Could the antenna pattern be in energy instead of in power?

In general, the limited antenna power patterns in frequency domain are used to describe the antenna performance. It is enough to describe the antenna performance in narrow band communication systems. However, the limited antenna power patterns in frequency domain are not enough for ultra wideband (UWB) antennas or arrays in communication systems. The energy pattern of antenna is the total response of power patterns in frequency domain. It will be easier to describe the energy pattern instead of power pattern for UWB antennas. In this paper, electromagnetic energy, electromagnetic power, energy pattern, energy gain, energy directivity and energy efficiency will be discussed. In order to verify the theory of antenna pattern in energy, Yagi Uda antenna, narrow band multibeam smart antenna, UWB bow-tie slot antenna, UWB comb taper slot antenna, and UWB antenna arrays with different element spacing are studied and measured by the impulse time domain system. The energy pattern is quite similar to that of power pattern for narrow band antennas. The grating lobes of UWB antenna array will not occur at the energy pattern even if the element spacing of array is larger than one wavelength.