideband PIN-diode limiter low noise amplifier MMIC with sub-2.4 dB noise figure

In this paper, a thorough co-design procedure for the integrated PIN-diode limiter and low noise amplifier (LNA) is presented. A 27 GHz–35 GHz wideband integrated limiter low noise amplifier (limiter-LNA) is fabricated with the combined PIN/0.15-μm-pHEMT technology for millimeter-wave radar applications. The PIN-diode limiter and the LNA are co-designed to improve the small signal performance. To improve the noise performance and the input-matching of the limiter-LNA, a novel limiter design method with the modified lossy TL model is presented. The measurement results illustrate that the small-signal gain is 20 ± 0.7 dB, the noise figure (NF) is 1.9 dB–2.4 dB, the output power at 1 dB compression point (OP1dB) is larger than 12.1 dBm and the dc power consumption is only 96-mW. The limiter-LNA is capable of handling 38 dBm continuous wave (CW) input-power without failure. The chip area including testing pads is 2.3 mm × 1.0 mm.

Axion dark matter: How to see it?

The axion is a highly motivated elementary particle that could address two fundamental questions in physics—the strong charge-parity (CP) problem and the dark matter mystery. Experimental searches for this hypothetical particle started reaching theoretically interesting sensitivity levels, particularly in the micro–electron volt (gigahertz) region. They rely on microwave resonators in strong magnetic fields with signals read out by quantum noise limited amplifiers. Concurrently, there have been intensive experimental efforts to widen the search range by devising various techniques and to enhance sensitivities by implementing advanced technologies. These orthogonal approaches will enable us to explore most of the parameter space for axions and axion-like particles within the next decades, with the 1- to 25-gigahertz frequency range to be conquered well within the first decade. We review the experimental aspects of axion physics and discuss the past, present, and future of the direct search programs.

LDLA14: a 14 Gbps optical transceiver ASIC in 55 nm for NICA multi purpose detector project

This paper presents the design and test results of a 14 Gbps optical transceiver ASIC (LDLA14) fabricated in a 55 nm CMOS technology for NICA Multi Purpose Detector (MPD) project. The LDLA14 is a single-channel bidirectional (1Tx + 1Rx) optical transceiver ASIC, including a Laser Driver (LD) module and a Limiting Amplifier (LA) module. It would drive the Vertical Cavity Surface Emitting Laser (VCSEL) of Transmitter Optical Sub-Assembly (TOSA) and receive signals from Photo Diode (PD) of Receiver Optical Sub-Assembly (ROSA), respectively. In the LDLA14, a novel structure of capacitive coupling pre-emphasis is proposed in the output driver of LD to obtain peaking effect without sacrifice the modulation current swing. A shared inductor technology and a Continuous Time Linear Equalizer (CTLE) pre-emphasis structure are added in the output buffer of LA to improve the quality of the output eye diagram. The dimension of LDLA14 is 1.5 mm × 1.3 mm, and the power consumption is 178 mW. The Peak-to-Peak Jitter (PPJ) and Root-Mean-Square Jitter (RMSJ) of the 14 Gbps optical eye diagram of LD in the Tx direction are 22.5 ps and 3.5 ps, respectively. The PPJ and RMSJ of the 14 Gbps electrical eye diagram of LA in the Rx direction are 23.1 ps and 4.7 ps, respectively. The BER tests have been conducted in Tx, Rx directions and the Tx-Rx loop condition, and the BER less than 10−12 is achieved in all tests.

A 40-Gb/s, 900-fJ/bit Dual-Channel Receiver in a 45-nm Monolithic RF/Photonic Integrated Circuit Process

An energy-efficient dual-channel receiver (RX) for short range optical interconnects is integrated in a 45-nm RF/photonic process and characterized for electrical bandwidth to de-embed the photonic device limitations. Each channel receiver consists of a low-power transimpedance amplifier (TIA), limiting amplifier (LA), and output buffer (OB) which is implemented with minimal area footprint using active gyrators and feedforward capacitive compensation for bandwidth enhancement and only a single pair of inductors on the OB. The electrical characterization includes the data rate and bit error rate (BER) to 40 Gb/s per channel. The total energy efficiency is 0.9 pJ/bit including the output buffer and 0.36 pJ/bit excluding the OB at a data rate of 40 Gb/s per channel.

