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This brief presents a three-stage wideband power amplifier (PA) monolithic microwave integrated circuit (MMIC) using 100 nm GaN-on-Si process. A synthesized matching strategy is introduced to achieve high efficiency and improve gain flatness over a wide operation bandwidth. For demonstration, one monolithic microwave integrated circuit (MMIC) PA working from 24 to 29 GHz is designed, which covers the typical 5G millimeter-wave (mm-wave) bands. The measured output power reaches 30 dBm and the measured power added efficiency (PAE) exceeds 27.6% over the frequency range of 24 to 29 GHz. Meanwhile, the peak PAE of 40.6% and the peak power of 31.3 dBm are obtained at 27.5 GHz. Besides, the PA shows a measured gain of 18.7 to 21.2 dB from 25 to 30.5 GHz, with gain flatness of ±1.26dB. [ABSTRACT FROM AUTHOR]

A novel coupling-cancellation method by loading planar path is proposed and applied in the millimeter-wave phased array for wide-angle scanning. By employing the improved decoupling stubs with weak radiation first, an extra introduced wideband equal-magnitude and anti-phase path is generated to cancel the inherent coupling path. The principle of the proposed method is investigated by the equivalent circuits and the full-wave simulation. Based on this method, a high-isolation 1-D phased array using low-temperature-cofired ceramic (LTCC) process is designed and fabricated. The planar paths are placed symmetrically between the subarrays and its radiation polarization is coincident with the antenna elements, resulting in high isolation and enhanced boresight radiation null-fill of subarrays. The measured isolation is below 20 dB within the relative bandwidth of 16.7% and the maximum scanning angle is ±60°. Moreover, the proposed method can be expectedly extended to large-scale arrays. [ABSTRACT FROM AUTHOR]

This communication presents a millimeter-wave wideband dual-polarized low-temperature cofired ceramics (LTCC) antenna array based on metasurfaces (MSs) for beam-scanning applications. Benefiting from the wideband and large-freedom property of MS-based structures, a novel ±45° dual-polarized wideband MS-based antenna (MSA) element with high isolation is designed. The antenna element is fed by two orthogonal striplines on different layers, through a crosslike dog-bone slot and a narrow slot, respectively, to realize the two polarizations. The feeding structure consists of slot–stripline–slot–stripline from top to bottom and is specially designed to improve the polarization isolation of the antenna element. The proposed MSA element is compactly arranged with a small distance ($ < 0.5\lambda$) to construct a 4 $\times $ 4 array integrated in an LTCC package, where via walls with metal ring strips are loaded between adjacent elements to reduce the gain fluctuation. Consequently, the array can achieve a good beam-scanning capability over a wide band of 19.5% with a maximum scanning angle up to ±55° and a small gain variation of less than 3 dB. Meanwhile, the active $S$ parameters almost always remain below −10 dB, enabling good impedance matching when scanning at all angles. With these features, the proposed design has potential for application in 5G base-station systems. [ABSTRACT FROM AUTHOR]

In this brief, two wideband bandpass filters using a novel double-row staggered double-sided quasi-SSPPs transmission line are proposed. By loading U-shaped cells symmetrically, a transmission zero can be introduced into the original operating frequency band, which forms a high out-of-band suppression wideband bandpass filter. The structure can draw an analogy with double-sided parallel stripline, and the equivalent circuit model of microstrip line can be constructed to assist analysis and design. The passband selectivity can be further improved when the number of U-shaped cells is increased from 3 to 5. The measured result of 3-dB fractional bandwidth is 18.9 % (frequency 11.4 GHz), and the in-band return loss is greater than 10.2 dB. In addition, the out-of-band suppression is greater than 20 dB in the lower stopband (from 6.18 GHz to 10.12 GHz) and the upper stopband (from 12.78 GHz to 19 GHz). [ABSTRACT FROM AUTHOR]

