Wide area surveillance systems are becoming more important for border and homeland security, earth resources monitoring and mitigation of natural disasters such as floods and seismic activity. As the frequency spectrum is being utilized for communications and business networking, the available bandwidth for these important efforts is more difficult. Historically, airborne surveillance radars ha...

The ultra wide band antennas are required in applications where larger bandwidth for the transmitting signal is needed. They cover wide bandwidth in the range from 500 MHz to the frequencies above 8000 MHz. In this paper, a review of various techniques to realize ultra wide band microstrip antennas (MSA) is presented. They are realized by using different techniques like basic planar monopole an...

Gallium Nitride (GaN) amplifiers have demonstrated very high power density as well as wide band width in previous research. This paper examines their use in supplying flat gain, power, and linearity across a large band width. It demonstrates two types of power amplifiers: a Ft Doubler (FT2) amplifier and a Cascode amplifier, both of which require a simple PCB tune. Both amplifiers show 0.2 to 4...

Recent developments in the use of composite ceramics for high frequency arrays have reached the stage where large area, high frequency sonar receiver arrays can be produced cost effectively [1]. Typically these consist of hundreds of individual sensors with excellent element-to-element matching, in both gain and phase, over bandwidths in excess of an octave centred on frequencies in the range 3...

A series of observations were made between 15 June and 9 July 1995 in an attempt to determine the system temperature, gain, and SEFD (System Equivalent Flux Density) for each antenna of the VLBA as a function of frequency for all bands. Each band was divided evenly into frequencies which extended beyond the nominal bandwidth. This was done to test antenna performance across the full band and es...

We present Johnson UBV , and Kron-Cousins I photometry for about 60,000 stars in a region of 44 × 33 arcmin2 centered on the Galactic globular cluster (GGC) NGC 2808. The central r < 100 arcsec region has been mapped also in the F218W, F439W, and F555W bands with the HST WFPC2 camera. Overall, we cover a field which extends from the center to about 1.7 tidal radii. Photometric calibration has b...