Abstract: The combination of a Vivaldi slot and a meander line loaded antenna is provided which exhibits an ultra wideband characteristic with the Vivaldi notch expanding the high end and with the meander line loaded antenna portion reducing the low frequency cut-off. When these antennas are arrayed, this array exhibits a single lobe and an ultra wide 100:1 bandwidth. The Vivaldi notch portion of the antenna accommodates the higher frequencies, whereas the meander line loaded antenna portion of the antenna accommodates the lower frequencies, there being a smooth transition region between the Vivaldi and meander line portions of the antenna and no discontinuity. In one embodiment, the antenna is made to work between 50 MHz and 1500 MHz with a VSWR less than 3:1. The Vivaldi notch meander line combination assures that for an array one does not have a separation of the elements more than a 0.5 wavelength at the highest frequency, thus to eliminate the possibility of creating grating lobes.

Abstract: The present invention features a compact tunable meander line loaded patch antenna where switches or the like are used to electrically connect and disconnect sections of the meander line adjusting the electrical length of the antenna. A fixed or switched series capacitance is used to overcome the inductance of the meander line. In one embodiment, a quarter wavelength mode patch antenna can be constructed which occupies significantly less space than conventional patch antennas. This size reduction is important when the antennas are to be used on mobile platforms where real estate is at a premium and larger antennas cannot be used.

Abstract: A device for holding a wheelchair stationary on a floor has a pair of notched plates at their rearward ends adapted to abut a transverse barrier upstanding from the floor and to be releasably engaged at their forward ends by a bail fastened to and swinging from the floor to engage the forward ends of the notched plates with sufficient resilient force to lock the wheelchair in position.

Abstract: Electrically conductive metal is melted, preferably by a flame, and is sprayed onto a freshly exposed, pitted surface of a concrete member having iron embedded therein. The sprayed metal, when cooled, forms a metal cover on and interlocked with at least part of the newly exposed surface. The cover and the embedded iron are preferably joined in an electric circuit affording a direct current electromotive force, effectively opposite to that which normally would occur, in order to preclude the deterioration of the contained iron.

Abstract: The sweep rate of a linearly swept frequency generator is increased while maintaining strict linearity by artificially increasing the number of zero axis crossings of the output signal from a linearly swept voltage controlled oscillator over those that would naturally occur during a linear sweep. This permits an increased sampling rate which, in turn, permits the oscillator sweep rate to be increased without loss of accuracy. Increasing the number of zero axis crossings is accomplished by introducing phase shifts in the output of the oscillator at calculated sampling times with phase shifting being accomplished indirectly by heterodyning the swept oscillator output with the output from a fixed oscillator whose output signal is phase shifted by discrete amounts during the frequency sweep. Only a small number of phase shifts need be introduced due to the discovery of certain symmetries of phase when sweeping through a frequency range.