High Power Symmetrical Switch Topology for Direct Antenna Modulated (DAM) Transmitters

Electrically small antennas continue to be a prevailing research topic due to the need to develop transmitters and receivers which could at high power and efficiency. However due to their electrical size, such antennas suffer from narrowband and minimal efficiency. Techniques such as direct antenna modulation (DAM) enable high efficiency bandwidth performance by utilizing a high-speed transistor switch which directly modulates the antenna at its peak energy. This enables transmission of high-bandwidth communication modulations such as FSK. However, due to the non-idealities of a switch from its parasitic capacitances, the power handling of the antenna is limited to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&lt;20 \text{dBm}$</tex>. Combined with the already minimal gain of the antenna, the link budget that such DAM systems could support is minimal. In this work, we propose a symmetrical complementary switch topology which combined with the antenna geometric symmetry, prevents coupling between the RF signal and the control signal needed to maintain DAM. Such mitigation of control ambiguity in the transistor network enables a measured RF power handling up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{4 2 ~ d B m}$</tex> at a data rate of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1. 7 9 ~ M b p s}$</tex> at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{7 5}$</tex> MHz with BFSK modulation despite the narrowband <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left \vert\mathrm{S}_{11}\right \vert$</tex> performance of the ESA.