Tunnel Diode Oscillator Research Articles

Resonant Tunneling Diode (RTD) Terahertz Active Transmission Line Oscillator with Graphene-Plasma Wave and Two Graphene Antennas

This study describes the design of a resonant tunneling diode (RTD) oscillator (RTD oscillator) with a RTD-gated-graphene-2DEF (two dimensional electron fluid) and demonstrates the functioning of this RTD oscillator through a transmission line simulation model. Impedance of the RTD oscillator changes periodically when physical dimension of the device is of considerable fraction of the electrical wavelength. As long as impedance matching is achieved, the oscillation frequency is not limited by the size of the device. An RTD oscillator with a graphene film and negative differential resistance (NDR) will produce power amplification. The positive electrode of the DC power supply is modified and designed as an antenna. So, the reflected power can also be radiated to increase RTD oscillator output power. The output analysis shows that through the optimization of the antenna structure, it is possible to increase the RTD oscillator output to 22 mW at 1.9 THz and 20 mW at 6.1 THz respectively. Furthermore, the RTD oscillator has the potential to oscillate at 50 THz with a matching antenna.

High-Efficiency Bias Stabilization for Resonant Tunneling Diode Oscillators

We report on high-efficiency, high-power, and low-phase-noise resonant tunneling diode (RTD) oscillators operating at around 30 GHz. By employing a bias stabilization network, which does not draw any direct current (dc), the oscillators exhibit over a tenfold improvement in the dc-to-RF conversion efficiency (of up to 14.7%) compared to conventional designs (~0.9%). The oscillators provide a high maximum output power of around 2 dBm, and low phase noise of −100 and −113 dBc/Hz at 100 kHz and 1 MHz offset frequencies, respectively. The proposed approach will be invaluable for realizing very high efficiency, low phase noise, and high-power millimeter-wave (mm-wave) and terahertz (THz) RTD-based sources.

Large-scale array of resonant-tunneling-diode terahertz oscillators for high output power at 1 THz

We proposed and fabricated large-scale arrays of resonant tunneling diode (RTD) oscillators for high-output-power terahertz (THz) sources. The array element is composed of an RTD, a slot resonator, and a dipole array antenna on a dielectric layer stacked on the RTD. In this structure, the output power is radiated in the upward direction of the substrate without a hemispherical silicon lens. The dipole array antenna was designed so that the average output power determined by the variation in the size of the RTD in the array was maximized. The experimental output power was proportional to the element number, and its value was 0.73 mW for an 89-element array at ∼1 THz in a pulsed mode with a repetition rate of 300 Hz and a duty ratio of 10%. Multiple peaks were observed in the oscillation spectra, because the elements were not intentionally coupled with each other. The average output power per element was 9 μW in the array, which was lower than that of the separated single oscillators (21 μW). Possible causes of this difference are discussed.

Evidence for unconventional superconductivity in half-Heusler YPdBi and TbPdBi compounds revealed by London penetration depth measurements

The half-Heusler compounds YPdBi and TbPdBi, while having similar band structure, exhibit different magnetic properties. YPdBi is a diamagnet, while TbPdBi shows antiferromagnetic order below 5.5 K. Both are superconductors with T${_c}\approx$1 K for YPdBi and T${_c}\approx$1.75 K for TbPdBi. Such a contrast in properties between these two compounds opens a question about the effects of band structure or magnetic correlations on superconductivity. Using the combination of a tunnel diode oscillator (TDO) and a commercial dilution refrigerator, we measured temperature dependent magnetic penetration depth $\Delta\lambda(T)$ in single crystals of YPdBi and TbPdBi, down to temperatures as low as 0.1K. We found that penetration depths of both compounds do not show exponential temperature dependence and saturation at low temperatures, as expected for conventional BCS superconductors. Instead, in both compounds, the penetration depth can be described by a power law $\Delta\lambda(T) = A\times T^{n}$. The coefficient A was found to be about 50$\%$ smaller in TbPdBi, but the exponents are very similar, $n = 2.76\pm 0.04$ in YPdBi and $n = 2.6\pm 0.3$ in TbPdBi, respectively. Our results suggest unconventional superconductivity in both YPdBi and TbPdBi.

