A Pre-TR Tube for High Mean Power Duplexing

A gas discharge tube for transmit-receive switching capable of handling average power levels up to at least 25 kw at 3000 Mc is described. The discharge is excited in the annular space between two concentric silica tubes and recovery time is controlled by the dimensions and gas pressure. In this way, a tube with constant characteristics during life has been achieved. The tube is mounted in a thick resonant iris, and sparking is avoided by using accurately ground silica mounted in a precision-bore hole. The arc loss of the tube in this form of mount is less than 0.1 db at 5 Mw peak 10 kw average, and the recovery time is about 100 µsec to 3 db. The attenuation is about 30 db, and the insertion loss is less than 0.1 db. Performance of this form of tube is discussed for average power levels of up to 50 kw in a phase-shift duplexer and 25 kw in a balanced duplexer, and the expected performance during life is also considered. Lives in excess of 10,000 hours are deduced from extrapolated data obtained with radioactive krypton in tubes operating at 10 kw average.     

Resonant Cavity Type Mode Transducer

This paper describes the operating principle and the properties of a resonant cavity type mode transducer which was newly devised. The theoretical equations necessary for designing the mode transducer from a TE/sub 10/ mode of a rectangular waveguide to an arbitrary mode of a circular waveguide have been derived, and a design method using the coupling parameters is discussed. The experiments were made for the rectangular TE/sub 10/-circular TE/sub 01/, mode transformation in the 50 Gc band. Showing an example (N=1), the transfer loss, input SWR and mode purity were 1.34 dB, 1.13, and 95 percent (power contents), respectively, at the resonant frequency of 50 Gc/s. The 3 dB bandwidth of the transfer loss was 83 Mc/s at the constant cavity length, but it can be made much larger if the cavity length is adjusted according to the frequency change. This mode transducer is unique in that various modes can be excited purely in the circular guide by merely varying the cavity length.     

The Elliptical Surface Wave Transmission Line

Electromagnetic wave propagation on an elliptical cross-sectional surface-wave transmission line is investigated theoretically. Characteristic equations for odd and even hybrid modes are derived and solved numerically. Expressions are obtained for power flow, energy storage and power loss using a perturbation method. Numerical results on propagation characteristics of three lower order modes are presented. The /sub 0/HE/sub 11/ mode is shown to have low attenuation particulary at high eccentricities. The propagation characteristics of lines of high eccentricities are found to be slowly varying functions of dimensions.     

The Dominant Cutoff Wavelength of a Lunar Line

A method is presented for calculating the lowest cutoff wavelength of a new microwave transmission line, the "lunar line," which is formed by two eccentric circular metal tubes connected with a metal bar or tangential to each other. The lunar-shaped cross section is approximated by introducing a series of steps in the outer guide wall and by dividing the cross section into m fan-shape regions. Thus, the problem is reduced to one of a multiple-step waveguide and can be solved by introducing the angular parameter alpha/sub i/ for the individual regions. The radial boundary conditions require a combination of Bessel functions of noninteger order for each region. The common boundaries between regions give m integral equations that represent the total power in one region transferred into the next region. The integral equations are solved approximately by solving only the first terms of an infinite series expansion of the tangential electric field at the common boundary. The solution of the m-stepped waveguide results in a system of 2m equations containing 2m unknowns: the cutoff wave number beta/sub c/, the order of the Bessel function p/sub i/, and the angular parameter alpha/sub i/. A successive approximation method is applied to obtain the cutoff wavelength. The calculated value is in close agreement with experimental results.     

Design and Operation of Four-Frequency Parametric Up-Converters

A theoretical analysis of a four-frequency parametric-diode up-converter is presented, retaining both sum and difference frequencies generated by mixing of pump and signal. Upper and lower sideband up-converters are compared, and it is shown that the gain limitations of the former can be overcome by combination with the latter, without appreciable loss of stability. Three different parametric amplifier configurations utilizing this four-frequency mode of operation have been designed, fabricated, and tested. These designs utilize sum-frequency up-conversion from 400 to 9400 Mc., and have exhibited noise figures below 1.5 db, gain in excess of 12 db, and bandwidths greater than 8 Mc.     

Synopsis of attenuation and emission investigations of 58 to 62 kMc frequencies in the earth's atmosphere

This synopsis of the investigation over the frequency interval of 58 to 62 kMc of emission and absorption of the earth's atmosphere between sea level and 100 thousand feet describes the measurements of the earth's atmosphere and simulated atmospheres and the results of the data analysis. The attenuation and emission of the atmosphere was found to be described within the limits of atmospheric variability by previously derived empirical equations. Between sea level and 100 thousand feet the attenuation between 58 and 62 kMc at the line center frequencies and between the line center frequencies has average values of 200 db and 145 db, respectively. The emission temperature into space from 100 thousand foot altitudes is 220°K between the lines and 225°K at line center frequencies. The emission temperature is a function of bandwidth and within the variability limits of the atmosphere, independent of incident solar radiation.     

