With the demanding system requirements for the fifth-generation (5G) wireless communications and the severe spectrum shortage at conventional cellular frequencies, multibeam antenna systems operating in the millimeter-wave frequency bands have attracted a lot of research interest and have been actively investigated. They represent the key antenna technology for supporting a high data transmission rate, an improved signal-to-interference-plus-noise ratio, an increased spectral and energy efficiency, and versatile beam shaping, thereby holding a great promise in serving as the critical infrastructure for enabling beamforming and massive multiple-input multiple-output (MIMO) that boost the 5G. This paper provides an overview of the existing multibeam antenna technologies which include the passive multibeam antennas (MBAs) based on quasi-optical components and beamforming circuits, multibeam phased-array antennas enabled by various phase-shifting methods, and digital MBAs with different system architectures. Specifically, their principles of operation, design, and implementation, as well as a number of illustrative application examples are reviewed. Finally, the suitability of these MBAs for the future 5G massive MIMO wireless systems as well as the associated challenges is discussed.

Multibeam Antenna Technologies for 5G Wireless Communications

Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

When there are a large number of antennas in massive MIMO systems, the transmitted wideband signal will be sensitive to the physical propagation delay of electromagnetic waves across the large array aperture, which is called the spatial-wideband effect. In this scenario, the transceiver design is different from most of the existing works, which presume that the bandwidth of the transmitted signals is not that wide, ignore the spatial-wideband effect, and only address the frequency selectivity. In this paper, we investigate spatial- and frequency-wideband effects, called dual-wideband effects in massive MIMO systems from the array signal processing point of view. Taking millimeter-wave-band communications as an example, we describe the transmission process to address the dual-wideband effects. By exploiting the channel sparsity in the angle domain and the delay domain, we develop the efficient uplink and downlink channel estimation strategies that require much less amount of training overhead and cause no pilot contamination. Thanks to the array signal processing techniques, the proposed channel estimation is suitable for both TDD and FDD massive MIMO systems. Numerical examples demonstrate that the proposed transmission design for massive MIMO systems can effectively deal with the dual-wideband effects.

Spatial- and Frequency-Wideband Effects in Millimeter-Wave Massive MIMO Systems

A fully integrated technique for wideband cancellation of transmitter (TX) self-interference (SI) in the RF domain is proposed for multiband frequency-division duplexing (FDD) and full-duplex (FD) wireless applications. Integrated wideband SI cancellation (SIC) in the RF domain is accomplished through: 1) a bank of tunable, reconfigurable second-order high-Q RF bandpass filters in the canceller that emulate the antenna interface’s isolation (essentially frequency-domain equalization in the RF domain) and 2) a linear $N$ -path $G_m$ - $C$ filter implementation with embedded variable attenuation and phase shifting. A 0.8–1.4 GHz receiver (RX) with the proposed wideband SIC circuits is implemented in a 65 nm CMOS process. In measurement, $>20\;\text{MHz}\;20\;\text{dB}$ cancellation bandwidth (BW) is achieved across frequency-selective antenna interfaces: 1) a custom-designed LTE-like 0.780/0.895 GHz duplexer with TX/RX isolation peak magnitude of 30 dB, peak group delay of 11 ns, and 7 dB magnitude variation across the TX band for FDD and 2) a 1.4 GHz antenna pair for FD wireless with TX/RX isolation peak magnitude of 32 dB, peak group delay of 9 ns, and 3 dB magnitude variation over 1.36–1.38 GHz. For FDD, SIC enhances the effective out-of-band (OOB) IIP3 and IIP2 to $+\text{25}\text{-}27\;\text{dBm}$ and $+90\;\text{dBm}$ , respectively (enhancements of 8–10 and 29 dB, respectively). For FD, SIC eliminates RX gain compression for as high as $-8\;\text{dBm}$ of peak in-band (IB) SI, and enhances effective IB IIP3 and IIP2 by 22 and 58 dB.

/pdf/integrated-wideband-self-interference-cancellation-in-the-rf-gyi9hx3y7e.pdf

Integrated Wideband Self-Interference Cancellation in the RF Domain for FDD and Full-Duplex Wireless

This paper presents the design of a 60 GHz phase shifter integrated with a low-noise amplifier (LNA) and power amplifier (PA) in a 65 nm CMOS technology for phased array systems. The 4-bit digitally controlled RF phase shifter is based on programmable weighted combinations of I/Q paths using digitally controlled variable gain amplifiers (VGAs). With the combination of an LNA, a phase shifter and part of a combiner, each receiver path achieves 7.2 dB noise figure, a 360° phase shift range in steps of approximately 22.5°, an average insertion gain of 12 dB at 61 GHz, a 3 dB-bandwidth of 5.5 GHz and dissipates 78 mW. Consisting of a phase shifter and a PA, one transmitter path achieves a maximum output power of higher than +8.3 dBm, a 360° phase shift range in 22.5° steps, an average insertion gain of 7.7 dB at 62 GHz, a 3 dB-bandwidth of 6.5 GHz and dissipates 168 mW.

