Millimeter-wave Circuits Research Articles

Compact low‐loss millimeter‐wave shielded asymmetrical coplanar stripline to unilateral and antipodal finline transitions

Compact and low-loss U-band shielded asymmetrical coplanar stripline (SACPS) to unilateral and antipodal finline transitions are proposed in this article for millimeter-wave circuits and systems applications. The principles of mode conversion and impedance matching are applied to the proposed transitions. In the SACPS to unilateral finline transition, the SACPS is firstly transformed into the asymmetrical unilateral finline to convert the quasi-TEM mode to the quasi-TE10 mode and then a tapered unilateral finline section is applied to realize impedance matching. For the U-band back-to-back SACPS to unilateral finline transition, the measured return loss is larger than 15 dB and the insertion loss is less than 1.5 dB with a minimum of 0.5 dB. In the SACPS to antipodal finline transition, the SACPS is firstly transformed into the defected ground microstrip (DGM) without changing the characteristic impedance. Then, the DGM is transformed into the asymmetrical antipodal finline to make mode conversion. At last, a tapered antipodal finline section is used for impedance matching. For the U-band back-to-back SACPS to antipodal finline transition, the measured return loss is larger than 12 dB and the insertion loss is less than 1.5 dB with a minimum of 0.3 dB.

The Combination Scattering-Matrix Method and Wave Iterative Computation for CSRR Based Band Pass Filter Analysis

This paper presents the combination scattering-matrix method and wave iterative computation (WIC) for complementary split rings resonator (CSRR) based band pass filter analysis. The WIC is a numerical model for analyzing the electromagnetic problems of microwave and millimeter-wave circuits and systems. The scattering matrices using Redheffer’s star product, composite right-left-handed (CRLH) transmissions line theory, four-terminal network and boundary conditions in electromagnetics are applied to WIC simulation based on graphical user interface of MATLAB. The WIC simulation can be used for designing the CSRR based BPF circuit and illustrating the electromagnetic field in the circuitry layered structure. The results of WIC simulation and the traditional simulation agree well with the theoretical and measured results.

W-band millimeter-wave back-scattering system for high wavenumber turbulence measurements in LHD.

A 90GHz W-band millimeter-wave back-scattering system is designed and installed for measuring electron scale turbulence (k⊥ρs ∼ 40). A metal lens relay antenna is used for in-vessel beam focusing, and a beam diameter of less than 40mm is achieved in the plasma core region. This antenna can be steered at an angle of 159° ± 6°, which almost covers the plasma radius. The estimated size of the scattering volume is ∼105mm at the edge and 135mm at the core, respectively. A 60m corrugated waveguide is used to achieve a low transmission loss of ∼8 dB. A heterodyne detection system for millimeter-wave circuits with probing power modulation can distinguish the scattered signal from background noise.

Optimization of spaceflight millimeter-wave impedance matching networks using laser trimming

AbstractRealizing packaged state-of-the-art performance of monolithic microwave integrated circuits (MMICs) operating at millimeter wavelengths presents significant challenges in terms of electrical interface circuitry and physical construction. For instance, even with the aid of modern electromagnetic simulation tools, modeling the interaction between the MMIC and its package embedding circuit can lack the necessary precision to achieve optimum device performance. Physical implementation also introduces inaccuracies and requires iterative interface component substitution that can produce variable results, is invasive and risks damaging the MMIC. This paper describes a novel method for in situ optimization of packaged millimeter-wave devices using a pulsed ultraviolet laser to remove pre-selected areas of interface circuit metallization. The method was successfully demonstrated through the optimization of a 183 GHz low noise amplifier destined for use on the MetOp-SG meteorological satellite series. An improvement in amplifier output return loss from an average of 12.9 dB to 22.7 dB was achieved across an operational frequency range of 175–191 GHz and the improved circuit reproduced. We believe that our in situ tuning technique can be applied more widely to planar millimeter-wave interface circuits that are critical in achieving optimum device performance.

