Answers are grounded in this paper and cite their sources.
A varactor-loaded left handed loop antenna that has reconfigurable radiation patterns is described. The loop antenna uses a left-handed transmission line which is loaded with series capacitors and shunt inductors in a number of unit cells. The two wire transmission line is formed into a loop and fed at the break in the outer loop. The antenna has eight varactors in the four unit cells. Different radiation patterns can be obtained at the same frequency with variation of capacitance of the eight varactors. A prototype antenna implemented on FR4 substrate has dimensions of 150mm by 150mm with a line width of 1.4mm. The DC voltages are supplied to the varactors via the transmission lines by inserting slits in the strips. The antenna is analyzed by simulator "CST". Simulated performance is also confirmed by measurements.
No takes yet. Share an insight, caveat, or question.
Kelly et al. (2010) studied this question.
Synapse has enriched one closely related paper. Consider it for comparative context: