Radio-Frequency Phase-Difference Networks: A New Approach to Polyphase Selectivity

It is shown that phase-difference networks operating at radio rather than at audio frequency may be used to obtain selectivity by polyphase methods. Design and practical realization of such networks are considered. A polyphase selective system suitable for single-sideband transmission or reception is described, in which the selective action takes place directly at radio frequency so that a number of individual systems may be cascaded in situations where a very high degree of over-all selectivity must be obtained.