The evolution of wireless communication points to increasing demands on throughput for data-intensive applications in modern society. Integrated millimeter-wave systems with electrical beam-steering capabilities are promising candidates for wireless technologies of the future and are currently the subject of widespread academic and commercial research. The$D$-band, ranging from 110–170 GHz, offers high aggregate bandwidths (BWs), low atmospheric absorption, and multi-GHz operation at amenable fractional BWs. It, therefore, has the potential to foster efficient, highly integrated wireless-communication systems with data rates approaching 100 Gb/s. This article reviews all aspects of hardware integration against the backdrop of an extensive literature review and outlines the challenges and possible solutions for practical 6G wireless systems in the$D$-band. To this end, this article covers a number of related topics in depth, which includes system definition, possible radio architectures and array configurations, the scope and potential of integrated circuit (IC) technologies, the design and characterization of key circuit blocks, advances in antenna and packaging technologies for high-frequency systems, and an overview of measurement techniques currently employed at$D$-band frequencies. A system-level study based on radio-link simulations of different single-carrier quadrature amplitude modulation (QAM) schemes is presented, which quantifies that the impact physical nonidealities, such as signal-to-noise ratio, phase noise, intermodulation distortion, and amplitude and phase imbalances in quadrature signal paths, have on bit-error rates in broadband$D$-band communication systems. This is followed by a comparative assessment of different arrayed-system configurations that include traditional phased arrays, the use of polarization diversity for the transmission of different or identical data streams, and multiple input multiple output (MIMO) operation. The article also presents an overview of possible transceiver architectures for implementing beam-steering arrays and an outline of the associated tradeoffs. The beam-squinting effect seen in large arrays is also investigated in detail. On the implementation front, we present a comparison between different integrated-circuit technologies for high-frequency applications. These include CMOS and SiGe bipolar complementary metal oxide semiconductor (BiCMOS) heterojunction bipolar transistors (HBTs) in silicon technologies, and MOSFETs, HBTs, and HEMTs in III–V technologies, such as InP and GaAs. Implementation challenges are then addressed, and these include the design of high-frequency circuits in the latest IC technologies, current advances in antenna and packaging technologies, and emerging solutions for hybrid integration. The article also details the design and characterization of critical$D$-band transceiver circuit blocks, namely, power and low-noise amplifiers, mixers, phase shifters, passive components for quadrature-phase generation, and radiators exploring hybrid antennas, which we have developed over the course of the past five years. These results compliment the literature survey with comparisons with state-of-the-art designs and are applied to radio-link simulations to predict the performance of practicable wireless links.

Autonomous driving is disrupting the automotive industry as we know it today. For this, fail-operational behavior is essential in the sense, plan, and act stages of the automation chain in order to handle safety-critical situations on its own, which currently is not reached with state-of-the-art approaches.The European ECSEL research project PRYSTINE realizes Fail-operational Urban Surround perceptION (FUSION) based on robust Radar and LiDAR sensor fusion and control functions in order to enable safe automated driving in urban and rural environments. This paper showcases some of the key exploitable results (e.g., novel Radar sensors, innovative embedded control and E/E architectures, pioneering sensor fusion approaches, AI-controlled vehicle demonstrators) achieved until its final year 3.

Autonomous driving has the potential to disruptively change the automotive industry as we know it today. For this, fail-operational behavior is essential in the sense, plan, and act stages of the automation chain in order to handle safety-critical situations by its own, which currently is not reached with state-of-the-art approaches.The European ECSEL research project PRYSTINE realizes Fail-operational Urban Surround perceptION (FUSION) based on robust Radar and LiDAR sensor fusion and control functions in order to enable safe automated driving in urban and rural environments. This paper showcases some of the key results (e.g., novel Radar sensors, innovative embedded control and E/E architectures, pioneering sensor fusion approaches, AI controlled vehicle demonstrators) achieved until year 2.

Among the actual trends that will affect society in the coming years, autonomous driving stands out as having the potential to disruptively change the automotive industry as we know it today. For this, fail-operational behavior is essential in the sense, plan, and act stages of the automation chain in order to handle safety-critical situations by its own, which currently is not reached with state-of-the-art approaches also due to missing reliable environment perception and sensor fusion. PRYSTINE will realize Fail-operational Urban Surround perceptION (FUSION) which is based on robust Radar and LiDAR sensor fusion and control functions in order to enable safe automated driving in urban and rural environments. In this paper, we detail the vision of the PRYSTINE project and we showcase the results achieved during the first year.

Millimeter-wave devices must use highly directional antennas to achieve GBit/s data rates over reasonable distances due to the high path loss. As a consequence, it is important to precisely align the antenna beams between sender and receiver. Even minor movement or rotation of a device can result in beam misalignment and thus a strong performance degradation. Existing work as well as standards such as IEEE 802.11ad tackle this issue by means of antenna sector probing. This comes at the expense of a significant overhead, which may significantly reduce the performance of millimeter-wave communication, particularly in mobile scenarios. In this paper, we present a mechanism that can track both movement and rotation of 60 GHz mobile devices with zero overhead. To this end, we transmit part of the preamble of each packet using a multi-lobe beampattern. Our approach does not require any additional control messages and is backward compatible with 802.11ad. We implement our scheme on a 60 GHz testbed using phased antenna arrays, and show that we reduce the angle error to less than 5° in most cases. We also perform simulations to validate our approach in a wide range of scenarios, achieving up to 2x throughput gain.

