Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.

An Overview of Signal Processing Techniques for Millimeter Wave MIMO Systems

This paper demonstrates an 8-element phased array receiver in a standard 0.18-mum SiGe BiCMOS (1P6M, SiGe HBT ft ap 150 GHz) technology for X- and Ku-band applications. The array receiver adopts the All-RF architecture, where the phase shifting and power combining are done at the RF level. With the integrations of all the digital control circuitry and ESD protection for all I/O pads, the receiver consumes a current of 100 ~ 200 m A from a 3.3 V supply voltage. The receiver shows 1.5 ~ 24.5 dB of power gain per channel from a 50 Omega load at 12 GHz with bias current control, and an associated NF of 4.2 dB (@ max. gain) to 13.2 dB (@ min. gain). The RMS gain error is < 0.9 dB and the RMS phase error is < 6deg at 6-18 GHz for all 4-bit phase states. The measured group delay is 162.5 plusmn 12.5 ps for all phase states at 6-18 GHz. The RMS phase mismatch and RMS gain mismatch among the eight channels are < 2.7deg and 0.4 dB, respectively, for all 16 phase states, over 6-18 GHz. The 8-element array can operate instantaneously at any center frequency and with a wide bandwidth (3 to 6 GHz, depending on the center frequency) given primarily by the 3 dB gain variation in the 6-18 GHz range. To our knowledge, this is the first demonstration of an All-RF phased array on a silicon chip with very low RMS phase and gain errors at 6-18 GHz. The chip size is 2.2 times 2.45 mm2 including all pads.

An X- and K u -Band 8-Element Phased-Array Receiver in 0.18- $\mu{\hbox{m}}$ SiGe BiCMOS Technology

The RF community has long been searching for the ideal switch since the birth of electronics, and it is defined as a device having virtually no insertion loss (Ron = 0 Ω) over a wide frequency range, very high isolation [off-state capacitance (Coff)] = 0 fF), extremely high linearity (IIP2 and IIP3 → infinite), medium- to high-power handling (100 mW to 1 kW), and no dc power consumption. Our entire RF infrastructure ecosystem, from communication system networks, to satellite systems, to wideband spectral analysis, to instrumentation and radar systems, uses a variety of switches for signal routing and control (attenuation, phase shifting, etc.). The ideal switch was achieved long time ago using electromechanical relays, and even after nearly 100 years, it is still the best RF switch ever made from an electrical perspective [1]. It has very low insertion loss (Ron <;1 Ω), very high isolation (Coff of few fF), very high linearity and high power handling (100 mW to 50 W). However, it is bulky, expensive, and has an average lifetime of few million cycles.

The Search for a Reliable MEMS Switch

Reliability of MEMS: A perspective on failure mechanisms, improvement solutions and best practices at development level

A wide-angle scanning planar phased array with pattern-reconfigurable windmill-shaped loop elements has been designed. Each element has a four-port windmill-shaped structure over a high-impedance surface, and it can steer the main beam in four different space quadrants by exciting one port at a time. A 16-element planar (4 × 4) array is fabricated and measured to demonstrate the wide-angle scanning performance of the array. The results show that the fabricated array is able to scan its main beam up to 72° and supports a 3-dB scanning coverage up to 92° in each quadrant. In addition, input amplitudes and phases for the array are optimized with a hybrid particle swarm optimization algorithm to enhance the array scanning performance.

Planar Wide-Angle Scanning Phased Array With Pattern-Reconfigurable Windmill-Shaped Loop Elements

This letter demonstrates a 20-GHz radio frequency microelectromechanical system (RF MEMS)-based electrically switchable antenna on a quartz substrate Two quasi-Yagi antenna elements are monolithically integrated with a single-pole double-throw (SPDT) MEMS switch router network on a 21 mm times 8 mm chip Electrical beam steering between two opposite directions is achieved using capacitive MEMS SPDT switches in the router Port impedance and radiation patterns are studied numerically and experimentally Measured results show that the switched beam antenna features a 27% impedance bandwidth (S11 = -10 dB), a gain of 46 dBi, and a front-to-back ratio of 14 dB at 20 GHz when the control voltage is applied to one of the switch pairs of the SPDT switch

Switched Beam Antenna Based on RF MEMS SPDT Switch on Quartz Substrate

In this paper, we present GaAs MMIC based reconfigurable RF MEMS impedance matching networks for highly integrated (potentially single-chip) frequency-agile LNAs and adaptive multi-band front-ends. Such GaAs MMIC based RF MEMS LNA matching networks have been realized with a frequency tuning range of 40% (10–16 GHz and 15–23 GHz, respectively) and 1–3 dB of in-band losses. Simulated tunable LNA results based on measured data of GaAs MMIC MEMS matching circuits (and simulated data of MEMS matching networks made on quartz) show the potential of achieving a high gain and low in-band noise figure over such wide tuning ranges.

RF MEMS and MMIC based reconfigurable matching networks for adaptive multi-band RF front-ends

In this paper, we report on recent results obtained within a pan-European research effort aiming at a successful integration of RF MEMS switches in a GaAs MMIC foundry process technology. Testing and characterization of GaAs based MEMS switches and RF circuits show promising results with respect to switch cycling tests, micro-seconds switching times and the relatively low losses demonstrated up to millimetre-wave frequencies. Compact GaAs RF MEMS based phase shifters together with a possible packaging solution are also presented.

Design, packaging and reliability aspects of RF MEMS circuits fabricated using a GaAs MMIC foundry process technology

In this paper, we present different types of reconfigurable RF MEMS based matching networks intended for frequency-agile (multi-band) LNAs. Measured results of 2-bits matching networks show a centre frequency tuning range of 2–3 GHz (10–13%) around 20 GHz and 1.5–2.0 dB of minimum losses. Simulated tunable LNA results based on measured data of the RF MEMS matching networks show the possibilities of achieving similar high gain, good matching and low NF over the whole tuning range. The results demonstrate the potential of using RF MEMS switches for the realization of tunable LNAs at microwave and millimetre-wave frequencies.

RF MEMS based impedance matching networks for tunable multi-band microwave low noise amplifiers

This paper presents a dual band LNA that can be switched between two bands (2.4 GHz & 5.2 GHz) for IEEE 802.1 la/b/g WLAN applications. The LNA is also tunable within each band and the tuning is incorporated by on-chip varactors. The test chip consists of two fully integrated narrow-band tunable LNAs along with SPDT switch. For power saving one LNA can be switched off. The technology process is 0.2 mum GaAs offered by OMMIC. The LNA can achieve a relatively good performance over the two bands as demonstrated by simulation. With a 3V supply, the LNA has a gain of 26.2 dB at 2.4 GHz and 21.8 dB at 5.2 GHz and the corresponding NF varies between 2.07 dB and 1.84 dB, respectively. The LNA has an IIP3 of -7 dBm at 2.4 GHz and -1.6 dBm at 5.2 GHz.

C. Samuelsson

Papers

Switched Beam Antenna Based on RF MEMS SPDT Switch on Quartz Substrate

RF MEMS and MMIC based reconfigurable matching networks for adaptive multi-band RF front-ends

Design, packaging and reliability aspects of RF MEMS circuits fabricated using a GaAs MMIC foundry process technology

RF MEMS based impedance matching networks for tunable multi-band microwave low noise amplifiers

Dual Band Tunable LNA for Flexible RF Front End