||The Alford loop antenna; particulary for use with plane polarized radio waves. An Alford loop antenna is typically used in radio navigation systems, such as a VOR (VHF Omnidirectional Radio) system, and in instrument landing systems. An Alford Loop Antenna includes several elements, each of which is driven with a correct ratio of power and at a right phase difference with respect to the other elements of the Array, so that the radiated signal pattern will consist of a RF Carrier, a Sideband Carrier modulated at 90 Hz and the other Sideband Carrier modulated at a selected frequency in space by a process known as space modulation.
||International Telephone and Radio Manufacturing Corporation
||May 26, 1942
|Broad Band Antenna
||A broadband high frequency Alford loop antenna. Improvement upon US patent No. 2,283,897.
||Mackay Radio and Telegraph Company
||August 24, 1943
||A radio beacon capable to give correct course indications despite the presence of many reflecting objects. This is achieved by comparison of time position of impulses instead of amplitudes.
||Federal Telephone and Radio Corporation
||April 29, 1947
|Localizer Antenna System
||An Instrument landing System (ILS); consists of two independent sub-systems, one providing lateral guidance (localizer), the other vertical guidance (glide slope or glide path) to aircraft approaching a runway. Aircraft guidance is provided by the ILS receivers in the aircraft by performing a modulation depth comparison. It enables a safe landing during instrument meteorological conditions (IMC), such as low ceilings or reduced visibility due to fog, rain, or blowing snow.
||June 22, 1954
|Monitor for two frequency localizer guidance system
||A monitoring arrangement for use in a two frequency localizer guidance system using a single antenna array is disclosed. This monitoring arrangement is designed to provide monitoring signals equivalent to those that would be provided by monitors located at a distant point on the course and at a distant point located at a selected angle off the course. Additional monitoring for the clearance transmitter signals and means for determining the existence of major faults such as short circuits or open circuited lines or major injuries to the equipment.
||January 10, 1978
|Stacked arrays for broadcasting elliptically polarized waves
||Improved performance of a stacked array of short helical elements is achieved by using average spacing between elements which is less than one wavelength. Still better performance is obtained by using as antenna elements structures comprising combinations of Z-shaped radiators.
||September 16, 1980