Time-domain response of MIS coplanar waveguides for MMICs

An MIS coplanar waveguide propagating a slow-wave mode has been characterised in the time domain. The theoretical analysis proposed to obtain the time-domain response of the line gives results in good agreement with measurements. The circuit analysis used is suitable for the determination of spurious propagation effects, inherent to the use of miniature waveguides encountered in MMICs, such as Schottky contact coplanar lines and coupled microstrip lines laid on MIS substrates.     

Desktop computer appraisal of potential slow-wave propagation characteristics for Schottky coplanar lines

An original analytical model of the Schottky coplanar line is presented. Determination of the potential slowing factor is made with good accuracy. In its present form the model does not give the slow-wave mode frequency limitation. However, it can be useful to initialise computer analyses using FEM or SDA techniques, and to explain the effect of varying DC bias and geometrical parameters on propagation characteristics.     

The use of active traveling-wave structures in GaAs MMIC's

A coplanar waveguide has been fabricated on a modulation doped GaAs substrate in order to evaluate the potential of traveling-wave structures in microwave applications. The use of a Schottky contact center conductor enables the line to function as a slow wave structure in which the rf propagation characteristics can be modified with a dc bias. Measurements are reported at 10 GHz on simple structures, some of which incorporated an additional dielectric layer. Results show that slow-wave factors of between 8 and 24 are readily obtained with a loss per slow-wave factor of about 0.7 dB/mm. The practical issues relating to the application of such structures in phase shifters, chip size reduction, compact active filters and resonators are examined     

Guided-wave characteristics of periodic coplanar waveguides with inductive loading - unit-length transmission parameters

Periodic coplanar waveguides (CPWs) with inductive loading are thoroughly studied by resorting to unit-length transmission parameters, i.e., propagation constant and characteristic impedance, of an equivalent dispersive and/or lossy transmission line. The admittance-type method of moments (MoM) is at first formulated to full-wave modeling of a finite-cell periodic CPW with the two feeding lines and then the short-open-calibration procedure is carried out to deembed the two-port ABCD matrix of the core periodic CPW section. Thus, the above two parameters can be extracted from the MoM simulation to exhibit their guided-wave characteristics, i.e., slow-wave and bandstop behaviors. It is demonstrated for the first time that, within the bandstop or bandgap, the propagation constant must become complex with a nonzero attenuation constant, while the characteristic impedance appears purely imaginary. Three periodic CPW circuits with six finite cells are then characterized on a basis of the transmission-line theorem and the derived S-parameters are validated by Momentum simulation and RF measurement.     

Characteristics of Metal-Insulator-Semiconductor Coplanar Waveguides for Monolithic Microwave Circuits

Using a full-wave mode-matching technique, an extensive analysis is presented of the slow-wave factor, attenuation, and characteristic impedance of a metal-insulator semiconductor coplanar waveguide (MISCPW) as functions of the various structural parameters. Design criteria are given for low-attenuation slow-wave propagation. By a proper optimization of the structure, performances comparable with or even better than those of alternative structures proposed in the literature are theoretically predicted.     

Hybrid-mode analysis of homogeneously and inhomogeneously dopedlow-loss slow-wave coplanar transmission lines

A hybrid-mode analysis is presented to characterize the propagation properties of uniplanar slow-wave MIS (metal-insulator-semiconductor) coplanar transmission lines. The effect of homogeneous versus gradually inhomogeneous doping profile is investigated as well as the influence of the metal conductor losses and finite metallization thickness on the slow-wave factor and the overall losses. Numerical results indicate that thick-film MIS CPWs can support a slow-wave mode with moderate loss up to 40 GHz when the line dimensions are kept in the micrometer range. Furthermore, it is found that an inhomogeneous doping profile can reduce the overall losses and that the effect of metal conductor losses in heavily doped MIS structures is only marginal. On the other hand, in weakly doped or insulating GaAs material a lossy metal conductor leads to a higher propagation constant, exhibiting a negative slope with increasing frequency     

Quasi-TEM Analysis of "Slow-Wave" Mode Propagation on Coplanar Microstructure MIS Transmission Lines

We present a simple quasi-TEM analysis of "slow-wave" mode propagation on micron-size coplanar MIS transmission lines on heavily doped semiconductors and compare theoretical results with measurements on four such structures at frequencies from 1.0 to 12.4 GHz. Excellent agreement is found, which shows that the "slow-wave" mode propagating on these transmission lines is, in fact, a quasi-TEM mode. Relatively low-loss propagation along with significant wavelength reduction is observed. Conduction losses of the metal, which have been tacitly ignored in previously published "full-wave" treatments of "slow-wave" mode propagation, are included in the theory and are shown to dominate the attenuation at frequencies below 25 GHz and to still be significant at frequencies up to at least 100 GHz.     