A novel low-profile wideband dual-circularly polarized metasurface antenna based on a traveling-wave sequential feeding mechanism is proposed. It consists of 4 × 4 rectangle metasurface cells and is excited by a simple two-port traveling-wave feeding network, which includes four rotated Z-shaped slots etched on the ground and a ring feeding line, to provide stable sequential phases of 0°, 90°, 180°, 270° for realizing dual-circular polarizations. By changing the width of four Z-shaped slots, the equal amplitude of two orthogonal electric fields can be achieved and good right- and left-handed circular polarization (RHCP, LHCP) can be realized accordingly in a wideband. Moreover, a metasurface is utilized as a radiator to improve the impedance bandwidth (IMBW) as well as radiation performance. For demonstration, one prototype with an overall size of 0.88λ0 × 0.88λ0 × 0.06λ0 centered at 5.3 GHz is fabricated and measured. The measured results show that the proposed low-profile antenna realizes a large 10-dB IMBW of 38.4% (4.33–6.39 GHz) and 46.6% (6.17–6.70 GHz), 3-dB axial-ratio bandwidth of 38.4% and 39.3%, respectively, for RHCP and LHCP states. In addition, the polarization isolation is over 12 dB in the entire band of interest. [ABSTRACT FROM AUTHOR]

A broadband low-profile folded transmitarray (FTA) is proposed and investigated, in which a novel wideband transmission polarizer (TP) is used to realize low-profile design. The proposed TP, mainly consisting of a differential-fed grid-slotted patch antenna, can realize high-efficiency transmission and polarization selection simultaneously within a wideband frequency range. Moreover, the proposed TP can realize linear transmission phase because of the true-time delay (TTD) technique. Owing to the function of polarization selection and linear transmission phase, the TP can be used as antenna element for a FTA. A 140-element FTA is designed and fabricated by combining the TP with a broadband polarization rotation reflecting surface (PRRS). The measured radiation patterns agree well with the simulated results, and a peak gain of 24 dBi and maximum aperture efficiency of 44.7% are achieved. Furthermore, −1 and −3 dB gain bandwidth with 25.9% and 33.3% are also experimentally demonstrated in the proposed FTA, respectively. [ABSTRACT FROM AUTHOR]

One kind of cross-layer capacitive-loaded metasurface (MS) structure is proposed and applied to realize miniaturized wideband MS antennas. The proposed MS structure is constructed by loading a thin substrate with several stacked patches above conventional MS structure, where the cross-layer stacked patches are located upon the gaps between the original MS units. Therefore, additional capacitances can be introduced accordingly, and then help decrease the resonance frequency effectively. Based on above strategies, when the resonance frequency remains unchanged, the proposed MS structure with smaller aperture size can provide equivalent capacitive reactance and inductive reactance with conventional MS structure. In this way, the miniaturization can be realized while the wideband feature is still remained. By optimizing the loading structure, symmetrical and asymmetrical MS structures are designed accordingly and different-level miniaturizations are realized, where the element sizes can be respectively miniaturized to 0.067 λ0 × 0.067 λ0 and 0.059 λ0 × 0.059 λ0. For demonstration, onw asymmetrical capacitive-loaded MS structure is used to realize a compact wideband MS antenna, where large impedance bandwidth (∼44.4%) and compact size (∼0.41 λ0 × 0.41 λ0) are obtained. This design method may provide a feasible solution to realize compact wideband MS antennas for broadband wireless communication systems. [ABSTRACT FROM AUTHOR]

A wideband low-noise amplifier (LNA) with low and flat noise figure (NF) is presented in this article. For conventional wideband noise matching, the noise performance in the high-frequency region of the entire wideband is usually deteriorated due to the frequency-dependent nature of the minimum noise figure (NFmin) for a MOSFET. To address this issue, a novel wideband noise matching approach aiming at noise matching in high band is proposed. This approach can reduce the NF in high band at the cost of a slight NF increase in low band, eventually achieving a low and flat NF and thus a better overall noise performance for a wideband LNA. In addition, the multistage noise matching technique is employed at high frequencies to further reduce the NF caused by the second amplification stage. To validate the proposed techniques, a two-stage LNA prototype was designed and fabricated using a 65 nm CMOS process. The experimental results indicate a peak gain of 16.6 dB with a −3 dB bandwidth (BW) from 7.2 to 27.3 GHz (a fractional BW of 116%). Within the entire band of interest, the simulated NF is low and almost constant (3.3–3.4 dB), while the measured NF falls within the range of 3.30–3.72 dB. Considering the uncertainty of NF measurement, a 0.21 dB NF flatness is one of the best results among the reported millimeter-wave wideband LNAs. The measured third-order input intercept point (IIP3) is −6 dBm at 20 GHz, while the power consumption is 13.2 mW. In addition, only two passive transformers are used in this design, leading to a compact chip core area (0.14 mm2). [ABSTRACT FROM AUTHOR]

