Millimeter-wave Circuits Research Articles

Low-loss W-band CPW bandpass filter using annular CPW branch-line coupler with open load stubs

A W-band coplanar waveguide (CPW) low-loss annular branch-line bandpass filter for planar integrated millimeter-wave circuits is presented. It is designed by using the annular branch-line coupler as a transversal filtering section by loading the coupled ports of the coupler with suitable open load stubs and taking the isolated port as the output node. The proposed W-band bandpass filter shows very good performance, insertion-loss of 0.7 dB with a 14.9% of 3 dB relative bandwidth at center frequency of 94 GHz and return loss is better than −27 dB at the center frequency. The designed and fabricated bandpass filter exhibits the good performance for monolithic integrated millimeter-wave circuit applications. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2400–2403, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26264

Modeling of Current-Return-Path Effect on Single-Ended Inductor in Millimeter-Wave Regime

The effect of current return path (CRP) on the accurate modeling of single-ended inductors in the millimeter-wave regime has been investigated. A series of spiral inductors with different sizes, shapes, and CRP positions was fabricated in a 0.18-μm RF-CMOS process and measured up to 50 GHz. An analytical appended model for CRP is developed to characterize the effect, and its equivalent circuit is validated by measurement results. The proposed model can help millimeter-wave circuit designers to devise layout routing flexibly with high accuracy.

Workshop on Integrated Nonlinear Mirowave and Millimeter-Wave Circuits

Workshop on Integrated Nonlinear Mirowave and Millimeter-Wave Circuits

Millimeter-Wave Passives in 45-nm Digital CMOS

With dramatically increased f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> , CMOS technologies have been widely applied in the design of millimeterwave circuits. To reduce the fabrication cost, digital CMOS processes may be used. Due to the lack of thick top metal and the reduced distance between the top metal and silicon substrates in a digital CMOS, the design of high-performance passives becomes very challenging, particularly in the millimeter-wave frequency regime. In this letter, passives with novel structures were fabricated in a 45-nm digital CMOS process. These passives, including transmission lines, spiral inductors, and metal-oxide-metal (MOM) capacitors, were designed and characterized up to 110 GHz. Their performance was compared with those fabricated using 180- and 90-nm RF CMOS processes. These passives achieved good performance in the millimeter-wave regime. A MOM capacitor has a self-resonant frequency higher than 110 GHz. An inductor achieves a quality factor of 24 at 70 GHz. These results show the feasibility of implementing the millimeterwave passives and systems in a 45-nm digital CMOS process.

High‐performance W‐band MMIC mixer module using GaAs metamorphic HEMT

AbstractIn this letter, we report on a high‐performance 94‐GHz millimeter‐wave monolithic integrated circuit (MMIC) mixer module using 0.1‐μm metamorphic high electron mobility transistors. A modified resistive mixer with a RF amplifier was proposed in this work for low conversion loss and high LO‐RF isolation. The MMIC mixer module was fabricated using a MMIC chip and CPW‐waveguide transitions. The fabricated mixer chip and module showed a low conversion loss of 6.3 and 9.5 dB, and LO‐RF isolations of 24.8 and 30.4 dB at 94 GHz, respectively. This results are superior to those of previously W‐band (75–110 GHz) MMIC mixers. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:815–817, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25081

Broadband transition between rectangular waveguide and substrate integrated waveguide

A novel broadband waveguide-to-substrate integrated waveguide transition is presented. The transition is realised by using a fin line probe inserted into a rectangular metal waveguide. A single back-to-back transition covering the KA band is designed, fabricated and tested. Measured results show that good agreement with simulation, an insertion loss less than 1.4 dB and a return loss better than 15 dB at 25–40 GHz are obtained for a back-to-back structure. This broadband transition between the rectangular waveguide and substrate integrated waveguide can be used widely in microwave and millimetre-wave circuits and systems.

