Tuning Range Voltage Research Articles

Fully epitaxial, monolithic ScAlN/AlGaN/GaN ferroelectric HEMT

In this Letter, we demonstrated fully epitaxial ScAlN/AlGaN/GaN based ferroelectric high electron mobility transistors (HEMTs). Clean and atomically sharp heterostructure interfaces were obtained by utilizing molecular beam epitaxy. The fabricated ferroelectric gate HEMTs showed counterclockwise hysteretic transfer curves with a wide threshold voltage tuning range of 3.8 V, a large ON/OFF ratio of 3 × 107, and reconfigurable output characteristics depending on the poling conditions. The high quality ferroelectric gate stack and effective ferroelectric polarization coupling lead to improved subthreshold performance, with subthreshold swing values approaching 110 and 30 mV/dec under forward and backward gate sweeps, respectively. The results provide fundamental insight into the ferroelectric polarization coupling and threshold tuning processes in ferroelectric nitride heterostructures and are promising for nitride-based nonvolatile, multi-functional, reconfigurable power, and radio frequency devices as well as memory devices and negative capacitance transistors for next-generation electronics.

A 0.14 THz Angular Radial Extended Interaction Oscillator

A 0.14 THz angular radial extended interaction oscillator (AREIO) is proposed in this article. The characteristic impedance (<inline-formula> <tex-math notation="LaTeX">${R}/{Q}$ </tex-math></inline-formula>), the normalized equivalent conductance (<inline-formula> <tex-math notation="LaTeX">${g}_{e}$ </tex-math></inline-formula>), and the starting condition of the cavity are calculated and analyzed. When the metal loss is considered, in order to achieve the starting condition, it is necessary to increase the period length (<inline-formula> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula>) to improve <inline-formula> <tex-math notation="LaTeX">$\vert {g}_{e}\vert $ </tex-math></inline-formula>. The performance of the AREIO is simulated by particle-in-cell (PIC). The voltage tuning range and the output performance under different angular angles of the cavity are investigated. Under the condition of lossless and the electron beam of 11.5 kV and 1.5 A, the peak output power and interaction efficiency of the AREIO (8&#x00B0;) are 5.46 kW and 31.7&#x0025;, which have increased by 24.1&#x0025; and 6.2&#x0025; in comparison with conventional sheet beam. When considering the metal loss, the optimal angular angle will decrease to 4&#x00B0;. In addition, the cavity is fabricated and tested, and the results of <inline-formula> <tex-math notation="LaTeX">${S}_{{11}}$ </tex-math></inline-formula> in operating mode are consistent with the simulation.

Analysis of factors affecting delay accuracy of subfemtosecond liquid crystal variable retarders.

To obtain a wide range of high-precision time-delay controllable devices, a 100-µm-thick nematic liquid crystal (LC) cell was fabricated using the LC HTD028200-200. Factors influencing the delay calibration accuracy of LC variable retarders (LCVRs) were analyzed theoretically and experimentally. Subsequently, within the total voltage tuning range of 0-5 V, the LCVR had a delay of 4.977-97.404 fs, total delay range of 90 fs, tuning accuracy of ±0.216fs, and tuning resolution of 0.128 fs. This device will play an important role in spectral imaging.

Hf0.5Zr0.5O2-Based Ferroelectric Gate HEMTs With Large Threshold Voltage Tuning Range

AlGaN/GaN high-electron-mobility transistors (HEMTs) with Hr0.5 Zr0.5O2 ferroelectric gate stacks exhibiting significant ferroelectric switching for threshold voltage control are experimentally demonstrated. Ferroelectric gate HEMTs (FeHEMTs) with large threshold voltage tuning range of 2.8 V were obtained, with an on/off ratio of $\sim {10}^{{{5}}}$ based on a GaN-channel HEMT structure suitable for RF applications. Improved subthreshold performance has also been achieved compared to conventional MIS-HEMTs, with reduction in average sub-threshold swing (SSavg) by a factor of 2. As a consequence of the significant ferroelectric polarization achieved on AlGaN/GaN heterostructures, Hr0.5 Zr0.5O2 based ferroelectric gate AlGaN/GaN HEMTs appear promising for nonvolatile and reconfigurable RF and microwave applications.

