Negative Resistance Oscillator Research Articles

Effect of Interdiffusion and Crystallization on Threshold Switching Characteristics of Nb/Nb2O5/Pt Memristors.

The resistive switching response of two terminal metal/oxide/metal devices depends on the stoichiometry of the oxide film, and this is commonly controlled by using a reactive metal electrode to reduce the oxide layer. Here, we investigate compositional and structural changes induced in Nb/Nb2O5 bilayers by thermal annealing at temperatures in the range of 573-973 K and its effect on the volatile threshold switching characteristics of Nb/Nb2O5/Pt devices. Changes in the stoichiometry of the Nb and Nb2O5 films are determined by Rutherford backscattering spectrometry and energy-dispersive X-ray (EDX) mapping of sample cross sections, while the structure of the films is determined by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy (TEM). Such analysis shows that the composition of the Nb and Nb2O5 layers is homogenized by interdiffusion at temperatures less than the crystallization temperature (i.e., >773 K) but that this effectively ceases once the films crystallize. This is explained by comparison with the predictions of a simple diffusion model which shows that the compositional changes are dominated by oxygen diffusion in the amorphous oxide, which is much faster than that in the crystalline phases. We further show that these compositional and structural changes have a significant effect on the electroforming and threshold switching characteristics of the devices, the most significant being a marked increase in their reliability and endurance after crystallization of the oxide films. Finally, we examine the effect of annealing on the quasistatic negative differential resistance characteristics and oscillator dynamics of devices and use a lumped element model to show that this is dominated by changes in the device capacitance resulting from interdiffusion.

A negative‐resistance oscillator using dual‐cavity based on SISL technology

AbstractThis article presents a low‐phase noise negative resistance oscillator using the dual‐cavity resonator (DCR) based on substrate integrated suspended line (SISL) technology. Two air cavities are stacked without increasing the footprint areas of the oscillator. A coupling hole is introduced to realize weak coupling between the two air cavities. The DCR can enhance the roll‐off of the equivalent resonator. The measured Q factor of the DCR is increased by 15% compared with the single cavity resonator. The measured phase noise of the designed oscillator is −135.32 dBc/Hz at 1 MHz offset from the carrier frequency of 12.44 GHz, and the measured FOM at 1 MHz offset is −204 dBc/Hz. Besides, the designed oscillator based on SISL technology has the advantages of low cost, compact size, and self‐packaging properties.

Effect of Load Impedance on the Performance of Microwave Negative Resistance Oscillators

In microwave negative resistance oscillators, the RF transistor presents impedance with a negative real part at either of its input or output ports. According to the conventional theory of microwave negative resistance oscillators, in order to sustain oscillation and optimize the output power of the circuit, the magnitude of the negative real part of the input/output impedance should be maximized. This paper discusses the effect of the circuit’s load impedance on the input negative resistance and other oscillator performance characteristics in common base microwave oscillators. New closed-form relations for the optimum load impedance that maximizes the magnitude of the input negative resistance have been derived analytically in terms of the Z-parameters of the RF transistor. Furthermore, nonlinear CAD simulation is carried out to show the deviation of the large-signal optimum load impedance from its small-signal value. It has been shown also that the optimum load impedance for maximum negative input resistance differs considerably from its value required for maximum output power under large-signal conditions. A 1.8 GHz oscillator circuit has been designed and simulated using a typical SiGe hetero-junction bipolar transistor (HBT) to verify the proposed approach of analysis.

A Survey on Switching Oscillations in Power Converters

High-frequency power converters enabled by wide bandgap (WBG) and silicon semiconductor devices offer distinct advantages in power density and dynamic performance. However, switching oscillations are commonly observed in these circuits with undesirable consequences. This paper reviews the impacts, root causes, and mitigation techniques of switching oscillations through literature survey, modeling analysis, and experimental investigation. We categorize the following root causes for oscillations during switching transients: 1) damped oscillation triggered by high di/dt and/or dv/dt coupled with parasitic elements; 2) undamped oscillation of WBG devices as part of a negative resistance oscillator; and 3) semiconductor device physical mechanisms such as the negative capacitance phenomenon due to conductivity modulation in insulated gate bipolar transistors or impact ionization in MOSFETs, the plasma extraction transit-time effect in bipolar power devices, and the reverse conduction property of GaN HEMTs. Furthermore, this paper discusses various circuit techniques to suppress switching oscillations, and techniques of extracting parasitic inductances of power devices.

