Broadside Coupling Research Articles

Broadside Coupling High-Temperature Superconducting Dual-Band Bandpass Filter

This paper proposes a novel high-temperature superconducting dual-band bandpass filter (HTS-DBPF), that employs a broadside coupling structure, in which quarter-wavelength resonators are formed on opposite sides of each substrate. This structure provides a dual-band operation of the BPF and flexibility, in the sense of having a wide range in selecting two center passband frequencies of the HTS-DBPF. This paper employs the ratio of the lower and higher center passband frequencies, α, as a criterion for evaluating the flexibility. The obtained α ranges are from 1 to 4.7, which are the widest for DBPFs for mobile communications applications, to the best knowledge of the authors. This paper presents a 2.4-/2.9-GHz band HTS-DBPF, as an experimental example, using a YBCO film deposited on an MgO substrate. The measured frequency responses of the HTS-DBPF agree with the electromagnetic simulated results. Measurement and simulation results confirm that the proposed filter architecture is effective in configuring a DBPF that can set each center passband frequency widely.

Compact dual-band bandpass patch filter using coplanar waveguide feed method

By employing the coplanar waveguide feeding method, a dual-band dual-mode bandpass patch filter, with flexible frequency ratio and fractional bandwidth, is proposed. Two resonant frequency bands are achieved by using two stacked square patches with different cross slots etched, which are simultaneously excited by the centre CPW fed lines. The frequency ratio and fractional bandwidths can be controlled by the CPW broadside coupling and cross slots. To verify the proposed configuration, two dual-band bandpass patch filters have been designed, fabricated and measured.

A novel butterfly‐shaped multilayer backward microstrip hybrid coupler for ultrawideband applications

AbstractIn this letter, the numerical analysis and design of aperture‐coupled backward microstrip hybrid coupler for ultrawideband (UWB) multilayer microwave circuits are introduced. The proposed coupler is composed of two microstrip patches located on two stacked substrate layers. This coupler uses a broadside coupling via a rectangular‐shaped slot in the common ground plane (mid‐layer). To achieve broadband characteristics for UWB operation, butterfly‐shaped patches are used. The numerically simulated results using two simulation programs with two different numerical techniques show that the proposed coupler have good insertion losses (both through S21 and coupled S31) variation (less than ±2 dB) and high return loss S11 (greater than 14 dB) with acceptable isolation S41 (about 14 dB) over most of the 3.1–10.6‐GHz frequency band. A 3dB/90°‐backward hybrid coupler prototype is fabricated and then tested experimentally using Agilent E8364B PNA Network Analyzer. Experimental results agree well with the simulated ones. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2231–2237, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27092

Simulation and Experiment of a Compact Wideband 90$^{\circ}$ Differential Phase Shifter

A compact wideband 90° differential phase shifter is developed by modifying ports termination in the Abbosh phase-shifter configuration. This novel phase-shifter arrangement consists of a 3-dB directional coupler with the coupled and transmission ports terminated with reactive loads. The proper reactance is found at the input of the coupled line section in which the remaining ports are open circuited. Both coupled sections utilize a multilayer broadside coupling microstrip-slot-microstrip tight coupler. A theoretical model is presented to explain the performance of the proposed phase shifter and design procedure. Further, the phase shifter was designed and manufactured. Results of calculation and measurement show that the developed circuit provides a 90° differential phase shift with deviation less than ±4° across the 3-7-GHz frequency band.

Design of compact inphase power divider with one narrow notch band for UWB application

A novel multilayer inphase power divider with ultra-wideband behaviour and a sharply rejected notch band is presented. The proposed power divider employed a broadside coupling structure via a multilayer slot configuration and a single isolation resistor. One notch band is obtained by introducing one coupled folded stepped impedance resonator with metalised via hole to ground. Simulated and measured results show that the proposed power divider has equal power division with high stability of phase, low insertion loss and good return loss at the three ports across the band 2.7 to more than 11.0 GHz.

