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In this Letter, a simplified design approach for zero‐bias power detectors suited for integration in six‐port receiver architectures is presented. The proposed concept uses the quadrature hybrid coupler as an effective way to improve the input impedance matching and linearity performance. The proposed solution has been experimentally validated through its implementation into a 60 GHz six‐port receiver prototype to investigate its performance in detecting various M‐ary quadrature amplitude modulation (M‐QAM) signals. The obtained measurement results show a high accurate and linear detection responses for all investigated M‐ary QAM modulation techniques (4‐QAM, 16‐QAM, 32‐QAM). The variation in the error rates of the demodulated signals at the adjacent differential outputs is minimal (<1%), and the maximum error rate achieved does not exceed 5%. The obtained precision and linearity performances make the proposed structure highly suitable for the emerging millimetre‐wave six‐port receiver front‐ends. [ABSTRACT FROM AUTHOR]

An air‐filled substrate integrated waveguide (AFSIW) slot array antenna based on multilayer PCB process is proposed. For comparison and demonstration purposes, 1 × 4 slot array antennas based on both AFSIW and conventional dielectric‐filled SIW (DFSIW) operating at 30.5 GHz are designed, fabricated and measured. The exampled AFSIW 1 × 4 slot array antenna achieves 44 and 18% narrower measured H‐plane and E‐plane half‐power beamwidth, respectively, and simulated radiation efficiency improved by 1.6%, resulting in an overall measured gain improvement of 3.5 dB compared with its DFSIW counterpart. This antenna is of high interest for the design of efficient arrays based on high‐performance AFSIW feeding network. [ABSTRACT FROM AUTHOR]

Variable propagation constant directional coupler is proposed and demonstrated. Compared with its conventional counterpart, the proposed coupler uses variable waveguide propagation constants as an extra degree of design freedom to achieve the required signal addition and cancellation. The operation principle is mathematically formulated and a step‐by‐step design methodology is presented. Two double‐layer two‐hole substrate integrated waveguide couplers: namely, one forward directional coupler and one backward directional coupler, are fabricated to validate the proposed concept. A coupling of −20 dB is achieved in both couplers and the maximum isolation of −47 and −52 dB are obtained by the forward and backward structures, respectively. [ABSTRACT FROM AUTHOR]

A substantial reduction of substrate integrated waveguide (SIW) insertion loss can be achieved through the use of air as dielectric instead of usual dielectric material. However, air‐filled SIW (AFSIW) circuits exhibit larger footprint compared with their dielectric‐filled counterparts. A compact multilayer AFSIW bandpass filter is proposed to realise both high‐performance and small footprint. For demonstration purpose, a Ka‐band multilayer fourth‐order AFSIW bandpass filter has been designed and fabricated. Measured and simulated results are in good agreement. Retro‐simulations, taking into account fabrication tolerances, are also presented. Finally, a performance comparison with other multilayer technologies is presented. [ABSTRACT FROM AUTHOR]

A substrate‐integrated waveguide (SIW) broadband phase shifter is presented and studied. The phase shift mechanism is based on the synthesis of an artificial dielectric slab using an array of metallic rods in the middle of a SIW. This technique enables a large phase shift within a compact size and enhances the density of integration. As an example, 45° and 90° phase shifters are designed and showcased on a single‐layer substrate at a centre frequency of 26 GHz. The amplitude imbalance between the two paths is also avoided while the phase error is less than 5° over a frequency band of 20–32 GHz or around 46% relative bandwidth. The measured return loss is found to be better than 12 dB over the whole frequency band. [ABSTRACT FROM AUTHOR]

An edge‐guided mode isolator based on substrate integrated waveguide (SIW) technology is presented. A matching transition section from a ferrite isolator in a SIW to a microstrip is introduced and developed. Supporting experiments have been conducted to confirm the predicted performance of the new structure. [ABSTRACT FROM AUTHOR]

A type of substrate integrated waveguide (SIW) 'corner cavity' is proposed. For each corner cavity, two transmission zeros (TZs) can be introduced and the location of either TZ can easily be controlled by adjusting suitable geometrical parameters. Using the corner cavities, a novel SIW filter with wide stopband characteristic is implemented. The central frequency of the filter is 20 GHz, and the first spurious appears at about 40 GHz, which is two times the central frequency. In addition, the measured stopband attenuation of the filter is better than 50 dB from 21.24 to 37.71 GHz. [ABSTRACT FROM AUTHOR]