Showing papers on "Monopole antenna published in 1970"

Computer-aided radome analysis

Abstract: A procedure is presented for predicting by computer the radiation pattern of an antenna in the presence of a radome. The case of a horn antenna radiating through an actual aircraft radome is treated in detail, and a comparison is made between computed and measured antenna patterns. Good agreement between theory and experiment is noted.

Miniature tv antenna

Abstract: An antenna for TV reception predominantly in the low band and high band VHF ranges having dipoles of significantly reduced physical length as compared with conventional dipoles for reception of signals respectively in the low and high band VHF ranges. Inductive elements are employed to form a portion of the dipole length to permit significant reduction in the physical length of the dipole. The dipoles are electrically isolated from one another by suitable trap circuits to isolate high band VHF operation from low band VHF operation. Lossy components are deliberately added to the dipole section of the antenna to provide significantly improved noise matching and power transfer between antenna and amplifier. The inductive elements further provide good impedance matching between antenna and amplifier to optimize power transfer. The antenna is provided with end loads of the capacitive-type for improving both current magnitude and current distribution across the dipole in both low band and high band VHF operation. Separate amplifier channels are provided for low band and high band VHF signals to improve gain and reduce intermodulation and cross modulation effects, among other. A passive UHF section may be integrated into the array.

Pattern distortion due to edge diffractions

Abstract: The method of combining wedge diffraction solutions for the analysis of an axial TEM-mode slot is extended here for an arbitrary aperture antenna in a finite size ground plane. The new approach, however, considers superposition of boundary-value and wedge-diffraction solutions on the same antenna. The boundary-value solution (primary pattern) considers the pattern component when the aperture is in an infinite ground plane, and the diffraction solution (secondary pattern) considers the contribution to the pattern from the edges of the finite ground plane.

Helical coil coupled to a live tree to provide a radiating antenna

Abstract: This device is an air-cored toroidal coil having dimensions much less than the wavelength of the applied frequency. It may be used as an omnidirectional antenna or as a coupler for converting a much larger object, such as a forest, into a giant antenna.

Theory of a vertical tubular antenna located above a conducting half-space

Abstract: The input admittance and the current distribution of a finite vertical tubular dipole antenna located above an infinite dissipative half-space can be found as a function of the distance above and the electric properties of the dissipative half-space. An integral equation for the current on the surface of the antenna is formulated and subsequently solved by numerical evaluation of associated moment functions in the Fourier transform plane. The magnitude, but not the distribution, of the current is found to be strongly affected by the presence of the dissipative medium. At certain distances above the half-space, the input conductance of the antenna reaches its maximum value.

Helical dipole antenna

Abstract: An antenna for communication equipment, in which a conductor in the form of a ribbon or strip is helically wound upon a tube or rod which is made of plastic material or the like.

Orthogonal dipole antennas

Abstract: A drooping dipole antenna having a center combination supporting mast and indicator balun structure with the drooping dipoles electrically close to the ground and part of the guy support system for the antenna effective primarily in the skywave mode of operation, but also producing a useful vertically polarized surface wave component with the droop of the dipole elements. Further, with two of these antennas colocated in an orthongonal configuration and the two antennas substantially at right angles sufficient mutual isolation is advantageously attained that the two input terminals are connectable simultaneously to two transmitters, two receivers, or one transmitter and one receiver.

Retroflector dipole antenna array and method of making

Abstract: A method of making an antenna array and an antenna array apparatus of a low-cost wide angle retroreflector is provided in which a printed circuit board has a plurality of antenna elements etched on one side thereof and a ground plane on the other separated by dielectric material of a predetermined thickness. Baluns are attached through the printed circuit board to each antenna element and to the ground plane and transmission lines of equal length connect spaced pairs of antenna elements utilizing the balun and matching the transmission line to the antenna element.

Experimental investigation of the broad-band properties of a continuously loaded resistive monopole

Abstract: A resistive monopole was designed using thin-film evaporation techniques. Measurements of radiation patterns were made over a 100:1 frequency band and compared to the theory of Wu and King. Current amplitude measurements exhibited a more rapid fall-off at the higher frequencies than the almost linear decay observed at the low frequencies. The input admittance was found to have a relatively gradual increase with frequency and reached a final value of approximately ( 16 + j4 ) m \Omega M-1The efficiency of the antenna was observed to increase markedly with increase in frequency.

