Due to the inherent shortcomings of existing antenna technologies (such as array coupling, reconfigurable difficulty, poor RF stealth performance, etc.) or the inability to meet the application requirements under new forms (implantable devices, onboard applications, etc.) A new type of antenna launched a series of studies - liquid antenna, plasma antenna, metamaterial antenna, nano-ray antenna, implantable antenna, foldable antenna.

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Research Progress of New Antenna Technology
Written By Calio Huang
Due to the inherent shortcomings of existing antenna technologies (such as array coupling,
reconfigurable difficulty, poor RF stealth performance, etc.) or the inability to meet the
application requirements under new forms (implantable devices, onboard applications, etc.) A
new type of antenna launched a series of studies - liquid antenna, plasma antenna, metamaterial
antenna, nano-ray antenna, implantable antenna, foldable antenna.
1. Liquid antenna
The emergence of the liquid antenna, breaking the traditional concept of the solid antenna, its
unique properties and advantages for the antenna theory and application have opened up a new
world. The liquid antenna refers to the solid liquid material used for replacing the solid antenna
radiation unit with the liquid and constitutes the antenna with the liquid as the radiation unit.
Compared with the traditional solid state antenna, the liquid antenna has high plasticity and
reconfigurability, low radar cross section, Can effectively improve the electromagnetic coupling
characteristics, has great potential applications in wireless communications.
Liquid Antenna refers to the use of conductive liquid to replace the ordinary antenna radiating
elements used in the composition of the antenna. Liquid Antenna There are ionic liquids for the
radiation unit, but also the use of liquid metal or liquid crystal material. Compared with the
conventional metal antenna, the liquid antenna can be changed into various shapes without
applying pressure, bending does not lead to material fatigue, and even self-repairing and
eliminating air gaps after being destroyed, and has a huge Advantage and development
prospects.
The many advantages of liquids provide us with new ideas for antenna design. Liquid or liquid
metal Good structural flexibility provides two major advantages for antenna manufacturing.

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(1) The stability of the antenna structure. It seems unreasonable to show the stability by the
liquid, but when the antenna can work in the liquid or liquid metal state, we no longer have to
worry about the explosion scenes in the movie, and the liquid antenna will be shocked This
scenario will be revolutionary in just seconds and back to work.
(2) The liquid provides great convenience for the reconstruction of the antenna. We can change
the structure of the antenna by controlling the shape of the liquid so that the antenna can work
in different frequency bands and is very flexible. This is a small communication device for the
antenna design encountered in the small space, cable complexity and other problems provide a
solution.
2. Plasma antenna
Plasma antenna is a gaseous reconfigurable antenna, the use of ionized inert gas plasma instead
of the traditional metal antenna to launch or receive electromagnetic waves. Due to the inherent
properties of plasmas, plasma antennas have outstanding stealth properties that do not reflect
normal radar waves even in operating conditions. Moreover, the broadband plasma antenna,
reconfigurable performance is particularly suitable for active stealth technology such as spread
spectrum, frequency hopping.
The main structure of a plasma antenna is an insulating medium enclosed by an inert gas
chamber (such as a quartz glass tube). When one end (usually the bottom) of the cavity is
coupled with radiofrequency energy, the inert gas begins to ionize to generate plasma. As the
incident energy increases, the entire cavity can be gradually filled by the plasma cylinder. Due to
the electrical conductivity of the plasma, the plasma cylinder bound to the dielectric cavity can
emit and receive electromagnetic waves as a metal antenna.
Due to the unique physical properties of plasmas, plasmas have many advantages over metallic
antennas:
a) Incognito characteristics. When the antenna is off, the plasma antenna system has almost no
metal parts, the radar cross section will be very small, to achieve stealth in electronic warfare
and improve survivability.
b) Reduce the mutual coupling. In the array antenna, mutual coupling between the
non-operating unit and the working unit is hardly generated, which greatly reduces the
interference among the array units and improves the performance of the antenna.
c) Radiated components are electrically controlled. The physical structure of the antenna does
not need to be changed. The parameters such as the frequency, the bandwidth and the
directivity of the antenna can be dynamically reconstructed by changing the physical
parameters such as the gas composition and the electron concentration of the plasma,
thereby realizing the antenna control.
d) Solve the problem of high power. The use of high-voltage pulsed plasma antenna can solve
the problem of high power in the current design of microwave antenna and avoid the
situation that the high-voltage burned the feeder and the antenna.
e) Compact structure. The discharge tube in the antenna can be a high-strength quartz glass
tube, which is lighter in weight and smaller in size than the metal antenna, and improves the
assembly efficiency.
Plasma antenna main technical problems

