Limiting Amplifier Research Articles

Effects of age and hearing loss on overshoot.

The detection of a brief, sinusoidal probe in a long broadband, simultaneous masker improves as the probe is delayed from the masker's onset. This improvement ("overshoot") may be mediated by a reduction in cochlear amplifier gain over the timecourse of the masker via the medial olivocochlear (MOC) reflex. Overshoot was measured in younger adults with normal hearing and in older adults with normal and impaired hearing to test the hypothesis that aging and cochlear hearing loss result in abnormal overshoot, consistent with changes in certain structures along the MOC pathway. Overshoot decreased with increasing quiet probe thresholds and was only minimally influenced by increasing age. Marked individual differences in overshoot were observed due to differences in masking thresholds for probes presented near the masker's onset. Model simulations support the interpretation that reduced overshoot in hearing-impaired listeners is due to limited cochlear amplifier gain and therefore less gain to adjust over the timecourse of the masker. Similar overshoot among younger and older adults with normal hearing suggests that age-related changes to mechanisms underlying overshoot do not result in significant differences in overshoot among younger and older adults with normal hearing.

A 30–75 <inline-formula> <tex-math notation="LaTeX">$\text{dB}\Omega$</tex-math> </inline-formula> 2.5 GHz 0.13-<inline-formula> <tex-math notation="LaTeX">$\mu\text{m}$</tex-math> </inline-formula> CMOS Receiver Front-End With Large Input Capacitance Tolerance for Short-Range Optical Communication

This paper describes the design and implementation of a linear optical receiver front-end for short range optical communication applications in 0.13-μm CMOS technology. While conventional optical receivers are typically implemented using limiting amplifiers (LA), emerging optical systems are expected to employ advanced modulation schemes, which require preserving the signal envelope. The proposed linear optical receiver architecture utilizes super-Gm transimpedance amplification with common-mode restoration and constant settling time automatic gain control (AGC) with background illumination cancellation to preserve the signal linearity while tolerating capacitance up to 15 pF for large area photo-detectors. Linearity aware design of transimpedance amplifiers (TIA), variable gain control (VGA), and post amplifiers (PA) are discussed before introducing an exponential generator based on the parasitic BJTs available in the used technology. Consuming 40 mW from a 1.2 V supply in the presence of ~15 pF input capacitance, the circuit achieves a binary modulation data rate of 5 Gbps with an input sensitivity of ~ 65 μA maintaining a bit-error rate (BER) <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> . S-parameter measurements show a constant -3 dB bandwidth of 2.5 GHz for a wide dynamic range of ~45 dB (30-75 dBΩ) with dB-linearity error better than ±1 dB. To demonstrate the optical functionality of the architecture, an external photodiode (PDCS70T-GS) is directly wirebonded to the chip. Optical measurements confirm a sensitivity of -9.5 dBm (BER <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> ) at a highest data rate of 5 Gb/s (λ = 680 nm). The noise and linearity performance of the receiver is verified using input referred integrated noise and 1 dB-compression point measurements for different gain settings.

Codesign of &lt;italic&gt;Ka&lt;/italic&gt;-Band Integrated Limiter and Low Noise Amplifier

In this paper, a thorough design procedure for concurrent design of integrated antiparallel Schottky-diode-based limiter and low noise amplifier (LNA) is presented. The optimum number of limiter branches, the size and number of diodes in each branch, width of the transmission line loaded by diode branches, and design considerations for input transistor of the LNA are discussed in detail. To improve power handling of the limiter with a minimum impact on overall noise figure (NF), a novel limiter structure is proposed where transistors are utilized in a limiter topology. A design procedure is also introduced for the transistor-based limiter-LNA. Developed methodologies are employed to design and fabricate a diode-based and transistor-based limiter-LNA in a 0.1-μm AlGaAs/InGaAs pHEMT process. Measurement results show that the diode-based limiter-LNA tolerates up to 2-W continuous wave (CW) input power without failure, while transistor-based limiter-LNA is capable of handling 5-W CW input power. Measured average gain and NF for the diode-based limiter-LNA are 21 and 2.3 dB over 28-38-GHz frequency range, while the transistor-based limiter-LNA achieves an average 18-dB small-signal gain and 2.5-dB NF over the 30-38-GHz bandwidth.

