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1 ISSUED rev.01

2 CPE group provides its customers with a complete set of RF cable assemblies flexible, semirigid, corrugated, conformable, phase matched compliant with the more stringent industry specifications. Nowadays the microwave world needs a lot of phase matched coaxial cable sets. CPE group, thanks to the excellence of its RF lab and production line, has the capability to manufacture high volumes of tightly controlled phase matched coaxial cables. Due to the inevitable variations in connector and cable manufacturing process and assembly, phase matching can be considered an art more than a technology and requires the great experience of our in-house designers and state of the art RF instruments. Both these factors allow to obtain a wide variety of phase matched cable assemblies compliant with the customer s specifications at competitive costs. Applications Phased Array Radars Multi-Beam Antenna Arrays RF Combiners and Filters High Power Amplifier / Multi Channel Amplifier Features and Benefits Customized cable assembly design & development Max operating frequency equal to 26.5 GHz Wide temperature range Any type of cable and connector series Cable pairs or sets Different complex shapes Delay line and coils

3 Considerations about phase matched coaxial cable assemblies Many modern microwave applications require cable assemblies with the same electrical length, also named phase length. Because it is impossible to have zero phase tolerance among cables in the same set, that cables are manufactured with a reasonable match tolerance in phase, depending on the frequency range of operation, the cable length, the velocity of propagation, the temperature, the bending and the connectors used. Phase matching can be absolute, if the cable phase is compared with a defined value, or relative, if the cable assemblies in the same set are matched to each other. Phase matching is specified as electrical delay in time (typically nanoseconds) or degrees at a specified frequency of operation. A typical phase match is ± 1 /GHz for semi-rigid cables and ± 2 /GHz for flexible cables. An electrical delay can be converted into a physical length, in particular when the cable is very stable and consistent. To obtain the phase matching, it is usually convenient to specify the desired electrical match and the minimum mechanical length, where the length is the variable used to matching the phase. Frequency range of operation At higher operating frequencies it is more difficult to achieve a close phase match. Tight tolerances will require tight physical cut tolerances and increased manufacturing efforts and costs. Cable length The phase matching is very difficult when long cable assemblies are used. In this case wider phase match windows are needed and tighter phase tolerances are obtained with increased manufacturing efforts and costs. Velocity of propagation The velocity of propagation Vp of a cable is expressed as a percentage of the velocity of the light in the free space. It is inversely proportional to the square root of the relative dielectric constant of the cable. Higher Vp cables are longer for a given electrical delay, while lower Vp cables are shorter. A tight control of Vp eases the phase matching process, providing cables with more similar physical length. Tab. 1 provides a list of common dielectrics, their delay and Vp. Dielectric Delay [ns/ft] Vp [%] Solid PE Foam PE Foam PS Air space PE Solid PTFE Tape wrap PTFE Air space PTFE Tab. 1: List of common dielectrics with related delays and Vp Note that cables with solid dielectric cores and lower Vp are in general mechanically strongest, but they have greater insertion loss and phase changes as a function of temperature. Cables with high air content and higher Vp are mechanically weaker, but they have low insertion loss and excellent phase behavior vs. temperature 3

4 Small changes in Vp have a great impact on the electrical length of the cables. As an example, let s consider a 3 m long cable assembly at 18 GHz with nominal Vp = 82%. Let s suppose that, due to manufacturing and material variations, Vp ranges from 81% to 83%. At f = 18 GHz the wavelength ʎ in the free space is ʎ = c/f = m, where c = 3*10 8 m/s is the speed of light in the free space. The effective wavelength ʎ c in the coaxial cable is ʎ c = Vp* ʎ. When Vp = 82%, it is ʎ c = m and the electrical length of the 3 m long cable is equal to 219 wavelengths, that means degrees almost (note that one wavelength corresponds to 360 degree phase shift). Reducing Vp at 81 %, we obtain ʎ c = m, while the electrical length of the cable becomes wavelengths, that means degrees almost. Increasing Vp at 83 %, we obtain ʎ c = m, while the electrical length of the cable becomes wavelengths, that means degrees almost. In these conditions the phase matching requires a length tolerance of ± 4.4 cm. Temperature The electrical length of a coaxial cable changes with temperature. This change is given in parts per million per degrees centigrade [ ppm / C ]. Fig. 1 shows the not linear temperature dependence of the phase change of cables with different velocities of propagation. Fig. 1: Phase change vs. temperature for coaxial cables with different Vp Note that higher Vp cables, smaller phase changes over the most temperature range. It is evident that the phase matching of cables of the same set has to be made in a temperature controlled area. Other The connectors at the ends of the cables influence the cable phase matching: it simpler to phase match cable assemblies with the same connectors on both ends than assemblies with different connectors, due to the higher phase uncertainty introduced by different connectors. A tighter cable bend radius increases phase change and increasing the number of flexures on the cables also increases phase change. Consequently fixtures simulating the installation cable bends have to be used during the matching process. Methods for phase matching CPE group uses different methods for phase matching sets of cables: matched to a standard matched to other cables in the same set custom

5 Matched to a standard The phase standard consists of a gold hardware standard, that means a defined and known electrical length in degrees at a given frequency and temperature. If the assemblies are phase matched to a gold standard, they are interchangeable. Fig. 2 shows a CPE phase matched assemblies (UFB 311A cable terminated with SMA in one side and TNC on the other) using a gold standard. The length of the standard is 8.05m and the requested phase matching is ±5 up to 16GHz. The measurement has been made at a controlled temperature of 25 C. Fig. 2: Example of CPE matching to a gold standard Matched to other cables in the same set Cable assemblies matched in a set are only guaranteed to be matched to other cables in the same set. Due to the fact that phase between two sets can differ substantially, co-mixing cables have to be avoided. This method increases yields, lowering the cost. Custom Phase matching to a standard provided by the customer, or providing cable assemblies with defined phase offset with respect to each other, or following customer requests. Phase tracking The ability of the coaxial cable assemblies to tightly reproduce their phase characteristics with respect to each other over a range of temperature, bending, flexure is known as phase tracking. Essentially the phase tracking measures the mechanical consistency of the assemblies. The phase tracking due to the temperature changes is optimized if all the cables in the set are in the same thermal environment. Thermal cycling artificially ages the cables or stabilizes them, improving tracking characteristics. 5

6 CPE WORLDWIDE TEXAS - USA COMMERCIAL OFFICE USA - TEXAS COMMERCIAL OFFICE MILANO - ITALIA HEAD QUARTER PASTORANO - ITALIA SLATINA - ROMANIA DELHI - INDIA COMMERCIAL OFFICE WUXI - CHINA CURITIBA - BRAZIL CPE Italia S.p.A. Componenti professionali per l elettronica HEADQUARTER Via D. Chiasserini, Milano - Italia Tel Fax Our subsidiaries : CPE do Brasil Ind.& Com. Ltda Rua Inaja, 698 Vila E. Perneta BR PINHAIS-PR/ Brasil Tel Fax CPE East Europe (C.G.B.) Sos Draganesti, Km. 4 Loc. Slatina, Jud.Olt (Romania) Tel Tel CPE Wuxi Electronics Ltd. Xi Nan Road (Xue Lang, Ban Qiao) Bin Hu District, Wuxi City, Jiang Su, P.R.China, Tel. +86(0) Fax +86(0) CPE India Private Limited: Registered Office : 405/406 AKD Tower, Sector 14 Gurgaon Haryana Tel all rights reserved of CPE Italia S.p.A.