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The biggest technical problem plaguing the plasma antenna research is difficult to achieve the
performance index of ordinary metal antenna. Plasma antenna prototype developed according to
foreign public literature, the gain is usually lower than the same specifications of the metal
antenna about 20 decibels, basically no practical value.
In addition, due to the plasma antenna coupling and matching methods and metal antenna is
completely different. In addition to feeding the normal microwave signal to the plasma antenna,
it is also necessary to feed excitation power at the bottom to form and maintain the plasma
cylinder. The two RF power needs to be connected to the same coupling cavity at the bottom of
the antenna, which will not only bring serious mutual interference, but also the matching
efficiency is very low. Therefore, the plasma antenna is not only difficult to achieve the desired
gain, but also the power consumption required to excite the plasma to form an antenna is also
very alarming.
3. Metamaterial antenna
Metamaterial (metamaterial), in which the Latin root "meta-" means "beyond, alternative" and
so on, so the general literature is given artificial electromagnetic material is defined as "the
extraordinary physical properties of natural materials do not have the artificial composite
structure Or composite material. "That is everyone relish the" metamaterials. " Meta material has
the unique nature of the original material does not have, of which there have been many new
physical phenomena. At present, the research on the physical properties of Meta materials and
their application in the field of directional radiation high performance antenna, electromagnetic
stealth, space communication, detection technology and new terahertz band functional devices
have become the research hotspots in the fields of international physics and electromagnetics.
Artificial electromagnetic materials (Metamaterials, Meta material) is a man-made structure of
cells arranged in a specific manner to form a special electromagnetic properties of artificial
structure of the material. At present, there are several kinds of metamaterials that are currently
under study, such as left-handed materials, compound left / right hand transmission lines,
photonic crystals, invisible clothing and electromagnetic black holes.
The artificial electromagnetic metamaterials are proposed to control the range of the negative
refractive index bandwidth by reasonably designing the structural unit of metamaterials to make
corresponding resonance to electric and magnetic fields. By reasonably integrating the
metamaterial unit and the antenna, the gain and the orientation of the antenna can be improved
without greatly changing the antenna structure.
4. Implantable antenna
The continuous development of electronic circuit integration system and miniaturization antenna
technology make it possible to use wireless energy transmission and data telemetry in wireless
biomedical devices and show great application prospect. This development has contributed to a
variety of applications in biomedical diagnostic and therapeutic applications of wireless energy
and data telemetry, including human pacemakers, body area network devices, wireless sensing
for detecting glucose, pH, blood pressure, temperature, etc. Equipment development and design.
Due to the strong coupling of human tissue with wireless energy and data transmission
equipment, which has a strong impact on the electromagnetic properties of wireless devices,
how to design wireless medical devices accurately is a key problem to be solved urgently in the

