Anritsu HFE0702_Kneeland 电路图.pdf

《Anritsu HFE0702_Kneeland 电路图.pdf》由会员分享，可在线阅读，更多相关《Anritsu HFE0702_Kneeland 电路图.pdf（2页珍藏版）》请在收音机爱好者资料库上搜索。

1、48High Frequency Electronics High Frequency Design MULTI-SIGNAL CABLES Another Look at Combined Microwave-Optical Cables and Connectors By Foster Kneeland Haverhill Cable & Manufacturing Corp. C ables that combine optical and micro- wave signal trans- mission have been avail- able for several years,

2、 but it seems that this is a good time for a review. With so many new wide bandwidth communica- tions systems, the ability to carry both types of signals on a single cable may have significant advantages. Figure 1 shows the construction of these cables. At the center is an optical fiber, sur- rounde

3、d by its cladding, which is then metal- lized on the outside. The metallization layer becomes the inner conductor of a coaxial cable. A typical coaxial outer conductor and dielec- tric material completes the cable. A number of design issues must be consid- ered when manufacturing this specialized du

4、al-mode cable: The optical fiber should be chosen for the application, whether single-mode, multi- mode with stepped index or multi-mode with graded index, with the desired wave- length and attenuation characteristics. To use standard coaxial cable materials and tooling, the outside diameter of the

5、optical fiber, after metallization, should be the same as a standard coaxial cable inner conductor (e.g. 0.011 in. diameter for a 0.047 in. semi- rigid cable.) The physical strength of the clad and metal- lized fiber, as well as its bending behavior, must be included when determining cable specifica

6、tions for pull strength, bending radius, repeated bending, etc. These charac- teristics can be significantly different from the typical copper center conductor. The metallization thickness and the choice of material must be appropriate for the skin depth at the operating frequency range of the coaxi

7、al cable. Connectors Connectors and launchers for microwave- optical cable are relatively simple in concept: The center pin of the connector is tubular, per- mitting the optical fiber to pass through to its termination at an optical source or detector (Figure 2). Although straightforward in con- cep

8、t, the mechanical alignment must be appropriate for an optical connector. In addi- tion, the conductor dimensions and dielectric properties must be appropriate for the desired microwave characteristic impedance. SMA connectors have dimensions that allow modification for use with this type of cable.T

9、he center conductor can be adapted for New applications in microwave and optical communications may benefit from coaxial cables that combine an optical fiber with a conventional center conductor and outer conductor/shield Figure 1 Cutaway diagram of a combined coaxial and fiber optic cable. Coaxial

10、Cable Outer Conductor Dielectric Metallization Cladding Fiber Optical Fiber From July 2002 High Frequency Electronics. Copyright 2002 Summit Technical Media, LLC RadioFans.CN 收音机爱 好者资料库 High Frequency Design MULTI-SIGNAL CABLES an optical fiber to pass through, while providing an electrical connecti

11、on to the metallization of the fibers cladding. The connection to the outer conductor is unchanged from normal coaxial cable. Performance Measurements on the MOST (Microwave Optical Simultaneous Transmission) cable from Haverhill Cable & Manufacturing show that this design is practical as a microwav

12、e cable. The cable tested was compatible with standard 0.047 in. diameter semi-rigid coax. A multi mode step index fiber was used, with a core diameter of 183 m, a clad diameter of 220 m and a metallized diameter of 275 m, which is equal to the normal inner conductor diameter of 0.011 inch. An 18 in

13、ch long test cable with modified SMA connectors demon- strated a maximum VSWR of 1.28 from 0.5 to 18 GHz. Attenuation of the cable assembly at 1 GHz was equivalent to 58 dB/100 ft., rising to 260 dB/100 ft. at 20 GHz. To extend the frequency range of the cable, bet- ter connectors are required, and

14、work has been done to develop 2.4 mm and 2.9 mm interfaces. Applications These MOST cable assemblies can be used in phased array antenna sys- tems, signal processing networks, and systems that require extremely high isolation. The latter include remotely-located sensors or up- and downconverters tha

15、t can be driven with one transmission mode, return- ing a signal on the other. About the Author After more than 30 years in the microwave industry, Foster Kneeland founded Haverhill Cable & Manufacturing Corp. in 1984. He studied Mechanical Engineering at Northeastern University and holds three US patents. Contact Haverhill Cable at 978-372-6386 or visit Figure 2 Basic design of connectors and launchers for these cables. Center contact with fiber-optic center Two-hole flange SMA jack RF contact Optical source or detector RadioFans.CN 收音机爱 好者资料库