双频带通滤波器的优化设计

利用阶跃阻抗谐振器优化,设计了一个工作在无线局域网(2.4/5.2GHz)的双频带通滤波器。通过奇、偶模分析,在阶跃阻抗谐振器理论计算公式基础上,根据不同的阻抗比条件,阶跃阻抗谐振器谐振频率比与阶跃阻抗高、低阻抗电长度之比的关系曲线,可以方便地确定阶跃阻抗谐振器的谐振频率和电长度,通过sonnet电路仿真软件验证了设计的合理性,并给出了用于无线通信2.4、5.2 GHz双频带通滤波器的设计结果。该带通滤波器可以分别在2.4、5.2 GHz处得到较好的通带性。由于交叉耦合的存在,该双频带通滤波器在两个通带端各有一个传输零点,以此来提高滤波器的通带频率选择性。最后,测量结果与仿真结果基本吻合。     

A Compact Dual-Band Bandpass Filter Using Meandering Stepped Impedance Resonators

This letter presents a miniaturized dual-band narrow bandpass filter (BPF) using meandering stepped impedance resonators (SIRs) with a new coupling scheme, which exhibited a size reduction of 50% compared with the traditional direct coupling structure at the same frequency, while the new structure can generate three transmission zeros in the insertion loss response. To validate the design and analysis, two dual-band BPFs centered at 2.4-GHz/5.2-GHz and 2.4-GHz/5.7-GHz for WLAN application were fabricated and measured. It is shown that the measured and simulated performances are in good agreement. The BPFs achieved insertion loss of less than 2 dB and return loss of greater than 16-dB in each band.     

A Dual-Band Filter Realized by Alternately Connecting the Main Transmission-Line With Shunt Stubs and Shunt Serial Resonators

In this letter, we present a novel network for dual-band filter, the circuit of which is a mixture of shunt stub bandpass filter and shunt serial resonator bandstop filter. The stopband of the bandstop filter will split the passband of the bandpass filter and result in a dual-band response. The simulated and measured results are given. This kind of filter has the advantage of bigger and controllable bandwidths and lower insertion loss compared with traditional SIR dual-band filters.      

Asymmetric Dual-Passband Coplanar Waveguide Filters Using Periodic Composite Right/Left-Handed and Quarter-Wavelength Stubs

A novel dual-passband coplanar waveguide (CPW) filter periodically loaded with the composite right/left-handed (CRLH) short-circuited stubs and the quarter-wavelength open-circuited stubs in asymmetric configuration is presented. The unit-cell equivalent circuit of the periodic structure in conjunction with Floquet's theorem is employed to find the propagation characteristics of passband and stopband regions. Unlike the conventional quarter-wavelength transmission-line inverter suitable only for a narrow frequency range, the dual-band inverter is adopted in the dual-passband filter to achieve a better frequency response within two operating bands. The performance of the 2.4/5.8-GHz third-order CRLH CPW dual-passband filter with 52% and 23% bandwidths is measured and validated by full-wave simulation. Two arbitrary passband regions are presented and the stopband within the passbands can be controlled by varying the length of open-circuited stub, supporting the flexibility and compactness of the proposed dual-passband filter     

Capacitive-Ended Interdigital Coupled Lines for UWB Bandpass Filters With Improved Out-of-Band Performances

This letter presents a novel ultra-wideband (UWB) microstrip bandpass filter on a microstrip line with improved out-of-band performances. A multiple-mode resonator (MMR) is first constituted to equally allocate its first three resonant frequencies in the 3.1–10.6-GHz UWB band. Two capacitive-ended interdigital coupled lines are then formed to assign their transmission zero towards the fourth-order resonant frequency of this MMR, thereby suppressing the first spurious passband. Moreover, two outer arms in the interdigital lines are properly tapered to compensate the phase imbalance or group delay near the UWB upper-end relying on extra capacitive-ended stubs. And finally, two UWB filters with one- and two-MMRs are designed and implemented to experimentally demonstrate the improved out-of-band performances, i.e., widened/deepened upper-stopband and sharpened rejection skirts outside the UWB passband.     

