Design of Prototype NVIS Spider Antenna for HF Tactical Radio Communication

The use of near vertical incidence skywave (NVIS) propagation for HF radio communications somewhat beyond the groundwave range has assumed increasing importance years, particularly when no artificial means of radio relay is available. When tracing its history however there has been a tendency to assume that it first made its appearance in military communications during the Vietnam war in the late 1960s. Certainly, in that conflict considerable use was made of NVIS techniques and the basic characteristics of the antenna systems intended to launch it were subjected to exhaustive measurement. However, the genesis of what is now almost universally referred to as NVIS can be traced back at least to the Second World War when both the American and British forces used it-but never referred to it by that acronym.

We have combined the relatively mature numerical technique of the moment method computer modelling with a powerful, though less well-known, method of antenna synthesis which is based on the procedure of characteristic modes (CM), to both analyse and then to design optimum antenna systems for vehicular NVIS applications. Regardless of the maturity of an analytical technique however, the acid test of its accuracy can only be determined by means of a series of careful measurements of the performance of the candidate antennas when mounted on their appropriate host vehicle. This paper presents both analytical and experimental results for the existing whip antenna, at various angles of inclination, as well as for the vertically orientated loop, which has been proposed as a more appropriate antenna for this application. In addition, a loop configuration with an unconventional feed system is analysed and shown to provide improved performance.

SummaryAlthough many physical layer solutions have appeared for remote sensors and Internet of things during the recent years, none of them is suited to very remote sensors in areas away from any mobile operator coverage. In that case, a solution on the basis of near vertical incidence skywave (NVIS) with reflection in the ionosphere may be very attractive. Using NVIS, no line of sight is needed and the coverage is much bigger than any other system operating in either the very high frequency (VHF) or ultra high frequency (UHF) band. In this paper, we present a new transmission scheme for very remote sensors using the NVIS transmission technique.

The method of characteristic modes is used for the design of vehicular antennas for near vertical incidence skywave (NVIS). The technique allows the treatment of any vehicle-antenna combination as one, computing a unique set of characteristic, orthogonal currents and associated fields that may be optimized. >

In high-frequency (HF) frequency band radio waves can propagate over a few thousand kilometers owing to the reflection from ionosphere. In doing so, the ionosphere channel constitute an alternative to satellite communications when smaller data rates (bandwidths) are of interest. The entire range of distances can be covered if an antenna system supports all three modes of propagation: near vertical incidence skywave (NVIS), long range skywave and surface wave. Design of antennas for NVIS mode is the most challenging since they have to operate over the low end of HF frequency band. Due to size constrains, these antennas are electrically small, and thus they are inherently narrowband and have small radiation resistance. In addition, antenna pattern should have maximum at zenith, though there is no stringent requirement for the signal polarization.

Every year more interest is focused on high frequencies (HF) communications for remote sensing platforms due to their capacity to establish links of more than 250 km without a line of sight and due to them being a low-cost alternative to satellite communications. In this article, we study the ionospheric ordinary and extraordinary waves to improve the applications of near vertical incidence skywave (NVIS) on a single input multiple output (SIMO) configuration. To obtain the results, we established a link of 95 km to test the diversity combining of ordinary and extraordinary waves by using selection combining (SC) and equal-gain combining (EGC) on a remote sensing platform. The testbench is based on digital modulation transmissions with power transmission between 3 and 100 W. The results show us the main energy per bit to noise spectral density ratio (Eb/N0) and the bit error rate (BER) differences between ordinary and extraordinary waves, SC, and EGC. To conclude, diversity techniques show us a decrease of the power transmission need, allowing for the use of compact antennas and increasing battery autonomy. Furthermore, we present three different improvement options for NVIS SIMO remote sensing platforms depending on the requirements of bitrate, power consumption, and efficiency of communication.

A popular technique for providing non line-of-sight coverage in mountainous or urban terrain is high frequency (HF) radio near-vertical incidence skywave (NVIS) mode. In NVIS operation, HF energy is directed vertically, and is refracted from the ionosphere to return nearly vertically to the area surrounding the transmitter; this nicely avoids nearly all obstacles. Direction finding versus a NVIS transmitter is also made difficult to the extent that the energy is directed vertically and groundwave is suppressed. However, NVIS operation requires the presence of substantial ionization in the ionosphere directly overhead the transmitter, so some concern is warranted about the effectiveness of NVIS operation during a solar minimum. In this paper, we present measurements and analysis of a multi-year NVIS experiment conducted during the current minimum of the sunspot cycle, including the effectiveness of the NVIS mode of operation, and evaluation of the accuracy of standard HF propagation programs in predicting usable operating frequencies.

