Passive components are the old, taken-for-granted workhorses of the high-frequency-electronics industry. The tasks that they perform, such as filtering and signal routing, are essential to both circuits and systems. Yet many are surprised to learn how much ongoing development is occurring in this area. New passive products are constantly coming out, thanks in large part to the spawning of new materials. Many of these product introductions are inspired by next-generation performance needs. Yet products also must evolve to meet the needs of a changing world—one in which RoHS compliance has become mandatory and technologies like low-temperature cofired ceramic (LTCC) are enabling even smaller components with higher performance.

A new family of true tabless surface-mount ceramic resonators, for example, makes RoHS compliance a priority. Hailing from Integrated Microwave Corp. (San Diego, CA), this technology promises to deliver better reliability and accuracy when compared to traditional metal-tabbed resonators. With a larger solder pad, these resonators promise to eliminate misalignment and tab-solder reflow problems (Fig. 1). As a result, they should raise manufacturing efficiency while delivering higher Q.

In the switch arena, size reductions and performance improvements also are coinciding with adherence to RoHS requirements. The MASW-007107 from M/A-COM (Lowell, MA) is a DC-to-8-GHz, single-pole double-throw (SPDT), RoHS-compliant switch. It is well suited for systems that require handling power levels to ±27 dBm (5-V operation) with error vector magnitude (EVM) of better than 2 percent for an orthogonal-frequency-division-multiplexing (OFDM), 64 QAM, 54-Mb/s signal. At 3.3 V, the switch handles associated linear output power of ±21 dBm. The MASW-007107 is fabricated on a low-cost, 0.5-µm, gate-length gallium-arsenide (GaAs) process. Full passivation is included for robust reliability. The switch maintains an insertion loss of 0.5 dB up to 6 GHz and 0.7 dB up to 8 GHz while achieving high isolation to 30 dB. It is especially suitable for linear communications applications like WiMAX and Ultra Wideband (UWB).

RF-integrated-circuit (RF IC) switch technologies take the forms of GaAs, CMOS, and PIN diode. The UPD5713TK CMOS SPDT switch from NEC (Tokyo, Japan) was designed for transmit and receive, antenna diversity, band selection, and other general RF switching applications. Compared to GaAs IC switches, the company claims that the CMOS switch has a lower cost while providing a lower part count than PIN diodes. The UPD5713TK requires only a single control voltage line. Its frequency range is 50 MHz to 2.5 GHz. At DC to 1.0 GHz, the switch's insertion loss is typically 0.6 dB. It is typically 0.8 dB at 2.0 GHz. The switch's isolation is typically 32.5 dB at 1.0 GHz and 25 dB at 2.0 GHz. At 2.8 V, it handles +21 dBm power at 1-dB compression. The UPD5713TK targets mobile communications, set-top boxes, instrumentation, and short-range wireless applications.

PIN-diode switches also are evolving to meet the needs of new applications. American Microwave Corp. ( Frederick, MD) offers a single-pole three-throw (SP3T), absorptive, PIN-diode switch that operates from 2.0 to 6.0 GHz. This switch's isolation is 70 dB. It flaunts an insertion loss of 3.5 dB and a VSWR of 2.0:1. At +20-dBm maximum RF input power, the switching speed is impressive with 15-ns rise/fall and 100-ns on/off times. The switch has TTL control and DC power-supply requirements of +5 VDC at 150 mA maximum and ?5 VDC at 100 mA maximum.

Of course, switches are not the only passive components being driven to meet small-size demands. AVX Corp. ( Myrtle Beach, SC) plans to satisfy thin-package requirements with a very-low-profile, multi-layer ceramic capacitor (MLCC). Designated the LT series, this capacitor is offered in 0402, 0603, 0805, and 1206 case sizes (Fig. 2). The product is an expansion of the X5R dielectric product offering. The X5R is a Class II dielectric with a temperature variation of capacitance within ±15 percent from ?55° to +85°C. The LT series is available in operation voltages of 4, 6.3, 10, or 16 VDC with a capacitance tolerance of ±10 or ±20 percent. The MLCC targets decoupling and filtering applications in which height clearance is limited.

