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A dual-layered six-port front-end circuit on the basis of substrate-integrated waveguide (SIW) technology is presented and demonstrated. The use of SIW technology allows the development of a compact circuit with low radiation loss at millimetrewave frequencies. The six-port architecture makes use of multilayer couplers that provide a wide coupling area through two slots; a new broadband SIW phase shifter composed of two H-plane stub lines and a reference line; and two SIW power dividers. The six-port design is free from loads as in the case of classic modified six-port architectures with eight ports. To validate the proposed concept, an integrated broadband six-port front-end circuit prototype was designed, fabricated and measured. Simulation and measurement results show that the proposed six-port circuit can easily operate at 60 GHz for V-band system applications. The two-layered structure presents interesting technological features including low profile, small volume and footprint and highdensity integration. [ABSTRACT FROM AUTHOR]

A Butler beam-forming network with low sidelobe level (SLL) is proposed and demonstrated on the basis of variable couplers. A set of couplers with 0.75, 1.26, 3, 6 and 8 dB coupling levels are required to achieve an SLL of -13.6, -20 and -30 dB. Such variable coupling is achieved by creating a movable mirror structure in the common region of perpendicularly or cross-coupled waveguide building blocks. This mirror is composed of a 5×7 cylindrical rod array. The coupling and directivity characteristics depend on the position of this proposed fringe structure. In this work, WR28 is used to demonstrate the capability of this type of coupler over 26-30 GHz bandwidth. Structure usefulness and design procedure are validated by electromagnetic simulation high frequency structural simulator (HFSS) and prototype experimentation. Very good results are observed, that have also demonstrated attractive performances of the coupler. Measured results of couplers are used to assess the properties of Butler matrix with excitation coefficients corresponding to -13.6, -20 and -30 dB of SLLs. Radiation patterns obtained by this investigation show a promising performance. This proposed technique allows flexibility in the choice of excitation coefficients without degradation on the efficiency. [ABSTRACT FROM AUTHOR]

A new balanced oscillator is proposed to generate anti-phase sources at Ku band. The proposed oscillator is stabilised with the TE210 differential mode of a single planar substrate integrated waveguide (SIW) rectangular cavity with mutually locked dual anti-phase outputs. The unloaded-Q of this resonator extracted through mixed mode S-parameters is 370 at 14 GHz. The differential coupling mechanism is presented and the coupling coefficient is parametrically studied. The proposed balanced oscillator provides 6.9 and 7.2 dBm output power for each balanced output with a phase noise of -101 dBc/Hz at 100 kHz offset measured at 14 GHz. The amplitude and phase balances of the two output signals are verified with measurement. The combined differential output power is 10.8 dBm and the phase noise is -109 dBc/Hz at 100 kHz offset. [ABSTRACT FROM AUTHOR]

Substrate-integrated waveguide (SIW) technology represents an emerging and very promising candidate for the development of circuits and components operating in the microwave and millimetre-wave region. SIW structures are generally fabricated by using two rows of conducting cylinders or slots embedded in a dielectric substrate that connects two parallel metal plates, and permit the implementation of classical rectangular waveguide components in planar form, along with printed circuitry, active devices and antennas. This study aims to provide an overview of the recent advances in the modelling, design and technological implementation of SIW structures and components. [ABSTRACT FROM AUTHOR]

A novel class of substrate-integrated waveguides (SIWs) is presented, based on the concept of the classical ridge rectangular waveguide, which permits the design of broadband, compact and low-loss integrated components and interconnects. Two configurations are proposed. The former is the ridge SIW, where the structure is integrated in a dielectric substrate with top and bottom metal layers, and comprises two-sided rows of full-height metal cylinders and a central row of partial-height metal posts connected at their bottom by a metal strip. The latter is the ridge substrate-integrated slab waveguide; this structure presents a geometry similar to the ridge SIW, but includes additional air holes to further enhance the bandwidth. The design and experimental verification of two prototypes, covering the frequency band from 6.8 to 25 GHz and from 7.1 to 30.7 GHz, respectively, are also presented. The proposed structures exhibit a mono-modal bandwidth three times broader than classical rectangular waveguides or SIWs, and their size is half of the SIW with the same cut-off frequency. [ABSTRACT FROM AUTHOR]

This study presents a novel approach for designing broadband single layer printed log-periodic dipole array (PLPDA) antenna fed by substrate integrated waveguide (SIW). The PLPDA antenna has the merits of wide bandwidth, low profile and light weight, which should be fed by the balanced line. The balanced line, created by the geometric features of the SIW, provides a balun with a considerably wide bandwidth with low profile, broad dominant mode bandwidth, low insertion loss and so on. Prototype of the proposed substrate integrated printed log-periodic dipole array (SIPLPDA) antenna and 1×4 antenna array at Ka band are designed and fabricated; the measured data are in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

In this study, a new type of substrate integrated waveguide (SIW) beamforming network (BFN) based on the principle of the modified R-KR lens has been proposed and experimentally verified. Through the detailed analysis of such a structure, a prototype lens with 15 input ports is implemented together with an SIW slot array antenna at 30 GHz, which is able to cover a wide angle of (-59°, 59°) with its 3 dB beam-width. The measured radiation efficiencies of the lens excited at different ports range from 21.6 to 40.8%. This type of BFN takes the advantages of low profile, low cost and high performance, and may be applied to millimetre-wave mobile communications and radars with beam switching technology. [ABSTRACT FROM AUTHOR]