Near vertical incidence skywave (NVIS) is suitable for short distance (ground distance less than 400 kilometres) short-wave communication, and there are errors using the existing calculation methods of transmitter elevation angle in this communication range. This paper presents a synthetic method for predicting the transmitter elevation angle of NVIS links. According to whether the measured data can be obtained in the application area, different models are selected to predict the transmitter elevation angle. The accuracy of this method is verified by theoretical values constructed using three-dimonsional ray-tracing technology. The research results can be used for frequency selection and field strength prediction of short-range skywave communication.

Accurate noise estimation in the HF band is a defining aspect in the evaluation of SNR for communication links. The reference document that specifies how different types of electromagnetic noise can be taken into account by radio communication system planners is the ITU-R Recommendation P.372.Meanwhile a series of studies have demonstrated that Gaussian noise in the HF band is not always valid because this band noise is strongly affected by atmospheric emission sources such as lightning impulse. This leads to the idea that a distribution suited to express the noise variance is the Bi-Kappa distribution. In addition, over the past decade, SDR devices and real-time spectrum analysers, which can be used to evaluate this noise, have registered explosive growth. This article indicates technical solutions and procedures used to estimate the noise level in the HF subband which can be used for Near Vertical Incidence Skywave (NVIS) communications and proposes a measurement system based on a SDR solution which meets these requirements.

The benefits of using high frequency (HF) circuits for both long-range beyond line of sight (BLOS) and short-range near vertical incidence skywave (NVIS) military applications are well documented. STANAG 4538 specifies an automated HF system that incorporates robust waveforms and protocols with the aim of providing faster link establishment and higher message throughputs under a variety of channel conditions. Under the auspices of the. NATO BLOS Communication WG, international trials have evaluated the link establishment and data link performance of S4538. Comparisons have been made with existing technologies such as MS-ALE and FS-1052. The testing has shown that S4538 offers a considerable improvement over MS-ALE in terms of increasing communications availability and decreasing LSU times. S4538 was also shown to be more reliable under poor channel conditions, such as those prevalent in the tactical environment. The operation of both point-to-point (PTP) and point-to-multipoint (PTM) protocols have been observed. Furthermore, the benefits of using RTCE information from sounding (or previous successful communications) has been observed.

Separate excitation of the characteristic waves in the ionosphere results in two orthogonal propagation channels on the same frequency, which may be used in diversity and multiple-input, multiple-output (MIMO) systems. In this article, a method to measure the isolation between these paths is proposed and demonstrated in a near vertical incidence skywave (NVIS) experiment at a frequency of 7 MHz over a 105-km distance. Characteristic wave isolation exceeding 25 dB is measured during Happy Hour: the interval when the propagation path just opens or closes and only the extraordinary wave propagates.

