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In this paper, flexible CPW parallel resonators which consist of parallel combination of short- and open-end CPW series stubs on polyimide film are presented. Phase compensation method using smith chart is applied to obtain equivalent circuit of each CPW parallel resonator. Two CPW parallel resonators are designed at 5.8 GHz and 11.6 GHz, respectively. Then, a band-stop-filter (BSF) for harmonics suppression is implemented with two designed CPW parallel resonators. The measured frequency responses of the series stubs, resonators, and a BSF are in good agreement with the predicted simulation results. [ABSTRACT FROM AUTHOR]

In this article, a compact dual-mode λg/2 bandpass filter with the characteristic of harmonic rejection is designed and implemented.The second and third harmonics of the suggested bandpass filter are rejected by using the additional open stubs of the T-type equivalent circuit for the quarter wavelength line. Also, the J-inverter is investigated as functions of the impedance and electrical length of the open stub of dual-mode λg/2 resonator. From the results, the lower impedance of open stub of dual-mode λg/2 resonator is better for the good performance of the dual-mode λg/2 bandpass filter. The harmonic-rejected dual-mode λg/2 bandpass filter shows the characteristic of suppression of harmonics until 8 GHz and the insertion and return losses of 0.96 and 18.89 dB, respectively, at the center frequency of 2.43 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2288–2291, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25457 [ABSTRACT FROM AUTHOR]

In this article, a narrow band pass filter with reduced size using the λg/4 short stubs is presented.The filter size is reduced by realization of transmission line at the second harmonic while the power can be transferred to the output using the fundamental frequency band generated in the resonator and the transmission line in which the impedance mismatching technique is adopted. The experimental results show that the insertion loss is 2.0 dB and return loss is 11.1 dB, and the fractional bandwidth is 10% at the center frequency of 5.8 GHz. The filter size is 19.7 × 8.6 mm2. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2002–2005, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25419 [ABSTRACT FROM AUTHOR]

This article reports a novel broadband rectifying antenna (rectenna) using the printed monopole antenna and the band-pass stub band-pass filter, which is designed in the microstrip line structure at 2.45 GHz for the wireless transmission of microwave power.We suggest a novel H-shape printed monopole antenna with size reduction of the radiator and the ground plane using surface current distribution, and a broadband stub band-pass filter with suppression of the second harmonic. The rectifying circuit with stub filter doesn't need additional area because it is fabricated on the ground plane, which is widened to acquire broadband characteristic of the monopole antenna. The RF-to-DC conversion efficiency of 66% is obtained by using a load resistor of 270 Ω at 2.45 GHz. Also, the conversion efficiency is maintained from 2 GHz to 3 GHz above 50%. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1194–1197, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25130 [ABSTRACT FROM AUTHOR]

A simplified mathematical design method for tapped-line geometry is presented and the stub bandpass filters (BPFs) of λg/4 and λg/2 stubs with a center frequency of 5.8 GHz and a bandwidth of 5% are successfully designed, fabricated, and characterized using this approach. Design parameters for the tapped-line geometry of the filter prototypes are obtained using input (output) admittance toward source (load), where the open-stub and the additional transmission-line with a negative electrical length are taken into account for filter implementation. The electrical lengths of the stubs and lines are functions of the line admittance and J-inverter. The filters are implemented on a RT-duroid substrate and the results from modeling and measurement show good agreement with each other. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2338–2341, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24615 [ABSTRACT FROM AUTHOR]

In this article, a broadband double-balanced mixer is presented using a wideband Marchand balun implementation by vertical coupler. Frequency is selected as 1.0–3.7 GHz for radio frequency (RF), 1.14–3.84 GHz for LO, and 140 MHz for IF signals. When LO signal with 7 dBm at 2.64 GHz is injected, a conversion loss of 7.5 dB, and RF to LO isolation of -45 dB are obtained. Also, an average conversion loss of 9 dB, and RF to LO isolation of -25 dB are obtained for frequency band of 1.0–3.7 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1811–1814, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24488 [ABSTRACT FROM AUTHOR]

In this article, λg/2 open stub bandpass filters with flexible narrow bandwidth on duroid substrate are presented. This filters show flexible bandwidth with variation of the position of the open stubs using the external quality factor, Qe without changing the impedance value at microwave range. On the other hand, by replacing the series quarter-wavelength connecting-lines with the equivalent T-shaped line, a compact stub bandpass filter with second harmonic suppression can be obtained. This filter shows the insertion loss of 1.2 dB and the return loss of 21.9 dB at the center frequency of 5.8 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1763–1766, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23492 [ABSTRACT FROM AUTHOR]

