This study proposed a novel decoupling method for four planar inverted-F antennas (PIFAs) operating at 2.0GHz (f0). The edge-to-edge and center-to-center spacings of the adjacent PIFAs are extremely small (0.05λ0 and 0.17λ0, respectively), resulting in strong mutual coupling among them. In our previous study, we proposed a structure consisting of parasitic elements (PEs) and a bridge line (BL) for the decoupling of two PIFAs. One attractive feature of the proposed method is that no adjustment of the original structure and size of the PIFAs is necessary. However, as the number of PIFAs increases to four, their decoupling becomes considerably more complicated, and impedance mismatch is also an issue to be considered. Therefore, in this study, PEs and BLs are functionally developed to simultaneously achieve low mutual coupling and improved impedance matching of the four PIFAs. The simulated results showed that loading the proposed PEs and BLs onto the four PIFAs could reduce as well as maintain all mutual coupling for less than -10dB, and simultaneously improve impedance matching. Therefore, the total antenna efficiency at 2.0GHz could be significantly improved from 64.2% to 84.8% for PIFA1 and PIFA4, and from 35.9% to 74.2% for PIFA2 and PIFA3. Four PIFAs with PEs and BLs were fabricated and measured to validate the simulation results.

In this study, a novel decoupling method using parasitic elements (PEs) connected by a bridge line (BL) for two planar inverted-F antennas (PIFAs) is proposed. The proposed method is developed from a well-known decoupling method that uses a BL to directly connect antenna elements. When antenna elements are connected directly by a BL, strong mutual coupling can be reduced, but the resonant frequency shifts to a different frequency. Hence, to shift the resonant frequency toward the desired frequency, the original size of the antenna elements must be adjusted. This is disadvantageous if the method is applied in cases where the design conditions render it difficult to connect the antennas directly or adjust the original antenna size. Therefore, to easily reduce mutual coupling in such a case, a decoupling method that does not require both connecting antennas directly and adjusting the original antenna size is necessitated. This study demonstrates that using PEs connected by a BL reduces the mutual coupling from -6.6 to -14.1dB, and that the resonant frequency is maintained at the desired frequency (2.0GHz) without having to adjust the original PIFAs size. In addition, impedance matching can be adjusted to the desired frequency, resulting in an improved total antenna efficiency from 77.4% to 94.6%. This method is expected to be a simple and effective approach for reducing the mutual coupling between larger numbers of PIFA elements in the future.

The monocone antenna is a type of monopole antenna that has wideband characteristics. This paper proposes a low-profile monocone antenna with a planar inverted-F structure. The characteristics of the proposed antenna are analyzed through a simulation. The results demonstrate that the low-profile antenna offers wideband performance, and the relative bandwidth of VSWR ≤ 2 is found to be more than 190%. In addition, miniaturization of the monocone antenna is elucidated. The proposed antenna is prototyped, and the validity of the simulation is verified through measurements.

The research on body-centric wireless communications (BCWCs) is becoming very hot because of numerous applications, especially the application of E-health systems. Therefore, a small multi-band and low-profile planar inverted-F antenna (PIFA) with tuning function is presented for BCWCs in this paper. In order to achieve multi-band operation, there are two branches in the antenna: the longer branch low frequency band (950–956 MHz), and the shorter branch with a varactor diode embedded for high frequency bands. By supplying different DC voltages, the capacitance of the varactor diode varies, so the resonant frequency can be tuned without changing the dimension of the antenna. While the bias is set at 6 V and 14 V, WiMAX and ISM bands can be covered, respectively. From the radiation patterns, at 950 MHz, the proposed antenna is suitable for on-body communications, and in WiMAX and ISM bands, they are suitable for both on-body and off-body communications.

Although the effect of electromagnetic interference on an implanted cardiac pacemaker due to a nearby mobile phone has been investigated, there have been few studies on the enhancement of the specific absorption rate (SAR) around an implanted cardiac pacemaker due to a nearby mobile phone. In this study, the SAR distribution around a pacemaker model embedded in a parallelepiped torso phantom when a mobile phone was nearby was numerically calculated and experimentally measured. The results of both investigations showed a characteristic SAR distribution. The system presented can be used to estimate the effects of electromagnetic interference on implanted electric circuits and thus could lead to the development of guidelines for the safe use of mobile radio terminals near people with medical implants.