A 20-31 GHz HIGH IMAGE REJECTION RATIO SUBHARMONIC MIXER

A broadband monolithic image rejection subharmonic mixer using a standard 0.18m CMOS technology is proposed. This circuit is composed of a band-pass fllter with an intermediate frequency (IF) extraction function that can simplify the block diagram of the image rejection mixer. The entire passive circuit is constructed using a broadside coupling structure to achieve a high level of integration. Based on measured results, the proposed mixer exhibits conversion loss of 15.5{18.5dB at a local oscillator (LO) power of 13dBm, whereas the 3dB bandwidth ranges from 20 to 31GHz (43.1%) with a miniature chip dimension of 0:77 £ 0:81mm 2 . The LO-to-radio frequency (RF), 2LO-to-RF, and RF-to-IF isolation levels are higher than 22.5, 42.9, and 34.5dB, respectively. The best image rejection ratio of 29dBc with 20 - phase compensation at 24.5GHz can be achieved.

Parallel-Planar High-Temperature Superconducting Dual-Band Bandpass Filter Using Double-Sided Conductors on a Substrate

This paper proposes a broadside coupling high-temperature superconducting (HTS) dual-band bandpass filter (DBPF) employing double-sided conductors on a substrate to suppress misalignment between resonators. This filter configuration satisfies the required specifications and provides flexibility in selecting each center frequency for the two passbands within certain ranges of frequencies. This paper presents 1.8-/2.9-GHz band and 2.1-/2.7-GHz band HTS bandpass filters, as experimental examples, to validate the proposed filter configuration. The measured frequency responses of the fabricated HTS-DBPFs are closer to the simulated ones than those of the previously proposed HTS-DBPF.

High selectivity UWB bandpass filter using dual-mode resonators

A novel ultra-wideband bandpass filter using multilayer technology is reported. A dual-mode resonator is designed on the middle layer to generate a transmission zero at the upper stopband, and a short-circuited coupling line is designed on the top layer for generating a transmission zero at the lower stopband. These incorporated transmission zeros result in high selectivity for the proposed filter. The broadside coupling technique is adopted for the strong coupling to realise an ultra-wide passband. The proposed filter has been investigated using full-wave simulation and fabricated using multilayer liquid crystal polymer technology. Good agreement between simulated and measured results is observed. The measured UWB filter has a 3 dB bandwidth from 3 to 9 GHz with a small in-band insertion loss, a flat group delay, high selectivity and a compact size of 4.8 by 11 mm.

A Compact Printed Filtering Antenna Using a Ground-Intruded Coupled Line Resonator

A compact printed filtering antenna with high band-edge gain selectivity is presented. Occupying about the same substrate area as a conventional antenna, the proposed structure not only serves as a radiator but also a second-order bandpass filter, with one filter pole provided by a Γ-shaped antenna and the other by a newly proposed coupled line resonator. High band-edge selectivity is achieved due to two additional stop-band transmission zeros provided by the coupled line resonator. To minimize the required area and reduce the spurious radiation, a coupled line structure composed of a microstrip line and a coplanar waveguide by broadside coupling is adopted and intruded into the Γ-shaped antenna area. According to the filter specifications, a design procedure for the proposed filtering antenna is depicted in detail. One example at 2.45 GHz with a second-order Chebyshev bandpass filter of 0.1 dB equal-ripple response is tackled. As compared to the conventional Γ -shaped antenna, the proposed filtering antenna not only possesses a similar antenna gain but also provides better band-edge gain selectivity and flat passband gain response. The measured results, including the S-parameters, total radiated power, and antenna gains versus frequency, have good agreement with the designed ones.

Hybrid Microstrip T-Stub/Defected Ground Structure Cell for Electromagnetic Interference Bandpass Filter Design

In this paper, the hybrid microstrip T-stub/defected ground structure (HMT/DGS) cell is presented, which is composed of a microstrip T-stub and an interdigital DGS with the broadside-coupled (BC) transition. Finely adjusted resonance can be achieved by the proposed cell. Meanwhile, strong slow-wave effect is employed by the structure, which leads to wide stopband responses. Based on these HMT/DGS cells, the interdigital-coupled scheme is employed to implement the electromagnetic interference (EMI) bandpass filter with high performance. To verify the aforementioned mechanism, two filters are designed and fabricated. Specifically, the second-order bandpass filter with a fractional bandwidth (FBW) of 14.3% has a 29.1-dB stopband rejection up to 15 f0 (where f0 stands for the passband center frequency). The fourth-order bandpass filter with an FBW of 10.8% demonstrates a 30.1-dB stopband rejection up to 12.1f0. Both types of filters show compact sizes with low insertion losses less than 1.1 dB.

