The fifth generation (5G) research and development has been fueled by many new breakthroughs in various areas. The recent progress in carrier aggregation (CA), licensed assisted access (LAA), massive MIMO (MaMi), beamforming techniques, cooperative spectrum sensing (CSS), compressive sensing (CS), machine learning, etc., has provided inspiring and promising approaches to address 5G and beyond challenges. However, at the user equipment (UE) end, limited design budget and hardware resources bring along a series of challenging implementation issues when delivering multi-standard and multi-functional wireless communications. In this paper, we first review recent advances in technical standards and critical enabling techniques, accompanied with several case studies of product developments. After the classification of typical 5G application and deployment scenarios, we propose and analyze a novel hardware reuse and multiplexing solution to facilitate cost-effective and energy-efficient UE design, followed by an investigation of state-of-the-art hardware development from the systems and circuits standpoint. Moreover, wireless UE hardware solutions, UE proof-of-concept (PoC) implementation and field test are proposed and discussed. Finally, the new trends of UE design and terahertz technologies for 5G and beyond applications are investigated and envisioned.

/pdf/enabling-multi-functional-5g-and-beyond-user-equipment-a-10lgjh6d0f.pdf

Enabling Multi-Functional 5G and Beyond User Equipment: A Survey and Tutorial

This article presents an extremely broadband 24.5–43.5 GHz receiver (RX) achieving 32–56-dB instantaneous full-band image rejection (IR), which supports multiple major mm-Wave 5G bands at 24.5/28/37/39/43 GHz. A compact transformer-based I/Q network (0.14 mm2) is proposed to generate high-precision LO I/Q signals at millimeter-wave (mm-Wave) and provide built-in load impedance up-transformation for passive voltage amplification, boosting the LO swing for a higher RX conversion gain (CG). The high-quality differential I/Q generation is measured with phase/amplitude variation less than ±1.8°/±0.15 dB over an instantaneous wide bandwidth of 25–50 GHz without any calibration or switching/tunable elements. The RX is measured with a peak 35.2-dB CG and 18-dB gain tuning to accommodate complex EM environments. The RX modulation tests successfully demonstrate receiving 18-Gb/s 64-QAM and 14.4-Gb/s 256-QAM signals. In addition, the RX is tested with concurrent injection of a desired signal and an image, while the image uses the same wideband modulation scheme and data rate as the desired signal. The RX successfully rejects the wideband images and receives the desired signals of 12-Gb/s 64-QAM with −27.6-dB EVM and 8-Gb/s 256-QAM with −33.47-dB EVM. To the best of our knowledge, this article presents the first CMOS RX front end that covers 24.5–43.5-GHz mm-Wave 5G bands and supports instantaneous full-band IR with no calibration, switching/tuning elements, or external controls, enabling future wideband low-latency 5G MIMOs.

A 24.5–43.5-GHz Ultra-Compact CMOS Receiver Front End With Calibration-Free Instantaneous Full-Band Image Rejection for Multiband 5G Massive MIMO

Two 4-bit active phase shifters integrated with all digital control circuitry in 0.13-mu m RF CMOS technology are developed for X- and Ku-band (8-18 GHz) and K-band (18-26 GHz) phased arrays, respectively. The active digital phase shifters synthesize the required phase using a phase interpolation process by adding quadrature-phased input signals. The designs are based on a resonance-based quadrature all-pass filter for quadrature signaling with minimum loss and wide operation bandwidth. Both phase shifters can change phases with less than about 2 dB of RMS amplitude imbalance for all phase states through an associated DAC control. For the X- and Ku-band phase shifter, the RMS phase error is less than 10 degrees over the entire 5-18 GHz range. The average insertion loss ranges from -3 dB; to -0.2 dB at 5-20 GHz. The input P-1dB for all 4-bit phase states is typically - 5.4 +/- 1.3 dBm at 12 GHz in the X- and.Ku-band phase shifter. The K-band phase shifter exhibits 6.5-13 degrees of RMS phase error at 15-26 GHz. The average insertion loss is from -4.6 to -3 dB at 15-26 GHz. The input P-1dB of the K-band phase shifter is -0.8 +/- 1.1 dBm at 24 GHz. For both phase shifters, the core size excluding all the pads and the output 50 Omega matching circuits, inserted for measurement purpose only, is very small, 0.33 x 0.43 mm(2). The total current consumption is 5.8 mA in the X- and Ku-band phase shifter and 7.8 mA in the K-band phase shifter, from a 1.5 V supply voltage.