Dynamics of traveling pulses developed in a tunnel diode oscillator ring for multiphase oscillation

Herein, we characterize the dynamics of traveling pulses developed in tunnel diode (TD) oscillators that form a closed ring via neighbor-to-neighbor coupling by lossy inductors for multiphase oscillation. It is found that the development of rotary traveling pulses having no sink–source pairs is guaranteed by sufficiently slow application of TD bias voltage. The properties of such rotary pulses are investigated, including the bias dependence of their velocity and their bifurcational structure. Based on these properties, we propose a scheme for multiphase oscillation with a significant number of channels. In addition, this paper describes several experimental observations that validate the numerically obtained properties of rotary traveling pulses.

Penetration depth study of the type-I superconductor PdTe2

Superconductivity in the topological non-trivial Dirac semimetal PdTe2 was recently shown to be type-I. We hereby report measurements of the relative magnetic penetration depth, , on several single crystals using a high precision tunnel diode oscillator technique. The temperature variation follows an exponential function for , consistent with a fully-gapped superconducting state and weak or moderately coupling superconductivity. By fitting the data we extract a -value of ∼500 nm. The normalized superfluid density is in good agreement with the computed curve for a type-I superconductor with nonlocal electrodynamics. Small steps are observed in , which possibly relates to a locally lower due to defects in the single crystalline sample.

15-Gb/s 50-cm Wireless Link Using a High-Power Compact III–V 84-GHz Transmitter

This paper reports on a 15-Gb/s wireless link that employs a high-power resonant tunneling diode (RTD) oscillator as a transmitter (Tx). The fundamental carrier frequency is 84 GHz and the maximum output power is 2 mW without any power amplifier. The reported performance is over a 50-cm link, with simple amplitude shift keying modulation utilized. The 15-Gb/s data link shows correctable bit error rate (BER) of $4.1 \times 10^{-3}$ , while the lower data rates of 10 and 5 Gb/s show a BER of $3.6 \times 10^{-4}$ and $1.0 \times 10^{-6}$ , respectively. These results demonstrate that the RTD Tx is a promising candidate for the next-generation low-cost, compact, ultrahigh data rates wireless communication systems.

AMS SoC Formal Verification based on Hybrid Scheme

This paper proposes for AMS SoC formal verification based on Hybrid Scheme combined with symbolic computing and LHPN model, FV-HS. The paper is concerned with a class of AMS designs, continuous-time AMS designs i.e., tunnel diode oscillator for research target. Firstly, Labeled Hybrid Petri Net model is established for safety property verification of tunnel diode oscillator, then mathematical expression for this model is extracted for efficiency enhancement, and then proof policy built in computer algebra Maple is applied to the corresponding LHPN model for tunnel diode oscillator to verify the property. The proposed method is implemented on tunnel diode oscillator and experiment results demonstrate the advantages of the proposed method over previous method. The proposed method overcomes the drawbacks of LHPN, makes full use of the merits of LHPN and symbolic computing, simplifies the workflow of algorithm and enhances the efficiency.

External Feedback Effect in Terahertz Resonant Tunneling Diode Oscillators

The external feedback effect of a resonant tunneling diode oscillator in terahertz (THz) proximity wireless transmission is modeled and analyzed. The model is based on the circuit modeling of the resonant tunneling diode and the passive structures. We investigate important system parameters such as the reflectivities at the transmitter and the receiver and the power coupling. It is found that the frequency change, the frequency change rate, and the direct-current change are mainly dependent on the reflectivity at the receiver. The received power change is mainly caused by the reflectivity at the transmitter. The simulations agree well with the experimental results. In addition, we demonstrate the high accuracy of our models by clarifying origins of the bit-error-rate change with distance. This demonstrates that the proposed model can be used for the design of a stable THz proximity wireless communication system. The model is also considered to be potentially applicable in other promising THz applications including sensing and radar.

A wide-range variable-frequency resonant tunneling diode oscillator using a variable resonator suitable for simple MEMS process

A resonant tunneling diode oscillator having a wide frequency variation range based on a novel MEMS resonator was proposed, which exploits the change in the signal propagation velocity on a coplanar waveguide according to a movable ground plane. First, we discussed the velocity modulation mechanism, and clarified the importance of the dielectric constant of the substrate. Then, a prototype device oscillating in a 10 to 20 GHz frequency range was fabricated to demonstrate the basic operation. A large and continuous increase in the oscillation frequency of about two times was achieved with this device. This is promising for various applications including THz spectroscopy.

