Frequency synthesizers up to 370 GHz

A new generation of frequency synthesizers up to 370 GHz is described. The main parts of them are microwave frequency synthesizer covering 11–15 GHz band, effective frequency multipliers-mixers using an opposite pair of planar Shottky diodes and a lock-in loop of a backward-wave oscillator tube covering millimeter and longer part of submillimeter wave bands with tens of milliwatts of output power. The ways of further increase in the operating frequency of such synthesizers are discussed.     

Frequency measurements of CF2CHF and SO2 laser lines and a new far infrared laser line of HDCO

The emission frequencies of several optically pumped far infrared laser lines of CH₂CHF, SO₂ and HDCO molecules have been measured by mixing them with a harmonic of a millimeter-wave synthesizer operating in the range 78–118 GHz. A new line of HDCO at 1886 GHz has been found.     

四路并行DDS合成技术在核磁共振中的应用

频率综合仪是核磁共振(NMR)谱仪的重要组成部分.随着微电子技术的迅速发展,用直接数字频率合成(DDS)方法来产生核磁共振射频信号已经成为可能.但是,由于数字集成电路工作频率的局限性,制约了DDS在高频段的应用.本文采用多路并行DDS合成技术,大大地提高了数字合成信号的频率范围。     

Compact Tunable Radiation Source at 180–1500 GHz Frequency Range

This paper is concerned with development of compact continuously tunable over all the submillimeterwave band (180 – 1500GHz) general purpose radiation source. The source consists of Backward Wave Oscillator (BWO) of the range 180 – 260 GHz or 250 – 375 GHz fixed in a small permanent magnet, followed by specially developed broadband frequency multiplier producing second, third, fourth, fifth and sixth harmonics of BWO fundamental frequency. The conversion losses for all the harmonics are measured. The estimations of output power of the source depending on frequency band are given. The examples of applications are presented in phase lock-in scanning BWO regime.     

Phase Lock-In of MM/SUBMM Backward Wave Oscillators: Development, Evolution, and Applications

The development and evolution of a Phase-Lock Loop (PLL) system up to the highest frequencies of Backward Wave Oscillators (BWO) is considered starting from the first submillimeter BWO PLL in 1970. Improvements and increase of working range near to Terahertz are followed. Development of the series of commercial BWO-based millimeter wave frequency synthesizers, extension of the BWO PLL beyond Terahertz as well as recent progress in fast millimeter wave frequency synthesizers are described. Applications of BWO PLL systems for physical and technical measurements are discussed and some proposals for the next generation of BWO-based synthesizers are presented.     

Saturation recovery EPR and ELDOR at W-band for spin labels

A reference arm W-band (94 GHz) microwave bridge with two sample-irradiation arms for saturation recovery (SR) EPR and ELDOR experiments is described. Frequencies in each arm are derived from 2 GHz synthesizers that have a common time-base and are translated to 94 GHz in steps of 33 and 59 GHz. Intended applications are to nitroxide radical spin labels and spin probes in the liquid phase. An enabling technology is the use of a W-band loop-gap resonator (LGR) [J.W. Sidabras, R.R. Mett, W. Froncisz, T.G. Camenisch, J.R. Anderson, J.S. Hyde, Multipurpose EPR loop-gap resonator and cylindrical TE₀₁₁ cavity for aqueous samples at 94 GHz, Rev. Sci. Instrum. 78 (2007) 034701]. The high efficiency parameter (8.2 GW^−1/2 with sample) permits the saturating pump pulse level to be just 5 mW or less. Applications of SR EPR and ELDOR to the hydrophilic spin labels 3-carbamoyl-2,2,5,5-tetra-methyl-3-pyrroline-1-yloxyl (CTPO) and 2,2,6,6,-tetramethyl-4-piperidone-1-oxyl (TEMPONE) are described in detail. In the SR ELDOR experiment, nitrogen nuclear relaxation as well as Heisenberg exchange transfer saturation from pumped to observed hyperfine transitions. SR ELDOR was found to be an essential method for measurements of saturation transfer rates for small molecules such as TEMPONE. Free induction decay (FID) signals for small nitroxides at W-band are also reported. Results are compared with multifrequency measurements of T_1e previously reported for these molecules in the range of 2–35 GHz [J.S. Hyde, J.-J. Yin, W.K. Subczynski, T.G. Camenisch, J.J. Ratke, W. Froncisz, Spin label EPR T₁ values using saturation recovery from 2 to 35 GHz. J. Phys. Chem. B 108 (2004) 9524–9529]. The values of T_1e decrease at 94 GHz relative to values at 35 GHz.     

