A Si bipolar 28-GHz dynamic frequency divider

A dynamic frequency divider applying the regenerative frequency division principle has been developed. A spiral inductor on the silicon substrate used as a load is characterized, and an improved one-port model with the substrate resistance is discussed. A 1/16 frequency divider was implemented with a silicon bipolar technology with a cutoff frequency of 40 GHz. The operation frequency range was 11.8-28.1 GHz, covering the Ka band (18-26.5 GHz). The inductive load has improved the maximum operation frequency by 7%, compared with a conventional circuit. Complemented with a 21-GHz static frequency divider previously reported by the authors, the whole microwave frequency range up to 26.5 GHz has been completely covered with the silicon bipolar technology. The maximum operation frequency of a silicon MMIC has been extended to the millimeter-wave frequency region for the first time     

Novel unilateral circuits for MMIC circulators

A circuit which is equivalent to a four-port circulator with one port terminated, called a quasi-circulator, is proposed. The quasi-circulator can replace a conventional circulator even though it is not a complete circulator. Examples of novel three-port unilateral circuit modules, called quasi-circulator modules, which are the main part of the quasi-circulator are presented to realize very wide band circulators in monolithic microwave integrated circuit (MMIC) form without using ferrite materials and external magnets. The proposed modules are composed of an active out-of-phase divider and an active in-phase combiner or an active in-phase divider and an active out-of-phase combiner. The modules have many variations. All are very small and operate over a very wide frequency range. Two types of quasi-circulator modules that have very broadband operation up to X or Ku band are demonstrated. A quasi-circulator is also demonstrated. It is shown how an active circulator is realized by quasi-circulator modules     

InGaAs/InAlAs/InP collector-up microwave heterojunction bipolartransistors

Collector-up InGaAs/InAlAs/InP heterojunction bipolar transistors (HBTs) were successfully fabricated, and their DC and microwave characteristics measured. High collector current density operation (J_c>30 kA/cm²) and high base-emitter junction saturation current density (J₀>10^-7 A/cm²) were achieved. A cutoff frequency of f _t=24 GHz and a maximum frequency of oscillation f _max=20 GHz at a collector current density of J₀ =23 kA/cm² were achieved on a nominal 5-μm×10-μm device     

On the design and performance of a 6-18 GHz three-tier matrixamplifier

A 3×3 matrix amplifier for the 6-18-GHz frequency band has been developed. Using MESFETs fabricated on VPE (vapor-phase epitaxial) material, gains of G=23.5±0.5 dB with a maximum reflection loss of RL=-10 dB were obtained from 5.2 to 18.7 GHz. Gain improvement to G=29.1±1.1 dB at a worst-case reflection loss of RL=-7.5 dB between 4.6 and 18.3 GHz when MBE (molecular-beam epitaxial) material was used for the MESFETs. In addition to the experimental results, important design considerations, especially in regard to the termination impedances of the idle ports, are discussed     

A compact full MMIC module for Ku-band phase-lockedoscillators

A compact Ku-band phase-locked oscillator module has been developed in a full MMIC (monolithic microwave integrated circuit) configuration. The module includes an MMIC voltage-controlled oscillator, an analog frequency divider, and interstage amplifiers. The constituent monolithic chips are integrated in a very small single-package module and operate at the target frequencies without any external trimming or matching network. The oscillator is tuned more than 1 GHz with a constant output amplitude. The frequency-divided output is also obtained over the whole tuning range. Spurious output is not found at any frequency up to 22 GHz. In spite of the very low-Q factor of GaAs monolithic circuitry, the oscillator phase noise exhibited is less than -80 dBc/Hz, due to the high-gain, high-speed phase lock     

In0.52Al0.48As/InxGa1-xAs (0.53⩽x⩽0.70) lattice-matched and strainedheterostructure insulated-gate FETs

The DC and microwave properties of In_0.52Al_0.48 Al/In_xGa_1-xAs (0.53⩽x⩽0.70) heterostructure insulated gate field-effect transistors (HIGFETs) with a quantum well channel design are presented. DC and microwave transconductances (g_m) are enhanced as the In content is increased in the InGaAs channel. An intrinsic microwave g _m value of 428 mS/mm and a K-factor of 1140 mS/mm-V have been obtained for 1.0-μm gate length with the 65% In channel devices. The sheet charge density, drift mobility, transconductance, current-gain cutoff frequency (f_T), and maximum oscillation frequency (f _max) all show a continuous improvement up to 65% In content ( f_T=22.5 GHz with 53% and f_T=27 GHz with 65% In; the corresponding f_max change is from 6.5 to 8 GHz). The device performance degrades as the In content is increased to 70%. DC and microwave characteristics show the presence of negative differential resistance (NDR) up to 2.7 GHz     