Nodeless superconductivity and time-reversal symmetry breaking in the noncentrosymmetric superconductor Re24Ti5

The noncentrosymmetric superconductor Re$_{24}$Ti$_{5}$, a time-reversal symmetry (TRS) breaking candidate with $T_c = 6$\,K, was studied by means of muon-spin rotation/relaxation ($\mu$SR) and tunnel-diode oscillator (TDO) techniques. At a macroscopic level, its bulk superconductivity was investigated via electrical resistivity, magnetic susceptibility, and heat capacity measurements. The low-temperature penetration depth, superfluid density and electronic heat capacity all evidence an $s$-wave coupling with an enhanced superconducting gap. The spontaneous magnetic fields revealed by zero-field $\mu$SR below $T_c$ indicate a time-reversal symmetry breaking and thus the unconventional nature of superconductivity in Re$_{24}$Ti$_{5}$. The concomitant occurrence of TRS breaking also in the isostructural Re$_6$(Zr,Hf) compounds, hints at its common origin in this superconducting family and that an enhanced spin-orbital coupling does not affect pairing symmetry.

Codesign of Compact III–V Millimeter-Wave Wavelet Transmitters With On-Chip Antennas

Monolithically integrated millimeter-wave wavelet transmitters are presented and analyzed in this paper. Two designs that include compact dielectric resonator antennas with either inductive or self-resonant input characteristics are compared. The efficient transmitter front-end core consists of a resonant tunneling diode oscillator that is quenchable by a transistor switch. A physical diode model is used to formulate small-signal matching criteria and study codesign conditions. Fabricated transmitters provide up to 11-dBm equivalent isotropically radiated power in down to 80-ps wideband wavelets at $V$ -band carrier frequencies. Analyses of the radiated waveform envelope and time-frequency characteristics give insight in the circuit operation.

In situ Investigation of Magnetism in Metastable Phases of Levitated Fe83B17 During Solidification

Understanding transient phases that evolve during solidification can be critical to phase selection and the resulting microstructure of an alloy. However, the nature of high-temperature metastable phases makes them difficult to study with conventional techniques. The authors combine a tunnel-diode oscillator, electrostatic levitator, and x-ray diffraction for contactless precision measurement of magnetic transitions during the freezing of Fe-B, an industrially important material. This technique will prove invaluable for studying high-temperature magnetism in challenging systems.

Magnetic and thermodynamic properties of CuxTiSe2 single crystals

We present a detailed study of the phase diagram of copper intercalated TiSe$_2$ single crystals, combining local Hall-probe magnetometry, tunnel diode oscillator technique (TDO), specific-heat, and angle-resolved photoemission spectroscopy measurements. A series of the Cu$_x$TiSe$_2$ samples from three different sources with various copper content $x$ and superconducting critical temperatures $T_c$ have been investigated. We first show that the vortex penetration mechanism is dominated by geometrical barriers enabling a precise determination of the lower critical field, $H_{c1}$. We then show that the temperature dependence of the superfluid density deduced from magnetic measurements (both $H_{c1}$ and TDO techniques) clearly suggests the existence of a small energy gap in the system, with a coupling strength $2\Delta_s \sim [2.4-2.8]k_BT_c$, regardless of the copper content, in puzzling contradiction with specific heat measurements which can be well described by one single large gap $2\Delta_l \sim [3.7-3.9]k_BT_c$. Finally, our measurements reveal a non-trivial doping dependence of the condensation energy, which remains to be understood.

Response of a resonant tunnelling diode optoelectronic oscillator coupled to a non‐linear electrical circuit

In this study, the authors present a numerical study of the dynamics of a non-linear optoelectronic oscillator (OEO) based on the resonant tunnelling diode (RTD) oscillator incorporating a photo-detector and coupled to a non-linear electrical circuit. In the first part, it is found that the RTD-OEO oscillator presents periodic and quasiperiodic behaviours depending on the values of the parameters of a pulse-like optical signal. In the second part where the RTD-OEO is coupled to the Van der Pol oscillator, the dynamics present a variety of states including bursting, relaxation and sinusoidal oscillations.