On-Chip Coupled Transmission Line Modeling for Millimeter-Wave Applications Using Four-Port Measurements

Transmission lines are fundamental elements in millimeter-wave circuits. In this paper, on-chip coupled transmission lines, fabricated in a commercial 0.18 ?m complementary metal-oxide semiconductor process, have been modeled, based on measured 50 GHz four-port scattering-parameters. The two-port open-short deembedding technique and thru deembedding method were successfully extended and applied to the four-port structures presented here. The accuracy of the deembedding techniques was verified by full-wave electromagnetic simulation. Based on the deembedded S-parameters, a SPICE-compatible equivalent circuit model of on-chip coupled transmission lines was extracted. Simulation and measurement results agree well over the entire frequency band from 100 MHz up to 50 GHz.

Oversized microstrip line as differential guided-wave structure

An oversized microstrip line as a differential guided-wave structure is proposed. For most guided-wave structures such as microstrip line and waveguide, the signal transmission will be in the form of fundamental mode propagation, where higher-order mode propagations should be avoided. In this reported work, the first higher-order propagation mode (TE10) of a microstrip line is excited. Its guide-wave characteristic was simulated and measured. The oversized microstrip line supporting TE10 propagation mode is proposed for the microwave and millimetre-wave differential circuit and system designs.

A Ka-band low-noise amplifier with a coplanar waveguide (CPW) structure with 0.15-μm GaAs pHEMT technology

This investigation explores a low-noise amplifier (LNA) with a coplanar waveguide (CPW) structure, in which a two-stage amplifier is associated with a cascade schematic circuit, implemented in 0.15-μm GaAs pseudomorphic high electron mobility transistor (pHEMT) technology in a Ka-band (26.5–40.0 GHz) microwave monolithic integrated circuit (MMIC). The experimental results demonstrate that the proposed LNA has a peak gain of 12.53 dB at 30 GHz and a minimum noise figure of 3.3 dB at 29.5 GHz, when biased at a Vds of 2 V and a Vgs of −0.6 V with a drain current of 16 mA in the circuit. The results show that the millimeter-wave LNA with coplanar waveguide structure has a higher gain and wider bandwidth than a conventional circuit. Finally, the overall LNA characterization exhibits high gain and low noise, indicating that the LNA has a compact circuit and favorable RF characteristics. The strong RF character exhibited by the LNA circuit can be used in millimeter-wave circuit applications.

High speeds in a single chip

This article reviews the development and breakthrough of SiGe technologies. SiGe HBTs with transit frequencies ft and maximum oscillation frequencies fmax above 300 GHz and monolithic integrated millimeter-wave circuits based on these HBTs have been developed by several groups. As this paper shows in the overview, the combination of active devices with passive planar structures, including antenna elements, allows single-chip realizations of complete millimeter-wave front-ends.

Nanoscale CMOS Transceiver Design in the 90–170-GHz Range

This paper reviews recent research conducted at the University of Toronto on the development of CMOS transceivers aimed at operation in the 90-170-GHz range. Unique nanoscale CMOS issues related to millimeter-wave circuit design in the 65-nm node and beyond are addressed with an emphasis on transistor and top-level layout issues, low-voltage circuit topologies, and design flow. A Doppler transceiver and two receivers fabricated in a 65-nm GPLP CMOS technology are described, along with a single pole, double throw antenna switch with better than 5-dB insertion loss and 25-dB isolation in the entire 110-170-GHz band. The first receiver has an IQ architecture with a fundamental frequency voltage-controlled oscillator, and is intended for wideband passive imaging applications at 100 GHz. The measured noise figure and downconversion gain are 7-8 and 10.5 dB, respectively, while the 3-dB bandwidth extends from 85 to 100 GHz. The second receiver has double-sideband architecture, operates in the 135-145-GHz range (the highest for CMOS receivers), and features an 8-dB gain LNA, a double-balanced Gilbert cell mixer, and a dipole antenna. The 90-94-GHz Doppler transceiver, the highest frequency reported to date in CMOS, is intended for the remote monitoring of respiratory functions. A Doppler shift of 30 Hz, produced by a slow-moving (4.8 cm/s) target located at a distance of 1 m, was measured with a transmitter output power of approximately + 2 dBm and a phase noise of -90 dBc/Hz at 1 MHz offset. The range correlation effect is demonstrated for the first time in CMOS by measuring the phase noise of the received baseband signal at 10-Hz offset, clearly indicating that 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise has been canceled and it does not pose a problem in short-range applications, where neither a phase-locked loop nor a frequency divider are needed.

