No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Energy efficiency maxima for wireless communications: 5G, IoT, and massive MIMO
... In [44], the thermal problem in traditional AESA's was discussed by investigating the effect of PA efficiency on the operating temperature of the PAs. The severity of the problem was shown using the PA in [45] as the baseline for LTE signals, which provides around 9% PA efficiency. ...
... The resulting temperature distribution is given here in Fig. 3 which clearly shows that the heat gets trapped in the center of the array, resulting in an unacceptable temperature rise. Although serious challenges with thermal management occurred recently in the wireless communication area with the introduction of 5G and its intended performance requirements, which has created more interest in thermal management [44], [47], [48], excessive heat dissipation has always been a critical issue for phased array antenna design in such systems as military electronics [49], [50] and space applications [51]. As an example, an X-band airborne phased array antenna [46] is given here in Fig. 4 which shows many microwave modules having transmit and receive circuitry with GaAs power amplifiers that are attached to liquid cooled slats. ...
... Temperature distribution across a traditional 8x16 AESA (taken from[44]). ...
Heat removal capabilities and radiation performances of several sparse antenna array topologies are studied for cooling enhancement in 5G millimeter-wave base station antennas. Both electromagnetic and thermal aspects are jointly considered for the first time in array layout optimization and a novel connection between layout sparsity and thermal management is presented. Two types of active electronically scanned arrays (AESA’s), based on the traditional and planar approaches, are examined. Thermal management in AESA’s is discussed, with a focus on cooling challenges at millimeter waves. Being relatively low-cost and low-profile while supporting flexible beamforming, passively cooled planar AESA’s with fanless CPU coolers are proposed, for the first time, to be used in 5G base stations. Additional cooling for such arrays is achieved by increasing the inter-element distances in the layout. Linear irregular arrays, spiral arrays, thinned arrays, circular ring arrays and heat sink antenna arrays are revisited with a critical discussion on their electromagnetic and thermal performance. The results are compared with regular and square layouts that are used as benchmarks throughout the paper.
... So aggregating many of such components in a small surface can result in a major heat level. In [46], it is pointed out that a 128-antenna-element array (8×16) can reach temperatures above 300 • C. In the analysis, use is made of a LTE PA chip with an efficiency of 9% and a thermal resistance of 23 • C/W. A first-order approximation to model the junction temperature is given by the following expression: ...
... the thermal resistance in (1) is actually fixed. In particular, we assume θ JC to be equal to 23 • C/W according to the PA datasheet in [49], which is the same used in [46]. Although this is an approximation, it will provide a fair first-order comparison between the data found in the references. ...
In order to cope with the needs of fifth-generation (5G) cellular networks and beyond, phased-array antenna systems operating at millimeter-wave (mm-wave) frequencies will be required. This makes the system design very complex. In order to create insight and agility in the design process, we propose a framework that visualises the requirements and trade-offs of 5G-and-beyond systems. Our literature survey uses this framework to compare state-of-the-art papers on Silicon-based beamforming integrated circuits (BFICs) operating in the mm-wave band. Three use-cases are analyzed: Base-stations (BSs), Gateways (GtWs) and User Terminals (UTs). Based on the framework, we explore which implementation fits best with each use-cases. In UT, space and power consumption are the main constraints. For BSs, the main constraint is in output power and noise figure (NF). Finally, in GtW applications there is more flexibility as it has a larger footprint than UT but doesn’t necessarily need to cover the same link-budget constraints of BSs. One of the identified limitations throughout all the cases is the heat generation, which is seen as a major bottleneck in mm-wave phased arrays. Only a few of the references show proper modelling and simulations for heat transfer of the realized BFICs. Finally, a limitation in the BFICs is the output power. In order to realize a mm-wave link at least 13 dBm would be required at the input of each antenna element. Only few references meet this criterion, and only at saturation. Further, in order to achieve more than 13 dBm in back-off operation a higher power density would be required. This would imply a further increase of heat generation in the system.
... In [139], the thermal problem in traditional AESA's was discussed by investigating the effect of PA efficiency on the operating temperature of the PAs. The severity of the problem was shown using the PA in [140] as the baseline for LTE signals, which provides around 9% PA efficiency. ...