This brief presents a 15–38 GHz vector-summing phase shifter (VSPS) with the full 360° phase-shifting range in the 65nm CMOS process. An improved wideband quadrature all-pass filter (QAF) is designed to overcome the traditional one’s capacitive loading effect and exhibits wideband I/Q performance. Analysis and comparison between the proposed QAF and the traditional one are discussed. For demonstration, a prototype VSPS with the full 360° phase-shifting range from 15GHz to 38GHz using the proposed QAF is implemented in the 65nm CMOS process. The root means square (RMS) phase and gain errors are 2°~3.5° and 0.7 dB ~1 dB from 15 GHz to 38 GHz, respectively. The power consumption is 19.2mW, and the whole chip is compact with a core size of 0.16mm2. [ABSTRACT FROM AUTHOR]

A wideband low-noise amplifier (LNA) featuring transformer-based wideband input matching is proposed for millimeter-wave applications. By analyzing the properties of conventional series input matching networks, which were widely employed in narrowband LNAs and shunt–series matching networks for bandwidth extension, a novel input matching network possessing the merits of both was proposed. For further bandwidth extension, another peak of input impedance at a higher frequency is introduced for the proposed input matching network. Moreover, it is proved that the proposed input matching network can suppress the gate resistor noise, resulting in significant noise figure (NF) improvement of an LNA. On the other hand, the NF is further reduced by connecting a transformer between the two amplification stages, which helps suppress the noise contribution from the second stage, leading to an LNA design with NF lower than 4.5 dB over a very wide operating bandwidth. To enhance the gain bandwidth, the peak distribution, including both shunt peaking and series peaking, is discussed. By appropriately distributing these peaks, which is also known as the pole-tuning technique, a wider gain bandwidth can be obtained. To validate the proposed techniques, an LNA with two common-source (CS) stages is designed and fabricated using a 65-nm CMOS process, and the overall chip size, including all pads, is only 0.26 mm2. The two CS stages are cascoded for dc biasing to reduce the power consumption. Experimental results show that a peak gain of 13.5 dB is achieved within a −3-dB bandwidth from 19.2 to 42.6 GHz. The measured NF is 3.1–4.5 dB, and the input 1-dB gain compression point (IP1 dB) ranges from −13.54 to −9.89 dBm in the entire gain bandwidth. The input return loss $S_{11}$ is less than −10 dB over a frequency range of 16.8–38.9 GHz. Moreover, benefiting from the current-reuse technique, the power consumption of the LNA is only 6.36 mW. [ABSTRACT FROM AUTHOR]

One kind of interembedded metasurface (MS) structure is proposed and applied to realize miniaturized wideband MS antennas (MSA). Different from conventional MSA, the proposed interembedded MSs are formed by etching slots on the radiating patch with various sawtooth schemes rather than rectangular gaps. Consequently, the resonance frequency of MSA can be decreased due to introducing those interdigital-like capacitances, while obvious miniaturization can be realized accordingly. By optimizing the parameters of the sawtooth radiating slots, a miniaturized antenna using cross-shaped interembedded MS is proposed, achieving an impedance bandwidth of 35.08% and a high gain of about 8.25 dBi with a compact overall size of 0.66 λ0 × 0.66 λ0. Moreover, one further miniaturized antenna using modified cross-shaped interembedded MS is also presented, realizing a larger impedance bandwidth of 41.35% and a high gain of about 6.62 dBi with a smaller aperture of 0.48 λ0 × 0.48 λ0. Compared with conventional MSA, 42% overall size reduction and larger bandwidth can be obtained. The design approach may provide a feasible solution to realize compact MSAs with the unique advantages of large bandwidth, low profile, low cost, and easy fabrication. Due to above good features, the proposed antenna can be a promising candidate for applications in modern wideband wireless communication systems. [ABSTRACT FROM AUTHOR]