/pdf/0-13-mu-m-cmos-phase-shifters-for-x-ku-and-k-band-phased-224uhr9k0o.pdf

0.13-mu m CMOS phase shifters for X-, Ku-, and K-band phased arrays - eScholarship

The ever-growing demand for low power, high performance, cost-effective, low-profile, and highly integrated wireless systems for emerging applications has triggered the need for the enormous innovations in wireless transceiver systems, components, architectures and technologies. This is especially valid for the antenna which is an integral component of the wireless transceiver systems and contributes significantly in determining their overall performance. Antenna-on-Chip (AoC) is an alternative antenna technology, which has drawn a substantial attention in recent days because of its various benefits over off-chip antenna technology. A few of these benefits include miniaturization, low power, low cost, and high integration of the wireless modules. Motivated by these valuable advantages and to unveil the true potential of the AoCs, this article presents, for the first time, a comprehensive survey of the suitability, advantages, and challenges of the AoCs for the emerging wireless applications such as 5th generation (5G) Wireless Systems, Internet-of-Things (IoT) Wireless Devices and Systems, Wireless Sensor Networks (WSNs), Wireless Interconnects, Wireless Energy Transfer, Radio Frequency (RF) Energy Harvesting, Biomedical Implants, Unmanned Aerial Vehicles (UAVs), Autonomous vehicles, Innovative characterization methods for Integrated Circuits (ICs) and Antennas, and Smart City. In addition, this article presents the current state-of-the-art of the AoC's applications by classifying their applications in Millimeter-Wave (MM-Wave) band, Terahertz (THz) band, and low-frequency bands. The article also investigates and describes some useful methods for the mitigation of the challenges and issues posed by the emerging applications for the realization of the AoCs in a systematic manner. A concise description of the future directions of the AoCs with respect to each emerging application is also a part of this article. It is expected that this well-structured and organized survey will not only act as an excellent source of scholarship for the relevant research community, but also open up a world of novel research opportunities.

/pdf/the-potentials-challenges-and-future-directions-of-on-chip-45r9j698zs.pdf

The Potentials, Challenges, and Future Directions of On-Chip-Antennas for Emerging Wireless Applications—A Comprehensive Survey

The performance and robustness of millimeter-wave (mm-wave) phased-array transmitters (TXs) define, to a large extent, the quality of a high-data-rate 5G link. In practical situations, however, this TX performance is strongly affected by mutual coupling among the closely-spaced radiating elements in the phased-array antenna, yielding a beam-steering angle-dependent and time-varying loading or VSWR condition. Furthermore, 5G mm-wave systems typically employ spectrally efficient modulation schemes with high peak-to-average power ratios (PAPRs). This requirement demands the TX power amplifier (PA) to operate in power back-off (PBO), thus degrading its average efficiency. To alleviate this issue, outphasing or Doherty PAs (DPAs) can be adopted [1–4]. However, as depicted in Fig. 14.4.1 (Top left), these efficiency-enhancement techniques will worsen the output reflection coefficient of the PA $(\Gamma_{{\mathrm {PA}}}$). Consequently, the unwanted “element-to-element” coupled signal reflects back to the antenna and will deteriorate the phased-array beam pattern and its TX linearity. A previously promoted solution for this antenna VSWR problem is load mismatch detection, followed by tuning of the output matching network (self-healing). However, this requires the use of a reconfigurable and inevitably lossy matching network [5]. Also, active load pulling [1] and using a reconfigurable series/parallel DPA configuration [2] have been proposed to realize a VSWR resilient efficiency-enhanced TX. Nevertheless, all these techniques are only suitable when dealing with a known and stable antenna impedance mismatch, which is, unfortunately, not the case in practical situations.

A 24-to-30GHz Double-Quadrature Direct-Upconversion Transmitter with Mutual-Coupling-Resilient Series-Doherty Balanced PA for 5G MIMO Arrays

The development of next-generation 5G networks is ongoing. The large available bandwidth at mm-waves allows increasing channel capacity well beyond the levels offered by LTE. Wide ranges of spectra, with sub-bands centered at 28GHz, 37GHz, and 39GHz, have been appointed for 5G development to facilitate international roaming and intra-networks connections [1]. In this scenario, generation of ultra-low phase-noise quadrature (IQ) signals with >40dB image rejection ratio (IRR) over >40% fractional bandwidth is key to efficiently deliver extreme data-rates through high-order spectrally efficient modulations. Quadrature voltage-controlled oscillators are disregarded because of their limited tuning range and also due to a severe trade-off between phase noise and phase accuracy. Solutions leveraging single-phase VCOs followed by quadrature generators is seen as a better strategy. Still, the challenging phase noise, required to support higher-order modulations trading-off with tuning range, mandates at least two VCOs covering half bandwidth each. For quadrature generation, distributed couplers, e.g., Lange couplers, are bulky and not amenable to integration. Hybrid couplers based on coupled inductors offer a compact footprint with low loss, but they are disregarded, because a few percent variation in the coupling coefficient, k, leads to unacceptable phase deviations. Polyphase filters (PPFs) and their improvements are widely adopted at RF [2]. In [3], the PPF operation at mm-waves is proven through careful layout techniques. Still, wideband operation can be achieved only by cascading several stages, severely increasing signal loss and power consumption.

