Design and Development of 60 GHz Millimeter-wave Passive ...

Design and Development of 60 GHz Millimeter-wavePassive Components using Substrate IntegratedWaveguide TechnologyN. Athanasopoulos, D. Makris, K. VoudourisWireless Communications and e-Applications Research GroupTechnological Educational Institution of AthensAthens, Greecenathan@teiath.grAbstract—This paper overviews the design and development of aset of 60 GHz frequency band, millimeter-wave passivecomponents using Substrate Integrated Waveguide (SIW)technology. Two bandpass filters, a diplexer and a slot antennaarray are demonstrated. Simulation results show goodperformance according to the prescribed specifications. Thediplexer and the antenna are integrated on a common substrate,providing a fully integrated SIW millimeter-wave transceiverfront-end.Keywords-Substrate Integrated Waveguide; millimeter-waves;System-on-SubstrateI. INTRODUCTIONThe deployment of millimeter-wave (mm-wave) integrationtechnologies is critical for the wireless systems evolution in thenext few years. A variety of applications has been recentlyproposed in the frequency range between 60 GHz and 94 GHzincluding wireless networks [1], automotive radars [2],imaging sensors [3], and biomedical devices [4]. These mmwavesystems require cost-effective technologies suitable formass-production and high density integration techniques,combined with a low-cost fabrication process.Substrate Integrated Waveguide (SIW) technology [5]-[8]is a candidate for providing compact, easy to fabricate, flexibleand cost-effective mm-wave circuits and systems whichpreserve most of the advantages of the conventional metallicwaveguides namely complete shielding, low loss, high qualityfactorand high power-handling capability [9]. Most of theclassical passive components have been implemented in SIWtechnology providing components with a substantial reductionin size if compared to classical waveguide components;moreover, their losses are lower than in the correspondingmicrostrip devices, especially in the millimeter-wave frequencyrange, and there are no radiation and packaging problems. Acomplete overview of the SIW components that have beensuggested in literature is given in [9].One of the major advantages of SIW technology is thepossibility to fabricate a complete circuit in planar form(including planar circuitry, transitions, rectangular waveguides,active components and antennas) using a standard printedcircuit board. Moreover, there is the possibility to mount one ormore chip-sets on the same substrate. There is no need oftransitions between elements fabricated with differenttechnologies, thus reducing losses and parasitics. In this way,the concept of System-in-Package (SiP), widely adopted in thedesign of RF circuits, can be extended to the System-on-Substrate (SoS) [10], [11]. SoS represents the ideal platform fordeveloping cost-effective, easy-to-fabricate and highperformancemm-wave systems.In this research a set of mm-wave passive components aremodeled in SIW technology. Analytically, a pair of 5 th order,60 GHz bandpass filters are designed and been simulated first.These two filters are then combined in order to form a SIWdiplexer. An 8x8 SIW slot antenna array operating at the 60GHz band is then designed and simulated. Finally, diplexer andantenna are integrated in a common substrate providing a fullyintegrated SIW millimeter-wave transceiver front-end.II. THE 60 GHZ SIW GENERAL STRUCTURESIW structure is fabricated by using two periodic rows ofmetallic vias connecting the top and bottom ground planes of adielectric substrate. The top-side of a general SIW structure isdepicted in Fig. 1.α siwFigure 1. The SIW structure top-side.SIW width, α siw , is calculated based on the correspondingrectangular waveguide width, α:αSIWα effα=εwhere ε r is the substrate dielectric constant. SIW effectivewidth, α eff , is calculated based on equation [7]:r(1)p vd v

