Passive components would appear at first to embody some of the more mature of microwave technologies. After all, passive component functions such as dividing and coupling power, filtering, switching, attenuating, and terminating high-frequency signals have been in existence for more than half a century. But surprisingly, passive components have enjoyed their share of technological advances in recent years as demands for lower cost, smaller size, and higher integration drive the latest generation of passive component products.
In recent years, designers of passive components have embraced three-dimensional approaches rather than traditional planar configurations in order to shrink the size of a component without sacrificing power-handling capability. Credit is due to commercial electromagnetic (EM) modeling tools from such companies as Agilent-EEsof (Santa Rosa, CA), Ansoft (Pittsburgh, PA), Applied Wave Research (El Segundo, CA), Computer Simulation Technology ((Wellesley Hills, MA), Sonnet Software (Syracuse, NY), and Zeland Software (Fremont, CA) for allowing design engineers to visual high-frequency components and structures in terms of current distribution even across multiple circuit layers.
The fruits of such EM modeling tools can be found in a generation of shrinking (in size and cost) high-frequency passive components that can effectively dissipate power levels once handled by units much larger. The Xinger lines of passive components from Anaren Microwave (East Syracuse, NY, www.anaren.com), for example, are popular among designers of cellular-communications amplifiers and base-station equipment for their small size and performance. For certain product series, such as hybrid couplers, the miniature Xinger product line has been augmented by the even smaller Micro Xinger and Pico Xinger product lines.
For example, the model 1F1305-3 Xinger 3-dB hybrid coupler was designed for PCS applications from 1993 to 1990 MHz. The 90-deg. quadrature hybrid suffers 0.23 dB or less insertion loss and achieves at least 21-dB isolation between ports. The maximum VSWR is 1.17:1. In spite of the small size of 0.56 × 0.35 × 0.076 in., the surface-mount component can handle 100 W CW input power at temperatures from –55 to +85°C. The small size does contribute to outstanding amplitude and phase unbalance levels of ±0.15 dB and ±2 deg., respectively.
In the Micro Xinger line, the model 1M803 3-dB hybrid coupler operates from 5 to 6 GHz with 0.25-dB maximum insertion loss and 20-dB minimum isolation. It measures just 0.40 × 0.20 × 0.065 in., but handles 20 W CW power. In the Pico Xinger line, the model 1P503S 3-dB hybrid coupler operates in the DCS and PCS band from 1700 to 2000 MHz with no more than 0.25 dB insertion loss and at least 20 dB isolation. It measures 0.25 × 0.20 × 0.054 in. but handles 30 W CW power.
In higher-power applications, the firm's acquisition a few years ago of the former RF Power brought with it lines of small but rugged components capable of handling hundreds of watts of input power. Model S03B2150N3 is one of these components, a 3-dB hybrid coupler that operates from 2000 to 2300 MHz with maximum insertion loss of 0.15 dB and minimum isolation of 20 dB. The low-profile 90-deg. hybrid was designed for UMTS and other 3G cellular systems and is suitable for use in balanced amplifiers. In spite of measuring only 1.0 × 0.5 × 0.15 in., the hybrid coupler handles 300 W CW power at temperatures from –55 to +85°C.
Late last year, the firm unveiled its Xinger II 3-dB couplers with several modifications from the original Xinger lines, including leaded and nonleaded versions and larger soldering pads for improved handling with automated assembly equipment. The compact couplers were developed for wireless applications from 410 to 2700 MHz, covering such applications as GSM, DCS, PCS, AMPS, 3G, UMTS, WiMAX, and WLAN systems with typical insertion loss of 0.12 dB or less, minimum isolation of 20 dB, power handling to 225 W. Later this year, the company will introduce Xinger parts from its Consumer Components Group (CCG), including patent-pending crossover networks—small components that enable the transition of two intersection RF traces in a surface-mount package. The 50-Ω model X0060L5050A00 low-profile RF crossover is supplied in a 0603 package. It covers DC to 4.5 GHz with 0.03 dB typical insertion loss and better than 40 dB typical isolation at all frequencies. It measures 0.059 × 0.029 × 0.027 in. and features typical return loss of 27 dB.
