Enabling Solutions for Integration and Interconnectivity in Millimeter-wave and Terahertz Systems

Recently, Terahertz (THz) systems have witnessed increasing attention due to the continuous need for high data rate transmission which is mainly driven by next-generation telecommunication and imaging systems. In that regard, the THz range emerged as a potential domain suitable for realizing such systems by providing a wide bandwidth capable of achieving and meeting the market requirements. However, the realization of such systems faces many challenges, one of which is interconnectivity and high level of integration. Conventional packaging techniques would not be suitable from performance perspective above 100 GHz and new approaches need to be developed. This thesis proposes and demonstrates several approaches to implement interconnects that operate above 100 GHz. One of the most attractive techniques discussed in this work is to implement on-chip coupling structures and insert the monolithic microwave integrated circuit (MMIC) directly into a waveguide (WG). Such approach provides high level of integration and eliminates the need of galvanic contacts; however, it suffers from a major drawback which isthe propagation of parasitic modes in the circuit cavity if the MMIC is large enough to allow such modes to propagate. To mitigate this problem, this work suggests and investigates the use of electromagnetic bandgap (EBG) structures that suppresses those modes such as bed of nails and mushroom-type EBG structures. The proposed techniques are used to implement several on-chip packaging solutions that have an insertion loss as low as 0.6 dB at D-band (110-170 GHz). Moreover, the solutions are demonstrated in several active systems using various commercial MMIC technologies. The thesis also investigates the possibility of utilizing the commercially available packaging technologies such as Embedded Wafer Level Ball Grid Array (eWLB) packaging. Such technology has been widely used for integrated circuits operating below 100 GHz but was not attempted in the THz range before. This work attempts to push the limits of the technology and proposes novel solutions based on coupling structures implemented in the technology’s redistribution layers. The proposed solutions achieve reasonable performance at D-band that are suitable for low-cost mass production while allowing heterogeneous integration with other technologies as well. This work addresses integration challenges facing systems operating in the THz range and proposes high-performance interconnectivity solutions demonstrated in a wide range of commercial technologies and hence enables such systems to reach their full potential and meet the increasing market demands

Non-galvanic Interconnects for Millimeter-wave Systems

Fueled by the increasing demand for higher data rates, millimeter-wave (mmW) systems emerged as a candidate that can provide multi-gigabit per second (Gb/s) transmission. This demand is mainly driven by modern communication systems and several other wireless and sensing applications such as production quality inspection and imaging systems. The full realization of such systems has been always challenged by the lack of low-loss low-cost interconnects and high-level integration. This challenge is more critical in systems operating beyond 100 GHz where conventional packaging techniques would not be suitable from performance perspective.D-band offers a wide spectrum ranging from 110 to 170 GHz and hence providing wide bandwidth that makes it suitable for high data rate systems. In this thesis, several interconnects that operate at D-band are presented. Different technologies were used to realize the interconnects. Two interconnects are realized in Embedded Wafer Level Ball Grid Array (eWLB) packaging technology. The technology has been widely used for low frequency applications. The proposed interconnects are based on slot antennas radiating to a standard air-filled waveguides. The interconnects achieve an average insertion loss of 3 dB and 3.4 dB across the frequency ranges 110-138 GHz and 116-151 GHz respectively. The proposed interconnects are generic and do not require any galvanic contacts. The utilized eWLB packaging technology is suitable for low-cost high-volume production and allows heterogeneous integration with other technologies as well.A chip-to-waveguide transition based on unilateral finline structure is also demonstrated. The interconnect consists of a microstrip line implemented on a 75 um-thick substrate. The line then couples to a unilateral finline taper that is mounted in the E-plane of a standard D-band waveguide. The transition achieves a very low loss of only 0.7 dB and covers a very wide band ranging from 110 to 170 GHz.A chip-to-waveguide transition in a commercial MMIC technology is also presented. The transition is based on Linearly Tapered Slot antenna (LTSA) structure. The antenna is implemented on a 50 um-thick Gallium Arsenide (GaAs) substrate. The transition exhibits an insertion loss of 1 dB across the frequency range 110-170 GHz. This work presents low-cost high-performance mmW interconnects and addresses integration challenges facing systems operating beyond 100 GHz paving the way for high-volume commercialization of such systems in the future

G-band Frequency Converters in 130-nm InP DHBT Technology

This paper presents the design and characterisation of a two G-band (140 - 220 GHz) fundamental mixers. The mixers are implemented in a 130-nm indium phosphide (InP) double heterojunction bipolar transistor (DHBT) technology. First, a passive double balanced topology was investigated using a diode ring with balanced RF and LO ports. The mixer operates in both upconversion and downconversion modes. In order to reduce the power requirement on the local oscillator (LO) at G-band, the diodes were dc biased. Measurement results show that the mixer has an average conversion loss of 12.4 and 14 dB for upconversion and downconversion modes respectively and covers the frequency range extending from 180 to 194 GHz. The mixer exhibits an LO-RF isolation of 21 dB and requires an LO power of +2 dBm. An upconverting transconductance mixer topology was also investigated using the same technology. Measurement results show that the mixer has an average conversion gain of 1 dB over the frequency range of 171 to 220 GHz. The mixer operates as an upconverter and requires a low LO power of only -4 dBm

