There are two approaches to the modularization of SAW filters. One is to combine a SAW filter with its peripheral circuits, and the other is to pack two or more SAW filters in a single package.
A representative modular SAW filter product containing peripheral circuits is one that can respond to a balance circuit. At present, many RF-ICs have balanced IC circuits to suppress noise generated inside them. On the other hand, many filters connected to such ICs are unbalanced input-output products. In such a case, it is necessary to add baluns and other devices, causing an increase in the number of parts needed.
To supply products that solve these problems, Murata is mass-producing SAW filters responding to balance circuits with balun functions added, and these products find wide-ranging uses such as for EGSM
(Extended Global System for Mobiles) systems, DCS (Digital Communication Systems), CDMA800 and W-CDMAsystems, GPS (Global Positioning Systems) and other products.
In many cases, the GSM and CDMA systems adopt a direct conversion system on the reception side for the purpose of simplifying their circuit configurations. In the case of a balance circuit for the direct conversion system, signals received are liable to be distorted and unnecessary spurious signals caused when signals are joined inside the IC, in case amplitude balanced deviation and phase balanced
(continued on page 53)
 |
|
Advanced SAW Filters Facilitate Design of...
deviation are great in the balanced out- piezoelectric substrate, a high den- As explained earlier, the company put of a SAWfilter. Therefore, SAWfil- sity mounting technology for hous- has established for SAW filters an inters with limited amplitude and phase ing two or more piezoelectric sub- dispensable position as key parts for the balanced deviation are needed. strates in a single package, and flip- RF circuits of cellular terminals by enMurata’s SAW filters for the RF cir- chip technology. deavoring to reduce their sizes and by cuits of EGSM systems minimize their The company is now developing a adopting a modular format. One of the effect on ICs by achieving an amplitude modularized SAW filter addressing purposes of the company’s research and difference of 1.0dB and a phase differ- two or more balance circuits, aiming development efforts is to supply the marence of 180(plus-minus) 10° or less in to further modularize its SAW filters. ket with SAW filters that meet a martheir balanced output. Modularization of SAW filters is not ket need by solving various technical Meanwhile, speaking of the other confined to combining two or more problems and by exploring the possimodularization approach of making SAW filters, but it is now moving to- bilities of SAW filters for a new market a single package contain two or more ward developing modularized prod- and to create new products. SAW filters, there is a strong market ucts with ICs and SAW filters mounted need for such SAW filters for use in on multi-layered substrates. SAW fil- cellular terminals using two or more ters
that are mounted on such prod- About This Article wavelengths. Murata
is mass-pro- ucts need to adopt smaller sizes and ducing dual SAW filters for PDC and lower profile. The author, Takashi Senbo, serves as EGSM/DCS systems by fully utiliz- Murata is concentrating its develop- the Assistant Chief of the Product Ening its high density technology for ment efforts on SAW filters using bare gineering Section at Microwave Prodforming two or more odd-shaped chips, while endeavoring to downsize ucts Department I of Murata Manufacthick film sheets on one and the same SAWfilter packages with reduced height. turing Co., Ltd. |
Уважаемый посетитель!
Чтобы распечатать файл, скачайте его (в формате Word).
Ссылка на скачивание - внизу страницы.