A SiC BJT-Based Negative Resistance Oscillator for High-Temperature Applications

This brief presents a 59.5 MHz negative resistance oscillator for high-temperature operation. The oscillator employs an in-house 4H-silicon carbide BJT, integrated with the required circuit passives on a low-temperature co-fired ceramic substrate. Measurements show that the oscillator operates from room temperature up to 400 °C. The oscillator delivers an output power of 11.2 dBm into a 50 $\Omega $ load at 25 °C, which decreases to 8.4 dBm at 400 °C. The oscillation frequency varies by 3.3% in the entire temperature range. The oscillator is biased with a collector current of 35 mA from a 12-V supply and has a maximum dc power consumption of 431 mW.

A real-time humidity sensor based on a microwave oscillator with conducting polymer PEDOT:PSS film

In this paper, we propose a humidity sensor based on a negative resistance oscillator using conducting polymer (CP) PEDOT:PSS film at room temperature. The proposed humidity sensor basically consists of a microstrip line and a negative resistance circuit, which creates a negative resistance for high-frequency oscillation. The microstrip line has a circuit structure that is connected through a via hole between the ground plane and the signal line with a CP thin film. From our experimental results, we find that the oscillation frequency of the sensor gradually decreases as the relative humidity (RH) increases. Owing to the conductivity variation of the CP film with the RH value, the oscillation frequency of the sensor sensitively changes in real time. Therefore, we suggest that our microwave-oscillator-based sensor scheme is a good candidate for the design of a robust and stable humidity sensor.

A Phase-Noise Reduced Microwave Oscillator Sensor With Enhanced Limit of Detection Using Active Filter

A microwave planar negative resistance oscillator with higher frequency stability and lower phase noise (PN) is introduced for sensing applications. Split-ring resonator is used as sensing element at 2.4 GHz and is used for microfluidic concentration sensing of high lossy solution of water in ethanol. Stabilizing the frequency response with the use of active filter leads to 14-times enhancement in the limit of detection, from 7% (passive filter) to 0.5% (active filter), while the linearity of the sensor is preserved; the sensing range is then increased. Nearly 13-dBc/Hz improvement in the measured PN, in great agreement with theory, also verifies the frequency domain stability of the oscillator.

Design of Negative Resistance Oscillator with Rocord Low Phase Noise

The aim of this paper is to use a new design of a negative resistance microwave oscillator in order to fabricate oscillator with very good performance in terms of output power, efficiency, stability and phase noise. In this study the new concept of oscillator using distributed resonator and micro-strip circuit elements improve performances of our structure. A micro-strip microwave oscillator with low phase noise based on an NPN silicon planar epitaxial transistor has been designed, fabricated, and characterized. In this design, each step has been conducted by using Advanced Design System (ADS) and following a theoretical study which enable to optimize the different performances of the whole circuit. The oscillator produce a sinusoidal signal with spectrum power of 12.25 dBm at 2.45 GHz into 50 Ω load when polarized at Vcc=15V with DC to RF efficiency of 16. The obtained phase noise of -120 dBc/Hz at 100 Hz offset is the result of the use of high Q factor resonator and the depth study of the parameters of the oscillator. Simulation and measurement results are in good agreement.

