SAW duplexers shrink to chip-size packages

Small, lightweight surface acoustic wave (SAW) duplexer has a built-in matching circuit featuring improved attenuation and isolation characteristics.

Kyocera Corp has developed a small, lightweight surface acoustic wave (SAW) duplexer with a built-in matching circuit featuring improved attenuation and isolation characteristics.

Production is scheduled to commence in April 2007 at Kokubu Plant in Kagoshima Japan, with monthly output of one million units.

Kyocera expects to triple monthly production to three million units within a year.

A duplexer is a component that is used in an antenna circuit, to enable duplex and simultaneous conversation by discriminating transmitting and receiving signals.

It is mainly used in the circuits of a CDMA system, where it is a critical component that determines telephone speech quality.

Recently, mobile handsets have required numerous functions and high performance, including slim design, compact body, camera, high-resolution and large LCD, high-speed data transmission, and multiple bands.

The electronic components being mounted in terminals also need to be more integrated, smaller and lighter, resistant to temperature change, vibration and shock as well as highly reliable.

In responding to these demands, Kyocera has developed the SD25 series of chip size package (CSP) duplexers by taking advantage of its unique simulation technology that mounts minimised SAW element directly on ceramic substrate, seals it and coats it with resin.

Optimising the combination of the SAW element and the substrate enables the duplexer to be as small as 2.5 x 2.0 x 0.8mm (typical value), making it one of the smallest duplexers in the industry.

The product boasts excellent resistance to climate and mechanical impact thanks to its airtight structure, which seals with soldering the surrounding of the element mounted on the substrate.

Low temperature cofired ceramic (LTCC) is used as ceramic substrate.

It allows an inductor for a matching circuit to be incorporated.

As a result, the SD25 series requires no external inductor that is normally used for a matching circuit.

This helps simplify circuit design while reducing the number of components and saving the component assembly space.

"The LTCC substrate that we used for this product takes advantage of the fine ceramic technologies Kyocera has been developing and cultivating since it was founded", says Yoshifumi Yamagata from Kyocera's Kyoto R and D Centre.

"Miniaturisation often tends to cause a deterioration of isolation and attenuation characteristics in the high frequency band, but we never sacrificed them this time".

"We are proud that we can offer the small duplexer with the improved characteristics for our customers".

"The SD25 series will contribute to improve speech quality and miniaturise the CDMA terminals".

The products have two different specifications, one for Japanese CDMA (Japan CDMA Band) and the other for North American CDMA (Cellular Band), and will be released in April.

Kyocera plans to develop products for the UMTS bands in the near future.

The SD25 series is also an environmentally friendly product using lead-free materials, and complies with the RoHS Directive.

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