# Antenna Arrays And Python – Patch Efficiency & Gain

Last post I dealt with antenna directivity, this post discusses antenna gain which is closely related.

Gain combines an antennas directivity and efficiency to describe how good it is at sending/receiving power in a direction. This is useful for things like link budget analysis which basically calculates if two antennas can communicate.

Antenna Gain, G, can be calculate from the directivity, D, and antenna efficiency, εr by:

The efficiency of an antenna describes how well the input power is radiated by the antenna (and due to reciprocity receive efficiency is the same as transmit efficiency):

A high efficiency antenna will radiate most of the input power while a low efficiency antenna will lose a lot of the input power before it is radiated due to things like dielectric loss, impedance mismatch, etc.

Patch Efficiency

The Python script at the bottom of the post is based on the ArrayCalc calc_patchr_eff.m file and defines a function, `CalculatePatchEff`, that calculate the efficiency of a rectangular patch based on the patch dimensions and materials. The comments provide some example material properties and the main function has some examples that demonstrate the effects of the material selection on the efficiency:

```FR4 Patch, 14GHz, Efficiency = 47.27%

RO4350 Patch, 14GHz, Efficiency = 62.32%```

Python Script