Opto-VLSI-Based Dynamic RF Signal Combiner

Abstract

Many applications including antenna beamforming and RF signal processing, require broadband RF signal combiners [1]–[3]. The key specifications of an RF signal combiner include low loss, compact size, compatibility with existing RF systems and very good channel isolation [4]. Several structures have been proposed for realising RF signal combiners, such as resistive signal adders [5], Wilkinson combiners [6] and active signal adders [7]. All these structures have limitations that make them unattractive for broadband RF signal processing. For example, while resistive adders are broadband devices, their power losses are quite high (due to the skin effect). Wilkinson combiners have relatively low RF losses, however, their most common problem is poor interport isolation [8]. Active RF combiners are capable of adding gain to the output [9]. However, such combiners cannot accurately control the combination ratio, and also their operating frequency band is typically narrow