Theoretical and Experimental Analysis of a Waveguide Mounting Structure

The induced EMF method has been extended and applied to derive the driving-point impedance of a common waveguide structure used for mounting small microwave devices. An equivalent circuit is developed and discussed in detail. Theoretical impedance curves are presented demonstrating the circuit characteristics for various configurations of the mount. The driving-point impedance of this mount has also been considered experimentally. A novel measurement technique is used based upon the use of subminiature coaxial line to gain electrical access to the terminal pair located inside the waveguide. A model of the measurement circuit, which enhances the accuracy of the results, providing excellent agreement between the theoretical and measured values, is developed. The multilateral nature of the circuit allows consideration of the mount in the waveguide as an obstacle to any incident propagating mode. Some related measurements have been made using standard techniques for the H/sub 10/ mode. It is anticipated that this formulation will permit accurate design of many components which previously required empirical methods based on limited experimental data.     

Characteristics of Waveguides with a Semiconductor Side Wall

The attenuation, guide wavelength, and characteristic impedance of rectangular waveguides with one high conductivity semiconductor side wall have been derived for the case of propagating TE/sub NO/ modes. These properties can be interpreted in terms of the penetration of the microwave electric field into the semiconductor material by an amount of the same order as, but generally unequal to, the classical skin depth. These theoretical results are evaluated for the special case of an indium antimonide side wall in RG 138/U waveguide operating at 110 Gc/s. The calculated attenuation lengths and guide wavelengths for this case are of such magnitude that they can be measured with reasonable accuracy, thus illustrating the value of this technique for the measurement of the electrical properties of semiconductor materials at the higher microwave frequencies.     

A Waveguide Impedance Meter for the Automatic Display of Complex Reflection Coefficient

A waveguide impedance meter has been developed, comprising some specially designed components and some components previously designed for other applications. When this circuit is used in conjunction with the X-band rapid sweep oscillator and suitable display and control circuits, the impedance focus of a waveguide component is automatically and rapidly measured and oscilIographically displayed in the reflection coefficient plane. A waveguide component having a 11/4-inch X 5/8-inch (large X-band) waveguide input port can be continuously measured throughout the frequency range extending from 8.5 to 9.6 kmc (12 per cent X-band). The bandwidth of the system is limited by the design bandwidth of the waveguide components. The plane of the impedance measurement may be referred to a plane internal to or external to the input port of the component under test. An expanded portion of the reflection coefficient plane may be displayed on the crt when small reflections are measured. The measurements of several representative impedances by the waveguide circuit were compared with slotted line measurements of these same components. For measurements of large reflections, standard /spl infin/ db swr full scale display, the maximum observed errors of the magnitude and phase of the reflection coefficient as measured by the waveguide circuit were 10 per cent and 5 degrees respectively. These maximum errors occurred for measurements performed at the ends of the 12 per cent frequency band. The average errors of the magnitude and phase of the reflection coefficient were 2.5 per cent and 2 degrees respectively. For measurements of small reflections, with the crt display of the reflection coefficient plane expanded to 6 db swr full scale, the maximum observed deviation of the waveguide circuit measurements from slotted line measurements was 0.5 db swr, and the average deviation was 0.2 db swr. The maximum errors again occurred at the ends of the 12 per cent frequency band.     

An input-impedance-based circuit model for coplanar waveguide-to-slotline T-junction

In this paper, an analytical input impedance formula is presented to characterize the coplanar waveguide (CPW)-to-slotline T-junction. Based on this impedance formula, one may establish a new circuit model for the T-junction, which may describe both the discontinuity effect and the mode conversion effect between even and odd CPW modes. This circuit model is validated by measurement and is then applied to design the back-to-back CPW-to-slotline and CPW-to-coplanar stripline transition structures.     

Characterization of IMPATT diodes at millimeter-wave frequencies

In order to evaluate the quality of a microwave device and to design a suitable circuit for it, the device must be characterized in terms of an equivalent circuit. At low microwave frequencies L through X bands, devices can be characterized in a relatively simple manner in conjunction with a coaxial transmission line network analyzer. At higher frequencies, such as millimeter-wave frequencies, however, the characterization must be carried out in a waveguide. This paper presents a technique for characterizing an IMPATT diode mounted in a waveguide and the associated circuit parasitics at millimeter-wave frequencies. The passive and active device parameters and the circuit parasitics, which have increased effects particularly at millimeter-wave frequencies, are evaluated by means of a computer-aided iterative curve-fitting method from the measured variation of the input impedance (VSWR) as a function of position of a movable short placed behind the device. The accuracy of the technique and the computer program are first checked by comparing the characteristics of anX-band IMPATT diode measured by the present technique and those measured by the network analyzer method. The characterization of a millimeter-wave IMPATT diode is then presented. A technique to achieve the stabilization required for the measurement of active parameters of the diode is also described. Comparison of the performance of an IMPATT diode amplifier calculated from the measured diode characteristics with the experimentally observed amplifier performance is then presented. It is shown that the device characterization technique can effectively be used for the analysis and design of a millimeter-wave circuit in which the device is used.     