A CMOS based low power digitally controlled oscillator design with MOS varactor

With the shift from traditional analog circuit designs to an all-digital intensive approach, the all-digital Phase-locked loops (ADPLLs) have become more attractive in digital communication systems. Digitally controlled oscillators (DCO) are the key components of the ADPLL circuits. In this paper, a new low power DCO structure is proposed with NMOS transistor as the switching network and utilizing the NMOS varactor as shunt-capacitive loads for the delay cells. The new DCO is capable of producing much higher output frequencies and comprises of components that are fully digital. The proposed DCO structure is designed for three, five and seven stages in CMOS 0.18 µm technology. Variable capacitance is achieved by the use of control word which is applied through NMOS switches conditionally selecting combinations of capacitance and hence determining the delay of the circuit. A 3-stages digitally controlled oscillator shows output frequency variation from 1.986 to 3.526 GHz with a power consumption of 1.484 mW. In the 5-stages DCO, the output frequency varies from 1.154 to 2.210 GHz with a power consumption of 2.762 mW. For 7-stages DCO, the output oscillation frequency is in the range from 0.835 to 1.658 GHz with a power consumption of 4.04 mW. A 3-stages DCO shows a phase noise of − 100.06 dBc/Hz with the offset of 1 MHz with the corresponding figure of merit (FoM) of 165.37 dBc/Hz. Five and seven-stages DCO show phase noise of − 102.08 dBc/Hz and − 105.52 dBc/Hz at 1 MHz respectively. The figure of merit (FoM) for 5 and 7-stages is 160.92 dBc/Hz and 159.07 dBc/Hz respectively. The digital tuning range for 3, 5, and 7-stages DCO is 55.96%, 62.78%, and 66.05% respectively. Further, the results show that the designed DCO has a maximum supply voltage tuning range of 101.45% with the variation of VDD from 1 to 1.8 V. Comparison with earlier reported circuits has been made based on output frequency, power consumption, and phase noise.

Fully Printed Flexible Dual-Gate Carbon Nanotube Thin-Film Transistors with Tunable Ambipolar Characteristics for Complementary Logic Circuits

Semiconducting single-wall carbon nanotubes (sSWCNTs) have been widely used as the channel material for high-performance printed flexible thin-film transistors (TFTs). Due to the absorption of moisture and oxygen in air, the printed sSWCNT TFTs generally exhibit p-type characteristics only. In this paper, we report fully printed dual-gate sSWCNT TFTs that exhibit almost symmetric ambipolar characteristics. With the applied control gate voltage varying from -60 to +60 V, a threshold voltage tuning range of 27 V is achieved, allowing the device to be effectively tuned into either predominantly p-type or predominantly n-type. The tunable ambipolar characteristics are found to be very stable over a long period of time (4 months). By integrating two printed dual-gate TFTs biased with different control gate voltages, a complementary metal oxide semiconductor inverter with close to rail-to-rail output voltage swing is demonstrated. The use of a dual-gate structure for achieving n-type printed carbon nanotube TFTs is much more controllable and repeatable compared to other methods such as chemical doping. Our work shows the feasibility of implementing more sophisticated complementary logic circuits using printed flexible carbon nanotube transistors.

A CMOS high-performance inductorless ring VCO with extended monotonic tuning voltage range

A CMOS high-performance inductorless ring VCO with extended monotonic tuning voltage range

Low noise frequency synthesizer with self-calibrated voltage controlled oscillator and accurate AFC algorithm

A low noise phase locked loop (PLL) frequency synthesizer implemented in 65 nm CMOS technology is introduced. A VCO noise reduction method suited for short channel design is proposed to minimize PLL output phase noise. A self-calibrated voltage controlled oscillator is proposed in cooperation with the automatic frequency calibration circuit, whose accurate binary search algorithm helps reduce the VCO tuning curve coverage, which reduces the VCO noise contribution at PLL output phase noise. A low noise, charge pump is also introduced to extend the tuning voltage range of the proposed VCO, which further reduces its phase noise contribution. The frequency synthesizer generates 9.75–11.5 GHz high frequency wide band local oscillator (LO) carriers. Tested 11.5 GHz LO bears a phase noise of−104 dBc/Hz at 1 MHz frequency offset. The total power dissipation of the proposed frequency synthesizer is 48 mW. The area of the proposed frequency synthesizer is 0.3 mm2, including bias circuits and buffers.

