The evaluation board for the ADGM1304, a dual-chip radio frequency (RF) switching solution containing a single-pole four-throw (SP4T), micro-electromechanical systems (MEMS) switch and a control chip co-packaged in a compact 5 mm × 4 mm LFCSP package. The SP4T switch uses Analog Devices, Inc., MEMS switch technology, providing optimum performance in terms of bandwidth, power handling capability, and linearity for RF applications. The control chip generates the high voltage signals needed for the MEMS switch and allows the user to control its operation through a simple and flexible complementary metal-oxide semiconductor/low voltage transistor-transistor logic LVTTL compliant parallel interface.

The evaluation board comes fitted with connectors for RF and control signals as well as links to allow the user to control the operation of the switch and evaluate its performance.

Consult the ADGM1304 data sheet for operating information when using the evaluation board.

The circuit shown in Figure 1 uses RF MEMS switches to route an RF signal between two surface-mount RF attenuators and two straight through paths.

Attenuating RF signals is commonly done in RF test instrumentation and receiver front ends to protect downstream circuitry and to increase dynamic range. Using discrete attenuators and switches maximizes design flexibility and routing options. In the Figure 1 circuit, two ADGM1304 single-pole, four-throw (SP4T) RF MEMS switches in a back to back configuration yield four independently switchable paths between input and output. Two of the paths are straight through transmission lines, the third path contains a 6 dB attenuator, and the forth path contains a 9 dB attenuator. Key to realizing this application is the use of ultralow insertion loss and highly linear switches to multiplex between the different path options.

The switches must be as transparent as possible to the RF signal and add as little insertion loss and distortion as possible. The ADGM1304 switches offer best in class insertion loss of 0.26 dB typical at 2.5 GHz, and a third-order intercept (IP3) performance of 69 dBm typical. In addition to insertion loss and distortion, another key benefit that the MEMS switch brings to this application is its ability to operate down to true dc. This means the switches do not limit lower frequency operation in a typical RF instrumentation attenuator switching application, and enables the instrument to pass dc bias voltages when required.

The physical size of the ADGM1304 device at 4 mm × 5 mm × 0.95 mm yields a significant reduction in printed circuit board (PCB) area compared to traditional electromechanical relays switching solutions. In addition, the actuation speed of the ADGM1304 switch is 30 μs, a significant improvement over electromechanical relays, which are in the order of milliseconds and introduce significant time lag in measurement systems. The actuation lifetime of the ADGM1304 device is guaranteed for one billion cycles, which is a major improvement over electromechanical relays and significantly increases overall system reliability.