James N. Murdock

State of the Art in 60-GHz Integrated Circuits and Systems for Wireless Communications

This tutorial presents an overview of the technological advances in millimeter-wave (mm-wave) circuit components, antennas, and propagation that will soon allow 60-GHz transceivers to provide multigigabit per second (multi-Gb/s) wireless communication data transfers in the consumer marketplace. Our goal is to help engineers understand the convergence of communications, circuits, and antennas, as the emerging world of subterahertz and terahertz wireless communications will require understanding at the intersections of these areas. This paper covers trends and recent accomplishments in a wide range of circuits and systems topics that must be understood to create massively broadband wireless communication systems of the future. In this paper, we present some evolving applications of massively broadband wireless communications, and use tables and graphs to show research progress from the literature on various radio system components, including on-chip and in-package antennas, radio-frequency (RF) power amplifiers (PAs), low-noise amplifiers (LNAs), voltage-controlled oscillators (VCOs), mixers, and analog-to-digital converters (ADCs). We focus primarily on silicon-based technologies, as these provide the best means of implementing very low-cost, highly integrated 60-GHz mm-wave circuits. In addition, the paper illuminates characterization techniques that are required to competently design and fabricate mm-wave devices in silicon, and illustrates effects of the 60-GHz RF propagation channel for both in-building and outdoor use. The paper concludes with an overview of the standardization and commercialization efforts for 60-GHz multi-Gb/s devices, and presents a novel way to compare the data rate versus power efficiency for future broadband devices.

Broadband Millimeter-Wave Propagation Measurements and Models Using Adaptive-Beam Antennas for Outdoor Urban Cellular Communications

The spectrum crunch currently experienced by mobile cellular carriers makes the underutilized millimeter-wave frequency spectrum a sensible choice for next-generation cellular communications, particularly when considering the recent advances in low cost sub-terahertz/millimeter-wave complementary metal–oxide semiconductor circuitry. To date, however, little is known on how to design or deploy practical millimeter-wave cellular systems. In this paper, measurements for outdoor cellular channels at 38 GHz were made in an urban environment with a broadband (800-MHz RF passband bandwidth) sliding correlator channel sounder. Extensive angle of arrival, path loss, and multipath time delay spread measurements were conducted for steerable beam antennas of differing gains and beamwidths for a wide variety of transmitter and receiver locations. Coverage outages and the likelihood of outage with steerable antennas were also measured to determine how random receiver locations with differing antenna gains and link budgets could perform in future cellular systems. This paper provides measurements and models that may be used to design future fifth-generation millimeter-wave cellular networks and gives insight into antenna beam steering algorithms for these systems.

38 GHz and 60 GHz angle-dependent propagation for cellular & peer-to-peer wireless communications

As the cost of massively broadband® semiconductors continue to be driven down at millimeter wave (mm-wave) frequencies, there is great potential to use LMDS spectrum (in the 28-38 GHz bands) and the 60 GHz band for cellular/mobile and peer-to-peer wireless networks. This work presents urban cellular and peer-to-peer RF wideband channel measurements using a broadband sliding correlator channel sounder and steerable antennas at carrier frequencies of 38 GHz and 60 GHz, and presents measurements showing the propagation time delay spread and path loss as a function of separation distance and antenna pointing angles for many types of real-world environments. The data presented here show that at 38 GHz, unobstructed Line of Site (LOS) channels obey free space propagation path loss while non-LOS (NLOS) channels have large multipath delay spreads and can exploit many different pointing angles to provide propagation links. At 60 GHz, there is notably more path loss, smaller delay spreads, and fewer unique antenna angles for creating a link. For both 38 GHz and 60 GHz, we demonstrate empirical relationships between the RMS delay spread and antenna pointing angles, and observe that excess path loss (above free space) has an inverse relationship with transmitter-to-receiver separation distance.

60 GHz Wireless: Up Close and Personal

To meet the needs of next-generation high-data-rate applications, 60 GHz wireless networks must deliver Gb/s data rates and reliability at a low cost. In this article, we surveyed several ongoing challenges, including the design of cost-efficient and low-loss on-chip and in-package antennas and antenna arrays, the characterization of CMOS processes at millimeter-wave frequencies, the discovery of efficient modulation techniques that are suitable for the unique hardware impairments and frequency selective channel characteristics at millimeter-wave frequencies, and the creation of MAC protocols that more effectively coordinate 60 GHz networks with directional antennas. Solving these problems not only provides for wireless video streaming and interconnect replacement, but also moves printed and magnetic media such as books and hard drives to a lower cost, higher reliability semiconductor form factor with wireless connectivity between and within devices.