In this paper, the harmonics suppressed waveguide filter with SIW (substrate-integrated waveguide) structure using inductive windows at satellite communication band is discussed. The SIW structure is realized by via-holes and can be integrated with other circuits on the same substrate. The SIW filter has the insertion loss of 2.85 dB and return loss of 17.57 dB at the center frequency of 12 GHz. Also, the proposed SIW filter has the harmonics suppression under 20 dB until 30 GHz by inserted low-pass filter (LPF). This harmonics suppressed SIW filter can be used in satellite communication systems. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 447–450, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23114 [ABSTRACT FROM AUTHOR]

In this article, the potential feasibility of integrating BST films into Si wafer by adopting tunable interdigital capacitor (IDC) with TiO2 thin film buffer layer is suggested. TiO2 as buffer layer is grown onto Si substrate by atomic layer deposition and the coplanar IDC on BaxSr1-xTiO3(500 nm)/TiO2(50 nm)/high resistivity Si (HR-Si) is fabricated. BST interdigital tunable capacitors integrated on HR-Si substrate with high tunability and low loss tangent are characterized for their microwave performances. BST/HR-Si and BST/TiO2/HR-Si IDCs show much enhanced tunability values of 31% and 40%, respectively as compared to the value of 21% obtained with BST film on MgO single crystal substrate at the bias of 5 kV/cm. BST/TiO2/HR-Si structure shows much improved figure of merit of 504.4 as compared to 418.53 and 101.68 of BST/MgO and BST/HR-Si structure, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2144–2148, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22657 [ABSTRACT FROM AUTHOR]

In this paper, a broadband microstrip Marchand balun is presented. It is implemented by new vertical coupled structure, which is suggested to improve the coupling effect in the conventional coupler. Using this vertical coupling structure, the Marchand balun shows broad bandwidth of larger than 115% at the center frequency of 2.3 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 752–755, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22281 [ABSTRACT FROM AUTHOR]

This study presents a frequency tripler using APDP (anti-parallel diode pair) in which a new structure of bandpass filter (BPF) with low insertion loss and small size is adopted instead of a conventional coupled line BPF. The tripler using the proposed filter is measured and compared with the one using a conventional coupled line BPF. This BPF shows the insertion loss of less than 0.7 dB within the bandwidth of 16.41–19.23 GHz. The conversion loss of the tripler is about 16.6–18.5 dB with flatness of less than ±1 dB at the fundamental frequency of 5.72–6.28 GHz. The suppression characteristics for the first and fifth harmonic signals at 6.1 GHz are -32.16 and -44.6 dBc, respectively, and its phase noise attenuation is about 9.5 dB at 100 kHz offset. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1770–1773, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21787 [ABSTRACT FROM AUTHOR]

In this paper, a new microstrip stepped-impedance hairpin resonator with interdigital capacitor (IDC) slow-wave band-pass filter (BPF) using dielectric supported air-gapped microstrip line (DAML) of surface micromachining on GaAs substrate is proposed. Unlike conventional slow-wave filters, the proposed bandpass filters are designed to produce a narrow passband at the fundamental mode of the resonators with small size and a sharp skirt characteristic. The proposed slow-wave band-pass filter with IDC is designed to produce a passband of 7.7% at the fundamental frequency of 56 GHz. It shows insertion loss of 3.37 dB, return loss of better than 15 dB, and a stopband characteristic greater than 31 dB within 37.03–45.51 GHz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1244–1247, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21667 [ABSTRACT FROM AUTHOR]

This paper presents the design and experimental results of the new miniaturized elliptic coplanar bandpass filter (EC BPF) using two types of double stepped impedance resonators (DSIRs) operating at a center frequency of 1.38 GHz. Miniaturization in the proposed BPF is achieved by connecting the transmission line between the middle of two SIRs contained in a single DSIR and both grounded planes. In addition, bond-wire bridges connected between both grounded planes (which are needed in various coplanar waveguide structures) are not required. The new four-pole EC-DSIR BPF shows good agreement with the simulation data obtained by full-wave EM simulations using Zeland IE3D ver. 10.06. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1059–1063, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21600 [ABSTRACT FROM AUTHOR]

In this paper, new microstrip cross-coupled elliptic function (CCEF) bandpass filters (BPFs) using folded split-ring resonators (FSRR) are proposed. The CCEF BPFs using these resonators are designed with maintaining a good filter performance and reducing the size significantly. The four-pole and three-pole CCEF BPFs show a 3-dB bandwidth of 3.0% at the center frequency of 2.0 GHz, and insertion losses of 4.28 and 2.77 dB, respectively. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 491–494, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21388 [ABSTRACT FROM AUTHOR]

