A low frequency electric field probe that integrates data acquisition and storage is developed in this paper. An electric small monopole antenna printed on the circuit board is used as the receiving antenna; the rear end of the monopole antenna is connected to the integral circuit to achieve the flat frequency response; the logarithmic detection method is applied to obtain a high measurement dynamic range. In addition, a Microprogrammed Control Unit is set inside to realize data acquisition and storage. The size of the probe developed is not exceeding 20 mm × 20 mm × 30 mm. The field strength 0.2 V/m ~ 261 V/m can be measured in the frequency range of 500 Hz ~ 10 MHz, achieving a dynamic range over 62 dB. It is suitable for low frequency electric field strength measurement and shielding effectiveness test of small shield.

In order to achieve an antenna with robustness to metal for closed space wireless communications, two types of the folded monopole antenna with different input impedance have been studied. In this study, we propose the folded monopole antenna, which can switch the input impedance by a simple method. Both simulated and measured results show that the proposed antenna can improve robustness to the proximity of the metal.

In this paper, a printed elliptical monopole antenna for wideband circular polarization is proposed. The antenna's structure is asymmetric with regard to the microstrip line. The section of the ground plane that overlaps the elliptical patch is removed. With simulations, the relationship between the antenna's geometrical parameters and the antenna's axial ratio of circularly polarized wave is clarified. The operational principle for wideband circular polarization is explained by the simulated electric current distributions. The simulated and measured bandwidths of the 3dB-axial ratio with a 2-VSWR is approximately 88.4% (2.12GHz-5.47GHz) and 83.6% (2.20GHz-5.36GHz), respectively.

Two types of 3D folded dipole antenna with feed line (FDAFL) were reported for a small terminal, which covered WiMAX 2.5/3.5GHz bands and WLAN 2.4GHz band. In this study, folded monopole antenna (FMA) is proposed as a variant of FDAFL. We show the broadband characteristics of FMA and determine the most suitable configuration of FMA array for realizing MIMO system. Also, a multiband variant is created by introducing a parasitic element to FMA. The result is a multiband FMA array with parasitic elements operating at 5GHz band of WiMAX and WLAN as well as WiMAX 2.5/3.5GHz bands and WLAN 2.4GHz band with total antenna efficiency of between 70% to 96% and the envelope correlation coefficient of less than 0.02. Finally, a prototype antenna is implemented, and we confirm the validity of the simulation by comparison to measured results.

This paper proposes a new small multiband printed antenna for wireless telecommunications modules that can realize Machine-to-Machine applications. We reconfigure our previous antenna to cover the 700MHz, 800MHz, and 900MHz bands, and add two new elements (second strips) to cover the 2GHz band. The new antenna achieves operation in quad-bands: 700MHz, 800MHz, 900MHz, and 2GHz. Frequency characteristics are analyzed using electromagnetic-simulation software based on the method of moments, and the validity of the numerical results is shown based on measured Voltage Standing Wave Ratio (VSWR) characteristics and the radiation patterns of a prototype antenna. The proposed antenna is compact with a VSWR bandwidth (≤2) of 27.5% in bands including 700MHz, 800MHz, and 900MHz, and a VSWR bandwidth (≤2) of 10.6% in the band including 2GHz. We clarify that the operating mechanism in the 2GHz band is equivalent to that of a one wavelength folded offset fed dipole antenna comprising a monopole element and second strips, and that the operating frequency in the 2GHz band can be determined by the path length from the tip of the monopole element to the tip of the second strip via a feeding point.

The problem of a finite monopole antenna driven by a coaxial cable is revisited. On the basis of a variable bound approach, the radiated field around a monopole antenna can be represented in terms of the discrete modal summation. This theoretical model allows us to avoid the difficulties experienced when dealing with integral equations having different wavenumber spectra and ensures a solution in a convergent series form so that it is numerically efficient. The behaviors of the input admittance and the current distribution to characterize the monopole antenna are shown for different coaxial-antenna geometries and also compared with other existing results.

In this letter, a novel ultra-wideband circular quasi-fractal monopole antenna with a six-petaled lotus pattern is presented. The CPW-fed technique and quasi-fractal concept are used to achieve ultra-wideband characteristics. The size of the proposed antenna is 4250 mm2 with a lotus diameter of 19.8 mm. The proposed antenna exhibits ultra-wideband characteristics from 2.65 to 12.72 GHz, which corresponds to a fractional bandwidth of 131%. The measured radiation pattern of the proposed antenna is nearly omnidirectional.