A wideband planar dipole array based on artificial magnetic conductor (AMC) surface is presented for phased array applications. One wideband in-phase hexagonal AMC cell is realized firstly. An X-band planar dipole is modified by employing a detached H-shaped patch and four L-shaped stubs for impedance bandwidth enhancement. The active VSWR with different scanning angles and the radiation pattern of center element in small array are simulated. For demonstration, a prototype of 45° linearly polarized array with the elements of $4\times32$ is fabricated and measured. From the measurements, it can provide a stable gain over the entire scan range of ±45° within 8–11 GHz. Meanwhile, the difference of two orthogonal polarization components keeps less than 3.5 dB below 11 GHz as the beam scanning. It shows good performance in low-profile and low cost phased array antennas. [ABSTRACT FROM AUTHOR]

A compact low-profile ultrawideband circularly polarized (CP) metasurface antenna (MSA) array is presented in this letter. The array consists of 2 × 2 sequentially rotated symmetric MSA elements and a wideband four-way feeding network providing stable phases of 0°, 90°, 180°, and 270°. By using the constructed feeding network and MSA element, the CP array can achieve an ultrawideband CP performance with a low profile of 0.05λL. The measured results show that the proposed MSA array achieves the 10 dB impedance bandwidth of 97.2%, 3 dB axial ratio bandwidth of 83.2%, and 3 dB gain variation bandwidth of 73.8%. Compared with the other designs in published literatures, the proposed CP MSA array owns the advantages of low profile with a simple structure and good CP performance without any air gap, thus indicating a promising candidate in compact wideband wireless systems. [ABSTRACT FROM AUTHOR]

A novel wideband polarization rotating element based on a metasurface antenna is proposed. To achieve high polarization isolation and low cross polarization, a wideband differential-driven dual-polarized metasurface antenna is designed accordingly. By connecting the two differential ports of the dual-polarized metasurface antenna, a wideband polarization rotating metasurface element (PRMSE) is realized, while a large polarization rotating bandwidth of 27.6% can be achieved. In addition, combining the true-time delay (TTD) microstrip lines, the PRMSE can achieve linear phase response and can be applied to the folded reflectarray design. Based on the PRMSE, a 140-element center-fed folded reflectarray (FRA) is designed and fabricated. The measured radiation patterns of the FRA are stable within the frequency range from 26 to 32 GHz. The measured −10 dB impedance bandwidth is 25.4% from 25.4 to 32.8 GHz. Furthermore, the measured 1 dB gain drop and 3 dB gain drop are 20.7% and 34.5%, respectively. The measured sidelobe levels are below −13 dB and the cross-polarization levels are below −30 dB at the broadside direction within the entire operating band. [ABSTRACT FROM AUTHOR]

In this article, various types of six-port balanced rat-race couplers with wideband common-mode suppression characteristics are presented. In these couplers, the input and output ports can functionalize either as single-ended or differential terminals to realize different operational modes. The power-splitting ratio for these balanced couplers can be flexibly adjusted by means of the values of the characteristic-impedance parameters of their constituent transmission-line segments. Furthermore, the employment of double-sided-parallel-strip-line-(DSPSL)-based 180° phase inverters instead of half-wavelength transmission-line-based ones allows for the considerable enlargement of their operation bandwidth in more-compact circuits with lower in-band insertion-loss levels. For experimental-validation purposes, two microstrip prototypes at $f_{0}=0.9$ GHz with equal and unequal power division are fabricated and characterized. They exhibit common-mode rejection levels higher than 15 dB from 0 to 1.8 GHz (i.e., 0– $2f_{0}$) and differential-to-common- mode-conversion suppression levels above 15 dB within the spectral range 0–1.49 GHz (i.e., 0– $1.65f_{0}$). [ABSTRACT FROM AUTHOR]

