Modal analysis of radial-resonator waveguide diode mounts

A method of calculating the driving-point and transfer admittances of waveguide diode mounts with radial resonators is presented. The method is applicable to a variety of mount configurations, including the widely used resonant-cap mount. The analysis uses multimodal admittance matrices to represent the radial regions and their coupling and includes the influence of the waveguide boundary conditions. The analysis proceeds by first determining (from the matching of tangential fields at the common boundary) the coupling between radial regions in the form of a mode-coupling matrix. By multiplying this matrix with the generalized admittance matrices of connecting radial regions to form an overall admittance matrix, the driving-point and transfer admittances for a general radial-resonator mount can be extracted. The method is demonstrated by application to the resonant-cap mount. The accuracy of the analysis is confirmed by comparison with experimental results     

Conditions of Oscillation for Waveguide Mounted Tunnel Diodes

Double frequency oscillation was observed in a waveguide mounted tunnel diode circuit, due to the frequency dependency of the waveguide's distributed parameters. A general analysis of the frequency dependent diode load is made and conditions of oscillation are formulated. The analysis is extended to a 1N3219A diode mounted in a tapered RG-52/U waveguide used as an oscillator. The load impedance to the tunnel diode is derived with the diode mounted at the center of the waveguide. A numerical example involving the RG-52/U waveguide mount is presented verifying the existence of double frequency oscillation and exemplifying the oscillation conditions stated. Off center diode mounting is examined. It is concluded that the waveguide mount's distributed parameters are highly frequency dependent at the center of the guide and thus double frequency oscillation can exist when a tunnel diode is mounted at that point. With the diode mounted at any other point, only one oscillation frequency can be observed. The frequencies of oscillation of a waveguide mounted tunnel diode oscillator are determined only by the real roots of the resistive component of the total tunnel diode load impedance.     

Small signal characterization of IMPATT diodes†

A precise method for the characterization of an encapsulated microwave diode, using an iterative computer procedure, is described. An accurate equivalent circuit for mount and package is obtained, and used in the estimation of the small signal properties of an IMPATT diode, from slotted-line measurements. Consistent diode junction parameters are obtained for various mount configurations. Agreement is obtained between the measured and predicted oscillation frequency of a radial-line cavity IMPATT oscillator, to within experimental error.     

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.     

Large-Signal Equivalent Circuits of Avalanche Transit-Time Devices

A large-signal analysis for IMPATT diodes is derived, which allows carrier multiplication by impact ionization to occur at every point in the diode. Therefore, the operating characteristics of IMPATT diodes with a wide range of realistic doping profiles can be investigated. For a given operating frequency, RF voltage, dc bias current, and doping profile, the admittance, power output, efficiency, bias voltage of a diode can be obtained. An equivalent circuit the diode package, microwave circuit mount and diode, is obtained experimentally. Using this circuit, the admittance of the diode is measured by a reflection-type circuit and an oscillator circuit as a function of the RF voltage, dc bias current, and frequency.     

Frequency response subtraction for simple measurement of intrinsiclaser dynamic properties

The authors describe a new technique for extracting the intrinsic laser-diode dynamic properties accurately. This simple technique eliminates the need for accurate microwave calibration of the test equipment and problems of microwave reflections, nonideal frequency response of laser mount, and detector. The effect of the parasitic components of the laser diode are also eliminated from the results so that measurements of important dynamic properties of the laser can be found up to high frequencies (10-20 GHz) on standard laser diodes. The techinque being used to measure variations of resonance peak and damping factor at different bias levels for a standard bulk active region 1.3 μm laser diode is shown     

Electromagnetic model of a radial-resonator waveguide diode mount

An electromagnetic model of a class of waveguide diode mounts that incorporates a radial resonator with the diode arbitrarily positioned is derived. The model is tested through comparison of numerical and experimental results for the input impedance of the mount. The tests show good agreement between theory and experiment and indicate that the model may be especially useful in investigating the effects of an off-centered positioning of the diode     

Optimization of a 250-GHz Schottky tripler using novel fabricationand design techniques

A technique for optimizing a diode waveguide mount for millimeter- and submillimeter-wave applications has been developed. The structure consists of a planar rectangular radiator for which an accurate derivation of impedance is available. The planar radiating probe incorporates the diode contacting tip, is fabricated integrally with the microstrip filter, and is used in a 230-290-GHz frequency tripler. Modification of the tripler using the described technique resulted in an improvement of ≈6 dB in available output power, compared to the authors' previous results for this device. Device output power exceeds 8.5 mW at 245 GHz for an input power of 132 mW. The best flange-to-flange efficiency (in excess of 11%) was achieved at 3.3-mW output power. This technique was then applied to a waveguide mount, incorporating two diodes contacted in parallel, so that greater input power could be handled. This resulted in a tripler with a maximum output power of 15 mW at 270 GHz for an input of 280 mW     

Computer Analysis of Microwave and Millimeter-Wave Mixers (Computer Program Descriptions)

The program analyzes the performance of single-diode microwave and millimeter-wave mixers. A Schottky-barrier diode is assumed, whose I-V and CV characteristics are known. The diode mount is taken to be lossless, but may have external loads at any number of sideband and local oscillator (LO) harmonic frequencies.     

