Modeling of symmetric composite right/left-handed coplanar waveguides with applications to compact bandpass filters

This study proposes an equivalent-circuit model for the composite right/left-handed (CRLH) coplanar waveguide (CPW) comprising the series interdigital capacitor and shunt meandering short-circuited stub inductor in symmetric configuration. The new technique for extracting the equivalent-circuit elements of the CRLH CPW, which include inductances, capacitances, and resistances to represent the left-handed, right-handed, and lossy characteristics, is developed based on the effective medium concept. The applications to the compact resonators and filters are presented to emphasize the unique features of the CRLH CPW. A novel CRLH CPW resonator with a 0/spl deg/ effective electrical length at resonance is proposed, which gives a 49.1% size reduction when compared with the conventional half-wavelength resonator at 5 GHz. Based on the zeroth-order CRLH CPW resonators, an inductively coupled two-pole bandpass filter with 5.4% 3-dB bandwidth and 2.7-dB insertion loss at 5 GHz is implemented, and it is 51.4% more compact than the conventional structure. A good agreement among the results of the full-wave simulation, equivalent-circuit model, published data, and measurement demonstrates the effectiveness of the proposed modeling technique. To suppress the higher order harmonic spurious passbands, the electromagnetic-bandgap CPW structures are incorporated into the proposed CRLH CPW filter.     

A novel mixed conventional microstrip and composite right/left-handed backward-wave directional coupler with broadband and tight coupling characteristics

A novel backward directional coupler, composed of a conventional microstrip (C/spl mu/S) line and composite right/left-handed (CRLH) line, is proposed. This coupler is functionally backward but it is based on a forward-type coupling phenomenon. The coupler is shown to exhibit broad bandwidth and tight coupling characteristics. The theoretical circuit-model results are supported by full-wave and experimental evidence. A quasi 0-dB prototype with more than 50% bandwidth is demonstrated.     

Broad-band uniplanar hybrid-ring and branch-line couplers

Novel uniplanar 180° and 190° hybrids suitable for MIC and MMIC applications are described. The uniplanar crossover hybrid-ring coupler using a coplanar waveguide (CPW) and slotline provides substantially improved amplitude and phase characteristics over a broad bandwidth compared to conventional microstrip hybrid-ring couplers. Experimental results show that the new coupler has a bandwidth of more than one octave from 2 GHz to 4 GHz with a ±0.4-dB power dividing balance and a ±1° phase balance. A uniplanar two-branch directional coupler using a coupled rectangular slotline ring has also been developed. CPW-to-slotline transitions using uniform and nonuniform CPWs or slotlines are also discussed. These transitions are uniplanar and simple to fabricate. No via-holes are needed for ground connections, and integration with solid-state devices is easy. A pair of broadband transitions using CPW shorts and slotline radial stubs is demonstrated with a 1-dB bandwidth of more than 5.2:1     

Exact analytic solutions to the nonlinear wave equation for asaturable Kerr-like medium: modes of nonlinear optical waveguides andcouplers

Exact analytic solutions to the nonlinear wave equation for a lossless saturable Kerr-like medium are found. The nonlinearity is an intensity-dependent refractive index which saturates according to the model n²=n₀²±a|E|²/(1+b|E| ²). The solutions to the wave equation are used to determine the TE power-dependent dispersion relations, and therefore the guided modes, of a single waveguide structure and of a directional coupler whose coupling medium is the nonlinear saturable material. Although the interaction between the sinh- and cosh-like modes of the coupler, and therefore the coupling length, is not treated in this work, it is shown that the critical power, defined in the literature to be the level of input power above which 100% of the power cannot be switched between the guides of a coupler, is a mathematical misinterpretation in both saturable media as well as in nonsaturable Kerr media. The absence of a critical power in single waveguide structures is also demonstrated. Parameters of GaAs-based waveguides and of a GaAs-GaAlAs MQW coupling medium are used in the numerical analysis     

A Novel Quasi-Elliptic HTS Filter With Group-Delay Equalization Using Compact Quasi-Lumped Element Resonators in VHF Band