A simple, compact filtering patch antenna with wide out-of-band suppression is presented, where the filtering mechanism is first analyzed and implemented based on mode analysis of a conventional patch antenna. According to the mode analysis, undesired higher-order modes can be effectively suppressed by selecting a proper length ratio of two sides of the patch and the feeding position, thus realizing a wide upper stopband. To further enhance the filtering response, another two simple filtering structures loaded on the patch antenna are also proposed. First, a split-ring-shaped slot is etched on the patch to generate a radiation null at the lower-band edge for improving skirt selectivity. Second, a U-shaped strip is etched underneath the patch and connected with the feeding probe, which can introduce another null at the upper band edge. As a result, a high suppression level of 23 dB in lower and upper stopbands can be realized, respectively, for the proposed filtering antenna, while the upper stopband can extend up to $2.3 f_{0}(f_{0}$ is the center frequency of the antenna). Furthermore, wide passband response can also be achieved by the extra in-band resonances existing in the slot and the strip. A filtering antenna prototype is fabricated and measured for demonstration. Good agreements between the simulated and the measured results are observed, indicating a large impedance bandwidth of 22.6%, high antenna efficiency of 95.6%, and an average gain of about 7.4 dBi. Compared with the reported filtering antennas, the proposed filtering antenna can achieve better wideband filtering response but with a simpler configuration. [ABSTRACT FROM AUTHOR]

A multiresonance antenna based on a nonperiodic square-ring metasurface (MS) is proposed, which has large bandwidth and stable radiation gain. The nonperiodic MS radiator is formed by several adjustable square-ring patches and fed by a microstrip line through a coupling slot. By properly adjusting the widths of these square rings, different resonance modes can be inspired for the MS according to the characteristic mode analysis. Combined with the resonance mode of the coupling slot, multiple adjacent resonance frequencies occur and thus realize a wideband and consistent radiation. For demonstration, a C-band wideband antenna based on the proposed 4 × 4 square-ring MS units with a low profile of 0.06λ0 is accordingly designed and fabricated. The measured results indicate a large impedance bandwidth of 54% (4–7 GHz) and an extremely stable gain with 2 dB gain bandwidth of 32% (4.76–6.54 GHz). [ABSTRACT FROM AUTHOR]

A wideband and high-efficiency power amplifier (PA) based on a bandpass filtering (BPF) matching network is presented. Composite right-/left-handed (CRLH) cell and dual-CRLH (D-CRLH) cell are employed to realize the wideband BPF matching network with an absorbed bias circuit. The equivalent circuit model of the proposed BPF matching network is given and a synthesized design method is introduced. Furthermore, one wideband gallium nitride (GaN) PA with high efficiency is achieved by using the proposed BPF matching network accordingly. The measured S-parameters of the wideband PA reveal bandpass response from 1.2 to 2.3 GHz with ±1.2-dB gain flatness and one transmission zero (TZ). For large signal performance from 1.25 to 2.4 GHz, the experimental results show that the measured drain efficiency (DE) is between 64.3% and 77.5%, and verifying the validity of the design strategies for the proposed wideband high-efficiency PA. Due to the compact feature of the CRLH and D-CRLH (D/CRLH) matching network, the proposed PA achieves the smallest area in terms of core circuit compared with other published works. The results demonstrate the advantages of the D/CRLH BPF structure for designing wideband high-efficiency PAs. [ABSTRACT FROM AUTHOR]

A novel filtering method based on the metasurface antenna (MSA) with radiation nulls is proposed without loading extra circuits. Due to the specific multiunit structure of MSA, the filtering method is first realized on each radiating metasurface (MS) unit by introducing a multifolded U-shaped slot and a defected ground structure to generate lower edge radiation nulls. Meanwhile, coplanar parasitic patches are loaded around the MS units to provide upper edge nulls and simultaneously introduce extra in-band resonances for wide passband. Thus, a low-profile, wideband, and high-gain filtering antenna is readily constructed. To verify the concept, a prototype with a low profile of only $0.04\lambda _{{0}}$ is designed and fabricated. The simulated and measured results agree well, demonstrating a good performance with large impedance bandwidth of about 20%, high average gain of 8 dBi, and high aperture efficiency of about 90%, together with high out-of-band suppression levels of about 20 dB. In addition, the radiation patterns are symmetric in both the E- and H-planes with cross-polarization suppressions of over 20 dB. Compared with the reported filtering antennas, the proposed filtering MSA can achieve the wideband filtering response in a low profile, as well as high gain with high aperture efficiency. [ABSTRACT FROM AUTHOR]