A 38 GHz cellular outage study for an urban outdoor campus environment

Wireless systems require increasingly large system bandwidths that are only available at millimeter-wave frequencies. Such spectrum bands offer the potential for multi-gigabit-per-second data rates to low-cost massively broadband® devices. To enable mobile outdoor millimeter-wave cellular-type applications, it is necessary to determine the coverage potential of base stations in real-world environments. This paper presents the results of a measurement campaign of 38 GHz outdoor urban cellular channels using directional antennas at both the mobile and the base station, and assesses outage probabilities at two separate transmitter locations on the campus of The University of Texas at Austin. Our measurements demonstrate the viability of directional antennas and site-specific planning for future mm-wave cellular, and show that cell radii of ~200 M will provide a very high probability of coverage in an urban environment. As production costs for millimeter-wave technologies continue to fall [1], we envision millimeter-wave cellular systems with dense base station deployments as a cost effective means of delivering multi-Gbps data rates to mobile cell phone and internet users.

Cellular broadband millimeter wave propagation and angle of arrival for adaptive beam steering systems (invited paper)

The advent of inexpensive millimeter wave devices and steerable antennas will lead to future cellular networks that use carrier frequencies at 28 GHz, 38 GHz, 60 GHz, and above. At these frequencies, the available RF bandwidth is much greater than that of current 4G systems, and high gain millimeter wave steerable antennas can be made in much smaller form factor than current products. This paper presents an extensive measurement campaign and initial results for base-station - to - mobile propagation situations at 38 GHz carrier frequencies in an outdoor urban environment using directional, steerable antennas. This work provides angle of arrival (AOA) and RF multipath characteristics for highly directional antenna beams that may exploit non-line-of-sight propagation paths for futuristic channels at 38 GHz. This work yields data for a variety of antenna pointing and antenna beamwidth scenarios in line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios.

17.8 A 190nW 33kHz RC oscillator with ±0.21% temperature stability and 4ppm long-term stability

In wireless networks with a low duty cycle, the radio is operational for only a small percentage of the time. A sleep timer is used to synchronize the data transmission and reception. The total system power is then limited by the sleep power and the sleep timer frequency stability. Low-frequency crystal oscillators are a common choice for sleep timers due to their excellent long-term stability, frequency stability over temperature, and very low power consumption. However, the external crystal cost and board area are undesired. If an integrated oscillator is used as an alternative, the frequency variation must be minimized so the sleep time can be maximized.

Power efficiency and consumption factor analysis for broadband millimeter-wave cellular networks

The growing demand for bandwidth intensive wireless applications and devices portend a future where millimeter-wave and sub-THz carrier frequencies will be used to provide massively broadband® bandwidths and many Giga-bits-per-second (Gbps) data rates in mobile environments [1]. Concurrently, the importance of energy efficiency for communication systems incentivizes discovery of new routing and access techniques that work in conjunction with power saving protocols to maximize battery life and improve power consumption. Wireless channels, as well as the wireless devices themselves, play a major role in determining both achievable data rates and power requirements. In this paper, we use the consumption factor [2] framework to quantify the impact of channel characteristics on both data rate performance and power consumption in a wireless link. Based on recent 38 GHz cellular propagation measurements [3], we demonstrate how future (5G) millimeter-wave cellular channels will impact the data rates and power requirements for future millimeter-wave cellular systems having cell radii less than a km. Analysis results presented here show how to include frequency-domain representations of the channel for use in the consumption factor analysis. A key result from the analysis is that, as massively broadband systems become more prevalent, it will be important to assess the ideal cell size to achieve the lowest energy consumption per pit. Higher bandwidth systems generally benefit form shorter transmission distances. As futuristic cellular standards contemplate the use of millimeter-wave frequencies for greater bandwidths, the work here may offer insight into how to analyze energy efficiency and performance.

Challenges and approaches to on-chip millimeter wave antenna pattern measurements

We present two methods to remove wafer probe interference radiation from measured on-chip antenna patterns performed in a probe station environment. On-chip antenna pattern and gain measurements are affected by parasitic probe tip radiation as well as scattered energy from the metal probe station environment. In this work, we use superposition and S-parameter techniques to de-embed the effects of probe tip radiation. On-chip Dipole, Yagi, and Rhombic antennas were fabricated using standard 180nm CMOS, and radiation patterns were measured at 60 GHz. This work shows methods that improve the ability to reliably design, predict, and measure on-chip antenna patterns.

5.9 A 24MHz crystal oscillator with robust fast start-up using dithered injection

Wireless nodes in Internet-of-Everything (IoE) applications achieve low power consumption by operating the radio at very low duty cycles. The wireless node spends most of its time in sleep, waking only occasionally to transmit or receive data. For some standards, such as Bluetooth Low Energy (BLE), the data or advertising packet length can be less than the time it takes the crystal oscillator, which is used as the reference clock for the radios PLL, to turn on. Figure 5.9.1 shows a simplified power profile for a node with a typical BLE advertising packet length. A significant fraction of energy used for each RX/TX burst is used to turn on the oscillator. For applications where average power is not dominated by sleep power, the crystal oscillator start-up time can be a large contributor to average power consumption.