Abstract-Since its introduction in 1994 direct conversion sixport receivers have attracted a considerable attention at microwave frequencies, with most recent work focusing on the so called sixport receivers with analog I/Q generation. Besides its applications at microwave frequencies, six-port receivers with I/Q regeneration play a crucial role in the optical communications field, as they are the most promising candidates for optical coherent receivers that are being developed for 100 Gigabit Ethernet transceivers. In this paper we analytically model the influence of six-port junction hardware impairments on receiver performance. New analytical expressions are developed which give geometrical interpretation of signal constellation distortion due to hardware impairments and allow for the definition of several interesting figures of merit. Closed formulas are also proposed to analytically calculate BER degradation, under AWGN conditions, from these figures of merit. Finally, the proposed formulas are validated by means of simulation, and it is shown that they can be of practical interest to set the specifications of the six-port junction components.
Abstract-In this paper a robust technique for the design of high performance directional couplers is proposed.It combines the advantages of wiggly coupled lines and slot-coupled lines but overcomes their main limitations. The key to this novel technique is a new corrugated slot that allows perfect compensation of the even and odd mode phase velocities and can be easily designed using BlochFloquet theory, yielding outstanding performance. To demonstrate the validity of the proposed technique, the design of two different wideband directional couplers is presented. The first design consists of a 10 dB asymmetric directional coupler with a one decade bandwidth (1.2-12 GHz) that exhibits a coupling accuracy of 10 ± 0.6 dB, a return loss better than 23 dB and an isolation better than 28 dB across the complete frequency band. The second design consists of a symmetric quadrature hybrid that operates over the complete UWB band (3.1 to 10.6 GHz) showing an amplitude and phase imbalance between the output ports lower than ±0.5 dB and ±0.7 • , respectively.
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