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This article proposed an analytical synthesis approach of generalized strongly coupled resonator triplet (GSCRT) filters, which eliminates the need for negative couplings regardless of the location of transmission zeros (TZs). The principle of removing negative couplings in GSCRTs is explained from circuit level for the first time. In contrast with conventional filter function synthesis with all in-band reflection zeros (RZs), some RZs are preassigned out of the passband, which are named redundant resonant modes (or even modes). By regulating the frequency of the redundant modes, flexible synthesis solutions can be achieved and the previously published strongly coupled resonator triplet (SCRT) becomes a special case of this new generalized version. Besides, a novel physical interpretation of GSCRT from the basis of modes is presented, which shows the modes routing clearly within the coupling matrix framework. Due to the proposed theories, additional approximation and optimization can be avoided during the synthesis procedure. Due to the redundant mode, all couplings in the GSCRT are positive, thus easing the design and manufacturing process. Also, GSCRT brings compact and in-line configuration of filters. Moreover, due to the higher flexibility provided by redundant resonant modes, reasonable synthesis solutions can be selected depending on the specifications or other physical limitations, such as bandwidth and size. A group of synthesis examples with simulations are elucidated. The simulated results show a good agreement with the synthesis theories. The simulated and measured results of an anti-interference C-band eight-pole filter with four TZs below the passband further validate the effectiveness of the proposed theories. [ABSTRACT FROM AUTHOR]

The generalized Chebyshev (pseudoelliptical) filter functions may not be optimal for certain applications due to physical constrains. With redundancy in filter polynomials, this article breaks down the “mental barrier” in conventional synthesis and directly synthesizes the “Chebyshev-like” functions to achieve desired filter performance under physical limitations. By exploiting the redundant restrictions on exact equal-ripple response, the reflection zeros can be moved to the complex plane, thus forming the “Chebyshev-like functions.” A class of inline filters with a block of second-order dangling resonators is synthesized, which can generate a pair of symmetric transmission zeros (Tzs) but is considered unrealizable using standard Chebyshev functions. With the proposed theories, an accurate and much improved filter prototype is directly derived from the “Chebyshev-like” polynomials, avoiding additional optimization in the design process. For verification, a group of examples with synthesis results are elucidated. Eight ten-pole filters with four Tzs are synthesized and fabricated. The simulated and measured results demonstrate the effectiveness and application of the proposed theories. [ABSTRACT FROM AUTHOR]

This article proposes a novel approach for extracted pole (EP) filter synthesis. The pole producing elements can be extracted without introducing phase shifters. It is made possible by extracting lowpass elements in the prototype without reducing the order of filter functions. Using the proposed elements as added redundancy, the nonideal effect in the physical model is absorbed by adjacent resonators. Those novel approaches break through the conventional framework in EP filter synthesis. The synthesized results do not introduce extra spikes caused by nonideal phase shifters in the conventional EP filters. The new theory enables the application of EP filters in broadband situations. This work also reveals the equivalence between the frequency-dependent couplings and the PPEs. The validity of the demonstrated method is illustrated via an 11-pole filter with two transmission zeros. The simulated and measured results have no extra spikes caused by the nonideal phase shifters, which verified the effectivity of the proposed theory. [ABSTRACT FROM AUTHOR]

This article presents a fully integrated 12-channel multiplexer with TE011 mode channel filters enabled by the unified extracted pole technique. A novel synthesis procedure is proposed to remove the limitation (a very small coupling) in the prototype with the classical approach. In addition, this article proposes a novel approach to assign the junction susceptance by simply shifting the length of the connecting waveguide section of the dangling resonators. The design process is then extended to the singly terminated case as the channel filter design. This work also proposes a novel analytical approach to derive the initial connecting phase lengths for the manifold multiplexer design. The circuit level optimization and space-mapping procedure for deriving physical dimensions are illustrated. The multiplexer is designed and constructed using a new clamshell structure, which offers low cost, small footprint, easy fabrication, and superior thermal performance. The simulated and measured results demonstrated that the proposed theory offers an excellent solution to the high-power waveguide manifold multiplexer designs. [ABSTRACT FROM AUTHOR]

This article studied the interference between two channels of a tunable diplexer and proposed a feasible solution to alleviate the effect. A novel approach to synthesize the channel filter with the first element replicating the other channel’s effect is first developed. It led a set of simple formulae for fixed frequency diplexer design. After that, a framework incorporating a redundant coupling path to generate cancellation effect is derived using the coupling matrix theory. The proposed theories are demonstrated and verified using a combline diplexer design. The simulated and measured results suggest that the interference of the two channels can be greatly mitigated. [ABSTRACT FROM AUTHOR]

This contribution establishes the relationship between the complementary condition and the singly terminated (ST) networks. The general theory is first presented in the form of bandpass/bandstop complementary diplexers. Furthermore, the well-known limitation of a complementary diplexer, i.e., using maximally flat prototypes, is overcome. From the first principle, it is rigorously proven that predefined complementary features can be obtained by connecting two channel filters in an ST prototype of the same filter function but exchanging the transfer and reflection part. This paper leads to a general design procedure for bandpass and bandstop complementary diplexers using arbitrary functions. A complementary diplexer design example with full electromagnetic simulated results and measured results verified the accuracy of the proposed theory. Finally, the theory is further extended to N-ports networks. A new “partially-complementary” condition is proposed. The new theory leads to an extremely simple and “direct approach” to estimate the performance of contiguous multiplexers without any optimization. [ABSTRACT FROM AUTHOR]

This paper proposes a novel and unified synthesis approach and design procedure for microwave filters with extracted pole and nonresonating node (NRN) technique. By introducing a general circuit topology, the traditional extracted pole and NRN filters can be unified to a general prototype. With the new design process, the exact mapping relationship between the electromagnetic (EM) model of the pole producing element and the circuit model can be achieved. All the physical dimensions of the filter structure can be obtained by a fully analytical approach. No full EM optimization or adjustment is needed in the filter design. A three pole TE \mathrm { {101}} mode waveguide filter with one finite transmission zero is designed to illustrate the new procedure. In addition, a seven-pole TE \mathrm { {011}} mode filter with four finite transmission zeros covering all three possible types of arrangements is designed and fabricated to demonstrate the versatility of the proposed method. The simulated and measured results verified the efficiency and the accuracy of the proposed design method. [ABSTRACT FROM AUTHOR]

This article offers a novel approach to realize dual-polarized diplexers (DPDIPs), which can duplex horizontally and vertically polarized signals separately. The proposed device is composed of a turnstile junction (TJ) and four-channel filters. Compared with conventional orthomode transducer (OMT) and two diplexers scheme, it has an ultracompact size and comparable performance. A new arrangement for the TJ that is suitable for the DPDIP is analyzed and simulated accordingly. A Ka-band DPDIP is designed and fabricated as a verification example. Simulated and measured results have verified the accuracy and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

This article proposes a computer-aided tuning approach for Butler matrices (BMs). It is implemented in two stages. First, extract the amplitude imbalance of each individual coupler from the overall BM measurement results using the proposed diagnosis procedure. The extracted results led to the instructions for fine adjustments. After that, each coupler is adjusted using the proposed method. As a result, the nonideal effect of a BM can be tuned out to achieve significant performance improvement. An $8 \times 8$ BM was designed, fabricated, and tuned using the proposed approach. The final results show excellent amplitude imbalance performance, which is improved by more than 80% relative to the initial results. For the first time, a systematic tuning method is demonstrated to achieve excellent amplitude imbalance for a BM. [ABSTRACT FROM AUTHOR]