The power efficiency of cellular base stations is a crucial element to maintain sustainability of future mobile networks. To investigate future network concepts, a good power model is required which is highly flexible to evaluate the diversity of power saving options. This paper presents an advanced power model which supports a broad range of network scenarios and base station types, features and configurations. In addition to the power consumption, the model also provides values on the hardware sleep capabilities (sleep depths, transition times, power savings). The paper also discusses the technology trends and scaling factors which are used to predict the power consumption of base stations up to the year 2020. Two use cases are described, illustrating the power savings over different sleep depths, and quantifying the power consumption evolution over different technology generations.

In-band full-duplex sets challenging requirements for wireless communication radios, in particular their capability to prevent receiver sensitivity degradation due to self-interference (transmit signals leaking into its own receiver). Previously published self-interference rejection designs require bulky components and/or antenna structures. This paper addresses this form-factor issue. First, compact radio transceiver feasibility bottlenecks are identified analytically, and tradeoff equations in function of link budget parameters are presented. These derivations indicate that the main bottlenecks can be resolved by increasing the isolation in analog/RF. Therefore, two design ideas are proposed, which provide attractive analog/RF-isolation and allow integration in compact radios. The first design proposal targets compact radio devices, such as small-cell base stations and tablet computers, and combines a dual-port polarized antenna with a self-tunable cancellation circuit. The second design proposal targets even more compact radio devices such as smartphones and sensor network nodes. This design builds on a tunable electrical balance isolator/duplexer in combination with a single-port miniature antenna. The electrical balance circuit can be implemented for scaled CMOS technology, facilitating low cost and dense integration.

With the explosion of wireless communications in number of users and data rates, the reduction of network power consumption becomes more and more critical. This is especially true for base stations which represent a dominant share of the total power in cellular networks. In order to study power reduction techniques, a convenient power model is required, providing estimates of the power consumption in different scenarios. This paper proposes such a model, accurate but simple to use. It evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard. It is flexible enough to enable comparisons between state-of-the-art and advanced configurations, and an easy adaptation to various scenarios. The model is based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters.

This paper presents a 90 nm CMOS digital amplitude modulator for polar transmitter. It reaches an output power of -2.5 dBmRMS using a WLAN OFDM 64QAM modulation at 2.45GHz achieving -26.1 dB EVM and 18% efficiency. To reduce the aliases due to the discrete-time to continuous-time conversion a 2-fold interpolation has been implemented. The amplitude modulator has a segmented architecture. This results in a very compact 0.007 mm2chip area.

This paper presents a digital amplitude modulator (DAM) for polar transmitter in 90 nm CMOS technology. It consists of 255 basic cells digitally activated by an 8-bit amplitude code to shape a non-constant envelope RF output. To reduce the aliases due to the discrete-time to continuous-time conversion a 2-fold interpolation has been implemented. It reaches an output power of -2.5 dBmRMS using a WLAN OFDM 64QAM modulation at 2.45GHz achieving -26.1 dB error vector magnitudes (EVM) and 18% drain efficiency. The 8-bit are segmented addressed. This results in a very compact 0.007 mm2chip area.

Software defined radio (SDR) transceivers comprising a single highly reconfigurable circuit have proven to enable multi-mode multi-band operation at low-cost. However, distortion induced by circuit imperfections hampers standard compliancy over the diverse modes and bands. In this paper, a solution is presented and implemented in hardware to eliminate this distortion by using digital in-system calibration. The proposed calibration scheme offers system performance improvements beyond standard compliancy, achieving e.g. an error vector magnitude (EVM) of 1.8%, a quadrature imbalance of -46 dBc and -42 dBc at the transmitter and receiver output respectively and a carrier feedthrough of -38 dBc. This calibration scheme is very efficient and directly applicable on most SDR transceivers, even in a multiple antenna (MIMO) configuration.

A digital in-system calibration method is presented eliminating distortions caused by transceiver circuit imperfections such as quadrature imbalance, carrier feedthrough and receiver DC-offset. The method enables standard compliancy over multiple modes and multiple bands while using a low-cost Software Defined Radio (SDR). By using non-iterative algorithms and standard compliant calibration signals, the system remains operational during calibration. As the calibration does not require dedicated circuitry, there is no penalty in area or design effort and is thus applicable on most SDR. Implementation shows Error Vector Magnitude (EVM) performance improvements down to 1.8%.

Orthogonal Frequency Division Multiplexing (OFDM) is the modulation of choice for broadband wireless communications. Unfortunately, it comes at the cost of a very low energy efficiency of the analog transmitter. Numerous circuit-level and signal processing techniques have been proposed to improve that energy efficiency. However more disruptive improvement can be achieved at system-level, capitalizing on energy-scalable design and circuit reconfiguration to match the user requirements and operation environment. We describe the design of such an energy-scalable reconfigurable transmitter as well as its control strategy. Based on measurement carried out on the physical realization of this transmitter, the benefit of system-level energy management is shown. Energy-efficiency scalability ranges over 30%, which translates in an average system-level energy improvement of up to 40% compared to a non-scalable system.

The design of complex analog front-ends demands the exploration of a huge design space at different levels of abstraction and using a multitude of simulators. One of the main issues is to guarantee the consistency of the models and the model parameters between the different abstraction levels.A methodology and a tool, called NETLISP, has been developed for the purpose of guaranteeing the consistency between different levels of abstraction. The tool was successfully applied to the design of a multi-mode multi-band analog front-end, showing its applicability on real large-scale designs.