Design of Cryogenic SiGe Low-Noise Amplifiers

This paper describes a method for designing cryogenic silicon-germanium (SiGe) transistor low-noise amplifiers and reports record microwave noise temperature, i.e., 2 K, measured at the module connector interface with a 50-Ω generator. A theory for the relevant noise sources in the transistor is derived from first principles to give the minimum possible noise temperature and optimum generator impedance in terms of dc measured current gain and transconductance. These measured dc quantities are then reported for an IBM SiGe BiCMOS-8HP transistor at temperatures from 295 to 15 K. The measured and modeled noise and gain for both a single- and two-transistor cascode amplifier in the 0.2-3-GHz range are then presented. The noise model is then combined with the transistor equivalent-circuit elements in a circuit simulator and the noise in the frequency range up to 20 GHz is compared with that of a typical InP HEMT

The eleven antenna: a compact low-profile decade bandwidth dual polarized feed for reflector antennas

A novel dual polarized ultrawide-band (UWB) feed with a decade bandwidth is presented for use in both single and dual reflector antennas. The feed has nearly constant beam width and 11 dBi directivity over at least a decade bandwidth. The feed gives an aperture efficiency of the reflector of 66% or better over a decade bandwidth when the subtended angle toward the sub or main reflector is about 53°, and an overall efficiency better than 47% including mismatch. The return loss is better than 5 dB over a decade bandwidth. The calculated results have been verified with measurements on a linearly polarized lab model. The feed has no balun as it is intended to be integrated with an active 180° balun and receiver. The feed is referred to as the Eleven antenna because its basic configuration is two parallel dipoles 0.5 wavelengths apart and because it can be used over more than a decade bandwidth with 11 dBi directivity. We also believe that 11 dB return loss is achievable in the near future

Matched wideband low-noise amplifiers for radio astronomy

Two packaged low noise amplifiers for the 0.3–4 GHz frequency range are described. The amplifiers can be operated at temperatures of 300–4 K and achieve noise temperatures in the 5 K range (<0.1 dB noise figure) at 15 K physical temperature. One amplifier utilizes commercially available, plastic-packaged SiGe transistors for first and second stages; the second amplifier is identical except it utilizes an experimental chip transistor as the first stage. Both amplifiers use resistive feedback to provide input reflection coefficient S11<−10 dB over a decade bandwidth with gain over 30 dB. The amplifiers can be used as rf amplifiers in very low noise radio astronomy systems or as i.f. amplifiers following superconducting mixers operating in the millimeter and submillimeter frequency range

A novel wide-band noise-parameter measurement method and its cryogenic application

The concept of using a long mismatched transmission line to measure noise parameters has been known for some time. However, it has been limited to narrow-bandwidth applications, and a wide-band extension has never been reported. In order to measure the cryogenic noise parameters of a wide-band low-noise amplifier (LNA), a wide-band frequency-variation method is proposed. In this method, the four noise parameters at each frequency are derived numerically from a set of matched and mismatched noise temperatures measured within a surrounding frequency-sampling window. By scanning this frequency-sampling window, noise parameters over a wide frequency range can be obtained. Since this approach can be easily incorporated into existing noise measurement systems, a tuner is not required, and the technique can be applied to a cryogenic amplifier. This paper details the theory, implementation, and verification of this new method. The measured noise parameters of a cryogenic wide-band LNA are presented

A millimeter-wave perpendicular coax-to-microstrip transition

A novel transition from coaxial cable to microstrip is presented in which the coax connector is perpendicular to the substrate of the printed circuit. Such a right-angle transition has practical advantages over more common end-launch geometries in some situations. The design is compact, easy to fabricate, and provides repeatable performance of better than 14 dB return loss and 0.4 dB insertion loss from DC to 40 GHz

A W-band monolithic medium power amplifier

This paper summarizes the design and measured performance of a MMIC power amplifier for W-band. The chip was fabricated on a 50 µm GaAs substrate using 0.1 µm AlGaAs/InGaAs/GaAs pseudomorphic-HEMT technology. Measurements show that it has small-signal gain of 19±1 dB from 72 to 95 GHz. During scalar measurements with moderate heat-sinking, the chip delivered more than 100 mW between 75 and 93 GHz, with a corresponding large signal gain of 11 dB. Such an amplifier is widely useful in millimeter-wave applications requiring moderately high power over broad frequency ranges, including emerging wireless communication systems in W-band

Experimental cryogenic modeling and noise of SiGe HBTs

SiGe devices are an exciting contender for extremely low noise, cryogenically cooled amplifiers. This paper begins with a procedure for extracting a simple equivalent circuit model capable of accurately describing SiGe HBT devices. Next, small-signal modeling results obtained for a 3×0.12×18um^2 SiGe HBT at 15, 40, 77, 120, 200, and 300K are presented along with discussion of performance enhancements due to cooling of the device. Finally, the modeled noise performance is presented as a function of temperature and frequency using the concept of minimum cascaded noise temperature, a figure of merit which incorporates both noise temperature and gain

A 0.1–5 GHz Cryogenic SiGe MMIC LNA

In this letter, the design and measurement of the first SiGe integrated-circuit LNA specifically designed for operation at cryogenic temperatures is presented. At room temperature, the circuit provides greater than 25.8 dB of gain with an average noise temperature (T_e) of 76 K (NF = 1 dB) and S11 of -9 dB for frequencies in the 0.1-5 GHz band. At 15 K, the amplifier has greater than 29.6 dB of gain with an average Te of 4.3 K and S11 of -14.6 dB for frequencies in the 0.1-5 GHz range. To the authors' knowledge, this is the lowest noise ever reported for a silicon integrated circuit operating in the low microwave range and the first matched wideband cryogenic integrated circuit LNA that covers frequencies as low as 0.1 GHz

A 0.5-20GHz quadrature downconverter

A quadrature downconverter with 4GHz IF bandwidth and working over the 0.5–20GHz RF frequency range has been designed, fabricated, and tested. The downconverter uses a frequency doubling and dividing scheme to generate quadrature local oscillator signals from 0.5–17GHz and a pair of Gilbert-cell mixers to perform downconversion. When the IF outputs are combined with a commercial quadrature hybrid, the mixer achieves an image rejection ratio greater than 35dB over the entire band with no on-chip calibration or tuning. The active die area is approximately 0.5 x 1 mm^2