Measured bandwidth of resonant patch antennas supported by a conducting sphere with comparisons to Chu´s limit

In this work, we discuss the measurement process and construction of a unique antenna having a spherical shape. Measured data are then presented from which the antenna´s bandwidth can be determined. The antenna(s) are patch antennas with canonical spherical shapes supported by and underlying conducting sphere, Figure 1a. The unique nature of the feed precludes stored energy from existing inside the sphere and allows the antenna to approach, but not exceed, Chu´s limit, Figure 1b. Chu´s limit estimates the Q of electrically small antennas using the stored energy external to a sphere that encompasses the antenna. However, the stored energy inside the encompassing sphere is neglected, (e.g., a sphere encompassing a dipole.) The addition of this energy would raise the value of Q reducing the theoretical lowest possible bandwidth. Accordingly any calculation of Q is lower that can be achieved in practice.