Design of Dual-Band Bandpass Filters Using Stub-Loaded Open-Loop Resonators

In this paper, open-loop resonators loaded by shunt open stubs are proposed to design compact dual-band bandpass filters with improved out-of-band rejection characteristics. The second passband of the dual-band filter is obtained by tuning higher resonant modes of the open-loop resonator by the stub length and position. A tapped-line input/output feed structure is used for external coupling. Required external coupling is obtained by adjusting the tapping position and dimension of the stub-loaded resonator. A lossless transmission line model is used to determine the resonance properties of the resonator and the external quality factor. Theoretical predictions are verified by the experimental results of three dual-band filters.     

Dual and tri-band bandpass filters based on novel Π-shaped resonator

A novel Π-shaped resonator is proposed, and compact dual-band and tri-band bandpass filters that meet IEEE 802.11 application requirements by using the new resonator are designed. The dual-band bandpass filter centres at 2.45 and 5.6 GHz with a simulated passband insertion loss of no more than 0.8 dB, and the tri-band bandpass filter which is got by two-path coupling achieves simulated passband insertion loss of no more than 1.1 dB. The new designs are demonstrated by experiment. The new filters have advantages of simple and compact structures, low passband insertion losses, good frequency selectivity and miniature circuit sizes. All these have prospect to be applied in future wireless communication systems.     

Dual-Band Adjustable and Reactive I/Q Generator With Constant Resistance for Down- and Up-Converters

Adjustable and reactive in-phase/quadrature (I/Q) generators with constant resistance are proposed for the first time in this paper with the properties of low loss, dual-band implementation, and high quadrature accuracy. The quadrature phase property and input matching of the I/Q generator can be achieved at all frequencies simultaneously by the constant-resistance I/Q generator. However, the magnitude balance of the dual-band I/Q generator is achieved at two designed frequencies. A 2.4/5.2-GHz I/Q down-converter and a 2.4/5.7-GHz single-sideband up-converter are fabricated using 0.35- $mu{hbox{m}}$ SiGe BiCMOS technology. The dual-band I/Q generator along with two single-to-differential amplifiers is integrated to provide differential quadrature local oscillator signals for dual-band mixers. The magnitude imbalance and phase error between the I and Q channels of the down-converter are $≪$1% and $≪{hbox{1}}^{circ}$, respectively, while the maximum sideband rejection ratio of the up-converter is up to 50 dB. Additionally, the operation bandwidth (sideband rejection ratio $> $30 dB) is 200 MHz at 2.4 GHz and 720 MHz at 5.7 GHz.      

Dual-Mode Dual-Band Bandpass Filter Using Stacked-Loop Structure

In this letter, a dual-mode dual-band bandpass filter using stacked-loop structure is proposed, which allows two transmission paths to radio frequency (RF) signals. Each of them using dual-mode resonators results in respective passband. This can provide convenience to easily change one passband frequency, while another keeps almost the same. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed bandpass filter. The theoretical and measured results are presented and show good agreement.     

Variable Bandpass Filters Using Varactor Diodes

A rectangular waveguide type variable bandpass filter for the 4-GHz bandpass has been proposed and tested. The bandpass width varies from 260 MHz to 1.02 GHz for a filter using varactor diodes. Two microstrip variable bandpass filters for the 6-GHz and 4-GHz bands are also proposed and tested. The passband width varies from 310 MHz to1.24 GHz for a varactor-diode coupled filter, and it varies from 380 MHz to 2.18 GHz for a filter which is composed of low-pass and high pass filters connected in cascade. The center frequency of the three filters can be changed arbitrarily.     