Effect of input phase modulation to a phase-sensitive optical amplifier.

Many optical applications depend on amplitude modulating optical beams using devices such as acousto-optical modulators (AOMs) or optical choppers. Methods to add amplitude modulation (AM) often inadvertently impart phase modulation (PM) onto the light as well. While this PM is of no consequence to many phase-insensitive applications, phase-sensitive processes can be affected. Here we study the effects of input phase and amplitude modulation on the output of a quantum-noise limited phase-sensitive optical amplifier (PSA) realized in hot 85Rb vapor. We investigate the dependence of PM on AOM alignment and demonstrate a novel approach to quantifying PM by using the PSA as a diagnostic tool. We then use this method to measure the alignment-dependent PM of an optical chopper which arises due to diffraction effects as the chopper blade passes through the optical beam.

An Ultra-Low Power Subthreshold CMOS RSSI for Wake-Up Receiver

This paper reports an ultra-low power received signal strength indicator (RSSI) for low frequency (LF) wake-up receiver. Topology theory analysis and subthreshold operation are performed to lower power consumption. Each gain stage of the subthreshold limiting amplifier (LA) employs cascade diode-connected loads to obtain high output impedance while maintaining low power. An offset cancelation circuit with different tail currents, which also operates in the subthreshold region, is employed to reduce the DC offset voltage. Unbalanced source-coupled pairs of subthreshold devices adopted in the full-wave rectification are optimized. A 45[Formula: see text]dB input dynamic range and [Formula: see text][Formula: see text]dB indicating error are achieved at 125[Formula: see text]KHz frequency. The prototype occupies an active area of 0.39[Formula: see text][Formula: see text][Formula: see text]0.28[Formula: see text]mm using CSMC 0.153-[Formula: see text]m complementary metal-oxide-semiconductor (CMOS) technology. With a 1.8[Formula: see text]V supply voltage, the overall current consumption is only 6[Formula: see text][Formula: see text]A.

Wavelength dimensioning for wavelength-routed WDM satellite network

Internet and broadband applications driven by data traffic demand have become key drivers for satellite constellations. The key technology to satisfy the high capacity requirements between satellites is optical satellite networks by means of wavelength division multiplexing inter-satellite links (ISLs) with wavelength routing (WDM-OSN). Due to the limited optical amplifier bandwidth onboard the satellite, it is important to minimize the wavelength requirements to provision requests. However, ISLs should be dynamically established and deleted for each satellite according to its visible satellites. Furthermore, different link assignments will result in different topologies, hence yielding different routings and wavelength assignments. Thus, a perfect match model-based link assignment scheme (LAS-PMM) is proposed to design an appropriate topology such that shorter path could be routed and less wavelengths could be assigned for each ISL along the path. Finally, simulation results show that in comparison to the regular Manhattan street network (MSN) topology, wavelength requirements and average end-to-end delay based on the topology generated by LAS-PMM could be reduced by 24.8% and 12.4%, respectively.

Design of a high gain and power efficient optical receiver front-end in 0.13 μM RF CMOS technology for 10 Gbps applications

In this paper, two versions of a complete RF front-end for a 10 Gbps optical receiver are presented. The RF front-end consists of a transimpedance amplifier and a limiter amplifier. Two versions of the TIA amplifiers are proposed. The first topology has 54 dB transimpedance gain, 11.5 GHz bandwidth and has a input current noise density of only 6.8pA/Hz. The second topology is composed by a cascade os two inverters. This topology has 48 dB transimpedance gain, 11.2 GHz bandwidth, a input current noise density of 8.9pA/Hz and occupies an area of only 0.048 mm2. The limiter amplifier for both optical receivers is a five stage cherry-hooper amplifier with active inductors optimized for low power. The main amplifier has 38 dB gain, 9.8 GHz Bandwidth, 69 mW of power consumption and only 0.171 mm2 of die area. The complete RF front-end is fully integrated and has 10 GHz bandwidth. The circuits were designed in 0.13 μm RF CMOS technology. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1499–1504, 2016