Also hailing from AVX is the SQCF, which offers very low effective series resistance (ESR) in an 0805 package. Because of the 100-percent tin terminations, the EIA 0805 model SQCF is RoHS compliant. The SQ series also comes in 0603, 0605, and 1210 case sizes. The capacitors are available with operating voltages up to 250 VDC and capacitance of 240 pF. This capacitor is geared toward RF-amplifier, base-station, wireless-infrastructure, and point-to-point and multipoint radio applications.

In the coupler arena, much development is predictably still driven by wireless communications. Microlab/FXR (Parsippany, NJ), a wholly owned subsidiary of Wireless Telecom Group, Inc., has expanded its range of directional couplers. By covering 800 to 2500 MHz, the CK-60 series includes the cellular, PCS, and UMTS bands in a single unit in either N or SMA connectors (Fig. 3). Impressively, these directional couplers have been designed using a dual-section airline design for low-loss, flat frequency response, and 100 W of through-line power. Thanks to the wide frequency range, the design can be used with multiband antennas and leaky cable systems.

Some recently released couplers from MECA Electronics (Denville, NJ) also satisfy wireless-application needs. The rugged, 50-W couplers were designed to serve all of the wireless bands from to 2.2 GHz. They are well suited base-station and in-building wireless systems. The couplers credit their microstrip design for their insertion loss of 0.3 dB, directivity of 23 dB, and VSWR of 1.10:

The Model IPP-2015 90-deg. hybrid coupler from Innovative Power Products, Inc. (Holbrook, NY) covers 2000-to-4000-MHz frequency range. This coupler combines two signals up to 200 W CW of total output power. The 3-dB hybrid delivers insertion loss of less than 0.4 dB. Phase balance is less than ±4 deg. and VSWR is less than 1.25:1. Amplitude balance is less than ± dB. In addition, the coupler promises greater than 18 dB of isolation.

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Recently, RLC Electronics (Mount Kisco, NY) began offering a range multi-hole, broadwall directional couplers. These components cover the frequencies from 40 to 2.6 GHz in standard waveguide sizes. To achieve high directivity and coupling flatness, the couplers use a precise machined coupling hole pattern and a precision load in the secondary arm. The VSWR for these couplers is 1.1:1 maximum (primary) and 1.15:1 maximum (secondary).

An 8-to-11-GHz directional coupler from Planar Monolithics Industries, Inc. (Frederick, MD) offers field-replaceable SMA connectors. The RFOC-811-QRCdc-10 10-dB coupler uses microstripline technology to strip line transitions. All of the feed-throughs of input and output ports can thus be soldered directly to the mechanical housing to have better mechanical support. The maximum true insertion loss and the minimum directivity of the coupler are 1.6 and 10 dB, respectively.

Microstrip design also is at the heart of a new UWB power divider for in-building applications. The two-way power divider, which also comes from Microlab/FXR, covers the broad band of 350 to 6000 MHz. It allows multiple bands to share a common antenna or distributed antenna system. In addition, Microlab/FXR has announced a two-way power divider covering the WiFi and WiMAX signals in the 5150-to-5850-MHz band. Thanks to its innovative air-line construction, this RoHScompliant power divider vows to provide very low loss, a minimum of 19 dB isolation, and good input and output VSWR. Its standard power rating for as a divider is 10 W.

To make all of these products possible, a lot of impressive work must take place behind the scenes. For example, Dielectric Laboratories (Cazenovia, NY) uses its customizable ceramic technology to produce both high-Q resonators and very small filters at frequencies as high as 67 GHz. For filters, that ceramic technology typically yields 0.5 to 3.0 dB insertion loss, 45-dB minimum isolation, and 15 dB of return loss.