A SiGe Power Amplifier With Double Gain Peaks Based on the Control of Stationary Points of Impedance Transformation

A broadband SiGe power amplifier (PA) with double gain peaks for 5G applications is presented. The differential structure is widely adopted in millimeter-wave circuit design to decrease the impact of the source parasitic inductance that is induced by the bonding wires. Since differential PA results in a higher impedance transformation ratio of the matching network, differential PAs generally have narrower bandwidth than single-ended PAs. Through the bandwidth analysis of the matching network, the transformer used for interstage matching is elaborately designed to ease gain fluctuations. By controlling the stationary points of impedance transformation, the maximum available gain characteristic of a transistor, which decreases with increasing frequency, can be compensated. The gain curve of PA, thus, has double gain peaks within operational frequencies to make its frequency responses as flat as possible. The proposed PA for the frequency band from 27 to 37 GHz is fabricated in a standard 130-nm SiGe BiCMOS process, which occupies 0.36 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Under the 2.5-V voltage supply, the SiGe PA exhibited a power gain of 33.5 dB and output power of 21.3 dBm with 24% power-added efficiency at 31 GHz. It achieves a 34% 3-dB small-signal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> bandwidth from 27.3 to 38.5 GHz.

A Ka-band pattern-reconfigurable microstrip antenna enabled by PIN diodes with accurate extraction of equivalent circuit parameters

A Ka-band microstrip antenna based on PIN diodes with accurate extraction of equivalent circuit parameters for pattern reconfigurability is proposed in this work. With the increase in operation frequency, the parasitic effect introduced by PIN diodes has tremendous influence on the performance of reconfigurable antennas; hence, the conventional equivalent circuit parameters of the PIN diodes are not applicable for higher-frequency applications, such as millimeter-wave circuits and antennas. Therefore, accurate equivalent circuit models of the conventional PIN diodes are essential in the millimeter-wave reconfigurable antenna design. Based on the combination of simulation and experimental results, accurate equivalent circuit model parameters for the millimeter-wave range of the PIN diode are extracted, with a pattern-reconfigurable antenna being developed afterwards. The proposed antenna consists of two PIN diodes, two interdigital capacitors, an L-shaped slot, and their bias networks. Particularly, the interdigital capacitors are utilized to isolate direct current (DC) from radio frequency circuits, which is able to improve the economic efficiency of the antenna notably as compared with conventional chip capacitors in the Ka-band. By combining a suitable arrangement of the diodes’ location and the DC bias networks, the main beam direction of the proposed antenna can be switched between −60° and 60°. To demonstrate the proposed idea, a prototype antenna is fabricated and measured. The measured results agree with the simulation quite well, with a good performance around 30 GHz and a gain greater than 5 dBi for both modes being achieved.

Simulations of the Self-Focused Pseudospark-Sourced Electron Beam in a Background Ion Channel

Using pseudospark discharge sourced electron beams for the generation of high-peak-power millimeter and terahertz radiation has attracted increasing research interest in recent years. However, one of the crucially important and hitherto unanswered questions is what is the upper-frequency limit at which millimeter-wave devices can be driven by pseudospark discharge sourced electron beams?. In this paper, we studied this question from the perspective of beam transportation in a plasma background, more specifically an ion channel using particle-in-cell simulations to find the limitations. The parameter ranges of the beam transportation with small oscillations in the beam diameter were investigated and summarized, through simulations of beam propagation in a large diameter drift tube with different ion densities, plasma electron densities, beam density distributions, and beam energies. The beam transportation in a small diameter beam tunnel was also simulated. It showed the maximum beam current with a small velocity spread that can be transported in the beam tunnel was determined by the diameter of the beam tunnel and the ion density. High injected current will cause significant beam loss and reduce the overall efficiency. The simulation results indicate a minimum diameter of the beam tunnel in a millimeter-wave circuit that can be effectively driven by a pseudospark-sourced electron beam. The equivalent upper limit in the operating frequency is about 400 GHz.

