K. Chang

Development of a retrodirective wireless microwave power transmission system

This paper describes the design of a small-scale system for demonstrating retrodirective wireless power transmission. A solid-state phased array transmitter with retrodirective control drives two 5.8 GHz circular-polarized (CP) transmit antenna subarrays that illuminate a remote CP rectenna array. The total power transmitted is about 40 W. A 2.9 GHz pilot beam projected from the rectenna site is received at the transmit site and processed for retrodirective control of the 5.8 GHz transmitter.

A dual polarized circular patch rectifying antenna at 2.45 GHz for microwave power conversion and detection

A novel circular patch rectifying antenna (rectenna) has been developed which converts microwave energy into DC power at 2.45 GHz. Dual polarization is achieved by two orthogonal microstrip feed lines. Rectification is achieved by GaAs Schottky-barrier diodes located on each feed line. A 48% conversion efficiency from microwave power to DC power was achieved. The design was based on a nonlinear circuit analysis.<<ETX>>

New technique to measure transmission line attenuation

A new technique using a quarter-wave open stub resonator was developed to measure a transmission lines attenuation coefficient. Transmission line attenuation was extracted from the Q-factor measurement of the open stub resonator. Equations were derived that relate the stubs two port S-parameters to transmission line attenuation. The new methods benefits include higher accuracy over other methods of attenuation measurement, less area required for the test structure, and easier test structure design. Applications include simple and accurate determination of the transmission lines loss characteristics and effective dielectric constant at very high frequencies. >

Electronically tunable and switchable filters using microstrip ring resonator circuits

Two microstrip ring resonator circuits are described: an electrically switchable filter and a tunable switchable filter, both using p-i-n diodes. In the first circuit, a microstrip ring resonator loaded with two p-i-n diodes is developed as a switchable filter. By replacing one p-i-n diode with a varactor diode, the switchable filter is made electronically tunable. Over 20-dB isolation with 9% tuning bandwidth has been demonstrated. Equivalent circuits have been developed for both circuits. The analysis was based on the transmission-line model including the effects of diode parasitics, coupling gaps, dispersion, and mounting gap capacitance. The experimental results agree very well with the theoretical calculation.<<ETX>>

A self-mixing active antenna for communication and vehicle identification applications

A cavity backed, Gunn diode driven, self-mixing active inverted stripline circular patch antenna has been developed. The active antenna provides good radiation patterns with cross-polarization levels 18 dB below copolarization at boresight. The self-mixing performance shows that the circuit has a 2 dB conversion gain for IFs up to 450 MHz and a double sideband noise figure of 15 dB at 200 MHz. The antenna is suitable for use as a transceiver for short communications links or as a microwave identification transceiver.

A novel nonlinear statistical modeling technique for microwave devices

A novel nonlinear methodology for representing statistical variations of FET Equivalent Circuit Parameters (ECPs) and a new approach to yield estimation are presented. Proposed statistical nonlinear characterization is based on combination of applied multivariate methods with heuristic techniques, while proposed yield estimation method is based on Latin Hypercube Sampling (LHS). Practical examples validate the accuracy and efficiency of the methods.

Coplanar waveguide feed linear tapered slot antenna

The authors present the design and performance of a linear tapered slot antenna with a coplanar waveguide feed. The measured radiation patterns of the antenna are linear with cross polarization levels 12 dB down in both E and H-plane. The return loss is below -20 dB over a bandwidth of 1.55 GHz. The measured gain of the antenna is 7 dBi at 9.2 GHz.<<ETX>>

Directional couplers between doubled-sided substrate microstrip lines using virtually-terminated coupling slots

A new planar multilayer quadrature coupler is proposed. This new multilayer coupler consists of two microstrip lines that are coupled through two virtually terminated narrow slots in a common ground plane. Experimental results are in fairly good agreement with theory. With the advantages of compact size and simple design procedure, this new component should have many applications in multilayer microwave integrated circuits.<<ETX>>

Wideband integrated varactor-tunable active notch antennas and power combiners

A Gunn device in a varactor-tuned slotline coplanar waveguide (CPW) resonator has been integrated with a planar, endfire notch antenna. The varactor provides more than 14% tuning bandwidth centered at 9.6 GHz, with a power output of 14.5+or--0.8 dBm. Wideband tunable quasi-optical power combiners have also been developed using the active elements. The signal spectrum remains clean and very stable with nearly constant power output throughput the electronic tuning range. These results offer a simple, lightweight, low-cost, reproducible, and truly planar active wideband tunable source for many microwave applications.<<ETX>>

Down-Conversion of Microwave Optoelectronic Signals in a GaAs Microstrip Ring Resonator

We report the mixing performance of a GaAs microstrip ring resonator in which a Schottky photodetector is monolithically integrated in a coupling gap. A spectrum of down-conversion between an optically modulated RF signal and an independently applied LO (Local Oscillator) signal is demonstrated and the system conversion loss of RF to IF (Intermediate Frequency) is measured as a function of LO frequency and compared with other data.