88 research outputs found
System-level design and RF front-end implementation for a 3-10ghz multiband-ofdm ultrawideband receiver and built-in testing techniques for analog and rf integrated circuits
This work consists of two main parts: a) Design of a 3-10GHz UltraWideBand
(UWB) Receiver and b) Built-In Testing Techniques (BIT) for Analog and RF circuits.
The MultiBand OFDM (MB-OFDM) proposal for UWB communications has
received significant attention for the implementation of very high data rate (up to
480Mb/s) wireless devices. A wideband LNA with a tunable notch filter, a downconversion
quadrature mixer, and the overall radio system-level design are proposed for
an 11-band 3.4-10.3GHz direct conversion receiver for MB-OFDM UWB implemented
in a 0.25mm BiCMOS process. The packaged IC includes an RF front-end with
interference rejection at 5.25GHz, a frequency synthesizer generating 11 carrier tones in
quadrature with fast hopping, and a linear phase baseband section with 42dB of gain
programmability. The receiver IC mounted on a FR-4 substrate provides a maximum
gain of 67-78dB and NF of 5-10dB across all bands while consuming 114mA from a
2.5V supply.
Two BIT techniques for analog and RF circuits are developed. The goal is to reduce
the test cost by reducing the use of analog instrumentation. An integrated frequency response characterization system with a digital interface is proposed to test the
magnitude and phase responses at different nodes of an analog circuit. A complete
prototype in CMOS 0.35mm technology employs only 0.3mm2 of area. Its operation is
demonstrated by performing frequency response measurements in a range of 1 to
130MHz on 2 analog filters integrated on the same chip. A very compact CMOS RF
RMS Detector and a methodology for its use in the built-in measurement of the gain and
1dB compression point of RF circuits are proposed to address the problem of on-chip
testing at RF frequencies. The proposed device generates a DC voltage proportional to
the RMS voltage amplitude of an RF signal. A design in CMOS 0.35mm technology
presents and input capacitance <15fF and occupies and area of 0.03mm2. The application
of these two techniques in combination with a loop-back test architecture significantly
enhances the testability of a wireless transceiver system
Dual Gate Graphene FETs with fT of 50 GHz
A dual-gate graphene field-effect transistors is presented, which shows
improved RF performance by reducing the access resistance using electrostatic
doping. With a carrier mobility of 2700 cm2/Vs, a cutoff frequency of 50 GHz is
demonstrated in a 350-nm gate length device. This fT value is the highest
frequency reported to date for any graphene transistor, and it also exceeds
that of Si MOSFETs at the same gate length, illustrating the potential of
graphene for RF applications
Operation of Graphene Transistors at GHz Frequencies
Top-gated graphene transistors operating at high frequencies (GHz) have been
fabricated and their characteristics analyzed. The measured intrinsic current
gain shows an ideal 1/f frequency dependence, indicating an FET-like behavior
for graphene transistors. The cutoff frequency fT is found to be proportional
to the dc transconductance gm of the device. The peak fT increases with a
reduced gate length, and fT as high as 26 GHz is measured for a graphene
transistor with a gate length of 150 nm. The work represents a significant step
towards the realization of graphene-based electronics for high-frequency
applications
Ultrafast graphene photodetector
The electronic properties of graphene are unique and are attracting increased
attention to this novel 2-dimensional system. Its photonic properties are not
less impressive. For example, this single atomic layer absorbs through direct
interband transitions a considerable fraction of the light (~2.3%) over a very
a broad wavelength range. However, while applications in electronics are
vigorously being pursued, photonic applications have not attracted as much
attention. Here, we report on ultrafast photocurrent response measurements in
graphene (single and few-layers) field-effect-transistors (FETs) up to 40 GHz
light intensity modulation frequencies, using a 1.55 micron excitation laser.
No photoresponse degradation is observable up to the highest measured
frequency, demonstrating the feasibility and unique benefits of using graphene
in photonics. Further analysis suggests that the intrinsic bandwidth of such
graphene FET based photodetectors may exceed 500 GHz. Most notably, the
generation and transport of the photo-carriers in such graphene photodetectors
are fundamentally different from those in currently known semiconductor
photodetectors, leading to a remarkably high bandwidth, zero source-drain bias
(hence zero dark current) operation, and good internal quantum efficiency.Comment: 25 pages, 3 figure
CULTURA Y ACTIVACIÓN FÍSICA I.
GUÍA DIDÁCTICA / PLANEACIÓN DIDÁCTICA (NMS
Bifocal dual reflectarray with curved main surface
This paper presents a novel approach to synthesizing curved reflectarrays using Geometrical Optics (GO). It introduces the concepts of virtual normal and path length shift, which enable a vector-based formulation of the problem that can be solved using ray tracing techniques. The formulation is applied for the design of two different versions of a Dual Bifocal Reflectarray with a parabolic main surface and a flat subreflectarray. The first version aims to enhance the performance of the multibeam antenna by providing a focal ring located at the feed cluster plane. The second version focuses on improving the scanning characteristics of the antenna in the horizontal plane by incorporating two foci. The synthesis procedure yields samples of the path length shift or its derivatives. To reconstruct the phase distribution, an interpolation scheme is employed and described in this paper. Numerical results are presented for both the focal-ring and two-foci configurations, demonstrating the feasibility of this solution for multibeam or scanning satellite antennas operating in the Ka.European Space Research and Technology Centre | Ref. 4000117113/16/NL/AFMinisterio de Economía y Competitividad | Ref. PDC2021-120959-C21/C22Ministerio de Ciencia e Innovación | Ref. RYC2021-033593-IXunta de Galicia | Ref. GRC-ED431C-2019/2
PLANEACIÓN DIDÁCTICA GENERAL DE LA ASIGNATURA: ARITMÉTICA Y LENGUAJE MATEMÁTICO 2017B
GUÍA DIDÁCTICA / PLANEACIÓN DIDÁCTICA (NMS
PLANEACIÓN DIDÁCTICA GENERAL DE LA ASIGNATURA: TRIGONOMETRÍA 2017- B
GUÍA DIDÁCTICA / PLANEACIÓN DIDÁCTICA (NMS
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