Compact Millimeter-Wave SPDT Switches and Wilkinson Power Combiners Implemented by LC-Based Spiral Transmission Lines

This article proposes an LC-based spiral transmission line structure, which can effectively reduce the area of ON-chip transmission lines. The quarter-wavelength transmission line realized by this transmission line structure can be widely used in millimeter-wave circuits design. Based on the LC-based spiral transmission line structure, a 28-GHz single-pole double-throw (SPDT) switch and a 37-GHz Wilkinson power combiner are implemented with an area of only 0.028 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in 65-nm CMOS. Measurement results indicate that the SPDT switch has an insertion loss of less than 1.5 dB and an isolation better than 23.7 dB in the frequency range from 20 to 35 GHz. The insertion loss and the isolation of the Wilkinson power combiner at 36.9 GHz is 0.9 and 30.3 dB, respectively.

Synthesis of mm-Wave Wideband Receivers in 28-nm CMOS Technology for Automotive Radar Applications

A new strategy for millimeter-wave (mm-Wave) circuit and system synthesis, where the accuracy of electromagnetic simulations can be achieved in optimization-based design methodologies without sacrificing efficiency, is presented and tested within a real industrial project. This is done by properly partitioning the system, generating libraries of passive devices which are electromagnetically simulated prior to any circuit optimization, generating performance tradeoffs at different hierarchical levels with multiobjective optimization algorithms and hierarchically composing lower level sub-blocks. With this proposed solution, an entire mm-Wave system, from the passive component level up to the system level, has been designed and compared with the results obtained from a conventional design approach, demonstrating the outstanding capabilities of the methodology.

An efficient transformer modeling approach for mm-wave circuit design

In this paper, a Gaussian-process surrogate modeling methodology is used to accurately and efficiently model transformers, which are still a bottleneck in radio-frequency and millimeter-wave circuit design. The proposed model is useful for a wide range of frequencies from DC up to the millimeter-wave range (over 100 GHz). The technique is statistically validated against full-wave electromagnetic simulations. The efficient model evaluation enables its exploitation in iterative user-driven design approaches, as well as automated design exploration involving thousands of simulations. As experimental results, the model is used in several scenarios, such as the design of an inter-stage amplifier operating at 60 GHz, where the model assisted in the simulation of the transformers and baluns used, and the design of individual transformers and a matching network.

Compact ESD Protection Cell for Multi-Band Millimeter-Wave Applications

A compact electrostatic discharge (ESD) protection cell is proposed for multi-band millimeter-wave (MMW) circuits in nanoscale CMOS technology. The proposed ESD protection cell consists of a silicon-controlled rectifier (SCR) and a diode as the main ESD protection devices, and an inductor in this cell is divided into several sections to resonate at multifrequencies. The proposed design has been demonstrated for 28- and 67-GHz applications. The measurement results show that the proposed design exhibits lower loss at the specified frequency bands, higher ESD robustness, and sufficiently small layout area. Therefore, the novel compact ESD protection cell will be better for multi-band MMW applications in CMOS technology.

A 67-86 GHz Spectrum-Efficient CMOS Transmitter Supporting 1024-QAM With a Process-Variation-Tolerant Design

This paper describes a direct-conversion E-band transmitter (TX) in 65-nm CMOS. To demonstrate the feasibility of E-band 1024-quadrature amplitude modulation (QAM), a 67 to 86 GHz direct-conversion CMOS transmitter with broadband image rejection is presented. The transmitter contains an I (in-phase) and Q (quadrature-phase) modulator and a five-stage power amplifier. To achieve a 40 dBc image-rejection ratio (IRR) of the I/Q modulator for E-band, a broadband half-quadrature generator (HQG), which contains a composite right/left-handed (CRLH) based divider, quadrature couplers, and baluns is proposed. For the purpose of minimizing the phase imbalance, phase balance lines are utilized in HQG to achieve a 1-degree phase accuracy under different tuning lines. Subsequently, the reflection can be mitigated by optimizing the impedance matching between the HQG and the mixer core. Meanwhile, because millimeter-wave (MMW) circuits are susceptible to process variations, a process-variation-tolerant design is introduced to mitigate IRR variation, especially under 40 dBc. The transmitter demonstrates a measured flat conversion gain (CG) of 23±2 dB from 56 to 86 GHz. The proposed TX achieves an IRR better than 40 dBc from 67 to 86 GHz (bandwidth of 19 GHz) with a peak IRR of 56.2 dBc at 70 GHz. Furthermore, the proposed TX has exhibited a 6 bit/s/Hz spectral efficiency with 1024-QAM under the orthogonal frequency-division multiplexing (OFDM) modulation format. The 1.129 mm 2 ~E-band TX achieves a measured output power of 6.5 dBm with a total dc power consumption of 164 mW from a 1.2 V supply voltage.

