This paper presents a methodology to design band-pass filters having ultrawide stopband characteristics using multilayer circular substrate-integrated waveguide (SIW) cavities. The orthogonal microstrip feedlines are used as input and output ports that are present at the top and bottom layers, while the middle layers are used to couple the SIW cavities. Higher-order spurious modes of the circular SIW cavity are suppressed by using orthogonal feeding mechanism and properly adjusting the arc-shaped slots between the cavities. To validate the present approach, two filters (second- and fourth-order) have been designed and fabricated and their characteristics are measured. The second-order filter exhibits a stopband rejection below 25 dB up to nearly 5.07f0, while the fourth-order filter has a stopband characteristic of nearly 5.05f0 with 20 dB rejection. The filters allow only TM010 mode propagation and attenuate the higher-order spurious modes of the cavity.

This paper presents the application of a substrate-integrated waveguide (SIW) for the design of a leaky-wave antenna (LWA). The antenna radiates through a wide slot in the top wall of the SIW structure in the forward direction. The effective width of the slot is varied by changing capacitances of two arrays of varactors connected between slot edges and inserted conducting strips. The radiation pattern of the antenna is by this way controlled by DC bias, which sets the capacitances of varactors. The maximum radiation direction in elevation can be varied within 35° by changing the DC bias from 2 to 12 V. This elevation angle is measured from the broad side direction perpendicular to the antenna substrate. The measured antenna characteristics are in accord with those predicted by simulation. The antenna can be simply fabricated by a planar circuit board technology.

We present a tunable planar groove gap waveguide (PGGWG) resonant cavity at Ka-band. The cavity demonstrates varactor loading and biasing without bridging wires or annular rings, as commonly is required in conventional substrate-integrated waveguide (SIW) resonant cavities. A detailed co-simulation strategy is also presented, with indicative parametric tuning data. Measured results indicate a 4.48% continuous frequency tuning range of 32.52–33.98 GHz and a Qu tuning range of 63–85, corresponding to the DC bias voltages of 0–16 V. Discrepancies between simulated and measured results are analyzed, and traced to process variation in the multi-layer printed circuit board stack, as well as unaccounted varactor parasitics and surface roughness.

Substrate-integrated waveguide (SIW) technology has recently drawn attention to its benefits in the microwave field, such as integration in planar microwave circuits, low manufacturing cost, and high-quality factor compared to other technologies. In this paper, a broadband and high gain SIW cavity-backed L-shaped slot antenna structure has been designed and made for X-band applications. Three pairs of L-shaped half-wave resonators are placed on the lower wall of the cavity (backed-slots) to further expand bandwidth and improve gain. The final antenna designed operates on a band ranging from 9.4 to 10.5 GHz with a bandwidth of 11%. Moreover, the gain reaches a value of 9.5 dBi. The final antenna is realized on a Rogers RT/Duroid 5870 substrate. The gain, the reflection coefficient, and the radiation patterns are measured and compared to the EM simulation results and a very good agreement is obtained. The proposed cavity-backed L-shaped slot antenna gives a good compromise between a high gain and a large bandwidth.

Demands for very high-speed wireless communication access is rapidly growing with respect to the increasing data rates for the use of rich multimedia content in various applications of defense, enterprise, industrial, and public domains. To serve these gigabit fidelity (Gi-Fi) uses for various wireless applications, millimeter wave (MmW) wireless technology with huge bandwidth in licensed/unlicensed bands is triggering boundless avenues. In this research, the concept of substrate-integrated waveguide (SIW) and exponentially tapered slot (ETS) antenna are used together design a high-gain, efficient planar dielectric-loaded antenna for MmW-based Gi-Fi wireless communications using unlicensed 60 GHz band in the MmW family. The SIW is used to feed the antenna and a dielectric is utilized increasing the gain. The dielectric-loaded ETS antenna and compact SIW feed are fabricated on a single substrate, resulting in low cost and easy fabrication utilizing printed circuit board process. The measured gain of single-element antenna is 11.4 dB, with radiation efficiency of 96.84% at 60 GHz. Then indoor radio wave propagation studies are carried out using elliptically dielectric-loaded ETS antenna with radio frequency measurement equipment to measure and model propagation channels at 60 GHz. The attained simulations are compared with the experimental results.

This paper presents a study of losses in substrate-integrated waveguides (SIWs) and cavities. Three mechanisms of losses are considered and separately investigated, namely radiation leakage, ohmic loss, and dielectric loss. A systematic comparison of waveguides with different geometry, operating at different frequencies, is reported. This study permits to give a physical interpretation of the loss mechanisms and to identify design criteria to minimize losses. A similar analysis is also developed in this work for the case of SIW resonant cavities. For these structures, a different variation of losses with respect to frequency is found, which reduces the effectiveness of the design criteria established for SIWs.