In this paper we discuss the latest developments of the STRIP instrument of the “Large Scale Polarization Explorer” (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the “B-modes” of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the “Observatorio del Teide” in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization.
Wideband receivers for the 3-mm band were developed for CARMA, the Combined Array for Research in Millimeterwave
Astronomy. Three cryogenic MMIC (monolithic microwave integrated circuit) amplifiers manufactured in InP 35-
nm technology are combined in a block with waveguide probes and gain equalizers to cover the 80–116 GHz band.
These are followed by a sideband-separating mixer that has two 17 GHZ wide outputs, for upper and lower sidebands.
Each receiver has a feed horn followed by a circular-to-linear polarizer and orthomode transducer. The two polarizations
are amplified by the cryogenic MMICs, and the outputs downconverted in sideband separating mixers, resulting in four
1–18 GHz channels that can be simultaneously correlated. The first receiver was tested in the lab, and on-sky tests
conducted at CARMA. Measured noise temperatures were in the range 40–70 K, with a sideband rejection of about
We report on the development of Argus, a 16-pixel spectrometer, which will enable fast astronomical imaging over the 85–116 GHz band. Each pixel includes a compact heterodyne receiver module, which integrates two InP MMIC low-noise amplifiers, a coupled-line bandpass filter and a sub-harmonic Schottky diode mixer. The receiver signals are routed to and from the multi-chip MMIC modules with multilayer high frequency printed circuit boards, which includes LO splitters and IF amplifiers. Microstrip lines on flexible circuitry are used to transport signals between temperature stages. The spectrometer frontend is designed to be scalable, so that the array design can be reconfigured for future instruments with hundreds of pixels. Argus is scheduled to be commissioned at the Robert C. Byrd Green Bank Telescope in late 2014. Preliminary data for the first Argus pixels are presented.
We report on the development of some of the key technologies that will be needed for a large-format Cosmic Microwave
Background (CMB) interferometer with many hundreds of wideband W-band (75-110 GHz) receivers. A scalable threebaseline
prototype interferometer is being assembled as a technology demonstration for a future ground- or space-based instrument.
Each of the prototype heterodyne receivers integrates two InPMonolithic Microwave Integrated Circuit (MMIC)
low-noise amplifiers, a coupled-line bandpass filter, a subharmonic balanced diode mixer, and a 90° local oscillator phase
switch into a single compact module that is suitable for mass production. Room temperature measurements indicate bandaveraged
receiver noise temperatures of 500 K from 85-100 GHz. Cryogenic receiver noise temperatures are expected to
be around 50 K.
The Q/U Imaging Experiment (QUIET) is an experimental program to make very sensitive measurements of
the Cosmic Background Radiation (CMB) polarization from the ground. A key component of this project is the
ability to produce large numbers of detectors in order to achieve the required sensitivity. Using a breakthrough in
mm-wave packaging at JPL, a polarimeter-on-a-chip has been developed which lends itself to the mass-production
techniques used in the semiconductor industry. We describe the design, implementation and performance of these
polarimeter modules for QUIET Phase I and briefly discuss the plans for further module development.