Slow-Wave Coplanar Waveguide on Periodically Doped Semiconductor Substrate

A metal-insulator-semiconductor (MIS) coplanar waveguide with periodically doped substrate is described. An efficient numerical method is introduced in order to obtain the propagation constants and the characteristic impedances of the constituent sections of each period. Using the results, the characteristic of the periodic MIS coplanar waveguide is analyzed by Floquet's theorem. The theoretical study shows reduction of attenuation and enhancement of the slow-wave factor at certain frequencies, compared to the uniform MIS coplanar waveguide. This structure is experimentally simulated and shows good agreement theory.     

Broadband continuously variable microwave phase shifter employing a distributed Schottky contact on silicon

Fabrication details and microwave measurements are presented for the first realisation of a silicon, broadband, voltage-controlled, microwave phase shifter comprising a coplanar, slow-wave, Schottky-contact transmission line. This structure exhibits very little dispersion over the measured frequency range of 1?20 GHz. A voltage-dependent `wave compression? factor is observed that can be varied from 11.7 to 17.0 by varying the bias between ?6 and +0.1 V. Even though the device is fabricated on a `true? (lossy) semiconducting substrate, the attenuation per unit length is smaller than that reported for a similar structure fabricated on semi-insulating GaAs.     

Spectral domain analysis of coplanar superconducting line laid on multilayered GaAs substrate

Shows the influence of superconducting strips on the propagation characteristics of a MIS or a Schottky contact coplanar line laid on a GaAs substrate. The use of superconducting strips instead of metallic strips makes it possible to decrease losses. However the main purpose of the study is t point out the influence of the superconductor on the slowing factor and on the characteristic impedance.<>     

GaAs SAMP Device for Ku-Band Switching

Switchable attenuating medium propagation (SAMP) devices are coplanar transmission lines on an epitaxial semiconductor (GaAs) substrate. These transmission lines can be switched rapidly between states of high and low attenuation by controlling the width of a depletion layer under the center conductor. SAMP devices can easily be characterized by the use of transmission line theory. They are well suited for use in monolithic microwave integrated circuits (MMIC's). Experimental performance data and theoretical background will be presented.     

A spiral-shaped defected ground structure for coplanar waveguide

The authors present a spiral-shaped defected ground structure for coplanar waveguides (DGSCPW), which can be used as a kind of periodic structure for a planar transmission line. The proposed spiral-DGSCPW adopts spiral-shaped defects on both ground planes of CPW. Due to the spiral-shaped defects, the equivalent shunt inductance and slow-wave effects increase more rapidly than the standard CPW or CPW lines combined with the conventional PBG. The modeling and analysis to extract the equivalent circuit, increased slow-wave factor, and simulated and measured performances are presented.     

High-Performance Slow-Wave Transmission Lines With Optimized Slot-Type Floating Shields

A novel slow-wave transmission line with optimized slot-type floating shields in advanced CMOS technology is presented. Periodical slot-type floating shields are inserted beneath the transmission line to provide substrate shielding and to shorten the electromagnetic (EM) propagation wavelength. This is the first study that demonstrates how the wavelength, attenuation loss, and characteristic impedance can be adjusted by changing the strip length (SL), strip spacing (SS), and metal layer position of the slot-type floating shields. Wavelength shortening needs to be achieved with a tradeoff between slow-wave effect and attenuation loss. The slot-type floating shields with different SLs, SSs and metal layer positions are analyzed. It is concluded that minimum SL provides the most optimal result. A design guideline can be established to enable circuit designers to reach the most appropriate slot-type floating shields for optimal circuit performance. Transmission line test structures were fabricated by using 45-nm CMOS process technology. Both measurement and EM waves simulation were performed up to 50 GHz. Transmission lines are frequently used at a length of half- or quarter-wavelength. With a shortened wavelength, a saving in silicon area of more than 67% can be achieved by using optimized slot-type floating shields. Experimental results demonstrated a higher effective relative permittivity value, which is improved by a factor of more than 9, and a better quality factor, which is improved by a factor of more than 6, as compared to conventional transmission lines.      