Evidence of nodes in the order parameter of the superconducting doped topological insulator NbxBi2Se3 via penetration depth measurements

The low-temperature variation of the London penetration depth $\ensuremath{\lambda}(T)$ in the candidate topological superconductor ${\mathrm{Nb}}_{x}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{3} (x=0.25)$ is reported for several crystals. The measurements were carried out by means of a tunnel-diode oscillator technique in both field orientations (${H}_{\mathrm{rf}}\ensuremath{\parallel}c$ and ${H}_{\mathrm{rf}}\ensuremath{\parallel}ab$ planes). All samples exhibited power-law behavior at low temperatures ($\mathrm{\ensuremath{\Delta}}\ensuremath{\lambda}\ensuremath{\sim}{T}^{2}$) clearly indicating the presence of point nodes in the superconducting order parameter. The results presented here are consistent with a nematic odd-parity spin-triplet ${E}_{u}$ pairing state in ${\mathrm{Nb}}_{x}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$.

Experimental demonstration of strain detection using resonant tunneling delta‐sigma modulation sensors

AbstractA strain sensor was fabricated based on a resonant tunneling diode (RTD) oscillator. This sensor uses strain‐dependent frequency change of the RTD oscillator, and the frequency delta‐sigma modulation technique, which can convert a frequency to a digital signal with wide dynamic range and wide bandwidth. The sensor consists of an oscillator using an LC resonator and an RTD loaded on a beam of the cantilever. The cantilever was fabricated using selective wet etching of the InP substrate. In this sensor, the strain applied to the cantilever changes the current–voltage characteristics of the RTD due to the piezoelectric effect, and hence it changes the oscillation frequency. In this paper, it was demonstrated that the acoustic strain signal can be successfully detected by this sensor with noise shaping behavior, which is a unique nature of the delta‐sigma modulation.

FV-HS: Formal Verification for AMS SoC Based on Symbolic Computing

This paper proposes a novel methodology for AMS SoC formal verification based on Hybrid Scheme combined with symbolic computing and LHPN model, FV-HS. The paper is concerned with a class of AMS designs, continuous-time AMS designs i.e., tunnel diode oscillator for research target. Firstly, Labeled Hybrid Petri Net model is established for safety property verification of tunnel diode oscillator, then mathematical expression for this model is extracted for efficiency enhancement, and then proof policy built in computer algebra Maple is applied to the corresponding LHPN model for tunnel diode oscillator to verify the property. The proposed method is implemented on tunnel diode oscillator and experiment results demonstrate the advantages of the proposed method over previous method. The proposed method overcomes the drawbacks of LHPN, makes full use of the merits of LHPN and symbolic computing, simplifies the workflow of algorithm and enhances the efficiency.

SFV: A Scalable Approach to Formal Verification for AMS SoC

This paper proposes a new scalable approach to formal verification (SFV) for AMS SoC designs. Induction rules defined in computer symbolic algebra system Maple are followed to extract representation of property of AMS SoC, constraints solving is performed to formally verify the correctness of the system with respect to its given property. With an AMS description and a set of properties, SMT based model checker is applied to validate if the given system has a certain properties. The proposed methodology is applied on a tunnel diode oscillator. Experimental results for a benchmark and a tunnel diode oscillator demonstrate the effectiveness of the approach. The proposed method is scalable to other AMS system using language VHDL-AMS as description tool.

Nodeless superconductivity in noncentrosymmetricPbTaSe2single crystals

We report an investigation of the superconducting order parameter of the noncentrosymmetric compound PbTaSe$_2$, which is believed to have a topologically nontrivial band structure. Precise measurements of the London penetration depth $\Delta\lambda(T)$ obtained using a tunnel diode oscillator (TDO) based method show an exponential temperature dependence at $T\ll T_c$, suggesting a nodeless superconducting gap structure. A single band s-wave model well describes the corresponding normalized superfluid density, with a gap magnitude of $\Delta(0)=1.85T_c$. This is very close to the value of $1.76T_c$ for weak-coupling BCS superconductors, indicating conventional fully-gapped superconductivity in PbTaSe$_2$.