Application of microwave holography in the study of the field from a radiating source

Abstract: Microwave holography is applied to the investigation of the radiation mechanism of a monopole. It is shown that a radiating monopole can be described mathematically as two point sources located at each end of the monopole. A microwave hologram was recorded using liquid crystals which upon optical reconstruction yielded two points as predicted by the theory. Using optical techniques, one can visualize the field at the antenna plane, at a plane in the Fresnel zone, and at a plane in the far field. This technique is, however, only one example of microwave holography in the investigation of a radiator. It can be very useful in designing any type of antenna.

Mobile deflectable antenna with impedance matching

Abstract: A tiltable monopole antenna of the type to be mounted on an automobile rooftop or the like as a transmitting-receiving antenna for mobile radio communication equipment. A novel antenna-to-mounting base structural connection greatly simplifies the antenna and mounting base assembly as these parts provide a rigid pivotal connection and are held together by a transversely extending pin. Impedance matching means is provided within the mounting base of the antenna to match the antenna with the given transmission line connected thereto over a given frequency range.

Mechanically swept radar antenna for use with an aircraft landing monitor system

Abstract: An radar antenna for use in an aircraft landing monitor which includes an elongated antenna housing mounted on a vertical pivot for horizontal oscillation in the nose of an aircraft. An elongated horn reflector mounted along the housing supports a resonant edge-slotted waveguide array therein for transmitting and receiving radar signals with a radar beam pattern narrower in the azimuth than in the elevation plane. An elongated bar spring is mounted in the housing and is rigidly attached to the vertical pivot in order to tend to maintain the desired oscillation of the antenna housing. A motor oscillates the antenna housing about the vertical pivot to sweep the radar beam over a predetermined azimuth angle. Circuitry is provided to sense the position of the antenna housing and for maintaining the antenna sweep at the predetermined azimuth angle and rate.

Radar antenna arrangement

Abstract: A radar antenna utilizing primarily antenna having a pencilshaped radiation characteristic and two secondary radar antennas which supplement the primary antenna and are disposed adjacent the periphery of the primary antenna, the secondary antenna each having a fan-shaped radiation characteristic, the secondary antennas being of such shape and so arranged as to effect an intersection of the fan-shaped beams thereof to form a joint overlapping range, one of the secondary antennas being utilized for transmission of interrogation signals and the other secondary antenna being utilized for the reception of reply signals whereby the transmission-reception of such signals is effected in such overlapping range. One of the secondary antennas may be disposed adjacent the upper or lower edge of the primary antenna and the other secondary antenna disposed adjacent a side edge of the primary antenna, and each of the secondary antennas may be provided with a radiator for side-lobe suppression.

Energy density antenna apparatus for mobile radio receiver

Abstract: An energy density antenna has a magnetic current antenna in the form of a slot in a conducting plate and an electric current antenna in the form of a unipole normal to the plate with the signals from each antenna independently coupled to separate square law detectors and combined to provide an output signal which is relatively immune to fading due to motion of the antenna through a standing wave pattern.

Glide slope antenna system

Abstract: A switchless glide slope antenna system maintaining horizontal polarization during capture and track functions. The antenna system comprises a track antenna and a capture antenna arranged in an aircraft landing gear door so that switching from capture to track antenna occurs automatically upon gear extension by cross-polarization of the capture antenna.

On the radiation from a vertical dipole with an inductive wire-grid ground system

Abstract: The far field of a vertical electric dipole on a sectionally homogeneous ground plane is considered. The specific model used is a dielectric-like ground which is modified by using an inductive wire grid or mesh screen in a region surrounding the dipole. Attention is focused on the modification of the radiation pattern resulting from the presence of the inductive ground screen. It is demonstrated that the low-angle radiation may be greatly enhanced by a ground screen which extends out to 15 or more wavelengths.

Plug in antenna, antenna base and test probe system

Abstract: An antenna mounting system, including a base plate having a rear coaxial connector to which a coaxial cable is permanently attached. The base plate is permanently attached to the exterior of the mounting surface with the coaxial connector extending inwardly thru a hole in the mounting surface. An antenna mounting plate or a test probe fits onto the base plate. The antenna or test probe is secured to the base plate by bolts, thereby allowing for the rapid removal of the antenna and replacement thereof by the test probe.

Duplexed antenna for retransmission devices

Abstract: A dual antenna system formed on a common structure includes two antennas operating within different frequency ranges. In one embodiment of the invention the central conductor of a coaxial line defines the receiving element of one antenna and the shield of the coaxial line is employed as the receiving element of the second antenna. A ground plane for the first antenna is coupled to the coaxial shield. In a second embodiment of the invention the central conductor of the coaxial line is electrically divided to serve as the receiving element of both antennas, and the shield of the coaxial line forms a part of the ground element of one of the antennas. Duplexing circuitry connected to the antenna separates the signals received at the two antennas and applies the separated signals to the appropriate receiver or transmitter.

