Jian-Yu Li

Single-Antenna Doppler Radars Using Self and Mutual Injection Locking for Vital Sign Detection With Random Body Movement Cancellation

This work presents a single-antenna self-injection-locked (SIL) radar to reduce the hardware complexity of continuous-wave (CW) Doppler systems. The theory provides a basis for determining the signal-to-noise spectral density ratio (SNDR) with the effects of clutter. Experimental results agree closely with the theoretical predictions, showing that the clutter does not affect the optimal SNR performance in an SIL radar. A single-antenna SIL radar array is designed to detect vital signs with random body movement cancellation. To this end, a subject is placed between two single-antenna SIL radars to measure the rates of respiration and heartbeat using Doppler shift, and the effects of random movement of the subject are cancelled by wireless mutual injection locking (MIL) of the two radars. In an experiment, a prototype of such a two-radar array with a spacing of 2 m was implemented at 2.4 GHz, providing accurate and reliable cardiopulmonary monitoring of a subject who jogged on a treadmill with random body motion of many centimeters.

A Novel Vital-Sign Sensor Based on a Self-Injection-Locked Oscillator

A novel vital-sign sensor with a self-injection-locked oscillator and a frequency demodulator to reduce system complexity and improve sensitivity is proposed. The theory provides a delta-sigma model to account for the excellent signal-to-noise spectral density ratio in a parametric study of the sensitivity performance. Then, the experiments verify the sensing principle and the predicted performance. Accordingly, a prototype sensor with high sensitivity is realized for noncontact cardiopulmonary monitoring, achieving a long sensing distance without the need for a low-noise amplifier. The sensing distance can grow four times longer by doubling the operating frequency. Furthermore, the sensor using a swept frequency can eliminate the null detection points and the external radio interference. As an experimental result, the sensor, which is placed 4 m away from the subject, can reliably detect the heartbeat signal an the operating frequency of 3.6 GHz and an output power level of 0 dBm.

Design and Linearization of Class-E Power Amplifier for Nonconstant Envelope Modulation

This paper presents design and linearization techniques for a highly efficient, but nonlinear Class-E power amplifier (PA) applied to linear RF transmitters. To achieve maximum efficiency for Class-E PA operating above gigahertz frequencies, the proposed design theory modifies the classic Class-E condition and considers switch-on and switch-off resistances in deriving the analytical solution. For linearization, a digital envelope predistorter (DEP) is used to provide predistorted envelope modulation for the RF-input and supply-voltage signals fed to the Class-E PA. This DEP can successfully compensate for AM/AM and AM/PM distortions such that the Class-E PA, although classified as a switching-mode PA, can act as a linear PA. A cdma2000 1 times transmitter incorporating this Class-E PA and DEP is demonstrated to simultaneously achieve high efficiency and high modulation quality.

Electrical performance improvements on RFICs using bump chip carrier packages as compared to standard small outline packages

The electrical models of Bump Chip Carrier (BCC) packages have been established based on the S-parameter measurement. When compared to the standard Thin Shrink Small Outline Packages (TSSOP), BCCs exhibit much smaller parasitics in the equivalent circuits. In the simulation, the insertion and return losses for an arbitrary pair of package leads connected through an on-die 50-ohm line are calculated against frequency. BCCs also show better loss characteristics than TSSOPs over a wide frequency range. By setting a random variable with Gaussian distribution varied within a certain range for each equivalent circuit element of the packages, the Monte Carlo analysis has been performed to study the package effects on a GaAs Heterojunction Bipolar Transistor (HBT). Again, BCCs cause less decrement of HBTs unity-gain bandwidth than TSSOPs.

An injection-locked detector for concurrent spectrum and vital sign sensing

This paper proposes a concurrent spectrum and vital sign sensor using an injection-locked detector. To achieve this goal, two different sensing mechanisms are involved. One is to employ the injection locking and pulling effects in an oscillator to fast detect the frequency and power of a wireless communication signal. The other is to use a self-injection-locked oscillator to detect Doppler shift for measuring the breathing and heartbeat rate of a target. A prototype system operating in S-band has been implemented to validate the proposed sensor architecture.