Design of a CMOS multi-mode GNSS receiver VCO

A voltage-controlled oscillator (VCO) with dual stages of accumulation mode varactors for a multi-mode global navigation satellite system (GNSS) application, which adopts sigma-delta fractional-N technology in the synthesizer, is presented. The structure is selected to optimize the frequency coverage and tuning linearity, based on a general analysis of the parasitic capacitance in the coarse tuning switch bank cells, which cover the global positioning system (GPS) and Beidou (BD) bands. The VCO implemented in the 0.18 μm CMOS process can cover the GPS L1, BD B1, B2 and B3 bands with sufficient margin, and exhibits low phase noise by using this tuning curve linearization technique. The equalized Kvco characteristic behavior further offers a wide voltage tuning range and improves the stability of the closed loop.

A CMOS Quadrature VCO With Subharmonic and Injection-Locked Techniques

A 1-V quadrature voltage-controlled oscillator (QVCO) using subharmonic and injection-locked techniques (SHIL-QVCO) is presented. Instead of using the traditional transformer-coupling LC tank with a large area to implement the quadrature output, we use a frequency-doubled differential pair with an injection-locked method. The proposed QVCO is implemented with a TSMC 0.18- μm 1P6M CMOS process having a 1.4 × 0.67 × mm2 chip area. This QVCO has the advantages of low phase noise and low power consumption. Experimental results show that the QVCO has a phase noise of - 126 dBc/Hz at an offset frequency of 1 MHz and a power consumption of 4.9 mW to achieve a 186 figure of merit. Moreover, a tuning frequency between 2.17 and 2.52 GHz can be obtained with a tuning voltage range of 0-1 V for the IEEE 802.15.4.

A technique to improve the linearization of frequency–voltage characteristic of LC-VCO

This paper presents a very low-power linearization technique to improve the linearity of frequency-voltage characteristic of LC-VCO (voltage controlled oscillator) using MOS varactor. This reduces the VCO gain (K VCO) variation and its required value over the tuning voltage range. Low K VCO improves noise and reference spur performances at the output of phase lock loop/frequency synthesizer (FS). Low K VCO variation reduces FS loop stability problem. Using this VCO circuit, a fully on-chip integer-N frequency synthesizer has been fabricated in 0.18 μm epi-digital CMOS technology for 2.45 GHz ZigBee application. The measured VCO phase noise is ?115.76 and ?125.23 dBc/Hz at 1 and 3 MHz offset frequencies, respectively from 2.445 GHz carrier and the reference spur of the frequency synthesizer is ?68.62 dBc. The used supply voltage is 1.5 V.

An wide-range tunable on-chip radio-frequency LC-tank formed with a post-CMOS-compatible MEMS fabrication technique

An on-chip-micromachined tunable LC-tank, which consists of a metal inter-digitated variable capacitor and a metal solenoid inductor, is developed for wide-range radio-frequency (RF) tuning in multi-GHz band. A low-temperature metal MEMS process is developed to on-chip fabricate the passives. The process can be used for post-CMOS-compatible integration with RF ICs. Both the varactor and the inductor are suspended with a gap from the low-resistivity silicon wafer (i.e. standard CMOS wafer) for effectively depressing RF loss. The fabricated variable capacitor part, the inductor part and the whole tunable LC resonator are sequentially tested, finally resulting in a wide resonance-frequency tuning range of 72% (between about 3.5 and 6.0GHz) under a low tuning voltage range of 0–4V, while the Q-factor ranged within 23 and 8.

High-Performance 76-GHz Planar Gunn VCO

A 76-GHz Gunn voltage-controlled oscillator (VCO) with a high output power and a wide tuning-frequency range was fabricated by optimizing VCO circuits and using laser micromachining. The tuning-frequency range of the fabricated Gunn VCO was more than two times higher than that attained in our previous experiments by optimizing VCO circuits. The VCO attained a tuning-frequency range of 493MHz, out-put power variation of 1.0dB, and tuning-frequency linearity of 6.1% over a tuning-voltage range from 0 to 10V. Its power consumption was 2.0W at operation voltage of 3.6V. And it measured out-put power was 13.3dBm with DC-RF conversion efficiency of 1.0% at 76.5GHz. Moreover, under fundamental-mode operation, it achieved low phase noise of -107.8dBc/Hz at an offset frequency of 1MHz. Since laser micromachining was used in fabricating the Gunn VCO, the reproducibility of its RF performance was improved.