/pdf/a-60-ghz-phase-shifter-integrated-with-lna-and-pa-in-65-nm-2vfyyleuvn.pdf

A 60 GHz Phase Shifter Integrated With LNA and PA in 65 nm CMOS for Phased Array Systems

A fully integrated CMOS ultra-wideband 4-channel timed array receiver for high-resolution imaging application is presented. A path-sharing true time delay architecture is implemented to reduce the chip area for integrated circuits. The true time delay resolution is 15 ps and the maximum delay is 225 ps. The receiver provides 11 scan angles with almost 9 degrees of spatial resolution for an antenna spacing of 3 cm. The design bandwidth is from 1 to 15 GHz corresponding to less than 1 cm depth resolution in free space. The chip is implemented in 0.13 mum CMOS with eight metal layers, and the chip size is 3.1 mm by 3.2 mm. Measurement results for the standalone CMOS chip as well as the integrated planar antenna array and the CMOS chip are reported.

An Integrated Ultra-Wideband Timed Array Receiver in 0.13 $\mu{\hbox{m}}$ CMOS Using a Path-Sharing True Time Delay Architecture

This article covers the basic principles of true-time-delay (TTD)-based space-time array processors and ultra-wideband beamformers. General considerations regarding the need for TTD array processing, optimum array size, antenna spacing, and array patterns are discussed for communication and imaging UWB arrays. Several recent integrated circuit implementations of UWB TTD-based beamformers are presented. A few commercial applications that warrant UWB TTD-based array processing, with emphasis on imaging and sensing, are also described.

Integrated true-time-delay-based ultra-wideband array processing

This paper presents a wireless non-contact sensor that enables detection, localization, and monitoring of people along with their specific features such as gait and cardiopulmonary activities. These types of sensors can be embedded in the environment and networked with the existing wireless infrastructure to create an intelligent and responsive ambient where the health of children, patients, and the elderly can be monitored without intrusion. None of the common sensing modalities including visible optical, infra-red, and ultra-sound can operate under different visibility conditions, without Line-Of-Sight (LOS), under environmental noise, and measure human-specific features simultaneously. Radio Frequency (RF) sensors have been used to localize humans, and monitor their gait and vital signs [1,2]. Most of these RF sensors transmit a Continuous Wave (CW) modulated or un-modulated waveform and detect the Doppler shift caused by the movement of hearts, lungs, and other body parts — the latter referred to as micro-Doppler technique. RF sensors do not require LOS and work under extreme weather and visibility conditions.

A short-range UWB impulse-radio CMOS sensor for human feature detection

A broadband true-time-delay-based multi-beam array architecture is presented in this paper that is applicable to 1-D and 2-D linear antenna arrays. A 1-D millimeter-wave multi-beam array receiver and a 2-D ultra-wide band multi-beam array receiver have been implemented in 0.13- μm SiGe and a 0.13- μm CMOS technology, respectively. The 1-D millimeter-wave multi-beam array receiver with six antennas and seven beams covers the entire 30-40-GHz instantaneous bandwidth, and achieves 18° spatial resolution and ±54° spatial coverage with 4-mm antenna spacing. The 2-D ultra-wideband multi-beam array receiver with 2 × 2 antennas and 7 × 7 beams covers the 3-15-GHz instantaneous bandwidth, and achieves 10° spatial resolution and ±30° spatial coverage in each dimension with 3-cm antenna spacing.

True-Time-Delay-Based Multi-Beam Arrays

The phased array is a common technique where multiple spaced antennas electronically form and scan narrow electromagnetic beams to achieve spatial selectivity. These arrays are also referred to as steering arrays. On the other hand, there are many wireless communications, imaging, and sensing applications where it is highly desirable and even essential to form multiple simultaneous beams, each staring (or scanning around) a specific angle independently. These arrays are also referred to as multi-beam starring arrays.

Ta-Shun Chu

Papers

An Integrated Ultra-Wideband Timed Array Receiver in 0.13 $\mu{\hbox{m}}$ CMOS Using a Path-Sharing True Time Delay Architecture

Integrated true-time-delay-based ultra-wideband array processing

A short-range UWB impulse-radio CMOS sensor for human feature detection

True-Time-Delay-Based Multi-Beam Arrays

A true time-delay-based bandpass multi-beam array at mm-waves supporting instantaneously wide bandwidths