Band-stop Circuit Research Articles

Analysis and research of EMI filter based on SiC power device

The new electronic devices represented by SiC have brought new opportunities to improve the efficiency and power density of the drive circuit system. However, the complex circuit drive system using the new electronic devices still faces many challenges to give full play to its advantages. This paper focuses on the electromagnetic interference of drive circuit. Research on Filter Circuit, through in-depth study of the filter circuit, several second-order active circuits are proposed to filter the signal interference of the conduction path. Finally, an adjustable quality factor bandstop circuit is designed. The proposed circuit has good adjustment and feedback functions when filtering interference signals.

Hybrid loop/monopole antenna with a passive bandstop circuit for the LTE/GPS operation in the tablet computer

ABSTRACTA hybrid loop/monopole antenna capable of covering the LTE operation in the 698–960/1710–2690 MHz band and the GPS operation at 1575 MHz for the tablet computer application is presented. With the obtained LTE/GPS operation, the antenna requires a small size of 8 × 40 × 3 mm3 only. The antenna is operated as a coupled‐fed loop antenna for the LTE operation and as a coupled‐fed monopole antenna for the GPS operation. The two antenna structures share the same radiation strip, except that the loop antenna with the end terminal thereof short‐circuited to the device ground plane of the tablet computer and the monopole antenna with the end terminal thereof open‐ended. The two antenna structures are configured into one antenna structure using a passive bandstop circuit connected between the end terminal of the antenna's radiation strip and the device ground plane. The bandstop circuit exhibits a very high impedance in the GPS band and a very low impedance in the LTE band, thereby making the antenna operated as a loop antenna for the LTE operation (698–960/1710–2690 MHz) and a monopole antenna at 1575 MHz for the GPS operation. Details of the proposed hybrid loop/monopole antenna are described. Operating principle of the antenna is addressed, and experimental results of the fabricated antenna are presented and discussed. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:630–635, 2016

Dual‐inverted‐F antenna with a decoupling chip inductor for the 3.6‐GHz LTE operation in the tablet computer

ABSTRACTA simple, decoupled dual‐inverted‐F antenna (DIFA) formed by two inverted‐F antennas (IFAs) with a decoupling chip inductor is presented. The open ends of the two IFAs face to each other and are connected by the decoupling chip inductor. The DIFA has a planar structure and is easily fabricated on a thin dielectric substrate. Good isolation between the two IFAs can be obtained, owing to an equivalent bandstop circuit formed by the decoupling chip inductor and the equivalent distributed capacitor between the open ends of the two IFAs. For the tablet computer application in the 3.6‐GHz LTE band (3.4–3.8 GHz), the DIFA with a decoupling chip inductor of 39 nH occupies a small size of 20 × 4 mm2 on a 0.8‐mm thick FR4 substrate. The two IFAs in the DIFA almost require no isolation spacing, thereby leading to the compact structure and small size. Details of the proposed DIFA are described, and its multi‐input multioutput performance is discussed. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2189–2194, 2015

A Novel Compact Balun Using a Weakly Coupled Line With Grounded Resonator

A compact balun is proposed using a very weakly coupled line loaded with a parallel resonator. Based on an equivalent circuit model, the balun behaves as a matching network for odd-mode operation and a bandstop circuit for even-mode operation. The proposed balun can exhibit a broad bandwidth from 2.4 to 3.6 GHz with return loss of S 11 below 10 dB. This balun provides only 0.1 dB amplitude difference and gives 180 ° ±5 ° of phase difference between S 21 and S 31. The electrical size is only 0.088 λg ×0.078 λg and fractional bandwith is 40%. Different from previous broadband baluns, the proposed balun can be implemented in low coupling-coefficient structures, which means complex strongly coupled lines (more than two wires) aren't required. This idea is one of the main reasons to achieve a very compact balun.