Microwave modeling of 2-D active grid antenna arrays

A new measurement technique for determining the broadband driving point impedance of large two-dimensional active grid arrays is presented. The active array radiates a plane wave in the broadside direction when all elements are locked in phase. For analysis, the array is reduced to a single unit cell by exploiting the array symmetries. The driving point impedance of the unit cell is determined by using the dielectric waveguide measurement method (DWM). The approximations of the method are discussed, and the method is compared with other measurement techniques. Results are presented for four square arrays: dipole, bow-tie, double-vee and slot array. The measurement method is verified by comparing it to the full-wave theory in the whole range. It is shown that all four antenna arrays can be represented by very simple circuits that use only transmission lines as circuit elements. The bow-tie array is found to represent the best choice for broadband operation     

The Packaged and Mounted Diode as a Microwave Circuit

Suitable definitions of the elements in the equivalent circuit of a packaged diode yield a lumped-element circuit with an impedance at its terminals which is the same as the total radial-line impedance of the packaged diode with the outer surface of the diode taken as the terminal surface. Consideration of the packaged diode as a radial-line structure permits an analytical justification for the incorporation of the diode circuit with the circuits of waveguide, coaxial-line, and strip-line diode mounts. As a result, the lumped-element equivalent circuit of a packaged diode can be directly related to the microwave equivalent circuit of the diode and the mount together. Diode element values, which were obtained from low-frequency measurements, have been used in conjunction with the theoretically determined circuits of mounted diodes to predict resonant frequencies at X-band of waveguide, coaxial-line, and stripline mounts holding packaged diodes. Similarly, antiresonant frequencies of greater than 20 Gc/s have been predicted for diodes in a radial cavity. The validity of all these predictions has been verified by measurement.     

Spectral-domain analysis of E-plane waveguide tomicrostrip transitions

The spectral-domain technique and a residue calculus theorem are used to compute the input impedance of a microstrip transition to a rectangular waveguide. The transition consists of a printed circuit board inserted into a waveguide housing along the E-plane. The effects of the dielectric layer are considered in the present analysis. The behavior of the input impedance of the transition is studied with respect to the critical dimensions of the probe length and backshort location. Calculated results by the new formulation agree well with those computed using an integral equation and those measured at Ka -band frequencies     

一种销钉波导的分析方法

为了解决销钉波导端口阻抗参数计算复杂问题,采用一种新的分析方法,建立单销钉波导等效电路模型,利用级联规律,在分析三销钉波导时,把3个单销钉的等效电路级联起来进行分析,从电路角度解决销钉波导问题。把通过HFSS电磁仿真软件计算的销钉波导端口的阻抗参数与通过等效电路计算的销钉波导端口阻抗参数进行对比,两者结果一致。验证了该销钉波导等效电路的正确性以及这种销钉波导的分析方法的有效性。     

A novel processing technique to fabricate planar InGaAsP/InP electroabsorption waveguide modulators

A novel processing technique has been developed to fabricate planar electroabsorption waveguide modulators in compound semiconductor heterostructures. The lateral confinement of light is achieved by introducing controllable, reproducible, and stable stresses into semiconductor heterostructures using WNi surface stressor stripes, which also serve as electrodes for the waveguide modulators. Self-aligned helium implantation is employed to achieve electrical isolation using the Stressors as the templates for the ion masks. An increase as large as 33000 times has been obtained in the dc resistance between the neighboring waveguide modulators 25 μm apart. Propagation loss of 1.7 dB/cm is observed in the photoelastic waveguides at a wavelength of 1.53 μm following the He implantation. A post-implant thermal annealing at 310°C for 40 min increases the dc resistance between the neighboring devices to the maximum value, and at the same time reduces the optical loss to its value before ion implantation (less than 1 dB/cm). Using a combination of the photoelastic effect and helium implantation, planar InGaAsP/InP Franz-Keldysh-effect waveguide modulators 430 μm long with a 10 dB extinction ratio at 3 V for the TM mode have been fabricated. Planar electroabsorption quantum-confined Stark effect waveguide modulators have also been demonstrated. This planar device processing technique may prove valuable in future photonic integrated circuit technology.     

The Analysis of Hole-Gap Helical Groove Waveguide

The hole-gap helical groove waveguide, as a all-metal slow-wave circuit, has advantages of good heat dissipation and great size, and thus is suitable for use of mm TWT. By means of an approximate field theory, the expressions of the dispersion equation and the coupling impedance of the hole-gap helical groove waveguide is obtained in this paper. The influence of various circuit dimensions on the dispersion relation and the coupling impedance is discussed by the numerical computation.     