Terahertz attenuation and dispersion characteristics of coplanartransmission lines

Experimental verification of analytic formulas for the dispersion and the attenuation of electrical transient signals propagating on coplanar transmission lines is presented. The verification is done in the frequency domain over a terahertz range although the experiments are in the time domain. The analytic formulas are obtained from fits to the full-wave analysis results. It is quantitatively verified that the full-wave steady-state solutions can be directly applied to the transient time-domain propagation experiments. Subpicosecond electrical pulses and an external electrooptic sampling technique are used to obtain the time-domain propagation data. From the Fourier transforms of the time-domain data both the attenuation and the phase information as a function of frequency are extracted. The dispersion and the attenuation characteristics are investigated for both coplanar waveguide and coplanar strip transmission lines. The investigation is carried out on both semiinsulating semiconductor and dielectric substrate materials. No observable losses caused by the semiconductor material are indicated     

Invited paper Characteristics of travelling waves along the non-linear transmission lines for monolithic integrated circuits: a review

A general analysis of non-linear wave propagation along transmission lines with voltage-dependent capacitance is presented. In particular, slow-wave structures like MIS and Schottky-barrier strip lines are examined. A spatial periodicity is included explicitly. The theoretical treatment is based on suitable equivalent circuits leading to characteristic wave equations. With regard to practical devices, the solutions show a variety of different phenomena as determined by the parameters of the non-linearity, dispersion and dissipation and the boundary conditions. Experimental results performed on a slow-wave model line are included.     

A general analysis of propagation along multiple-layersuperconducting stripline and microstrip transmission lines

A rigorous spectral-domain formulation for a superconducting stripline or microstrip transmission line with a multiple-layer dielectric substrate is presented. The formulation models the strip conductor as a surface current with an equivalent surface impedance, where the surface impedance is approximated in closed form when the strip is either much thinner or much thicker than a penetration depth. In either case the surface impedance is related to the complex conductivity of the material, which is calculated from a two-fluid model. Results are presented to show the slow-wave propagation and attenuation along both microstrip and stripline packages in a realistic multiple-layer configuration, which accounts for the field penetration into the superconducting ground planes     

Optoelectronic measurements of picosecond electrical pulsepropagation in coplanar waveguide transmission lines

Observations are presented concerning the effects of coplanar waveguide transmission lines on the propagation of picosecond electrical pulses using an optoelectronic time-domain measurement technique. Effects of various test structure design factors such as substrate thickness, thickness of transmission line metallization, discontinuity spacing, ground plane width, pulser/sampler line length, and pulser/sampler geometry on picosecond electrical pulse propagation in microwave/millimeter wave coplanar waveguide transmission lines are discussed, and schemes for minimizing the adverse effects of each of the above factors are provided     

Analysis of printed transmission lines for monolithic integrated circuits

Planar transmission lines formed with MIS and Schottky barrier contacts are analysed based on the spectral domain technique. Depending on the frequency and the resistivity of the substrates, three different types of fundamental modes are predicted. The calculated slow-wave factors and attenuation constants agree well with experimental results.     

Bias-dependent small-signal parameters of Schottky contact microstrip lines

Schottky contact lines are a type of microstrip on semiconducting substrata. The strip forms a rectifying metal-semiconductor interface, the Schottky contact. Schottky contact lines show interesting small-signal and large-signal properties, so far unknown in microwave IC-technology, due to the voltage-dependent capacitance per unit length.In this paper the small-signal transmission line properties are investigated. Formulas for the characteristic impedance and the propagation constant are given. Particular account is taken of the effect of varying external d.c. bias. measurements performed on microstrip lines with Al- and Au-Schottky contacts on n-type silicon are given.     

140 GHz基于CPWG单平衡基波混频GaAs集成电路

通过在300 μm厚度的GaAs衬底条件下,利用共面波导传输线实现了基波混频集成电路设计。利用半导体分析仪测试I-U和C-U曲线,并成功提取了相应的肖特基二极管模型。结合建立的肖特基二极管模型,代入Lange耦合器、中频结构和匹配网络等实现了140 GHz零中频基波混频片上电路,并加入了地-信号-地(GSG)测试封装。最终仿真结果表明：在固定中频1 GHz的条件下,变频损耗最优为-7 dB,3 dB带宽大于40 GHz。