A high-current pseudomorphic AlGaAs/InGaAs double quantum-wellMODFET

Double quantum-well modulation-doped field-effect transistors (MODFETs) with planar-doped lattice-strained AlGaAs/InGaAs structure have been fabricated and characterized at DC and microwave frequencies. At 300 K the 0.3-μm gate devices show a full channel current of 1100 mA/mm with a constant extrinsic transconductance of 350 mS/mm over a broad gate voltage range of 1.6 V. Excellent microwave performance is also achieved with a maximum available gain cutoff frequency f _mag of 110 GHz and a current gain cutoff frequency f _r of 52 GHz. A maximum output power of 0.7 W/mm with 30% efficiency is obtained at 18 GHz     

A dielectric model of the vegetation effects on the microwaveemission from soils

A layer of vegetation over the soil surface absorbs some of the radiation emitted from the soil and emits at its own temperature. This results in a reduction of the information in the microwave radiation about the soil surface. To study this problem further the authors use the model of F.T. Ulaby and M.A. El-Rayes (1987) for the dielectric constant of vegetation to estimate the absorption loss and optical depth, τ, of plant canopies for frequencies between 1 and 40 GHz. The authors treated τ as the product of a vegetation parameter b and vegetation water content, VW. They compared both the linear and square root (refractive) mixing models with the observed data in terms of the b parameter. These data were obtained from published reports on the values of τ and VW for crops ranging from prairie grass to corn and soybeans. The data fit the curve for the refractive model quite well. For the refractive model the value of b was independent of VW, while for the linear model there was some dependence on VW. For both models b is roughly proportional to the frequency     

Low-temperature microwave characteristics of pseudomorphic InxGa1-xAs/In0.52Al0.48Asmodulation-doped field-effect transistors

Low-temperature microwave measurements of both lattice-matched and pseudomorphic In_xGa_1-xAs/In_0.48As (x=0.53, 0.60, and 0.70) channel MODFETs on InP substrates were carried out in a cryogenic measurement system. The measurements were done in the temperature range of 77 to 300 K and in the frequency range of 0.5 to 11.0 GHz at different bias conditions. The cutoff frequency ( f_T) for the In_xGa_1-xAs/In_0.52Al_0.48As MODFETs improved from 22 to 29 GHz, 29 to 38 GHz, and 39 to 51 GHz, for x=0.53, 0.60, and 0.70, respectively, as the temperature was lowered from 300 to 77 K, which is approximately a 31% increase at each composition. No degradations were observed in device performance. These results indicate an excellent potential of the pseudomorphic devices at low temperatures     

A 1-μm polysilicon self-aligning bipolar process for low-powerhigh-speed integrated circuits

A double-poly-Si self-aligning bipolar process employing 1-μm lithography is developed for very-high-speed circuit applications. Epilayer doping and thickness are optimized for breakdown voltages and good speed-power performance. Shallow base-emitter profiles are obtained by combining low-energy boron implantation and rapid thermal annealing (RTA) for the emitter drive-in. A transit frequency f_T =14 GHz at V_BC=-1 V and a current-mode-logic (CML) gate delay of 43 ps at 30 fJ are achieved. For an emitter size of 1.0×2.0 μm² a minimum power-delay product of 15 fJ is calculated. Circuit performance capability is demonstrated by a static frequency divider operating up to 15 GHz     

High-frequency performance of submicrometer channel-length siliconMOSFETs

Polycide-gate silicon n-channel MOSFETs were fabricated on the basis of a standard 0.5-μm MOS technology and measured over the 1.5-26.5-GHz frequency range, in order to investigate the effects of channel-length reduction on device behavior at high frequency. Excellent microwave performances were obtained with a maximum operating frequency (f_max) and a unity-current-gain frequency f _t near 20 GHz for 0.5-μm-gate-length NMOS devices. An equivalent circuit for a MOSFET with its parasitic elements was extracted from measured S-parameter data. The influence of gate resistance, gate-to-drain overlap capacitance, substrate conductivity, and the transit-time effect between the source and drain on microwave characteristics was analyzed     

Dual-chip GaAs monolithic integration Ku-bandphase-locked-loop microwave synthesizer

Two novel multifunction monolithic chips, GaAs microwave monolithic integrated circuit (MMIC) and large-scale integration (LSI) chips, have been developed to realize an extremely small and lightweight microwave synthesizer. The MMIC includes a voltage-controlled oscillator, a dual-output buffer amplifier, a balun, and dynamic/static prescalers. To integrate these functions on a single chip, each circuit has been drastically reduced in size by utilizing a uniplanar MMIC configuration. The LSI includes a dual-modulus prescalar, programmable counters, and a phase/frequency comparator. By incorporating these two monolithic chips in the structure, a Ku-band microwave synthesizer has been fabricated in an 11-mm×23-mm flat package. The synthesizer to which these multifunction chips were applied had a tuning range broader than 1 GHz in the Ku-band with a flatness within 2 dB_pp. In spite of low-Q monolithic circuitry, single-sideband (SSB) phase noise was as low as -70 dBc/Hz     

75 GHz ECL static frequency divider using InAlAs/InGaAs HBTs

A 75 GHz static frequency divider in InAlAs/InGaAs transferred-substrate heterojunction bipolar transistor (HBT) technology is reported. This is the highest reported frequency of operation for a static frequency divider. The circuit has 60 transistors and dissipates 800 mW. The divider was operated at a clock frequency of 5.0 to 75 GHz     