2 2dvdvαeff = αsiw−1.08⋅ + 0.1⋅ (2)pvαsiwVia diameter d v and pitch via p v should be appropriately setin order to ensure that there is no radiation leakage betweenmetallic vias due to diffraction. In [12], the following designrules are given in order to avoid such effects:andd vλg< (3)5p ≤ 2d(4)vIn this research, pitch via and via diameter are set equal top v =0.35 mm and d v =0.2 mm respectively. Dielectric substrateRogers RT/duroid 5880 (ε r =2.2, dielectric thickness h=0.508mm) is considered. The 60 GHz frequency band rectangularwaveguide (WR-15) width is α=3.759 mm. Applying (1), SIWwidth is calculated, while, based on (2) SIW effective width isalso calculated. All SIW basic design parameters for the 60GHz frequency band are summarized in Table I.vFigure 3. Simulation results for the 59.8 GHz SIW bandpass filter.TABLE I. SIW DESIGN PARAMETERS AT 60 GHZDielectric Substrate: RT/duroid 5880Parameter(ε r =2.2, h=0.508 mm)Symbol Value UnitPitch Via p v 0.35 mmVia Diameter d v 0.2 mmSIW Width α siw 2.8 mmSIW Effective Width α eff 2.678 mmIII. 60 GHZ SIW BANDPASS FILTERSThe design methodology of the two SIW bandpass filtershas been analytically presented by the authors in [13]. Centerfrequencies for the two filters are 59.8 GHz and 62.2 GHzrespectively. Bandwidth is 1 GHz, and filter order is 5. Basedon these specifications, authors in [13] compute the designparameters of both filters. 50 Ohm SIW-microstrip transitionsare suitably designed in order to enable TE 10 modepropagation. Fig. 2 depicts the HFSS SIW bandpass filtermodel.Figure 4. Simulation results for the 62.2 GHz SIW bandpass filter.IV. 60 GHZ SIW PLANAR DIPLEXERAuthors in [14] presented the 60 GHz planar diplexer inSIW technology which is developed by the integration of thetwo 5 th order SIW bandpass filters been presented in theprevious section. Integration is achieved through a SIW T-junction which is designed so as TE 10 mode to be propagated,and incident electromagnetic waves at channel filters’ ports tobe equal-amplitude and in-phase. 50 Ohm SIW-microstriptransitions are also designed for all diplexer ports. The SIWplanar diplexer HFSS design is presented in Fig. 5.Figure 2. HFSS model for the 5 th order SIW bandpass filter.Fig. 3 presents the HFFS simulation results for 59.8 GHzbandpass filter. Insertion loss is about 2 dB while return lossvaries below 20 dB for the 1 GHz pass band. Filter rejection at62.2 GHz is 66 dB. Fig. 4 shows the HFFS simulation resultsfor 62.2 GHz bandpass filter. Insertion loss is 1.5 dB whilereturn loss varies below 20 dB for the 1 GHz pass band. Filterrejection at 59.8 GHz is 90 dB.Figure 5. The 60 GHz SIW planar diplexer HFSS model.Fig. 7 shows the common port (Port 1) return loss, thetransmission responses as well as the channel-to-channelisolation, whereas Fig. 8 the channel filters’ return losses.According to the simulation the insertion losses are about 3.5dB for receive and transmit 1 GHz pass bands. Receive andtransmit out-of-band rejection is 52 dB at transmit and receive

filter center frequencies respectively while channel-to channelisolation varies below 60 dB. Finally, common port return lossas well as receive and transmit return loss vary below 12.5 dB.TABLE II.ParameterSlot Length8X8 SIW SLOT ANTENNA DESIGN PARAMETERSSymbolSLTheoretical OptimizedValue Value1.97 1.80UnitmmSlot Spacing SS 2.17 2.17 mmSlot to Top ST 3.25 3.00mmSlot Width SW 0.18 0.20 mmSlot Offset SO 0.15 - 0.25 0.18mmFigure 6. HFSS simulated transmission responses, isolation and commonport return loss for the diplexer.Figure 8. The 60 GHz 8x8 SIW slot antenna array HFSS model.Figure 7. HFSS simulated return losses for diplexer receive and transmitchannel filters.V. 60 GHZ SIW SLOT ANTENNA ARRAYAn 8x8 SIW slot antenna array was designed based onanalysis suggested in [15]. Feeding network at the input of theantenna divides the signal to 8 in-phase, equal amplitudesignals and a 50 Ohm SIW-microstrip transition is usedlikewise. The 8x8 SIW slot antenna array HFSS model ispresented in Fig. 8.Slot Spacing (SS) is equal to the half of guided wavelength λ gand Slot to Top (ST) is equal to the three-quarter of λ g shortcircuittermination. Slot Width (SW) varies between one tenthand one twentieth of SL, determining the desired bandwidth.The position of each slot relative to the centerline of each array(SO) is analytically described in [16]. Finally, Slot Length (SL)is computed based upon [17]. In Table II, both theoretical andoptimized using HFSS design parameters are summarized forthe 8x8 SIW slot antenna array.Fig. 9 shows the antenna return loss simulation results.According to that, S 11 varies below -10 dB in the range from58.6 GHz to 63 GHz covering the pass bands of the diplexerchannel filters been presented in previous section. Fig. 10shows radiation pattern simulation results. Beamwidth is 15.5 0and 10.7 0 in azimuth and elevation planes respectively. Thegain is 21.64 dB.Figure 9. HFSS simulated return loss at the input of the antenna.Figure 10. The HFSS azimuth and elevation radiation patterns.