Geometry Of the Base Element

Classical Design

The classical EMVS array consists of three short dipoles and three small loops, as in Fig.1, each connected to its own receiver [201]:

Fig.1. Classical EMVS

Modified Design

As demonstrated in [202], the dipoles could be eliminated if the loops are loaded with two receivers at the opposite sides, then each element serves both as a loop and as a dipole. Two such elements are shown on Fig.2:

Fig.2. Double loaded loops

Proposed Design

We propose a slightly modified version of the double-loaded loop element as shown on Fig. 3, where the receivers are located at the loop center and connected to the opposite corners of the loop with open wire feedlines:

Fig.3. Proposed base element

The signals from the two receivers are fed to the PC, and their sum and difference are computed. When the two signals are added in-phase (Sig = RX1 + RX2), the element works as a vertical dipole, with the upper and lower triangles serving as dipole shoulders; when the signals are added 180 degrees out of phase (Sig = RX1 - RX2), the element turns into a K6STI receiving loop [203], also known as Alford loop [204] and LZ1AQ crossed parallel loop [205]. If only one of the signals is used and the other one is discarded (Sig = RX1), this element becomes a W2PM Mini Diamond Flag [206].

Validation

To validate the proposed element design, 4nec2 antenna modeling software [207] was used to compute the 3D radiation patterns of a short dipole, small loop, and the proposed double-loaded element in the dipole, loop and flag modes. The computed patterns are shown on Fig.4 and Fig.5.

b

Fig.4. 3D radiation patterns of a short dipole (a) and a small loop (b)

c

Fig.5. 3D radiation patterns of a double-loaded element in the dipole (a), loop (b) and diamond flag (c) modes

As expected, all patterns are toroids, except that of the diamond flag, which is a 3D cardioid. The radiation patterns of the double-loaded element in the dipole and loop modes are identical to those of the short dipole and small loop antennas respectively.

Proposed EMVS Array

Three mutually orthogonal double-loaded loops form the proposed EMVS receiving antenna array. The elements of the array may be oriented either as shown on Fig.6, or in the ground-symmetric way as suggested in [208]. In the latter case, the antenna is rotated so that one of the triangles that form its octahedron shape is parallel to the ground.

Fig.6. Proposed EMVS Array