A novel type of low-cost high performance coaxial cable coupler

A new type of extremely low-cost, high-performance couplers is presented in this paper. The proposed coupler consists of two U-curved coaxial cables with proper cuts on the bottom of the curves and soldered together. It has excellent performance in terms of high directivity, low VSWR, very good isolation, excellent EMI shielding, moderate and wide coupling bandwidth, and high power handling capabilty. Detailed analysis of the coupler is carried out for the first time. Some very useful properties of this kind of couplers are found. Strong couplings such as 3-dB can be easily realized with two tandem connected coupler of low coupling coefficients. We have successfully realized a 11-dB coupler with return loss of -30 dB and directivity of higher than 32 dB (maximum 42 dB), for example. Good agreement between measurements and calculations on one hand shows the excellent performance of the coupler, and on the other hand validates the design procedure.