Application of CMRC in antenna switch

For time division duplex (TDD) systems, a PIN-diode transmitting/receiving (TX/RX) switch is widely used for switching between the transmit and receive section to the antenna. There are two commonly used PIN diode antenna switches. The dual-biased switch is compact but with a relatively large control current consumption. The single-biased switch only needs half the current consumption, but needs a section of λ/4 microstrip transmission line and its applications are limited due to this size constraint. As power saving is a very important feature for portable communication equipment, the single-biased antenna switch is attractive if its size can be reduced. The compact microstrip resonant cell (CMRC) is a kind of microstrip structure with some suitable patterns on the conductor strip. To achieve a size reduction of the switch, we propose a CMRC with a spiral pattern. The CMRC with spiral pattern was employed to build a single-biased PIN diode antenna switch. With the CMRC as the λ/4 impedance transformer, the switch is not only reduced to a practical size, but the rejection of second harmonic radiation is greatly improved.