The Diode as a Frequency-Changer for Measurements at Ultra-High Frequencies

The increasing use of ultra-short wave radio communication has created a need for the measure­ment of oscillating electric currents, potential differences, and field strengths, at very high fre­quencies, up to at least 300 megacycles per second. The difficulty of measuring these quantities can be greatly reduced by converting the original frequency to a much lower `intermediate' frequency by the well-known heterodyne process, provided that the law is known which connects the amplitudes of oscillation at the two frequencies. Theory suggests that the diode frequency-changing circuit as described, for example, by Strutt¹, possesses a linear conversion law if it is used with a heterodyning oscillation of sufficiently large amplitude. The linearity of this law has now been demonstrated by experiments carried out in the Radio Department of the National physical Laboratory at frequencies between 4 and 000 megacycles per second for amplitudes between about 10 and 30,000 microvolts.