Four novel architectures of wideband five-port single-ended-to-balanced power dividers with broadband common-mode suppression are proposed in this paper. The bandpass filtering capability with/without close-to-passband transmission zeros are also incorporated in some of them to obtain multifunctional single-ended-to-differential-mode filtering/power division operation. Two ideal 180° phase inverters are used to replace the conventional half-wavelength transmission line-based inverters in the basic power divider structure so that wideband common-mode rejection and a smaller circuit size are achieved. Quarter-wavelength transmission lines and coupled-line sections are exploited to simultaneously realize the bandpass filtering and wideband power division functionalities. Each five-port power divider exhibits broadband 3-dB single-ended-to-balanced power division, high in-band input–output power-matching levels, high in-band power isolation levels between the two balanced outputs and wideband common-mode rejection. The theoretical analysis, parametric study, and design procedure for the conceived single-ended-to-differential-mode power dividers are provided. Furthermore, for experimental and demonstration purposes, four microstrip prototypes designed at 1 GHz are manufactured and characterized. [ABSTRACT FROM AUTHOR]

In this paper, a novel wideband and low-profile discrete dielectric lens (DDL) antenna is presented. The proposed unit cells of DDL with the square-pyramid structure can realize wideband antireflection at an air–dielectric interface. By increasing the phase compensation range, the DDL antenna with very large gain bandwidth but large DDL thickness would be achieved. Furthermore, based on the large gain bandwidth technology, a novel multifolded lens structure is proposed to realize the low-profile design, in which a broadband polarization rotation reflection surface is proposed, while a polarized grid is used appropriately. Finally, the proposed multifolded DDL antenna can achieve a very large gain bandwidth, while the thicknesses of the DDL unit cell and the total antenna can be greatly reduced. For demonstration, the proposed multifolded DDL antenna is fabricated and measured. The fabrication was implemented by using a simple and low-cost 3-D printing technology. The results show that the proposed lens antenna can realize a 1 dB gain drop bandwidth of 43%, thickness of less than 1/3 focal-length-to-diameter ratio, and maximum aperture efficiency of 32%. Good agreement can be observed between the measurement and simulation. [ABSTRACT FROM AUTHOR]

A novel wideband reconfigurable impedance matching network is presented, which consists of a main transmission line and several switchable branch lines. The proposed network can match different complex loads at different frequency bands. A novel optimization method is proposed to calculate the circuit parameters efficiently. The calculation results indicate that the proposed impedance matching network can match a broad range of complex loads with wideband operation. For demonstration, two prototypes are designed and fabricated. Good agreement is observed between the measured and expected performances. [ABSTRACT FROM AUTHOR]

Two novel high selectivity wideband balanced filters based on open/shorted stubs with multiple transmission zeros are proposed in this brief. Two and four transmission zeros near each passband for the differential mode (DM) can be easily achieved for two balanced filters. In addition, the common mode can be suppressed with three and five transmission zeros with an insertion loss greater than 15 dB/20 dB over a wide frequency band. Two prototypes with 3-dB fractional bandwidths of 67.6% and 37.8% for the DM with an insertion loss greater than 15 dB (7.0–12.7 GHz) are designed and fabricated. A good agreement can be observed between the measured results and the theoretical expectations. [ABSTRACT FROM PUBLISHER]

Two compact low-temperature co-fired ceramic (LTCC) wideband bandpass filters using coupled lines with open/shorted stubs are proposed in this paper. Two conventional coupled lines with open/shorted stubs are used to increase the passband order for the wideband filters. Two independent transmission zeros realized by the open/shorted coupled lines are used to further improve the passband selectivity and harmonic suppression. Due to the 3-D LTCC circuit, the coupled lines and stubs can be located at different layers to overcome the large circuit size. Two fifth-order wideband LTCC bandpass filters centered at 3.1 GHz with multiple transmission zeros are designed and fabricated for verification. The theoretical and measured results are in good agreement and show good in-band performances. [ABSTRACT FROM AUTHOR]

