A Si MMIC compatible ferroelectric varactor shunt switch for microwave applications

A New Ferroelectric Varactor Shunt Switch for Microwave and Millimeterwave Reconfigurable Circuits

“…The design of the ferroelectric varactor shunt switch has been reported previously [8,9]. Briefly, the varactor shunt switch consists of a CPW transmission line loaded by a ferroelectric varactor in the middle (as shown in figure 1), such that the large capacitance of the varactor at zero bias will shunt the input signal to ground, thus isolating the output port, resulting in the OFF state of the device.…”

“…The important device parameters are (i) the varactor area (overlap area of the metal1 and metal2 layers), (ii) CPW transmission line parameters, such as the width of the center conductor, spacing between the center conductor and ground lines, and length of the CPW line sections, (iii) parasitic inductance and resistance of the thin-line shunting to ground in metal1, and (iv) the dielectric properties of the nano-structured BST thinfilm. The varactor shunt switch can be precisely modeled as reported earlier [8,9]. The larger area of the varactor results in a large zero-bias capacitance of the varactor.…”

Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components

“…BST films exhibit an excellent tunable behavior at room temperature (in the case of 40%-60% concentration of barium), which lays the foundation for the microwave tunable devices. 5,6 The range of capacitance tuning in BST varactors is quite large (>3:1 in the linear region) and varactor devices are relatively simple in nature. Also, BST thin film based varactors have exhibited high power handling capability which is also attractive for applications in microwave and millimeter-wave communications.…”

“…The device is called the varactor shunt switch, as it behaves like a voltage controlled switch for allowing a RF signal to pass or not pass through. 5 Since the BST film has high relative dielectric constant at 0 V (and hence the shunt capacitor providing a high capacitance to ground), the RF signal is shunted to ground and reflected back resulting in the OFF state of the device. Applying a DC voltage to the signal line reduces the dielectric constant of the film to a lower value (and lower capacitance) allows most of the RF signal to go to the output port resulting in the ON state of the device.…”

Effect of Sr concentration on microstructure and magnetic properties of (Ba1−xSrx)(Ti0.3Fe0.7)O3 ceramics

“…They have been identified as a potential alternative to the current silicon oxide and nitride dielectrics in the next generation dynamic random access memories (DRAM) [1,2] because of their high dielectric response, especially in the vicinity of the ferroelectric Curie temperature T C [3]. The voltage-tunable dielectric constants with low dielectric loss show great promise for applications in microwave devices such as phase shifters, tunable filters, tunable resonators, varactors and switches [4][5][6][7]. In addition, high pyroelectric coefficients make BST a promising candidate for infrared (IR) detectors [8], most particularly, as the active sensing elements of focal plane arrays in thermal imaging systems.…”