Active Integrated Antenna Based Permittivity Sensing Tag

In this article, a novel negative resistance oscillator based active integrated tag antenna design is proposed for sensing material permittivity at a distance from the reader. A microstrip interdigital sensing arm acts as the terminating element of the oscillator. A broadband microstrip monopole tag antenna, working as the load element, is used to transmit the output signal of the oscillator to the reader. The frequency of oscillation varies with the permittivity of the loaded overlay dielectric substrate sample on the interdigital sensing arm. An oscillation frequency variation of 200 MHz (6.8 GHz to 7 GHz) is experimentally observed for change in relative permittivity from 1 (unloaded) to 10.2. The proposed tag is calibrated, and it can measure relative permittivity of 1 to 12 with better than 3.6% accuracy. The permittivity of the loaded material can be calculated by measuring the output signal frequency of the active tag and utilizing frequency positioning algorithm. The phase noise of the stand-alone oscillator is measured to be better than -105 dBc/Hz and -117 dBc/Hz at 500 KHz and 2 MHz frequency offsets, respectively. The design is optimized theoretically and by simulation, and its proof-of-concept working principle is demonstrated experimentally. The proposed active sensor tag provides good reading range of about 600 cm and consumes very low power (6 mW). It has low profile (40 cm x 87 cm), and it is suitable for low cost batch fabrication.

(Invited) Methods for Dynamic Analysis and Stability Assurance of Power Modules with Wide Bandgap Devices

This paper addresses the problems that have been widely reported with the dynamic behavior of application circuits using wide bandgap devices of both common semiconductor types, i.e., silicon carbide and gallium nitride. It is now common to see recommendations to the effect that advanced wide bandgap transistors need advanced packaging to realize reliable operation and expected benefits. This thinking is so prevalent that at least one manufacturer of GaN transistors does not supply their devices in packaging. While this is hardly the view of most manufacturers, it does highlight that wide bandgap transistors have succeeded so well in demonstrating new capabilities in high voltage, high current, and/or high frequency that the design methodology for integrating these devices into power electronics applications needs to be rethought. But what should this thinking be? Since fast switching is an essential part of the value of wide bandgap devices, it is imperative that the designers of high-power modules using these devices have modeling and simulation tools to manage the near RF dynamic behavior of the system in order to preclude instability and to manage electromagnetic emission. Fortunately, the well established rules of stability in electronic circuits should apply, but during analysis of power electronic applications they need to be augmented with model features omitted with silicon power semiconductors. But as a practical matter, the additions to the model need to be as simple as possible while achieving a level of confidence that a power module design containing SiC or GaN transistors integrated with a particular gate drive will perform with assurance of stability and with acceptable dynamics. An example of acceptable dynamics is compliance with electromagnetic interference certification requirements. But what are the means available? The current literature primarily addresses the issue quantitatively with what might be called the finite element method. This involves trying to experimentally measure or estimate through simulation the lumped element parasitics connecting all devices to each other and to drain, source, and gate buses leading to the external contacts of the power package and continuing to the gate drive. These parasitics are usually lumped series inductances and resistances, and shunt capacitances to surfaces of common potential so that common-mode interference can also be understood. This method has been shown to be successful in identifying the impedance-based mode changes from parasitic “ringing” to periodic oscillations. The former is considered to be a relatively unavoidable nuisance that dissipates the energy stored in parasitic components during ­one switching cycle of a commutated power pole. The latter is unacceptable as it converts energy from a main energy supply, such as the DC bus feeding a half-bridge circuit, into recurring oscillations. An impedance based method known as the concept of negative resistance oscillators is shown to be quantitatively successful at predicting the mode change from stable to unstable in a circuit with a single discrete device. But for the case of a multi-chip power package, with much greater complexity in the number of active semiconductor devices and the number of interconnections and shunt paths defining the parasitic degrees of freedom, a more systematic method is needed that is still behavioral in nature to keep the methodology computationally tractable. This paper describes a novel blend of the approaches used by two engineering communities that integrate power devices into application specific packaging. The impedance method of the lumped-element negative resistance oscillator representing the method of the power electronics engineering community is extended to the power package containing wide bandgap devices with the use of the S-parameter approach that dominates the microwave engineering community. A commercial simulation tool, such as ADS by Agilent, is shown to easily extract S-parameters of arbitrary package design using physics based modeling and simulation. The resulting comprehensive description of the parasitic properties of the power package captured by the multi-port S-parameter behavioral model is combined with the channel-modulation model of the transistors to form a negative resistance description of the root cause of poor dynamics and instability. The result is a new approach for specifying acceptable dynamic performance and stability assurance of multi-chip integrated power modules containing wide bandgap semiconductors.