Measurements of Dielectric Properties at Ka-Band Using a Fabry-Perot Hemispherical Open Resonator

A Fabry-Perot hemispherical open resonator is designed and constructed in order to measure dielectric properties of BeO in the Ka-band (26 – 40 GHz) frequency range. Based on both analytic calculations and simulations by a 3-D finite element electromagnetic code, HFSS, the hemispherical open resonator is designed to excite a TEM_0,0,17 mode at 28 GHz. The TEM_0,0,17 mode is experimentally identified by a field perturbation technique. Dielectric measurements are made by both frequency variation and length variation methods. Measurements show that permittivity and loss tangent of BeO are 6.69 and 6.5 × 10^–4 - 7.2× 10^–4, respectively, in the frequency range of 26 – 34 GHz.     

Generation of Submillimeter-Wave Radiation with GaAs Tunnett Diodes and InP Gunn Devices in a Second or Higher Harmonic Mode

Efficient second-harmonic power extraction was demonstrated recently with GaAs tunnel injection transit-time (TUNNETT) diodes up to 235 GHz and with InP Gunn devices up to 325 GHz. This paper discusses the latest theoretical and experimental results from second-harmonic power extraction at submillimeter-wave frequencies and explores the potential of using power extraction at higher harmonic frequencies to generate continuous-wave radiation with significant power levels at frequencies above 325 GHz. Initial experimental results include output power levels of more than 50 W at 356 GHz from a GaAs TUNNETT diode in a third-harmonic mode and at least 0.2–5 W in the frequency range 400–560 GHz from InP Gunn devices in a third or higher harmonic mode. The spectral output of these submillimeter-wave sources was analyzed with a simple Fourier-transform terahertz spectrometer and, up to 426 GHz, with a spectrum analyzer and appropriate harmonic mixers. Initial experimental results from a GaAs/AlAs superlattice electronic device at D-band (110–170 GHz) and J-band (170–325 GHz) frequencies are also included.     

An Integrated Sideband-Separating SIS Mixer Based on Waveguide Split Block for 100 GHz Band with 4.0–8.0 GHz IF

We have developed an integrated sideband-separating SIS mixer for the 100 GHz band based on the waveguide split block. The measured receiver noise temperatures with 4.0–8.0 GHz IF are less than 60 K in the LO frequency range of 90–110 GHz, and a minimum value of around 45 K is achieved at 100 GHz. The image rejection ratios are more than 10 dB in the frequency range of 90–110 GHz. We have installed the sideband-separating SIS mixer into an atmospheric ozone-measuring system at Osaka Prefecture University and successfully observed an ozone spectrum at 110 GHz in SSB mode. This experimental result indicates that the sideband-separating SIS mixer is very useful for astronomical observation as well as atmospheric observation.     

80–360 GHz very wide band millimeter wave network analyzer

An extension to a 20 GHz HP8510C Network Analyzer has been built for wideband measurements between 80 and 360 GHz. Improvements relative to the first version [1], [2] include new harmonic mixers, and an active doubler. Dynamic ranges up to 60 dB in transmission and 50 dB in reflection are obtained up to 280 GHz, with more than 50 GHz instantaneous bandwidth using waveguide calibration. Detection with a 30 dB dynamic range is obtained at 320 – 360 GHz. Time domain measurements give spatial resolution down to 2 mm.     

Phase Locking of 2-mm Wave Sources Upon High-Order IMPATT Multipliers

We describe experiments resulting in the phase locking of two electrically tunable 2-mm wave sources based on active high-order IMPATT multipliers. Phase locking modes were tested on a pair of identical multiplying sources (master and slave) with the tuning ranges 138.5+/–1.5 GHz (master) and 140.0+/– GHz (slave). The phase lock loop (PLL) system is used to lock the slave source to the master source. The multipliers of this type can translate the spectra of highly stable centimeter-wave oscillators to any part of the millimeter range with the output power 100÷20 mW over the 30 to 140 GHz range without additional amplification. The phase locked sources operate over a 3% frequency band with low phase noise and rapid frequency tuning. The amplitude-frequency characteristics of the sources are presented with the locking-mode signal spectra.     