Three novel wideband balanced-to-unbalanced filtering power dividers based on coupled lines are proposed in this paper. Multifunctional power dividers can replace various cascaded single devices to decrease integration mismatching loss and circuit size. The wideband response can be easily realized by the coupled lines structures. To further improve the differential-mode passband selectivity, open/shorted coupled lines and half-wavelength open stubs are applied to introduce two transmission zeros near the passband, respectively. In addition, a resistor in the middle of two single-ended ports can be used to realize isolation between out ports. To verify the proposed concepts, three prototypes of wideband balanced-to-unbalanced filtering power dividers operating at 2 GHz are designed and fabricated with the 4-dB differential-mode bandwidths of 80.5%, 71.5%, and 80%. All the structures show good performances for differential-mode out-of-band suppression, common-mode suppression, and isolation. [ABSTRACT FROM PUBLISHER]

A new wideband balanced power dividing/combining network with high isolation is proposed in this paper. The differential/common mode equivalent circuits of the balanced network can be easily reduced based on the matrix transformation. Two double-sided parallel-strip line (DSPSL) 180^\circ phase inverters loaded with four isolation resistors are used to realize high isolation for the power division output ports. A planar wideband balanced network with bandwidth 52.7% of (1.68–2.84 GHz, \vert Sdd21, Sdd31\vert >- 4 dB) for the differential mode and high isolation for the differential/common mode is designed and fabricated. The measured results show good agreement with the theoretical expectations. [ABSTRACT FROM PUBLISHER]

A new frequency-agile scheme for the loaded stepped-impedance resonator (SIR) is introduced, which can be employed for designing a wideband tunable bandpass filter (BPF). Two identical capacitors are added to the two open ends, and a capacitor is added to the center of the SIR. By properly controlling their respective values, the even-mode resonant frequency (f_\mathrmeven) can be bidirectionally tuned, resulting in a wideband tuning range (approximately double those of the traditional tunable resonators). However, in such frequency range, the odd-mode resonant frequency (f_\mathrmodd) functions as a spurious resonance would appear. To overcome this, the feed line is attached to the center of the SIR where it is always short-circuited for f_\mathrmodd and its odd-order harmonics, which cannot be excited accordingly. Thus, the wideband tuning range of the passband (f_\mathrmeven) in the proposed BPF is validated to be meaningful, and the selectivity of the passband is improved due to the suppression of odd-mode spurious near the passband. For demonstration, a wideband tunable BPF is designed, and the simulated and measured results are presented, showing good agreement. The results showcase that the tuning range of passband reaches 84.4%, i.e., from 0.77 to 1.42 GHz with insertion loss from 3.1 to 1 dB. [ABSTRACT FROM PUBLISHER]

A novel wideband balanced-to-unbalanced power divider using symmetrical transmission lines is proposed. Due to the symmetry of the power divider circuit, even/odd-mode analysis method is applied to derive the even/odd-mode values and transmission line characteristic impedance. A resistor in the middle of two single-ended output ports is used to realize high isolation for the power division ports. One prototype of the wideband balanced-to-unbalanced power divider operating at 2.2 GHz (1.24–3.20 GHz) is designed and measured to prove the proposed methods. [ABSTRACT FROM PUBLISHER]

Two novel high-selectivity wideband balanced filters using symmetrical/asymmetrical coupled lines with open/shorted stubs are proposed in this letter. Multiple transmission zeros are achieved to obtain sharp rejection and good out-of-band suppression for the differential mode, in which fixed transmission zeros can be realized by half-wavelength open stubs and adjustable transmission zeros can be realized by loaded open/shorted coupled lines. In addition, all the transmission zeros can be allocated to suppress the common mode from 0 GHz to 3f0 ( f0 is the center frequency of the passband). Two balanced filters with 3-dB fractional bandwidths of 22% and 21% are, respectively, designed and fabricated. [ABSTRACT FROM PUBLISHER]

A compact ultra-wideband (UWB) bandpass filter with improved upper stopband using open/shorted stubs is proposed in this letter. Seven transmission zeros in the upper stopband can be realized by different open/shorted stubs. The bandwidth of the UWB bandpass filter can be adjusted easily by changing the characteristic impedance of the open/shorted stubs. A UWB bandpass filter with 3-dB fractional bandwidth of 123% (0.5-1.9 GHz) is fabricated and measured. Good agreement can be observed between simulated and measured performances. [ABSTRACT FROM PUBLISHER]

