Reconfigurable Filter for Military Radio Using MEMS Switches
A reconfigurable filter bank using Menlo Micro’s “Ideal Switch” technology offers high-power handling, high IP3 and little variation over temperature. Developed for land, air and seaborne military radios, the filter covers the primary military VHF and UHF bands from 225 to 512 MHz and can be scaled to operate in the HF bands.
Configured as a four-pole bandpass filter, this reconfigurable filter bank uses four MM5130 SP4T switches integrated with discrete high-power handling inductors and capacitors. The design handles up to 30 W CW power and achieves insertion loss below 1.5 dB, which is up to 3 dB less than traditional switched filter banks. The single resonator filter architecture yields a size of 3.4 x 1.6 x 0.7 in., greater than a 90 percent reduction in volume compared to switched filter banks using PIN diodes.
MEMS switches have several advantages over solid-state technologies: lower loss, higher input power handling and better RF linearity. MEMS designs have very low “on” resistance, which provides the lowest possible insertion loss, and the low “off” capacitance reduces signal leakage in the “off” state. These lower parasitics enable high-Q tunable resonators with little degradation in RF performance compared to a fixed resonator design.
MEMS switches have ultra-low mass, which withstands extreme shock and vibration without any detectable performance degradation from the switches. Filters using the MEMS switch operate over wide temperature ranges with thermal dissipation and RF variation over temperature much lower than comparable solid-state designs. These factors contribute to significant size, weight, power and cost advantages over traditional tunable or switched filter banks for military radios. The lifetime of Menlo Micro’s MEMS switch technology is more than 3 billion on/off switching operations, which supports the long lifetime requirements of military radios.