Half-Mode Substrate Integrated Waveguide Filters With Arbitrarily Inserted Transmission Zeros

In this paper, a filter design method, which can arbitrarily insert transmission zeros (TZs) into the transfer responses, is proposed. By loading the zero nodes to the source and load, TZs could be generated with regard to these zero nodes. The number and positions of the TZs could be independently controlled by only adjusting the zero nodes. On the basis of half-mode substrate integrated waveguide (HMSIW) technologies, two types of HMSIW filters, which have a TZ located above the passband, or at both sides of the passband, are analyzed, fabricated, and measured to validate the proposed method. This method has an advantage of generating any number of TZs at any position without increasing the filter loss, although it is at the expense of filter size.