Superconducting microwave parametric amplifier based on a quasi-fractal slow propagation line

Quantum limited amplifiers are sought after for a wide range of applications within quantum technologies and sensing. One promising candidate is the travelling wave parametric amplifier which exploits the non-linear kinetic inductance of a superconducting transmission line. This type of microwave amplifier promises to deliver a high gain, a quantum limited noise performance over several GHz bandwidth, and a high dynamic range. However, practical realizations of this type of device have so far been limited by fabrication defects, since the length of the superconducting transmission line required for achieving substantial parametric gain is on the order of ∼1 m. Here, we report on a design for a microwave traveling wave amplifier based on a slow propagation line comprising a central strip with high kinetic inductance and quasi-fractal line-to-ground capacitors. Due to an enhanced per unit length inductance (73 nH cm−1) and capacitance (15 pF cm−1), the line has a microwave propagation velocity as low as 9.8 × 108 cm s−1. This translates into parametric gain up to 0.5 dB cm−1 and a total gain of 6 dB for just a ∼10 cm long transmission line. Moreover, the flexibility of the presented design allows balancing the line inductance and capacitance in order to keep the characteristic impedance close to 50 Ω and to suppress standing waves, both factors being essential in order to implement a practical parametric amplifier in the microwave domain.

Capacity maximization based power loading analysis for digital channelized satcom systems

For digital channelized frequency division multiple access based satellite communication (SATCOM) systems, it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously under limited and non-linear high-power amplifier conditions. In this paper, different from the traditional link supportability designs aiming at minimizing the total transponder output power, a maximal sum Shannon capacity optimization objective is firstly raised subject to link supportability constraints. Furthermore, an efficient multilevel optimization (MO) algorithm is proposed to solve the considered optimization problem in the case of single link for each terminal. Moreover, in the case of multiple links for one terminal, an improved MO algorithm involving Golden section and discrete gradient searching procedures is proposed to optimize power allocation over all links. Finally, several numerical results are provided to demonstrate the effectiveness of our proposals. Comparison results show that, by the MO algorithm, not only all links' supportability can be guaranteed but also a larger sum capacity can be achieved with lower complexity.

4 × 25 Gb/s 2.6 mW/Gb/s parallel optical receiver analog front‐end for 100 Gb/s Ethernet

ABSTRACTA design of 4 × 25 Gb/s parallel optical receiver analog front‐end, including transimpedance amplifier (TIA) and limiting amplifier (LA), is presented in this article. It features a pseudodifferential TIA structure to cancel common mode noise and stabilize circuit. The TIA and LA use regulated cascode technique and four stages interleaving active feedback structure to acquire 23.2 GHz bandwidth and 74.3 dBΩ transimpedance gain. The parallel TIA and LA chip occupies 525 × 1835 μm2 area. It consumes 76 mW per channel and the power consumption per bit is only 2.6 mW/Gb/s. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:974–978, 2015

Millimeter-wave multimedia communications: challenges, methodology, and applications

The worldwide opening of a massive amount of unlicensed millimeter-wave spectrum has triggered great interest in developing high-bit-rate multimedia services and applications. Specific challenges for mmWave communication design include large-scale attenuation, atmospheric absorption, phase noise, limited gain amplifiers, and so on. This article aims to define and evaluate important metrics to characterize multimedia QoS and jointly takes these technical challenges into account in the framework of mmWave. To this end, we design a QoS-aware multimedia scheduling scheme to achieve the trade-off between performance and complexity, in which accurate propagation analysis is carried out and suitable countermeasure techniques are pointed out to satisfy the QoS requirements. Moreover, potential multimedia applications are analyzed and possible solutions provided. Illustrative results indicate that the proposed multimedia scheduling scheme can perform efficiently in a practical mmWave communication system.

Non-Poissonian quantum jumps of a fluxonium qubit due to quasiparticle excitations.

