Wide Passband Filter Offers Good In- And Out-Of-Band Characteristics

April 12, 2007

Wideband-, multiband-, and wireless-communications systems demand compact, low-insertion-loss microwave bandpass filters. But wideband couple-line bandpass filters with 3-dB fractional bandwidths greater than 20 percent tend to be difficult to fabricate. A new coupling structure for filter design is proposed by M.K. Mandal, P. Mondal, S. Sanyal, and A. Chakrabarty from the Indian Institute of Technology (Kharagpur, India). This compact bandpass-filter design uses only one resonator, which is excited by two open microstrip stubs. To obtain wide bandwidth, a ground-plane architecture technique is employed.

The resulting filter can vary 3-dB fractional bandwidth between 1.0 and 90.0 percent with good in-band and out-of-band filter characteristics. A prototype of FBW 45.1 percent and passband center frequency f₀= 3.795 GHz shows a maximum passband insertion loss of 2.0 dB. See "Novel Compact Bandpass Filters with Wide Controllable Fractional Bandwidth," Microwave and Optical Technology Letters, Jan. 2007, p. 29.

About the Author

Nancy Friedrich

RF Product Marketing Manager for Aerospace Defense, Keysight Technologies

Nancy Friedrich is RF Product Marketing Manager for Aerospace Defense at Keysight Technologies. Nancy Friedrich started a career in engineering media about two decades ago with a stint editing copy and writing news for Electronic Design. A few years later, she began writing full time as technology editor at Wireless Systems Design. In 2005, Nancy was named editor-in-chief of Microwaves & RF, a position she held (along with other positions as group content head) until 2018. Nancy then moved to a position at UBM, where she was editor-in-chief of Design News and content director for tradeshows including DesignCon, ESC, and the Smart Manufacturing shows.