A 60-GHz Millimeter-Wave Bandpass Filter Using 0.18-μm CMOS Technology

This letter presents the design and implementation of a 60-GHz millimeter-wave RF-integrated-circuit-on-chip bandpass filter using a 0.18-mum standard CMOS process. A planar ring resonator structure with dual-transmission zeros was adopted in the design of this CMOS filter. The die size of the chip is 1.148times1.49 mm². The investigations of sensitivity to the insertion loss and the passband bandwidth for different perturbation stub sizes are also studied. The filter has a 3-dB bandwidth of about 12 GHz at the center frequency of 64 GHz. The measured insertion loss of the passband is about 4.9 dB, and the return loss is better than 10 dB within the passband.     

Dual-Band Bandpass Filter Design Using a Novel Feed Scheme

A planar dual-band bandpass filter based on a novel feed scheme is presented in this letter. The proposed filter employs two sets of resonators operating at diverse frequencies to generate two passbands. A novel scheme is introduced to feed the resonators. One set of resonators is utilized to not only generate the lower passband but also feed other resonators. Source-load coupling for upper passband is inherently realized. This scheme provides sufficient degrees of freedom to control the center frequencies and bandwidth of the two passbands. Four transmission zeros can be created close to passband edges, resulting in high skirt selectivity. To validate the proposed idea, a demonstration filter is implemented. The design methodology, filter sensitivity and experimental results are presented.      

A 1.8-V 6/9-GHz reconfigurable dual-band quadrature LC VCO in SiGe BiCMOS technology

This paper presents a dual-band voltage-controlled oscillator (VCO) that can be reconfigured between 6- and 9-GHz frequency bands. It comprises a 6-GHz LC-tuned VCO, two 1/2 dividers, two mixers, and two 3-GHz notch filters. The 9-GHz output is generated based on the analog frequency multiplication method by mixing the 6-GHz VCO output with its divide-by-two signal. The VCO, implemented in a 0.18-/spl mu/m SiGe BiCMOS technology, achieves a fast reconfiguration time of 3.6 ns. The measured VCO phase noises are -106 and -104 dBc/Hz at 1-MHz offset for 6- and 9-GHz modes, respectively, while draining 10.8 mA from a 1.8-V supply.     

2.4/5.7 GHz Dual-Band High Linearity Gilbert Upconverter Utilizing Bias-Offset TCA and LC Current Combiner

A 2.4/5.7 GHz dual-band Gilbert upconversion mixer is demonstrated using 0.35 mum SiGe BiCMOS technology. A bias-offset cross-coupled transconductance amplifier (TCA) is employed in the intermediate frequency port for the linearity improvement. The dual-band LC current combiner and the output shunt-shunt feedback buffer amplifier are in the radio frequency (RF) port. The mechanisms of the high linearity upconverter and the design flow of the dual-band LC current combiner are established in this letter. The dual-band upconverter has conversion gain of 1.5/-0.2 dB, OP_1dB, and of -10.5/-9 dBm, and OIP₃ of 12/13 dBm for IF=100 MHz, RF 2.4/5.7 GHz, respectively.     

Novel Centrally Loaded Resonators and Their Applications to Bandpass Filters

This paper presents several novel centrally loaded resonators and their applications to various types of bandpass filters. Based on the theoretical analysis, it is found that the even- mode resonance of the proposed resonators can be conveniently controlled without affecting the responses at the odd-mode resonant frequencies. Benefiting from this feature, the resonator can be utilized to design not only harmonic-suppressed bandpass filters and dual-band bandpass filters but also tunable bandpass filters. The tunable filter offers a fixed passband and a tunable one. The center frequency of the upper passband can be electrically tuned, whereas the performance of the lower one is maintained constant. To demonstrate these applications, four filters using the proposed resonators are implemented. The experiments verify the theoretical predictions and simulations.     