K/sub a/-Band Ferrite Phase Shifter (Correspondence)

In 1957, Reggia and Spencer utilized a new technique to develop a phase shifter at 9.1 kMc. This letter reports an extension of their technique to K/sub a/-band frequencies. A maximum figure of merit of 1100 degrees of phase shift per db of loss has been achieved at 35 kMc +- 500 Mc.     

Gigacycle bandwidth coherent light traveling-wave phase modulator

A continuous duty coherent light phase modulator has been constructed which exhibits a bandwidth in the kilomega-cycles. A modulation index of unity has been obtained with a modulation peak power of about 12 watts. This power level is independent of the bandwidth of the modulation. This is contrasted with known microwave amplitude light modulators which require peak modulation power in the kilowatts and exhibit bandwidths of the order of 30 Mc. The extremely wide bandwidth operation with the low modulation power is obtained by applying the modulation voltage to the electro-optic material by means of a traveling-wave structure of the transmission line type. The direction of propagation of the light and of the modulation are colinear and the transmission line is designed so that the light progresses through the crystal in synchronism with the modulation on the line. The magnitude of the angular modulation was determined by illuminating the modulator with a ruby laser and examining the individual spectral components of the output with an S-band traveling-wave microwave phototube receiver. Similar to the behavior of conventional FM systems, a minimum in the carrier at a modulation index of 3.75 was observed as well as the appearance of the appropriate sidebands. These experiments were performed at 30 Mc and 1 Gc. It appears that the bandwidth of the modulator should be several octaves greater than 1 Gc, but this was not determined experimentally for equipment reasons. The attenuation of the 1 Gc modulation through the modulator and the balun at either end was 2 db and the attenuation of the light through the electro-optic crystals was about 6 db. A good portion of this later loss undoubtedly occurred at the interfaces between crystals.     

Quantitative analysis and optimization techniques for on-chip cache leakage power

On-chip L1 and L2 caches represent a sizeable fraction of the total power consumption of microprocessors. In nanometer-scale technology, the subthreshold leakage power is becoming one of the dominant total power consumption components of those caches. In this study, we present optimization techniques to reduce the subthreshold leakage power of on-chip caches assuming that there are multiple threshold voltages, V/sub T/'s, available. First, we show a cache leakage optimization technique that examines the tradeoff between access time and subthreshold leakage power by assigning distinct V/sub T/'s to each of the four main cache components-address bus drivers, data bus drivers, decoders, and static random access memory (SRAM) cell arrays with sense amplifiers. Second, we show optimization techniques to reduce the leakage power of L1 and L2 on-chip caches without affecting the average memory access time. The key results are: 1) two additional high V/sub T/'s are enough to minimize leakage in a single cache-3 V/sub T/'s if we include a nominal low V/sub T/ for microprocessor core logic; 2) if L1 size is fixed, increasing L2 size can result in much lower leakage without reducing average memory access time; 3) if L2 size is fixed, reducing L1 size may result in lower leakage without loss of the average memory access time for the SPEC2K benchmarks; and 4) smaller L1 and larger L2 caches than are typical in today's processors result in significant leakage and dynamic power reduction without affecting the average memory access time.     

Microwave Variable Attenuators and Modulators Using PIN Diodes

The PIN diode is a double diffused junction with an intrinsic layer separating the P and N regions. At frequencies above 100 Mc, the diode ceases to be a rectifier because of carrier storage and transit time effects. Its shunt capacitance is quite small because of the separation of the P and N regions by the I layer. Conductivity of the I region can be varied by a dc bias current and the device becomes an electrically variable resistor which can be used for microwave attenuators and modulators up to frequencies as high as 20 Gc. The PIN junctions are mounted on posts which are inserted in a 50-ohm strip transmission line as shunt elements, and a number of these elements, spaced a quarter wavelength apart at midband, are used to form an attenuator. At the appropriate bias current, yielding 50-ohm junction resistances, the diode elements are reactively compensated by choice of post dimensions so that they are effectively pure resistances, yielding an image attenuation of 4.2 db per element. Many elements can be used to attain any desired total attenuation and higher impedance end elements can be used to improve the SWR. Bandwidths of 4 to 1 with low SWR in both ON and OFF conditions are achievable. Maximum attenuation of 60 db, insertion loss of 1 db, and SWR of 1.5 are typical for a 12-diode attenuator and powers of the order of watts can be handled with negligible harmonic generation. When used as a pulse modulator, rise times of the order of 10 nsec are achievable.     