A folded monopole antenna fed by a CPW-to-trident transition feeder for compact wireless USB dongle devices is proposed. The antenna's dimensions are 1644.83.5 mm3, so it is suitable for low-profile wireless USB dongles. The proposed, compact monopole antenna resonates from 2.28 GHz to 10.8 GHz; hence, it can cover all wireless bands including WiBro (2.3–2.4 GHz), Bluetooth (2.4–2.484 GHz), WiMAX (2.5–2.7 GHz and 3.4–3.6 GHz), satellite DMB (2.605–2.655 GHz), 802.11b/g/a WLAN (2.4–2.485 GHz and 5.15–5.825 GHz), and UWB (3.1–10.6 GHz). A fabricated antenna is tested on a laptop to investigate the effects of the keypad and LCD screen on the resonant frequency and radiation pattern. The measured average gain of the fabricated antenna ranges from -2.76 dBi to 0.72 dBi.

An infinitely long monopole antenna driven by a coaxial cable is revisited. The associated Weber transform and the mode-matching method are used to obtain simple simultaneous equations for the modal coefficients. Computations are performed to illustrate the behavior of current distribution and antenna admittance in terms of antenna geometries.

A small broadband omni-directional printed antenna comprising symmetrically arranged trapezoid elements is investigated for broadband Voltage Standing Wave Ratio (VSWR) and low center frequency characteristics. Two symmetrical trapezoid elements are printed on the bottom side of the substrate and are connected to a small ground plane printed on the same side over two strips. The trapezoid elements and the strips are excited in an electromagnetically coupled manner by the monopole element set between the trapezoid elements. Two resonance characteristics arise because the resonance part changes depending on the frequency, and a broad bandwidth becomes possible. The center frequency can be lowered by changing the shapes of the trapezoid elements. The monopole element length is a very important parameter for impedance matching. The space between the monopole element and the trapezoid elements is an important parameter for the optimization of two resonance characteristics. The proposed antenna is shown to achieve a VSWR bandwidth (≤2) of 28.9%, a low profile, and omni-directional pattern features. The measured and numerical results are in good agreement.

This letter presents a low-profile printed monopole wideband antenna for mobile terminals. The proposed antenna is simply structured with an inverted-L strip, which occupies the small area of 3180.8 mm3 (0.023λL0.138λL0.006λL at lower frequency edge of 2.3 GHz) on a substrate which is perpendicular to the circuit board of the terminal. The height of the upright substrate is only 3 mm (3.8 mm including the circuit board). The proposed antenna achieves a 10-dB impedance bandwidth of 59.7% ranging from 2.16 GHz to 4 GHz, which can cover which can cover the 2.4 GHz WLAN (2.4-2.4835 GHz) and WiMAX (2.3-2.4/2.495-2.69/3.4-3.6 GHz) operational bands. It is suitable for application to a multiband mobile phone due to its relatively low profile.

This paper presents a planar monopole antenna with slits and a stub for multi-band operation in vehicles. The proposed antenna is at least 55% smaller than the regular rectangular monopole antenna and covers eight wireless application bands. Slits cut into the rectangular monopole alter the surface current paths so that the band coverage is expanded. A long bent-stub is also added to cover the lowest service band.

New structure of broadband planar antenna, combining monopole elements with electromagnetic bandgap (EBG) structures, is proposed. The antenna has a simple single layer structure and unique beam pattern. Antenna is fabricated on a surface of a single layer dielectric substrate and back side of the substrate is covered with metal layer. At the center of the substrate, an inverted L monopole strip is fabricated and on both sides of this monopole, EBG unit cells are placed. By tuning monopole length and EBG bandgap frequency, the monopole resonates even if metal layer exists close to the monopole radiator. Three types of EBG, one dimensional (1D), square two dimensional (2D) and hexagonal 2D, are tested. By combining monopole strip with hexagonal 2D-EBG, the bandwidth of prototype antenna, whose return loss is less than 10 dB, is 840 MHz in 5 GHz band. To control beam patterns of antenna, parasitic elements are placed close to the monopole radiator and EBGs. These parasitic elements work as directors of quasi Yagi-Uda antenna and radiation gain at lower tilt angles is improved.

This paper investigates the performance of multiple monopole antennas mounted on a card-type terminal, which is expected to be used in the systems beyond 3 G, based on the calculated and measured radiation patterns for the 2.0 GHz. We characterize the feasible performance of quarter-wavelength monopole antennas mounted on a card-type terminal in a multiple antenna configuration with narrow element spacing of less than a half-wavelength assuming that the antennas used must satisfy the space restrictions of the mobile terminal. Performance figures of merit for the multiple antenna performance include the beamforming gain, correlation coefficient, and MIMO channel capacity. Furthermore, we investigate the influence of a finite ground plane on the characteristics of multiple monopole antennas using a typical antenna configuration comprising a simple finite ground plane and multiple monopole antennas to discuss the fundamental characteristics.