... Temperature distribution across a traditional 8x16 AESA[139]. ...
This doctoral thesis presents the first ever irregular/sparse and subarray based reduced-complexity 5G base station antennas that are integrated with low temperature - high efficiency power amplifiers and have wide-angle scan multibeam capability, while providing low level of side lobes and radiation nulls. The developed antenna arrays and beam generation concepts could also have an impact over a broad range of applications where they should help overcome the capacity problem by use of multiple adaptive antennas, improve reliability and reduce interference.
... Combining such an approach mathematically with the array factor and thus the radiation pattern of the array (by assuming the antennas are at the same 2-D location with the heat-generating transceiver chips) would result in a joint optimization of both thermal and electromagnetic performances. Traditionally, conduction-based thermal management is applied in conventional phased arrays where electronic circuit cards are placed orthogonally to the array and the cooling is achieved from the outer edges of the array via a large heatsink [8]. For such systems, intuitively, it can be inferred that more elements (chips) should be placed at the edges of the aperture since otherwise, the heat gets trapped in the middle of the array. ...
... Following similar steps, the far field expression in (6) can be modified to take into account the effect of scanning via multiplication with (7). Thus, the far field of a scanned beam s m at the i th iteration can be computed as follows (1 + jkϵ i n (sin θ cos ϕ − sin θ sm cos ϕ sm ) + jkδ i n (sin θ sin ϕ − sin θ sm sin ϕ sm )) (8) If the u-v coordinates are introduced as u = sin θ cos ϕ, u sm = sin θ sm cos ϕ sm , v = sin θ sin ϕ, v sm = sin θ sm sin ϕ sm (9) the field expression in (8) can be rewritten as ...
An extended-feature, system-driven convex algorithm for the synthesis of uniform-amplitude, irregular planar phased arrays with simultaneous multi-beam optimization for
mm-wave 5G base station applications in multi-user scenarios is presented. The inter-user interferences are suppressed by minimizing the maximum side lobe level (SLL) for a beam scanned freely inside a given sector. The aperture size is restricted to the size of the heatsink baseplate dimensions. A minimum guaranteed inter-element spacing in the final layout is predefined, which prevents element overlapping, eases the thermal problem and helps reduce the effects of high mutual coupling. The algorithm performance is tested via the synthesis of a 64-element integrated array with at least half a wavelength interelement spacing. The optimized array results show that, compared to their regular counterparts, significant reduction in the SLLs is achieved for a beam scanned inside the defined sector, while keeping the maximum temperature of the array at a reliable level.
The effect of mutual coupling on the results is also investigated via full-wave simulations and it is explained how embedded element patterns can potentially be included in the optimization. Superior capabilities of the proposed method are illustrated by comparing
the algorithm output to those reported in the state-of-the-art literature.
... Considering that the heat generated from the conventional phased array configuration is concentrated in the center of the array [7], the excess heat should be transferred to a heat exchanger or to ambient air. Active cooling systems have received much attention due to their effective heat removal capability [8], [9]. ...
The discrete packaging approach of the antenna and active radio frequency components in the Sub‐6 GHz antenna system provided the advantage of effectively dissipating the generated heat within the device. This chapter proposes a compact metal stamped antenna‐in‐package (AiP) structure that can be directly integrated with the transceiver module and expanded in the form of a modular configuration. The proposed AiP not only maximizes the heat removal capability at the passive level but also features good radiation performances. To enhance the heat dissipation capacity of the microchannel heat sinks, a cylinder‐shaped copper is used to connect each amplifier and microchannel. The multiphysical simulation demonstrates that most of the heat is conducted down through the silicon and thermal interface material toward the heat sink. The temperature distribution results ascertain that the heat emission generated from the radio frequency integrated circuit is effectively discharged to the top surface of the package.
