Recently, it was reported that reduction in serum adiponectin levels is correlated with the incidence of breast cancer. As an effort to explain this, we screened various human breast cancer cell lines to identify those in which proliferation is directly controlled by adiponectin. Among the five tested cell lines, proliferation of MDA-MB-231 cancer cell was significantly suppressed by adiponectin within the range of physiological concentration. Furthermore, prolonged adiponectin treatment caused cell growth arrest and even apoptosis of MDA-MB-231. This result is the first to show that adiponectin can directly control cancer cell growth and provides a rationale for the theory that reduction in plasma adiponectin levels could be a risk factor for breast cancer.
A 300 GHz integrated heterodyne receiver and transmitter for wideband communication and imaging applications have been developed in a 250 nm InP double-heterojunction bipolar transistor (DHBT) process. The receiver integrates a 300 GHz RF amplifier with a balun, a down-conversion mixer with an IF amplifier, and a local oscillator, all on a single chip. The transmitter is composed of the identical circuit blocks of RF amplifier and oscillator in addition to an up-conversion mixer. Compared to previous integrated receivers and transmitters reported at above 200 GHz, the proposed work includes the on-chip local oscillator and mixers operating at a fundamental mode. This simplifies the system architecture, thus not only reducing the chip area and DC consumption but also improving the RF performance such as high conversion gain, low spurious levels, and low noise figure. The receiver exhibits a peak conversion gain of 26 dB at 298 GHz, 3-dB bandwidth of 20 GHz, and noise figure of 12.0-16.3 dB at IF frequency from 1.1 to 7.7 GHz. The transmitter exhibits peak conversion gain of 25 dB, 3 dB bandwidth of 18 GHz, and output power of 2.3 dBm. The DC power consumption of the receiver and transmitter are 482 and 452 mW, respectively.Index Terms-Fundamental local oscillator, fundamental mixer, heterodyne receiver, heterodyne transmitter, millimeter-wave amplifier, terahertz (THz) monolithic integrated circuit.
Two fundamental-mode oscillators operating around 300 GHz, a fixed-frequency oscillator and a voltage-controlled oscillator (VCO), have been developed in this work based on a 250-nm InP heterojunction bipolar transistor (HBT) technology. Both oscillators adopted the common-base configuration for the cross-coupled oscillator core, providing higher oscillation frequency compared to the conventional common-emitter cross-coupled topology. The fabricated fixed-frequency oscillator and the VCO exhibited oscillation frequency of 305.8 GHz and 298.1-316.1 GHz (18-GHz tuning range) at dc power dissipation of 87.4 and 88.1 mW, respectively. The phase noise of the fixed-frequency oscillator was measured to be dBc/Hz at 10 MHz offset. The peak output power of 5.3 dBm (3.8% dc-to-RF efficiency) and 4.7 dBm (3.2% dc-to-RF efficiency) were respectively achieved for the two oscillators, which are the highest reported power for a transistor-based single oscillator beyond 200 GHz.
Index Terms-Frequency control, heterojunction bipolar transistors (HBT), voltage-controlled oscillators (VCO).
0018-9480
An overview of the solid-state electronic approaches for THz sources and detectors aiming at THz imaging is presented in this review paper. Various diode-and transistor-based THz sources are compared for their operation principles and the performances comparison is made based on the literature available at this moment.Similarly, diode-and transistor-based detectors are compared for their operation and performance. This paper is expected to provide a snap shot of current status of the solid-state THz electronics, serving to help those who want to get an initial idea of this field.
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