Armms RF and Microwave Society
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Conferences

Next Conference:

Monday 23rd April to Tuesday 24th April 2018 at The Oxford Belfry, Nr Thame

Booking for the April 2018 meeting of the ARMMS RF & Microwave Society Conference will open soon.

Young Engineer Sponsorship: The ARMMS RF & Microwave Society provides sponsorship for young engineers (28 or below) who have had papers accepted for presentation at each meeting. Sponsorship is £100 cash plus free attendance (including conference dinner and overnight accommodation). Potential candidates should identify themselves as eligible at time of submission and state their date of birth. This offer is limited to a maximum of 2 places per meeting.

Best Paper Award: The Steve Evans-Pughe prize is awarded to the best presenter at each meeting. The award is £200 for the best paper and £50 for the runner-up. The prize is sponsored by NI.

If you are interested in submitting a paper for presentation at this conference, please contact the technical coordinator (details below). Papers currently listed below are those already accepted. The deadline for submissions is February 23rd. For all other enquiries please email enquiries@armms.org

VENUE

The Oxford Belfry
Milton Common
Nr Thame
Oxfordshire
OX9 2JW

Webhttp://www.qhotels.co.uk/our-locations/the-oxford-belfry/

PROGRAMME CO-ORDINATOR

Gavin Watkins
Toshiba Research

Tel+44 (0)7762 158 649
Emailgavin.watkins@toshiba-trel.com

PAPERS

A Broadband LNA Design in Common-Source Configuration for Reconfigurable Multi-standards Multi-bands Communications

Sunday C. Ekpo, Rupak Kharel and MfonObong Uko
Manchester Metropolitan University

The design of broadband low noise amplifiers (LNAs) for reconfigurable and real-time multi-standard multiband RF/microwave transceiver requires a holistic design trade-off for a given active device configuration. The common-source configuration generally yields moderate gain, narrow bandwidth and compensated stability for the lowest noise figure response. This paper presents a novel single-ended LNA topology that achieves high gain, broadband and very low noise in the common-source configuration. The pseudomorphic high electron mobility transistor process technology was utilised over the C- and K-band frequencies. The GaAs-based active device libraries came from two different foundries. The simulation results show that the reported circuit topology yielded gain and noise figure responses of 37.6 dB and 0.5 dB (over 4–8 GHz); and 30 dB and 1.0 dB (over 18–21.6 GHz). The minimum stability factor was higher than 4 at the respective centre-design frequencies and the in-band ripples were 5% (C-band) and 4% (K-band) relative to the 3 dB communication threshold. These results enable the reported broadband LNA to accommodate a wide dynamic range for multi-process technologies. The presented LNA designs can combine multi-band direct-conversion RF transceiver with embedded field programmable gate array processing to provide a multi-standard radio solution for reliable and cost-effective capability-based communication solutions.


A New Golden Age of Radio Development tools for Software Defined Radio

Richard G. Ranson
Radio System Design Ltd

In the last 15 years, entirely behind the scenes, the technology for radio has been completely revolutionised. First the full scale adoption of digital modulation and advanced coding has enabled bandwidth efficiency approaching the Shannon limit. Then, the integration of digital and RF CMOS has created sophisticated, flexible hardware platforms capable of convering data to RF in the low GHz spectrum and back, using only an handfull of components. The end result, Software Defined Radio (SDR), is now professional main stream, but the important thing is that the cost of entry into this market has continued to fall.


A Transmission Line-Based Load Compensation Network for Outphasing Power Amplifiers

Aleksander Bogusz, Jonathan Lees, Roberto Quaglia, Gavin Watkins and Steve C. Cripps
Cardiff University

The outphasing concept proposed by Chireix in 1935 is an effective method to address the efficiency drop in power amplifiers caused by modulated signals exhibiting high peak-to-average power ratios. In outphasing, the efficiency is preserved by amplifying two constant amplitude signals. Amplitude modulation, now contained as phase offset between input signals, is reconstructed at the combiner stage by performing vector summation of the two constant amplitude signals.

