SemiGen fixed attenuator pads feature precise resistor films and superior metallization to provide consistent performance and reliability. The use of advanced thin film technology enables the parts to have full side wraps for surface-mount or onboard installation. Gold bondable topside contacts for the input and output make the pads suitable for standard RF/microwave assembly techniques.
The fixed attenuators comprise devices with nominal attenuation values of 0 to 30 dB (in 1 dB steps). The attenuators contain wraps that connect the topside ground to the backside metallization of each die. The devices with nominal attenuation values of 1 dB or greater are fabricated using thin film resistors deposited on alumina. The circuit topology is a simple T structure that consists of two series resistors and a shunt resistance, which is realized as a pair of shunt resistors connected to the node between the two series resistors.
The resistances of each of the resistors are selected to simultaneously produce the nominal attenuation with very good input and output return losses. The attenuators with nominal attenuation values ≥6 dB contain a pair of cascaded T sections. The 0 dB attenuator is a 50 Ω microstrip transmission line with identical footprint and bond pads. The assembly technique of simply mounting the pad to the ground floor of the module or thin film circuit gives the user shorter bond wires and lower loss.
The high values also work as a 50 Ω load while the smaller values allow the user good signal level control. The ground wraps allow the pads to be small with an overall size of 0.030" × 0.030". The pads are optimized for coplaner waveguide or microstrip PCB and microwave module assemblies. Bond wire or ribbon is used to connect the input and output terminals to the transmission lines. Connection to ground is achieved through the topside wraps connecting to the bottom metalized surface. The size, ground wrap and process controlled resistor values allow the user enhanced power handling to over 5 W and return loss in the 30 dB range.