InP DHBT Process in Transferred-Substrate Technology With $f_{t}$ and $f_{\max}$ Over 400 GHz

In this paper, a double heterojunction bipolar transistor (DHBT) process has been developed in transferred-substrate (TS) technology to optimize high-frequency performance. It provides an aligned lithographic access to frontside and backside of the device to eliminate dominant transistor parasitics. The transistors of 0.8 times 5-mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> emitter mesa feature f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> = 410 GHz and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> = 480 GHz at a BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ceo</sub> = 5.5 V. Parallel to the device setup, a multilevel metallization scheme is established. It serves as construction kit for 3-D configurations of active and passive elements. High yield of the TS DHBTs, consistent large-signal modeling, and accurate simulation of complex passive elements have been demonstrated and have proved the availability of the technology for advanced millimeter-wave circuit design.

Development of a 60-GHz Bandpass Filter and a Dipole Antenna Using Wafer Transfer Technology

The development of a low-insertion-loss bandpass filter and a dipole antenna using wafer transfer technology (WTT) for 60-GHz band applications is presented for the first time. The WTT process provides a much higher fabrication accuracy than the traditional printed circuit board/thick-film process. In addition, the WTT also provides a new way to transfer millimeter-wave circuits from the high-loss Si substrate to low-loss microwave substrates like the Rogers RT/Duroid 5880. The bandpass filter has a measured 3-dB bandwidth of 12 GHz, and the measured minimum insertion loss is 1.8 dB. The dipole antenna has shown a measured frequency bandwidth from 56 to 61.5 GHz for |S11| less than -10 dB and a measured gain of 5.1 dB at 60 GHz. Compared with the integrated bandpass filter and antennas on CMOS, the WTT shows to be very promising for 60-GHz applications.

50 GHz S-shaped rat-race balun with 1.4 dB insertion loss in a wafer-level chip-size package process

In millimeter-wave CMOS circuits, a balun is useful for connecting off-chip single-end devices and on-chip differential circuits to improve noise immunity. However, an on-chip balun occupies a large chip area. To reduce the chip area required for the on-chip balun, a new rat-race balun using a rewiring technology with a wafer-level chip-size package (W-CSP) is proposed. The W-CSP balun occupies no area in a die because it is placed over integrated circuits. In the proposed balun, an S-shaped structure is adopted in order to directly connect the balun to differential GSGSG pads on a chip with a small area. The S-shaped W-CSP balun was fabricated on a silicon-on-insulator (SOI) substrate. The core area of the S-shaped rat-race balun is 480×735 µm, which is 22.4% that of a square rat-race balun. As a result of measurement, we found that the minimum insertion loss is 1.4 dB and the operating frequency ranges from 40 to 61 GHz.

Measuring Return-Loss Resonances to Estimate RF Wall Loss in MM-Wave Coupled-Cavity Circuits

Wall losses in millimeter-wave coupled-cavity circuits are found from return-loss resonance measurements without consideration of resonance coupling conditions. Changes in the circuit resonator length for a fixed coupling geometry can alter the resonator input impedance and the resonance curves for a given resonance mode. Calculations of the unloaded Q's for both overcoupled and undercoupled conditions for a set of resonance curves show that one result of each pair of calculations is near the correct value.

