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The tumor microenvironment is a highly complex ecosystem of diverse cell types, which shape cancer biology and impact the responsiveness to therapy. Here, we analyze the microenvironment of esophageal squamous cell carcinoma (ESCC) using single-cell transcriptome sequencing in 62,161 cells from blood, adjacent nonmalignant and matched tumor samples from 11 ESCC patients. We uncover heterogeneity in most cell types of the ESCC stroma, particularly in the fibroblast and immune cell compartments. We identify a tumor-specific subset of CST1+ myofibroblasts with prognostic values and potential biological significance. CST1+ myofibroblasts are also highly tumor-specific in other cancer types. Additionally, a subset of antigen-presenting fibroblasts is revealed and validated. Analyses of myeloid and T lymphoid lineages highlight the immunosuppressive nature of the ESCC microenvironment, and identify cancer-specific expression of immune checkpoint inhibitors. This work establishes a rich resource of stromal cell types of the ESCC microenvironment for further understanding of ESCC biology.

In this paper, three kinds of Ka/Ku-band Gilbert mixers are demonstrated using 0.15- [micro]m AlGaAs/InGaAs pseudomorphic high electron mobility transistor technology. Thanks to the semiinsulating GaAs substrate, microwave passive components have a low-loss feature, and polyphase filters work up to higher frequencies. Highly accurate tantalum-nitride thin-film resistors utilized in polyphase filters result in perfect quadrature operation. Therefore, our proposed single-sideband up-converter operates at 15 GHz with a 63-dB sideband rejection ratio, and another 34-GHz in-phase/quadrature (I/Q) subharmonic down-converter reaches Index Terms--Compensation, down-converter, polyphase filter, pseudomorphic HEMT (pHEMT), quadrature, single sideband (SSB), subharmonic, up-converter.

A 5.0-GHz-band monolithic direct-conversion receiver front end employing subharmonic mixers (SHMs) is demonstrated in 0.18-[micro]m CMOS technology. Instead of using transistors as transconductors, the SHMs adopt on-chip 1:4 transformers to achieve voltage gain, and hence, excellent local-oscillator self-mixing suppression and good linearity can be obtained. Additionally, a CMOS-compatible postprocess is used to selectively remove the silicon substrate underneath the inductors and transformers of the receiver front end. While dissipating 43.9 mW from a 1.8-V supply, the micromachined receiver front end exhibits a voltage gain of 28.0 dB, a noise figure of 9.7 dB, a third-order input intercept point of -7.8 dBm at 5.0 GHz, and an input-referred dc offset of--118.0 dBm. The proposed receiver front end is further integrated with analog baseband circuits, a fractionai-N frequency synthesizer, and a serial-to-parallel data converter to accomplish a multioperation-mode receiver. Index Terms--CMOS, direct conversion, front end, localoscillator (LO) self-mixing, quadrature coupler, receivers, subharmonic mixers (SHMs), transformers.

This paper realized a broadband uniplanar phase-inverter rat-race coupler using a standard silicon process, and then analyzed this coupler under a lossy condition. A phase inverter is employed in this coupler, not only to extend the operation bandwidth, but also to generate balanced outputs by providing equal lossy paths, while symmetrical spiral-shaped coplanar striplines (CPSs) are also utilized to shrink the coupler size, as well as to construct a phase inverter in the middle of one of spiral CPSs. The lossy CPS, when designed as a distortionless line, has a real characteristic impedance, and thus, perfect port matching of the coupler can be achieved at the center frequency. The operation frequency of this silicon monolithic rat-race coupler with the size of 0.5 [mm.sup.2] is extremely wide and ranges from 5 to 23 GHz. The dissipated loss, transmission coefficient, and isolation of the ratrace coupler are approximately 5.5, -8, and below -25 dB, respectively. In addition, a wideband Gilbert micromixer with an integrated uniplanar phase-inverter rat-race coupler at the local oscillator port is demonstrated using 0.35- [micro]m SiGe BiCMOS technology. This mixer works from 2.5 to 13 GHz with 12-dB conversion gain, -16-dBm [IP.sub.1 dB], -4-dBm [IIP.sub.3], and 14-dB noise figure. The chip size of the mixer with an integrated coupler is approximately 1.4 mm x 1.4 mm. Index Terms--Downconverter, micromixer, phase inverter, rat-race coupler, SiGe BiCMOS, silicon substrate, transimpedance amplifier, wideband.