Noise figure and input intercept point's errors in an AGC‐less microwatt ultrawideband system (limiter and low noise amplifier)

The goal is to illustrate new errors about using the figures-of-merit NF and IIP, by investigating an AGC-less microwatt ultrawideband g m -boosted CMOS RF system with noise/distortion cancellation. The system composed of limiter and LNA is designed for 0.3–10.7 GHz at 1.8 V. Thanks to the limiter, the impact of noises and distortions is cancelled and the LNA acts linear without any saturation or block, as well as, it becomes AGC-less. Additionally, achievements prove that NF and IIP sometimes can be accompanied by error, hence engineers must always consider all aspects of a system together during their evaluations. Although this work is not experimental, it applies different methods such as “Regenerating”, “Comparing Calculations with Simulations” and “Monte Carlo” to demonstrate the reliability of achievements for applying in a SAW-less RFIC.

A 10-Gb/s Driver/Receiver ASIC and Optical Modules for Particle Physics Experiments

We present the design and test results of a Drivers and Limiting AmplifierS ASIC operating at 10 Gb/s (DLAS10) and three miniature optical transmitter/ receiver/transceiver modules (MTx+, MRx+, and MTRx+) based on DLAS10. DLAS10 can drive two transmitter optical subassemblies (TOSAs) of vertical cavity surface emitting lasers (VCSELs), receive the signals from two receiver optical subassemblies (ROSAs) that have no embedded limiting amplifiers (LAs), or drive a VCSEL TOSA and receive the signal from a ROSA, respectively. Each channel of DLAS10 consists of an input continuous time linear equalizer (CTLE), a four-stage LA, and an output driver. The LA amplifies the signals of variable levels to a saturation amplitude of 800 mV (peak-peak). The output driver drives VCSELs or impedance-controlled traces. DLAS10 is fabricated in a 65-nm CMOS technology. The die is 1 mm ×1 mm. DLAS10 is packaged in a 4 mm ×4 mm 24-pin quad-flat no-leads (QFNs) package. DLAS10 has been tested in MTx+, MRx+, and MTRx+ modules. Both measured optical and electrical eye diagrams pass the 10-Gb/s eye mask test. The input electrical sensitivity is 40 mVp-p, while the input optical sensitivity is -12 dBm. The total jitter of MRx+ is 29 ps (P-P) with a random jitter of 1.6 ps (rms) and a deterministic jitter of 9.9 ps. Each MTx+/MRx+ module consumes 82.6 and 174.4 mW/ch, respectively.

Data rate enhancement of free space optical communication using pulse positioned differential phase shift keying.

In this paper, a pulse positioned-differential phase shift keying technique is proposed to enhance the data rate in free space optical communication. Using the schematics of polarization rotation differential phase shift keying, multi-rate functionality can be achieved without using delay-line interferometers. Furthermore, the proposed novel modulation format-differential phase shift keying combined with pulse-position modulation-enables a high data rate owing to the use of an average power limited amplifier. By using the average power limited amplifier, the signal power is increased as the pulse position order increases, which enhances the bit-error-rate performance. The increased signal power can be converted to an enhanced data rate. We demonstrated that the data rate above 625 Mbps can be increased in every step, as the pulse position order increases in the pulse positioned-differential phase shift keying. The performance enhancement of the proposed technique is theoretically and experimentally demonstrated.

Searching for Dark Matter with a Superconducting Qubit.

Detection mechanisms for low mass bosonic dark matter candidates, such as the axion or hidden photon, leverage potential interactions with electromagnetic fields, whereby the dark matter (of unknown mass) on rare occasion converts into a single photon. Current dark matter searches operating at microwave frequencies use a resonant cavity to coherently accumulate the field sourced by the dark matter and a near standard quantum limited (SQL) linear amplifier to read out the cavity signal. To further increase sensitivity to the dark matter signal, sub-SQL detection techniques are required. Here we report the development of a novel microwave photon counting technique and a new exclusion limit on hidden photon dark matter. We operate a superconducting qubit to make repeated quantum nondemolition measurements of cavity photons and apply a hidden Markov model analysis to reduce the noise to 15.7dB below the quantum limit, with overall detector performance limited by a residual background of real photons. With the present device, we perform a hidden photon search and constrain the kinetic mixing angle to ε≤1.68×10^{-15} in a band around 6.011GHz (24.86 μeV) with an integration time of 8.33s. This demonstrated noise reduction technique enables future dark matter searches to be sped up by a factor of 1,300. By coupling a qubit to an arbitrary quantum sensor, more general sub-SQL metrology is possible with the techniques presented in this Letter.

