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Dr James Kelly

Lecturer in Microwave Antennas
MEng (Hons), PhD, PG Cert ULT, MIEEE
+44 (0)1483 689480
08 CII 01
Wednesdays 1-2pm


Areas of specialism

Microwave Antennas

University roles and responsibilities

  • Additional Learning Support (ALS) Tutor for Electronic Engineering


Research interests

Research projects

My teaching

My publications


Idris IH, Hamid MR, Jamaluddin MH, Rahim MKA, Kelly JR, Majid HA (2014) Single-, dual- and triple-band frequency reconfigurable antenna, Radioengineering 23 (3) pp. 805-811
The paper presents a frequency reconfigurable slot dipole antenna. The antenna is capable of being switched between single-band, dual-band or triple-band operation. The antenna incorporates three pairs of pindiodes which are located within the dipole arms. The antenna was designed to operate at 2.4 GHz, 3.5 GHz and 5.2 GHz using the aid of CST Microwave Studio. The average measured gains are 1.54, 2.92 and 1.89 dBi for low, mid and high band respectively. A prototype was then constructed in order to verify the performance of the device. A good level of agreement was observed between simulation and measurement.
Borja A, Kelly JR (2015) Reconfigurable Microwave Circuit Based on a Single Triangular Microstrip Patch, 2015 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING pp. 2253-2254 IEEE
Kelly JR, Borja AL (2014) Hardware block for use in programmable microwave function arrays, Electronics Letters 50 (15) pp. 1076-1077
Ultimately, the research presented will lead to the development of a microwave integrated circuit that is analogous to a field programmable gate array. An early step towards the development of this technology is presented. Specifically, a 3-port device, based on a single resonant element, namely a microstrip square patch, is described. The device operates simultaneously as a filter and an antenna. Filter performance is obtained between ports 1 and 2. Antenna performance is obtained on port 3. © 2014 The Institution of Engineering and Technology.
Wang Z, Kelly JR, Hall PS, Borja AL, Gardner P (2014) Reconfigurable parallel coupled band notch resonator with wide tuning range, IEEE Transactions on Industrial Electronics 61 (11) pp. 6316-6326
This paper presents a new form of reconfigurable band notch resonator with a wide tuning range. The whole structure consists of a through line and two parallel coupled resonators. This paper presents an accurate lumped element equivalent circuit for the parallel coupled resonator. The mechanism giving rise to the wide tuning range is also investigated. The first harmonic of the fundamental stop-band is analyzed and compared with that of the varactor-coupled resonator. Measurement results show that the stop-band of the filter can be tuned from 0.6 to 4.0 GHz. This is achieved by varying the capacitance of two pairs of varactor diodes. The stop-band tuning range is restricted by the capacitance variation which can be achieved using the varactor diode. The potential tuning range of a filter based on this resonator is greater than one decade. © 1982-2012 IEEE.
Wei JD, Chen XZ, Kelly JR, Cui YZ (2015) Blast furnace stockline measurement using radar, IRONMAKING & STEELMAKING 42 (7) pp. 533-541 MANEY PUBLISHING
Kelly JR, Borja A (2015) Reconfigurable Microwave Circuit Based on Three Triangular Microstrip Patches, 2015 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING pp. 2251-2252 IEEE
Chen G, Xiao Pei, Kelly James, Li B, Tafazolli Rahim (2017) Full-Duplex Wireless-Powered Relay in Two Way Cooperative Networks, IEEE Access 5 pp. 1548-1558 IEEE
This paper investigates a full duplex wirelesspowered two way communication networks, where two hybrid access points (HAP) and a number of amplify and forward (AF) relays both operate in full duplex scenario. We use time switching (TS) and static power splitting (SPS) schemes with two way full duplex wireless-powered networks as a benchmark. Then the new time division duplexing static power splitting (TDD SPS) and full duplex static power splitting (FDSPS) schemes as well as a simple relay selection strategy are proposed to improve the system performance. For TS, SPS and FDSPS, the best relay harvests energy using the received RF signal from HAPs and uses harvested energy to transmit signal to each HAP at the same frequency and time, therefore only partial self-interference (SI) cancellation needs to be considered in the FDSPS case. For the proposed TDD SPS, the best relay harvests the energy from the HAP and its self-interference. Then we derive closed-form expressions for the throughput and outage probability for delay limited transmissions over Rayleigh fading channels. Simulation results are presented to evaluate the effectiveness of the proposed scheme with different system key parameters, such as time allocation, power splitting ratio and residual SI.
Uchendu Iyemeh Egwenike, Kelly James (2017) Ultrawide isolation bandwidth Compensated Power Divider for UWB applications, Microwave and Optical Technology Letters 59 (12) pp. 3177-3180 John Wiley & Sons