In this paper, a new microstrip stepped-impedance hairpin resonator (SIR) low-pass filter (LPF) using a defected ground structure (DGS) is proposed. The proposed SIR hairpin low-pass filter using DGS provides a very sharp cutoff frequency response with low insertion loss. Furthermore, the SIR hairpin low-pass filter can provide attenuation poles for the wide-stopband characteristic due to the resonance characteristic of the DGS. Design parameters for the SIR low-pass filter are derived based on stepped-impedance theory and the equivalent-circuit model for the DGS. The experimental results show excellent agreement with the theoretical simulation results. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 405–408, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21364 [ABSTRACT FROM AUTHOR]

In this paper, a new microstrip stepped-impedance hairpin resonator (SIHR) slow-wave bandpass filter (BPF) using a dielectric-supported air-gapped microstrip line (DAML) via surface micromachining on GaAs substrate is proposed. The slow-wave periodic structures utilize the parallel- and series-resonance characteristics of the resonators to construct a band-pass filter. The proposed slow-wave band-pass filter is designed to produce a passband of 10% at the fundamental frequency of 60 GHz. It exhibits insertion loss of 2.23 dB, return loss of better than 15 dB, and a stopband greater than 35 dB. This filter is useful for many millimeter-wave system applications. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 86–89, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21089 [ABSTRACT FROM AUTHOR]

In this paper, novel microstrip open-loop resonator (OLR) bandpass filters are presented. By introducing additional spiral inductors as well as gap-coupled capacitors, the bandpass filters (BPFs) exhibit another attenuation pole at the upper stopband. Also, a novel miniaturized high-Q duplexer for Universal Mobile Telecommunications System (UMTS) bands using these BPFs is discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 69–72, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20904 [ABSTRACT FROM AUTHOR]

In this paper, a new class of cross-coupled planar microwave filters using the microstrip edge-coupled split-ring resonator (EC-SRR) is introduced and its simple equivalent circuit is proposed. The utilization of the microstrip split-ring resonators not only makes the filters compact, but also allows either positive or negative cross coupling to be realized. Also, three-pole and four-pole cross-coupled microstrip elliptic function bandpass filters using the EC-SRR are presented. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 495–499, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20862 [ABSTRACT FROM AUTHOR]

In this paper, a microstrip active resonator oscillator (ARO) for X-band application is presented. The ARO is implemented on Teflon substrate with relative dielectric constant of 2.52, height of 0.54 mm, and metal thickness of 0.017 mm. The ARO shows 6-dBm output power at 10 GHz, 2nd-harmonic suppression of -20.1 dBc, phase noises of -57.27 and -92 dBc/Hz at the offset frequencies of 1 and 100 kHz, respectively, and a frequency tuning range of 43.7 MHz with 0.05% output error. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 472–475, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20505 [ABSTRACT FROM AUTHOR]

This paper presents the design of a high-efficiency LDMOS power-amplifier module (PAM) at the 880-MHz band. The nonlinear parameters for the LDMOS FET are obtained through the modified SPICE level-3 static and large-signal analyses. It shows an output power of 30.2 dBm and power-added efficiency (PAE) of 64%, with a transducer power gain of 28.78 dB. In this paper, the harmonic-trap network (HTN) is introduced to maximize the PAE and the winding transmission line (WTL) is adopted to obtain the optimizing output matching point between the output power and PAE. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 164–167, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11317 [ABSTRACT FROM AUTHOR]

The mutual coupling between cylindrical–rectangular microstrip patch antennas with a cylindrical superstrate is analyzed with the use of the conformal FDTD (CFDTD) method. The method is also applied to antennas mounted on flat structures for comparison. The effects of superstrate permittivity and thickness on the mutual coupling between cylindrical–rectangular microstrip patch antennas are presented. Curvature effects on the mutual coupling are also shown. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 64–68, 2002 [ABSTRACT FROM AUTHOR]

A new bandpass filter that is composed of two-stage microstrip-ring resonators with a center frequency of 5.775 GHz and a bandwidth of 100 MHz is presented in this paper. For the suppression of unnecessary harmonics, low-pass filters are integrated into a microstrip-ring resonator. A harmonic suppression ratio of about 35 dB for this structure is obtained. Also, a varactor-tuned microstrip-ring bandpass filter with harmonic suppression is suggested, and an insertion loss of 6 dB and a tuning bandwidth of 450 MHz are obtained. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 26–29, 2001. [ABSTRACT FROM AUTHOR]