Continuous-wave far-infrared ESR spectrometer for high-pressure measurements

We present a newly-developed microwave probe for performing sensitive high-field/multi-frequency electron spin resonance (ESR) measurements under high hydrostatic pressures. The system consists of a BeCu-made pressure-resistant vessel, which accommodates the investigated sample and a diamond microwave coupling window. The probe’s interior is completely filled with a pressure-transmitting fluid. The setup operates in reflection mode and can easily be assembled with a standard oversized microwave circuitry. The probe-head withstands hydrostatic pressures up to 1.6 GPa and interfaces with our home-built quasi-optical high-field ESR facility, operating in a millimeter/submillimeter frequency range of 105–420 GHz and in magnetic fields up to 16 T. The overall performance of the probe was tested, while studying the pressure-induced changes in the spin-relaxation mechanisms of a quasi-1D conducting polymer, KC₆₀. The preliminary measurements revealed that the probe yields similar signal-to-noise ratio to that of commercially available low-frequency ESR spectrometers. Moreover, by observing the conduction electron spin resonance (CESR) linewidth broadening for KC₆₀ in an unprecedented microwave frequency range of 210–420 GHz and in the pressure range of up to 1.6 GPa, we demonstrate that a combination of high-pressure ESR probe and high-field/multi-frequency spectrometer allows us to measure the spin relaxation rates in conducting spin systems, like the quasi-1D conductor, KC₆₀.     

A 275–370 GHz Receiver Employing Novel Probe Structure

We present the results of the development of a 275–370 GHz, fixed-tuned double sideband (DSB) receiver based on superconductor-insulator-superconductor (SIS) junction mixer. The mixer block uses a full height rectangular waveguide and employs a novel radial-like probe structure with integrated bias-T. The measured uncorrected receiver noise temperature is 30–50 K corresponding to about 2–3 quantum noise across the full frequency band with an IF from 3.8 to 7.6 GHz. The mixer is to be used on the Atacama Pathfinder EXperiment (APEX) submillimeter telescope in Chile.     

Characterization of Submillimeter Wave Absorbers from 200–600 GHz

This paper presents measurements of both specular and non-specular scattering from several submillimeter wave absorber materials designed for antenna testing and from low-cost carpet materials. The frequency range is 200–600 GHz in specular scattering, and 300–400 GHz in non-specular scattering measurements. The constructed bistatic test bench allows testing of the full continuous angular range of 0°–90°. The measurement results show large differences in performance of different materials. It is shown that reflectivities below –50 dB over limited angular ranges are possible with a correct alignment of the material. Also, low-cost carpet materials have lower than –15 dB reflectivities in most angles, and may be useful in non-critical parts of the antenna test range. The results can be used to optimise the absorber placement inside an antenna range, concerning both best performance and lowest cost.     

Novel 53/106 GHz Dual-Band MMW LC Oscillator Implemented in SiGe BiCMOS Technology

In this Paper, we present a fully integrated millimeter wave LC voltage-controlled oscillator (VCO), which employs a novel topology, operating at dual-band frequency of 53.22 GHz-band and 106.44 GHz-band. The low-phase noise performance of –107.3 dBc/Hz and –106.1 dBc/Hz at the offset frequency of 600 kHz, –111.8 dBc/Hz and –110.6 dBc/Hz at the offset frequency of 1 MHz around 53.22 GHz and 106.44 GHz are achieved using IBM BiCMOS-6HP technology, respectively. Two tuning ranges, of 52.7 - 53.8 GHz and 105.4 - 107.6 GHz for the proposed LC VCO are obtained. The output voltage swing of this VCO is around 1.8 V_p-p at the operation frequency of 53.22 GHz and 0.45 V_p-p at 106.44 GHz; the total power consumption is about 16.5 mW. To our knowledge, this is the first oscillator which operates at dual-band frequency above 50 GHz with the best preformance.     

Broad-band band-pass filter with variable center frequency and band width

This paper describes a new type of broad-band band-pass filter in which both the center frequency and band width are variable. The filter is composed of four balanced mixers, two local oscillators, an amplifier, and high-pass and low-pass filters. The center frequency and band width can be varied by changing the frequencies of two local oscillators. The center frequency is variable in the range 2–16 GHz, and the band width in the range 20–800 MHz.