Folded Monopole Antenna Research Articles

Compact broadband folded monopole antennas with shorting pins

An investigation of broadband folded monopole antennas with shorting pins is proposed. The proposed antennas are compact in size, and can provide sufficient bandwidths for the DCS (1710–1880 MHz), PCS (1850–1990 MHz), 3G (1920–2170 MHz), and WLAN (2400–2484 MHz) bands. The method used to realize size compact is to introduce a folded monopole antenna, which is difficult to accomplished with a planer substrate. Here, we introduce the shorting pin and find its optimal position in order to approach a folded-antenna. Details of the antenna design and the experimental results are presented and discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 471–474, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20670

Built-in folded monopole antenna for handsets

A built-in folded monopole antenna for handsets (BFMA) is introduced and investigated. The characteristics of the BFMA are compared with those of a planar inverted-F antenna (PIFA), which is one of the conventional handset antennas. As a result, it has been confirmed that the BFMA has smaller size and wider bandwidth compared with the PIFA.

Plate‐loaded folded monopole antenna on a ground‐plane edge

AbstractA folded monopole antenna loaded with a rectangular plate placed at the edge of the ground plane is proposed and its characteristics are evaluated by numerical analysis with the FDTD method and by experiments. This antenna is characterized by a structure in which one of the two conductors forming a folded monopole element is a rectangular plate. The structure is suitable for surface mounting on a printed circuit board. In this paper, mainly for an antenna using a dielectric chip with a permittivity of 2.6, the configurations of the feed line and the short‐circuited line and the shape of the loading conductor plate affecting the antenna characteristics are investigated. It is made clear that the element height and the shape of the loading plate along the longer side mainly contribute to the determination of the resonant frequency. The changes in the characteristics due to the finite size of the ground plane are studied both from the input characteristics and from the radiation characteristics. It is shown that the present antenna has radiation characteristics essentially identical to those of the monopole antenna and that the disturbance in the radiation patterns is caused by the fact that the length of one side of the ground plane is close to resonance. Also, the characteristics of the antenna with a helical loading plate and the effect of the permittivity of the core materials used for size reduction of the antenna are evaluated. It is shown that an antenna with the electrical dimensions of the element reduced to one‐half can be realized by a combination of the helical loading plate and a material with a permittivity of 10.2. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(8): 24–37, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10214

MF AM folded monopole characteristics

Folded monopole antennas have been used for many years in medium frequency amplitude modulation broadcast applications. These antennas offer a grounded radiating structure with a height approximating a quarter wavelength. Folded monopoles have been studied exhaustively during a previous effort in an attempt to characterize the input impedance and directivity characteristics as a function of monopole height. As a result it was observed that several impedance regions can be achieved as a function of antenna height and cage diameter: Some of these regions permit a bandwidth operation sufficiently broad to support a high fidelity response for analog or digital transmissions. This type of antenna can be useful at different heights including a self matching region at the standard 50 ohms impedance. By choosing the appropriate antenna physical dimensions, antenna tuners can be avoided and thus it increases efficiency. Measurements have been made on a full scale 72 meter tower with a 6 wire cage in order to validate the calculated antenna input impedance and directivity. The cage and supporting mast make up the equivalent of a transmission line. For this reason different standard triangular towers were analyzed in order to determine their effect on the input impedance. Tower effective radius is determined taking into account the tower width and the tower leg diameter. At the same time, a minimum antenna height with maximum efficiency has been analyzed to solve the hard problem for installations at places where antenna height is a challenge for the designer.

Double-folded monopole antenna using parallel line or coaxial cable

It has been shown that loading a certain reactance component at the feeding point of an antenna is useful in reducing antenna size. When a parallel transmission line with a short-circuited end is loaded onto a monopole antenna, we can obtain a small antenna called a parallel line loaded monopole antenna. However, a small antenna usually has low input resistance and low actual gain. The approach outlined is to increase the actual gain of the small loading antenna and utilise knowledge of a folded monopole antenna, which has a very high impedance value. A small folded monopole antenna called the double folded monopole antenna (DFMA) with high resistance and high actual gain can then be realised. An explanation of the operational principles of the DFMA is provided and the characteristics of small antenna design discussed. A coaxial cable is also used as the loading element for the loading antenna. It is proposed that a coaxial cable DFMA can be realised by replacing the parallel transmission line loading with coaxial cable transmission line loading. The advantage of the coaxial cable DFMA is that it has a small cross-sectional area, since the coaxial cable loading is embedded within the cylindrical antenna element. The results of actual testing of the coaxial cable DFMA are presented. All other results are provided by computer simulation using the method of moments, since the results are assumed to be similar to those recorded from practical experimentation.

Dual band folded monopole/loop antenna for terrestrialcommunication system

With the introduction of DCS1800 to meet the demands for a wider frequency spectrum for mobile communication systems, novel antenna structures capable of generating dual resonance are in demand. An antenna structure based on the geometry of a bent folded monopole antenna capable of dual resonance frequencies operation is discussed. This antenna is able to cover the GSM/DCS 1800 communication system bands.

On the feasibility of using an atmospheric discharge plasma as an RF antenna

The plasma produced by a laser-guided, electric discharge in the atmosphere has been formed in the shape of a folded monopole antenna with a characteristic frequency of 112 MHz. This plasma antenna has been used to transmit and receive signals at 112 MHz. While the plasma remained conducting, the signal transmitted from, and received on, the plasma antenna was within -1 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\pm1</tex> dB of that transmitted from and received on a "standard" copper folded monopole antenna of the same size. During this time the signal transmitted from, and received on, the plasma antenna also remained approximately constant in amplitude (fluctuations <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim \pm1</tex> dB). This useful lifetime of the plasma antenna was varied from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim 200 \mu</tex> s to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\geq 2000 \mu</tex> s by changing the dration of the electric discharge sustaining the plasma columns. In these experiments, the noise from the plasma antenna was not distinguishable from that developed using a copper antenna, but in both cases the noise was much larger than the true thermal noise background.

A broad-banded folded monopole antenna

Electrically short folded monopole antennas with lumped mutual coupling between driven and folded sections are considered, showing that the input radiative impedance exhibits a resonance frequency depending upon the sign and magnitude of the coefficient of coupling. If extended to " <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> -folded" monopoles with separate lumped mutual couplings, the analysis shows the input radiative impedance will exhibit <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> staggered resonance frequencies and bandwidth broadening.