This paper demonstrates two designs of extremely low noise amplifiers in the low frequency range of 350 MHz to 1070
MHz. Hybrid microwave integrated circuit is adapted for a low noise design at this low frequency range. Discrete
passive components with high-Q and large values are selected to integrate with the best low noise transistors to optimize
the LNA performance. The first UHF band cryogenic LNA was designed with InP HEMTs in all three stages for Square
Kilometer Array - mid telescope band-1 receiver. This LNA extended the low end frequency to 350 MHz, and achieved
averaging 1.4 Kelvin of a record low noise temperature, more than 47 dB gain, and good input and output return losses <
-10 dB over the broad bandwidth from 350 to 1050 MHz at 15 K. The second UHF band cryogenic LNA was developed
for MeerKAT Array, a precursor of Square Kilometer Array. This LNA was designed with InP HEMT transistor at first
stage to achieve best low noise performance and GaAs HEMTs for second and third stages to replace InP HEMTs and
realize high gain and good amplitude stability at cryogenic temperature. The second LNA achieved a record low noise
temperature of averaging 0.6 Kelvin, more than 45 dB gain, and good input and output return losses ≤ -12 dB over the
wide bandwidth from 580 to 1070 MHz at 15 K.
Phased array feed (PAF) receivers used on radio astronomy telescopes offer the promise of increased fields of view
while maintaining the superlative performance attained with traditional single pixel feeds (SPFs). However, the much
higher noise temperatures of room temperature PAFs compared to cryogenically-cooled SPFs have prevented their
general adoption. Here we describe a conceptual design for a cryogenically cooled 2.8 – 5.18 GHz dual linear
polarization PAF with estimated receiver temperature of 11 K. The cryogenic PAF receiver will comprise a 140 element
Vivaldi antenna array and low-noise amplifiers housed in a 480 mm diameter cylindrical dewar covered with a RF
transparent radome. A broadband two-section coaxial feed is integrated within each metal antenna element to withstand
the cryogenic environment and to provide a 50 ohm impedance for connection to the rest of the receiver. The planned
digital beamformer performs digitization, frequency band selection, beam forming and array covariance matrix
calibration. Coupling to a 15 m offset Gregorian dual-reflector telescope, cryoPAF4 can expect to form 18 overlapping
beams increasing the field of view by a factor of ~8x compared to a single pixel receiver of equal system temperature.
Astronomical surveys are demanding more throughput from telescope receivers. Currently, microwave/millimeter telescopes with mature cryogenic single pixel receivers are upgrading to multi-pixel receivers by replacing the conventional feed horns with phased array feeds (PAFs) to increase the field of view and, thus, imaging speeds. This step in astronomy instrumentation has been taken by only a few research laboratories world-wide and primarily in Lband (0.7-1.5 GHz). We present a K-band (18-26 GHz) 5x5 modular PAF to demonstrate the feasibility of higher frequency receiving arrays. The KPAF system includes a tapered slot antenna array, a cryogenic commercial GaAs MMIC amplifier block, and a mixing stage to down-convert to L band for an existing beamformer. The noise temperature and power budget are outlined. Full antenna S-parameters and far-field beam patterns are simulated and measured using both planar near-field and far-field techniques. Cryogenic and room temperature amplifier noise measurements with varying bias levels are presented.
ALMA Band 1, covering 31-45 GHz, is the lowest signal frequency band of the ALMA telescope and development of
the technology to be used for the front-end cartridge is currently in a research phase. We have made progress on various
key components designed for use in the ALMA Band 1 cartridge, including the orthomode transducer (OMT), low-noise
amplifier (LNA), lens, and down-converting mixer. Since the layout of the ALMA cartridges within the antenna is not
optimized for the lowest band, a dielectric lens is required to avoid blocking other bands. Using a lens necessitates
careful characterization of the dielectric properties controlling focal length and dielectric loss. It is also important to
match the index of refraction of the lens to minimize reflection while still providing equal performance for both linear
polarizations and not introducing any cross-polarization effects. Different anti-reflection techniques will be shown; for
example, a hole array, as an anti-reflection layer, has been used for a vacuum window and measured results are
compared with simulation. A test cryostat has been constructed by adding an extension to a commercial liquid helium
cryostat. Initial sensitivity measurements of a simplified prototype receiver will be given, incorporating an HDPE
window, commercial conical feedhorn, 3-stage LNA, and warm amplification stage. An overview of the system losses,
receiver noise budget, and system alignment tolerances will also be shown. Furthermore, there is interest in either
extending or shifting the existing frequency towards 50 GHz, and the impact on each component will be considered.
The Band 3 receiver, covering the 84-116 GHz frequency band is one of the 10 channels that will be installed on the
Atacama Large Millimeter Array (ALMA). A total of 73 units have to be built in two phases: 8 preproduction and then
65 production units. This paper reports on the assembly, testing and performance of the preproduction series of these
state-of-the-art millimeter receivers.
This paper describes the development of a 3-stage cryogenic low noise InP HEMT amplifier for ALMA Band 3 receivers. A detailed design is given using Hughes 0.1 μm low noise InP HEMTs for producing a low power dissipation amplifier, < 9 mW. The amplifier design uses a hybrid circuit in order to provide the flexibility for optimizing the active devices and passive components. The optimal impedance matching for low noise and low input return loss were obtained by computer aided simulation to achieve 5 K noise temperature, 36 dB gain, flatness ±1 dB and -10 dB input return loss at 12 degrees Kelvin in the 4-9 GHz band. The amplifier will be used as a cold IF preamplifier with a SIS mixer in the Band 3 receivers now being constructed for the Atacama Large Millimetre Array (ALMA).
We have proposed and designed a photonic true-time delay (TTD) steered phased-array antenna system that can work at
high RF frequency with high angular resolution. Several elementary techniques have been studied and developed, including
an optical realization of the Blass matrix based on our substrate-guided wave fanout structure, switching operation of
wideband MSM and PIN photodetectors, and heterodyne RF signal generation. A design for the system demonstration that
has the bandwidth from 18 to 26GHz is reported.
This paper reports our efforts to develop an optical True- Time-Delay line module for Phased Array Antenna applications using optical polymeric waveguides. We first give a brief description of a targeted phased array antenna, having chosen a 16-element sub-array as our demonstration system. Then we address the design considerations of the True-Time- Delay lines pattern based on the sub-array antenna's parameters, including simulations we have done to optimize the building blocks of the pattern: splitters, arcs' curvature, and crossings. Finally, we describe the steps of a modified fabrication process and present the primary result. Our experiment shows that the polyimide-based waveguide has a promising future because it has high fabrication precision and packaging density.
The switching characteristic of wide-band MSM and PIN photodetectors has been studied in theory and experiments. MSM detector has threshold bias voltage to activate its response and so has a better performance than PIN photodetectors when working as a photo-electronic switch. However, our study tells that through a suitable designed bias circuit, the PIN photodetector also can provide a switching operation with considerable performance. Especially for RF photonic signal, the extinction ratio can reach around 30dB. At different bias condition, the gain of PIN can be continually tuned and it has very important application in photonic phased-array antenna system.