Concurrent Vital Sign and Position Sensing of Multiple Individuals Using Self-Injection-Locked Tags and Injection-Locked I/Q Receivers With Arctangent Demodulation

This work presents a wireless system that operates in the 2.4 GHz ISM band for concurrently sensing the vital signs and positions of multiple individuals. Characterized by low complexity and high accuracy, the proposed system consists of two main parts. One is a self-injection-locked (SIL) tag carried by a subject, which emits a sinusoidal frequency-modulated (SFM) signal with vital sign information. The other is a group of injection-locked (IL) I/Q receivers, which performs arctangent demodulation of the SFM signal to obtain the position information without using RF reference signals, and simultaneously extracts the vital sign information of the subject. In the experiment, the system is capable of sensing multiple individuals based on frequency division multiple access (FDMA) technique. Moreover, fidgeting effect on the detection of vital signs has been greatly reduced by a spectral product approach. Accordingly, it is demonstrated that the experimental prototype provides accurate information about the vital signs and positions of different individuals in an indoor environment.

Highly Efficient Multimode RF Transmitter Using the Hybrid Quadrature Polar Modulation Scheme

This research first presents a hybrid quadrature polar modulator to drive the power amplifier (PA) highly efficiently in a wireless RF transmitter required for multi-mode operation. The proposed modulator consists of a quadrature modulator for processing the RF modulated carrier and a class-S modulator for processing the envelope signal. Since both quadrature and class-S modulators deliver signals with envelope variation, the double amplitude modulation distorts the RF modulated signal at the PA output. Therefore, a digital predistorter is required in front of the hybrid quadrature polar modulator for compensation. The use of such predistorted drive signals can help reducing the average DC and input RF drive powers and the output feed-through levels so as to enhance the power added efficiency and adjacent channel power rejection remarkably

Mutual injection-locked SIL sensor array for vital sign detection with random body movement cancellation

This paper presents a self-injection-locked (SIL) sensor array for cancelling the effects of random body movement on the detection of vital signs. To achieve this goal, a subject is seated between two SIL sensors to measure rates of respiration and heartbeat using the Doppler shift, and the effects of random movements by the subject are cancelled by wireless mutual injection locking (MIL) of the two sensors. In the experiments, a prototype for such a two-sensor array with a spacing of 2 m was implemented at 2.4 GHz, providing accurate and reliable cardiopulmonary monitoring of a subject who exhibited random body motions of several centimeters.

Envelope Following-Based RF Transmitters Using Switching-Mode Power Amplifiers

This research presents a high-efficiency linear radio frequency transmitter applying the envelope-following technique to a switching-mode power amplifier. The use of predistorted envelope and quadrature-modulated signals can linearize the nonlinear behavior with fairly high average efficiency. The experimental results show that the proposed transmitter can deliver a 1.9-GHz CDMA2000 1times signal with high adjacent channel power ratio, low error vector magnitude, and high power added efficiency over a wide range of modulated output power

High efficiency dual-mode RF transmitter using envelope-tracking dual-band Class-E power amplifier for W-CDMA/WiMAX systems

This paper presents design and linearization techniques for a highly efficient but nonlinear Class-E power amplifier (PA) applied to a dual-mode RF transmitter for W0CDMA/WiMAX systems. At first, a Class-E PA design is carried out for dual-band operation based on the proposed modified Class-E condition. Then, the envelope tracking and digital predistortion techniques are applied to linearize the Class-E PA by improving the PA AM/AM and AM/PM distortions. Consequently, the designed Class-E PA, although classified as a switching-mode PA, can act as a linear PA for diverse high peak-to-average-power-ratio (PAPR) wireless systems. The experimental results show that a quadrature modulation transmitter incorporating the presented envelope-tracking dual-band Class-E PA can simultaneously achieve high average efficiency and adjacent channel power rejection for 1.95 GHz W-CDMA and 2.6 GHz WiMAX applications.