Octave-Bandwidth UHF/L-Band Circulator

Test data are presented on two aluminum-substituted yttrium-iron-garnet (YIG) materials that have low-saturation magnetizations that permit the extension of ferrite devices well into the UHF/VHF region. In particular, one composition has a saturation magnetization of 300 gauss and a line width of 50 oersteds. Measurements are presented that compare the new materials with previously available higher-saturation magnetization materials. A broad-band UHF/L-band four-port circulator that operates over a 2-to-1 frequency band has been developed, using this 300 gauss material. Insertion loss is 1 db or less from 665 to 1320 Mc (with constant magnetic field) and 0.5 db or less from 800 to 1150 Mc. A compact and favorable circulator package design was obtained by using coaxial hybrids and dielectric-loaded strip transmission line. Data on the broad-band magic-tee used in the circulator are included. Isolator measurements down to 200 Mc are reported. Reverse-to-forward magnetic-loss ratios of 36 at 600 Mc and 12 at 300 Mc were obtained.     

Millimeter Resonance Isolators Utilizing Hexagonal Ferrites

Ferrimagnetic resonance isolators operating over waveguide bandwidths have been developed in K, V and Q bands using hexagonal ferrites. Preliminary results on similar isolators operating in M and W bands have also been obtained. The materials employed in these isolators are highly anisotropic uniaxial hexagonal compounds. The compounds of interest for the first three frequency bands are from the Ni/sub 2/W family. The anisotropy field of Ni/sub 2/W is 12.6 kilo-oersteds (Koe). This uniaxial anisotropy field can be controlled over the range of 4 to 12.6 Koe by producing solid solutions of the above compound with that of Zn/sub 2/W and/or Co/sub 2/W, and controlled over the range of 12.6-19.0 Koe by aluminum substitutions. The following operating characteristics have been obtained over the full waveguide bands: K band (18-26.5 Gc), isolation (minimum)---25 db, insertion loss (maximum)---0.7 db, VSWR (maximum)--- 1.15, applied field---1000 oersteds, length---4 1/2 inches weight---6 1/2 ounces; v band (26.5-40 Gc), isolation (minimum)---25 db, insertion loss (maximum)---1.25 db, VSWR (maximum)---1.15, applied field---1000 oersteds, length---4 inches, weight---6 ounces; Q band (33-50 Gc), isolation (minimum)---25 db, insertion loss (maximum) ---1.5 db, VSWR (maximum)---1.15, applied field---1000 oersteds, length---3 1/2 inches, weight---5 1/2 ounces. Improved attenuation ratios and size are obtained when the band-width is reduced. Examples of this are K band where a ratio of 40 to 1 is maintained over a 4-Gc bandwidth in a 3-inch unit, and V band where a ratio of 40 to 1 is maintained over a 5-Gc bandwidth in a 2-inch unit. At the present time the M (50-75 Gc) and W (75-110 Gc) band units provide attenuation ratios exceeding 10 to 1 over 5-Gc bandwidths.     

E- and H-Plane Bends for High-Power Oversized Rectangular Waveguide

A study is presented of theoretical and experimental results of E- and H-plane bends for high-power oversized rectangular waveguide having cross-section dimensions in the range between 1..5 and 2.5 free space wavelengths. It is expected that waveguides having these dimensions will be able to transmit 50 to 100 kW of average power at X-band without water cooling. The transmission of at least 5.0 MW of peak power at X-band without pressurization is also a design objective. Dimensions for bends having low-mode conversion loss were determined by numerical integration of the coupled transmission line equations. The dominant TE/sub 10//spl square/ mode and four spurious modes were considered in these calculations. The results obtained for both constant curvature and sinusoidally shaped E- and H-plane bends are presented. A compact H-plane constant curvature bend is described for which the ratio of centerline radius to waveguide width is equal to 1.48. The measured mode conversion loss to the TE/sub 20//spl square/, TE/sub 30//spl square/, and TE/sub 40//spl square/ modes for an experimental model having a width equal to 2.25 inches was less than -20 dB in the frequency range from 7.0 to 11.0 Gc/s.     

