Yi-Cheng Lin

Bio: Yi-Cheng Lin is an academic researcher from National Taiwan University. The author has contributed to research in topics: Antenna measurement & Antenna (radio). The author has an hindex of 20, co-authored 79 publications receiving 2126 citations. Previous affiliations of Yi-Cheng Lin include University of Michigan & Qualcomm.

Compact Ultrawideband Rectangular Aperture Antenna and Band-Notched Designs

Abstract: A simple and compact ultrawideband (UWB) aperture antenna with extended band-notched designs is presented. The antenna consists of a rectangular aperture on a printed circuit board ground plane and a T-shaped exciting stub. The proposed planar coplanar waveguide fed antenna is easy to be integrated with radio-frequency/microwave circuitry for low manufacturing cost. The antenna is successfully designed, implemented, and measured. A compact aperture area of 13 times23mm2 is obtained with promising performances, including broadband matched impedance, stable radiation patterns, and constant group delay. The correlation between the mode-based field distributions and radiation patterns is discussed. Extended from the proposed antenna, three advanced band-notched (5-6 GHz) designs are also presented as a desirable feature for UWB applications

Estimation of forest biophysical characteristics in Northern Michigan with SIR-C/X-SAR

Abstract: A three-step process is presented for estimation of forest biophysical properties from orbital polarimetric SAR data. Simple direct retrieval of total aboveground biomass is shown to be ill-posed unless the effects of forest structure are explicitly taken into account. The process first involves classification by (1) using SAR data to classify terrain on the basis of structural categories or (2) a priori classification of vegetation type on some other basis. Next, polarimetric SAR data at L- and C-bands are used to estimate basal area, height and dry crown biomass for forested areas. The estimation algorithms are empirically determined and are specific to each structural class. The last step uses a simple biophysical model to combine the estimates of basal area and height with ancillary information on trunk taper factor and wood density to estimate trunk biomass. Total biomass is estimated as the sum of crown and trunk biomass. The methodology is tested using SIR-C data obtained from the Raco Supersite in Northern Michigan on Apr. 15, 1994. This site is located at the ecotone between the boreal forest and northern temperate forests, and includes forest communities common to both. The results show that for the forest communities examined, biophysical attributes can be estimated with relatively small rms errors: (1) height (0-23 m) with rms error of 2.4 m, (2) basal area (0-72 m/sup 2//ha) with rms error of 3.5 m/sup 2//ha, (3) dry trunk biomass (0-19 kg/m/sup 2/) with rms error of 1.1 kg/m/sup 2/, (4) dry crown biomass (0-6 kg/m/sup 2/) with rms error of 0.5 kg/m/sup 2/, and (5) total aboveground biomass (0-25 kg/m/sup 2/) with rms error of 1.4 kg/m/sup 2/. The addition of X-SAR data to SIR-C was found to yield substantial further improvement in estimates of crown biomass in particular. However, due to a small sample size resulting from antenna misalignment between SIR-C and X-SAR, the statistical significance of this improvement cannot be reliably established until further data are analyzed. Finally, the results reported are for a small subset of the data acquired by SIR-C/X-SAR. >

A Monte Carlo coherent scattering model for forest canopies using fractal-generated trees

Abstract: A coherent scattering model for tree canopies based on a Monte Carlo simulation of scattering from fractal-generated trees is developed and verified. In contrast to incoherent models, the present model calculates the coherent backscatter from forest canopies composed of realistic tree structures, where the relative phase information from individual scatterers is preserved. Computer generation of tree architectures faithful to the real stand is achieved by employing fractal concepts and Lindenmayer systems as well as incorporating the in situ measured data. The electromagnetic scattering problem is treated by considering the tree structure as a cluster of scatterers composed of cylinders (trunks and branches) and disks (leaves) above an arbitrary tilted plane (ground). Using the single scattering approximation, the total scattered field is obtained from the coherent addition of the individual scattering from each scatterer illuminated by a mean field. Foldy's approximation is invoked to calculate the mean field within the forest canopy that is modeled as a multilayer inhomogeneous medium. Backscatter statistics are acquired via a Monte Carlo simulation over a large number of realizations. The accuracy of the model is verified using the measured data acquired by a multifrequency and multipolarization synthetic aperture radar (SAR) [Spaceshuttle Imaging Radar-C (SIR-C)] from a maple stand at many incidence angles. A sensitivity analysis shows that the ground tilt angle and the tree structure may significantly affect the polarimetric radar response, especially at lower frequencies.

Dual-Polarized Quasi Yagi–Uda Antennas With Endfire Radiation for Millimeter-Wave MIMO Terminals

Abstract: This paper presents a novel design of compact dual-polarized multi-input and multi-output (MIMO) antennas with endfire radiation for millimeter-wave wireless applications. The low-cost printed circuit board process serves as the basis for the design, fabrication, and measurement of the proposed dual-polarized quasi Yagi–Uda antennas. Addressing the potential antenna locations in a mobile terminal, this paper investigates both the corner and the lateral design of antenna modules. Each design incorporates dual-port dual-polarized antennas co-located in a compact area. The lateral design is further extended to a linear $1 \times 4$ array for high-gain and phased-scanning operation. Experimental results show that the proposed compact dual-polarized quasi Yagi–Uda antennas are very suitable for MIM terminals of next-generation (5G) mobile communications.

