Novel configuration of ultra‐wide band uni‐planar configuration of complementary split ring resonator composite right/left‐handed based band pass filter with sharp roll off and good stopband attenuation

In this paper, a compact novel simple design of ultra‐wide bandpass filter with high out of band attenuation is presented. The filter configuration is based on combining an ultra‐wide band composite right/left‐handed (CRLH) band pass filter (BPF) with simple uni‐planar configuration of complementary split ring resonator (UP‐CSRR). By integrating two UP‐CSRR cells, the ultra‐wideband CRLH filter roll‐off and wide stopband attenuation are enhanced. The filter has 3 dB cutoff frequencies at 3.1 GHz and 10.6 GHz with insertion loss equals 0.7 dB in average and minimum and maximum values of 0.48 dB and 1.05 dB, respectively over the filter passband. Within the passband. The transition band attenuation from 3 dB to 20 dB is achieved within the frequency band 1.9 GHz to 3.1 GHz (48%) at lower cutoff and the frequency band 10.6 GHz to 11.4 GHz (7%) at upper stopband. Moreover, the filter has a wide stopband attenuation >20 dB in frequencies 11 GHz to 13.6 GHz (21%) and ends with 3 dB cutoff frequency at 14.8 GHz. Furthermore, the designed filter size is very compact (23 × 12 mm²) whose length is only about 0.17 λ_g at 6.85 GHz. The filter performance is examined using circuit modeling, full‐wave simulations, and experimental measurements with good matching between all of them.     

A compact realization of composite low‐pass filter for monolithic microwave integrated circuit applications

A compact realization of composite low‐pass filter is presented in this article. The filter is realized using on‐chip spiral inductors and metal–insulator–metal capacitors and features an attenuation pole near the cutoff frequency leading to a sharper attenuation response. As well, it offers good matching properties in the passband. Space‐mapping‐based algorithm is used in the design/optimization of spiral inductors toward achieving high quality factors at the filter cutoff frequency. The realization of the proposed filter is compact in size, suitable for monolithic microwave integrated circuit applications, and exhibit broad upper stopband frequency characteristics. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

声表面波三工器网络合成研究

声表面波三工器是载波聚合技术中的关键器件,在移动通信中不可或缺。三颗单滤波器直接合成三工器的插入损耗和回波损耗会严重恶化,须优化合成网络改善指标。根据三工器电路拓扑结构分析出网络合成后性能恶化的两个关键因素。通过细化二端口网络,分析各频段滤波器输入阻抗对泄漏损耗的影响,并在史密斯圆图上画出低泄漏损耗区,从理论上找到了合成后插入损耗的影响因素。利用并联导纳建立约束方程,确保网络合成后公共端各频段滤波器能够共用同一个匹配电路来改善回波损耗。优化了Band1+3+7三工器合成网络,并实际制作了测试板。经实验验证,通过调节等效输入阻抗进入低泄漏损耗区和遵守并联导纳约束方程能够有效解决三工器网络合成问题。     

Design of second‐order lumped‐element reconfigurable diplexers

This paper presents a new type of second‐order reconfigurable diplexers by using common lumped‐element dual‐resonance resonator (LE‐DRR) and LC resonators. As examples, a 0.9/1.8 GHz second‐order diplexer is firstly designed to investigate the design theory, which has merits of wide passband, low insertion loss and extremely compact size. Then, a second‐order switchable diplexer is simply designed by embedding two p‐i‐n diodes in two end‐stage LC resonators of the above diplexer to switch on/off each channel independently. Finally, the capacitors of the above diplexer are replaced by the varactor diodes, so that a second‐order tunable diplexer with two independently tuned channels is proposed. Measured results of proposed tunable diplexer show that its lower channel can be tuned from 0.492 GHz to 0.995 GHz with corresponding frequency tuning range (FTR) of 66.58%, while its upper channel can be tuned from 0.974 GHz to 1.7 GHz with FTR of 51.92%.     

Investigation of ultra‐wideband Bowtie antennas for phased array feed application

In this article, two new ultra‐wideband (UWB) dual‐polarized Bowtie antennas are investigated as the elements for a phased array feed for reflectors. In addition to its UWB impedance matching characteristic, the Bowtie antennas have stable large beam‐width and a low cross‐polar level over a wide frequency band with a compact size, which is an essence for phased array applications. The simulated and measured results state a low ohmic loss, good impedance matching (S₁₁ below ?15 dB) and good radiation performance, with a simple structure for easy manufacturing. The proposed antennas can be good candidates for phased array feed (PAF) in FAST and the SKA (square kilometer array) pathfinder PHAROS2 projects, and massive MIMO antennas in wireless communication systems.     