To produce a filter small enough to fit a 2-in wafer in the very high frequency (VHF) band while avoiding parasitic cross coupling among nonadjacent resonators, a novel quasi-lumped element resonator with interdigital capacitor, double-spiral inductor, and pad capacitor have been introduced. This resonator has not only a highly miniature structure but also a very weak far-field radiation. A ten-pole quasi-elliptic filter with group-delay equalization, which has a 7.1-MHz 1-dB passband and a center frequency of 257.5 MHz, is designed and fabricated on a 37.3 x mm x 30.1 x mm x 0.5 x mm LaAlO₃ substrate. The measured results showed a 0.24-dB insertion loss, a 15-dB return loss, and a 70-dB out-of-band rejection. Moreover, the group delay variation is less than 50 ns over 70% of the 1-dB passband and the band where the phase error ripple is within plusmn5^deg is more than 80% of the 1-dB passband. The overall experimental performance showed excellent agreement with the theory and simulation, which is a good proof of the advantage of our weak far-field radiation resonator. The result showed that the novel resonator is very suitable to fabricate narrowband ultrahigh frequency, VHF, or even lower frequency high-temperature superconductor filters on a 2-in wafer.     

Design of Compensated Coupled-Stripline 3-dB Directional Couplers, Phase Shifters, and Magic-T's—Part II: Broadband Coupled-Line Circuits

The problem of discontinuities in broadband multisection coupled-stripline 3-dB directional couplers, phase shifters, high-pass tapered-line 3-dB directional couplers, and magic-T's, regarding the connections of coupled and terminating signal lines, is comprehensively investigated in this paper for the first time. The equivalent circuit of these discontinuities proposed in Part I has been used for accurate modeling of the broadband multisection and ultra-broadband high-pass coupled-stripline circuits. It has been shown that parasitic reactances, which result from the connections of signal and coupled lines, severely deteriorate the return losses and the isolation of such circuits and also—in case of tapered-line directional couplers—the coupling responses. Moreover, it has been proven theoretically and experimentally that these discontinuity effects can be substantially reduced by introducing compensating shunt capacitances in a number of cross sections of coupled and signal lines. Results of measurements carried out for various designed and manufactured coupled-line circuits have been very promising and have proven the efficiency of the proposed broadband compensation technique. The theoretical and measured data are given for the following coupled-stripline circuits: a decade-bandwidth asymmetric three-section 3-dB directional coupler, a decade-bandwidth three-section phase-shifter compensator, and a high-pass asymmetric tapered-line 3-dB coupler.     

Novel coupled-line conductor-backed coplanar and microstrip directional couplers for PCB and LTCC applications

Novel coupled-line conductor-backed coplanar and microstrip directional couplers, convenient for manufacturing in standard printed circuit board (PCB) or low-temperature co-fired ceramic (LTCC) technology, are proposed. The coplanar coupler, consisting of a layered structure with four strips and covering a -10 to -2.6 dB coupling coefficient, is theoretically ideally impedance matched and perfectly isolated at all frequencies under the assumption of validity of quasi-static approximation and two-mode propagation. The microstrip coupler, a modification of the coplanar one, can be ideally compensated only in an area of strong coupling coefficients. The novel couplers are not sensitive to lateral misalignment of conductive layers, and not sensitive to thickness and dielectric permittivity tolerances of applied dielectric substrates. Preliminary experimental results for 2.7-, 3-, and 8.34-dB couplers, designed both in PCB, as well as LTCC technology are presented.     

A broadband and compact asymmetrical backward coupled-line coupler with high coupling level

A new wideband asymmetric microstrip coupled-line coupler with 3 dB coupling value and quadrature phase difference is presented. Compared with the conventional edge-coupled couplers, this structure, consisting of two different transmission lines (interdigital and conventional microstrip transmission lines) as coupled lines, achieves wider operating bandwidth and larger coupling level. The coupled-line length of the proposed structure is approximately λ_g/4. To characterize the structure, an equivalent circuit model has been established. A 3 dB designed and fabricated coupler with 0.2 mm spacing between coupled lines exhibits an amplitude balance of 2 dB from 2.2 GHz to 4.2 GHz. Good agreements between the full-wave simulation and equivalent circuit model results has been achieved and verified the effectiveness of the proposed circuit model. Also, measurement results have been presented.     