Ku‐band low phase noise oscillator using the high order mode loaded with L‐slot SIW resonator

ABSTRACTThis article introduces a novel high Q‐factor substrate integrated waveguide (SIW) cavity resonator and its application of Ku‐band low phase noise oscillator. Q‐factor of the proposed resonator is improved by using the L‐slot and the higher order mode. The L‐slot is placed on edge of TE102 mode field. Therefore, the L‐slot has little influence on resonant frequency but can obviously enhance roll‐off characteristic of S11. And the high order modes have the bigger Q value than fundamental mode. The negative resistance oscillator based on the proposed SIW cavity resonator is easily designed and tested. The experimental results of Ku‐band oscillator show outstanding low phase noise of −130.43 dBc/Hz at 1 MHz offset frequency from 15.55 GHz carrier frequency. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2325–2328, 2016

Millimeter wave band ultra wideband transmitter MMIC

This paper presents a new millimeter-wave (MMW) ultra wideband (UWB) transmitter MMIC which has been developed in an OMMIC 0.1 μm GaAs PHEMT foundry process (ft = 100 GHz) for 22–29 GHz vehicular radar systems. The transmitter is composed of an MMW negative resistance oscillator (NRO), a power amplifier (PA), and two UWB pulse generators (PGs). In order to convert the UWB pulse signal to MMW frequency and reduce the total power consumption, the MMW NRO is driven by one of the UWB pulse generators and the power amplifier is triggered by another UWB pulse generator. The main advantages of this transmitter are: new design, simple architecture, high-precision distance measurements, infinite ON/OFF switch ratio, and low power consumption. The total power consumption of the transmitter MMIC is 218 mW with a peak output power of 5.5 dBm at 27 GHz.

Instability in Half-Bridge Circuits Switched With Wide Band-Gap Transistors

Wide band-gap (WBG) field-effect devices are known to provide a system-level performance benefit compared to silicon devices when integrated into power electronics applications. However, the near-ideal features of these switching devices can also introduce unexpected behavior in practical systems due to the presence of parasitic elements. The occurrence of self-sustained oscillation is one such behavior that has not received adequate study in the literature. This paper provides an analytical treatment of this phenomenon by casting the switching circuit as an unintentional negative resistance oscillator. This treatment utilizes an established procedure from the oscillator design literature and applies it to the problem of power circuit oscillation. A simulation study is provided to identify the sensitivity of the model to various parameters, and the predictive value of the model is confirmed by experiment involving two exemplary WBG devices: a SiC vertical-channel JFET and a SiC lateral-channel MOSFET. The results of this study suggest that susceptibility to self-sustained oscillation is correlated to the available power density of the device relative to the parasitic elements in the circuit, for which wide band-gap devices, to include SiC and GaN transistors, are in a class approaching that of the radio frequency domain.

Design of MMIC oscillators using GaAs 0.2 μm PHEMT technology

We propose a feedback type oscillator and two negative resistance oscillators. These microwave oscillators have been designed in the S band frequency. A relatively symmetric resonator is used in the feedback type oscillator. The first negative resistance oscillator uses a simple lumped element resonator which is substituted by a microstrip resonator in the second oscillator to improve results. The negative resistance oscillator produces 4.207 dBm and 7.124 dBm output power with the lumped element resonator and microstrip resonator respectively, and the feedback type oscillator produces −10.707 dBm output power. The feedback type oscillator operates at 3 GHz with phase noise levels at −83.30 dBc/Hz and −103.3 dBc/Hz at 100 kHz and 1 MHz offset frequencies respectively. The phase noise levels of the negative resistance oscillator with the lumped element resonator are −94.64 dBc/Hz and −116 dBc/Hz at 100 kHz and 1 MHz offset frequencies respectively, at an oscillation frequency of 3.053 GHz. With the microstrip resonator the phase noise levels are −99.49 dBc/Hz and −119.641 dBc/Hz at 100 kHz and 1 MHz offset frequencies respectively, at an oscillation frequency of 3.072 GHz. The results showed that both the output power and the phase noise of the negative resistance oscillators were better than those of the feedback type oscillator.