Semiconductor tuning circuit having constant Q over a wide range

A new type of variable tuning circuit using semiconductor inductance is described. This tuning circuit has a constant Q value over a wide range of frequency. Semiconductor inductance in this circuit is obtained using the impedance conversion method, however, there is no instability such as with negative impedance converter (NIC) and the structure of the circuit is simple. The common fault of semiconductor inductances is that their input impedance changes according to frequency, causing the Q value to vary widely. An attempt to solve this fault by the addition of a second ganged capacitor was made. Experimental results prove the validity of the theory, and confirm that this tuning circuit has practical applications. Applications of this circuit are shown at the end of this paper.     

Parametric Simulation and Optimization of Cold-test Properties for a 220 GHz Broadband Folded Waveguide Traveling-wave Tube

Characterized with full-metal structure, high output power and broad bandwidth, microfabricated folded waveguide is considered as a robust slow-wave structure for millimeter wave traveling-wave tubes. In this paper, cold-test (without considering the real electron beam) properties were studied and optimized by 3D simulation on slow-wave structure, for designing a 220 GHz folded waveguide traveling-wave tube. The parametric analysis on cold-test properties, i.e., phase velocity, beam-wave interaction impedance and cold circuit attenuation, were conducted in half-period circuit with high frequency structure simulator, assisted by analytical model and equivalent circuit model. Through detailed parametric analyses, interference between specified structural parameters is found on determining beam-wave interaction impedance. A discretized matrix optimization for interaction impedance was effectively carried out to overcome the interference. A range of structural parameters with optimized interaction impedance distributions were obtained. Based on the optimized results, a broadband folded waveguide with cold pass-band of about 80 GHz, flat phase velocity dispersion and fairly high interaction impedance was designed for a 220 GHz central frequency traveling-wave tube. A three-dB bandwidth of 20.5 GHz and a maximum gain of 21.2 dB were predicted by small signal analysis for a 28 mm-long lossy circuit.     

Six-Port Interferometric Technique for Accurate $W$ -Band Phase-Noise Measurements

An innovative six-port (SP) phase-noise measurement technique for millimeter-wave high-power sources is proposed in this paper. Simulation results using a 94-GHz rectangular waveguide SP circuit model validates the measurement principle for both millimeter-wave oscillators and amplifiers. Phase-noise measurement results of a 100-W extended interaction Klystron amplifier are presented and discussed. Compared to conventional methods, this new method allows accurate low-cost phase-noise measurements.     

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.     

折叠波导慢波电路的传输特性

研究了新型慢波结构折叠波导慢波电路的传输特性 ,利用等效电路法计算了折叠波导电路的色散特性、耦合阻抗和止带。分析和计算表明 ,该电路很适合用作短厘米波和毫米波大功率行波管的慢波结构。     

一种开敞式脊加载折叠波导慢波电路的高频特性

提出了一种开敞式脊加载折叠波导慢波结构.通过除去直波导段周围的金属边界,形成一种开敞式结构以减弱色散,同时在直波导段加脊以提高耦合阻抗.研究表明,和传统结构相比,新型结构在不影响带宽的前提下,有效提高了耦合阻抗,尤其在大功率设计情况下,耦合阻抗的提高接近1倍.     

Theoretical and experimental characterization of nonsymmetricallyshielded coplanar waveguides for millimeter-wave circuits

A quasi-planar structure, the nonsymmetrically shielded coplanar waveguide (NSCPW), is proposed as a quasi-TEM transmission line with advantageous characteristics for millimeter-wave circuit applications. Advantages in terms of broadband behavior and ease of machining, as well as device mounting and substrate mounting, are pointed out. An experimental method is developed which allows the evaluation of the transmission line spectrum in a very wide frequency band (15:1) with a single transmission measurement. The experimentally evaluated propagation characteristics of the dominant and higher order modes are shown to be in excellent agreement with the theoretical predictions based on the generalized transverse resonance technique. This method is also used for an extensive characterization of the structure in terms of characteristic impedance and useful frequency band     

Analysis of the Coaxial Ridge-Loaded Helical Groove Waveguide

The coaxial ridge-loaded helical groove waveguide is proposed in this paper. As an all-metal slow-wave circuit, it has advantages of good heat dissipation and great size, and thus is suitable for use of millimeter TWT. By means of field theory, the expressions of the dispersion equation and the coupling impedance of the coaxial ridge-loaded helical groove waveguide are obtained. The influence of various circuit dimensions on the dispersion relation and the coupling impedance is investigated by the results of numerical computation.     

Quadruple ridge-loaded circular waveguide phased arrays

An equivalent circuit representation of quadruple ridge-loaded waveguide arrays is presented which is useful for synthesis and optimization of array performance. The validity of this technique has been verified by simulator measurement.