Compact dual‐polarized dipole antenna with high isolation using hybrid balun circuit

In this article, a crossed dipole antenna with compact size (43 × 43 mm²) and high isolation (42 dB) is proposed using a hybrid balun circuit. The hybrid balun consists of a tapered balun and a Marchand balun. The tapered balun transforms the microstrip line into the parallel feeding lines for one pair of dipoles, and the Marchand balun transforms the stripline transmission line into a couple of out‐of‐phase feeding lines for the crossed pair of dipoles. Due to the low coupling between two different baluns, a high isolation of the antenna can be achieved when the crossed dipole antenna is cascaded with the hybrid balun. Moreover, these two baluns can improve impedance matching and therefore further miniaturize the size of the crossed dipole antenna. The impedance matching of two baluns can be controlled and adjusted independently. As a result, the proposed dual‐polarized antenna has the bandwidth of 1.7 to 2.8 GHz for S11 < ?15 dB with compact size and high isolation. The proposed antenna with the hybrid balun circuit are fabricated, and the simulated and measured results meet well.     

Wideband bandpass filter based on U‐slotted SW‐HMSIW cavities

A wideband bandpass filter (BPF) is designed based on U‐slotted slow wave half mode substrate integrated waveguide (SW‐HMSIW) cavities. Similar to the substrate integrated waveguide (SIW), the SW‐HMSIW can also achieve a highpass characteristic while the lateral dimensions can be reduced by about 50%. By etching a U‐shape slot on the SW‐HMSIW cavity, a multiple‐mode resonator (MMR) can be realized, which can achieve a wide passband response and make the overall dimension of the filter much more compact. A wide passband, covering from 6.0 GHz to 10.65 GHz with a FBW about 58.13% is achieved. The measured minimum insertion losses including the losses from SMA connectors are 1.1 dB and return losses are better than 10 dB. Besides, the group delay varies between 0.2 and 0.5 ns within the passband. To validate its practicability, a wideband SW‐HMSIW BPF fabricated on a double‐layer printed circuit board (PCB) is designed and examined. The proposed filter has a more than 54% size reduction compared to the other designs reported in open literatures. The measured results have a good agreement with the simulated results. The effective size of the fabricated filter is about 27 mm × 8.55 mm.     

Design of a compact size tag antenna based on split ring resonator for UHF RFID application

In this article, a new design of miniaturized split‐ring resonator antenna using a meander line technique with a simple impedance matching method applicable to UHF‐RFID tags is presented. The new approach is based on the integration of a meander line into the radiating element of SRR to reduce the electrical tag size and a theoretical demonstration to calculate the conjugate impedance matching and directly attach the antenna with the chip. The new SRR antenna, which is printed on the flexible substrate Arlon CuClad 250LX, is designed using Alien Higgs 3 RFID ASIC whose input impedance is 25‐j190. The prototype antenna has a low‐cost compact size (18.28 mm × 18.28 mm) with a read range higher than 4 m within the RFID UHF band and with a roughly 4.2‐m peak range at 915 MHz. As a proof of behavior, a tag prototype is fabricated and measured to operate at a UHF RFID band. Based on some works' results, an optimized design is obtained with a 48% size reduction compared with the classic split ring resonator antenna and with a good impedance matching the antenna with RFID ASIC without the need for any external matching network.     

Low‐profile wideband patch antenna using double‐tuned impedance matching

A low‐profile wideband patch antenna utilizing double‐tuned impedance matching technology is investigated in this paper. To extend the operation bandwidth of the antenna, the step‐folded probe is used here to realize the double‐tuned impedance matching. Using equivalent circuit theory, the working principle of the antenna is analyzed and discussed. The full‐wave simulation is carried out to optimize the design while the prototype of the antenna is fabricated and measured. Good agreement between the simulation and measurement can be observed. The measured results show that the antenna has a height of 0.12λ_L (λ_L is the free space wavelength corresponding to lowest frequency) and the ?10 dB impedance bandwidth can cover 1.60‐2.83 GHz (55.5%). The low profile and wide operation bandwidth of the antenna make it a good candidate for wideband wireless communication systems.     

Compact Dual‐/Tri‐/Quad‐Band banpass filters using shorted stub loaded stepped‐impedance resonator

In this article, the shorted stub loaded stepped‐impedance resonator (SSLSIR) with the individually tunable first even resonant mode and first odd resonant mode is applied to design dual‐, tri‐, and quad‐band bandpass filters (BPFs). The SSLSIR dual‐band BPF with asymmetrical coupling is realized using the first even resonant modes and the first odd resonant modes of a set of SSLSIRs. Then, the high‐impedance feeding lines of SSLSIR dual‐band BPF is modified to produce a new passband, and thus a new tri‐band BPF is realized. The proposed quad‐band BPF consists of two sets of SSLSIRs with symmetrical coupling. Each of the designed circuits occupies a very compact size and has a good in‐band out‐of‐band performance. Good agreements are observed between the simulated and measured results. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:601–609, 2015.     

