Designing maximally flat quarter-wavelength-coupled filters using the Q distribution method
Four filter design examples are presented using the Q distribution (QD) method 1 to develop maximally flat quarter-wavelength-coupled transmission line filters accurately using arbitrary resonators. This article demonstrates the accuracy of the QD method using a variety of resonators and provides examples of the design procedure. Accordingly, each example employs a different type of resonator. The first example uses lumped-element bandpass resonators. The second and third examples use quarter- and half-wavelength tapped-stub resonators, respectively. The fourth example employs capacitively loaded half-wavelength tapped-stub resonators. The responses for these examples are approximately equal to the ideal maximally flat response, thereby further demonstrating the accuracy of the QD method.