It is now common practice to utilize the quadrature RF coils to improve the signal -to-noise ratio (SNR). In addition, to draw such an available SNR improvement, it is mandatory to use a well designed quadrature coupler which facilitates a perfect 3dB coupling and quadrature-phase shift. However, the four ports matching condition has to be well considered during the RF excitation and the signal detection period. This work investigates the effects of such a mis-matching condition from the simulation and real implementation and derives the possible measure to minimize the resultant signal loss.
It not only has accurate quadrature but currently has not more than -22dB reflection loss and more than 25dB decoupling between two RF coil systems. Which is more, using quarter lambda technique, it has more than 80dB isolation between Tx and Rx port during Transmit/Receive switching. As a result, the SNR of our system increases 3dB to be compared with the old one. Considering power loss and reduction of size, we used RT/duroid 6010 substrate and for simulation we used compact software.
It will be a solution to the concern of getting nonmagnetic, high power and high Q spare parts when using higher frequency in its future. Since it can also be easily reproduced and reduced in sizes, it will be more widely used.