Detailed Analysis of Multilayer Broad-Side Coupler with a Symmetric Structure

A detailed analysis of a multilayer symmetric coupler employing symmetrical broad-side coupled lines is presented. We confirm that the coupler can be designed using a well-known even-odd mode analysis of two strip lines while the coupler has four strip lines. We also confirm that the previously reported poor isolation originates from port mismatching. To verify the analysis, couplers that have different dimensions are fabricated. One example exhibits a coupling loss of 4.5±0.5dB, a return loss better than 15dB, and isolation characteristics higher than 12dB in the 6.5 to 15.1GHz frequency range. These results agree well with the obtained simulation results. The results show that the coupler has the potential to provide tight and ideal coupling.

Quasi-Elliptic UWB Bandpass Filter Using Multilayer Liquid Crystal Polymer Technology

A novel ultra-wideband (UWB) bandpass filter (BPF) with quasi-elliptic response using non-uniform periodical structures is presented. In the design, a periodical unit structure is proposed and studied, which can provide transmission zeros at both lower and upper stopbands to improve the selectivity. The proposed periodical unit structure consists of broadside coupling patches, slotted ground and embedded quarter-wavelength resonator. It can be implemented using a multilayer structure with a compact size. A high selectivity UWB BPF with multiple transmission zeros can be designed by cascading a few proposed non-uniform periodical units. As a demonstration, a UWB BPF with five periodical units is developed by full-wave simulation. Multilayer liquid crystal polymer technology is used to implement the designed prototype. The predicted results are verified by the experiments, which show that the fabricated filter has an ultra wide fractional bandwidth, a wide stopband and a high selectivity with quasi-elliptic response. The proposed filter is attractive for UWB communication and radar systems.

MULTI-FUNCTION PATCH ELEMENT

Integration of multiple functions is for the flrst time achieved within a single patch circuit element. Firstly, out of phase equal power division and bandpass fllter characteristics are combined within a patch element. The novelty of the proposed structure is to use simple asymmetric cross slots in the patch element to achieve this integration. A simplifled equivalent circuit model to describe operation of this patch element is proposed. Coplanar waveguide/microstrip broadside coupling is then investigated to enhance the performance of the patch balun fllter and eliminate narrow coupling gaps and microstrip lines. Subsequently, transition between microstrip and coplanar waveguide is then added to the patch element by using certain electromagnetic coupling methods for higher level integration without introducing additional loss. Difierent patch elements operating at 2.4GHz are developed to validate the feasibility of the proposed structures. The circuits were designed, fabricated and measured. The measured results agree quite well with the simulation, exhibiting small amplitude and phase imbalance at the output ports throughout the desired passband, and good rejection levels elsewhere.

Compact UWB Filter With Double Notch-Bands Using Multilayer LCP Technology

A novel ultra wideband (UWB) bandpass filter with double notch-bands is presented in this paper. Multilayer schematic is adopted to achieve compact size. Stepped impedance resonators (SIRs), which can also suppress harmonic response, are designed on top and second layers, respectively, and broadside coupling technique is used to achieve tight couplings for a wide passband. Folded SIRs that can provide desired notch-bands are designed on the third layer and coupled underneath the second layer SIRs. The designed prototype is fabricated using multilayer liquid crystal polymer (LCP) technology. Good agreement between simulated and measured response is observed. The fabricated filter has dual notch-bands with center frequencies of 6.4/8.0 GHz with 3 dB bandwidths of 9.5%/13.4% and high rejection levels up to 26.4 dB and 43.7 dB at 6.4/8.0 GHz are observed, respectively. It also has low-insertion losses and flat group delay in passbands, and excellent stopband rejection level higher than 30.0 dB from 11.4 GHz to 18.0 GHz.

Miniaturised broadside coupler using coupled slow-wave artificial lines

A miniaturised broadside coupled-line coupler is presented. The coupler is fabricated on a six-layered printed circuit board and consists of a 90° coupled slow-wave artificial transmission line section. Compared with previous works on printed circuit boards, the proposed design features the smallest occupied size. It also demonstrates a comparable operating bandwidth of 85%. The design concept, methodology and results are investigated.

