Wave transmission lines and networks – Coupling networks – Delay lines including long line elements
Reexamination Certificate
2000-02-17
2001-08-14
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Coupling networks
Delay lines including long line elements
C333S164000
Reexamination Certificate
active
06275120
ABSTRACT:
FIELD OF THE INVENTION
This patent application relates to the field of phase shifters, and more particularly, to phase shifters that use microstrip conductors.
Background of the Invention
In a phased array antenna system, the overall. antenna system includes a plurality of different antenna elements that are individually steered to direct and/or receive a beam in a selected direction. By using a phased array antenna system, it is possible to reduce the side lobes and, thus, minimize any power that is wasted in the antenna system.
With this type of system, the antenna bear is steered by adjusting the relative phase shift of each antenna element through individual phase shifters that are connected to each antenna element. The arrays are also typically sensitive to frequency. To overcome any sensitivity to frequencies, the phased array antenna system typically will use time delay steering where the signals propagated in each antenna element are time delayed to create a time coherence, and thus, steer the antenna beam into the predetermined direction.
Some prior art phased array antenna systems use a switched line phase shifter having more phase at higher frequencies than at lower frequencies. These type of phased array antenna systems require more bits of phase shift to achieve the same amount of phase at low and high frequencies. This also creates a limit to the amount of beam forming that can be accomplished at any one frequency for a given bandwidth. Other prior art switched delay line phase shifters are designed for different subbands, but require complex, expensive and large switching networks or diplexers. Others are complex and heavy, some even using lumped elements, requiring broad band attenuators that are expensive and leave a great signal loss, thus mandating increased Again requirements. Even others have used 0 to 180 degree hybrids, but only for narrow band applications.
One type of phased array antenna system uses time delay steering having a binary controlled and switched delay line. This system uses appropriately delayed signals in each antenna element channel and is disclosed in U.S. Pat. No. 3,295,138 to Nelson. Each switched delay line comprises a plurality of fixed time delays, which are combined to produce successive increments of delay in response to binary control signals.
It is also desirable to use a microstrip circuit to reduce the cost of implementing a phased array antenna system. Microstrip is less expensive than other known prior art construction techniques. An example of a microstrip phase shifter is disclosed in U.S. Pat. No. 3,568,105 to Felsenheid. In the '105 patent, a reflective system is used, but does not disclose a switched line phase shifter with any time delay. The '138 patent, on the other hand, does disclose a switched line phase shifter that switches between two line lengths. However, the structure disclosed in the '138 patent works primarily on one frequency and has a more exact differential phase, and is thus limited to a narrow band area. It would be advantageous if a switched delayed line phased array could be used with a wideband system in a low cost microstrip.
It is believed that some prior art phased array antenna systems provide some phase shifting using filters as a phase shift element, and provide phase performance in the 100 MHZ to 300 MHZ frequency range with reduced size, such as possibly found on microstrip. This type of phase shifter can be used as a phase shifter in either a switched or series digital configurations, and contains individual filters with controlled phase shift values. Typically, the phase shifters are placed in tandem, with progressively greater phase shift angles to provide phase angle selectivity. However, it is desirable to form a structure that can be used with a wide range of frequencies, such as broad band in one or two GHz, and positioned on a microstrip conductor.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a phase shifter used on a microstrip conductor that allows a broad band phase shift in the Gliz range, which can be readily manufactured at little cost with relative simplicity.
It is still another object of the present invention to provide a phase shifter using a microstrip conductor that can include several phase shift devices having progressively greater phase shift angles to provide phase angle selectivity in fie GHz range.
The present invention is advantageous because it allows the construction of a phase shifter a microstrip conductor and which accounts for broad band phase shift hybrid networks into a microstrip circuit without any complicated lumped element circuits. The phase shifter can also be combined to form a three-bit phase shifter that allows a beam to be minored around. The microstrip structure with the phase shift filter device of the present invention is also readily manufactured at low cost.
In accordance with present invention, a phase shifter includes a microstrip conductor and a substantially “U” shaped reference transmission line disposed as a microstrip conductor. This reference transmission line includes a base line and two legs extending from the base line.
A phase shift filter device is disposed as a microstrip conductor adjacent the reference transmission line. This phase shift filter device includes a phased base transmission line lying substantially parallel to the base line and adjacent to two legs of the reference transmission line. A substantially “U” shaped phased transmission line is connected to the phased base transmission line and forms an open area bounded by the phased base transmission line and the “U” shaped phased transmission line. The “U” shaped phased transmission line has a width less than a width of the reference transmission line.
In one aspect of the present invention, the phase shift filter device is formed as a 90° phase shift filter device. The radial stub is disposed as a microstrip conductor and bounded by the phased base transmission line and “U” shaped phased transmission line. The radial stub is connected to the “U” shaped phased transmission line.
REFERENCES:
patent: 3295138 (1966-12-01), Nelson
patent: 3568105 (1971-03-01), Felsenheld
patent: 4105959 (1978-08-01), Stachejko
patent: 4160220 (1979-07-01), Stachejko
patent: 4205282 (1980-05-01), Gipprich
patent: 4218664 (1980-08-01), Assal et al.
patent: 4238745 (1980-12-01), Schwarzmann
patent: 4652883 (1987-03-01), Andricos
patent: 4725792 (1988-02-01), Lampe, Jr.
patent: 4978933 (1990-12-01), Marconi
patent: 5451905 (1995-09-01), Gamand et al.
patent: 5489880 (1996-02-01), Swarup
patent: 5684440 (1997-11-01), Yabuki et al.
patent: 5703020 (1997-12-01), Das
patent: 6043722 (2000-03-01), Vaninetti et al.
patent: 6091311 (2000-07-01), Waters
patent: 123202 (1988-05-01), None
Gregorean Christopher
Marquardt Gregory
Vaninetti Roy
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Harris Corporation
Lee Benny
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