Uncertainty analysis of intermodulation-based antenna measurements

Intermodulation measurement principle has been proposed for characterizing transponder antennas. Although the method seems to offer certain advantages compared to traditional antenna characterization methods, the measurement uncertainty has not yet been well characterized. We aim at identifying the main sources of measurement uncertainty and estimating the achievable accuracy in a certain case at 1 GHz.Peer reviewe

An investigation of series LC resonant circuits within a sleeve balun to achieve wideband operation

In antenna measurements, it is not recommended to connect a balanced antenna directly to the coaxial cable feed. A balun is required to prevent surface current from flowing onto the outer shield of the feed cable. Balun chokes like the sleeve balun, also known as bazooka balun or quarter-wavelength balun, are commonly used in antenna measurements. In general, baluns do perform well, but their performance is band-limited. Hence, for wider frequency bands, multiple baluns with different operating frequencies have to be used. This presents a major problem, especially in broadband antenna measurements. To this end, a proposed design based on the quarter-wave bazooka (sleeve) balun has been investigated. The design consists of resonators arranged in a log-periodic manner. The main objective of this design is to have high impedance and therefore high common mode rejection ratios at different frequencies. To do so, resonant series LC circuits were placed between the outer shield of the coaxial cable and the inner wall of the balun. These are intended to create short circuit terminations within the balun at different design frequencies. Two models have been investigated: one with two LC circuits and the other with four LC circuits. The variables considered in the study included circuit placement and circuit quality factor Q. Simulations in Agilent ADS$^{\circledR}$ and HFSS$^{\circledR}$ 14.0 were performed to study the common mode rejection ratio (CMRR) parameter of the different proposed designs. In addition, three baluns were built and measured in order to compare with simulations. Results demonstrated that the Q of the inductor significantly affects the response over a frequency range. Comparisons of the performance of the different designs are presented in detail in this work. All designs achieved a common mode rejection ratio above 30 dB over a wideband frequency range

Modeling of cable for measurements of small monopole antennas

Coaxial cable is often used for measurements of antennas inside anechoic chambers. In the measurement of a monopole antenna with a small ground-plane, the finite-sized ground causes the current to flow back from the radiator to the outer surface of the coaxial cable. This results in secondary radiation which introduces errors to the measured radiation pattern. To reduce the unwanted secondary radiation, the coaxial cable can be covered with EMI suppressant tubing materials. However, this introduces errors to the measured efficiency. In this paper, the models of the coaxial cable with and without suppressant tubing are developed and used for computer simulation. The cable effects on the measured results of a small monopole ultrawide band (UWB) antenna are studied by using the antenna measurement equipment Satimo StarLab and the EM simulation tool CST. The results show great agreements between the simulated and measured results. © 2011 IEEE.published_or_final_versio

Characterization of a Structure Consisting of Magnetostatic Responsive Microscopic Particles and Its Applications In Antennas

Wireless communication systems often require that a single antenna work at different frequencies. Thus the recon gurable antennas are useful in frequency agile environments to receive a signal over multiple bands. Research on antenna recon gurability using mechanical systems and radio frequency (RF) switches have been implemented in the past years. One problem for these voltage- controlled switches is that they require direct current (DC) bias control lines for operation. The incorporation of DC biasing circuitry also limits designers to explore the recon gurable capacity of many antennas. The DC bias control lines can possibly degrade the antenna performance. Moreover, because of the additional control signals, many existing multiband systems cannot use recon gurable antennas. In this research, magnetostatic responsive particles are used in micro-sized cavities to manufacture novel magnetic switches that are activated in a magnetic eld. Furthermore, the characterization, modeling in simulation software, and lumped element model extraction of these micro electromechanical systems (MEMS) based on magnetic switches is presented. A re ned method of quantifying the micro sized magnetic particles in a cavity and the response of the proposed micro level magnetic switches in the RF eld is also explained in detail. Then, a microstrip patch antenna loaded with Electromagnetic Band Gaps (EBGs) that cannot be recon gured using existing RF switching devices was recon gured using the proposed magnetic switches and is presented in this research for the rst time. A comparison between PIN diodes and the proposed magnetic switches on a microstrip patch is also included in this research to show the efficiency of the proposed structure. Overall, the proposed magnetic switches showed good results when used in antenna systems to achieve recon gurability and do not effect the radiation characteristics of the recon gured antenna.COMSATS Institute of Information Technology, Pakista

Theoretical and Experimental Study to Improve Antenna Performance Using a Resonant Choke Structure