This article presents design analyses for achieving an ultrawide isolation bandwidth compensated power divider (CPD). The CPD offers improvement in complexity, size and insertion when compared with alternative techniques for increasing isolation bandwidth. A prototype CPD with -15dB isolation bandwidth of 114% was fabricated and measured to validate the analyses.
Wang Z, Hall P, Kelly JR, Gardner P (2017) Wideband Frequency Domain and Space Domain Pattern Reconfigurable Circular Antenna Array, IEEE Transactions on Antennas and Propagation 65 (10) pp. 5179-5189 IEEE
This paper presents a wideband circular antenna array with a frequency domain and space domain reconfigurable radiation pattern. A wideband circular array antenna is designed with omni-directional radiation pattern, in azimuth direction, throughout the whole frequency band. The antenna array consists of eight TEM horn antennas. The antenna array exhibits an omni-directional azimuthal radiation pattern when all eight ports are excited with signals of the same magnitude and phase. The antenna array is fed through eight reconfigurable bandstop filters and a power splitter. This enables it to provide an omni-directional azimuthal pattern along with a single directional pattern null in a given spatial direction and at a certain frequency. Both the spatial direction and the frequency can be altered. The antenna works from 0.8 GHz to 3.0 GHz. The antenna array will be useful in combating interference in wideband communication systems. It will also be of value in surveillance military applications.
da Costa I, Filgueiras H, Kelly J, Arismar Cerqueira S, Xiao P (2018) Mechanical Beam Steering Circular Patch Antenna, EuCAP 2018 Proceedings
This work reports preliminary results and a
prototype of an innovative mechanical beam steering circular
patch antenna for 5G indoor cellular access networks with sub6
GHz operation. The beam steering is achieved using 18 screws
installed around the circular patch radiator, working as a
reflector by proper managing the screws position and height.
The new antenna can steer its main beam over 360º in azimuth
plane and from -30º to 30º in the elevation plane with gain up to
8.01 dBi at 4.6 GHz.
Allayioti Marion, Kelly James R., Mittra Raj (2018) Beam and Polarisation Reconfigurable Microstrip Antenna Based on Parasitics, Microwave and Optical Technology Letters 60 (6) pp. 1460-1464 Wiley
This paper presents a dual-notch polarization and beam reconfigurable microstrip antenna. It uses parasitics which incorporate switches to steer its beam away from boresight and dual-notches which, again, incorporate switches to reconfigure between linear and circular polarization. The antenna is a low profile microstrip patch antenna which only uses a single feed, allowing it to be compact and simple in terms of its structure.
Kelly J.R., Alqurashi K. Yahya, Filgueiras H.R.D., da Costa I. F., Cerqueira S. Jr. Arismar, Xiao Pei, Chen Zhe, Wong Hang (2018) Millimeter Wave Beam Steerable/Reconfigurable Liquid Metal Array Antenna, Proceedings of ICEAA - IEEE APWC - FEM 2018 Institute of Electrical and Electronics Engineers (IEEE)
Users within mobile networks require ever increasing data rates. However, the frequency spectrum, reserved for mobile networks, is highly saturated. The millimeter wave spectrum, by contrast is relatively under utilised. Nonetheless, this area of the spectrum suffers from higher propagation losses, necessitating the use of highly directional antennas. To support mobility these antennas require beam steering capabilities. For several applications wide beam scanning capability is required. A valuable approach for increasing the beam scanning range is to use element factor plus array factor control [1]. Although several authors have presented designs based on this approach the lobe performance of those antennas is generally quite poor. In this paper we seek to address that issue.
Borja A. L., Kabiri Yasin, Belenguer A., Kelly J. R. (2018) Programmable Multi-Functional RF/Microwave Circuit for Antenna and Filter Operation, IEEE Transactions on Antennas and Propagation 66 (8) pp. 3865-3876 Institute of Electrical and Electronics Engineers (IEEE)
This paper describes a multi-functional microwave
device that can be reconfigured to behave either as a filter or an
antenna. The device is based around a single resonant element,
referred to as a building block element that is connected to 4
ports. The resonant element is a microstrip square patch
working in the 2.45 GHz unlicensed Industrial Scientific and
Medical (ISM) band used for IEEE 802.11 WiFi. The proposed
building block is simple in its design and construction. The paper
also presents devices composed of three building blocks, which
can realize more complex filtering and antenna mode
performance. In addition, PIN diodes have also been
incorporated into the devices in order to facilitate electronic
control. Measured results, pertaining to fabricated prototypes,