Two new wideband in-phase and out-of-phase balanced power dividing/combining networks are proposed in this paper. Based on matrix transformation, the differential-mode and common-mode equivalent circuits of the two wideband in-phase and out-of-phase networks can be easily deduced. A patterned ground-plane technique is used to realize the strong coupling of the shorted coupled lines for the differential mode. Two planar wideband in-phase and out-of-phase balanced networks with bandwidths of 55.3% and 64.4% (\vert S{ dd21,31}\vert<4\ {\ {dB}}) for the differential mode with wideband common-mode suppression are designed and fabricated. The theoretical and measured results agree well with each other and show good in-band performances. [ABSTRACT FROM PUBLISHER]

As one of the most important components in RF/microwave systems, high-performance wideband bandpass filters with low insertion loss within the passband and large attenuation in the stopband are extremely desirable [1], [2]. Moreover, as shown in Figure 1(a), the definition of the fractional bandwidth for the narrowband bandpass filter is less than 1%; and the fractional bandwidths for wideband/ultrawideband (UWB) bandpass filter are greater than 1% and 25%, respectively [2]. The main features of the high-performance wideband microstrip bandpass filters include simple design, compact size, low loss and good linearity, enhanced out-of-band rejection, and easy integration with other circuits/antennas etc. [3], [4]. Various microstrip wideband filters employing multimode resonators, complementary split-ring resonator (CSRR) and multilayer aperture-coupled patches have been designed and analyzed [3]-[10]. In [11]-[18], the cascaded low-pass/high-pass filters, electromagnetic (EM) loaded bandgap and T/Y-shaped resonators are used to extend the upper stopband bandwidth and improve the selectivity of the passband. [ABSTRACT FROM PUBLISHER]

Two novel wideband differential bandpass filters based on a T-shaped structure are proposed in this paper. Broad passband and wideband harmonic suppression for the differential/common mode can be easily achieved for the wideband differential filter without cross coupling, due to the controlled resonator frequencies of the shorted/open T-shaped structure. In addition, another more compact differential filter using cross coupling is proposed with two transmission zeros close to the passband to improve the selectivity for the differential mode. To verify the presented concept, two prototypes (\varepsilon r = 2.65, h = 0.5~\ mm) with 3-dB fractional bandwidth of 70% and 70.7% for the differential mode and insertion loss greater than 13.5 dB for common mode (0–19 GHz) are designed and fabricated. Good agreement can be observed between measured results and theoretical expectations. [ABSTRACT FROM AUTHOR]

A novel wideband balanced-to-balanced network with unequal power division is proposed in this letter. Two open stubs and half-wavelength transmission lines are used to realize wideband common mode suppression, two ideal double-sided parallel-strip line (DSPSL) 180 ^\circ phase inverters with isolation resistors are used to realize high isolation for the power dividing output ports. A planar wideband balanced network with bandwidth of 38.6% (power division ratio: 1:2^2) for the differential mode and over 113.6% common mode suppression (1.06–3.56 GHz, $| S_{{cc}21,31}| < -10\ \text{dB}$) is designed and fabricated. [ABSTRACT FROM PUBLISHER]

A new compact wideband differential bandpass filters with wideband common mode suppression using half-wavelength ring resonator is presented in this letter. Five-order passband for the wideband differential mode with two transmission zeros close to the passband is realized with four open stubs. A planar wideband differential filter (3 dB fractional bandwidth 79%) with wideband common mode suppression is designed and fabricated. The theoretical and measured results agree well and show good in-band filtering performances and high selectivity. [ABSTRACT FROM PUBLISHER]

A high selectivity wideband bandpass filter (BPF) based on transversal signal-interaction concepts and T-shaped structure is proposed in this letter. Two transmission paths with two open coupled lines and a T-shaped structure are used to realize signal transmission from Port 1 to Port 2. A three-order passband with two transmission zeros can be achieved in the proposed filter. One prototype with 3-dB fractional bandwidth of 36.3% (3.3–4.75 GHz) is fabricated for demonstration. Good agreement is observed between simulated and measured performances. [ABSTRACT FROM PUBLISHER]