This paper proposes two types of electromagnetic bandgap (EBG) structures aimed for SAR reduction on a mobile phone antenna. The EBG structures, one which uses vias while the other does not can reduce the surface wave and prevent the undesired radiation from the antenna. Thus, these structures can reduce the electromagnetic fields toward the human head direction and reduction the SAR value. Tests demonstrate the reduction of SAR values and therefore, the human body can be protected from hazard electromagnetic fields by using the proposed EBG structures, regardless of whether vias are used or not.

In recent years, wireless communications systems such as wireless LAN, Bluetooth, etc. are being rapidly adopted. As the antennas used in wireless communications systems are usually installed in small mobile devices, it is demanded that the volume should be small. In our research, we focus our attention on flexible printed circuits (FPCs) to meet the miniaturization demand. In this paper, we introduce a planar inverted F antenna (PIFA) suitable for IEEE802.11b/g and Bluetooth. The antenna is made of FPC. We measured the radiation pattern of the antenna when the antenna is successively curved and folded, and it is clear that its radiation performance does not vary much when the antenna is deformed. We analyzed the antenna by using the moment method.

The development of a small and multiband antenna plays an important role in the rapidly growing mobile communication market. This paper presents the design of a novel small and wideband planar inverted F-antenna which simultaneously covers GSM850/GSM900/DCS1900/IMT2000/WLAN/DMB services. The proposed antenna consists of a main patch with a pair of slits and L-shaped patch, occupying a total volume of 15366 mm3. A very wide impedance bandwidth characteristic was achieved by optimizing both the gap distance between the feed line and L-shaped patch, and also the lengths and widths of a pair of slits on the main patch, which is excited by the modified CPW-fed line. The average gains at the frequencies of 850, 2000 and 2600 MHz were -2.51, -1.42 and -1.68 dBi, respectively. The overall shape of the radiation patterns is suitable for mobile communications.

This letter describes a dual band planar inverted-F antenna (PIFA) with non-uniform meander-line shaped slot suitable for the mobile environment scenario, which operates at the GSM 900 MHz and GSM 1800 MHz (DCS) bands. This antenna structure overcomes the lack of height of the mobile phone. In a practical mobile handset, the bandwidths of the antenna for return loss -8.5 dB are 240 MHz at 900 MHz and 250 MHz at 1800 MHz. Good impedance bandwidth performance for the dual-band is observed. The advantage of the design suggested in this letter is its simplicity of manufacturing and low cost.

A polarization diversity planar inverted-F antenna (PIFA) on portable telephone in the practical use near the operator's body is investigated at 1,800 MHz under multipath urban environment. The antenna structure comprises a center-fed square patch with one permanent short-pin and two RF-switches on three corners. The RF-switches perform as the polarization branch switches for dominantly vertical polarization (VP) or dominantly horizontal polarization (HP) modes. The radiation efficiency of the polarization diversity PIFA is 58% and 53% for VP and HP modes, respectively, which is higher than the 52% efficiency of the reference λ/4 monopole antenna under the same condition. The mean effective gain (MEG) of VP and HP modes decrease with respect to the increasing cross-polarization power ratio (XPR). The correlation coefficient of two diversity branches is between 0.66 through all the possible XPR ranging from -10 dB to +10 dB. The diversity gain is computed from the MEG and correlation coefficient to determine the diversity antenna gain (DAG). The diversity gain, based on 10-3 BER for selective combining, is 7.5 dB over non-diversity reception. The DAG is -1.2+2.8 dBi which is approximately 4 dB lower than the case without human body. In other words, the presence of the human body degrades the communication performance by a half.

A new antenna for a wristwatch phone is proposed. The proposed antenna is a one-wavelength rectangular loop along the cap of the wristwatch phone. The loop is fitted at the periphery of the openable cap connected to the wristwatch case by a hinge. In order to discuss the antenna gain, we define the two different conditions as follows. When the user opens the cap and talks over the wristwatch phone, his wrist is held in front of his face, which is called the "talk position" in this paper. When the user closes the cap and waits for a call, his wrist rests down at the side, which is called the "stand-by position. " We measured the radiation patterns and calculated the pattern averaging gain (PAG) of the proposed antenna for the two positions. In addition, we compared the proposed antenna with the other antennas: a planar inverted F antenna (PIFA) fixed on the strap and a normal mode helical antenna (NMHA) installed on the case. As a result, the PAG of the proposed antenna was about -5.5 dBd, which was the same as the PAG of the other antennas for the talk position. In the case of the stand-by position, the PAG of the proposed antenna was about -3 dBd, which was 7 dB higher than that of the other antennas. The gains of the proposed antenna reached the goal, which was the PAG of a whip antenna of a handy phone held near the head. The results demonstrate that the proposed antenna is suited to a wristwatch phone.