GHz Cutoff Frequency Research Articles

A novel FVF-based GHz-range biquad in a 28 nm CMOS FD-SOI technology

Inductor-less CMOS filters with bandwidth exceeding several GHz are required in high-speed data converter applications. This paper introduces two complementary biquad filters, one N-based and the other P-based, utilizing the well-established flipped voltage follower (FVF) stage. These filters exhibit more than 7 GHz cut-off frequency and a low power consumption of 0.54 mW/pole for the N-type biquad, and 0.3 mW/pole for the P-type one, demonstrating impressive figures-of-merit (FOMs) even considering bandwidth and dynamic range. The implementation of these biquads in the STMicroelectronics FD-SOI 28-nm CMOS process, along with extensive simulations, ensures stable performance under process, supply voltage and temperature (PVT) variations and mismatches, as confirmed by post-layout simulations. Notably, the area occupied by each biquad is merely 246 μm2 for N-type biquad and 193 μm2 for P-type, marking one of the smallest footprints in the existing literature. The achieved figures-of-merit are noteworthy, showcasing excellent power efficiency, minimal area occupation, and commendable dynamic range.

Theoretical limit and framework of dynamic modulation in spoof surface plasmon polariton interconnects.

Spoof-surface-plasmon-polariton (SSPP) interconnects are potential candidates for next-generation interconnects to satisfy the growing demand for high-speed, large-volume data transfer in chip-to-chip and inter-chip communication networks. As in any interconnect, the viability and efficiency of the modulation technique employed will play a crucial role in the effective utilization of SSPP interconnects. In light of the lack of a comprehensive platform for the performance analysis of SSPP signal modulation, this work presents a theoretical framework that contributes to the following: 1) predictions of the maximum attainable modulation speed, limited by geometric dispersion in SSPP waveguide, 2) quantification of the fundamental trade-off relation between modulation speed and energy-efficiency for an arbitrary design of SSPP structure, 3) extension of the analysis over a broad category of SSPP modulation technique. In conjunction, a novel SSPP signal modulation technique is introduced, involving controlled alteration of the resonant condition of the SSPP interconnect using a variable resistor. Analyzing a sample SSPP waveguide with a 7 GHz cut-off frequency, the study identifies a potential ∼28% change in its transmission-band by varying the implanted resistor from 5kΩ to 5Ω, a range of values practically attainable with gate-controlled, state-of-the-art submicron scale field-effect transistors. The assertions of the theoretical model have been independently validated by finite-element method based numerical simulations, which show that the underlying concept can be utilized to realize the digital modulation scheme of the amplitude shift keying. For a millimeter-scale SSPP channel having 2.75 GHz transmission bandwidth, up to 300 Mbps modulation speed with nominal power loss is achieved in a standard, thermal-noise limited communication system. By scaling the interconnect to micrometer dimensions, the speed can be augmented up to 10 Gbps for data transfer over 100 mm distance with ≥80% energy efficiency. Essentially, the presented theory is the first of its kind that provides the foundational design guideline for designing and optimizing diverse range of SSPP modulators.

GaN Integrated Circuit Power Amplifiers: Developments and Prospects

GaN integrated circuit technologies have dramatically progressed over the recent years. The prominent feature of GaN high-electron mobility transistors (HEMTs), unparalleled output power densities, has created a paradigm shift in the established and emerging high-power applications. In this article, we present a review on the developments and prospects of GaN integrated circuit power amplifiers (PAs). The progress of GaN transistors including improvements in their important features, i.e., supply voltage, substrate material, transistor scaling approach, and device modeling are elaborated and the current state-of-the-art processes with 20-nm gate length, 450 GHz cut-off frequency, and over 600 V supply voltage are discussed. We also investigate developments in the GaN integrated circuit PA architectures and their implementation challenges including the reactive matching PAs capable of delivering over 100 W output power and operating up to 200 GHz, PA linearity, back-off efficiency enhancement, reconfigurable PAs, and distributed PA architectures. Finally, we discuss the prospects of GaN technology and possible future improvements, in transistor and circuit levels, which can advance performance and functionality of GaN integrated circuits.

Design of Modified Jacobi Microstrip Lowpass Filter for L-Band Application

In this brief, a design of microstrip lowpass filter with the 1 GHz cutoff frequency is revisited, where a class of modified Jacobi polynomials is used for the filter design. The optimization procedure for these filters includes the passband return loss minimization and the roll-off factor enhancement using the magnitude correction of the transmission coefficient. Mentioned correction is performed by introducing the multiple transmission zeros such that LC ladder prototype filter can be realized symmetrically. Three seventh degree filters for L-band applications are realized and simulated: allpole, with a single and double transmission zeros. It is shown that, among these three stepped impedance lowpass filters realizations, the filter with simple transmission zeros offers the best performance.