Many passive components also have been born out of Synergy Microwave's (Paterson, NJ) SYNSTRIP surface-mount component technology. This technology enables smooth transitions between stripline and microstrip structures. Electrical via-hole connections thus become single-layer microstrip via holes. Among other components, this technology has been applied to the company's hybrids. The DQS-30-450 operates from 30 to 450 MHz. It has an insertion loss of 1.2 dB typical and 1.7 dB maximum. The hybrid's amplitude unbalance is 1.0 dB typical and 4.5 dB maximum. It offers a phase unbalance of ±0.2 deg. typical and ±3.0 deg. maximum.

By combining LTCC technology, semiconductor technology, and a manufacturable circuit layout, Mini-Circuits (Brooklyn, NY) has created a high-performance passive mixer (see "Upconverter Mixer Makes Most Of LTCC For ISM Applications," August 2006, p. 104). The OEMs working in the 2450-MHz band can use this mixer to upconvert those frequencies to the 5.7-to-5.8-GHz band. The RoHS-compliant mixer targets the wireless applications using the unlicensed spectrum in the Industrial-Scientific-Medical (ISM) bands. It boasts 2400 to 2500 MHz of IF input range, 5500 to 6000 MHz of RF output range, and a local-oscillator (LO) input range of 3100 to 3600 MHz. Its nominal LO power is +7 dBm while its conversion loss is 6.8 dB typical. The mixer typically has LO-RF isolation of 40 dB and LO-to-IF isolation of 16 dB.

The Multi-Mix Microtechnology from Merrimac Industries (West Caldwell, NJ) has enabled significant reductions in passive-component size. At the same time, it conforms to RoHS and lead-free requirements. In the Multi-Mix process for microwave, multilayer integrated circuits and micro-multifunction modules (MMFMs), fluoropolymer composite substrates are bonded together into a multilayer structure. This bonding is done with a fusion process, which provides a homogeneous dielectric medium for superior electrical performance at microwave frequencies. When combined with embedded semiconductor devices, MMICs, etched resistors, circuit patterns, and plated-through via holes, the bonded multilayers form a surface-mount module. That module does not require any further packaging. Rather, the MMFM structure actually becomes the package.

The next generation of this process, Multi-Mix PICO, vows to reduce the size of single-function microwave components from 84 percent to 87 percent compared to previous Multi-Mix designs. The Zapper PDD-2C-3G power divider operates from 2000 to 4000 MHz. It offers 20 dB minimum isolation and VSWR of 1.2:1. The divider's insertion loss is 0.30 dB maximum.

In the case of Multi-Mix, the technology becomes the package. In more typical scenarios, however, passive-component makers are under pressure to find packages that complement their ever-smaller, often-RoHS-compliant products. Meanwhile, package makers must tackle the component requirements for WiMAX and 5-GHz and higher frequencies with lower-cost packaging. Over the summer, StratEdge (San Diego, CA) introduced the G2420M-1 discrete semiconductor hermetic package for broadband applications. This glass/ceramic-walled package has a 0.205 × 0.245-in. body and a cavity of 0.105 × 0.145 in. It comes with an ASTM F-15 alloy base for devices up to 0.5 W. For higher-power devices, the package can be supplied with a copper composite insert or base. It is constructed using a glass-to-metal seal process. With seven leads—four on one side and one each on the other three sides—this package is a clear fit for SPDT switch applications. Such switches can be mounted on the board in drop-in or surface-mount configurations.The packages are lead-free and meet RoHS compliance.

Clearly, passive components are being pushed to satisfy the next level of performance, environmental friendliness, and size demands. Thanks to some impressive innovations in materials, technology,-and manufacturing, they are succeeding. At the same time, many of them are meeting the stringent price demands of their customers.

For a more complete listing of suppliers, visit the Microwaves & RF Product Data Directory website at www.m-rf.com.