Kyoung Yang

Electrooptic mapping and finite-element modeling of the near-field pattern of a microstrip patch antenna

A comprehensive electrooptic field-mapping technique is applied to the characterization of near-field radiation patterns above a microstrip patch antenna. The amplitude and phase maps of three orthogonal electric-field components, measured using electrooptic crystals above the patch, also have revealed the transition from the near field to the far field of the radiation pattern. In addition, experimental results have been compared with a finite-element method (FEM) simulation. The measurememts show superior results to the FEM simulation, especially in terms of spatial resolution and data acquisition times. Furthermore, the scattering parameter S/sub 11/ for the patch antenna has been calculated from the electrooptic measurement results of standing waves on the feeding line and compared with results from a conventional network analyzer.

Electrooptic mapping of near-field distributions in integrated microwave circuits

A field mapping system based on external electrooptic sampling has been developed in order to determine the vectorial components of the electric near-field distribution within microwave integrated circuits. The capabilities of the setup are demonstrated by two-dimensional measurements of normal and tangential fields in a coplanar microwave distribution network at frequencies up to 15 GHz. Results obtained on a functioning power-distribution network, as well as on two nonfunctioning networks, show the ability of the technique to interrogate internal circuit operation and to isolate faults through investigation of the field distributions.

Active-amplifier-array diagnostics using high-resolution electrooptic field mapping

Several Ka-band spatial-amplifier power combiners and their free-space feeds were characterized using a high-resolution extreme-near-field electrooptic measurement technique. The two-dimensional electric-field amplitude and phase maps obtained from several arrays are presented. The usefulness of the technique for diagnostic purposes during the design and prototyping stages of the active arrays is discussed. In particular, the electrooptic maps were shown to be valuable for making improvements in the bias line design in one case, and for isolating faulty unit cells in another case.

Simultaneous measurements of electric and thermal fields utilizing an electrooptic semiconductor probe

A method to simultaneously measure electric and thermal fields with a single probe is presented in this paper. The Pockels effect is employed within a gallium-arsenide probe to measure electric fields, and the effect of photon absorption due to bandtail states in the semiconductor is used to determine temperature. The measured optical power is found to be inversely related to temperature, in agreement with theory, and experimental results demonstrate a temperature sensitivity of 0.31 /spl mu/W//spl deg/C at 25/spl deg/C and an accuracy of /spl plusmn/0.5/spl deg/C between 20/spl deg/C-60/spl deg/C. The minimum detectable electric field is 1.24/spl plusmn/0.06 V/m using a 300-ms electrical bandwidth. Temporal phase stability of /spl plusmn/3/spl deg//h is achieved through the implementation of a system phase reference channel. The invasiveness of the probe is quantified by examining the change in the characteristic impedance and capacitance per unit length of a planar transmission line. Measured and simulated data show that the effect is equivalent to a lumped shunt capacitance on the order of a few femtofarads. The examination of a monolithic microwave integrated circuit in an X-band quasi-optical power-combining array and the calibration of electric-field data that was corrupted by temperature-dependent effects inherent to the electrooptic probe demonstrate the capability of this combined electrothermal measurement technique.

Global coupled EM-electrical-thermal simulation and experimental validation for a spatial power combining MMIC array

The first fully coupled electromagnetic-electro-thermal global simulation of a large microwave subsystem, here a whole spatial power combining MMIC array, is described. The modeling effort is supported by parallel developments in electro-optic and thermal measurement. The CAD tools and experimental characterisation described, provide a unique capability for the design of quasi-optical systems and for the exploration of the fundamental physics of spatial power combining devices.

Integrated electro-thermal probe

A method to simultaneously measure electric and thermal fields with a single probe is presented. The probe material is gallium arsenide with the Pockels effect employed to measure electric fields and the effect of photon absorption due to bandtail states used to determine temperature. Measured optical power versus temperature is inversely related and is shown to agree with theory. Experimental results demonstrate a sensitivity of 0.31 /spl mu/W//spl deg/C at 25/spl deg/C and an accuracy of /spl plusmn/0.5/spl deg/C between 20/spl deg/C and 60/spl deg/C. The magnitude of the electric field is obtained with a normalized standard deviation of 1.3%. The technique is applied to the combined electro-thermal examination of an MMIC in a quasi-optical power-combining array and the calibration of electric field data that was corrupted by temperature dependent effects inherent to the electro-optic probe.

Electro-optic field-mapping as a diagnostic tool for microwave circuits and antenna arrays

The effectiveness of an optical-fiber-mounted electro-optic probe as a scanning electric-field-mapping tool is demonstrated in diagnostic measurements on microwave and millimeter-wave circuits, antennas, and arrays. A combined electric-field and thermal-imaging capability is also discussed.

Near-field microwave diagnostics with nonlinear-optical sensors

The concept and implementation of a near-field microwave measurement system that relies on the Pockels effect in fiber-coupled, semi-insulating GaAs probes to acquire polarization-sensitive maps of electric-field patterns in close proximity to antenna arrays, integrated circuits, and packaged components, is presented. The evolution of the electro-optic field-mapping technique, which has subsequently addressed magnetic-field characterization via magneto-optic sensing and temperature measurement through semiconductor band-gap modulation, will also be discussed. The use of emerging materials, such as diluted magnetic semiconductors, is also considered.

Watt-Level Ka-Band Quasi-Optical Amplifier Arrays

Small-signal gain, resonant-mode gain, and saturated output power are studied on two Ka-band quasi-optical slot-antenna amplifier arrays fabricated with commercial MMICs on aluminum-nitride substrates. The amplifier arrays have small-signal gains of 2.1dB at 31.02 GHz and 6.5 dB at 31.40 GHz, respectively. The average small-signal gain of the active array is 10 dB over passive. In resonant mode, the amplifiers have small-signal gains of 10.7 dB at 31.52 GHz and 11.8 dB at 31.47GHz. In saturation, the arrays deliver 89 W EIRP or 0.3W output power at 30.40 GHz and 145 W EIRP or 0.5 W output power at 31.15GHz, respectively.