Browsing by Author "Hu, R"

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An 8-20-GHz wide-band LNA design and the analysis of its input matching mechanism
(2004-11-01)
Hu, R
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this letter, a wide-band low-noise amplifier (LNA) design is presented with -10 dB input reflection coefficient and 100-K noise temperature over the 8-20-GHz frequency range at room temperature. This LNA can be cooled down in a liquid Helium cryostat to have 10-K noise temperature for the purpose of radio-astronomy application. To achieve its wide-band characteristics, a novel input matching mechanism is proposed, which combines the high-frequency inductive feedback and the low-frequency capacitive feedback. The recognition and comprehensive interpretation of this new input matching mechanism is crucial for future development of ultra-wide-band LNAs.
Analysis of the input noise contribution in the noise temperature measurements
(2005-03-01)
Hu, R
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In measuring the noise temperature of a cryogenic microwave low-noise amplifier (LNA), the noise from the input thermal buffer, i.e., the coaxial cable that connects the noise source to the amplifier, needs to be correctly accounted for. With the amplifier's noise temperature approaching just a few Kelvins, the postulate used in calculating the cable's noise temperature, that the cable is homogeneous and has a linear temperature profile, commands a further inspection. This letter analyzes these assumptions and clarifies the situations in which they hold. To substantiate this Kelvin-level discretion, a LNA is designed and measured.
Investigation of different input-matching mechanisms used in wide-band LNA design
(2005-02-01)
Hu, R
;
Yang, MSC
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper analyzes different input-matching mechanisms used in designing the wide-band amplifiers in general, and the low noise amplifiers (LNA) in particular, and their corresponding noise impact. Among them, the most promising one is the reactive-feedback circuit configuration, which is a combination of high-frequency inductive feedback and low frequency capacitive feedback. In this paper the simulated result that both matched input impedance and low noise temperature T-n can be achieved simultaneously over a wide bandwidth in the single-ended low noise amplifier is proved mathematically and is well interpreted. This understanding of reactive feedback is crucial for the future development of ultra-wide-band low-noise amplifiers.
On-wafer noise-parameter measurement using wide-band frequency-variation method
(2005-07-01)
Hu, R
;
Sang, TH
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, it is demonstrated that the newly proposed wide-band frequency-variation method, where only one set of matched and mismatched noise measurements is used, can efficiently determine the noise parameters of an ultra-sensitive transistor on-wafer at room temperature. Since the experimental setup is similar to that of conventional noise-temperature measurement while no complicated hardware is employed, this new approach is straightforward, yet efficient, and can be easily extended to applications with much higher or broader frequency ranges. Both the measured noise parameters of the post-amplifier stage and the transistor under test will be presented and investigated.
Wide-band matched LNA design using transistor's intrinsic gate-drain capacitor
(2006-03-01)
Hu, R
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents the development of a wide-band amplifier with matched input impedance and low noise temperature over 10-20 GHz. Here, the novel wide-band feedback mechanism provided by the transistor's intrinsic gate-drain capacitor will be analyzed in detail with both the derived input reflection coefficient and noise temperature of the resulting circuit confirmed by their simulated counterparts. It is thus clear why by fine tuning its output RC loading impedance and source inductance, a transistor's input reflection coefficient and noise temperature can be greatly improved over broad bandwidth. To demonstrate the feasibility of this novel approach, a wide-band low-noise amplifier (LNA) is designed and characterized. A bandwidth broadening mechanism using double feedback is also proposed for the future design of matched ultra-wide-band LNA.