Analysis and design of transformer-based CMOS ultra-wideband millimeter-wave circuits for wireless applications: a review

With a lot of millimeter-wave (mm-Wave) applications being issued, wideband circuits and systems have attracted much attention because of their strong applicability and versatility. In this paper, four transformer-based ultra-wideband mm-Wave circuits demonstrated in CMOS technologies are reviewed from theoretical analysis, implementation, to performance. First, we introduce a mm-Wave low-noise amplifier with transformer-based Gm-boosting and pole-tuning techniques. It achieves wide operating bandwidth, low noise figure, and good gain performance. Second, we review an injection-current-boosting technique which can significantly increase the locking range of mm-Wave injection-locked frequency triplers. Based on the injection-locked principle, we also discuss an ultra-wideband mm-Wave divider with the transformer-based high-order resonator. Finally, an E-band up-conversion mixer is presented; using the two-path transconductance stage and transformer-based load, it obtains good linearity and a large operating band.

Focus on software, data acquisition, and instrumentation

Focus on software, data acquisition, and instrumentation

Configurable Perforated Air-Filled Substrate Integrated Waveguide (AFSIW) For Generic High-Performance Systems on Substrate

In this article, the patent pending configurable perforated air-filled substrate integrated waveguide (PAFSIW) is presented. First, a theoretical and experimental study of the proposed PAFSIW topology is introduced. Specifically, it is demonstrated that a low-cost Hi- Tg FR4 PAFSIW transmission line can handle over 190 W (up to 1340 W, determined from extrapolation of the experimental results) of continuous wave (CW) power at 20 GHz with an enhanced thermal dissipation compared with its AFISW counterpart. Then, configurable phase shifters, resonators, and filters based on the PAFSIW transmission line sections are introduced. Those components are fabricated using the conventional printed circuit board (PCB) and the through-hole mounting (THM) process to demonstrate the PAFSIW versatility and fabrication-tolerance robustness. The proposed PAFSIW extends the capabilities of the high-performance AFSIW technological platform as it provides genericity, manufacturing process robustness, and an alternative to improve thermal dissipation. The authors expect its implementation in highly configurable microwave- and millimeter-wave circuits for future generic systems on substrate.

Direct Sputtering on PDMS for Investigation of Stretchable and Transparent Microstrip Line

This paper introduces a direct sputtering technology for fabricating flexible and transparent microwave microstrip line. The polydimethylsiloxane (PDMS) is used as the substrate, to realize the characteristics of flexible, stretchable, and transparent microwave circuit, and the solid metallic lines are replaced by the mesh metal. In particular, direct sputtering technology is used on the PDMS substrate to fabricate these transmission lines, which is an efficient candidate for fabrication of microwave or millimeter-wave circuits and is potentially a significant method for multilayer circuits. The fabricated transmission lines with different metallic meshes are measured under conditions of the normal state, 30° inside bending, and 130% stretch, respectively, with acceptable electrical performances up to a frequency of 20 GHz.

