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A new design of broadband slot antenna with circular polarization is presented. The broadband characteristics are achieved using a coplanar-waveguide (CPW)-fed two-arm spiral slot configuration. The spiral slot antenna and the feeding structure are fabricated on the same plane of the substrate so that the circuit process and the position alignment could be simplified. The improvement of circular polarization for the antenna is obtained mainly by an arc slot surrounding the spiral slots. The turn number of the spiral slots and the geometrical dimensions of the arc slot are varied in order to derive the better performance of the circular polarization. The measured impedance bandwidth of a S11 < -10 dB ranges from 1.25 to 8 GHz and covers most of the commercial wireless communication systems, such as GPS, DCS, PCS, IMT-2000, WLAN, and HiperLAN. The measured 3-dB axial-ratio bandwidth (ARBW) is 10.6% with respect to 1.605 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1204–1208, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25142 [ABSTRACT FROM AUTHOR]

A wideband coplanar waveguide (CPW)-fed two-arm spiral slot antenna without a balun circuit is presented in this article. Phase progressions at arm ports are realized through the coplanar waveguide excitations. A detailed characterization of all antenna components and parameters is provided along with guidelines and recommendations for broad bandwidth and small reflection. Variations of the impedance matching due to the turn numbers, the ground width separated between two neighboring turns and the slot width are tested and studied. The measured impedance bandwidth of a S11 ≤ 10 dB ranges from 1.63 to 8 GHz and covers most of the commercial wireless communication systems, such as DCS, PCS, IMT-2000, WLAN, Bluetooth, and HIPERLAN. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 222–225, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23947 [ABSTRACT FROM AUTHOR]

In this study, a coplanar waveguide-fed band-selective filter and a spiral slot antenna have been designed, fabricated, and integrated for the applications of multisystem integration. The antenna module was fabricated on the same plane of the substrate, so that the circuit process and the position alignment could be simplified. The passband responses of the filter ranging below 2.6 GHz and from 5.0 to 6.0 GHz cover most of the commercial wireless communication systems. Simulated results are compared with measurements performed on the antenna module. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2264–2267, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21915 [ABSTRACT FROM AUTHOR]

In this paper, an isosceles triangular patch resonator with an inverted V-shaped slot pattern is fabricated to realize a miniaturized microstrip dual-mode filter. The proposed structure possesses the elliptic characteristic and has the advantage of size and loss reduction. After analyzing the results, the relationships between the filter characteristics and the geometrical parameters of the inverted V-shaped slot are derived. The dual-mode filter exhibits a fractional bandwidth of 14.5% centered at 1.93 GHz with the lowest insertion loss of 1.4 dB. It is shown that a size reduction of 37% is achieved compared with a conventional dual-mode triangular filter. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1969–1974, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21824 [ABSTRACT FROM AUTHOR]

Three microstrip miniaturized meanderline antennas for mobile communications are presented in this paper. Two-arm meanderline antennas, one with a patch and one with a rectangular loop, are fabricated and tested. The advantages of the antennas are the lower circuit cost, light antenna weight, short process time, a minimum number of via holes and simplified mechanical construction. In our experiments, comparisons of the radiated power and return loss of the three topologies of the meander-line antenna are presented. The loading effect of the outside environments surrounding the meander-line antennas is also discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 207–210, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20420 [ABSTRACT FROM AUTHOR]

In this paper, the effects of the monopole antenna with windowed ground plane have been studied, including the impedance condition and the radiation patterns. A circularly microstrip monopole antenna is used as a radiated element. By utilizing a circular or rectangular slot of the extended ground plane to change the distribution of the electrical field, the injected power radiates from the slot and patch regions. According to the measured results, the radiation patterns and the antenna gain have been improved. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 407–411, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20319 [ABSTRACT FROM AUTHOR]

In this paper, a microstrip filter has been designed, fabricated, and measured for application in ultra-wideband antennas. By using the combination of a band-stop filter and a low-pass filter, the band-selective characteristics can be demonstrated. In order to enhance the suppression of the out-of-band signals, a defected ground structure (DGS) with stopband performance is used. The passband responses of the filter, which range below 2.8 GHz and from 5.0 to 6.0 GHz, cover most commercial wireless communication systems. The LC-lumped equivalent circuit of the filter has been extracted and simulated by using transmission-line analysis. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 248–251, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20107 [ABSTRACT FROM AUTHOR]

