Hao Wu

Bio: Hao Wu is an academic researcher from Broadcom. The author has contributed to research in topics: Noise figure & CMOS. The author has an hindex of 11, co-authored 21 publications receiving 397 citations. Previous affiliations of Hao Wu include University of California, Berkeley & University of California, Los Angeles.

Implicit Common-Mode Resonance in LC Oscillators

Abstract: The performance of a differential LC oscillator can be enhanced by resonating the common mode of the circuit at twice the oscillation frequency. When this technique is correctly employed, Q-degradation due to the triode operation of the differential pair is eliminated and flicker noise is nulled. Until recently, one or more tail inductors have been used to achieve this common-mode resonance. In this paper, we demonstrate that additional inductors are not strictly necessary by showing that common-mode resonance can be obtained using a single tank. We present an NMOS architecture that uses a single differential inductor and a CMOS design that uses a single transformer. Prototypes are presented that achieve figure-of-merits of 192 and 195 dBc/Hz, respectively.

Highly linear receiver front-end with thermal and phase noise cancellation

Abstract: A radio receiver supporting cancellation of thermal and phase noise in a down-converted RF signal. An inbound RF signal and blocking signal are provided directly to a passive mixer for down-conversion into a first baseband signal having data, thermal noise, and reciprocal mixing (RM) noise components. The inbound signals are also provided to a transconductance circuit, the output of which is provided to a second passive mixer for conversion into a current signal having data and blocking signal components, and a RM image. The blocking signal component and the RM image are mixed with a second LO signal, derived from the blocking signal, to produce a RM noise cancellation signal. The data component of the current signal is converted into a second baseband signal having data and thermal noise components. The first baseband signal, second baseband signal and RM noise cancellation signal are then combined through harmonic recombination.

EM Scattering from a Long Dielectric Circular Cylinder

Abstract: A new iterative technique based on the T -matrix approach is proposed for the electromagnetic scattering by dielectric cylinders, in particular cylinders with large aspect ratios. For such cases the conventional T -matrix approach fails. We use hypothetic surfaces to divide a cylinder into a cluster of N identical sub-cylinder, for each the T matrix can be directly calculated. Since any two neighboring sub- cylinder are touching via the division interface, the conventional multi- scatterer equation method is not directly applicable. The coupling among sub-cylinder and boundary conditions at the interfaces are taken care of in our approach. The validity of the proposed method is demonstrated through agreement between theoretical predictions and numerical simulations as well as measurements for scattering from dielectric circular cylinders with finite length. The results clearly demonstrate that the new iterative technique can extend regular T - matrix approach to solve cylindrical cases with large aspect ratio.

25.3 A VCO with implicit common-mode resonance

Abstract: CMOS VCO performance metrics have not improved significantly over the last decade. Indeed, the best VCO Figure of Merit (FOM) currently reported was published by Hegazi back in 2001 [1]. That topology, shown in Fig. 25.3.1(a), employs a second resonant tank at the source terminals of the differential pair that is tuned to twice the LO frequency (F LO ). The additional tank provides a high common-mode impedance at 2xF LO , which prevents the differential pair transistors from conducting in triode and thus prevents the degradation of the oscillator's quality factor (Q). As a consequence, the topology can achieve an oscillator noise factor (F)-defined as the ratio of the total oscillator noise to the noise contributed by the tank- of just below 2, which is equal to the fundamental limit of a cross-coupled LC CMOS oscillator [2]. There are, however, a few drawbacks of Hegazi's VCO: (1) the additional area required for the tail inductor, (2) the routing complexity demanded of the tail inductor, which can degrade its Q and limit its effectiveness, and (3) for oscillators with wide tuning ranges, the need to independently tune the second inductor, which again can degrade its Q. Moreover, it can be shown that the common-mode impedance of the main tank at 2×F LO also has a significant effect on the oscillator's performance, which if not properly modeled can lead to disagreement between simulation and measurement, particularly in terms of the flicker noise corner. To mitigate these issues, this work introduces a new oscillator topology that resonates the common-mode of the circuit at 2xF LO , but does not require an additional inductor.

A Blocker-Tolerant Inductor-Less Wideband Receiver With Phase and Thermal Noise Cancellation

Abstract: A wideband receiver architecture with simultaneous phase and thermal noise cancellation greatly relaxes the traditional trade-offs between noise, out-of-band linearity, LO phase noise and power consumption. The architecture employs thermal noise cancelling and avoids voltage gain at blocker frequencies, and exploits the symmetry of phase noise to cancel the reciprocal mixing products in the presence of either single-tone or modulated blockers. The resulting design in 28 nm CMOS has 2 dB noise figure from 100 MHz to 2.8 GHz. Without using any inductors on-chip including the RF VCO, the receiver's NF is below 14 dB under either a 0 dB CW blocker or a -10 dBm WCDMA blocker.

Method and apparatus for coupling an antenna to a device

Abstract: Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.

Cryo-CMOS Circuits and Systems for Quantum Computing Applications

Abstract: A fault-tolerant quantum computer with millions of quantum bits (qubits) requires massive yet very precise control electronics for the manipulation and readout of individual qubits. CMOS operating at cryogenic temperatures down to 4 K (cryo-CMOS) allows for closer system integration, thus promising a scalable solution to enable future quantum computers. In this paper, a cryogenic control system is proposed, along with the required specifications, for the interface of the classical electronics with the quantum processor. To prove the advantages of such a system, the functionality of key circuit blocks is experimentally demonstrated. The characteristic properties of cryo-CMOS are exploited to design a noise-canceling low-noise amplifier for spin-qubit RF-reflectometry readout and a class-F2,3 digitally controlled oscillator required to manipulate the state of qubits.

Remote distributed antenna system

Abstract: A distributed antenna system is provided that frequency shifts the output of one or more microcells to a 60 GHz or higher frequency range for transmission to a set of distributed antennas. The cellular band outputs of these microcell base station devices are used to modulate a 60 GHz (or higher) carrier wave, yielding a group of subcarriers on the 60 GHz carrier wave. This group will then be transmitted in the air via analog microwave RF unit, after which it can be repeated or radiated to the surrounding area. The repeaters amplify the signal and resend it on the air again toward the next repeater. In places where a microcell is required, the 60 GHz signal is shifted in frequency back to its original frequency (e.g., the 1.9 GHz cellular band) and radiated locally to nearby mobile devices.

Method and apparatus that provides fault tolerance in a communication network

Abstract: Aspects of the subject disclosure may include, for example, a system for detecting a fault in a first wire of a power grid that affects a transmission or reception of electromagnetic waves that transport data and that propagate along a surface of the first wire, selecting a backup communication medium from one or more backup communication mediums according to one or more selection criteria, and redirecting the data to the backup communication medium to circumvent the fault. Other embodiments are disclosed.

Guided-wave transmission device with non-fundamental mode propagation and methods for use therewith

Abstract: Aspects of the subject disclosure may include, for example, a transmission device that includes a transmitter that generates a first electromagnetic wave to convey data. A coupler couples the first electromagnetic wave to a single wire transmission medium having an outer surface, to forming a second electromagnetic wave that is guided to propagate along the outer surface of the single wire transmission medium via at least one guided wave mode that includes an asymmetric or non-fundamental mode having a lower cutoff frequency. A carrier frequency of the second electromagnetic wave is selected to be within a limited range of the lower cutoff frequency, so that a majority of the electric field is concentrated within a distance from the outer surface that is less than half the largest cross sectional dimension of the single wire transmission medium, and/or to reduce propagation loss. Other embodiments are disclosed.