Guest Editorial

This Transactions’ Mini-Special Issue contains six expanded papers from the 2018 International Workshop on Integrated Nonlinear Microwave and Millimetre-wave Circuits (INMMiC), Brive-La-Gaillarde, France, July 5–6, 2018. The INMMiC is a forum for promoting, discussing, and spreading ideas in the field of nonlinear microwave and millimeter-wave circuits and systems. The INMMiC Workshop was originally launched in Duisburg, Germany, in 1990, and achieved its present form in Rome, Italy, in 2004. Subsequently, the INMMiC has been held at different venues around Europe, namely, Aveiro, Portugal, in 2006; Málaga, Spain, in 2008; Göteborg, Sweden, in 2010; Vienna, Austria, in 2011; Dublin, Ireland, in 2012; Leuven, Belgium, in 2014; Taormina, Italy, in 2015; and Graz, Austria in 2017. The INMMiC 2018 was held in Brive-La-Gaillarde, France, on July 5–6, 2018.

Optically controlled millimetre‐wave switch with stepped‐impedance lines

A photoconductive grounded coplanar waveguide (GCPW) millimetre-wave switch controlled by a single infrared light-emitting diode is presented. By converting a straight GCPW transmission line into an alternating stepped-impedance line structure, the proposed device shows an on-state insertion loss of <2.9 dB and an off-state isolation of more than 15 dB over a wide-frequency range of 12–30 GHz, with a particularly good radio-frequency performance in the K-band (18–27 GHz). The required optical power and electrical power of the switch are only 199 and 364 mW, respectively. This device also demonstrates an absorptive characteristic with a low reflection coefficient of <−13.5 dB within this frequency range for both the on and off states. In addition, by employing through-holes for illumination of a silicon superstrate, the proposed device can be fabricated with rapid and low-cost laser etching and can be easily integrated with other microwave and millimetre-wave circuits.

Effects of Surface Finish Material on Millimeter-Wave Antenna Performance

Recently, the popularity of millimeter-wave circuits has increased. One of the main reasons for this increase is offering a wide frequency band and high-speed data transfer. Due to the manufacturing requirements, these circuits are covered with surface finishes. Although surface finish protects the exposed copper circuitry, these additive layers on copper foil affect the electrical properties of the conductor. Unlike previous papers in the literature, this paper deals with the effects of surface finishing materials on millimeter-wave antennas instead of transmission lines. With this aim, a differential dual exponentially tapered slot antenna (DETSA) that has almost constant gain, beamwidth, and low reflection coefficient over the entire V-band is designed. A balun is designed for one-port measurement of the differential antenna. Then, two widely used surface finish solutions, namely, electroless nickel immersion gold (ENIG) and immersion silver (IAg), are applied to the copper profile of the differential integrated antenna combined with balun. The structures are simulated with a widely used full-wave analysis tool. The antenna without surface finish, with ENIG, and IAg surface finishes are fabricated and measured. A peak gain of 8.7–9 dBi is measured in the 57–64-GHz ISM band for the antenna without surface finish. Only 0.2-dB decrease in maximum gain is observed with 0.4- $\mu \text{m}$ silver. With ENIG surface finish, the gain decrease is observed as 1 dB. ENIG has higher loss due to flow of current in nickel material having lower conductivity compared to copper. The measurement results are consistent with the numerical results.

A Scalable Model of On-Chip Inductor Including Tunable Dummy Metal Density Factor

Because of the metal density requirement in the advanced CMOS processes, dummy metal fills (DMFs) are unavoidable. The DMFs degrade the performance of the onchip inductors, especially for the ones in the microwave and millimeter-wave circuits. This paper analyzes the impact of the floating DMFs and proposes a scalable double-π inductor model including a tunable dummy metal density factor. The metal density factor can be integrated into the process design kit and determined by the designers to pass the design rule check. The proposed model predicts the decrease in the quality factor (Q) and self-resonance frequency ( fsr) with the density of DMFs increasing accurately. Furthermore, a fully automatic model extraction method based on the genetic algorithm is presented, which increases the accuracy of models. Inductors with DMFs of different densities are fabricated in a standard 180-nm CMOS technology. Then, the parameters of the inductors' models are extracted to verify the idea. The models' calculation results are compared with the measurement results up to 67 GHz.