Concurrent design of Schottky diode limiter and LNA

In this paper concurrent design of Schottky diode based limiter and low noise amplifier (LNA), based on noise matching, is investigated to achieve minimum noise figure (NF) of the receiver chain. In design procedure of the LNA, the noise figure is minimum, gain at central frequency is 14.5 dB, and limiter structure tolerates up to 5 W continuous wave input power. In the proposed concurrent design, a pass-band filter is applied at the LNA output to attenuate undesired out-of-band signals. In the proposed design, the limiter-LNA is implemented with a 0.25 µm gate length AlGaAs/InGaAs pHEMT process. Measured noise figure of chain is 2.7 dB and average gain over 8.5–9.5 GHz frequency range and the gain at 9 GHz center frequency are 10 dB and 14.5 dB respectively. The performance results of proposed matching network are compared with traditional 50 Ω matching networks in limiter-LNA with identical circuit specifications.

A 25 Gbps single‐end input limiting amplifier with loss of signal for low power integrated optical receivers

AbstractA 25 Gbps limiting amplifier (LA) with loss of signal (LOS) detection is presented in this paper. The proposed LA is composed of an input buffer, three‐stage cascaded amplifier, an output buffer, a DC offset cancellation (DCOC) and a LOS circuit. The LA adopts single‐end input and differential output structure to reduce the complexity of optical receiver front‐end and therefore decrease power consumption drastically. DCOC circuit consists of a low‐pass filter and an operation amplifier to extract the DC point of transimpedance amplifier output signal. Replica peak detector is employed in LOS to overcome the fluctuations of process, voltage, temperature (PVT). Fabricated in 0.13 μm SiGe BiCMOS technology, the LA acquires gain of 43.5, –3 dB bandwidth of 20.6 GHz and differential output voltage swing of 350 mV. With the 20 mV PRBS31 input data, the peak‐to‐peak jitter of output signal is 13.9 ps. When the input swing is larger than 40 mV, the peak‐to‐peak jitter is decreased to 7.5 ps. The whole LA with LOS chip only consumes 25.2 mW with a 1.8 V supply voltage.

A Low-power, CMOS Optical Communication Receiver System for 5Gbps Applications based on RGC Structure

An optical communication receiver system is presented in this research using 65nm CMOS, which consists of three lowpower active differential stages as Limiting Amplifier (LA) following an ultra-low-power RGC-Based Transimpedance Amplifier (RB-TIA). The presented active circuit of the RB-TIA is followed by a gain stage that extends the -3dB frequency of the circuit by creating a resonance for the load capacitance. Thus, needless of consuming extra power, a wide-bandwidth circuit has been designed. In addition, employing active-inductor loads within the LA stages enables obtaining a 5Gbps receiver system. The RB-TIA consumes 573µW and provides 3.52GHz frequency, while the complete optical receiver consumes only 4.76mW power to provide -3dB frequency of 3.5GHz and high gain of 80dB (10’000). The circuits have been mathematically presented and discussed, and simulations have justified the presented circuit design.

A 1.2V 0.2mW 27MHz CMOS limiting amplifier using cross-coupled active load structure

ABSTRACT This paper presents a 1.2 V 0.2 mW CMOS limiting amplifier (LiA) designed in both schematic and layout levels using 130 nm CMOS technology. A cross-coupled active load structure is used to provide high differential gain and low common mode gain for the design. A common mode logic (CML) to CMOS level conversion topology is used to convert the differential input signal into a single-ended output signal for the proposed design. The designed circuit generates clock signal and behaves effectively up to modulation index variation ≤0.3 for input signal variation up to 40mVp-p. A bandwidth of 27 MHz is chosen for the amplifier design and the measurement shows a differential gain of 60 dB with a power consumption of about 0.2 mW excluding power consumption in buffer stage.