D-band Waveguide Transition Based on Linearly Tapered Slot Antenna

In this work, an on-chip Monolithic Microwave Integrated Circuit (MMIC) to waveguide transition is realized based on Linearly Tapered Slot antenna (LTSA) structure. The antenna is implemented on a 50-um-thick Gallium Arsenide (GaAs) substrate and placed in the E-plane of an air-filled D-band waveguide. The transition shows a maximum insertion loss of 1 dB across the frequency range 110-170 GHz. The average return loss of the transition is -15 dB and the minimum is -9 dB. The structure occupies an area of 0.82x0.6 mm2. The transition provides low-loss wide-band connectivity for millimeter-wave systems and addresses integration challenges facing systems operating beyond 100 GHz

F-band Low-loss Tapered Slot Transition for Millimeter-wave System Packaging

This work presents a packaging solution at F-band (90 - 140 GHz) using on-chip waveguide transition. The transition is realized using a Linearly Tapered Slot (LTS) implemented in a commercial Gallium Arsenide (GaAs) Monolithic Microwave Integrated Circuit (MMIC) technology. The LTS is mounted in the E-plane of a split-block waveguide module and fed through a microstrip line. The transition is experimentally verified using a back-to-back test structure and it exhibits an average insertion loss of 1.7 dB over the frequency range extending from 100 to 135 GHz. This work presents an on-chip packaging technique to realize the interface between MMICs and standard waveguides at millimeter-wave (mmW) frequencies and hence addressing one of the main integration challenging facing systems operating at that range

Low-cost D-band Waveguide Transition on LCP Substrate

This work presents a waveguide transition based on a slot radiator implemented on liquid crystal polymer (LCP) substrate. The slot couples the RF signal to a D-band (110–170 GHz) waveguide perpendicular to its plane. The slot is fed using a microstrip line and can be bonded to any monolithic microwave integrated circuit (MMIC). A waveguide split-block that utilizes bed of nails structure is also presented. The structure is used to stop undesired radiation at the interface between the slot and the waveguide opening allowing better coupling between the slot and the waveguide by reducing radiation loss. The transition shows a minimum insertion loss of 2.1 dB and an average of 3.2 dB. The 3-dB bandwidth of the transition covers the frequency range 112 –140 GHz. Another variant of the transition is designed to cover the higher part of the band and shows an average insertion loss of 3.6 dB covering the frequency range 124–154 GHz. The transition presents a simple low-cost technique to interface between standard waveguides and MMICs in millimeter-waves systems

Packaging Technique of Highly Integrated Circuits Based on EBG Structure for +100 GHz Applications

This work presents an on-chip packaging concept suitable for monolithic microwave integrated circuits (MMIC) operating above 100 GHz. The concept relies on using an on-chip transition that couples the signal to a standard air-filled waveguide. The proposed solution utilizes an electromagnetic band-gap (EBG) structure realized using bed of nails to prevent the propagation of parallel plate modes and improve the coupling between the MMIC and the waveguide. The technique shows an average insertion loss of only 0.6 dB across the frequency range 110 - 155 GHz. Moreover, the concept is demonstrated in a D-band amplifier circuitry that is fabricated in an indium phosphide (InP) double heterojunction bipolar transistor (DHBT) technology. Experimental results show that the amplifier exhibits a maximum gain of 18.5 dB with no sign of propagation of any parallel plate modes. This work presents a verified solution for packaging high-frequency integrated circuits, and hence paves the way towards higher system integration above 100 GHz

Compact Low-Loss Chip-to-Waveguide and Chip-to-Chip Packaging Concept Using EBG Structures

This letter presents a novel approach for packaging millimeter-wave (mmW) and terahertz (THz) circuits. The proposed technique relies on using an on-chip coupling structure that couples the signal to a quarter-wavelength cavity, which in turn couples to either a waveguide (WG) or another chip. The solution also uses a periodic electromagnetic bandgap (EBG) structure that controls the electromagnetic wave and prevents field leakage in undesired directions. The proposed solution is fabricated and demonstrated at the D-band (110-170 GHz), and the measurement results show that it achieves a minimum insertion loss of 0.8 and a 3-dB bandwidth extending from 124 to 161 GHz. The proposed approach does not require any galvanic contacts and can be used for packaging integrated circuits in WG modules as well as for chip-to-chip communication

A Compact PCB Gasket for Waveguide Leakage Suppression at 110-170 GHz

An electromagnetic bandgap (EBG) structure is implemented on a printed-circuit board (PCB) as gasket between waveguide flanges. The proposed gasket can reduce leakage between waveguide flanges due to misalignment. A WR-6.5 waveguide proof-of-concept demonstration is presented in this paper covering 110 - 170 GHz with a return loss lower than 12 dB and over a 75 um of air gap between the flanges

A low-phase noise D-band signal source based on 130 nm SiGe BiCMOS and 0.15 mu m AlGaN/GaN HEMT technologies

This paper reports on a record-low-phase noise D-band signal source with 5 dBm output power, and 1.3 GHz tuning range. The source is based on the unconventional combination of a fundamental frequency 23 GHz oscillator in 150 nm AlGaN/GaN HEMT technology followed by a 130 nm SiGe BiCMOS MMIC including a sixtupler and an amplifier. The amplifier operates in compression mode as power-limiting amplifier, to equalize the source output power so that it is nearly independent of the oscillator\u27s gate and drain bias voltages used for tuning the frequency of the source. The choice of using a GaN HEMT oscillator is motivated by the need for a low oscillator noise floor, which recently has been demonstrated as a bottle-neck for data rates in wideband millimeter-wave communication systems. The phase noise performance of this signal source is -128 dBc/Hz at 10 MHz-offset. To the best of the authors\u27 knowledge, this result is the lowest reported phase noise of D-band signal source