A compact built-in handset antenna for multiple-input multiple-output (MIMO) system at 2 GHz, comprising two elements array of newly proposed L-shaped folded monopole antenna (LFMA), is evaluated under the multipath radio wave propagation environments. By analyzing the fundamental characteristics, mean effective gain (MEG), correlation, and channel capacity, the significant enhancement in the capability, as a handset MIMO antenna under practical use conditions, was confirmed. The performances were also compared to those of an array antenna comprising two planar inversed-F antenna (PIFA) elements in order to verify the effectiveness of the proposed antenna. The results show that the equivalent or improved performances can be realized, by using the proposed LFMA array with a compact size, taking only the volume of 44% of a PIFA array. The LFMA array provides almost the same bandwidth and enhanced isolation compared with a PIFA array, and the sufficiently low correlation and acceptable effective gain are obtained under the multipath radio wave propagation environments. In addition, a greater channel capacity than a PIFA array is achieved especially when the proposed LFMA array is inclined for the display-viewing mode, and moreover, an almost doubled increase in the channel capacity is obtained by using MIMO transmission compared with single-input single-output (SISO). This study also show that the MEG has much effects on the channel capacity, rather than the correlations, for the proposed antenna.

A multiband T-shaped monopole antenna for WLAN/WiMAX applications is presented. The T-shaped monopole is comprised of two horizontal arms of different lengths, which generate two separate resonant modes for 2.5/5.5 GHz WLAN/WiMAX bands, and with a shortened parasitic element, which generates a middle resonant mode for 3.5 GHz WiMAX band, for seamless wireless network access applications. The proposed antenna has been successfully simulated and implemented. Both results of simulation and measurement show good agreement. For the lower band from 2.3 to 2.7 GHz, the gain varies in the range of 2.5-3.3 dB, while the radiation efficiency is from 72% to 85% over the band. As for the middle band from 3.3 to 3.7 GHz, the gain varies from 1.5 to 2.0 dB, and the radiation efficiency is from 62% to 70%. As for the upper band from 5.2 to 5.8 GHz, the antenna gain varies from 5.4 to 5.9 dB, and the radiation efficiency is from 63% to 66%.

A novel helix-monopole antenna is proposed which combines the helix and monopole together to form improved current distribution. The current magnitudes are computed with Moment Method (MM) and results show the current difference between helix-monopole and helix antenna. Two antennas are fabricated for comparison and measured on the same two-way portable radio with frequency band from 400-420 MHz. Measurements prove that the proposed antenna offers a significant improvement in gain.

In this paper, we report the detailed investigation of novel printed disc monopole antennas for ultra-wideband (UWB) applications focusing on miniaturization of the disc radiator. First, the basic property was examined for the case of a circular disc with diameter of 50 mm, and it was found that the VSWR is less than 2 in the UWB band of 3.1-10.6 GHz when the feed gap length is between about -0.1 and 0.2 mm. Next, in order to reduce the size of the disc radiator, various dimensions of elliptical discs were investigated. It is shown that if the dimensions of the elliptical disc are chosen appropriately, a smaller disc size antenna can be achieved. To decrease the antenna size further, a triangular notch and an exponentially curved notch on the ground plane of the antenna were examined. It is observed that the use of the notched ground is very effective and that the diameter of the circular radiator can be reduced to 17 mm. The proposed antenna has an omnidirectional pattern in the x-y plane. The influence of the notch on the radiation pattern is very small. Details of the simulation results using the FDTD method and experimental results for the proposed antenna are presented and analyzed. These features are very attractive for UWB applications.

A small microstrip-fed monopole antenna using an L-shaped notch is presented for ultra wideband applications. The proposed antenna, with compact size of 15.521 mm2 including the ground plane, is designed to operate over the frequency band between 3.05 and 10.9 GHz for S11 < -10 dB. Good return loss and radiation pattern characteristics are obtained in the frequency band of interest.

The three beam-switched top-loaded antenna is suited to be applied to a wireless local area network to switch the radiation pattern by arranging several unidirectional antennas. In this paper, a three beam switched top loaded monopole antenna is proposed to realize its small size and planar structure. Three top loaded monopole antennas are arranged around a parasitic hexagonal patch at intervals of 120 degrees. The feed element is selected by the switching device to switch the radiation pattern. This antenna allows for reduction in the number of elements as well as downsizing. The front to back ratio (F/B) becomes 23 dB by selecting suitable parameters.