Merrimac Industries (West Caldwell, NJ) innovative Multi-Mix microtechnology is based on the used of multilayer circuits fabricated on fluoropolymer composite substrates. The substrates are bonded together into a multilayer structure using a fusion bonding process. The process provides a homogeneous dielectric medium for good electrical performance through millimeter-wave frequencies. The company has applied the technology to a wide array of passive components, including low-loss filters operating through millimeter-wave frequencies. Examples of the Multi-Mix filters include bandpass models FPGI-5.77G and FBMM-42.0G. The former provides a 3-dB bandwidth of 0.1 GHz at a center frequency of 5.77 GHz. It suffers maximum insertion loss of 2 dB and measures just 0.8 × 0.55 × 0.12 in. The latter has a 3-dB bandwidth of 3 GHz centered at 42.9 GHz with maximum insertion loss of 3.5 dB. It measures just 0.620 × 0.296 × 0.020 in.
The Multi-Mix technology is also the basis for the firm's PICO Zapper line of directional couplers, including the 2.0-to-2.3-GHz model CSDZ-10Z-2.1G. This 10-dB coupler suffers less than 0.2 dB insertion loss with maximum VSWR of 1.25:1. The coupling accuracy is within ±1 dB while the frequency sensitivity is ±0.3 dB. The coupler, which measures just 0.175 × 0.175 × 0.043 in., features directivity of 17 dB or more. Designed with high-stability ceramic-filled polytetraethylene (PTFE) dielectric materials, the couplers incorporate a wraparound ground for improved EM shielding.
Synergy Microwave (Paterson, NJ, www.synergymwave.com) has developed a surface-mount component technology called SYNSTRIP in which smooth transitions between stripline and microstrip structures are possible. This approach, electrical viahole connections are realized as single-layer microstrip viaholes, allowing efficient RF signal transfer from the component level to the 50-Ω microstrip lines on a printed circuit board (PCB). The SYNSTRIP technology has been used for couplers, hybrids, phase shifters, modulators, attenuators, and power dividers through about 3 GHz with excellent power-handling capabilities at low cost. Most recently, the technology has been applied to a line of high-intercept-point mixers through 2200 MHz (see Microwaves & RF, September 2005, Cover Feature, "Wideband Mixers Hit High Intercept Point," p. 98).
Passive components have benefited from a variety of materials technologies, including integration on low-temperature-cofired-ceramic substrates. This technology uses thin layers of ceramic substrates with printed conductors to achieve transmission lines, distributed components, and other high-frequency structures. The layers are bonded together at relatively low temperatures (typically +850°C) compared to higher-temperature ceramic technology, essentially forming three-dimensional, rather than planar, components. The LTCC components feature low loss, good heat dissipation, and hermeticity between layers. As an example of the LTCC technology, Mini-Circuits (Brooklyn, NY, www.minicircuits.com) has developed a line of surface-mount quadrature splitters that measure just 0.25 × 0.30 in., operate in bands from 340 to 2400 MHz, and handle as much as 25 W power. A typical unit, model QBA-24, operates from 1900 to 2400 MHz with 21 dB typical isolation and less than 0.71 dB insertion loss. It exhibits amplitude unbalance of 1.2 dB and phase unbalance of 6 deg. and sells for under $7.00.
Another company making the most of advanced materials is Dielectric Laboratories (Cazenovia, NY, www.dilabs.com). The firm's customizable ceramic technology has been used to produce high-Q resonators as well as tiny filters at frequencies as high as 67 GHz (see Microwaves & RF, September 2005, p. 114 as well as the white paper insert in this issue). The ceramic technology has yielded typical filter specifications of 0.5 to 3.0 dB insertion loss, 45-dB minimum isolation, and return loss of 15 dB.
Narda Microwave (Hauppauge, NY), a long-time supplier of optical components, switches, and EM radiation test equipment, offers extensive lines of broadband passive components, including attenuators, couplers, power dividers, and terminations. As an example, the model 6229-10 directional coupler incorporates 2.9-mm coaxial connectors to span 1 to 60 GHz with 10 dB coupling (flat to ±2 dB) and 8 dB directivity. Suitable for 38-GHz digital radios as well as military radar and electronic-warfare (EW) systems, the rugged coupler handles 20 W average input power and 3 kW peak power with maximum VSWR of 2.50:1 at both primary and secondary (coupled) ports. The firm also offers 18-to-40-GHz and 1-to-40-GHz versions of the 10-dB coupler with the same type of connectors.
