Showing papers on "Reflective array antenna published in 1970"
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24 Mar 1970
TL;DR: In this paper, 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 in low and high-band VHF.
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.
38 citations
TL;DR: In this paper, the behavior of log-periodic dipole (LPD) antennas, which are compressed along the transmission-line axis, was studied both experimentally and theoretically, and it was found that compressed LPD antennas are efficient, of low gain, and frequency independent.
Abstract: The behavior of log-periodic dipole (LPD) antennas, which are compressed along the transmission-line axis, is studied both experimentally and theoretically. Compressed LPD antennas are found to be efficient, of low gain, and frequency independent. With compression, the radiation pattern approaches dipole-like behavior and the bandwidth increases slightly. It is also found that LPD antennas exhibit anomalous frequency-dependent behavior in narrow bands of frequencies ( \approx 1/8 of a log period in width) when a reactive termination is used and when the scaling factor \tau is below about 0.92-0.93.
36 citations
TL;DR: In this paper, a phased array antenna element which provides good circular polarization over a broad sector of coverage in an array environment has been designed and evaluated, where the concept is the superposition of complementary antennas, the dipole, and the slot, to achieve equal E - and H -plane patterns in the array environment.
Abstract: A phased array antenna element which provides good circular polarization over a broad sector of coverage in an array environment has been designed and evaluated. The concept is the superposition of complementary antennas, the dipole, and the slot, to achieve equal E - and H -plane patterns in the array environment. This element, when evaluated in a large test array, demonstrated an ellipticity of less than \pm2.0 dB over a coverage of \pm60 degrees. By proper control of the excitation of the two isolated antennas any desired polarization can be achieved.
35 citations
17 citations
TL;DR: In this article, a circular array radar antenna designed for operation over a 20-percent bandwidth has demonstrated improved performance over that of linear arrays, where the beam pointing angle is independent of frequency.
Abstract: A circular-array radar antenna designed for operation over a 20-percent bandwidth has demonstrated improved performance over that of linear arrays. A major advantage is that the beam pointing angle is independent of frequency. The array developed and tested provides 128 beam positions with a beam crossover of about -2 dB, a half-power beamwidth on the order of 4 or 5 degrees, and a sidelobe level of -25 dB. Step increments of one element per beam position allow practical implementation of step scanning, i.e., simple commutation of the current distribution. Two approaches are possible for feeding and scanning the ring array: 1) a vector-transfer system involving 3-bit phase and amplitude boards which are capable of amplitude attenuation (VT scan) and 2) a lens feed system employing an R-2R parallel-plate region, with the spacing between the plates less than 1/2 a free-space wavelength, so that only the electric-field component perpendicular to the plates is propagated. Energy is launched and extracted from the lens by means of monopoles mounted 1/4 wavelength in front of the circumferential ground plane enclosing the lens. Computations involved in determining current distribution are based on [1] and [2].
16 citations
TL;DR: In this paper, the mutual impedance between the dipole elements of the antenna is taken into account, and the field radiated due to a surface wave reflector of finite extent is determined by calculating the surface current distribution on the reflector plate.
Abstract: A method is set up for a theoretical investigation of arbitrary backfire antennas based upon dipole structures. The mutual impedance between the dipole elements of the antenna is taken into account, and the field radiated due to a surface wave reflector of finite extent is determined by calculating the surface current distribution on the reflector plate. Numerical results obtained for Yagi backfire antennas and short-backfire antennas using this theory are compared with experimental results.
13 citations
TL;DR: A class of circuits is described that can be used with a phased-array antenna in order to allow a given array feed system to provide phase control for a phased array with many more elements.
Abstract: A class of circuits is described that can be used with a phased-array antenna in order to allow a given array feed system to provide phase control for a phased array with many more elements Alternatively, certain variations of these circuits can be used alone to provide phase control for small arrays while using only a single phase shifter for each direction of scan
7 citations
01 Jan 1970
4 citations
TL;DR: In this article, it was shown that in an optimized system, the number of elements in one antenna is one greater than in the other, and the ratio of interelement spacings is inversely proportional to the square of the numbers in the respective arrays.
Abstract: When array antennas are used for wide-frequency operation a difficulty with grating lobes is encountered at the upper frequency end of the operating band. This paper points out that the use of arrays for transmission and reception with different interelement spacings can be used to extend the operating frequency band in a radar system. The principle of transmitting-receiving arrays with different illuminations was used by Mattingly [2] to lower the sidelobe level of a radar array antenna. Birge [3] used it to reduce the number of elements in an array while preserving the resolution. The same principle is used in this paper to extend the operating frequency bandwidth of a radar antenna system. Relationships for an optimized radar array antenna system are derived. The criterion for optimization is the maximum bandwidth with a given total number of elements. It is shown that in an optimized system the number of elements in one array antenna is one greater than in the other, and the ratio of interelement spacings is inversely proportional to the square of the number of elements in the respective arrays. Based on these conditions, a function k is computed and tabulated. This function determines the number of grating lobes permissible in the specified angular sector, without overlap, as a function of the number of elements in the two arrays. An application to a high frequency (HF) ionospheric radar antenna system, now under construction, is used as an illustration of the principles outlined in the paper.