Internal coupled‐fed loop antenna integrated with notched ground plane for wireless wide area network operation in the mobile handset

AbstractAn internal wireless wide area network (824–960/1710–2170 MHz) antenna suitable to be disposed at a notched region (size 10 × 40 mm2) of the system ground plane of the handset to achieve compact integration therein is presented.The notched system ground plane, compared to the traditional rectangular system ground plane at which the internal antenna is generally disposed at the entire top or bottom edge of the ground plane, can lead to more compact layout design of the internal antenna and associated electronic elements in the handset. The proposed antenna has a simple structure occupying a small volume of 10 × 40 × 5 mm3 and comprising a monopole feed and a coupled strip. The latter is coupled‐fed by the monopole feed to provide a 0.25‐wavelength loop path, which generates a 0.25‐wavelength loop mode at about 850 MHz and a higher‐order loop mode at about 1.7 GHz. The monopole feed also contributes a 0.25‐wavelength mode at about 2.1 GHz to combine with the higher‐order loop mode to form the antenna's upper band. The bandwidth enhancement of the 0.25‐wavelength loop mode is obtained by adding an external bandstop circuit, which makes the desired antenna's lower band achieved. The antenna also meets the specific absorption rate and hearing‐aid compatibility requirements for practical applications. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:553–555, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26620

Design of Multilayer Dual-Band BPF and Diplexer with Zeros Implantation Using Suspended Stripline

In this paper, a dual-band bandpass filter (BPF) of multilayer suspended stripline (SSL) structure and an SSL diplexer composed of a low-pass filter (LPF) and a high-pass filter (HPF) are proposed. Bandstop structure creating transmission zeros is adopted in the BPF and diplexer, enhancing the signal selectivity of the former and increasing the isolation between the diverting ports of the latter. The dual-band BPF possesses two distinct bandpass structures and a bandstop circuit, all laid on different metallic layers. The metallic layers together with the supporting substrates are vertically stacked up to save the circuit dimension. The LPF and HPF used in the diplexer structure are designed by a quasi-lumped approach, which the LC lumped-elements circuit models are developed to analyze filters' characteristics and to emulate their frequency responses. Half-wavelength resonating slots are employed in the diplexer's structure to increase the isolation between its two signal diverting ports. Experiments are conducted to verify the multilayer dual-band BPF and the diplexer design. Agreements are observed between the simulation and the measurement.

Internal WWAN antenna for the clamshell mobile phone with various chassis shapes

AbstractStable performances of an internal WWAN antenna applied in the clamshell mobile phone with various chassis shapes are obtained. Six different states including five possible operating states and one closed state (idle condition) of the clamshell mobile phone, wherein the chassis shapes (main ground and upper ground) vary greatly, are studied. The WWAN antenna is mounted at the bottom of the main ground, and there are three connecting positions between the main ground and the upper ground. For each operating states, the upper ground is connected to the main ground at one of the three connecting positions. At each position, a band‐stop circuit formed by two parallel LC chip elements is embedded, which is designed to excite a parallel resonance at around 900 MHz and hence leads to very high impedance seen into the upper ground in the 900 MHz band. This greatly decreases the excited surface currents on the upper ground, making the presence of the upper ground to have very small effects on the performances of the WWAN antenna mounted at the bottom of the main ground. At around 1900 MHz, owing to its shorter wavelength, the surface currents on the upper ground excited by the WWAN antenna on the main ground are small. Thus, over both the 900‐ and 1900‐MHz bands, the various orientations of the upper ground to the main ground cause small effects on the WWAN antenna embedded therein. Details of the obtained results are presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2148–2154, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25413

Internal wireless wide area network clamshell mobile phone antenna with reduced ground plane effects

AbstractAn internal wireless wide area network (WWAN) antenna applied in a clamshell mobile phone having an equivalent band‐stop circuit at the hinge to decrease the upper ground plane effects of the mobile phone on the antenna performances is presented. The internal WWAN antenna in this study is a small‐size printed monopole mounted at the bottom of the main ground. This band‐stop circuit can perform a parallel resonance at around 900 MHz and leads to high impedance seen into the upper ground in the 900 MHz band, which greatly decreases the excited surface currents on the upper ground. At around 1900 MHz, owing to its shorter wavelength, the surface currents on the upper ground excited by the internal antenna on the main ground are small for both the traditional and proposed clamshell mobile phone structures. Hence, over the WWAN operating bands, the presence of the upper ground shows very small effects on the impedance matching and radiation characteristics of the antenna on the main ground. The SAR and HAC studies on the proposed clamshell mobile phone structure are also presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:922–930, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25056

Gallia est omnis divisa in partes tres

The name "Bartlett's bisection theorem" has been given to three entirely different bisection principles. One alone is used both in synthesizing a three-reactor bandstop circuit having the delay properties of a Bessel n=4 low-pass circuit and also in finding its step drive and its superior amplitude characteristics.