A self‐packaged wideband filtering power divider based on substrate‐integrated suspended line

In this study, a filtering power divider (FPD) is proposed by utilizing one T‐shaped tri‐mode stepped‐impedance resonator with input/output coupling structures based on substrate‐integrated suspended line (SISL). The circuit topology and SISL technology are combined together to reach balance in performances such as compact size, wideband, high frequency selectivity, low loss, good in‐band isolation, wide stopband, and self‐packaging so that there are no obvious flaws. Wide bandwidth and two near‐band transmission zeros are contributed by the proposed circuit topology. Good isolation can be obtained by comparing different coupling schemes with one resistor. An additional transmission zero for extending the upper stopband can be achieved by the two closely placed stubs without increasing the size of the design. Low loss and self‐packaging can be realized by SISL technology. For demonstration, a prototype is implemented with the size of 0.5λ_g × 0.28λ_g, which exhibits the 1‐dB fractional bandwidth of 26.3%, the frequency selectivity of 0.25/0.37 at the lower/upper edges of the passband, and the insertion loss of 1.1 dB (including transition) at the center frequency (f₀) of 3.34 GHz, while the in‐band isolation is higher than 20 dB and the 15‐dB stopband is achieved up to 3.74 f₀.     

Dual‐band band pass filter using stub‐loaded open‐loop resonators with wide controllable bandwidths

Two dual‐band band pass filters (BPF) using stub‐loaded open‐loop (SLOL) resonator are presented in this article. A novel coupling tuning method by changing the relative coupling position of the resonators is proposed to control the bandwidth of each passband in a wide range. Transmission zeros are created to improve the selectivity by source‐load coupling. Because of the large ratio of two bandwidths, a novel dual‐band matching method is proposed to match the different load impedances at two passband frequencies to the same source impedance. Hence, relax the fabrication requirement of gap. The proposed dual‐band band pass filter is designed and fabricated. The measured 3 dB fractional bandwidths (FBWs) of two 2.45/5.25 GHz dual‐band BPFs are 6.5%/14.5% and 9.8%/5.5%, respectively. The results are in good agreement with the simulation. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:367–374, 2014.     

A tunable 0.86‐3.83 GHz bandpass filter with high selectivity

This letter presents a tunable bandpass filter (BPF) with wide tuning range of center frequency and high selectivity. The wide frequency tuning range is achieved by two pairs of switchable varactors‐tuned parallel coupled line resonators with direct‐feed structure, which can be switched to lower and higher frequency resonator modes by using p‐i‐n diodes. Since the electromagnetic mixed coupling and frequency‐variant source‐load coupling are incorporated in this configuration, three self‐adaptive transmission zeros (TZs) close to the tunable passband are obtained. Also, three TZs can almost keep the same relative location of passband to achieve continuous high selectivity and good out‐of‐band rejection over the whole frequency tuning range. Meanwhile, by selecting a proper coupling region, a constant fractional bandwidth (CFBW) in the frequency tuning process can be realized. For verification, a tunable 0.86‐3.83 GHz BPF with a 12% CFBW and high selectivity is designed, fabricated and measured. The experimental results show the proposed filter has the advantages of wide tuning range and high selectivity.     

Compact low‐cost microstrip lowpass filter with sharp roll‐off and wide attenuation band

A compact low‐cost lowpass filter (LPF) with sharp roll‐off and wide attenuation band using stepped impedance resonator loaded with interdigital fingers and U‐shaped resonator is recommended in this article. The proposed LPF has a cut‐off frequency of 1.2 GHz with a sharp roll‐off 135 dB/GHz and passband insertion loss 0.35 dB. An array of two different shapes of defected ground structures are etched in the ground plane for introducing additional transmission zeroes to enhance the stopband performance. The relative stopband suppression is achieved up to 171% with a suppression factor of 2. The proposed structure is modelled, fabricated, and measured. The measurement results are found to be well‐matched with the simulated ones. Eventually, a high figure of merit of 21 600 is achieved.     

