Won Jang

Design of attenuated horn antenna to receive high power pulse

In this paper, we propose the new attenuated horn antenna configuration to measure high power pulse more than several hundred MW to avoid the RF break down in a short distance. The proposed antenna configuration is more compact and flexible to change attenuation level according to measurement ranges in comparison with high power measurement using high power attenuator. We designed the attenuated horn antenna with attenuation value about -96dB at 3GHz and -83dB at 10GHz. The proposed attenuated horn antenna is composed of a horn antenna, ridged waveguide and attenuated rectangular waveguide. We designed three sections individually and after designing, we combined three sections. We simulated the final antenna configuration for the performance verification. The proposed antenna configuration is applicable to receive high power microwave pulse effectively.

Design of T/R module for the wideband active array antenna

In this paper, a wideband sub-array module which has 4-channel T/R modules was built and evaluated. The T/R module has 5-bit digital MMIC phase shifter, attenuator, amplifiers, Wilkinson power dividers, etc. Two absorptive matching equalizers to get uniform gain over multi-octave bandwidth are inserted in the common part of the module. Chip-on-substrate technology was introduced to get the repeatability for the packaging of MMIC chips. To eliminate the cavity resonance of the module housing, the absorbing material is attached on the housing. Two types of the sub-array modules were built for the interface with the planar triangular array lattice. These modules are attached to a cold plate to remove the heat of the power amplifiers in the module

Circuit modeling of spark-gap switch and fat dipole for DS pulser

Design process for DS pulser consisted of spark-gap switch and fat dipole antenna has been represented. The performance of pulser is predicted using both circuit simulation and EM simulation, and these predictions are confirmed by comparison with test result. The proposed design process will be applied to more complex structure of high power wideband pulser in the future.

A New Stable Solution for TD-EFIE using weighted Laguerre Polynomials as Temporal Basis Functions

In this paper, we propose a new stable solution for the time domain electric field integral equation (TD-EFIE) for arbitrarily shaped conducting structures, which utilizes weighted Laguerre polynomials as temporal basis functions. The proposed algorithm is based on the Gerlerkins scheme that involves separate spatial and temporal testing procedures. RWG triangular vector basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D conducting structures. In order to verify the proposed method, we compared the results with the inverse discrete Fourier transform (IDFT) of the analytic solutions or the electric field integral equation solutions in frequency domain

Electric field measurement with Electro-Optic sensor of high power W-band gyrotron

We present electric field measurement with Electro-Optic (EO) sensor of high power W-band gyrotron. EO sensors serve as minimally invasive field receivers as compared to metal-based electronic field probes. A rectangular waveguide WR-10 for W-band is used in order to calibrate the probe since the field strength inside the waveguide can be accurately calculated based on the output power measured by RF power meter. Then, the performance of the sensor is evaluated by high power W-band gyrotron and its measurement result of power is compared with that of calorimeter.

Design of RF pulse generator with parabolic cylinder reflector fed by Yagi antenna

In this paper, we design a wideband RF pulse generator. Fig. 1 shows a schematic diagram of the RF pulse generator. It is comprised of a high-voltage charging system, a spark-gap switch, and a fat dipole antenna. Since the antenna and the spark gap switch are united, the source may be compact and robust. Marx generator is used as high-voltage charging system. The spark gap switch is located at the middle of fat dipole antenna. The antenna is charged to a high voltage and then shorted at the center by the spark-gap switch. The charge energy stored in the antenna then oscillates at the resonant frequency of the system and produces high-power electromagnetic pulse. The radiated field form of such source is a damped sine waveform. Since the antenna pattern of RF pulse generator using fat dipole antenna is omnidirectional, we design Yagi and parabolic cylinder reflector fed by Yagi antenna for high-power electromagnetic pulse generator to increase radiated power and direct energy in a desired direction. For the compact and mobile system, Yagi is limited 3 elements and the size of parabolic cylinder reflector is limited 3m x 2m.

The Array Geometry Design in Airborne Microwave 2-D Direction Finding

The resolving ambiguity of phase interferometer is necessary when the baseline separation between elements exceeds half wavelength since the phase difference between elements can only be measured modulo 2pi. It is difficult to meet the condition the minimum distance between two antennas is less than half wavelength for avoiding ambiguity in wideband operation. In this paper, we propose a simple and efficient array design method which minimizes the probability of ambiguity. This method adapts NLA (nonuniform linear array) geometry. And there is no need to maintain the distance between antennas less than half wavelength. We also show some numerical examples and experimental results of the 2-D array prototype for airborne application