5G devices range from base stations, antenna arrays, edge data centers, and transceivers to handsets. Effective thermal management solutions can help 5G devices maintain their increasingly slim footprint while still maintaining the ability to sustain 5G connections without performance drops. Form factors of different 5G devices constrain the selection of different thermal management solutions, including passive cooling, active cooling and hybrid cooling strategies. Materials with excellent thermal performance are required to improve heat transfer capabilities and properties, ensuring the ability to cope with ever-increasing reliability requirements. For example, thermal interface materials (TIMs) are used to fill the air gaps, establish an effective heat conduction channel between electronic components and the radiator, reduce the heat transfer resistance, and improve the heat dissipation performance. This chapter will provide a brief review of thermal management challenges in 5G devices, advanced thermal management solutions for different 5G devices ranging from base stations and antenna arrays, edge data centers and 5G mobile phones, as well as various thermal management materials and components, including thermal interface materials, polymer-based thermal materials and thermal metamaterials.KeywordsThermal managementPassive coolingActive coolingHybrid coolingHeat transferThermal interface materialAir coolingLiquid coolingThermoelectric coolerThermal insulation materialThermal metamaterialMobile edge computing
The Internet of Things (IoT) is a network of things or devices connected with each other designed by embedding sensors, programs, software, network availability, and essential hardware. IoT concept has the potential to improve our day-to-day life by interconnecting so many things in homes, the healthcare industry, etc. A city has so many things like home, serving offices, and traffic management. For connecting all these things at the physical layer, basic requirements are sensors for collection of information in electronic form and wireless communication technologies for collecting and forwarding information by sensors to gateways or servers. With enhancement in the number of sensors, network becomes very complex; hence to transfer information collected from sensors to some gateways reliable and high-speed multi-antenna-enabled communication technologies are very suitable. This chapter gives a detailed description of multi-antenna communication system and different wireless communication technologies having multiple antennas and that are most suitable for developing smart cities.
The world is entering a new era with ubiquitous connectivity among billions of humans and machines, i.e., the 6G massive Internet of Things (IoT). Radar and communication need to be integrated into this system to achieve target detection and massive connectivity. In this work, we first develop a shape-adaptive antenna array composed of multiple sub-arrays spaced at regular intervals. The shape-adaptive antenna array uses flexible material that enables changes in the physical structure to achieve adaptive gain. Subsequently, we investigate the micro-movement of IoT targets, such as the micro-motion characteristics and micro-Doppler effects of rotary-wing drones. The simulation results demonstrate the effectiveness and efficiency of the proposed schemes for detecting UAVs in an IoT scenario.
The encouraging potential of employing large-scale aperiodic base station arrays in addressing the radiation pattern and thermal requirements of the next generation communication systems is demonstrated. Sample 256-element layout-optimized multibeam arrays are presented as a futuristic view. The system benefits (in terms of the statistical quality-of-service, energy efficiency, thermal management, and processing burden) of the proposed arrays, as well as their performance versus design complexity tradeoffs, are explained through interdisciplinary simulations. The key advantage of the proposed antennas over the currently proposed 64-element periodic arrays is identified as the increased gain with much lower side lobes, which yields much less power and less heat per element with more surface for cooling, and allows robust/computationally efficient precoding.
To maximize energy efficiency in communications, particularly wireless communications, it is necessary to minimize power dissipation in all circuitry. This joint minimization is unfortunately not independently achievable. Decisions on the type of signal modulation adopted for use in any particular application can and do put lower limits on achievable circuit power dissipation, and therefore putting a ceiling on achievable energy efficiency. Such restrictions must be removed to fully realize our Green Communications objectives. Here the reasons for the energy efficiency limits are presented, which results in a new Figure of Merit for appropriateness of a signal selection with respect to maximizing available communication energy efficiency.
Learn how envelope tracking, polar modulation, and hybrid designs using these techniques, really work. The first physically based and coherent book to bring together a complete overview of such circuit techniques, this is an invaluable resource for practising engineers, researchers and graduate students working on RF power amplifiers and transmitters. Learn how to create more successful designs. Step-by-step design guidelines and real world case studies show you how to put these techniques into practice A survey of how various transistor technologies help you to choose which transistor type to use for best results Detail on the test and measurement of all aspects of these designs explains how to measure what the circuit is actually doing and how to interpret measurement results.
