A low Terahertz (324 GHz) frequency generator is realized in 90 nm CMOS by linearly superimposing quadruple (N=4) phase shifted fundamental signals at one fourth of the output frequency (81 GHz). The ...developed technique minimizes the fundamental, second and third order harmonics without extra filtering and results in a high fundamental-to-4 th harmonic signal conversion ratio of 0.17 or -15.4 dB. The demonstrated prototype produces a calibrated -46 dBm output power when biased at 1 V and 12 mA with 4 GHz tuning range and extrapolated phase noise of -91 dBc/Hz at 10 MHz frequency offset. The linear superposition (LS) technique can be generalized for all even number cases (N=2k, where k=1,2,3,4,...,n) with different tradeoffs in output power and frequency. As CMOS continues to scale, we anticipate the LS N=4 VCO to generate signals beyond 2 Terahertz by using 22 nm CMOS and produce output power up to -1.5 dBm with 1.7% power added efficiency with an LS VCO + Class-B Power Amplifier cascaded circuit architecture.
We present deep CCS and HC7N observations of the L1495-B218 filaments in the Taurus molecular cloud obtained using the K-band focal plane array on the 100 m Green Bank Telescope. We observed the ...L1495-B218 filaments in CCS JN = 21-10 and HC7N J = 21−20 with a spectral resolution of 0.038 km s−1 and an angular resolution of 31″. We observed strong CCS emission in both evolved and young regions and weak emission in two evolved regions. HC7N emission is observed only in L1495A-N and L1521D. We find that CCS and HC7N intensity peaks do not coincide with NH3 or dust continuum intensity peaks. We also find that the fractional abundance of CCS does not show a clear correlation with the dynamical evolutionary stage of dense cores. Our findings and chemical modeling indicate that the fractional abundances of CCS and HC7N are sensitive to the initial gas-phase C/O ratio, and they are good tracers of young condensed gas only when the initial C/O is close to solar value. Kinematic analysis using multiple lines, including NH3, HC7N, CCS, CO, HCN, and HCO+, suggests that there may be three different star formation modes in the L1495-B218 filaments. At the hub of the filaments, L1495A/B7N has formed a stellar cluster with large-scale inward flows (fast mode), whereas L1521D, a core embedded in a filament, is slowly contracting because of its self-gravity (slow mode). There is also one isolated core that appears to be marginally stable and may undergo quasi-static evolution (isolated mode).
We present an overview of solid-state integrated circuit amplifiers approaching terahertz frequencies based on the latest device technologies which have emerged in the past several years. Highlights ...include the best reported data from heterojunction bipolar transistor (HBT) circuits, high electron mobility transistor (HEMT) circuits, and metamorphic HEMT (mHEMT) amplifier circuits. We discuss packaging techniques for the various technologies in waveguide modules and describe the best reported noise figures measured in these technologies. A consequence of THz transistors, namely ultra-low-noise at cryogenic temperatures, will be explored and results presented. We also present a short review of power amplifier technologies for the THz regime. Finally, we discuss emerging materials for THz amplifiers into the next decade.
Accurate measurement of angular positions on the sky requires a well-defined system of reference, something that in practice is realized by the International Celestial Reference Frame (ICRF) with ...observations of distant (typical redshift <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula>1) Active Galactic Nuclei (AGN). At such great distances a subset of these objects exhibit as little as 10<inline-formula><tex-math notation="LaTeX">-</tex-math></inline-formula>50 <inline-formula><tex-math notation="LaTeX">\mu</tex-math></inline-formula>as/year observed parallax or proper motion, thus giving the frame excellent spatial and temporal stability. Until fairly recently the majority of AGN centered imaging was accomplished in the S (2.3 GHz) and X (8.4 GHz) radio frequency bands, however S-band observations for reasons such as sensitivity "plateauing", increased source structure (jets), and radio frequency interference (RFI) have become less productive. Following spacecraft telemetry moves to higher frequencies and a desire to strengthen JPL's leadership in defining the next-generation of celestial reference frames has motivated the development of a "Quad-band" prototype receiver that operates in X, Ku, K, and Ka band in both right hand (RCP) and left hand (LCP) circular polarization. The goal of this receiver is to achieve less than a 20 % increase in noise over the Jansky Very Large Array (JVLA, NRAO) performance specification, which in such a wide bandwidth represents a revolutionary capability. To evaluate the various technical developments of the 8 GHz<inline-formula><tex-math notation="LaTeX">-</tex-math></inline-formula>40 GHz receiver the feedhorn optical beam was designed to interface to the US based Very Long Baseline Array (VLBA). The receiver's intermediate frequency (IF) spans 4 GHz<inline-formula><tex-math notation="LaTeX">-</tex-math></inline-formula>8 GHz, giving rise to up to eight 4 GHz IF channels for a fully populated instrument. This paper outlines the technical development of a 2<inline-formula><tex-math notation="LaTeX">^{1}</tex-math></inline-formula>/<inline-formula><tex-math notation="LaTeX">_{2}</tex-math></inline-formula> octave wide (8 GHz<inline-formula><tex-math notation="LaTeX">-</tex-math></inline-formula>40 GHz) X-Ka band prototype receiver, fulfilling a need for super broadband technology within the VLBI network. An important additional benefit of the wideband receiver approach is its simplicity and low cost of operation.