Design and Performance of Extraordinary Low-Cost Compact Terahertz Imaging System Based on Electronic Components and Paraffin Wax Optics.

Terahertz (THz) imaging is a powerful technique allowing us to explore non-conducting materials or their arrangements such as envelopes, packaging substances, and clothing materials in a nondestructive way. The direct implementation of THz imaging systems relies, on the one hand, on their convenience of use and compactness, minimized optical alignment, and low power consumption; on the other hand, an important issue remains the system cost and its figure of merit with respect to the image quality and recording parameters. In this paper, we report on the design and performance of an extraordinary low-cost THz imaging system relying on a InP Gunn diode emitter, paraffin wax optics, and commercially available GaAs high-electron-mobility transistors (HEMTs) with a gate length of 200 nm as the sensing elements in a room temperature environment. The design and imaging performance of the system at 94 GHz is presented, and the spatial resolution in the range of the illumination wavelength (∼3 mm) and contrast of nearly two orders of magnitude is determined. The operation of two models of the HEMTs of the same nominal 20 GHz cut-off frequency, but placed in different packages and printed circuit board layouts was evaluated at 94 GHz and 0.307 THz. The presence of two competing contributions-self-resistive mixing and radiation coupling through the antenna effects of the printed circuit boards-to the detected signal is revealed by the signal dependence on the gate-to-source voltage, resulting in a cross-sectional responsivity of 27 V/W and noise-equivalent power of 510 pW/Hz at 94 GHz. Further routes in the development of low-cost THz imaging systems in the range of EUR 100 are considered.

A micromachined ultra‐wide stopband lowpass filter based on stepped impedance resonator loaded T‐shaped structure

This article presents an additively manufactured micro-coaxial lowpass filter with ultra-wide stopband suppression. To achieve a wide stopband response, two-stage stepped impedance resonator loaded T-shaped structures are used to substitute the low impedance transmission lines in the lowpass filter prototype to generate extra transmission zeros in the stopband. Shunt open-ended stubs are introduced to the structure in flexible positions to further strengthen the suppression at specific frequency points. The filter is designed with 22 GHz passband and the 20 dB stopband suppression bandwidth over 300 GHz. The micro-coaxial lowpass filter structure was fabricated based on additive metal micro-manufacturing process with the rectangular cross-section dimensions of 0.5 mm × 0.5 mm (300 GHz cutoff frequency). To facilitate the measurement, pair of coax-to-CPW transitions are added at the input/output ports. The measurement results show excellent agreement from DC-110 GHz (limitation of the measurement device), with insertion loss of 1.05 dB at the cutoff frequency fc, which validates the design.

(Invited) Nanoelectronics Based on Assembled High-Density and High-Semiconducting-Purity Carbon Nanotube Films

Carbon nanotubes hold great promise for high-performance electronics but also face significant challenges in terms of assembly and integration. On one hand, aligned carbon nanotubes are proposed as an alternative to III-V semiconductor technologies in radio frequency (RF) applications because of their high linearity as amplifiers and compatibility with CMOS electronics. We will first report high-performance RF transistors with operation frequencies beyond 100 GHz. These devices are built upon high-density (~50 nanotubes / micron) and high semiconducting purity (> 99.99%) aligned single-wall carbon nanotube films assembled at wafer scale. With gate length ~110 nm and T-shaped gate to reduce the gate charging resistance, the devices showed an extrinsic cutoff frequency and maximum oscillation frequency of over 100 GHz. The performance surpasses the 90 GHz cutoff frequency of radio-frequency CMOS transistors with gate length of 100 nm and is close to the performance of GaAs technology. [1] On the other hand, Carbon nanotubes are ideal candidates for beyond-silicon nanoelectronics because of their high mobility and low-cost processing; however, n-type transistors based on assembled aligned nanotubes has not been reported yet. Fabrication of n-type behavior field effect transistors (FETs) based on assembled aligned CNT arrays is needed for advanced CNT electronics. We will report a scalable process to make n-type transistors based on assembled aligned CNT arrays. Air-stable and high-performance n-type CNT FETs are achieved with high yield by combining atomic layer deposition dielectric and Ti contacts with gold overcoating, which are stable in air and widely used for III-V semiconductors. We also systematically studied the contribution of metal contacts and atomic layer deposition passivation in determining the transistor polarity. [2] Based on these experimental results, we report the successful demonstration of complementary metal-oxide-semiconductor inverters with good performance, which paves the way to realizing the promising future of carbon nanotube nanoelectronics.[1] “Wafer-scalable, aligned carbon nanotube transistors operating at frequencies of over 100 GHz”, C. Rutherglen, A. A. Kane, P. F. Marsh, T. A. Cain, B. I. Hassan, M. R. AlShareef, C. Zhou and K. Galatsis, Nature Electronics, volume 2, pages 530–539, 2019.[2] “Air-Stable n-Type Transistors based on Assembled Aligned Carbon Nanotube Arrays and Their Application in CMOS Electronics”, Z. Li, K. R. Jinkins, D. Cui, M. Chen, Z. Zhao, M. S. Arnold and C. Zhou, Nano Res. (2021). https://doi.org/10.1007/s12274-021-3567-9.