Every antenna requires a feed network to supply its RF energy. In the case of a simple dipole antenna, this could be a coaxial cable with a tuning element and matching balun. For mostly omnidirectional antennas, currents can easily couple to metallic surfaces inside an antenna's near field that includes the outer conductor of the coaxial feed line. These outer conductor currents can radiate into the far field to skew overall antenna radiation patterns. Other parameters such as VSWR may also be significantly affected. Electromagnetic field absorbers placed on the coaxial waveguide pose other problems where multiple RF carriers exist and non-linear dielectric materials can cause issues. Coil structures can also lead to radiation problems. This leads towards a metallic resonating choke solution, which will allow the antenna to radiate without affecting performance. The primary goal of this research is to integrate a metallic resonant choke structure that will prevent currents from travelling down the feed line outer conductor. In this work, an in-depth analysis is performed on each antenna component. This includes the feed network elements (waveguide coaxial line, tuning element, matching balun) and the radiator (dipole arms, resonant choke, outer feed). Each element is analyzed and designed to allow the manufactured antenna to have similar performance to its ideal center-fed counterpart for a tuned frequency band. To predict the performance of the manufactured antenna, several simulation models are constructed. To model the radiator and resonant choke structure, a Method of Moments code is written with Matlab. These results are compared with HFSS and measurements with good correlation. Specifically, the axisymmetric MoM code uses a KVL approach to integrate the internal choke structure that works well to reduce simulation time to a fraction of that taken by FEM solvers. To design the feed components, a combination of circuit models and HFSS allows for quick design with accurate results when compared with measured values. This systems design approach has the flexibility to add complexity to improve accuracy where needed

S-band antenna phased array communications system

The development of an S-band antenna phased array for spacecraft to spacecraft communication is discussed. The system requirements, antenna array subsystem design, and hardware implementation are examined. It is stated that the phased array approach offers the greatest simplicity and lowest cost. The objectives of the development contract are defined as: (1) design of a medium gain active phased array S-band communications antenna, (2) development and test of a model of a seven element planar array of radiating elements mounted in the appropriate cavity matrix, and (3) development and test of a breadboard transmit/receive microelectronics module

Examination of Additively Manufactured Chokes for Size Reduction and Performance Improvement in RF and Microwave Applications

For many RF and microwave applications, a balun is imperative to ensure the proper performance of a balanced structure that is connected to an unbalanced structure. Sleeve baluns are a common type of balun that are relatively cheap and basic, but they are also large, heavy, and time consuming to assemble. This works presents several novel methods of using additive manufacturing techniques to mitigate all of these issues. First, a methods of 3D printing basic designs to reduce weight and improve ease of assembly is presented. This method is then used to construct balun with up to two folds, which reduces the overall size of the balun with each consecutive fold. Next, a castable silicone is used to also reduce the overall size of a balun by reducing the effective wavelength on the balun’s interior, which is first tested with traditional unfolded baluns. This method was then combined with the folded balun design to compound the size reduction from both methods. A final method of printing a dielectric core and applying metal to the core is then presented. The performance of all of the baluns is presented and discussed and future improvements are addressed. Ultimately, this work establishes a method of drastically reducing the size of sleeve baluns to a point where they can be used as in line components, while still maintaining performance levels comparable to a standard, bulky sleeve balun

Broadband active differential array for the mid-frequency SKA band

This paper presents the design and characterization process of an active array demonstrator for the mid-frequency range (i.e., 300 MHz-1000 MHz) of the future Square Kilometre Array (SKA) radio telescope. This demonstrator, called FIDA3 (FG-IGN: Fundación General Instituto Geográfico Nacional - Differential Active Antenna Array), is part of the Spanish contribution for the SKA project. The main advantages provided by this design include the use of a dielectric-free structure, and the use of a fully-differential receiver in which differential low-noise amplifiers (LNAs) are directly connected to the balanced tapered-slot antennas (TSAs). First, the radiating structure and the differential low-noise amplifiers were separately designed and measured, obtaining good results (antenna elements with low voltage standing-wave ratios, array scanning capabilities up to 45°, and noise temperatures better than 52 K with low-noise amplifiers at room temperature). The potential problems due to the differential nature of the proposed solution are discussed, so some effective methods to overcome such limitations are proposed. Second, the complete active antenna array receiving system was assembled, and a 1 m2 active antenna array tile was characterized

A Review on 5G Sub-6 GHz Base Station Antenna Design Challenges

Modern wireless networks such as 5G require multiband MIMO-supported Base Station Antennas. As a result, antennas have multiple ports to support a range of frequency bands leading to multiple arrays within one compact antenna enclosure. The close proximity of the arrays results in significant scattering degrading pattern performance of each band while coupling between arrays leads to degradation in return loss and port-to-port isolations. Different design techniques are adopted in the literature to overcome such challenges. This paper provides a classification of challenges in BSA design and a cohesive list of design techniques adopted in the literature to overcome such challenges.</jats:p