As the energy relaxation time of superconducting qubits steadily improves, nonequilibrium quasiparticle excitations above the superconducting gap emerge as an increasingly relevant limit for qubit coherence. We measure fluctuations in the number of quasiparticle excitations by continuously monitoring the spontaneous quantum jumps between the states of a fluxonium qubit, in conditions where relaxation is dominated by quasiparticle loss. Resolution on the scale of a single quasiparticle is obtained by performing quantum nondemolition projective measurements within a time interval much shorter than T₁, using a quantum-limited amplifier (Josephson parametric converter). The quantum jump statistics switches between the expected Poisson distribution and a non-Poissonian one, indicating large relative fluctuations in the quasiparticle population, on time scales varying from seconds to hours. This dynamics can be modified controllably by injecting quasiparticles or by seeding quasiparticle-trapping vortices by cooling down in a magnetic field.

Design and analysis of 20 Gb/s inductorless limiting amplifier in 65 nm CMOS technology

A high speed inductorless limiting amplifier (LA) in an optical communication receiver with the working speed up to 20 Gb/s is presented. The LA includes an input matching network, a four-stage 3rd order amplifier core, an output buffer for the test and a DC offset cancellation (DCOC). It uses the active interleaving feedback technique both to broaden the bandwidth and achieve the flatness response. Based on our careful analysis of the DCOC and stability, an error amplifier is added to the DCOC loop in order to keep the offset voltage reasonable. Fabricated in the 65 nm CMOS technology, the LA only occupies an area of 0.45 × 0.25 mm2 (without PAD). The measurement results show that the LA achieves a differential voltage gain of 37 dB, and a 3-dB bandwidth of 16.5 GHz. Up to 26.5 GHz, the Sdd11 and Sdd22 are less than −16 dB and −9 dB. The chip excluding buffer is supplied by 1.2 V VDD and draws a current of 50 mA.

A CMOS LOW-POWER TEMPERATURE-ROBUST RSSI USING WEAK-INVERSION LIMITING AMPLIFIERS

This paper presents a low-power CMOS receiving signal strength indicator (RSSI). The main architecture of the circuit adopts a six-stage limiting amplifier (LA) in a logarithmic-linear form, which shows a good performance in weak signal detection. The RSSI achieves high tolerance to process, voltage, and temperature (PVT) variations by utilizing the unique nature of branch currents in a transconductance amplifier. The power consumption is decreased by using the weak-inversion LAs. Full-waveform current rectification and summation are employed in the RSSI circuit to achieve high precision while maintaining low power consumption. Measured results show that in the 1 kHz–50 MHz frequency range, the input dynamic range is wider than 70 dB within ±2 dB linearity error. The chip occupies an area of 0.7 mm2 × 0.3 mm2 using a 0.18-μm CMOS. It draws 1.3 mA from a 1.8 V supply.

A 38 Gb/s to 43 Gb/s Monolithic Optical Receiver in 65 nm CMOS Technology

A scaled 40 Gb/s optical receiver incorporating a transimpedance amplifier (TIA), a limiting amplifier (LA), a clock and data recovery (CDR), and a 1:4 demultiplexer was proposed in 65 nm CMOS technology. The TIA employs a regulated cascode structure to achieve low input resistance and a stable dc operating point, whereas the LA adopts the third-order interleaving active feedback technique to obtain greater bandwidth and flatter frequency response. A 10 GHz LC-based voltage controlled oscillator with a ring structure that generates eight phases is presented. A quarter-rate phase detector in the CDR samples the 40 Gb/s input data, which are retimed and demultiplexed into four sets of 10 Gb/s output data. Experimental results show that the recovered clock exhibits a phase noise of -112.39 dBc/Hz@10 MHz from a carrier frequency of 10 GHz, in response to 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sup> -1 PRBS input. The retimed and demultiplexed data exhibit a peak-peak jitter of 4.46 ps and an RMS jitter of 1.18 ps. The core circuit of the receiver consumes 160 mW from a 1.2 V supply.