Dual-frequency planar inverted-F antenna

Cellular telephone handsets are now being designed to have dual-mode capabilities. In particular, there is a requirement for internal antennas for GSM and DCS1800 systems. This paper describes a novel planar dual-band inverted-F antenna for cellular handsets, which operates at the 0.9-GHz and 1.8-GHz bands. The dual-band antenna has almost the same size as a conventional inverted-F antenna operating at 0.9 GHz and has an isolation between bands of better than 17 dB. The bandwidths of the antenna are close to those required for the above systems. Good dual-band action is also obtained for other frequency ratios in the range of 1.3-2.4. Studies also show that the dual-band antenna can operate with one or two feeds. A finite-difference time-domain analysis has been shown to give calculated results close to those measured     

2.4/5.7-GHz CMOS Dual-Band Low-IF Architecture Using Weaver–Hartley Image-Rejection Techniques

A 2.4/5.7-GHz dual-band Weaver–Hartley architecture, using 0.18-$mu{hbox{m}}$ CMOS technology, is demonstrated in this paper. The 2.4-GHz signal is set to be the image signal when the desired signal is at 5.7 GHz, and vice versa. Since the Weaver and Hartley systems are combined into this architecture, the demonstrated architecture rejects not only the first image signal, but also the secondary image signal. The image-rejection ratios of the first image signal and the secondary image signal are better than 40 and 46 dB, respectively. In this paper, a diagrammatic explanation is employed to obtain the image-rejection mechanisms of the Weaver–Hartley architecture.      

基于微带贴片谐振器的高选择性双模双通带带通滤波器的研究

本文提出了基于微带贴片谐振器的高选择性双模双通带带通滤波器及一种模式分析算法.首次利用该算法分析了微带贴片的模式组成,计算了导模场的闭式解.微带贴片的耦合馈线同时作为谐振单元构成第二个通带,减小了结构尺寸.全波仿真分析（full wave analysis）结果及测试数据表明,与现有的双模双通带带通滤波器相比,本文设计的滤波器传输零点个数增加了2倍,达到11个,带外抑制度达到20dB,带内插损较小,仅为1.2dB,抑制了寄生通带.同时设计的拓扑结构复杂度较低,利于滤波器的小型化.     

Modified T-shaped planar monopole antennas for multiband operation

In this paper, we propose a novel modified T-shaped planar monopole antenna in that two asymmetric horizontal strips are used as additional resonators to produce the lower and upper resonant modes. As a result, a dual-band antenna for covering 2.4- and 5-GHz wireless local area network (WLAN) bands is implemented. In order to expand the lower band, a multiband antenna for covering the digital communications systems, personal communications systems, Universal Mobile Telecommunications Systems, and 2.4/5-GHz WLAN bands is also developed. Prototypes of the multiband antenna have been successfully implemented. Good omnidirectional radiation in the desired frequency bands has been achieved. The proposed multiband antenna with relatively low profile is very suitable for multiband mobile communication systems.     

Compact microstrip dual-band bandpass filters design using genetic-algorithm techniques

An optimization scheme based on hybrid-coded genetic-algorithm (GA) techniques is presented to design compact dual-band bandpass filters with microstrip lines. A representation scheme is proposed to represent an arbitrary microstrip circuit as a set of data structures. Each data structure in the set describes a simple two-port network with the corresponding connection method and electrical parameters. The optimization algorithm based on conventional GAs is then applied to simultaneously search for the appropriate circuit topology and the corresponding electrical parameters with dual-band characteristic. Two examples are designed and implemented to validate the proposed algorithm. In the first example, the 3-dB fractional bandwidth of the low and high bands is 35% and 17%, respectively. It has return losses larger than 10 dB from 2.14 to 2.96 and 5.14 to 6.06 GHz. In the second example, the 3-dB fractional bandwidth of the low and high bands is 9.9% and 7.9%, respectively. The return losses are larger than 10 dB from 3.37 to 3.64 and 5.27 to 5.62 GHz. The sizes of the proposed filters are nearly half as small as those of the filters presented before. All the studies are completed on a computer with a 2.4-GHz microprocessor, and the computing time of two examples is 6 and 3 min, respectively.