Millimeter and submillimeter indium phosphide (InP) microwave monolithic integrated circuits (MMICs) are increasingly used in applications spanning Earth science, astrophysics, and defense. In this ...paper, we characterize direct detection and heterodyne gain fluctuations of 35-, 30-, and 25-nm gate-length InP MMIC low-noise amplifiers (LNAs) designed for the 200-670-GHz frequency range. Of the twelve MMIC LNAs, five pairs have also been measured in multistage or cascaded configuration. In direct detection mode, the MMICs room temperature (RT) 1/f noise spectrum and responsivity were measured. From these the power spectral density, the noise equivalent temperature difference (NETD), equivalent system noise temperature (T sys DD ), and low-frequency normalized gain fluctuations (ΔG/G) are derived. On the same set of MMIC LNAs, using a heterodyne down conversion technique, the Allan variance method is applied to obtain the Allan stability time and normalized 4-8 GHz gain fluctuation noise at both RT and two cryogenic temperatures. We find in the case of 35-, 30-, and 25-nm gate-length InP MMIC LNAs that the derived direct detection and heterodyne gain stability is highly process dependent with only a secondary dependence on gate periphery, the number of gate fingers, and/or gain stages. This observation confirms the underlying solid-state physics understanding that gain fluctuation noise is the result of a temporal distribution of the generation and recombination of electron free carriers due to lattice defects and surface impurities. Upon cooling below ~66 K, it is observed that on average gain fluctuations increase by ≳2.2× and the Allan stability time decreases by ~2.5×. The presented measurement results compare favorably
Abstract
We present deep CCS and HC
7
N observations of the L1495-B218 filaments in the Taurus molecular cloud obtained using the
K
-band focal plane array on the 100 m Green Bank Telescope. We ...observed the L1495-B218 filaments in CCS
J
N
= 2
1
–1
0
and HC
7
N
J
= 21−20 with a spectral resolution of 0.038 km s
−1
and an angular resolution of 31″. We observed strong CCS emission in both evolved and young regions and weak emission in two evolved regions. HC
7
N emission is observed only in L1495A-N and L1521D. We find that CCS and HC
7
N intensity peaks do not coincide with NH
3
or dust continuum intensity peaks. We also find that the fractional abundance of CCS does not show a clear correlation with the dynamical evolutionary stage of dense cores. Our findings and chemical modeling indicate that the fractional abundances of CCS and HC
7
N are sensitive to the initial gas-phase C/O ratio, and they are good tracers of young condensed gas only when the initial C/O is close to solar value. Kinematic analysis using multiple lines, including NH
3
, HC
7
N, CCS, CO, HCN, and HCO
+
, suggests that there may be three different star formation modes in the L1495-B218 filaments. At the hub of the filaments, L1495A/B7N has formed a stellar cluster with large-scale inward flows (fast mode), whereas L1521D, a core embedded in a filament, is slowly contracting because of its self-gravity (slow mode). There is also one isolated core that appears to be marginally stable and may undergo quasi-static evolution (isolated mode).
Recent advancements in transistor technology, such as the 35 nm InP HEMT, allow for the development of monolithic microwave integrated circuit (MMIC) low noise amplifiers (LNAs) with performance ...properties that challenge the hegemony of SIS mixers as leading radio astronomy detectors at frequencies as high as 116 GHz. In particular, for the Atacama Large Millimeter and Submillimeter Array (ALMA), this technical advancement allows the combination of two previously defined bands, 2 (67-90 GHz) and 3 (84-116 GHz), into a single ultra-broadband 2+3 (67-116 GHz) receiver. With this purpose, we present the design, implementation, and characterization of LNAs suitable for operation in this new ALMA band 2+3, and also a different set of LNAs for ALMA band 2. The best LNAs reported here show a noise temperature less than 250 K from 72 to 104 GHz at room temperature, and less than 28 K from 70 to 110 GHz at cryogenic ambient temperature of 20 K. To the best knowledge of the authors, this is the lowest wideband noise ever published in the 70-110 GHz frequency range, typically designated as W-band.
An MMIC Low-Noise Amplifier Design Technique Varonen, Mikko; Reeves, Rodrigo; Kangaslahti, Pekka ...
IEEE transactions on microwave theory and techniques,
03/2016, Letnik:
64, Številka:
3
Journal Article
Recenzirano
In this paper we discuss the design of low-noise amplifiers (LNAs) for both cryogenic and room-temperature operation in general and take the stability and linearity of the amplifiers into special ...consideration. Oscillations that can occur within a multi-finger transistor are studied and verified with simulations and measurements. To overcome the stability problem related to the multi-finger transistor design approach a parallel two-finger unit transistor monolithic microwave integrated circuit LNA design technique, which enables the design of wideband and high-linearity LNAs with very stable, predictable, and repeatable operation, is proposed. The feasibility of the proposed design technique is proved by demonstrating a three-stage LNA packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology that achieves more than a 20-dB gain from 75 to 116 GHz and 26-33-K noise temperature from 85 to 116 GHz when cryogenically cooled to 27 K.
In this letter, a rectangular waveguide to conductor backed-coplanar waveguide electromagnetic transition suitable of operating at sub-millimeter wave frequencies is demonstrated. The dipole based ...transition is fabricated using InP monolithic microwave integrated circuit technology. The compact transition eliminates wire-bonding problems (return loss and insertion loss) and is suitable for direct integration of sub-millimeter wave monolithic integrated circuits. Measured transition loss of ~1 dB has been achieved in the frequency range of 340 to 380 GHz.
In this paper, we report on a new 6-way MMIC power combiner amplifier utilizing cavity modes. The combiner is designed around a square cavity operating in the TM 320 electromagnetic mode. Such a ...configuration produces a total of 6 lobes of maximum field intensity inside the cavity. By placing probes (attached to MMIC amplifier chips) in alignment with the points of maximum field strength, a highly compact power combiner can be achieved. We illustrate this concept using a set of 1 Watt W-band GaN MMIC chips, placed in layered copper sheets and oriented so the MMICs line up with the regions of maximum field strength. A 6-way power combiner was built and was able to deliver 5.5 Watts of output power and 13.4% PAE using a miniature package.
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