94-GHz Log-Periodic Antenna on GaAs Substrate Using Air-Bridge Structure

We fabricated a compact, 94-GHz log-periodic planar antenna on GaAs substrate. We used millimeter-wave monolithic integrated circuit (MMIC) process technology to fabricate the on-chip antenna. An air-bridge crossover is used to replace the conventional bonded structure for crisscross connection, which is compatible with active devices and circuits. The fabricated antenna chip size is 1.2 times 2.6 mm2 . Measurement results show that this antenna can operate from 87 to 99.5 GHz with its return loss better than -10 dB. At 94 GHz, the log-periodic antenna has a return loss of -11 dB and 4.8 dBi of gain.

Recent Advances in Millimeter-Wave NRD-Guide Circuits

Though millimeter wave applications have attracted much attention in recent years, they have not yet been put to practical use. The major reason for the failure may be a large transmission loss peculiar to the short wavelength. In order to overcome the inconvenience, it may be promising to introduce the technology of millimeter-wave NRD-guide circuits. In this technology, not only NRD-guide but also Gunn diodes and Schottky diodes play the important role in high bit-rate millimeter-wave applications. A variety of practical millimeter wave wireless systems have been proposed and fabricated. Performances and applications of them are discussed in detail as well.

Planar Surface-Wave Sources and Metallic Grating Lenses for Controlled Guided-Wave Propagation

Guided surface-waves (SWs) on planar substrates are generally an adverse effect that can degrade the performance of monolithic integrated circuits and antenna arrays. However, with appropriate boundary conditions, such SWs can be harnessed as an efficient means of power transport achieving bound propagation along a dielectric slab. Furthermore, by the addition of planar metallic grating configurations an effective dielectric constant can be achieved, refracting cylindrical SWs transmitted from a central surface-wave launcher (SWL) source. Specifically, two metallic grating lenses are investigated for millimeter-wave frequencies of operation, offering either the convergence or divergence of bound SWs. In addition, design concepts are extended to a novel planar coupler. These metallic grating lenses and directive SWL sources can be useful for new quasi-optical millimeter-wave circuits and planar leaky-wave antennas.

A Distributed Millimeter-Wave Small-Signal HBT Model Based on Electromagnetic Simulation

In this paper, a novel distributed small-signal heterojunction bipolar transistor (HBT) model at millimeter-wave frequencies is proposed. This new approach integrates the electromagnetic (EM) simulation of the outer extrinsic passive part of an HBT, the coupled transmission lines for the fingers, and the Gupta multiport connection into an efficient global distributed modeling approach. For the first time, the values of the entire HBT intrinsic model elements used in the active elementary cells (AECs) can subsequently be extracted through the explicit analytical expressions derived through the multiport connection method. Good agreement between the measured and the simulated results has been demonstrated. This model has several unique advantages for microwave transistor optimization and synthesis in that the derived explicit analytical expressions are in terms of the effect of the extrinsic parts, allowing the designer to have better control over the whole transistor design. Furthermore, it serves as one of the valuable steps toward global modeling of millimeter-wave devices and circuits.

A 40-50-GHz SiGe 1 : 8 differential power divider using shielded broadside-coupled striplines

This paper presents a 1 : 8 differential power divider implemented in a commercial SiGe BiCMOS process using fully shielded broadside-coupled striplines integrated vertically in the silicon interconnect stackup. The 1 : 8 power divider is only 1.12 x1.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> including pads, and shows 0.4-dB rms gain imbalance and <3deg rms phase imbalance from 40 to 50 GHz over all eight channels, a measured power gain of 14.9 plusmn0.6 dB versus a passive divider at 45 GHz, and a 3-dB bandwidth from 37 to 52 GHz. A detailed characterization of the shielded broadside-coupled striplines is presented and agrees well with simulations. These compact lines can be used for a variety of applications in SiGe/CMOS millimeter-wave circuits, including differential signal distribution, miniature power dividers, matching networks, filters, couplers, and baluns.