K-band quasi-planar tapped combline filter and diplexer

Quasi-planar realizations of a combline bandpass filter and diplexer using multiple coupled suspended substrate striplines (MCSSSs) have demonstrated good performance at K-band without any tuning. The N MCSSSs excite N zero-cutoff-frequency quasi-TEM modes. A computer-aided filter design approach employing a rigorous spectral domain approach and 2N-port microwave circuit theory accounts for the effects of the N quasi-TEM modes, the couplings through nonadjacent MCSSSs, and cover height. Two 19.5-20.5 GHz MCSSS combline filters with different cover heights have been built and tested to compare their filter characteristics. The reduction in cover height has been found to decrease the amount of nonadjacent coupling through MCSSSs and to result in better filter stopband performance. An 18.5-19 GHz and 20-20.5 GHz MCSSS diplexer is also presented. All the measured results for the combline filters and diplexers agree well with the theoretic calculations     

A 2-18 GHz low-noise/high-gain amplifier module

The effectiveness of the two-tier matrix amplifier as a very-low-noise device with very high associated gains across multioctave frequency bands is theoretically and experimentally demonstrated. Experimental modules whose topology is based on a computer-optimized design exhibit an average noise figure of F=3.5 dB with an associated average gain of G=17.8 dB across the 2-18 GHz frequency band. These state-of-the-art results were achieved with GaAs MESFETs whose minimum noise figure is F=2.2 dB at 18 GHz and whose gate dimensions are 0.25×200 μm. The design considerations and the test results are discussed in detail     

Si/a-Si:H heterojunction microwave bipolar transistors with cut-offfrequencies ft above 5 GHz

The fabrication of a silicon heterojunction microwave bipolar transistor with an n⁺ a-Si:H emitter is discussed, and experimental results are given. The device provides a base sheet resistance of 2 kΩ/□ a base width 0.1 μm, a maximum current gain of 21 (V_CE=6 V, I_c=15 mA), and an emitter Gummel number G _E of about 1.4×10¹⁴ Scm^-4. From the measured S parameters, a cutoff frequency f_t of 5.5 GHz and maximum oscillating frequency f_max of 7.5 GHz at V_CE=10 V, I_c=10 mA are obtained     

Designer's Casebook-compact detector stabilized LCoscillators

An averaging or peak-voltage detector is generally incorporated in an RC oscillator for stabilizing its amplitude. Corresponding circuitry for an LC oscillator, however, is usually cumbersome because it requires two LC circuits tuned to the same frequency. An amplifying circuit that operates as a linear current divider for LC oscillators to overcome this problem is presented     

Comparisons of microwave performance between single-gate anddual-gate MODFETs

Both a 1.2-μm and a 0.3-μm gate length, n⁺-GaAs/InGa/n⁺-AlGaAs double-heterojunction MODFET have been fabricated with single-gate and dual-gate control electrodes. Extrinsic DC transconductance of 500 mS/mm has been achieved from a 0.3-μm single-gate MODFET. The device also has a current gain cutoff frequency f_T of 43 GHz and 14-dB maximum stable gain at 26 GHz with the stability factor k as low as 0.6 from the microwave S-parameter measurements. At low-frequency dual-gate MODFETs demonstrate higher gain than the single-gate MODFETs. However, the k of dual-gate MODFETs approaches unity at a faster rate. Power gain roll-off slopes of 3-, 6-, and 12-dB/octave have been observed for the dual-gate MODFETs     

Quarter-micrometer gate ion-implanted GaAs MESFET's with an f1 of 126 GHz

The fabrication and characterization of a 0.25-μm-gate, ion-implanted GaAs MESFET with a maximum current-gain cutoff frequency f_t of 126 GHz is reported. Extrapolation of current gains from bias-dependent S-parameters at 70-100% of I _dss yields f₁'s of 108-126 GHz. It is projected that an f₁ of 320 GHz is achievable with 0.1-μm-gate GaAs MESFETs. This demonstration of f₁'s over 100 GHz with practical 0.25-μm gate length substantially advances the high-frequency operation limits of short-gate GaAs MESFETs     

5 GHz high-temperature-superconductor resonators with high Q and low power dependence up to 90 K

The authors have fabricated high-temperature superconducting films made of TlBaCaCuO (2212) and YBaCuO (123) by postdeposition annealing techniques on (100) LaAlO₃ substrates. These films, especially the TlBaCaCuO(2212), exhibit high temperature operation, high Q (low surface resistance), and low power dependence. Both types of films have measured surface resistances which are better than 1/10 that of copper to 20 GHz. Microstrip resonators with a fundamental resonance frequency of 5 GHz were fabricated from these materials. The performance of the best resonator at 90 K (loaded Q>20000 at 5 GHz) was 50 times better than an analogous copper resonator (also measured at 90 K) and can handle more than 10 W of peak power in the resonator with only a small degradation of the Q. In addition, the shift of the resonator frequencies with temperature was fit to a two-fluid model