Extended dielectric material tapered slot antenna

[0002] This is a continuation of prior application Ser. No. 08/705,567, filed Aug. 29, 1996, abandoned, which is hereby incorporated herein by reference in its entirety.

[0003] 1. Field of the Invention

[0004] The present invention relates to a tapered slot antenna and, more particularly, to a tapered slot antenna with an extended dielectric substrate as a dielectric loading for tuning the E and H field beam width.

[0005] 2. Description of the Prior Art

[0006] Tapered slot antennas are generally known in the art and used in various microwave communications systems. Examples of such tapered slot antennas are disclosed in U.S. Pat. Nos. 5,036,335; 5,081,466 and 5,187,489. Such tapered slot antennas are also discussed in Antenna Engineering Handbook, 3rd Edition, McGraw-Hill, Inc., pgs. 8.4-8.9 (1993).

[0007] Such tapered slot antennas are normally formed on a dielectric substrate by photolithography techniques. Such tapered slot antennas include a metallization layer formed on one side of the substrate. A portion of the metallization layer is etched away to the substrate to form a tapered slot that extends to the edge of the substrate. A microstrip feed line is formed on an opposite side of the substrate by way of a metallized strip. The metallized strip it positioned adjacent a narrow portion of the slot, formed on the opposite side of the substrate. A plated through hole or small diameter wire is known to be used to couple the microstrip feed to the tapered slot antenna formed on the opposing side of the dielectric. When used in receiver applications, incoming electric magnetic radiation is received by the tapered slot antenna and coupled to the microstrip feed line, which, in turn, is normally coupled to signal conditioning circuitry, such as a low noise amplifier.

[0008] Unfortunately, such tapered slot antennas have asymmetric radiation patterns. In other words, the H-plane beam width is relatively wider than the E-plane beam width. As such, the gain and the coupling efficiency of such tapered slot antennas is relatively low.

[0009] It is an object of the present invention to provide a tapered slot antenna which solves various problems in the prior art.

[0010] It is yet another object of the present invention to provide a tapered slot antenna with a symmetrical radiation pattern in order to increase the gain and coupling efficiency of the antenna.

[0011] Briefly, the present invention relates to a tapered slot antenna which may be formed by photolithography techniques which includes a dielectric substrate with a metallization layer deposited on one side. The metallization layer is etched to the dielectric to form a tapered slot. In order to tune the antenna, for example, such that the E and H fields are symmetrical, the substrate extends beyond the wide portion of the slot. A microstrip feed line is formed by a metallization deposit on an opposing side of the substrate. The microstrip feed line extends across a narrow portion of the tapered slot and is configured to optimize the coupling between the microstrip feed line and the tapered slot antenna.

[0012] These and other objects of the present invention will be readily understood with reference to the following specification and attached drawing, wherein:

[0013] FIG. 1 is a top view of a tapered slot antenna in accordance with the present invention, illustrating a tapered slot antenna formed on one side of a dielectric substrate and a microstrip feed line formed on an opposing side of the substrate.

[0014] FIG. 2 is an enlarged partial view illustrating the slot to microstrip feed line transition.

[0015] A tapered slot antenna in accordance with the present invention is generally identified with the reference numeral 20. The tapered slot antenna 20 provides for tuning of the E and H fields, for example, to provide for symmetrical radiation patterns to improve gain and coupling efficiency. As shown in FIG. 1, four tapered slot antennas are shown, formed on a single substrate. However, the principles of the present invention apply equally to single or other multiple tapered slot antennas formed on a single substrate.

[0016] The tapered slot antenna 20 may be formed from conventional photolithography techniques and includes a substrate 22 formed from a generally planar dielectric material. Suitable dielectric materials for use as the substrate 22, for example, duroid, having a thickness of 5 mil. A metallization layer 24 is deposited on one side of the substrate 22 to a thickness of 0.8 mil by a known metal deposition method, such as metal cladding. Various electrical conductive materials, such as copper, may be used for the metallization layer 24. As shown, the metallization layer 24 is etched to the substrate 22, for example, by photolithography to form a plurality of linearly tapered slots 26, 28, 30 and 32. As shown, the tapered slots 26, 28, 30 and 32 are formed as generally linear V-shaped slots. However, it will be appreciated by those of ordinary skill in the art that the principles of the present invention are also applicable to other slot geometries, such as exponentially tapered slot geometries, for example, as shown in U.S. Pat. No. 5,036,335.