Antenna for direction finding systems

Abstract: An antenna arrangement for a shipboard direction finding system is designed to be carried on the ship mast and includes electrically parallel connected, substantially vertically polarized dipole antennas which are uniformly distributed circumferentially in a circle with their radiating elements outwardly inclined from the antenna mast and forming an angle of approximately 30* therewith. A motor controlled rotating differential condenser is connected between the dipole halves and ground to provide means for bringing the dipoles into capacitive symmetry. The antenna arrangement is adapted to be used in proximity to a mast-carried UHF direction finding antenna system through the use of two-terminal networks connected to the dipole elements.

Multi-band tunable halfwave whip antenna

Abstract: A physically shortened halfwave antenna of the whip type is disclosed. The antenna includes a main antenna rod, a pair of helices, one helix coupled to each end of the rod, and a capacitive top load coupled to the upper one of the helices. An RF terminal is inductively coupled to the lower one of the helices to supply RF energy to or remove RF energy from the antenna. A variable capacitance means is coupled between the lower helix and a capacitive bottom load, which may be ground, a small ground plane or an equivalent arrangement, to resonate the antenna. A plurality of lower helices and an associated variable capacitance means for each are selectively connected to the rod to enable the antenna to cover a relatively broadband frequency range. In one embodiment an inductive coupling to the lower helix is accomplished by a single tuned arrangement for the lower frequency band of the frequency range and by a doubled tuned arrangement for the middle and upper frequency band of the frequency range. Other embodiments may include all single tuned arrangements, all double tuned arrangements or a different combination of single and double tuned arrangements than that used for said one embodiment. A directional coupler and capacitance control arrangement are provided to adjust the capacitance of the variable capacitance means for reresonating the antenna when the resonance of the antenna is changed by an object coming into the proximity of the antenna.

Triangle-loop antenna

Abstract: An antenna for receiving three widely separated frequency bands; the antenna beginning with a triangular tapered section fed by a coaxial line and continuing with several loops terminated in the center at ground.

Unfurlable isotropic antenna

Abstract: The invention is a broadband isotropic antenna of the triorthogonal type. It is a randomly polarized antenna system that has particular application in satellites. The antenna consists of three independent antenna elements arranged in a mutually orthogonal configuration. Each of the elements is mounted on unfurlable partitions contained within an inflatable spherical enclosure.

Electromagnetic pulse generation by an impedance loaded dipole antenna

Abstract: A theoretical study is made for obtaining the pulse radiated from an impedance loaded dipole. Numerical results are presented for an antenna that is slowly charged and suddenly shorted at the terminals. The impedance loadings are chosen as those on an existing antenna located at Sandia Laboratory, Albuquerque, N. Mex.

Adjustable center loaded antenna arrangement

Abstract: A center-loaded antenna arrangement having a fixed loading coil in a whip antenna, and a tuning core mounted for movement through and out of the coil, said core having a ferrous section and an inductor ring section. Suitable connecting means connects an end of the coil to a radio ground and to a radio transmitter or receiver through a R.F. transmission line. This connecting means is preferably connected to the radio ground through an impedance matching device which couples the coil to the transmitter or receiver.

Low profile antenna mounted on a watercraft

Abstract: An omnidirectional, ultra high frequency transmitting antenna is disclosed having an unusually low profile and being of unusually rugged physical construction. A cylindrical monopole is attached to the outside conductor of a coaxial cable, and the center conductor is fastened to the apex of a conical dipole, with mechanical spacing and support between the dipoles being supplied by means of a ring of low loss dielectric material which provides dielectric loading for the antenna. With the dielectric loading, the height of the antenna can be made appreciably less than in the case of a conventional dipole antenna. A light flasher is incorporated into the cylindrical monopole as an aid in visually locating the antenna and associated equipment.

Quasi-near-zone field of a monopole antenna and the current distribution of an antenna on a finite conductive earth

Abstract: A mathematical expression is derived for the quasi-near zone of a monopole antenna on a finite conductive earth. Measured data are used to show the effect of finite conductivity of earth on the current distribution of dipole antennas.

Adjustable configuration uhf loop antenna

Abstract: A built-in television antenna, particularly suitable for use as a UHF antenna, is made of a loop of convoluted metal tubing.

Receiver with input phase control between antenna and chassis

Abstract: A receiver system including a differential input of which one end is connected to the antenna and the other end is grounded to the receiver chassis and a phase control device for adjusting the phase relationship between the antenna signal and the parasitic signal extracted from space by the receiver chassis.