60-GHz Four-Element Phased-Array Transmit/Receive System-in-Package Using Phase Compensation Techniques in 65-nm Flip-Chip CMOS Process

Abstract: AThe 60-GHz four-element phased-array transmit/receive (TX/RX) system-in-package antenna modules with phase-compensated techniques in 65-nm CMOS technology are presented. The design is based on the all-RF architecture with 4-bit RF switched LC phase shifters, phase compensated variable gain amplifier (VGA), 4:1 Wilkinson power combining/dividing network, variable-gain low-noise amplifier, power amplifier, 6-bit unary digital-to-analog converter, bias circuit, electrostatic discharge protection, and digital control interface (DCI). The 2 × 2 TX/RX phased arrays have been packaged with four antennas in low-temperature co-fired ceramic modules through flip-chip bonding and underfill process, and phased-array beam steering have been demonstrated. The entire beam-steering functions are digitally controllable, and individual registers are integrated at each front-end to enable beam steering through the DCI. The four-element TX array results in an output of 5 dBm per channel. The four-element RX array results in an average gain of 25 dB per channel. The four-element array consumes 400 mW in TX and 180 mW in RX and occupies an area of 3.74 mm2 in the TX integrated circuit (IC) and 4.18 mm2 in the RX IC. The beam-steering measurement results show acceptable agreement of the synthesized and measured array pattern.

An Overview of Signal Processing Techniques for Millimeter Wave MIMO Systems

Abstract: Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.

The potential and challenge of remote sensing‐based biomass estimation

Abstract: Remotely sensed data have become the primary source for biomass estimation. A summary of previous research on remote sensing‐based biomass estimation approaches and a discussion of existing issues influencing biomass estimation are valuable for further improving biomass estimation performance. The literature review has demonstrated that biomass estimation remains a challenging task, especially in those study areas with complex forest stand structures and environmental conditions. Either optical sensor data or radar data are more suitable for forest sites with relatively simple forest stand structure than the sites with complex biophysical environments. A combination of spectral responses and image textures improves biomass estimation performance. More research is needed to focus on the integration of optical and radar data, the use of multi‐source data, and the selection of suitable variables and algorithms for biomass estimation at different scales. Understanding and identifying major uncertainties cause...

Polarimetric SAR interferometry

Abstract: The authors examine the role of polarimetry in synthetic aperture radar (SAR) interferometry. They first propose a general formulation for vector wave interferometry that includes conventional scalar interferometry as a special case. Then, they show how polarimetric basis transformations can be introduced into SAR interferometry and applied to form interferograms between all possible linear combinations of polarization states. This allows them to reveal the strong polarization dependency of the interferometric coherence. They then solve the coherence optimization problem involving maximization of interferometric coherence and formulate a new coherent decomposition for polarimetric SAR interferometry that allows the separation of the effective phase centers of different scattering mechanisms. A simplified stochastic scattering model for an elevated forest canopy is introduced to demonstrate the effectiveness of the proposed algorithms. In this way, they demonstrate the importance of wave polarization for the physical interpretation of SAR interferograms. They investigate the potential of polarimetric SAR interferometry using results from the evaluation of fully polarimetric interferometric shuttle imaging radar (SIR)-C/X-SAR data collected during October 8-9, 1994, over the SE Baikal Lake Selenga delta region of Buriatia, Southeast Siberia, Russia.

Dielectric Resonator Antennas

Abstract: Linearly and circularly polarized conformal strip-fed dielectric resonator antennas (DRAs) are studied in this article. In the latter case, a parasitic patch is used to excite a nearly degenerate mode. The hemispherical DRA, excited in its fundamental broadside TE111 mode, is used for the demonstration. In the analysis, the mode-matching method is used to obtain the Green's functions, whereas the method of moments is used to solve for the unknown strip currents. In order to solve the singularity problem of the Green's functions, a recurrence technique is used to evaluate the impedance integrals. This greatly increases the numerical efficiency. Measurements were carried out to verify the calculations, with good results. Keywords: circularly polarized antenna; dielectric antennas; mode-matching methods; moment methods; parasitic antennas; resonance

Polarimetric SAR interferometry

Abstract: In this paper, we examine the role of polarimetry in synthetic aperture radar (SAR) interferometry. We first propose a general formulation for vector wave interferometry that includes conventional scalar interferometry as a special case. Then, we show how polarimetric basis transformations can be introduced into SAR interferometry and applied to form interferograms between all possible linear combinations of polarization states. This allows us to reveal the strong polarization dependency of the interferometric coherence. We then solve the coherence optimization problem involving maximization of interferometric coherence and formulate a new coherent decomposition for polarimetric SAR interferometry that allows the separation of the effective phase centers of different scattering mechanisms. A simplified stochastic scattering model for an elevated forest canopy is introduced to demonstrate the effectiveness of the proposed algorithms. In this way, we demonstrate the importance of wave polarization for the physical interpretation of SAR interferograms. We investigate the potential of polarimetric SAR interferometry using results from the evaluation of fully polarimetric interferometric shuttle imaging radar (SIR)-C/X-SAR data collected during October 8-9, 1994, over the SE Baikal Lake Selenga delta region of Buriatia, Southeast Siberia, Russia.