One of the key elements enabling high efficiency in Chireix outphasing is the load compensation network, traditionally realized by a shunt reactance at the output of each saturated amplifier. This paper presents an alternative way of realising this network, which has the advantage of not requiring additional discrete components to provide the aforementioned reactance. Instead, the same effect is achieved using simple transmission lines in series with the output of each amplifier, here named offset transmission lines (OTLs).

At 2 GHz, the fabricated prototype amplifier maintains an efficiency greater than 50% over an output power back-off in excess of 8 dB.  Drain efficiencies higher than 65% and 40% are maintained over 5.5dB and 10dB output power ranges respectively, while achieving a maximum combined output power of 44.5 dBm.


Analysis of the VSWR Withstand Capability of a Balanced Amplifier

John Walker1 and Malcolm Edwards2,
1:Integra Technologies, Inc. 2:Applied Wave Research Corporation

An analytic calculation is made of the VSWR withstand capability of a balanced amplifier and the results are verified by computer simulation. It is shown that in the presence of a mismatch at the output that one transistor in the balanced amplifier sees an improved VSWR whereas the other sees a larger mismatch and a very simple equation is derived that enables the VSWR that the transistors see to be calculated. The paper highlights deficiencies in previous works addressing this topic.


Cost-Effective Hybrid Input-Matched GaN Transistor for S-band Radar Applications

Robert Smith*, Liam Devlin*, Raj Santhakumar#, Richard Martin#
*Plextek RFI, #Qorvo Inc.

The use of Gallium Nitride (GaN-on-SiC) technology in high performance RF power amplifiers (PAs) is now widespread. Whilst the per-area cost of GaN-on-SiC has dropped significantly in recent years it is still higher than competing technologies, and as active phased-array radars can contain hundreds of amplifiers any cost reduction that can be achieved quickly adds up. At the same time, the RF performance of the system is paramount, and GaN-on-SiC can be used to design power amplifiers that have excellent power and efficiency.

This paper describes the design of the QPD1020 hybrid input-matched GaN transistor, which includes internal input matching for 2.7 – 3.5 GHz realised on a passive GaAs die. This transistor provides the performance of GaN with the convenience of internal input matching at a reduced cost compared to a GaN MMIC. The QPD1020 can be used as an output stage in an active phased-array radar system or as a driver amplifier for a higher power output stage. An accompanying PA reference design with an output matching network tuned for optimum efficiency between 2.7 to 3.1 GHz is also described.


Effect of supply modulator voltage ripple on efficiency and linearity in Envelope Tracking Power Amplifiers

Sattam Alsahali, Alexander Alt, Peng Chen and Jonathan Lees
Cardiff University

Envelope Tracking (ET) is developed as a key solution in Radio frequency power amplifier (RFPA) design for 5G communications systems due to its potential to efficiently amplify signals with high power average peak ratio (PAPR) and wide instantaneous bandwidths. In consequence of the fact that ET system comprises of various subsystems such as envelope generation, supply modulator, and linearization module, the ET design faces many difficulties to obtain the desired performance. This paper presents an experimental investigation on the interaction between the RFPA and supply modulator with output ripples. By introducing external ripples to the supply modulator, the effects in terms of efficiency and linearity on the RFPA have been observed and analysed. Experimental results show that the efficiency and linearity both degrade as the ripple amplitude increases, with additional intermodulation distortion produced in the sidebands. By using appropriate shaping function, the effect of the ripples can be minimized to improve linearity of RFPA. However, commercial digital pre-distortion DPD algorithm can’t pre-distort the output ripples.  


Frequency Selective Surface with Miniaturized Elements: a Different Approach

Muaad Hussein, Jiafeng Zhou and Yi Huang
University of Liverpool

Recently, many approaches have been proposed to miniaturize the dimensions of frequency selective surface (FSS) array elements. This is usually achieved by increasing the equivalent electrical lengths of array elements. In this paper, a different approach is proposed to realize the miniaturization by making use of the capacitance between adjacent layers of an FSS. Such an FSS will not only have a very small element size, but also have an extremely low profile. The element size is one of the smallest reported so far to the authors’ best knowledge.