Radiation from Bends in Dielectric Rod Transmission Lines

The radiation from the fundamental mode propagating around curved dielectric rod transmission lines is investigated experimentally with microwave frequencies. Three methods are used to determine the attenuation by radiation: measuring the insertion loss of bends, measuring the Q-factor of ring resonators, and measuring the Q-factor of sections of curved dielectric rod transmission lines terminated by large reflecting plates. The attenuation is found to depend mainly on the combination R lambda/sub 0//sup 2/ / r/sub 0//sup 3/ where R is the radius of curvature, lambda/sub 0/ the free space wavelength and r/sub 0/ a measure of the transverse field extent of the HE/sub 11/ mode. The experimental results are compared with theoretical predictions of other authors. The measured values of the attenuation constant are found to be smaller than the theoretical values. The distribution of the electromagnetic field near bends is recorded using a semiautomatic field plotter. From the field pictures, it can be concluded that the curved dielectric waveguide radiates tangentially from the outer side. The results presented will also be useful for understanding the mechanism of radiation from bent optical waveguides.     

TE Modes of the Dielectric Loaded Trough Line

The properties of TE modes on a dielectric loaded trough waveguide have been investigated. In the case of the dominant mode of this line (TE/sub 20/), families of design curves giving the field distribution, guide wavelength, power handling capability, wall losses, and dielectric losses as a function of operating wavelength, waveguide dimensions and dielectric constant are presented. For a loosely bound wave, the losses are comparable to those of conventional rectangular waveguide and the power handling capability is an order of magnitude greater. The apparatus and procedure used to measure guide wavelength, rate of field decay in the transverse direction, and attenuation are described. The measured performance is in close agreement with the theoretically predicted characteristics.     

A 6-kw Peak Power Varactor Duplexer

A strip transmission line varactor duplexer was developed for 6-kw operation at 1600 Mc for a missile application. The insertion losses were 0.6 db from antenna to receiver, and 0.3 db from transmitter to antenna. Transmitter to receiver isolation was greater than 40 db. The paper discusses the parameters leading to the choice of varactor and circuit configuration as to provide the power handling ability. Also discussed are the characteristics of interest to system designers that are peculiar to the varactor duplexer.     

Polygonal Coaxial Line with Round Center Conductor (Short Paper)

The complex potential function W = A (In z + C /sub n/z/sup n/) generates a zero-potential line approximating a regular polygon of N sides very closely, except in the nearly field-free region. By means of this function we work out the characteristic impedance, the power-carrying capacity, and the attenuation constant of the polygonal line of N sides wtth a round inner coaxial conductor in a closed form of elementary functions with good accuracy compared to more complex solutions. Results for N = 3 are believed to he nearly as good as those available in the literature.     

A 7-Gc/s Narrow-Band Waveguide Switch Using p-i-n Junction Diodes

A narrow-band waveguide switch with power capability in excess of 8 watts has been designed in WR137 waveguide. j-i-n diodes are used in band elimination filter sections. the attenuation in the reject band is greater than 80 dB over a 10 Mc/s range, and the passband loss is less than 0.5 dB.     

Theory of TEM Diode Switching

The theory of TEM diode switching is presented for purpose of understanding and designing TEM microwave diode switches. A few experimental results are reported for the purpose of supporting the theory and demonstrating the exceptional bandwidth possible. An analysis is given of the switching action of one and of two or more diodes as well as the biasing of the center conductor of a TEM transmission line over broad-frequency bandwidths without interacting the RF signal. The use of point-contact germanium, and gold-bonded germanium diodes for TEM switching is discussed. Some considerations of switching speed and maximum power-handling capacity are given. A coaxial transmission line switch has been constructed in which two gold-bonded diodes provide 26-db or greater isolation and insertion ranging from 1.6 db to less than 1 db from 40 Mc to 4000 Mc. The addition of a bias lead should increase the insertion loss 0.4 db or less over the 100-to-1 bandwidth, the maximum increase being at the upper and lower bounds.     

Electromagnetic-Wave Propagation in the Shielded Ring Line

A theoretical analysis is presented of a periodic structure consisting of equally spaced perfectly conducting rings. The dispersion relation satisfied by the Werent modes of the shielded ring line is determined. This analysis shows that cylindrically symmetric modes identical with those of smooth guides and hybrid modes can travel in this periodical structure. The asymptotic values of the dispersion relation show the different properties of these hybrid modes. The EH/sub n1/ modes can be slow, fast, or can travel at light velocity according to the frequency. The EH/sub nq/ (q > 1) modes are fast modes and exchange their cutoff frequencies for particular values of the geometrical parameters of the structure. These theoretical predictions are verified experimentally by recording the dispersion characteristics of the first modes. For deflecting radio-frequency structures, the fundamental EH/sub 11/ mode is interesting. This deflection constant is measured on a /spl pi/ / 2 wave structure.