Numerical model & design of wideband band reject filter with closed loop rectangular resonator

ABSTRACT Numerical model of a wideband band reject filter using closed rectangular loop resonator is presented using transmission lines. The prototype design of wide band reject filter centred at 3 GHz with lower cut-off frequency of 2 GHz and upper cut-off frequency of 4 GHz is fabricate from the optimal values obtained from the numeric model on a substrate (FR4) with a dielectric constant of 4.3, loss tangent of 0.02–0.03 and substrate height of 1.6 mm. For bidirectional operations, the length-to-width ratio of filter is 2:1. The impedance of the transmission line which is connected between input and output ports is taken as double the feed line impedance while the impedance of the other half wavelength is considered as four times the feed line impedance. The design has obtained bandwidth of more than 60%. It is observed that the full wave electromagnetic results are in good agreement with the experimental and numerical results.

Heterogeneous and Monolithic 3D Integration of III-V-Based Radio Frequency Devices on Si CMOS Circuits.

Next-generation wireless communication such as sixth-generation (6G) and beyond is expected to require high-frequency, multifunctionality, and power-efficiency systems. A III-V compound semiconductor is a promising technology for high-frequency applications, and a Si complementary metal-oxide-semiconductor (CMOS) is the never-beaten technology for highly integrated digital circuits. To harness the advantages of these two technologies, monolithic integration of III-V and Si electronics is beneficial, so that there have been everlasting efforts to accomplish the monolithic integration. Considering that the on horizon 6G wireless communication requires faster and more energy-efficient system-on-chip technologies, it is imperative to realize a radio frequency (RF) system in which III-V technology and Si CMOS technology are integrated at a device level. Here we report heterogeneous and monolithic three-dimensional (3D) analog/RF-digital mixed-signal integrated circuits that contain two types of InGaAs high-electron-mobility transistors (HEMTs) designed for high fT and fMAX in the top and Si CMOS mixed-signal circuits consisting of an analog-to-digital converter and digital-to-analog converter in the bottom. A high unity current gain cutoff frequency of 448 GHz and unity power gain cutoff frequency of 742 GHz have been achieved by the fT oriented and fMAX oriented InGaAs HEMTs, respectively, without being affected by mixed-signal interference. At the same time, the bottom Si CMOS circuits provide valid signals without any performance degradation by the integration process.

Multi-channel AlGaN/GaN Schottky barrier diodes with a half through-hole

The cutoff frequency of Schottky barrier diode (SBD) depends on its junction capacitance and series resistance. The two-dimensional electron gas (2DEG) at AlGaN/GaN interface has high carrier mobility and carrier concentration. However, AlGaN/GaN heterostructure SBD usually shows a high series resistance because of the thin 2DEG channel. In this work, multiple AlGaN/GaN heterojunctions are vertically stacked for forming multiple parallel 2DEG channels to reduce the series resistance. Multi-channel AlGaN/GaN-based air-bridge structure planar SBDs with a half through-hole are demonstrated. The series resistance of quintuple-channel SBD is only 39.5% of the single-channel SBD's. Moreover, a low capacitance is obtained by the Schottky electrode with a half through-hole structure. The low series resistance and the low capacitance contribute to a 16 GHz cutoff frequency in millimeter-wave band.