Dr Yongjin Kim of Inha Technical College, Korea, talks about the work behind the paper ‘Design of transparent multilayer film antenna for wireless communication’, page 12. Dr Yongjin Kim I received my B.S. degree in electrical engineering from Inha University in Inchon, and my M.S. and Ph.D. from Ohio State University, Columbus. During graduate school, in the ElectroScience Laboratory at Ohio, I joined several projects involving design of conformal antennas, subsurface target detection/identification, ground bound reduction for outdoor range measurement and radar systems. Then, from 2003 to 2007, I was a senior engineer in the communication and networking laboratory at the Samsung Advanced Institute of Technology in Korea, where I conducted research into the design of various antennas for communication devices, including cellular phones and UWB and RFID antennas. Since then, I have been an associate professor at Inha Technical College. My principle area of research is the design of modern communication antennas and my current interests include a smart antenna system and the development of conductive file antennas with composite materials and structures. A variety of studies using transparent electrodes and transparent conductive films have been conducted in RF applications. If the RF performance of a transparent antenna can be made similar to that of a conventional antenna, a wide range of applications in wireless communication become possible, including for the Internet of things (IoT) and RFID. I was interested in the study of this idea and I thought it could lead to a breakthrough in the antenna field. In the paper, we propose a multilayer thin film antenna for mobile devices. The proposed antenna consists of an IZTO/Ag/IZTO multilayer film that is fabricated on polyimide substrate and a copper layer. The center frequency of the antenna is 1260 MHz. The proposed antenna using an IZTO (indium zinc tin oxide) electrode has an excellent resistive characteristic and high flexibility. Also, it shows a transmittance of 86%. The proposed antenna is made by inserting a thin Ag layer between two layers of IZTO. We placed the IZTO/Ag/IZTO 3-layer structure over a polyamide substrate. The antenna is designed as an IFA type structure with a coupled loop and two branches. Our antenna has very high transparency and good radiation efficiency, showing an excellent balance with regard to the trade-off between the two. It is also the first antenna model for a mobile hand set using an IZTO/Ag/IZTO 3-layer structure. I think this will be a good basis of research for the future development of the transparent antenna. Of course, the strength of transparent antennas is transparency, they can be attached to many kinds of objects requiring antennas, including TVs, cellular phone displays, automobile glass, etc; and for RFID and IoT applications, where making the antenna inconspicuous may be desirable for a range of different reasons. The interest for transparent wireless communication devices is increasing due to the demands from a variety of designs and developments in communication services, both from the perspective of visual design and being able to integrate device components more efficiently. Thus, I think the research into transparent electronic components and materials will continue. There are several challenges in this research. One of them is the fine manufacturing process, which is a key point of determining antenna performance. The next one is increasing the conductivity of the 3-layer structure without decreasing the transparency of the antenna. There is also a simulation modelling issue for designing the antenna structure. In the transparent and flexible antenna area, one of my related projects is in the use of composite materials of carbon nanotube and other polymer materials such as a poly-vinylidence fluoridle for antenna applications.

A simple design of a compact probe-fed stacked patch antenna is proposed for broadband applications. The antenna design is presented on the basis of simulation results. The possibility of achieving as much as 24% impedance bandwidth (SWR<2) from a compact antenna is revealed.

Recent developments in the field of wireless communication industry continue to drive the requirements for small, compatible, and affordable multiband antennas. To overcome the challenges of multi-frequency operation a new scheme of multiband is proposed. In this paper, the design of a micro strip patch antenna for multiband operations is proposed. This antenna shows the three distinct frequency bands, centered at 4.02 GHz, 6.18 GHz and 11.13 GHz. Furthermore, to increase the frequency bands the same antenna structure is modified by attaching a T-shaped slit on the radiating patch. This proposed modified antenna has four distinct operating frequency bands centered at 3.92 GHz, 5.82 GHz, 7.88 GHz and 11.35 GHz with improved return loss. The proposed antennas has compact size of 25 × 28 × 0.82 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> including the ground plane and both antenna structures are designed on FR-4 substrate (er= 4.4) of thickness h=0.8 mm. The proposed structures were simulated by using the electromagnetic (EM) simulation software. The simulated return losses are less than-10 dB at resonance frequencies. The presented antennas are suitable for multiband wireless communication systems.

A design of a loop antenna is proposed for future 5G wireless communication. The radiating element is producing a second resonance at 38 laterally slimmed in a hemispherical manner to intensify the surface current density along the hemispherical contour, producing a second resonance at 55 GHz. In the previous paper, they implemented a wave antenna for communication. Using wave antenna for communication, the antenna size is very much small when compared to another antenna. In the wave antenna, the design of the antenna cannot increase bandwidth or wavelength, so that can get poor communication when transmitted. But using the loop antenna, this loop antenna can achieve system performance, directivity, radiation pattern. Loop antenna can be operated at 55 MHz for better communication. To reduce the distortion in the system, go for a loop antenna which can reduce distortion. There are many advantages to using the loop antenna. To reduce the problem previously, we go for a loop antenna, which can give good system operation. The antenna is centered on a single shielded loop inserted in the dielectric GIS window that tests the TEM mode propagation of PD currents. In conjunction with a trans-impedance amplifier, this paper outlines the related antenna parameters and antenna performance. The antenna sensitivity is within a few meters of the PD source, in the order of 1 pc. under laboratory conditions.