3.4/4.0 GHz Tunable Resonant Cavity in SIW Technology Using Metal Post and PIN Diode on a Low-Cost Biasing Network for 5G Applications

A novel and compact 3.5 GHz tunable bandpass filter in SIW technology with shunt‐inductive discontinuities switched by pin diode switches

“…A forward bias voltage of 0.85 V and a reverse bias voltage of −15 V were connected to the PIN diode through a bias filter composed of F I G U R E 2 Proposed tunable bandpass filter: A, bandpass filter, B, assembling configuration of the entire structure, and C, Schematic circuit of the PIN diode switch a quarter-wavelength microstrip line with a high impedance of Z H = 90 Ω and an open quarter-wavelength stub with a low impedance of with Z L = 20 Ω. 10 The chosen PIN diode is a surface mountable PIN diode used in applications from 10 MHz to more than 10 GHz. The PIN diode has a parasitic series inductance of 0.7 nH, a capacitance lower than of 0.20 pF for reverse bias voltage higher than 5 V, a series resistance lower than 1 Ω for a forward bias voltage higher than 0.80 V, and an input thirdorder intercept point (IIP3) of 25 dBm.…”

“…In order to provide tunability to the miniaturized bandpass filter and obtain other operation states at 3.5 GHz, all the MPs placed inside the SIW have one of their edges soldered directly to the SIW bottom wall and the other edge connected to the SIW upper wall through PIN diode switches. When the PIN diodes are switched off, the MPs do not significantly affect the electromagnetic field distribution inside the waveguide 9,10 . Switching on the PIN diodes, the MPs act as shunt‐inductive discontinuities, modifying the frequency response of the structure.…”

“…The PIN diode switches employ PIN diodes and biasing networks, and were designed to operate at 3.5 GHz. To assemble the switching elements and the bandpass filter in a single structure, a three‐layer implementation was considered, separating the biasing network from the microwave bandpass filter 9,10 . Figure 2A,B shows the proposed assembling configuration and Figure 2C shows the schematic circuit of the designed microwave switches.…”

“…In the series configuration, the switch is ON when the PIN diode is forward‐biased and OFF when it is reverse‐biased. A forward bias voltage of 0.85 V and a reverse bias voltage of −15 V were connected to the PIN diode through a bias filter composed of a quarter‐wavelength microstrip line with a high impedance of Z H = 90 Ω and an open quarter‐wavelength stub with a low impedance of with Z L = 20 Ω 10 …”

“…To perform a tunable and versatile filter, PIN diodes were used to design microwave switches assembled on the upper wall of the SIW component 9 . To improve the performance of the tunable filter, transmission lines are employed in the PIN diodes biasing networks to reduce the insertion losses 10 . The bandwidth of the proposed filter is controlled by the switching of the designed PIN diode switches, allowing three different operation states, converting the seventh order bandpass filter into a fifth order bandpass filter and into a regular SIW component.…”