Performance of a small loop antenna in the 3-10 MHz band

An electrically small coaxial loop antenna for HF

“…The radiation resistance for a small loop is given by [1]: 2 4 o A k 20 Rr ⋅ ⋅ ≈ (2) which in this case is approximately 5.4 Ω. A network analysis of the right half of the circuit in Figure 2 indicates that the sum of radiation resistance and the ohmic losses (Rr and Ro) was between 9 to 10Ω, and hence the efficiency of this particular loop is estimated to be between 50 to 60%.…”

“…The radiating element is a 66 cm diameter loop, made of 0.95 cm (3/8 inch) diameter copper tubing. The inductance for a small loop is given by the expression [1]:…”

“…Electrically Small (ES) loop antennas have been in use for the HF bands for many years, and the theoretical aspects have long been understood [1,2]. Typically, such antennas are comprised of a single loop about 1 meter in diameter, and power is introduced by a small offset coupling loop or some type of network [3].…”

Problems of implementation of ground biorthogonal and triorthogonal antenna systems

“…But the use of only such frequencies would mean a significant peak limitation of the operating range, which would be no more than approximately 1.5-fold. However, it is known [5,6] that loop antennas can easily enable operation in a 3-fold and even wider range. Moreover, the conducted investigations afford grounds for an assumption that operation is possible at frequencies up to the first resonance and even higher.…”

Design and evaluation of a cylindrical antenna for RFID in the 900-MHz band

“…On the other hand, there is the matching circuit outside the main radiation loop in some cases. For example, a matching circuit is connected to the feed point [4] or the structure of the main radiation loop is changed [5]. However, those antennas have a big size and those main loops have a complex structure [2].…”