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field of electronic science and bioelectromagnetics.
In implantable wireless medical research, there are many problems to be solved urgently. Among
them, how to accurately consider the influence of human environment on the working
performance of implantable devices and the energy supplement of wireless implant devices are
the two core problems in this field.
5. Nano-optical antenna
Nano-optical antennas are new concepts in physical optics. Similar to radio-wave antennas and
microwave antennas, they convert the freely propagating energy into local energy. However,
unlike current-driven, far-field-current energy conversion schemes that operate on conventional
antennas, nano-optical antennas work based on the localized plasmon excitation of metal
nanoparticles at the optical frequency due to their particular photovoltaic surface properties.
The significant difference between the antenna and the RF antenna is mainly reflected in two
aspects. Firstly, in the optical band, the model of the ideal electrical conductor is not suitable for
the optical band because of the high loss of the antenna. Secondly, in the nanometer range, The
existence of excitons and other physical phenomena, especially in the sub-wavelength field
limitations, antenna characteristics showed a clear difference.
Nano-optical antennas can not only control the light field in the subwavelength scale but also
effectively enhance the local field intensity. Therefore, they are widely used in the fields of
photodetection, sensing, heat conduction, solar cells, and spectrum analysis.
6. Foldable antenna
Antenna, as a key component of the wireless communication system, has become an important
technology devoted to the military field in various countries. In the field of space, the connection
between space, space, and ground cannot be separated without the high gain antenna. On the
ground, long-range combat missions to do the task, platoon or solo soldier wants to get in touch
with the command is also inseparable from the high gain antenna. For mobile units at this time,
the weight, ease of erection has become another antenna, antenna in the long-range combat
another important performance indicators. The reflector antenna belongs to a kind of
high-performance high-gain antenna. So far this type of antenna has been widely applied in the
fields of satellite, airborne radar, ground station, mobile communication station and vehicle
station. The conventional reflector antenna has many disadvantages, such as heavy weight, high
cost and difficulty of erection, which are not suitable for the flexibility of the communication
equipment in the future battlefield. Therefore, the foldable reflector antenna has become the
best choice for satellite communications and deep space communications.
In satellite applications, due to space limitations of the spacecraft's fairing, the antenna must be
folded and housed in the satellite cover during launch. When the satellite orbit, the antenna and
then rely on its own power source automatically launched, which is the so-called foldable
reflector antenna
(1) The solid surface reflection surface
Most solid-surface reflector antennas consist of a hub and a rigid plate. Solid surface reflector
material selection of metal plates or carbon fiber reinforced plastics (CTFR). As the plate can be
processed into an ideal paraboloid, so the biggest advantage of this reflective surface is the
higher accuracy.

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Such antennas have the disadvantages of heavy weight, high cost, and small shrinkage ratio and
are limited to deployable antennas with smaller dimensions, so their applications are less.
(2) Inflatable reflective surface
The main components of the inflatable antenna are made of thin film. In the pre-launch because
there is no inflatable, it can be compressed into a small volume and stored in the box; into the
track, inflated and expanded. The surface is cured by solar radiation into the desired curved
surface shape. The advantage of this antenna is shrinkage is relatively high, lightweight, low
processing costs. Although the diameter of the reflector of the air-filled antenna can be made
large, it is difficult to obtain a high-precision reflective surface, so its operating frequency is low.
(3) Mesh reflective surface
Mesh reflective surface is the rigid solid surface reflective surface replaced by metal mesh,
lightweight, large shrinkage ratio, wide frequency band, waveguide feeding system can work in
high-power, and easy to achieve multi-beam, multi-band, multi-polarization As well as
electro-scan and electronically controlled beam widths, suitable for high-resolution small satellite
SAR antennas.
Mainly due to the following three factors:
(1) The mesh adjustment, with the increase of the caliber and the increase of the working
frequency band, the requirements on the accuracy of the reflector are also getting higher
and higher, and the analysis and adjustment technology of the reflection surface still needs
to be perfect.
(2) Mesh measurement, mesh measurement technology is relatively backward, the test less
efficient.
(3) processing technology to mesh reflector antenna, for example, stainless steel nickel-plated
and gold-plated molybdenum wire in the production of two kinds of networks there is still a
great technical difficulty, resulting in a substantial increase in manufacturing costs.