Compact UWB microstrip lowpass filter with novel CMRC

A novel beeline compact microstrip resonant cell, entitled BCMRC (beeline compact microstrip resonant cell), is firstly proposed and analyzed. The photonic bandgap and slow‐wave effect of the BCMRC are evaluated. The compact configuration presents ultrawide stopband and improved slow‐wave characteristics. Investigation of its scattering/radiation level is also included. An ultrawide band lowpass filter, consisting of three BCMRCs connected in series, is designed and fabricated. The filter has the advantages of low insertion loss in the passband, sharp, high and wide rejection in the stopband and compact size. The experimental results show good agreements with simulation results. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Compact tri‐band BPF applying novel multi‐mode microstrip resonator

This article presents a novel multi‐mode microstrip resonator. Using the even‐odd‐mode method, its resonance characteristics are analyzed and the design graphs are given. Each mode equivalent circuit is a λ/4 stepped impedance resonator (SIR), so the proposed resonator has a compact size and the higher harmonics can be tuned in a wide range. Stub–stub coupling is introduced to split two identical modes and produce two transmission zeros (TZs). Then a tri‐band filter operating at 1.5, 2.4, and 3.8 GHz is designed using the proposed resonator. The three center frequencies and bandwidths can be independently controlled. By tuning the impedance and length ratios of the stubs, wide upper stopband is achieved. Finally, the designed filter is fabricated and measured, and the measured results agree well with the simulated ones. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:559–564, 2016.     

A broadband quasi‐Yagi array of rectangular loops on LTCC

In this article, a broadband quasi‐Yagi array of rectangular loops using low‐temperature co‐fired ceramic technology is proposed. The antenna is fed by a simple and compact microstrip‐to‐coplanar strip transition, which serves as balun and impedance transformer simultaneously. Four rectangular loops are used to direct the antenna propagation toward the end‐fire direction. Compared with the planar directors in traditional quasi‐Yagi antenna, they can provide better director effect to improve the radiation performance. Furthermore, they act as good impedance matching elements to broaden the bandwidth. The measured results show that the proposed antenna achieves a wide bandwidth of 42% for S₁₁ < ?10 dB (from 26.1 to 40 GHz), better than 12 dB front‐to‐back ratio, smaller than 14 dB cross polarization and an average gain over 6.5 dBi across the operating bandwidth. The antenna occupies a compact size of 8 × 8 × 1 mm³. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:196–203, 2014.     

Frequency reconfigurable RF circuits using photoconducting switches

Designs for a frequency switchable dual‐band branch‐line coupler and a reconfigurable S‐band power amplifier input matching network with photoconducting switches are presented. Frequency switching is achieved by increasing the power of the laser applied to the highly resistive silicon wafer and changing the properties of silicon under optical illumination. The advantages of this approach are high‐speed switching, electromagnetic transparency (no interference), and thermal and electrical isolation between the device and the control circuit. A branch‐line coupler frequency shift of 35% and 10% has been achieved from all switches off to all switches on in lower (900 MHz) and upper (1800 MHz) frequency bands, respectively. Frequency switchable class AB power amplifier with silicon switch in the input matching circuit has obtained the frequency tuning range of 2.5–3.5 GHz with no significant loss in efficiency and linearity. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Dual‐band filter with high selectivity and wide stopband rejection

This article presents a highly selective dual‐passband filter based on stepped‐impedance‐resonator (SIR) and mixed electromagnetic coupling. First, the surface area of the filter is effectively reduced by the triangular topology. Second, four controllable transmission zeros are introduced by source‐load coupling feed and mixed electromagnetic, which increases the selectivity of the filter. Third, a perturbation structure is added to independently control the resonance points of each passband. Finally, the improved defect ground structure (DGS) is integrated to obtain wide stopband rejection. The measured S‐parameters are well agreement with the simulated results, which show that the center frequencies of the two passbands are 2.4 GHz and 5.2 GHz; and the passband insertion losses are 0.85 dB and 1.6 dB; and the relative bandwidths are 14.6% and 5.7%, respectively. Besides, the structure is with six transmission zeros, and 20 dB suppression for the third harmonic and the fourth harmonic are achieved. Compared with the traditional SIR double‐passband filter, this filter has many advantages, such as simple design, small size, small insertion loss, controllable frequency, high selectivity, and high spurious suppression.     

Application of polynomial design of multiplexers to the implementation of a manifold microstrip triplexer

This article presents a microstrip implementation of a manifold multiplexer. The design procedure is based on evaluation, through an efficient synthesis algorithm recently proposed, of the characteristic polynomials of the triplexer, including the channel filters. Both the manifold and channel filters parameters are also available at the end of the synthesis. This approach, based on polynomial modeling of the triplexer, has been experimentally validated for the first time through a practical implementation in planar technology. The fabricated prototype consists of three channel filters of third order centered at 1.84, 1.95, and 2.14 GHz, with bandwidth of 75, 60, and 60 MHz respectively. This work illustrates in detail the design and implementation of the practical triplexer, starting from the initial specifications and obtaining the final physical dimensions of the structure. Following the technique here shown, each filter is synthesized taking into account for the loading effects of the whole manifold; the filters dimensioning can be carried out with the filters separated from the multiplexer. In this way the optimization tasks are greatly simplified as compared with previous techniques for multiplexer design. The measured results of a manufactured prototype show return losses under 17 dB and minimum isolation between channels equal to 25 dB. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23:690–698, 2013.