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.