High-speed metal-semiconductor-metal photodiodes with Er-doped GaAs

Very high-speed MSM photodiodes have been fabricated on Er-doped GaAs over a doping range of 10¹⁸-10²⁰ cm^-3 . The impulse response (characterized by photoconductive sampling) of these diodes, with finger widths/spacings of 2 μm, has been found to be tunable over a range of about 3 ps-22 ps. Electro-optic sampling was used to characterize MSM diodes with finger widths/spacings of 0.5 μm and 1 μm on a sample with [Er]=10¹⁹ cm^-3, resulting in 3-dB bandwidths of 160 GHz and 140 GHz, respectively, corresponding to pulse widths of 2.7 ps and 3.3 ps. Correlation measurements were also done on the GaAs:Er samples, using an all-electronic Sampling Optical Temporal Analyzer (SOTA) structure     

Coupled-line metamaterial coupler having co-directional phase but contra-directional power flow

A coupled-line coupler comprising a microstrip line, edge-coupled to a negative-refractive-index line, exhibits co-directional phase but contra-directional Poynting vectors on the lines, leading to backward coupling. A key feature of this coupler is that it can support complex coupled modes. The resulting exponential field decay enables enhanced coupling with moderate line lengths and spacing. An example 3 dB device has been implemented and tested at 3 GHz.     

基于多层结构的新型左右手混合传输线

通过利用微带到共面波导的多层耦合结构,设计并制作了一种新型的左右手混合（CRLH）传输线。在该结构中,串联电容可以方便的通过上下两层金属导体之间的耦合加以实现,克服了传统的共面交指电容的电容值有限并且调谐复杂的缺点。同时也研究了判断左手通带的方法,并将该方法应用到所设计的结构中,结果表明该传输线结构具有相对较宽的左手带宽并且在左手通带内匹配良好。     

Inductively Compensated Parallel Coupled Microstrip Lines and Their Applications

A simple method using lumped inductors to compensate unequal even- and odd-mode phase velocities in parallel coupled microstrip lines is presented. The singly and doubly compensated cases are analyzed to enable the optimum inductor values and the electrical lengths of the compensated coupled lines to be calculated from closed-form expressions. The technique proposed not only improves the performance, but also yields a more compact design. To demonstrate the technique's broad range of applicability, the compensated coupled-line structure is used to enhance the performance of a 900-MHz Lange coupler, a 1-GHz multisection 10-dB coupler, a 900-MHz planar Marchand balun, and a 1.8-GHz parallel coupled bandpass filter.     

Broadband 4 $times$ 4 Butler Matrices as a Connection of Symmetrical Multisection Coupled-Line 3-dB Directional Couplers and Phase Correction Networks

An innovative approach for realization of broadband 4 times 4 Butler matrices, in which broadband symmetrical multisection 3-dB/90deg directional couplers are used as basic elements, has been presented. A new technique for realization of center crossover together with 45deg phase shifters is proposed where phase correction networks, consisting of a number of coupled-line sections, are applied. The use of the proposed phase correction networks allows to achieve equal-ripple 45deg differential phase characteristics in a wide frequency range. Numerical results for the design of broadband 4 times 4 Butler matrices consisting of multisection symmetrical 3-dB/90deg directional couplers having three, five, seven, and nine coupled-line sections in conjunction with phase correction networks having an appropriate number of coupled-line sections are given in a tabular form. A method of performance improvement for broadband Butler matrices by the combinatory use of directional couplers consisting of different number of coupled-line sections is also proposed. To verify the presented analysis a broadband 4 times 4 Butler matrix consisting of six 3-dB/90deg three-section symmetrical coupled-line directional couplers and two single-section coupled-line phase correction networks has been designed, manufactured, and measured. Results of measurements of the designed Butler matrix fully confirm the validity of the proposed technique of broadband 4 times 4 Butler matrix realization.     

A PCB-compatible 3-dB coupler using microstrip-to-CPW via-hole transitions

A 3-dB coupler by implementing microstrip-to-coplanar waveguide (CPW) via-hole transitions is proposed. The proposed coupler, with the advantages of wider coupled line widths and spacing without using any bonding wires, can eliminate the uncertain factors of conventional Lange couplers caused by the printed circuit board (PCB) manufacturing processes. The proposed coupler can be easily fabricated on a single-layer PCB substrate instead of using multilayer substrates. Good agreements between the simulation and the measurement in the frequency range from 0.45 to 5 GHz can be achieved. The measured results at the center frequency of 2.4 GHz have the return loss better than -15dB; the insertion loss of coupled and direct ports is about 3/spl plusmn/ 0.2dB and the relative phase difference of 89/spl plusmn/0.3/spl deg/. The dimension of the coupler is 3.1cm /spl times/ 1.8cm.     

