Showing papers by "Sander Weinreb published in 2012"

Low-Power Very Low-Noise Cryogenic SiGe IF Amplifiers for Terahertz Mixer Receivers

Abstract: State-of-the-art radio astronomy terahertz receivers utilize clusters of super-conducting mixers with cryogenic IF amplifiers. The critical parameters of the IF amplifiers are noise temperature, bandwidth, power consumption, input return loss, and physical size. This paper presents test data on three approaches to the IF amplifier; two are silicon-germanium (SiGe) monolithic microwave integrated circuit designs and the third is a discrete SiGe transistor miniature module. The amplifiers provide noise temperatures in the range of 5-15 K, from 1 to 6 GHz, at power consumptions as low as 2 mW.

Ultrawideband square and circular quad-ridge horns with near-constant beamwidth

Abstract: Two quadruple-ridged, flared horns, one with circular aperture and the other with square aperture, are presented achieving nearly constant beamwidth and excellent return loss over 6:1 and 4:1 frequency bandwidths, respectively, are presented. The circular and square quad-ridge horns are designed with nominal 10 dB beamwidths of 85 and 140 degrees, respectively. Radiation pattern measurements show excellent beamwidth stability in Φ = 0, 45 degree planes for both horns. Measured return loss is > 10 dB over the entire band for the circular quad-ridge horn and much better for 85% of the frequency band. The square quad-ridge horn also has return loss ≥ 15 dB over much of the target frequency range. To the best knowledge of the authors, these horns are the first demonstrations of ultrawideband reflector antenna feeds with near-constant beamwidth which can accommodate widely different optical configurations.

The Kilopixel Array Pathfinder Project (KAPPa), a 16 pixel integrated heterodyne focal plane array

Abstract: KAPPa (the Kilopixel Array Pathfinder Project) is developing key technologies to enable the construction of heterodyne focal plane arrays in the terahertz frequency regime with ~1000 pixels. The leap to ~1000 pixels requires solutions to several key technological problems before the construction of such a focal plane is possible. The KAPPa project will develop a small (16-pixel) 2D integrated heterodyne focal plane array for the 660 GHz atmospheric window as a technological pathfinder towards future kilopixel heterodyne focal plane arrays.

First observations with SuperCam and future plans

Abstract: Supercam is a 345 GHz, 64-pixel heterodyne imaging array for the Heinrich Hertz Submillimeter Telescope (HHSMT). By integrating SIS mixer devices with Low Noise Ampliers (LNAs) in 8 - 1x8 pixel modules, the size needed for the cryostat and the complexity of internal wiring is signicantly reduced. All subsystems including the optics, cryostat, bias system, IF boxes, and spectrometer have been integrated for all 64 pixels. In the spring of 2012, SuperCam was installed on the HHSMT for an engineering run where it underwent system level tests and performed rst light observations. In the fall of 2012 SuperCam will begin a 500 square degree survey of the Galactic Plane in ^(12)CO J=3-2. This large-scale survey will help answer fundamental questions about the formation, physical conditions, and energetics of molecular clouds within the Milky Way. The data set will be available via the web to all interested researchers.

Cryogenic Self-Calibrating Noise Parameter Measurement System

Abstract: A system for measuring the noise parameters of a device at cryogenic temperatures is described. The method includes the thermal calibration of a module consisting of a noise diode, a dispersive coupling network, a temperature sensor, heater, and a bias-tee. The magnitude and phase of the reflection coefficient presented by the module vary rapidly with frequency and the noise output of the module can be thermally calibrated by changing the temperature of the module with an internal heater. The resulting variable impedance-calibrated noise source can be used to measure noise parameters of transistors or amplifiers over a frequency range of 0.4 to 12 GHz via the wideband frequency-variation method. The calibration scheme is not unique to the module and may be applied in general to any noise source. Calibration and noise parameter measurements are made at cryogenic temperatures on a discrete transistor and two different low-noise amplifiers. The results are compared against theoretical values and those obtained using independent measurements. To the best of the authors' knowledge, this is the first measurement of a transistor's noise parameters at cryogenic temperatures using such techniques.