Novel microstrip multifunction directional couplers and filters for microwave and millimeter-wave applications

Abstract

The design of a new class of microstrip couplers and filters is presented in this paper. The synthesis functions obtained from the solution of first-order nonlinear differential equation of nonuniform lines with a loose coupling assumption are modified and validated for higher coupling values. The design employs a nonuniform coupled line configuration along which a realizable continuous coupling coefficient is obtained by modifying the reflection coefficient distribution function. This modification results in a frequency selective coupling which minimizes the out-of-band coupling in the specified frequency range. As a result it is possible to realize-3 dB directional couplers using double-coupled lines without the need for tandem connections or extreme photolithographic techniques. Experimental results for microwave band-pass and periodic couplers are presented together with the computed results. Potential applications of these novel components are discussed and the work is extended to include millimeter-wave realization.

Design of a novel transversal filter

“…However, it is difficult to design broadband active and passive circuits with bandwidth of more than 20%. Research on transversal filters which are useful for broadband systems has been performed [2][3][4]. These transversal filters have the following advantages.…”

Multifolded Bandwidth Branch Line Coupler With Filtering Characteristic Using Coupled Port Feeding

“…[1] and [22] are the few reported quadrature coupler with filtering characteristic, and their performances are shown and compared in Table 2. In comparison, Ref.…”

“…Also the maximum bandwidth is a major concern in coupler design with the 18% measured bandwidth in Ref. [22] being defined by a coupling factor of 4.1±0.25 dB. The measured bandwidth in Ref.…”

“…In Ref. [22], only one port has bandpass characteristic, resulting in few practical applications. Also the maximum bandwidth is a major concern in coupler design with the 18% measured bandwidth in Ref.…”

“…The coupler filter proposed by Uysal and Watkins [21,22], made by non-uniform transmission lines had a relative bandwidth of 18% but occupied an area of more than 2-wavelengths by 5-wavelengths at the center frequency. Therefore, small size and wide bandwidth are found in antenna and feeding network integration [23].…”