High‐Current‐Density Enhancement‐Mode Ultrawide‐Bandgap AlGaN Channel Metal–Insulator–Semiconductor Heterojunction Field‐Effect Transistors with a Threshold Voltage of 5 V

Enhancement‐mode ultrawide‐bandgap Al0.65Ga0.35N/Al0.4Ga0.6N metal–insulator–semiconductor heterojunction field‐effect transistors are demonstrated using fluorine‐plasma treatment for threshold voltage control and Al2O3 as gate dielectric. The device exhibits a threshold voltage of 5 V, a maximum drain current density of 105 mA mm−1, and a transconductance of 19 mS mm−1. In addition, the capability to achieve low off‐state current density at 3–4 × 10−9 mA mm−1, an exceptionally low gate leakage current density of 1.4 × 10−8 mA mm−1 even at a high forward gate bias of VGS = 12 V, and a current on/off ratio >1010 is shown. Small signal measurement shows that the device has a unity current gain cutoff frequency fT of 3.8 GHz and power gain cutoff frequency fmax of 4.5 GHz.

Stepped Impedance 7th order Maximally Flat Low Pass Filter Using Microstrip Line for X-Band Applications

In this paper stepped impedance 7th order maximally flat low pass filter is designed and analyzed for X-band range at 9 GHz cut-off frequency. The filter is printed on Alumni substrate of dielectric constant 9.6 and thickness of 1.6 mm. The obtained attenuation is more than 20 dB. The Advanced Design System (ADS) software is used to design and simulate the proposed low pass filter. In addition, a comparison between filter design using insertion loss method implemented in stubs and stepped impedance is presented and discussed.

Performance Analysis of Normally-on Dual Gate Algan/Gan Hemt

This paper presents the novel normally-on dual gate (DG) AlGaN/GaN high electron mobility transistor. At high frequency, the dual gate structure gives superlative immunity over short channel effects. Multiple 2DEG channel regions in dual gate AlGaN/GaN HEMT improves the transport characteristics, charge control and gives better linearity. The high carrier mobility and electron saturation velocity contribute to the high switching frequency of DG HEMT. The drain characteristics of single gate HEMT and dual gate HEMT are compared and DG HEMT outstands in drain current. The various analog and linearity parameters are investigated for DG HEMT. The performance analysis provides better transconductance, capacitance, cut off frequency, subthreshold slope and on-resistance simulations represents the potential of DG HEMT. The DG HEMT provides 1100 mA/mm ION, 550 mS/mm transconductance and 11 GHz cutoff frequency at Vgs = 2 V. The high drain current, better transconductance and cutoff frequency results in better sensitivity of device.

AlInGaN/GaN HEMTs With High Johnson’s Figure-of-Merit on Low Resistivity Silicon Substrate

This work demonstrates high-performance AlInGaN/AlN/GaN high electron mobility transistors grown on 150 mm p-type low resistivity (resistivity~ 20-100 Ω-cm) silicon substrate with state-of-the-art Johnson's figure-of-merit (JFOM). Current gain cut-off frequency (fT) of 83 GHz and 63 GHz and power gain cut-off frequency (fmax) of 95 GHz and 77 GHz with a three-terminal off-state breakdown voltage of 69 V and 127 V, resulting in a high JFOM of 5.7 THz-V and 8.1 THz-V are achieved on the devices with a gate length of 0.16 μm and gate to drain distance of 2 μm and 4 μm, respectively. The fT and J-FOM are comparable or better than the reported values obtained on high resistivity silicon and SiC substrates for devices with similar gate length. On the other hand, GaN-on-Si HEMT structure on the LR-Si substrate exhibits lower power gain and power added efficiency due to strong capacitive coupling effects. TCAD large signal output power simulation indicates significant improvements in output power by minimizing the defects and free charge carriers in the GaN buffer even in the presence of the parasitic channel conduction and conductive silicon substrate. We further propose a modified equivalent circuit model of the parasitic conduction to take into account the conductivity of the GaN and AlGaN buffer.

RF Power Performance of Sc(Al,Ga)N/GaN HEMTs at Ka-Band

We report the RF power results of Sc(Al,Ga)N/GaN high electron mobility transistors (HEMTs). We show dc, small-signal RF and load-pull performance at 30 GHz with two barrier alloys-a ternary of ScAlN and a quaternary of ScAlGaN. The active layers are grown by molecular beam epitaxy on a GaN-on-SiC template. The Sc(Al,Ga)N HEMTs with 120 nm gate length achieve transconductance >700 mS/mm and >70 GHz cutoff frequency. The quaternary ScAlGaN sample shows reduced current collapse during pulsed I-V and load-pull characterization. The ScAlGaN HEMT delivers 5.77 W/mm output power (VD = 20 V) and 47% power-added efficiency (VD = 15 V) when tuned for maximum power and efficiency, respectively.

