Rohit Gawande

A 75–116-GHz LNA with 23-K noise temperature at 108 GHz

In this paper we present the design and measurement results, both on-wafer and in package, of an ultra-low-noise and wideband monolithic microwave integrated circuit (MMIC) amplifier in the frequency range of 75 to 116 GHz. The three-stage amplifier packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology achieves a record noise temperature of 23 K at 108 GHz when cryogenically cooled to 27 K. The measured gain is 22 to 27 dB for frequency range of 75 to 116 GHz. Furthermore, the amplifier utilizes four-finger devices with a total gate width of 60 μm resulting in higher output power. Therefore, we consider that this amplifier achieves state-of-the-art performance in terms of bandwidth, noise temperature, gain, and linearity so far reported for cryogenically cooled amplifiers around W-band.

W-Band cryogenic InP MMIC LNAs with noise below 30K

In this paper, we describe two monolithic millimeter-wave integrated circuit (MMIC) low noise amplifiers (LNAs) for W-Band which have a noise temperature of 30K or better over a wide bandwidth when cryogenically cooled. The LNAs were designed and fabricated in NGCs InP HEMT MMIC process having 35 nm gate length and employing an InAs Composite Channel (IACC). A two-stage amplifier exhibits room temperature S21 gain of 15–18 dB, and cryogenic gain of 20 dB with minimum noise temperature of 25K at 95 GHz, and less than 40K noise temperature between 75–105 GHz. A three-stage amplifier exhibits 29 dB of S21 gain, and a cryogenic noise temperature below 30K over the range of 94–109 GHz. We discuss the design of the amplifiers, measured and simulated S-parameters, and cryogenic measurements. To our knowledge, these are the highest frequency and lowest noise temperatures ever reported for InP cryogenic LNAs covering W-Band.

W-band heterodyne receiver module with 27 K noise temperature

We present noise temperature and gain measurements of a W-band heterodyne module populated with MMIC LNAs designed and fabricated using a 35 nm InP HEMT process. The module has a WR-10 waveguide input. GPPO connectors are used for the LO input and the I and Q IF outputs. The module is tested at both ambient (300 K) and cryogenic (25 K) temperatures. At 25 K physical temperature, the module has a noise temperature in the range of 27–45 K over the frequency band of 75–111 GHz. The module gain varies between 15 dB and 27 dB. The band-averaged module noise temperature of 350 K and 33 K were measured over 80–110 GHz for the physical temperature of 300 K and 25 K, respectively. The resulting cooling factor is 10.6.

An MMIC low-noise amplifier design technique

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.

Argus: a 16-pixel millimeter-wave spectrometer for the Green Bank Telescope

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.

Technology developments for a large-format heterodyne MMIC array at W-band

We report on the development of W-band (75–110 GHz) heterodyne receiver technology for large-format astronomical arrays. The receiver system is designed to be both mass producible, so that the designs could be scaled to thousands of receiver elements, and modular. Most of the receiver functionality is integrated into compact monolithic microwave integrated circuit (MMIC) amplifier-based multichip modules. The MMIC modules include a chain of InP MMIC low-noise amplifiers, coupled-line bandpass filters, and sub-harmonic Schottky diode mixers. The receiver signals will be routed to and from the MMIC modules on a multilayer high-frequency laminate, which includes splitters, amplifiers, and frequency triplers. A prototype MMIC module has exhibited a band-averaged noise temperature of 41 K from 82 to 100 GHz and a gain of 29 dB at 15 K, which is the state-of-the-art for heterodyne multichip modules.

Sideband-separating MMIC receivers for observation in the 3-mm band

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 15 dB.

Argus: A W-band 16-pixel focal plane array for the Green Bank Telescope

We are building Argus, a 16-pixel square-packed focal plane array that will cover the 75-115.3 GHz frequency range on the Robert C. Byrd Green Bank Telescope (GBT). The primary research area for Argus is the study of star formation within our Galaxy and nearby galaxies. Argus will map key molecules that trace star formation, including carbon monoxide (CO) and hydrogen cyanide (HCN). An additional key science area is astrochemistry, which will be addressed by observing complex molecules in the interstellar medium, and the study of formation of solar systems, which will be addressed by identifying dense pre-stellar cores and by observing comets in our solar system. Argus has a highly scalable architecture and will be a technology path finder for larger arrays. The array is modular in construction, which will allow easy replacement of malfunctioning and poorly performing components.

A W-band heterodyne receiver module prototype for focal plane arrays

A compact W-band heterodyne receiver module populated with MMIC LNAs designed and fabricated using a 35 nm InP HEMT process, and an IQ mixer designed and fabricated using the UMS Schottky diode process is developed as the prototype for Argus, a 16-pixel focal plane array to be deployed on the 100-meter Robert C. Byrd Green Bank Telescope in West Virginia to study star formation. The module has a WR-10 waveguide input. GPPO connectors are used for the LO input and the I and Q IF outputs. The module is tested at both ambient (300 K) and cryogenic (26 K) temperatures. A minimum receiver noise temperature of 27 K was achieved, with less than 45 K noise and more than 20 dB gain in the 85 GHz to 116 GHz band. The band-averaged noise temperature is 34 K and 249 K for a physical temperature of 26 K and 300 K, respectively. The IQ amplitude and phase balance shows image rejection better than 15 dB over 90 percent of the band with constant current operation of both mixers. Image rejection better than 25 dB is measured when optimized currents are used to drive the I and Q mixers.