Wideband Filter-Integrated Switch Based on Bandpass-to-Bandstop Switchable Filter Network

In this letter, a new design method for a broadband filter integrated switch based on a bandpass-to-bandstop switchable filter network is proposed. By switching p-i-n diodes <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on/off</small>, the proposed topology achieves two distinct filtering properties of a wideband bandpass filter (BPF) and bandstop filter (BSF), which correspond to the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on-/off</small>-states of the switch. For two states, the relationship among fractional bandwidth (FBW), return loss (RL), and stopband rejection (SR) is analyzed by using a set of established equations. The design concept is demonstrated by a BPF integrated single-pole single-throw (SPST) switch with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{0} =3$</tex-math> </inline-formula>GHz and FBW=59.7%, which is formed on a multilayer PCB. In addition, because the BSF has high input impedance over a wideband, the SPDT switch based on a switchable filter network does not require an additional matching circuit to achieve noninterference between the two channels, which has a FBW of 58.7%, high <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>-state suppression (OSS) of 26.2 dB, and isolation of 29.1dB.