Driven by suppliers of wireless-LAN chip sets, passive-component manufacturers are developing innovative devices and technologies to meet the requirements for high-performance characteristics such as quality, or "Q," factor, equivalent-series resistance (ESR) and small packaging in the WLAN.
Next-generation components for WLAN applications will most likely come in the form of antennas, integrated passive devices and module designs, many of them based on low-temperature co-fired ceramic (LTCC) technology for high performance and small size.
In many cases, passive-component suppliers are already ramping up production on low-pass and bandpass filters for WLAN applications that feature surface-mount packaging, low profiles and light weight. For example, Jaro Components (Boca Raton, Fla.) offers a wide selection of LTCC-based low-pass filters, bandpass filters, 2.45-GHz antennas, diplexers and baluns. The LTCC products are said to offer low insertion loss and high attenuation.
AVX Corp. and Vishay Intertechnology have developed innovative components and technologies for wireless applications. AVX, for instance, has introduced a microwave single-layer X7S-dielectric capacitor family that's designed to replace Z5U and Y5V dielectrics currently used in the company's SLC capacitors. This so-called "Z" dielectric extends the temperature range to -55 degrees C to 125 degrees C. The company said the broadband characteristics and high dielectric constants (2,500 to 15,000) make the Z dielectric ideal for wireless-LAN and telecommunications applications.
For passives, the key requirement for Wi-Fi applications is a higher Q characteristic, which means low loss at radio frequencies and lower leakage, said Ron Demcko, applications engineering manager and Fellow at AVX's Advanced Products Division (Myrtle Beach, S.C.). In some cases, wireless designers are looking for devices that integrate inductors and capacitors for both thick-film and thin-film technologies, he said.
AVX is looking closely at thin-film technology for integrated capacitors, inductors and possibly resistors in a network for better noise characteristics, low leakage and miniature sizes, Demcko said.
In the integration arena, AVX's newly released W2H/W3H series of miniature ceramic chip feed-through filters can be used to suppress elecromagnetic interference in wireless LANs. This passive component combines capacitor and inductor elements in a single distributed constant-circuit filter and offers excellent decoupling and significant noise reduction in digital circuits up to 5 GHz, said the company.
The W2H/W3H series, available in 0805 and 0612 case sizes, offers capacitance ratings from 200 to 100,000 picofarads in voltage ratings of 25, 50 and 100 V. Dc resistance is rated at less than 0.15 ohm and current at 0.5 to 5 amps.
The HPC series of silicon capacitors from Vishay Intertechnology (Malvern, Pa.), packaged in a 0402 case size, is billed as particularly suited for Wi-Fi applications. Vishay said the parts offer 10 times the capacitance density of other precision RF capacitor technologies and that their higher series resonant frequencies (SRFs) open up the frequency range from about 3 GHz to about 15 GHz. The series is available in a capacitance range of 0.1 to 180 pF. The standard operating temperature range is -55 degrees C to 125 degrees C.
Meanwhile, Johanson Technology (Camarillo, Calif.) and NIC Components Corp. (Melville, N.Y.) are improving traditional passive components for RF applications. For instance, Johanson Technology's S-Series of ultralow-ESR capacitors offers SRFs up to 25 GHz and a capacitance value range of 0.2 to 220 pF. Available in 0201, 0402, 0603 and 0805 case sizes, the capacitors can be used in a variety of applications including wireless LANs, portable wireless products and RF ICs, the company said.
NIC Components' answer to a host of wireless applications is its wide range of low-ESR and high-Q NPO ceramic chip capacitors. Designed for high-speed, high-frequency applications such as Bluetooth and WLAN products, the NMC-L and NMC-M chip capacitors are available in a capacitance range of 0.5 to 150 pF.
Several passive-component companies including Murata Electronics, Taiyo Yuden and Yageo have LTCC-based modules or integrated passive devices as well as high-frequency antennas under development for next-generation WLAN designs.
Murata says it is currently working with several IC vendors on integrated module designs. Taiyo Yuden (San Jose, Calif.) is also working closely with several IC vendors to fully optimize the performance of a bandpass filter slated for introduction this year. The company will also release several antenna products later this year for 2.4/5.2-GHz applications.
Yageo USA (Addison, Texas) has a triband antenna under development and offers several high-frequency antennas for a variety of wireless communications applications including IEEE 802.11b/g/a WLANs.
The antennas are designed for portable devices such as PDAs and tablet PCs as well as dual-band WLAN products for 2.4/5-GHz modules, the company said.
Jaro Components Inc.
Johanson Technology Inc.
Murata Electronics North America Inc.
NIC Components Inc.
Taiyo Yuden R&D Center of America