High power passive semiconductor limiting

Semiconductor receiver protectors are often used to replace TR cell limiters. These may be active (switched) limiters, which can handle high power levels with low loss but offer no protection against unsynchronized signals, or passive limiters, which are activated by the RF power itself. Passive switching is generally less efficient than active, however, since thinner diodes must be used to ensure transmitted pulse. High power passive limiting can be achieved, however, by connecting several diodes in parallel; the insertion loss is minimized by resonating the diode capacitance with a parallel inductance. A high power L-band limiter, containing eight diodes in parallel at the input, is described and tested. A loss of about 1.3 dB was measured over the 1.25-1.35 GHz band for a power handling capacity of over 100 kW peak. These results are compared to those of experiments using switched limiters, whose performance as regards loss and power handling capacity, is shown to be superior.