A novel planar diode mixer for submillimeter-wave applications

A mixer employing a planar GaAs Schottky diode has been designed and tested over a 300-365 GHz bandwidth. Using a planar diode eliminates the disadvantages of mechanical instability and labor-intensive assembly associated with conventional whisker-contacted diodes. The mixer design process uses scale model impedance measurements for both the design of individual components and the measurement of impedances presented to the diode terminals by the mixer mount at fundamental and harmonic frequencies. Results from these impedance measurements are used in linear and nonlinear numerical mixer analyses to predict the mixer performance     

On the development of a high-efficiency 750-GHz frequency triplerfor THz heterodyne systems

The development of a 750-GHz Schottky varactor diode frequency tripler having a measured output power and efficiency of more than 120 μW and 0.8% at a frequency of 803 GHz is described. The output powers and efficiencies are the highest reported for this frequency. The 750-GHz tripler mount is analyzed and optimized using a scaled model of the mount. Measurements of the embedding impedance seen by the device, using the model, are compared with theoretical values     

Study of the Harmonic Effects for Waveguide Gunn-Diode Oscillator Optimization

The dependence on harmonic load conditions of waveguide Gunn oscillator performance is theoretically and experimentally studied. A simple waveguide mount is presented, which by controlling the diode harmonic load conditions, with one single adjustment permits considerable simultaneous improvement in output power, bias tuning, and varactor tuning linearities, as well as in frequency stability with the temperature. The oscillator noise level can also be minimized, though not at the same time as the other improvements. Finally, the usefulness of harmonic control in simplifying some typical thermal procedures is shown.     

Discussion of a 2-Gap Waveguide Mount (Short Papers)

An equivalent circuit is presented for a commonly used waveguide diode mount, providing the means for accurate theoretical analysis and design of components previously considered possible only by empirical means. Several applications are discussed and experimental confirmation is included for a variety of circuit configurations.     

Broad-Band Equivalent-Circuit Determination of Gunn Diodes

A method has been developed for the direct broad-band measurement of the impedance of a Gunn diode operating at a bias voltage exceeding threshold. This method is based upon determination of an equivalent-circuit model for the diode mount and package, which is found to be valid over the 1- to 20-GHz range. Using this circuit, the low-field diode equivalent circuit is found and takes the form of a parallel RC circuit as expected from the theory. An unusual result is that the low-field capacitance is found to be strongly dependent on the bias voltage; this dependence is presumed due to the free-carrier contribution to the effective dielectric constant. Some direct broad-band measurements are reported for an active Gunn diode biased beyond threshold. These measurements provide additional insight into the conditions under which significant parametric action may occur in a Gunn diode.     

Problems concerning the spatial distribution of deep impurities in semiconductors

Variation in the spatial distribution of recombination centres within a semiconductor causes difficulties in the interpretation of lifetime measurements. These difficulties are assessed for three methods of lifetime assessment; photoconductive decay, charge storage and diode reverse leakage current. A quantitative comparison of these methods is made on the basis of the simple model of a semiconductor consisting of a matrix of low recombination centre concentration containing embedded volumes of a much higher concentration. Under these conditions it is shown that the diode reverse leakage current is the most meaningful method of estimating the average recombination centre concentration. The charge storage method is seriously affected by clustering of recombination centres and the analysis shows how this method can be used to estimate qualitatively that clustering is present.     

基于89C52的二极管特性测试器的设计

利用单片机具有的智能程序控制的特点,设计了基于STC89C52单片机的"二极管特性测试器",可对二极管一般特性进行快速测试。通过稳定线性电流源给二极管加载恒定电流,然后由高精度模数转换器测试其压降,以此为基础可判断二极管好坏、检测二极管极性和测试二极管伏安特性等,避免了用万用表测试只能测得极性而不知其特性这一缺点。可用于电子设计制作过程中对二极管进行快速测试,以确定被测二极管是否满足电路的设计要求。     

Switching-time limitation in tunable multisection lasers

The impact of the thermal transient on the frequency switching of multisection tunable lasers is studied. A simple thermal model is used to calculate the amplitude and time evolution of the frequency transient due to the thermal properties of both the laser chip and its mount. Transient time constants as large as 200 μs for the laser chip and several hundred milliseconds for the diode mount are measured, limiting the applicability of these devices to systems where the frequency is switched at low rates. A method to compensate electrically for this transient by means of a passive net work is demonstrated     

Subharmonically Pumped Millimeter-Wave Mixers

The two-diode subharmonically pumped stripline mixer has a pair of diodes shunt mounted with opposite polarities in a stripline circuit between the signal and local oscillator inputs. The circuit has low noise and conversion loss and substantial AM local oscillator noise cancellation.The local oscillator frequency is about half the signal frequency. A novel diode chip, the notch-front diode, which has ohmic contacts on the chip faces adjacent the face containing the diode junctions, was developed for these circuits. The notch-front diode permits the low parasitic reactance of the waveguide diode mount to be achieved in stripline circuits. The best performance for a two-diode subharmonically pumped mixer with notch-front diodes was a 400 K mixer noise temperature, obtained at 98 GHz which is comparable to the best fundamental mixers in this frequency range. The performance over a 47-110-GHz frequency range for this circuit with commercial beam-lead diodes is also presented.     

Mount-independent equivalent circuit of the S4 diode package

Broadband-admittance measurements have been made on dummy S4 diode packages mounted in a coaxial line. By comparing these with the theoretical admittance of a lumped-component equivalent circuit for the package and its mount similar to that of Getsinger, a consistent set of mount-independent equivalent-circuit parameters for the package has been derived.