Rsearch Summary:
The Electromagnetics Laboratory staff has extensive experience in the design, characterization, and use of antennas. A full range of radiators is the topic of a long-standing research tradition at MSU. We have investigated and designed antennas for use in a variety of applications including antennas that account for the impact of installation on an aircraft, automobile, or other vehicle.
On-going research at MSU is focusing on the design, characterization, and performance testing of conformal and self-adapting antennas. MSU is a leader in the analysis and design of complex wide bandwidth conformal antennas. In addition, MSU is pioneering the development of novel new intelligent self-adapting antennas that have the capability to adjust its property based on local conditions (e.g. installation location, element failure, etc.)
Tunable, Reconfigurable and Miniaturized Antennas:
Tunable and reconfigurable antennas are antennas whose performance can be changed by changing the electrical inputs to the antenna and not necessarily changing the antenna itself. Antenna performance could be the operational frequency range, radiation pattern, reflection coefficient, and/or polarization.
Tunable antennas refer to antennas who have one or more antenna performance characteristics, often just the operational frequency is investigated, that can be changed, or tuned, within some continuous range. Such behavior is often achieved by the thoughtful placement of slots, pins, and varactor diodes to modify the effective electrical length or width of the antenna. Reconfigurable antennas differ from tunable antennas as they modify behavior within a discrete, and not continuous, range and tend to uses switches.
As an example or research done in this area from our group, a reconfigurable patch antenna array is shown below [1]. Most work on tunable or reconfigurable antennas is focused on making a single antenna design that can be tuned/reconfigured. Our group was the first to investigate making not any one individual antenna element tunable/reconfigurable, but an entire array reconfigurable.
Reconfigurable patch antenna array as investigated in [1]: (A) 2x2 5 GHz array (layout for the RF shorted design but left unconnected),
(B) single patch antenna, (C) 2x2 5 GHz array connected with hard shorts, (D) 2x2 5 GHz array connect with RF shorts (3pF capacitors),
and (E) ANSYS HFSS simulated reflection coefficients for all four structures.
A tunable antenna our group has worked on is a pixelated dual-band folded monopole [6]. Here varactor diodes are used to tune a metamaterial grid where the pixels in the grid were determined using a genetic algorithm (GA) to meet certain performance goals. This antenna as well as the circular patch antenna shown below are miniaturized, or made electrically small, by using meta-material inspired designs.
(A) Miniaturzied circular patch antenna ,(B) same miniaturzied patch showing a metamaterial enhancement, (C) miniaturized patch antenna tunability results,
(D) pixelated folded monopole, (E) pixelated folded monopole integrated in a system, and (F) results from tuning the pixelated monopole.
Self-Structuring Antennas:
Self-structuring antennas (SSAs) are antennas where the electrical structure of the antenna is changed given the electrical inputs to the antenna. These types of antennas were first investigated by our research group and have been well investigated by current and former members. Below shows a (A) block diagram of an SSA system and a (B) diagram of an SSA template [2]. These antennas can be self-adapting and have 2n antenna states. Properties of these antennas are unknown and GAs are used to search for their state in real time to meet performance requirements. The base patent for these antennas is held by MSU as well as 2 subsequent patents.
(A) SSA system block diagram and (B) SSA template diagram.
SSAa have been commercialized by Monarch Antenna, formed in 2007, as a Delphi spin-off who holds a license to MSU's SSA patents. Several major projects related to SSAs have been handheld and laptop communication using Zigbee, structure monitoring, and a NASA return-to-moon spacesuit antenna. In (C) of the figure below, an automotive backlight antenna (Delphi, left) and a low-profile vehicle antenna (army STTR, right) are shown.
(A) Example of a fabricated SSA, (B) SSA use in NSA space suit, and (C) SSA use in a car.
Recent Related Publications:
[1] J. A. Byford, K. Y. Park, P. Chahal, and E. J. Rothwell, “Frequency reconfigurable patch antenna array,” Electron. Lett., vol. 51, no. 21, pp. 1628–1630, 2015.
[2] Coleman, Christopher Mark, et al. "Self-structuring antennas." IEEE Antennas and Propagation Magazine 44.3 (2002): 11-23.
[3] Tayebi, Amin, et al. "Dynamic beam shaping using a dual-band electronically tunable reflect array antenna." IEEE Transactions on Antennas and Propagation 63.10 (2015): 4534-4539.
[4] Özdemir, Tayfun, et al. "Frequency tunable antenna for LTE (4G) handsets operating in the 2.3–2.7 GHz global roaming band." 2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE, 2015.
[5] Frasch, Jonathan L., and Edward J. Rothwell. "A three dimensional extension of the self-structuring antenna to improve beam steering." Radio Science Meeting (Joint with AP-S Symposium), 2015 USNC-URSI. IEEE, 2015.
[6] Myers, Joshua C., et al. "A Multilayered Metamaterial-Inspired Miniaturized Dynamically Tunable Antenna." IEEE Transactions on Antennas and Propagation 63.4 (2015): 1546-1553.