Pulse transformers which are associated with the power modulators of radar equipment, for example, need to have a wide pass-band in order to allow high-power pulses to pass without distorting them to an excessive degree. The fact is that, at high frequencies, owing to the leakage inductance and the stray capacitance of the windings, the leading edge of the pulse tends to lose its steepness and to diverge from the ideal shape for a pulse edge. On the other hand, the low frequencies in the band are short-circuited owing to the influence of the non-infinite magnetizing inductance, since the impedance of the inductance decreases.
It is desirable to reduce as far as possible the effect of the leakage inductance and stray capacitance and stray capacitance especially in the case of transformers which operate with a low impedance, where the leakage inductance becomes the major disturbing factor. However, in this case a new disturbing factor makes its appearance which arises from the length of the external connections between the pulse generator and the primary winding of the transformer. This disturbing factor is termed the connection inductance and in the equivalent-circuit diagram of the transformer it is connected in series with the leakage inductance. Its operation is, however, independent of that of the leakage inductance although it too deforms the leading edge of the pulse.