Closed-form expression for mutual impedance of the short not-too-closely spaced dipoles with constant current distribution

Closed-form expression for mutual impedance of not-too-closely spaced short dipoles with constant current distribution is derived analytically using definition integral relation based on a method of electromotive forces (EMF) and approximation of sine and cosine functions by two or three terms of Taylor series expansion. The values given by analytical expressions are compared with the ones calculated numerically and relative error is presented up to the dipole distance of λ₀. The derived expressions might be beneficial for evaluation of e.g. input resistance of close but not-too-closely spaced elements in multi-element monopole arrays.