Microstrip bandstop attenuation equaliser - has three open circuited stub lines connected via specified resistors to continuous metallic strip

摘要

The equaliser is for the microwave range, and consists of a substrate completely coated with a metal layer on one side. The other side has a continuous metallic strip from which open circuited stubs branch off. The length of the stubs and their separation corresponds to a quarter wavelength at the stop band centre frequency. A resistor (R1-R3) is inserted at the junction of each stub with the conducting strip (3). The resistors (R1, R3) in series with two outer stubs (4, 6) have specified equal resistances normalised w.r.t. the characteristic impedances of external connecting lines. The resistances are functions of the maximum attenuation in db. the series resistor (R2) of the middle stub line (5) has a valve R2 = 1/2(R1-1/R1)Z212, where Z212 is the normalised value of the characteristics impedance of the conducting strip sections (7, 8) between the stub lines.