A Ka-band sub-harmonically pumped up-converter antenna employing the substrate integrated waveguide (SIW) technique is proposed and used to realise a low-cost transmitter together with spatial power combining architecture in this paper. A single Ka-band sub-harmonically pumped up-converter using SIW band-pass filter is developed, exhibiting a conversion loss of about 7 dB. Based on the designed up-converter and SIW feeding antipodal linearly tapered slot antenna (SIW-ALTSA), the integrated up-converter antenna is designed and fabricated. Measured results of equivalent isotropic radiated power (EIRP) and radiation patterns are given. Finally, a 2×2 up-converter antenna array is designed and fabricated. Measured result shows the array has a power combining efficiency of above 90% and IM3 EIRP of 16 dBm. In close-range point-to-point communication and radar systems, the demonstrated millimetre-wave sub-harmonically pumped up-converter antenna array can be considered as a transmitter because of its low cost, high dynamic range and high linearity. [ABSTRACT FROM AUTHOR]

Wave radios in the past have used passive wide-band with no multiple access (MA) coded interferometer architectures in modulator and demodulator circuits for QPSK digital data transmission and reception. The authors provide information and design insight on the use of MA coded interferometers in modulator and demodulator for UWB wave radio. Wave radio fitted with hardware MA coded interferometers offers MA to users as does CDMA using data codes. Experimental and simulation analyses of coded interferometers show that it is possible to establish a one-to-one wave radio hardware link by means of hardware-based codes (addresses). The number of UWB hardware-coded interferometers investigated is limited to three codes (code 0, code 1 and code 2) for demonstration purposes only. [ABSTRACT FROM AUTHOR]

Low sidelobe longitudinal slot array antennas are investigated based on substrate integrated waveguide (SIW) technology. The design method consists of the characterisation of the radiating element, the synthesis of the linear array and the development of the planar array including a feeding power divider by performing full-wave electromagnetic simulations for the final accurate design. Two planar slot array antennas are fabricated with a normal printed circuit board (PCB) process. Low sidelobe features are verified by the measured results which are in agreement with the simulated results. For an 8×8 SIW slot array antenna, the measured sidelobe levels (SLLs) are below -36 dB in the H-plane and below -25 dB in the E-plane with the Gain of 20.3 dB at 9.9 GHz. And for a 16×16 antenna, the SLLs are below -30 dB both in the E-plane and H-plane with the Gain of 24.4 dB at 10 GHz. The achieved design goals on the radiation patterns therefore validate the proposed low sidelobe SIW slot array antennas to be valuable candidates for high performance communication and radar applications. [ABSTRACT FROM AUTHOR]

A tunable dual-band bandpass microstrip filter is proposed and presented. It is composed of two pairs of quarter-wavelength transmission line resonators and two bandstop structures made of open stubs. Each operation bandpass frequency, denoted by f1 and f2, is generated by a pair of coupled resonators. The first coupled resonator is fed via a tap-coupled structure, while the second is fed through a coupling structure. The tunability of each bandpass and harmonic suppression is achieved by modifying the electrical length of the resonators and the electrical length of the open stubs by using varactor-diode capacitors. Finally, a 2.5 and 4.25 GHz dual band bandpass filter is designed, fabricated and measured as one example and a tunability of 22.2% and 19.6%, respectively, is obtained for the first and second bands. These excellent experimental results validate the proposed structure and design technique for dual-band bandpass filters. [ABSTRACT FROM AUTHOR]

A new class of substrate-integrated waveguides (SIWs) is proposed, which highlights a novel synthesis of waveguide circuits using metallic via-slot arrays instead of via-hole arrays. When the gaps between the slots are small enough, the broadside dimension of equivalent rectangular waveguide is approximately equal to the spacing between the inner walls of slots. Therefore the size of the SIW can directly be used to calculate propagation constants almost without phase bias. This new design is of critical importance in the design of substrate-integrated circuits (SICs) with fine and sensitive geometrical details with respect to circuit response such as filters and resonators. In this way, the design of SICs based on the new SIW structures can greatly be simplified. A finite difference frequency-domain method accelerated by an implicitly restarted Arnoldi method is developed to model the substrate-integrated resonant cavities with leakage. Simulated and measured results have confirmed the fact that conventional waveguide components are very similar to the SIW counterparts of the same structure. [ABSTRACT FROM AUTHOR]

A compact planar E-plane monopulse antenna is proposed and realised at 36.5 GHz for millimetre-wave radar or direction-finding system application, which is built on the substrate integrated waveguide (SIW) technology. A phase shifter having a non-uniform SIW width configuration is self-consistently made of a periodically embedded via array and it can achieve good performances over a relative broad bandwidth. A 180° directional coupler incorporating this proposed phase shifter structure is developed in the design of an integrated feeding network for the monopulse antenna. Four elements array based on the configuration of antipodal linearly tapered slot antenna is designed as radiator, offering a pair of ‘sum’ and ‘difference’ beams along the long direction of the substrate. Measured gain of the ‘sum’ beam is higher than 16 dBi, whereas the zero depth of the ‘difference’ beam is lower than –38 dB. This type of monopulse antenna presents an excellent candidate in the development of intelligent millimetre-wave directional-finding system. [ABSTRACT FROM AUTHOR]

This paper proposes a dualband frequency-selective surface (FSS) based on substrate-integrated waveguide (SIW) technology. This novel dualband FSS is constructed using double square loop slots (DSLSs) and an SIW cavity. Its frequency performance is investigated by numerical simulation using the finite difference frequency domain (FDFD) method. Another dualband FSS, constructed using convoluted double square loop slots (CDSLSs) and an SIW cavity is also investigated in order to get close passband spacing. Simulation results show that these dualband FSSs have the advantages of higher selectivity and passband insensitivity to the incident angles and polarisations, compared with conventional multiband FSSs. Experiments are carried out to verify the simulated results, and the measured results show a promising performance of the proposed FSS. [ABSTRACT FROM AUTHOR]