A new method which can enhance the scanning angle and elevate the operating frequency for active scanning leaky-wave antennas is proposed in this paper. We know that the characteristics and performance of scanning leaky-wave antennas are strongly dependent on the variation of the operating frequency within the leaky-mode region. The self-oscillating doubler without external oscillator sources provides double-frequency variation at the second-harmonic frequency instead of one-frequency variation at the fundamental frequency. Therefore, the antenna scanning range can be enhanced and the operating frequency can be elevated. The measured scanning angle of this antenna is 13°, which agrees well with the predicted 13.7°, and the data show that the frequency-scanning ability of the leaky-wave antenna using a self-oscillating doubler increases as predicted. This self-oscillating doubler design is very simple, and it not only can improve the scanning capability of the active leaky-wave antenna, but it is also very suitable for millimeter-wave active antenna design. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 108–111, 1999. [ABSTRACT FROM AUTHOR]

An active-integrated two-terminal leaky-wave antenna design is demonstrated in this paper. An X-band two-terminal-fed microstrip leaky-wave antenna and an active source, a varactor-tuned oscillator HEMT VCO, are integrated on the same plane. The space wave, due to the first higher order mode, dominates the leakage of the radiated energy in this experiment. This approach, as compared to a traditional single-terminal feeding leaky-wave antenna, creates a dual-beam radiation pattern, and has the advantages of multidirection and no reflected wave caused by the open end of the radiating element. Measured results on the experimental antenna show that the total scanning angle of two beams of this antenna configuration is approximately 44°, the maximum effective isotropic radiated power (EIRP) is close to 17.5 dBm for the right beam and 16.7 dBm for the left beam at 10.4 GHz, and the power difference between the two beams is less than 1 dB. Between 9 and 11.5 GHz, the return loss is less than -10 dB, and the transmission coefficient shows that the power radiates into space. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 100–103, 1998. [ABSTRACT FROM AUTHOR]

The active leaky-wave antenna arrays have been demonstrated, which integrate several microstrip leaky-wave antenna elements with a single HEMT oscillator as an active source at 10.2 GHz. To excite the first higher order mode, the leaky-wave antenna is fed asymmetrically. The reflected wave due to the open end of each leaky-wave antenna element has been suppressed by the symmetric configuration of this antenna array. When comparing with the measured radiation pattern of the single-element antenna, we found that 1×2 and 1×4 antenna arrays can effectively suppress the reflected power by more than 5.5 and 10.5 dB, respectively. Furthermore, the power gains are more than 2 and 3.16 dB higher than the single-element antenna with a measured EIRP of 18.67 dBm. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 14–17, 1998. [ABSTRACT FROM AUTHOR]

In this paper, a novel triple-band microstrip-fed slot antenna for wireless communication systems operating at 2.4, 5.2, and 5.8 GHz is demonstrated. The slot antenna is originally designed to radiate at 2.4 GHz. By etching a stair-shaped slot on the ground plane and adding several stubs at the edge to excite the first higher-order mode, we can create another resonant band at 5 GHz. According to the results, the impedance bandwidths are 227 and 778 MHz at the 2.4- and 5-GHz bands, respectively. In addition, the dimension of the proposed slot antenna is smaller than that of the conventional rectangular-slot antenna. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 370–372, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11220 [ABSTRACT FROM AUTHOR]

A new design of a miniaturized multilayer ceramic (MLC) antenna is proposed and presented for the applications of the dual ISM bands (hyper LAN and WLN). The antenna-size reduction is achieved by folding the simple microstrip monopole around a low-temperature co-fired ceramic (LTCC) substrate. This paper presents measured data to show that the 10-dB bandwidths achieved were 180 MHz and 750 MHz at 2.4 GHz and 5.2 GHz, respectively. The co-polarization far-field radiation patterns of the chip antenna are quasi-omnidirectional at 2.4 GHz and 5.2 GHz. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 140–142, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10848 [ABSTRACT FROM AUTHOR]

A method to suppress the back lobe of a short leaky-wave antenna (LWA) by using an aperture-fed patch antenna on the backside is demonstrated in this paper. The aperture-fed patch antenna is connected to the open end of the LWA. This design offers another radiation path of the reflected wave and creates another radiation pattern on the back plane of the substrate. Experimental results show that the suppression of the reflected wave can be 10 dB at 10.0 GHz with an LWA length of 6 cm (2 wavelengths). Compared to the conventional design, this novel structure can radiate as efficiently as LWA at a length of 4 wavelengths. The two radiation patterns on different planes have great potential in many applications and can provide more flexibility to traditional designs. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 129–131, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10696 [ABSTRACT FROM AUTHOR]