Call statistics show that communication with Low Earth Orbit (LEO) satellite systems occurs primarily at low elevations at or near the horizon. However, current LEO satellite telephones and similar handheld and compact communication devices generally employ circular polarisation antenna technologies, such as patch or conventional helix, that generate a cardioid antenna pattern more suited to high elevations.
Helix Technologies is developing a lightweight, compact, high-performance antenna with a toroidal radiation pattern that will maximise the circular polarisation gain at the horizon rather than at the axis bore-sight as with a conventional circular polarised antenna. This pattern distinction is illustrated in Figure 1 and Figure 2 below for an L-band antenna resonating at 1.591 GHz and 1.667 GHZ respectively.
Clearly, if the radiation efficiencies of the two antenna types are equal, the toroidal pattern offers a significant link-margin uplift for LEO satellite links in which the path elevations are generally low (<45° above horizon).
At the horizon the toroidal pattern antenna may have as great as a 10dB link-margin advantage over a conventional helix antenna and as much as a 20dB link-margin advantage over a conventional patch-based antenna.
Other inherent benefits of the dielectrically loaded helix construction include:-
- No gain ripple
- Small element size
- Intrinsically impedance matched
- Excellent radiation bandwidth – no pattern droop at band edges
- Possibility to implement a secondary cardioid pattern GPS mode in the same antenna
For more information on our compact, high performance LEO satellite terminal antennas please get in Contact with us.