First- and Second-Order Differentiators Based on Coupled-Line Directional Couplers

First- and second-order differentiators based on coupled-line directional couplers are presented. The time-derivative effect of coupled-line directional couplers is shown theoretically by applying Kirchhoff's laws to infinitesimal electromagnetically coupled transmission line sections. The time-derivation is accurate under the condition $Delta Tf_{0}gg 1/4$, where $Delta T$ is the pulse width and $f_{0}$ is the coupler center frequency; the required coupler operation frequency is thus inversely proportional to the pulse duration. The first-order differentiator, which is a simple coupled-line coupler, and the second-order differentiator, which requires in addition an interconnecting delay line, are demonstrated experimentally, and compared to ideal (mathematical) derivators.      

A design of wideband 3-dB coupler with N-section microstrip tandem structure

New design equations and a 3-dB microstrip coupler example for N-section tandem connected structure with wide bandwidth are presented. The proposed four-port S-parameters and equations are obtained from a port reduction method. The designed microstrip 3-dB coupler not only does not need high impedance lines, but also uses tight coupling gaps differently from conventional couplers such as Lange couplers, parallel coupled line couplers, etc. The measured data agrees well with the expected data, which show a wide bandwidth of 42%, an amplitude imbalance of /spl plusmn/0.5 dB, a phase unbalance of 1.0/spl deg/, and isolation characteristics of 15 dB at the band of 3.6 to 5.5 GHz.     

Analysis and Design of Branch-Line Hybrids with Coupled Lines

The scattering parameters of four-ports consisting of coupled lines with coupled or uncoupled connecting branches are derived in terms of the even- and odd-mode impedances and the lengths of the lines. These are used to analyze and formulate basic design procedures for the application of these structures as directional couplers including 0° and 90° 3-dB hybrids. The proposed new structures are quite compact at lower frequencies as compared to conventional uncoupled branch-line and rat-race hybrids. The results for the case of the coupled-line four-port with uncoupled branch lines also lead to closed-form expressions for the lengths and impedances of the lines required to nullify the effect of coupling between the main lines of a conventional branch-line coupler for use at higher frequencies. The measured response of the fabricated couplers is in good agreement with the theoretical predictions.     

三分量加速度地震检波器中3-dB耦合器设计

三分量加速度地震检波器检测加速度的核心部件是由2个3-dB耦合器级联而成的双M-Z干涉仪,3-dB耦合器的设计对三分量加速度地震检波器的检测精度尤为重要。介绍了三分量加速度地震检波器的结构和工作原理,导模之间的同向耦合理论。设置了3-dB耦合器波导的结构和计算参数。采用MATLAB对3-dB耦合器的输出功率进行仿真,仿...     

A CMOS uncooled heat-balancing infrared imager

In this paper, we report the fabrication, design, and testing of an uncooled 8×8 infrared imager based on an active pixel heat balancing technique. The imager is fabricated using a commercial CMOS process plus a simple electrochemical etch stop releasing step. The basic active pixel detector structure consists of a simple cascode CMOS amplifier in which the PMOS devices are built inside a thermally isolated floating n-well. The intrinsic coupling of the cascode currents with the self-heating of the well forms an electrothermal feedback loop that tends to maintain the well temperature constant, By employing the heat balance between incoming infrared radiation and the PMOS device power dissipation, the responsivity of the detector is controlled by the cascode biasing current. Measurements show responsivities between 0.3-1.2×10⁶ V/W when the infrared source is chopped at 20 Hz and a detectivity D*=3×10⁷ cm√(Hz)W^-1 at 30 Hz. Noise measurements suggest that a D* of 10⁸ cm√(Hz)W^-1 is achievable in this design     

Compact reflective-type phase-shifter MMIC for C-band using alumped-element coupler

The design and results of an ultra-compact single-load reflective-type monolithic-microwave integrated-circuit phase shifter at 6.2 GHz for a satellite radar system is presented in this paper, which has been fabricated using a commercial 0.6-μm GaAs MESFET process. A 3-dB 90° coupler with lumped elements enables significant circuit size reduction in comparison to former approaches applying microstrip branch line or Lange couplers. Phase control is enabled using MESFET varactors with capacitance control ratios (C_max/C_min ) of only four. Equations are derived to precisely describe the phase control ranges versus capacitance control ratios for different load configurations to allow efficient optimizations. Furthermore, the design tradeoff between low loss and high phase control range is discussed. Within a phase control range of 210°, a loss of 4.9 dB±0.9 dB and a 1-dB input compression point of higher than 5 dBm was measured for the designed phase shifter. The circuit size is less than 0.5 mm², which, to our knowledge, is the smallest reflective-type phase-shifter size reported to date