show that filter and antenna operation can be achieved, in the
same device at a frequency of around 2.45 GHz with acceptable
insertion loss and efficiency. In the future, it is anticipated that
this could lead to a new paradigm, namely a device that is
analogous to a field programmable gate array (FPGA) operating
in the microwave frequency regime.
Kelly James R., Tanha Mandana Ardeshir (2018) Reconfigurable 26GHz Liquid Metal Antenna Capable of Low Loss Continuous Beam Steering, Proceedings of the 2018 IEEE Conference on Antenna Measurements and Applications, 3-6 September 2018, Västerås, Sweden Institute of Electrical and Electronics Engineers (IEEE)
For this first time this paper presents a concept
for a high gain millimeter wave beam steerable antenna that
supports continuous steering over a 360° scan range and
promises to yield extremely low power losses. The concept does
not require phase shifters which suffer from high insertion
losses at millimeter wave frequencies or mechanical movement,
in the conventional sense, which has the disadvantages of poor
reliability and slow response times due to high inertia.
Millimetre wave beam and polarization reconfigurable antennas for future wireless communications
are investigated in this thesis. The millimetre wave frequency spectrum
has recently attracted large attention from researchers and the industry of wireless communications.
Millimetre wave frequencies is considered to be the frequency spectrum
between 30 GHz and 300 GHz. However, the industry considers the spectrum above 10
GHz as millimetre wave, due to the fact that it shows similar propagation characteristics
with the spectrum above 30 GHz. The aforementioned spectrum of frequencies
offers a lot of advantages compared to lower frequency spectrum, due to the fact that
it offers large and mostly unexploited bandwidths. The need for very high data rates,
in future wireless communications, increases the need for bandwidth. Millimetre wave
frequencies can be used to fulfill future bandwidth demands.
Although millimeter wave frequencies offer several advantages and good potential for
future wireless communications, they also impose several challenges. This thesis discusses
the need for highly directive and beam reconfigurable antennas for such high
frequencies. It also discusses how an antenna design can benefit from being circularly
polarised for several wireless communication applications and how antennas for future
wireless communications must be able to reconfigure several parameters, without compromising
the performance, cost and size, giving the
exibility to a wireless terminal
to operate in several different modes.
This thesis proposes novel reconfigurable antennas for portable devices, which can be
used at millimetre wave frequencies, and which offer high gain, wide steering range, low
scan loss and multi-parameter reconfigurability; essential characteristics that antennas
designed for future wireless communications should offer.
Hill Timothy A., Kelly James R. (2019) 28 GHz Taylor Feed Network for Sidelobe Level Reduction in 5G Phased Array Antennas, Microwave and Optical Technology Letters 61 (1) pp. 37-43 Wiley
This paper presents a design procedure for a phased array feed network. The procedure is validated by
designing and fabricating a set of 28 GHz 8-element beam steerable antennas. Within the feed, a
Taylor n-bar amplitude taper is implemented using unequal power dividers. At boresight, the taper
reduced the sidelobe level by 2.84 dB to -15.2 dB. Beam steering from 0° ? 48° is achieved using
meanders. An empirical formula for the meander widths is proposed, enabling independent control of
amplitude and phase. Empirical formulae for the initial parameters of the unequal dividers are also
proposed. The wide transmission lines in this feed network are compatible with low-cost PCB
fabrication techniques.
Kabiri Yasin, Borja Alejandro L., Kelly James, Xiao Pei (2019) A technique for MIMO antenna design with flexible element number and pattern diversity, IEEE Access pp. 1-1 Institute of Electrical and Electronics Engineers (IEEE)
This paper presents a new technique for designing Multiple Input Multiple (MIMO) Output antennas having pattern diversity. Massive MIMO is expected to form part of 5G communications and will require antennas having a very large number of elements. However, due to the size limitation, it is highly challenging to preserve high isolation between the ports. Pattern diversity technique are also highly desirable and can facilitate MIMO systems with diversity gain. However, achieving that within a compact antenna where there is limited space between the elements is also challenging. In this paper a technique is introduce and applied to 4-element and 6-element MIMO antennas. This technique can improve the isolation between the ports and it also yields pattern diversity for MIMO antennas with various numbers of elements. The technique is verified via experimental measurement.

Additional publications