High-Speed and Wideband On-Wafer Load Pull for Model Extraction, Validation and Design

Jim Creed
Castle Microwave, on behalf of Maury Microwave Corporation

The motivation and various methodologies for RF power device characterization using load pull will be presented.

Test system solutions will be addressed for passive and active impedance control, scalar and vector-receiver measurements and mixed-signal active load pull.

These will be applied to the activities of compact model validation, behavioural model extraction, and amplifier design.


Mutual Coupling Impact on GaN Power Amplifiers in Antenna Array Systems

Maria Jesus Canavate Sanchez, Souheil Bensmida, Konstantinos Mimis, George Goussetis, Apostolos Georgiadis, Gavin Watkins and Mark Beach
Heriot-Watt University

Multiple-input multiple-output (MIMO) technologies have become fundamental for telecommunications. In the fifth-generation (5G) standard, the MIMO system requires multiple independent radio frequency (RF) paths to excite an antenna array. In one possible implementation, each RF path has its own power amplifier (PA), whose performance is compromised due to the mutual electromagnetic coupling between the radiating elements. Consequently, the performance of digital pre-distortion (DPD) techniques can be compromised, negatively impacting the linearity of the PA. This impact on the PA behaviour does, in turn, affect the bit error rate (BER) performance due to the fact that certain digital modulations proposed for 5G, such as quadrature amplitude modulation (QAM), are extremely sensitive to the PA non-linearities.

Although this topic has been actively examined, there are few experimental measurements of the interaction between DPD techniques and PA load impedance mismatch in the literature. Moreover, measurements of GaN PAs, which can be used in multi-user MIMO systems due to their high power capabilities, under mismatched conditions are scarce. As different device technologies may have different behaviours when it comes to their linearity characteristics and load impact, this paper aims to present measured results to show the output impedance variation impact on the performance of a GaN PA. The figures of merit considered for this purpose are the normalized mean-square error (NMSE), for the in-band distortion, the adjacent channel power ratio (ACPR), for the out-of-band distortion, and the power added efficiency (PAE). Two GaN PAs are tested: a Class-A and a Class-AB.


Power Amplifier Design using Discrete GaN Transistors - Extending Frequency Bandwidth

Lord Ali
Surface Technology International Ltd

The design of power amplifiers for narrow frequency bandwidths is well understood and many designs, papers and application notes are available to support this. Proven techniques are utilised in order that these designs can be easily realised. But, when a design requires the bandwidth to be extended, such as that presented in this example from 2 to 6GHz, certain device parameters are compromised. The power efficiency may be degraded as well as the overall gain. The required output power may not be delivered and device stability may also be compromised as well as device linearity. In this paper, a design is presented, where the frequency bandwidth has been extended between 2 to 6GHz. The simulations performed and techniques used during the design process are discussed, in order to present a stable final design, with a focus on delivering the maximum available output power for the given bandwidth. But more importantly what compromises have had to be made in order for this to occur. The final design will be tested using CW signals.


RF Performance Potential of Diamond Field Effect Transistors

Stephen Russell, Salah Sharabi, Alexandre Tallaire, and David A. J. Moran
Universities of Glasgow and Paris

Diamond possesses a range of unique properties that make it of interest as a robust semiconductor platform for the production of high power and high frequency RF devices. Such properties include a large bandgap of 5.5 eV, intrinsic electron and hole mobility ~ 3000 cm2/V.s and an extremely high thermal conductivity of 300 W/m.K.

Despite diamond’s semiconductor potential, progress towards the production of mature, high performance diamond electronic components has predominantly been limited by the difficulty associated with doping. Substantial progress has been made in recent years however towards the development of high frequency devices such as field effect transistors.

We will present an overview of progress in the area of diamond RF device performance and show results achieved at the University of Glasgow that demonstrate the highest frequency performance yet achieved for a diamond-based transistor (fT = 53 GHz). These results shed light on the intrinsic high frequency limitations of this technology and highlight areas of research that must be prioritised moving forward to advance its maturity and performance potential.


