Robert Hu

An 8-20-GHz wide-band LNA design and the analysis of its input matching mechanism

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.

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.

Wide-band matched LNA design using transistor's intrinsic gate-drain capacitor

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 transistors 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 transistors 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.

Complementary UWB LNA Design Using Asymmetrical Inductive Source Degeneration

This letter proposes a novel LNA design method where the complementary transistor topology is combined with asymmetrical inductive source degeneration to achieve matched input impedance over a wide bandwidth. A 2-10 GHz LNA is designed and fabricated using a commercial 0.18 RF-CMOS process to verify the feasibility of our proposed method. In the intended bandwidth, this LNA has matched input impedance, 20 dB power gain, and 2.4-3.4 dB noise figure, with 25.65 mW power consumption.

Wide-IF-Band CMOS Mixer Design

A wide-IF-band transistor mixer has been designed using a 0.13-¿m RF-CMOS process where its RF frequency is 8.7-17.4 GHz, local oscillator (LO) fixed at 17.4 GHz, and IF up to 8.7 GHz. Proper layout arrangement for the Marchand balun has been discussed and then implemented; the output amplitude and phase imbalance are less than 0.5 dB and 1 ° measured in the RF bandwidth. Related theories for the core mixing circuit are explored extensively and verified through simulation; broad bandwidth of the resistive double-balanced mixer is then confirmed in the IF aspect. The designed mixer has more than 10-dB conversion gain, matched RF, IF, and LO ports, and good port isolation over the intended wide bandwidth. The input-referred P1 dB is -17.5 dBm at 9 GHz and -16 dBm at 13 GHz. The third-order input intercept point is -6 dBm at 9 GHz and -5 dBm at 13 GHz. The noise figure is 7 dB at 9 GHz and 12.6 dB at 13 GHz. The power consumption is 40 mW for this 1.3-mm2 mixer chip.

77–110 GHz 65-nm CMOS Power Amplifier Design

This paper details the development of our millimeter- wave wideband power amplifier design. By treating the power combiner as an impedance transformer which allows different loading impedance to be taken into account, a compact wideband power-combining network can be constructed. With small transmission-line attenuation being sustained and maximum output power easily extracted from the transistors over the 77- 110 GHz frequency range, a power amplifier can then be designed using 65-nm CMOS process to cover the whole W-band. In the on-wafer measurement, the gain is around 18 dB, the output reflection coefficients is below -10 dB, and the output-referred 1 dB compression point can reach 12 dBm at 1.2 V bias condition; when the bias is increased to 2.5 V, a 18 dBm output power is recorded. To our knowledge, this is the first CMOS power amplifier that covers the whole W-band.

SiGe HBT's Small-Signal Pi Modeling

This paper presents the derivation procedure used in determining the parameters in SiGe HBTs small-signal model where the Pi circuit configuration is employed. For both the transistors external base-collector capacitor and its base spreading resistor, new close-form expressions have been derived. Comparisons with existing approaches vindicate the feasibility and effectiveness of our formulations. With the impact of the lossy substrate effectively modeled and the frequency dependency of the transconductance properly addressed, this proposed extraction approach demonstrates accurate results up to 30 GHz with different bias conditions.

On-wafer noise-parameter measurement using wide-band frequency-variation method

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.

A 78

In this letter, a 78 ~ 102 GHz front-end receiver designed in 90 nm CMOS technology is presented. It consists of an ultra-wideband low-noise amplifier, a subharmonic mixer, and an IF buffer. This receiver has a peak gain of 11.8 dB at 94 GHz with the noise figure of 13.4 dB. The measured input-referred 1 dB compression point is -14.5 dBm and the total power dissipation is 18.6 mW. The chip size is 680 × 1020 μm2.

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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 amplifiers noise temperature approaching just a few Kelvins, the postulate used in calculating the cables 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.