Communications: radio wave antennas – Antennas – Wave guide type
Patent
1997-06-20
1998-09-08
Le, Hoanganh T.
Communications: radio wave antennas
Antennas
Wave guide type
343840, 343781R, H01Q 1914, H01Q 1912
Patent
active
058051163
ABSTRACT:
The satellite communications terminal employs separate transmit and receive feedhorns, offset from one another, to achieve adequate isolation of received and transmitted signals during full duplex operation. In one implementation, described herein, the satellite communications terminal employs an ultra-small-aperture dish antenna having an aperture of about one meter. Signals are received and transmitted at Ku band wavelengths of about 12 gigahertz and 14 gigahertz respectively. For this implementation, an extended focal point zone occurs, rather than a discrete focal point. Both the receive and transmit feedhorns are positioned within the focal point zone thereby achieving adequate gain to both reception and transmission. However, the receive and transmit feedhorns are offset from one another to minimize the coupling of feedback transmission signals into the receive feedhorn. In one specific implementation, for use in transmitting signals to and receiving signals from a geosynchronous satellite, the receive feedhorn is positioned at an ideal focal point for reception to maximize the receive gain. The transmit feedhorn is offset within the focal point zone by an amount sufficient to achieve adequate isolation while also minimizing off-axis signal transmissions, which might interfere with the reception of signals by other adjacent geosynchronous satellites. For other implementations, wherein the frequencies of reception and transmission and the characteristics of the antenna dish yield significant Fresnel diffraction effects, the ideal focal points for reception and transmission may be offset from one another. In such implementations, the receive and transmit feedhorns are both positioned at their respective ideal focal points. Method and apparatus implementations of the invention are disclosed.
REFERENCES:
patent: 4638322 (1987-01-01), Lamberty
patent: 4712111 (1987-12-01), Ohta et al.
patent: 5434586 (1995-07-01), Kinoshita et al.
Edmonston Brian S.
Le Hoanganh T.
Miller Russell B.
Qualcomm Incorporated
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