Abstract
In this paper, a novel synthetization approach is proposed for filter-integrated wideband impedance transformers (ITs). The original topology consists of N cascaded coupled line sections (CLSs) with 2N characteristic impedance parameters. By analyzing these characteristic impedances, a Chebyshev response can be derived to consume N + 2 design conditions. To optimize the left N − 2 variable parameters, CLSs were newly substituted by transmission lines (TLs) to consume the remaining variable parameters and simplify the circuit topology. Therefore, there are totally 2N − N − 2 substituting possibilities. To verify the proposed approach, 25 cases are listed under the condition of N = 5, and 7 selected cases are compared and discussed in detail. Finally, a 75–50 Ω IT with 100% fractional bandwidth and 20 dB bandpass return loss (RL) is designed and fabricated. The measured results meet the circuit simulation and the EM simulation accurately.
Highlights
Impedance transformers (ITs) have been widely used in microwave circuits and systems as a basic circuit component [1]
It consists of N cascaded coupled line sections (CLSs) with the electrical length θ, where Zevi and Zodi are the even-and odd-mode characteristic impedances of the ith CLS, and i = 1,2, . . . , N
The first, third, and fifth CLSs are substituted by transmission lines (TLs); the availability section is narrower than case 11, which is about 1.5 < k < 2.0 and the availability section is narrower than case 11, which is about 1.5 < k < 2.0 and 30◦ < θ < 35◦
Summary
Impedance transformers (ITs) have been widely used in microwave circuits and systems as a basic circuit component [1]. To realize DC block and reduce the circuit size, coupled line sections (CLSs) are widely used in wideband ITs and filters [31,32,33,34,35,36,37,38,39,40,41,42,43,44,45]. A novel synthetization approach is presented for filter-integrated multisection wideband ITs. From the point of view of the number of variable parameters, the wideband IT, which consists of N cascaded CLSs, is provided with a Chebyshev performance, where N + 2 design conditions are consumed, and N − 2 variable parameters remain.
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