4 citations
TL;DR: In this paper, a unique unidirectional octave-bandwidth reflector type circularly polarized antenna is described which uses crossed parallel connected conical dipoles operated near second resonance.
Abstract: A unique unidirectional octave-bandwidth reflector type circularly polarized antenna is described which uses crossed parallel connected conical dipoles operated near second resonance. The impedance characteristics of the antennas together with added series reactances gives the desired approximately quadrature current relation between the two dipoles. The axial ratio does not exceed 2 to 1.
4 citations
TL;DR: When the physical dimensions are adjusted properly periodic linear arrays, commonly known as Yagi-Uda arrays, may possibly be used as open waveguides or directional antennas operating at two or more widely separated frequency bands.
Abstract: When the physical dimensions are adjusted properly periodic linear arrays, commonly known as Yagi-Uda arrays, may possibly be used as open waveguides or directional antennas operating at two or more widely separated frequency bands. Other applications include open low-pass or bandpass filters and open resonators.
TL;DR: In this paper, the design and development of two types of stacked, vertically polarized, collinear arrays of three independently fed omnidirectional antennas operating at frequencies of 1550, 2702.5, and 4252.5 MHz are described.
Abstract: The design and development of two types of stacked, vertically polarized, collinear arrays of three independently fed omnidirectional antennas operating at frequencies of 1550, 2702.5, and 4252.5 MHz are described.
01 May 1970
TL;DR: 最近, とみに注目を集めているアンテナ, 最初概観的に解説した後, レーダー, 衛星通信, 電波天文用アANテナなどの応用について述べ,
Abstract: 最近, とみに注目を集めているアレイアンテナ, 特に電子走査のためのフェイズドアレイアンテナについて, 最初概観的に解説した後, レーダー, 衛星通信, 電波天文用アンテナなどの応用について述べ, 最後に, これらアレイアンテナに共通のアンテナ固有の諸問題について論じる.
02 Nov 1970
TL;DR: In this article, the authors describe one type of dual-frequency antenna that has been made operational in particular, this antenna is the MIT - Millstone Hill antenna, which has a dual-channel capability.
Abstract: : The need, in microwave tracking and radar systems for antennas with a dual-frequency capability, has necessitated the development of multi-frequency, multipurpose antennas It is the purpose of the report to describe one type of dual-frequency antenna that has been made operational In particular, this antenna is the MIT - Millstone Hill antenna
TL;DR: In this article, the satellite provides a uniform phase front and, for any appreciable elevation angle, meets the height requirement as a boresight source for large-aperture antennas.
Abstract: Theoretical and experimental results have shown that a satellite repeater can be used to measure accurately transmit and receive gains of ground-communications antennas. The satellite provides a uniform phase front and, for any appreciable elevation angle, meets the height requirement as a boresight source for large-aperture antennas.
01 Jul 1970
TL;DR: In this paper, the basic techniques of beam formation, steering, and receive/transmit (transponder) functions of a phased array antenna system are reviewed for the first time.
Abstract: This is a survey paper wherein phased array antenna systems, now operating on spacecraft, are reviewed so as to reveal their basic techniques of beam formation, steering, and receive/transmit (transponder) functions. Laboratory developmental antennas, designed for ultimate spacecraft flight qualification, are assessed in terms of the needs of communications, earth resources instrumentation, and area surveillance.
01 Jan 1970
01 Jan 1970
TL;DR: In this article, an aperture phase distribution is described that provides the maximum reflection-lobe dispersion for an arbitrary reasonably smooth amplitude distribution, which is an explicit function of the amplitude distribution.
Abstract: Reflection lobes in phase-scanned arrays with traveling-wave feeds can significantly degrade sidelobe levels. These lobes can be dispersed if the regularity of the feed system can be destroyed. In this communication, an aperture phase distribution is described that provides the maximum reflection-lobe dispersion for an arbitrary reasonably smooth amplitude distribution. This phase distribution is an explicit function of the amplitude distribution. The theoretical limitations on reflection-lobe dispersion in one- and two-dimensional arrays are determined and compared with the calculated properties of a sample linear array. The edge effects are also indicated.