Haiyan Jin

Slow-Wave Effect of Substrate Integrated Waveguide Patterned With Microstrip Polyline

A class of slow-wave substrate integrated waveguide (SIW) structures patterned with microstrip polyline is presented, theoretically studied, and experimentally validated, which demonstrates some interesting slow-wave propagation effects. The slow-wave SIW (SW-SIW) enables the size reduction of a physically large circuit without sacrificing its performance. A size reduction of 40% of the lateral dimension is achieved with reference to that of the conventional SIW counterpart at the same cutoff frequency. Meanwhile, the phase velocity of the waveguide is also reduced by 40%, resulting in a smaller longitudinal dimension for a given electrical length. Both lateral and longitudinal effects give rise to a total size reduction, largely extending the operation range of SIW structures in the low-frequency region, which has often been restrained by a physical dimension-related cutoff frequency. Also, a transmission line-based two-dimensional (2-D) equivalent-circuit model is proposed and deployed for the modeling and analysis of the slow-wave mechanism. The results from the equivalent-circuit model agrees very well with that from the full-wave simulations. Furthermore, a broadband microstrip to SW-SIW taper with good return loss is designed for measurement verification. Using the proposed SW-SIW structure, the size of conventional SIW-based microwave circuits such as power splitters, couplers, and filters can be further reduced in addition to the existing size-reduction techniques.

Novel UWB BPF with a controllable notched band using hybrid structure

In this letter, an ultra-wideband (UWB) bandpass filter (BPF) based on CPW-to-microstrip transition structure is proposed. To improve its selectivity, an interdigital coupled-line and split ring resonator (SRR) are used to generate two extra transmission zeros located at the lower and upper edge of the passband separately. The measured results show that the proposed filter possesses satisfactory performance such as compact size, sharp roll-off, and wide fractional bandwidth of 133 % (2.35-11.75 GHz). Moreover, a notched band with deep attenuation introduced by coupling T-shaped short stub (CTSSS) is achieved to block the ITU8.0 band with centre frequency of 8.2 GHz. And the notched band is controllable. This filter can be a good candidate for ultra-wideband applications.

Miniaturized Broadband Coupler Made of Slow-Wave Half-Mode Substrate Integrated Waveguide

In this work, a size-reduced wideband coupler is presented and demonstrated, which explores the slow-wave half-mode substrate integrated waveguide (SW-HMSIW) technique on a printed circuit board process. The SW-HMSIW coupler is composed of two SW-HMSIW transmission lines loaded with a polyline network. Along the coupler, energy is coupled by the electric and magnetic field between the two parallel SW-HMSIW lines. Compared with conventional microstrip coupler, the proposed coupler presents lower loss owning to the HWSIW structure performance. In addition, the proposed SW-HMSIW coupler exhibits a smaller size against its SIW and HWSIW counterparts, thanks to slow-wave effects of the loaded polyline. Measured and simulated results are in a good agreement.

Substrate-Integrated Waveguide Power Combiner/Divider Incorporating Absorbing Material

In this letter, substrate-integrated waveguide (SIW) power combiner/divider incorporating absorbing material for isolation is presented. Based on the Riblet coupler theory, the proposed SIW power combiner/divider contains two extra ports to improve isolation between the dividing ports. Its longitudinal axis symmetry illustrates its equal power-dividing property, and ensuring the dividing ports to have good and balanced amplitude and phase properties. By loading the isolated ports with shaped absorbing material, an SIW power combiner/divider prototype is realized. Measured results are in good agreement with simulated ones, and a fractional bandwidth of 36% with over 15-dB isolation is achieved, which is wider than other similar SIW power dividers.

Small-reflected substrate integrated waveguide termination with multi-step shape and absorbing material

A planar wideband substrate integrated waveguide (SIW) termination with multi-step shape and absorbing material is reported. Early reported absorbing material based SIW terminations exhibit fractional bandwidth (FBW) less than 45%. To broaden bandwidth, the multi-section stepped-impedance transformation is introduced into the design of SIW termination based on the theory of small reflection. The multi-step shape such as trident is used to mold the absorbing material, so that the impedance matching between the substrate and absorbing material can be improved and achieve a wider bandwidth. Measurement of the fabricated prototype exhibits a FBW over 70% with return loss better than 17dB, as well as system integration capability and low structure complexity.

Miniaturized dual-band filters based on quarter-mode substrate integrated waveguide loaded with double-sided stepped-impedance complementary split-ring resonators

This paper presents two miniaturized dual-band filters based on quarter-mode substrate integrated waveguide (QMSIW) loaded with double-sided stepped-impedance complementary split-ring resonator (DS-SICSRR). The modified SICSRRs, realized by employing the stepped-impedance concept into the conventional CSRR, are with longer electrical lengths and thus exhibit more compact size as compared with its corresponding conventional CSRR counterpart. Subsequently, by loading the SICSRRs with different sizes into the two sides of the QmSIW cavity, two cavity resonators with dual-band response are realized. Since sizes of the SICSRRs on the two sides are tuned independently, the two passbands of the proposed resonator can be controlled flexibly. Based on the proposed QMSIW-DS-SICSRR cavity resonators, two dual-band bandpass filters are implemented, with their measured results in good agreement with the simulated ones. Compared with some related works, the two proposed dual-band filters exhibit size-reduction about 52% and 64%, as well as more controlling flexibility of the two passbands.

Slow-Wave Propagation Properties of Substrate Integrated Waveguide Based on Anisotropic Artificial Material

In this paper, an inductor-loaded slow-wave substrate integrated waveguide (SIW) is presented and studied. The proposed structure features a number of unique propagation properties. First of all, the inductance value imposed along the transverse direction will affect the phase velocity and cutoff frequency of the waveguide simultaneously. Second, the inductance value in the longitudinal propagating direction will only affect the phase velocity but make no difference on the cutoff frequency. Based on the aforementioned characteristics, the size of structure could be controlled by separately tuning the loaded inductor along the transverse direction and longitudinal propagating direction. More importantly, it is released on the interrelationship between the phase velocity and cutoff frequency in the proposed guiding-wave structure. The feature will be beneficial to the design of leaky-wave antenna and matching circuits for SIW circuits. Finally, experimental results demonstrate that with the increasing of loaded inductance, a reduction of 35% in cutoff frequency is achieved compared with the conventional SIW counterpart. The phase velocity is also reduced by 35% with the increasing of the loaded inductor, which contributes to a miniaturized longitudinal dimension for a given electrical length.