This paper discusses and demonstrates the most popular sub-harmonic Gilbert mixers in 2-[micro]m GaInP/GaAs HBT technology. High two local oscillators (2LO)-to-RF isolation is important to alleviate the self-mixing problem of the sub-harmonic mixer. The demonstrated GaInP/GaAs HBT stacked-local oscillator (LO) mixer topology has achieved the best 2LO-to-RF isolation when compared with the previous literature. On the other hand, the leveled-LO sub-harmonic mixers have advantages in terms of the high speed and low dc supply voltage at the cost of much larger LO pumping power. Among all the structures, the bottom-LO sub-harmonic mixer has the lowest current consumption and the simplest circuit structure at the expense of the 2LO-to-RF isolation. Index Terms--DC offset, GaInP/GaAs HBT, Gilbert mixer, self-mixing, sub-harmonic mixer, two local oscillators (2LO)-to-RF isolation. Digital Object Identifier 10.1109/TMTT.2007.895169

A new input matching method making use of shunt-shunt feedback capacitance is introduced. Based on the new input matching method, reconfigurable SiGe low-noise amplifiers (LNAs) by varying shunt-shunt feedback capacitance are proposed. Two approaches are used to vary the shunt-shunt feedback capacitance. One approach is to switch between two different bias currents while the other is to use a series combination of a switch and a capacitor. Miniaturized fully monolithic reconfigurable SiGe LNAs without emitter degenerative inductors were realized by the above two approaches. The reconfigurable SiGe LNA achieved by switching bias currents only occupies a very small area of 355 [micro]m x 155 [micro]m, excluding measurement pads. This LNA achieves an input return losses ([S.sub.11]) of -27.6 dB, a voltage gain ([A.sub.v]) of 19.8 dB, and a noise figure (NF) of 3.18 dB for 2.4-GHz band when biased at a current of 3.8 mA and can be reconfigured to obtain [A.sub.v] = 20.4/20.3 dB, [S.sub.11] =-47.1/-24.6 dB and NF = 3.42/3.21 dB for 5.2/5.7-GHz band when bias current is switched to 3 mA. In addition, a 2.4/4.9/5.2/5.7-GHz reconfigurable SiGe LNAs for WLAN applications, whose variable shunt-shunt feedback capacitance is controlled by a switch and a capacitor, was also realized. Index Terms--BiCMOS, CMOS, low-noise amplifier (LNA), multiband, reconfigurable, SiGe.

A single-ended wideband downconversion Gilbert micromixer is demonstrated in this paper using 0.35-[micro]m SiGe BiCMOS technology. A transimpedance amplifier with resistive feedback is utilized in the IF stage while a broadband Marchand balun is employed to generate wideband differential local oscillator signals. The planar Marchand balun topology employed in this paper can generate truly balanced signals even in the presence of the lossy low-resistivity (~10 [OMEGA] * cm) silicon substrate. A systematic approach to measure the frequency response of each individual stage in a Gilbert mixer is developed in this paper. This single-ended wideband mixer has the conversion gain of 15 dB, I[P.sub.1dB] of -19 dBm, II[P.sub.3] of -7 dBm, and the noise figure of 13 dB. The mixer works from 3.5 to 14.5 GHz. Index Terms--Downconverter, Marchand balun, micromixer, SiGe BiCMOS, silicon substrate, transimpedance amplifier (TIA), wideband.

A general three-port S-parameter de-embedding method using shield-based test structures for microwave on-wafer characterization is presented in this paper. This method does not require any physical equivalent-circuit assumption for the surrounding parasitics of a device-under-test. We use one open and three thru dummy devices to remove the parasitic components connected to the gate, drain, and source terminals of a MOSFET. By shielding the lossy silicon substrate, the cross-coupling from port to port can be significantly mitigated, and thus, the parasitics of probe pads and interconnects at each port can be separately subtracted. The MOS transistor and its corresponding dummy structures fabricated in a 0.18-[micro]m CMOS process were characterized up to 20 GHz. Compared with the two-port cascade-based de-embedding method, the proposed three-port de-embedding procedure can further eliminate the parasitics associated with the dangling leg in the source terminal. The impacts of the accuracy of the de-embedding technique on device modeling and simulation are also discussed. Index Terms--De-embedding, MOSFET, parasitics, scattering parameters.

Drain-induced barrier lowering effects and low-temperature characteristics of p-channel transistors with Si[subscript 1-x]Ge[subscript x] raised source and drain (RSD) are examined. Si[subscript 1-x]Ge[subscript x] device perform better compared to pure Si RSD devices, and improvements become more dramatic as channel length is reduced.