Application of the 1-D silicon limit to varactors

Solid-state varactor performance is evaluated in light of fundamental tradeoffs imposed by semiconductor material. This leads to the important conclusion that the product of Q factor, frequency, tuning range, and breakdown voltage has an upper limit (between 5 and 40 THzmiddotV for silicon) that is dictated primarily by semiconductor material parameters, and to a lesser degree on doping level and temperature. This limit is then approached by experimental hyperabrupt profiles with a product of 17 THzmiddotV that were fabricated in a SiGe BiCMOS process. Two complementary analysis techniques based on LCR and high-frequency measurements are presented

Q-factor characterization of RF GaN-based metal-semiconductor-metal planar interdigitated varactor

We report the characterization of quality (Q)-factor of RF metal-semiconductor-metal (MSM) planar interdigitated varactors fabricated by standard AlGaN/GaN HEMT process. The MSM varactors have wide tuning range and exhibit high quality-factor at both the maximum and minimum capacitance values. The fundamental limitation of the Q-factor in the medium capacitance range is also revealed. The elimination of ohmic contact resistance in the MSM varactor configuration pushed up the peak Q-factor to 92 at 0.5 GHz and 41 at 1.1 GHz. The operation of the MSM varactor is modeled by a physical equivalent circuit, with which the dependence of the Q-factor over the entire tuning voltage range can be explained.

Improved independent gate N-type FinFET fabrication and characterization

N-type independent gate FinFETs (IGFinFETs) have been fabricated and characterized. Previous published results for this structure highlighted processing deficiencies. Several process enhancements have improved device results beyond those previously reported. These process improvements are presented, and the resulting device is demonstrated. Device results for 2 micron channel length devices are shown. Six decades of drain current suppression and low gate leakage currents are achieved. Subthreshold slope of 200 mV/dec and a threshold voltage tuning range of 1.7 V are demonstrated. This device combines the behavioral characteristics of independent-double-gate MOSFETs with the processing advantages and integration of FinFETs.

An abundance of sinusoidal RC oscillators

It is assumed that a sinusoidal RC oscillator consists of a linear, passive or active RC network and an amplifier. The properties of such an oscillator are primarily dependent on its open-loop voltage transfer function. A general form of this function is introduced for RC oscillators of the second order, and expressions for the required maintenance gain and the oscillation frequency are derived. It is shown that there exist four distinct types of 2nd-order oscillators. A set of basic building elements for the oscillators is proposed. This consists of some simple RC networks, a voltage divider, a buffer and two amplifiers. The theory and the building elements are used to develop 18 novel oscillator circuits. All these oscillators have either two earthed tuning capacitances or two earthed resistances. It is shown that six of them can be tuned by varying only one capacitance or resistance. Eight of the oscillators are tunable by varying a voltage parameter; in four of these, the voltage-tuning range can be very wide. 14 additional 2nd-order oscillators are suggested. A general 3rd-order RC oscillator is also considered, and it is shown that there exist 15 distinct kinds of this oscillator. The procedure used in the development of the 2nd-order oscillators can also be applied to the design of those of the third order. It is thought that this will lead to a very large number of different oscillator circuits.

A High Power C.W. Travelling-wave Tube†

ABSTRACT This paper describes a ‘ clover loaf ’ C.W. travelling-wave amplifier with a power output of the order of 5 kw over a voltage tuning range of about 5% in the 3 cm band. The tube is designed to operate with its collector at a negative potential, thus enhancing its efficiency, and the application of this technique to high power tubes is discussed in some detail.

Backward-wave oscillators for the 17 to 41 KMC band

Two ĸ-band backward-wave oscillators developed for the Evans Signal Laboratory will be described. The specified frequency range of the one oscillator is 17 to 27 kmc, while that of the other is 26.5 to 41 kmc. The circuit element employed in each case is a unifilar tape helix designed to operate over the desired frequency band within a voltage tuning range of approximately 500 to 2000 volts. The appropriate standard rectangular waveguide and flange is used for the rf output connector. The power output of the lower frequency tube ranges from about 20 to 100 milliwatts while for the higher frequency tube it varies from approximately 4 to 10 milliwatts.