Broadside excitation of surface plasmon waveguides on Cytop

Long-range surface plasmon waveguides consisting of a Au stripe on Cytop, covered with an index-matched aqueous solution, are described and characterized. The waveguides are tested using a broadside coupling technique, whereby tapered single-mode fibers are positioned in direct contact with the stripe such that the slow mode of the fiber couples through partial modal overlap to the long-range surface plasmon. Attenuation measurements obtained at λ0=1310 nm agree well with theory, thus validating the waveguide fabrication and experimental techniques. The waveguides are useful for (bio)chemical sensing and the broadside coupling technique is useful for on-wafer optical probing.

A Millimeter-Wave System-on-Package Technology Using a Thin-Film Substrate With a Flip-Chip Interconnection

In this paper, a system-on-package (SOP) technology using a thin-film substrate with a flip-chip interconnection has been developed for compact and high-performance millimeter-wave (mm-wave) modules. The thin-film substrate consists of Si-bumps, ground-bumps, and multilayer benzocyclobutene (BCB) films on a lossy silicon substrate. The lossy silicon substrate is not only a base plate of the thin-film substrate, but also suppresses the parasitic substrate mode excited in the thin-film substrate. Suppression of the substrate mode was verified with measurement results. The multilayer BCB films and the ground-bumps provide the thin-film substrate with high-performance integrated passives for the SOP capability. A broadband port terminator and a V-band broad-side coupler based on thin-film microstrip (TFMS) circuits were fabricated and characterized as mm-wave integrated passives. The Si-bumps dissipate the heat generated during the operation of flipped chips as well as provide mechanical support. The power dissipation capability of the Si-bumps was confirmed with an analysis of DC-IV characteristics of GaAs pseudomorphic high electron-mobility transistors (PHEMTs) and radio-frequency performances of a V-band power amplifier (PA). In addition, the flip-chip transition between a TFMS line on the thin-film substrate and a coplanar waveguide (CPW) line on a flipped chip was optimized with a compensation network, which consists of a high-impedance and low-impedance TFMS line and a removed ground technique. As an implementation example of the mm-wave SOP technology, a V-band power combining module (PCM) was developed on the thin-film substrate with the flip-chip interconnection. The V-band PCM incorporating two PAs with broadside couplers showed a combining efficiency higher than 78%.

Ultra wideband inphase power divider for multilayer technology

A multilayer inphase power divider with an ultra wideband behaviour is presented. The proposed divider exploits broadside coupling via a multilayer microstrip/slot configuration. The design method utilised for the device is based on the conformal mapping techniques. The developed device has a compact size with an overall dimension of 20 mm times 30 mm. The simulated and measured results show that the proposed device has equal power division between the two output ports with <0.2 dB amplitude imbalance between them, better than 10 dB return loss and isolation and <2deg phase difference between the two output signals across the frequency band 3.1-10.6 GHz.

Proximity Coupled Interconnect Using Broadside Coupled Composite Right/Left-Handed Transmission Line

In this paper, the feasibility of composite right/left-handed transmission lines for realizing proximity coupled interconnects is reported. The proposed interconnects' resonant length can be miniaturized due to the zeroth order resonance supported by a composite right/left-handed transmission line resonator. In addition, the proposed interconnects can achieve broadside coupling because the zeroth order resonance occurs in the fast-wave region. Simulated and measured electric field distributions are shown to explain the broadside coupling phenomenon. To validate the arbitrary size and broadside coupling of the proposed interconnects, simulated and measured transmission characteristics are presented. The results show that low insertion loss can be achieved by using single and double broadside coupling between interconnects.

Compact Broadside Coupled Directional Coupler Based on Coplanar CRLH Waveguides

A compact broadside coupled (BSC) backward directional coupler based on composite right/left-handed (CRLH) coplanar waveguide (CPW) is proposed. The design is symmetric on both sides of the substrate and comprises of series gap capacitor, broadside-coupled capacitor, and shunt meandering short-circuited stub inductor. Compared to existing directional couplers, the proposed coupler has much smaller size, broader bandwidth, phase balance and easy fabrication. An equivalent circuit model including series inductance, capacitance, shunt inductance and capacitance tank has also been established. Good agreement between the full-wave simulation and equivalent circuit model verifies the effectiveness of the proposed circuit model. Measured bandwidth from 9.9 ∼ 14.7 GHz centered at 12 GHz (40%) is observed with the device size of 1.8 × 1.3 cm2.