Known for their expertise in high-power components, Werlatone, Inc. (www.werlatone.com, Brewster, NY) has developed coaxial passive components capable of handling power levels to 50 kW. For example, the model D5738 two-way in-phase power combiner/divider handles an amazing 12.5 kW of CW power from 1.5 to 30 MHz. It avoids the heat by keeping maximum insertion loss to 0.2 dB and maximum VSWR to 1.25:1. The power combiner/divider features minimum isolation of 20 dB, with maximum amplitude unbalance of 0.2 dB and maximum phase unbalance of 5 deg. The model C7113 6-dB bidirectional coupler measures just 5.2 × 2.7 × 0.75 in. but handles 200 W CW power from 100 to 1000 MHz. It exhibits maximum insertion loss of 0.35 dB with maximum VSWR of 1.20:1. The coupling accuracy is within ±0.5 dB of the nominal 6-dB value while the amplitude flatness is within ±1.0 dB. The high-power coupler achieves minimum directivity of 20 dB.
RLC Electronics (Mt. Kisco, NY) is another long-time supplier of high-performance passive components. The firm recently introduced its model DCB-1020-2, a 1-to-2-GHz power divider with integral DC blocking on selected ports. The microstrip divider incorporates blocking capacitors on all ports except those intended to pass DC. This model features at least 20 dB isolation between ports with 0.3 dB maximum insertion loss and 1.25:1 maximum VSWR. The amplitude unbalance between ports is ±0.2 dB while the phase unbalance is ±3 deg.
The company also recently launched a microminiature SMA single-pole, two-throw (SPDT) switch capable of operating from DC to 26.5 GHz. Supplied with SMA connectors and rated for 1 million switching operations, the model SR-2min-min-R single-pole, two-position switch exhibits maximum insertion loss of 0.3 dB to 8 GHz, 0.7 dB to 18 GHz, and 0.8 dB to 26.5 GHz. The minimum isolation is 70 dB through 8 GHz, 60 dB through 18 GHz, and 50 dB through 26.5 GHz. The maximum VSWR is 1.35:1 through 8 GHz, 1.70:1 through 18 GHz, and 1.80:1 through 26.5 GHz. Available in failsafe and latching configurations, the compact switch meets MIL-DTL-3928 environmental conditions and can be specified for three different coil voltages (+5, +12, and +28 VDC). It measures just 0.75 × 0.70 × 0.49 in. (latching configuration) and weighs only 1.3 oz.
The model P8P-39N-5JD phase shifter (see figure) from GT Microwave (Randolph, NJ, www.gtmicrowave.com) represents a blend of the traditional (phase shifter) with the new (digital control circuitry). The "passive/active" diode-based phase shifter operates from 0.5 to 2.0 GHz with 12-b TTL control and 500-ns switching speed. Providing as much as 0.088-deg. resolution over a 360-deg. range, the phase shifter offers ±10 deg. phase accuracy with a noise figure of 7 dB and amplitude unbalance of ±1 dB. It is designed for input levels to 0 dBm and measures 4.95 × 3.38 × 1 in.
For more than 50 years, Aeroflex Weinschel (Frederick, MD, www.aeroflex-weinschel.com) has supplied rugged fixed and variable attenuators at microwave frequencies. The firm's model 54A, for example, is a fixed coaxial attenuator available for coverage from DC to 40 GHz. Equipped with 2.92-mm connectors, it can be supplied with attenuation values of 3, 6, 10, 20, and 30 dB with attenuation accuracy as good as ±0.5 dB.
For almost 50 years, ARRA (Bayshore, NY, www.arra.com) has been designing and supplying passive components based on waveguide technology. The company's lines of high-power fixed waveguide attenuators, for example, are available in waveguide sizes from WR284 (2.60 to 3.95 GHz) to WR42 (18.0 to 26.5 GHz). They can be supplied with standard attenuation values of 3, 6, 10, and 20 dB as well as custom values, and feature attenuation accuracy of ±0.3 dB at the calibration frequency of the attenuator. The aluminum waveguide attenuators are designed to handle 40 W CW input power.
In addition to the companies mentioned, many high-frequency firms continue to advance the technology and performance levels of microwave passive components. For a more complete listing of suppliers, please visit the Microwaves & RF Product Data Directory website at www.m-rf.com.