[0017] An important aspect of the invention is an extended dielectric portion 34 which extends beyond the metallization layer 24. In known tapered slot antennas, for example, as disclosed in U.S. Pat. Nos. 5,081,466; 5,187,489; and 5,036,335, the metallization layer is normally extended between opposing ends of the substrate. In the present invention, in order to provide for tuning of the E and H field beam width, for example, to create a symmetrical radiation pattern in order to improve the gain and coupling efficiency of the antenna, the metallization layer 24 is not extended between opposing ends 36 and 38 of the substrate 22. Rather, the metallization layer 24 extends only partially between the opposing ends 36 and 38 to define the extended dielectric portion 34. The extended dielectric portion 34 acts as an impedance that can be used to tune the E and H fields of the antenna. In the example shown in FIG. 3, the total length of the substrate 22 is, for example, 1.213 inches, while the metallization layer 24 only extends 1.0113 inches from the end 36. The length of the extended dielectric portion 34 may be determined experimentally by forming antennas with different length metallizations in order to determine a length of the metallization which results in the desired radiation pattern, for example, a symmetrical radiation pattern.

[0018] A plurality of microstrip feed lines 40, 42, 44 and 46 are formed by way of a metallization layer on an opposing side of the substrate 22. The microstrip feed lines 40, 42, 44 and 46 enable the tapered slot antennas formed by the notches 26, 28, 30 and 32 to electromagnetically couple the tapered slot antennas to an external circuit (not shown). Each microstrip feed line 40, 42, 44 and 46 is formed to a thickness of .08 mil and formed as generally elongated conductors along an axis generally parallel to a longitudinal axis 47 of the substrate 22, extending from one edge 36 of the substrate 22. An opposing end of each of the microstrip feed lines 40, 42, 44 and 46 is formed with a reduced thickness portion 48, 50, 52 and 54 at an angle, for example 45°, with respect to the longitudinal axis 47. The ends of the reduced thickness portions 48, 50, 52 and 54 of the microstrip feed lines 40, 42, 44 and 46 are formed with circular portions 56, 58, 60 and 62, having a diameter of, for example, 20 mil.

[0019] As shown best in FIG. 2, non-tapered curved slot portions 64, 66, 68 and 70 are formed as extensions of the narrow end of the tapered slots 26, 28, 30 and 32. As shown in FIG. 2, the non-tapered curved slot portions 64, 66, 68 and 70 are formed as relatively narrow slots, having a width, for example, 2 mil and non-linear, formed for example by two linear portions formed end to end at an angle, for example 45° relative to one another, such that the cross-over point between the curved slot portions 64, 66, 68 and 70 and the reduced width portions 48, 50, 52 and 54 of the microstrip feed lines 40, 42, 44 and 46 cross at generally 90° relative to one another. Circular slots 72, 74, 76 and 78, having a diameter of, for example, 7 mil are formed at the end of the curved slot portions 64, 66, 68 and 70. The reduced thickness portions 48, 50, 52 and 54 short circuit the curved slot portions 64, 66, 68 and 70. There is no plating of 64, 66, 68, 70 at the cross-over point. The configuration of the microstrip feed lines 40, 42, 44 and 46 with the curved portions 56, 58, 60 and 62 of the slots provides optimal coupling between the tapered slot antennas formed by way of the notches 26, 28, 30 and 32 and an external circuit.

[0020] Obviously, many modifications and variations of dielectric loading of the present invention are possible in light of the above teachings. For example, shape variations of the extended dielectric substrate, i.e., changes of the thickness, width, or drilling holes as another form of the dielectric loading. Thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described above.