The Design and Evaluation of a Plastic Packaged Single-Chip FEM for 28GHz 5G

Stuart Glynn, Robert Smith, Liam Devlin, Andy Dearn, Graham Pearson
Plextek RFI

The Front End Module (FEM) will be an essential component in future mm-wave 5G systems. It consists of a PA, LNA and transmit/receive switch to allow time division duplex (TDD) operation and must demonstrate high linearity in transmit mode and low noise figure in receive mode. This paper describes the design, realisation and evaluation of an FEM MMIC for the 28GHz 5G band (27.5 to 28.35GHz). The part was developed on a 4V, 0.15µm enhancement mode GaAs pHEMT process and so only positive supply voltages are required. The compact, low-cost 5mm x 5mm plastic overmolded QFN package means that the MMIC is suitable for the high volume and low cost manufacturing that will be required for 28GHz 5G systems.

The transmit path produces an output power around 20.2dBm at 1dB compression with a PAE of around 20%. When backed off to an IMD3 point of -35dBc the measured PAE is 6.5%, an impressive result that demonstrates simultaneous linear and power-efficient operation.  The measured receive path gain is around 13.5dB with a noise figure of around 3.3dB. The receive path also demonstrates impressive linearity for a modest power consumption of just 40mW.


The Dual-Input Doherty Amplifier

Gareth Lloyd
Rohde & Schwarz

The Doherty Amplifier, since its invention almost 100 years ago, has enjoyed something of a renaissance in the last 20 years. Proliferation of digitally modulated signals, increasingly noise like in their signal statistics, along with semiconductor device technology advancements, have fuelled this rediscovery process.

As Engineers try to squeeze remaining drops of performance out of their Doherty designs, there's an increasing awareness that there are significant gains to be made departing from the industry standard 3dB/90deg. fixed RF input split network.

By measuring the Doherty amplifier as a dual-path/dual-input device, and stimulating those two inputs with a range of different signals, it is possible to identify best performance and to understand the performance trade-offs and sensitivities.

Armed with that information, the Engineer is then empowered to make the best design decision. The presentation will be accompanied by a live, automated, measurement demonstration.


Two Port Cylindrical Cavity Enables Efficient Power Delivery- Through Power Combining & Scaling in a Solid State System

Kauser Chaudhry and Dr Jonathan Lees
Cardiff University

There is a growing interest in using solid-state, power transistor based technology as an alternative to traditional magnetron-based power generation in microwave cooking and heating. The  power available from a single solid-state power amplifier ‘module’ is generally limited by the maximum power rating of the transistors used however, and in most cases, a single module will be insufficient. In such instances, power combining becomes a key requirement, and at power levels greater than 250 Watts, this becomes a difficult task to accomplish in a cost effective way at the printed circuit board level. The use of the microwave cavity itself for direct power combination offers a possible solution, but it requires the use of multiple ports and feed structures.

The cavity’s operational impedance environment is a function of loading conditions, where each of the power amplifier modules will experience potentially high or even very high voltage standing wave ratio’s (VSWR) and must operate reliably and without performance degradation. Monitoring, capturing, managing and manipulating the impedance environment at each of the excitation ports is a key requirement in ensuring safe, reliable and efficient operation. For solid-state solutions to be viable in mass-market applications, there is a need to reduce the PA module cost to the point where they can be competitive with the magnetron based systems. Removing the need for the traditional circulator will help achieve this goal, however high VSWR and device reliability remains a concern. In this paper, the impact on device reliability in a 2-port systems is considered and presented.



EXHIBITION

Companies booking two or more delegate places are able to take part in the commercial exhibition that accompanies the conference. Please note: there is a maximum of 20 exhibition tables at each meeting, these are offered on a first come basis. Booking two delegate places does not guarantee an exhibition space, please email exhibition@armms.org to check availability and reserve and exhibition space.


SPONSORSHIP

The ARMMS RF and Microwave Society would like to thank Interlligent UK for sponsoring the April 2018 meeting:


CALL FOR PAPERS

Contributions are invited with an emphasis on RF and microwave design, research, testing and associated subjects. An oral presentation will be made at the meeting and a written paper will be required for publication in the society digest, which is distributed to delegates at the meeting. Prospective speakers are requested to submit a title and a short abstract to the technical coordinator (see above) as soon as possible.

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