A >40dB IRR, 44% fractional-bandwidth ultra-wideband mm-wave quadrature LO generator for 5G networks in 55nm CMOS

Precise generation of quadrature signals over a wide frequency range is a key function for the next-generation 5G communication systems. In this paper, we present a wideband quadrature generator based on a single-stage polyphase filter (PPF). A phase detector senses the phase error from quadrature signals generated by a single-stage PPF, and a feedback circuit continuously tunes the filter center frequency to the input signal frequency by varying the polyphase resistance of an nMOS device in triode. Transformer-based resonant circuits at the input and output of the PPF ensure wide bandwidth and low loss. Prototypes have been realized in a 55-nm CMOS technology. Tailored to the next-generation 5G systems for cross-network interoperability requirements, the measured quadrature generator shows an image rejection ratio IRR > 40 dB over a bandwidth from 28 to 44 GHz. The power consumption is 36 mW for the PPF and buffers, and 3 mW only for the calibration loop. One key aspect of the proposed solution is its robustness over process, voltage and temperature (PVT), one of the weak aspects of alternatives proposed in the literature. This solution compares favorably with the state of the art and shows the largest fractional bandwidth (44%) among the quadrature generators at frequencies greater than 20 GHz, to authors’ knowledge.

A PVT-Tolerant >40-dB IRR, 44% Fractional-Bandwidth Ultra-Wideband mm-Wave Quadrature LO Generator for 5G Networks in 55-nm CMOS

In this paper, we present a novel phase shifter topologies to construct 45°, 90° and 180° phase shifter cells laid-out using 180 nm TSMC technology These phase units provides compact circuit sized with reasonable implementation components Instead of using pin-diodes in the phase shifter topologies, CMOS switches are used to have advantages of simple control circuit for switching and very low power consumption Operation of the new circuit is based on the phase shifting properties of the symmetrical all-pass LC lattices As a consequence of this research, it is straight forward to construct phase shifting cells over a wide frequency band, with various angles for multi bit phase array systems In this work explicit design equations are presented according to ideal lumped elements and normalized frequency A numerical method which includes the design model is analyzed in MATLAB Top level design is simulated in CADENCE Simulations performed with actual elements from TSMC and inductors are designed in ASITIC tool A phase shift between 3–6GHz is achieved with less than 45° phase error for 45°, 90° and 180° Insertion loss for 45°, 90° and 180° are between 34–59 dB, 103–114 dB and 109–185dB respectively

Symmetric lattice 45°, 90° and 180° digital phase shifter at 3–6 GHz for LTE, WIFI, Radar applications

This paper presents a low power low voltage RF front-end for short range outdoor applications, meeting the IEEE 802.15.4 standard of 2.4 GHz for ZigBee systems. The design includes a two stage low power LNA with an integrated differential power splitter. Also, a low power, low voltage mixer is implemented to maintain the power specification of the design. The whole system has an almost 2.76 mW power dissipation and is supplied by 1.2 V voltage source. The design accomplished in TSMC 180 nm CMOS process. According to the simulation results acquired by Cadence Virtuoso, the design owns 22 dB conversion gain and 4.8 dB noise figure with IIP3 of −6.3 dBm.

Design and simulation of a low power RF front-end for short range outdoor applications

A low-power quadrature local oscillator (LO) generation scheme embedded in a direct-conversion E-band transmitter (TX) is presented. A single-stage polyphase filter is closed in a loop and continuously tuned by means of a quadrature phase detector to maintain precise I/Q signals independently from LO frequency and component variations, thus making the solution wideband and robust against process, supply, and temperature variations. The analog phase detector, realized with fully balanced analog multipliers, is critical to reach high accuracy. Careful circuit analysis and simple design solutions are proposed to avoid systematic phase errors and to maintain high detector gain despite the high operating frequency. The TX, realized in BiCMOS 55-nm technology, delivers a maximum linear output power of 20.5 dBm at 80 GHz with 14% power efficiency. The LO buffers consumes 115 mW from 2.3-V supply while the LO calibration circuits need 16 mW only and allows to maintain a remarkable image rejection ratio of 40 dB or better over 70–90 GHz.

Farshad Piri

Papers

A >40dB IRR, 44% fractional-bandwidth ultra-wideband mm-wave quadrature LO generator for 5G networks in 55nm CMOS

A PVT-Tolerant >40-dB IRR, 44% Fractional-Bandwidth Ultra-Wideband mm-Wave Quadrature LO Generator for 5G Networks in 55-nm CMOS

Symmetric lattice 45°, 90° and 180° digital phase shifter at 3–6 GHz for LTE, WIFI, Radar applications

Design and simulation of a low power RF front-end for short range outdoor applications

70–90-GHz Self-Tuned Polyphase Filter for Wideband I/Q LO Generation in a 55-nm BiCMOS Transmitter