A 10-Gb/s 0.18-μm CMOS Optical Receiver Front-End Amplifier

A fully integrated 10-Gb/s optical receiver analog front-end (AFE) design that includes a transimpedance amplifier (TIA) and a limiting amplifier (LA) is demonstrated to require less chip area and is suitable for both low-cost and low-voltage applications. The AFE is stimulation using a 0.18μm CMOS process. In order to avoid off-chip noise interference, the TIA and LA are dc-coupled on the chip instead of ac-coupled though a large external capacitor. The tiny photo current received by the receiver AFE is amplified to voltage swing of 400. The results indicate that, with a photodiode parasitic capacitance of 500fF and the bonding pad parasitic capacitance of 200fF between which a 2-mm bond wire is inserted at the input node, the AFE provides a conversion gain of up to 89.21 dB and 3 dB bandwidth of 9.78 GHz. Operating under a 1.8V supply, circuit power dissipation is 95 mW and its sensitivity is 18.5μA for BER of 10-12

A process/temperature variation tolerant RSSI

A low power process/temperature variation-tolerant CMOS received signal strength indicator (RSSI) and limiter amplifier are designed using SMIC 0.13 μm CMOS technology. The limiter uses six-stage amplifier architecture for minimum power consideration. The RSSI has a dynamic range of more than 60 dB, and the RSSI linearity error is within ±0.5 dB for an input power from −65 to −8 dBm. The RSSI output voltage is from 0.15 to 1 V and the slope of the curve is 14.17 mV/dB. Furthermore, with the compensation circuit, the proposed RSSI shows good temperature independence and robustness against process variation characteristics. The RSSI with an integrated AGC loop draws 1.5 mA (I and Q paths) from a 1.2 V single supply.

Quantum optomechanics with a high-frequency dilational mode in thin dielectric membranes

The interaction between a high-frequency dilational mode of a thin dielectric film and an optical cavity field is studied theoretically in the membrane-in-the-middle setup. A derivation from first principles leads to a multi-mode optomechanical Hamiltonian where multiple cavity modes are coupled by the thickness variation of the membrane. For membrane thicknesses of the order of 1 μm, the frequency of this dilational mode is in the GHz range. This can be matched to the free spectral range of the optical cavity, such that the mechanical oscillator will resonantly couple cavity modes at different frequencies. Furthermore, such a large mechanical frequency also means that the quantum ground state of motion can be reached with conventional refrigeration techniques. Estimation of the coupling strength with realistic parameters suggests that optomechanical effects can be observable with this dilational mode. It is shown how this system can be used as a quantum limited optical amplifier. The dilational motion can also lead to quantum correlations between cavity modes at different frequencies, which is quantified with an experimentally accessible two-mode squeezing spectrum. Finally, an explicit signature of radiation pressure shot noise in this system is identified.

Experimental Investigation on 1018-nm High-Power Ytterbium-Doped Fiber Amplifier

We present an all-fibered 1018-nm ytterbium-doped double-clad fiber laser in master oscillation power amplification configuration. The output characteristics of 1018-nm laser with seed power, gain fiber length, and fiber type are experimentally investigated. The power of the seed laser needs to be much higher to suppress amplified spontaneous emission and enable the sufficient amplification of the 1018-nm seed laser than the case of 1080-nm amplification. And the requirement of the seed power increases with the gain fiber length. The experimental results also indicate that gain fiber with large pump fill factor and low Yb ion concentration is more appropriate for the high-power 1018-nm fiber laser. With this gain fiber, we demonstrate a 77-W near diffraction limited fiber amplifier emitting at 1018 nm with power conversion efficiency of 75%.

Modeling of Burst Mode 2R Optical Regenerator Cascades for Long-Haul Optical Networks

A complete system-level model for cascades of burst mode 2R optical regenerators (BMOR), each consisting of an optical limiting amplifier (LA) followed by an optical reshaper, is presented for optical packet/burst-switched optical networks. The major distinction compared to continuous-mode 2R OR is that a BMOR can successfully handle the large power variations because of the LA, and the impact of inclusion of this into the system analysis is presented here. The bit error rate is evaluated along a cascade of identical BMORs, interspersed with heterogeneous inter-regenerator links (i.e., varying amplified spontaneous emission noise and net gains) which further complicate the burst mode case relative to the continuous mode. The dependency of performance of the cascade on the characteristics of the LA is investigated.