In this article, a K-band push-push Voltage Controlled Oscillator (VCO) is presented using a miniaturized hairpin resonator (MHR) with a higher loaded quality factor and the reduced circuit area within 50% compared to the conventional one at 9.2 GHz.The MHR combined with the GaAs MESFET varactor shows a tuning range of 140 MHz, and this voltage tunable MHR is used to compose a push-push VCO. It provides the frequency tuning range of 71 MHz with flatness of +0.13 dB, which is increased by 31 MHz compared to the conventional VCO. The voltage controlled push-push oscillator based on the series feedback topology is implemented on 0.54 mm-thick Teflon substrate with a dielectric constant of 2.54. The measurement shows the output power of 1.18 dBm, the fundamental signal power suppression of -33 dBc, and phase noise performance of -86.78 dBc/Hz at 100 kHz offset. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 699–701, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25007 [ABSTRACT FROM AUTHOR]

In this article, a new high Q resonator is presented and it is applied to the design of an I-band oscillator. The measurement of the resonator itself shows that it provides a higher loaded quality factor when compared with the spiral-resonator. The oscillator is designed to be operated at 10 GHz using the new resonator to confirm the phase noise performance. The measurement results for the new hair-pin resonator oscillator show the output power of 8.18 dBm and the phase noise of -103.48 dBc/Hz at 100 kHz offset. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1172–1174, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24283 [ABSTRACT FROM AUTHOR]

In this paper, a single balanced diode mixer using harmonic-suppressed defected ground structure (DGS) low-pass filter (LPF) with dumbbell shape is presented. The frequency bandwidth selected is C-band, with 5.72–5.82 GHz for RF, 5.58–5.68 GHz for LO, and 140 MHz for IF signals. A rat-race hybrid is designed for the accomplishment of the single balanced type of mixer. A low-pass filter using DGS is used for good conversion loss and unwanted 2nd and 3rd harmonic suppression. The mixer is compared to a reference mixer with conventional low-pass filter. When an LO signal with power of 4 dBm at 5.635 GHz is injected, a conversion loss of 6.2 dB is observed for the mixer. Also, LO-to-RF and LO-to-IF isolations of 30 dB and 40 dB are obtained, respectively. This mixer can be used in the area for wireless LAN application. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 423–425, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20489 [ABSTRACT FROM AUTHOR]

In this paper, a balanced amplifier with coplanar waveguide structure for wireless LAN applications is presented. To reduce the input VSWR and improve stability, the balanced characteristic is adopted for the amplifier's design. The balanced amplifier is designed by several microwave simulation tools, such as Agilent ADS ver. 1.3, Agilent HFSS ver. 5.6, IMST COPLAN ver. 2.3, and Zeland IE3D ver. 8.0. The new branch-line coupler shows an insertion loss of 3.5 dB and input/output return losses of greater than 20 dB at 5.8 GHz. The balanced amplifier, using a new CPW branch-line coupler, shows a gain of about 10 dB at 5.8 GHz. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 349–351, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11213 [ABSTRACT FROM AUTHOR]

This paper presents measured results for the improved bandwidth of a microstrip antenna using coupling techniques in conjunction with matching circuits. The proposed technique is applied to probe-fed and aperture-coupled microstrip antennas. The measured bandwidth for a probe-fed and an aperture-coupled antenna is increased up to about 14%, which can be further increased by obtaining the proper size of the impedance locus and using the matching technique. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 79–81, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11133 [ABSTRACT FROM AUTHOR]

Wavelets have been applied in conjunction with the measured equation of invariance (MEI) to solve a two-dimensional scattering problem. The MEI method with wavelet metrons is referred to as the wavelet MEI method. Haar wavelets are used as metrons. The proposed method leads to a significant savings in CPU time compared to the standard MEI method that does not use wavelets as metrons. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 47–49, 2002; DOI 10.1002/mop.10227 [ABSTRACT FROM AUTHOR]

One of the most important design parameters in a microwave radio transmitting system is to reduce the spurious response from an output spectrum. The spurious signal is primarily due to local oscillator (LO) leakage. Applying the leakage reduction (LR) signal that has the same magnitude and is 180° out of phase with respect to the LO leakage signal, the spurious response can be significantly reduced. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 379–381, 2002. [ABSTRACT FROM AUTHOR]

In this letter, a transverse slit within the signal line in a coplanar waveguide (CPW) structure is modeled as series inductance and parallel capacitance, and the simple formulas for the capacitance and the inductance are introduced. Also, a broadband harmonic-suppressed filter (12.5–50 GHz), a band-rejection filter, and a finite-ground (FG)–CPW low-pass filter (LPF) with this structure are demonstrated. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 426–428, 2001. [ABSTRACT FROM AUTHOR]