Design and fabrication of a low-loss microstrip lowpass-bandpass diplexer for WiMAX applications

This work presents a compact low-pass-bandpass microstrip diplexer with a novel configuration. It consists of a lowpass filter integrated with a bandpass filter via a simple compact junction. The proposed bandpass filter consists of four rectangular patch cells and some thin strips. The step impedance structures, with a radial cell, are applied to achieve a lowpass frequency response. The lowpass channel of the introduced diplexer has 2.64 GHz cut-off frequency, whereas, the bandpass channel center frequency is 3.73 GHz for WiMAX applications and covers the frequencies 3.31 GHz to 4 GHz. In addition to having novel structures, both filters have other advantages in terms of high return loss, low insertion loss and high selectivity. The presented microstrip diplexer has the compact size of 29 mm × 13.8 mm × 0.762 mm, calculated at 2.64 GHz. The obtained insertion losses are 0.20 dB (for the first channel) and 0.25 dB (for the second channel), which make the proposed diplexer suitable for energy harvesting. The stopband properties of both bandpass and lowpass filters are improved by creating several transmission zeros. The comparison results show that the lowest insertion losses, the minimum gap between channels, good return losses, and good isolation are obtained.

MODELING OF A MICROSTRIP FIFTH ORDER LOW PASS FILTER FOR WIMAX APPLICATION

Microstrip filters are used to combine or select microwave frequencies within a specific limit. They have been put to use for systems communicating in the wireless mode in today’s world. Over the past few years, the transmission and reception rates of data have transformed the wireless communication scenario in the world. High-speed communication has a pre-requisite of specialized filters encompassing the specifications for fast transmission of data. To achieve this a new inexpensive low pass fifth-order filter has been designed in this article. The proposed filter has been implemented for 3.2 GHz cut-off frequency suitable for WiMAX applications. There is a close agreement between the simulated and computed S-parameters of the designed filter. The filter has the advantage of low cost, highly reliable, and compact size.

Design of a compact LPF and a miniaturized Wilkinson power divider using aperiodic stubs with harmonic suppression for wireless applications

In this paper a miniaturized low pass filter (LPF) with 2.5 GHz cut-off frequency and a novel compact, harmonics suppressed Wilkinson power divider (WPD) at 0.7 GHz is proposed. The proposed divider consists of two multi-stub LPFs and three open stubs at each port. The presented open stub at port one suppresses the second harmonic and other two open stubs at output ports, suppress the third harmonic. To suppress high order harmonics a novel 12 sections LPF based on aperiodic stub is proposed. This filter is designed to suppressed 4th to 15th harmonics. The cut off frequency of applied filter is 2.5 GHz, which creates 12 transmission zeros and suppresses corresponding 4th–15th harmonics of the proposed divider. The proposed WPD not only has perfect harmonics suppression, but also extremely decreases the circuit size. The overall size of the fabricated divider is only 0.116 λg × 0.044 λg, which shows more than 73% size reductions, compared to the 0.7 GHz conventional WPD.

Wafer-scalable, aligned carbon nanotube transistors operating at frequencies of over 100 GHz

Wireless device technology operating in the millimetre-wave regime (30 to 300 GHz) increasingly needs to offer both high performance and a high level of integration with complementary metal–oxide–semiconductor (CMOS) technology. Aligned carbon nanotubes are proposed as an alternative to III–V technologies in such applications because of their highly linear signal amplification and compatibility with CMOS. Here we report the wafer-scalable fabrication of aligned carbon nanotube field-effect transistors operating at gigahertz frequencies. The devices have gate lengths of 110 nm and are capable, in distinct devices, of an extrinsic cutoff frequency and maximum frequency of oscillation of over 100 GHz, which surpasses the 90 GHz cutoff frequency of radio-frequency CMOS devices with gate lengths of 100 nm and is close to the performance of GaAs technology. Our devices also offer good linearity, with distinct devices capable of a peak output third-order intercept point of 26.5 dB when normalized to the 1 dB compression power, and 10.4 dB when normalized to d.c. power. Radio-frequency transistors made from aligned carbon nanotubes offer high linearity and an extrinsic cutoff frequency of over 100 GHz.

Design and simulation of tunable low-pass Gm-C filter with 1 GHz cutoff frequency based on CMOS inventers for high speed telecommunication applications

A tunable low-pass Gm-C filter with 1 GHz cutoff frequency is presented. The core of this filter is a high frequency low voltage operational transconductance amplifier (OTA) in which CMOS inverters...