How to determine if an amplifier is actually switching, or is just operating in compression, is developed here. While compressed amplifier operation is any deviation from linear operation toward lower output at the highest amplifier output powers, switching has additional requirements that the transistor achieve two steady states within each RF cycle: OFF and ON. Conditions necessary for transistor switching operation to occur at RF signal frequencies are derived, and related to the transistor transition frequency metric fT. The degradation of available amplifier efficiency as the operating frequency approaches fT is evaluated. Testing methods to verify that transistor switching operation is achieved are proposed.
Any amplifier operated with a varying supply voltage is actually a three-port circuit, having two inputs and one output. When an amplifier is characterized as a three-port for dynamic supply voltage operation, three separate operating modes appear: linear L-mode and the two nonlinear modes C-mode and P-mode. Each of these modes, along with their relationships and differences, are identified, characterized, and discussed. Relations of these modes to the dynamic power supply transmitter techniques of envelope tracking and/or direct polar are presented. Measurements are reported that provide experimental verification for these amplifier operating modes.
Improving conventional PSK signals for higher energy efficiency requires removing envelope variations which are a primary contributor to lower energy efficiency. A constant-envelope version of PSK, called pure PSK (pPSK) allows designs to achieve the highest energy efficiency available from the circuit technology. It is shown that pPSK is compatible with conventional PSK (cPSK) signals, and that the pPSK spectra have a triangular characteristic. Energy efficiency is further improved in both the transmitter and receiver by eliminating half of the baseband signal processing.
Integration is the key for reducing the cost of electronic circuits. Just like any other circuit, radio frequency (RF) circuits also obey this law. The feasibility of integrating voltage-controlled oscillator (VCO), low-noise amplifiers (LNAs), transmitters, and receivers in complimentary metal-oxide-semiconductor (CMOS) is obvious when looking at publications and state-of-the-art wireless products. Integrating an RF power amplifier (PA) in CMOS is less obvious. This is no surprise; the low supply voltage of CMOS contradicts with high output power, and the rather larger input and output capacitances of CMOS contradict with high gain. But CMOS has one major advantage compared to any other technology: one can integrate a lot of transistors and easily increase complexity. One should recognize and use this strength when aiming for integrated CMOS PAs.
Ubiquitous coverage, the ability of a mobile device to wirelessly communicate as intended from any location in the world, is not a reality today. Multiple wide-area and local-area wireless systems are now deployed in various places around the world. These mobile systems include cellular, local area networks, personal area networks, and specialized networks. Characteristics of these systems span a broad combination of constant-envelope and envelope-varying signals, time-division (half duplex) and code-division (full duplex) multiplexing, and high (several watts) to very low (microwatts) transmitter output powers. As a result, demands on the RF power amplifier (PA) in a multi-mode application are daunting. Linear RF techniques are unlikely to meet all requirements for near-future mobile terminals - particularly the need to simultaneously realize long mobile-battery life while also providing multi-mode operation using bandwidth-efficient signals. Initial results show that newer polar techniques meet many of the objectives for multi-mode and multi-band mobile terminals, including those for battery life. This is information on the cutting edge of RF progress. This article compares and contrasts advanced architectures and presents encouraging preliminary direct polar modulation results.
The generation of RF/microwave power is required not only in
wireless communications, but also in applications such as jamming,
imaging, RF heating, and miniature dc/dc converters. Each application
has its own unique requirements for frequency, bandwidth, load, power,
efficiency, linearity, and cost. RF power is generated by a wide variety
of techniques, implementations, and active devices. Power amplifiers are
incorporated into transmitters in a similarly wide variety of
architectures, including linear, Kalm, envelope tracking, outphasing,
and Doherty. Linearity can be improved through techniques such as
feedback, feedforward, and predistortion
Taking 5G from vision to reality
- M Rumney
SKY66184-11 LTE power amplifier
- Skyworks Inc
Modulation-Available Energy Efficiency
- E Mccune
Fixing the Broken Pattern (A treatise on PSK)
- E Mccune