Simplified phase noise model for negative-resistance oscillators and a comparison with feedback oscillator models

This paper describes a greatly simplified model for the prediction of phase noise in oscillators which use a negative resistance as the active element. It is based on a simple circuit consisting of the parallel addition of a noise current, a negative admittance/resistance, and a parallel (Qlimited) resonant circuit. The transfer function is calculated as a forward trans-resistance (VOUT/IIN) and then converted to power. The effect of limiting is incorporated by assuming that the phase noise element of the noise floor is kT/2, i.e., -177 dBm/Hz at room temperature. The result is the same as more complex analyses, but enables a simple, clear insight into the operation of oscillators. The phase noise for a given power in the resonator appears to be lower than in feedback oscillators. The reasons for this are explained. Simulation and experimental results are included.

Design of S-Band Oscillators by Using GaAs ED02AH 0.2-μm Technology

The S band limits from 2 to 4 GHz, is part of the electromagnetic spectrum’s microwave band. It is used by radars, satellites and some communications. This paper is concerned with the theory and design of 3 GHz feedback type and negative resistance oscillators by using Aiglent ADS software simulator with GaAs ED02AH 0.2-μm technology, and comparison of their results. A lumped element resonator has used in the design of feedback type oscillator and a negative resistance oscillator has utilized a microstrip resonator. The negative resistance oscillator operates at 3.072 GHz with phase noise levels at -99.49 dBc/Hz and -119.6 dBc/Hz at 100KHz and 1 MHz offset frequencies respectively. The phase noise levels of feedback type oscillator are -83.30 dBc/Hz and -103.3 dBc/Hz at 100KHz and 1 MHz offset at oscillation frequency of 3 GHz. Furthermore, we compared the output power of these oscillators and negative resistance oscillator showed 7.124 dBm, and feedback type oscillator presented -10.707dBm.

A Theory of Single-Event Transient Response in Cross-Coupled Negative Resistance Oscillators

A theory of the circuit-based response to SET phenomena in resonant tank oscillators is presented. Transients are shown to be caused by a change in the voltage state of the circuit's characteristic differential equation. The SET amplitude and phase response is derived for arbitrary strike waveforms and shown to be time-variant based on the strike time relative to the period of oscillation. Measurements in the time-domain are used to support the theory, while the frequency-domain is used to gauge potential impact on system performance. A design-oriented analysis of the relevant trade-offs is also presented.

A 10 GHz high-efficiency and low phase-noise negative-resistance oscillator optimized with a virtual loop model

A virtual loop model was built by the transmission analysis with virtual ground method to assist the negative-resistance oscillator design, providing more perspectives on output power and phase-noise optimization. In this work, the virtual loop described the original circuit successfully and the optimizations were effective. A 10 GHz high-efficiency low phase-noise oscillator utilizing an InGaP/GaAs HBT was achieved. The 10.028 GHz oscillator delivered an output power of over 15 dBm with a phase-noise of lower than –107 dBc/Hz at 100 kHz offset. The efficiency of DC to RF transformation was 35%. The results led to a good oscillator figure of merit of –188 dBc/Hz. The measurement results agreed well with those of the simulations.

20 GHz gated tunnel diode based UWB pulse generator

AbstractWe demonstrate a pulse generator based on a GaAs‐AlGaAs gated resonant tunneling diode (RTD). This is realized by integrating a third terminal, the gate, into the current path of a RTD. The gate consists of a 200 Å thick tungsten grating buried 300 Å above the RTD. This implementation allows for control of the current through the RTD. By integrating this device in parallel with an on‐chip inductance, a negative differential resistance (NDR) oscillator is formed. It is demonstrated that by using the gate to change the output conductance of the device, the oscillations may be switched on and off, creating short bursts of RF power. This technique allows for rapid quenching of the oscillator, and hence the ability to generate short pulses at high frequency, enabling impulse radio ultra‐wideband communication implementations. The highest demonstrated oscillation frequency is 22 GHz with an output power of –4.1 dBm, and the shortest pulses generated are 1.3 ns. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

DESIGN AND ANALYSIS CONSIDERATIONS OF 4-GHZ INTEGRATED ANTENNA WITH NEGATIVE RESISTANCE OSCILLATOR

DESIGN AND ANALYSIS CONSIDERATIONS OF 4-GHZ INTEGRATED ANTENNA WITH NEGATIVE RESISTANCE OSCILLATOR