Microwave Engineering Europe - December 2008 - (Page 34) 34 PRODUCTS Broadband active filters with ADC driver high-performance and accuracy in a tiny form factor A series of active, broadband lowpass filters from Linear Technology includes single- and dual-channel devices spanning 2.5 to 14 MHz, and also provides buffering and drive for the subsequent ADC stage. Target applications include femtocells and I/Q demodulation (WiMax, CDMA-2000, W-CDMA, and LTE), RFID readers, imaging, and sonar designs. The LTC6603 features a dual matched programmable 9th order switched capacitor linear-phase filter and ADC driver. The filter’s lowpass cutoff frequency up to 2.5 MHz and its gain are adjustable via a serial SPI port, or can be fixed by pin-strapping. Fine frequency control over 100:1 frequency range can be implemented using an external DAC to vary the device’s master reference clock. The LTC6603’s programmability, sharp filter rolloff frequency response, along with guaranteed phase and gain performance make it ideal as a baseband filter for I/Q demodulators in CDMA-2000, W-CDMA and LTE femto-cell basestations, repeaters, RFID readers, imaging, sonar scan receivers and a wide range of industrial signal processing instruments. The filter comes in a small 4 mm x 4 mm 24lead QFN package offering significant cost and space savings compared to alternative discrete solutions. The second filter in the family, the LTC6601-1, is a low noise 0.5 percent tolerance lowpass active filter and ADC driver with configurable bandwidth from 5 MHz to 28 MHz. The filter has a 2nd order linear phase Butterworth response. It has differential inputs and outputs. The filter’s on-chip resistors Four port RF switch matrix operates between 100 and 550 MHz Renaissance Electronics Corporation has announced the 18A1NAI RF switch, which is a four I/O RF matrix with four coupled ports that operate between 100 and 550 MHz. This matrix is designed for RF simulation applications that require the ability to inject and measure signal integrity in the presence of an interference signal. The maximum input power level at any I/O port is 1 W and the unit is fully programmable using GPIB and capacitors that form its cutoff frequency, Q (quality factor of a filter) and gain are laser trimmed at the factory to an absolute tolerance of 0.5 percent typical. These resistors and capacitors are pinned out, allowing users to pin strap wide combinations of filter response and gain. Additionally, the amplifier’s frequency response is also laser trimmed, resulting in a highly accurate and repeatable filter response from device to device. Higher order filters can be attained by cascading multiple stages of the LTC6601-1. Moreover, the amplifier has a robust output stage to directly drive many high sampling speed A/D converters. Each filter comes in a 4mm x 4mm 20-lead QFN package. Thus the filter offers form factor, reduced external component count and performance advantages over discrete filter solutions. Rounding out the family are the LTC6605-7, -10 and -14, which are fixed frequency, 2nd order linear phase dual matched lowpass active filters having bandwidths of 7 MHz, 10 MHz and 14 MHz, respectively. Each filter pairs are tested and guaranteed to offer tight matching of phase and gain characteristics. These filters are ideal for I/Q demodulator channel filtering in WiMAX and broadband wireless access equipment including point-to-point microwave links. www.mwee.com/212200819 commands. All paths have 90-dB/1-dB or 130-dB/1-dB programmable attenuators. Isolation between I/O ports is over 100 dB. The switch comes with a GPIB interface. www.mwee.com/211800413 Baseband processor for 4G smartphones cuts cost, real-estate and time-to-market Addressing the need to cut cost, real estate, and time-tomarket for 4G multi-mode smartphones, Sandbridge Technologies has unveiled the SB3500 flexible baseband processor. The chip facilitates 4G implementation in handsets entirely in software, resulting in cost and real estate reductions in the 15 to 20 percent range. The baseband processor operates any radio protocol for a multi-mode, multi-function mobile platform including LTE, HSPA, 3G, WiMAX, Wi-Fi, DVB-H, GPS and all multimedia formats. The first generation of this reprogrammable baseband chip, designated the 3011, was introduced a couple of years ago, but met with less than stellar market acceptance. What the experience did give the company was reaching the point where both operators and handset OEMs understood that the technology did meet the required performance characteristics, could achieve real-time operation at commercial power levels, and could pass the muster of testing. The marketplace, however, asked for a 4G capable version and now the company’s SB3500 chip is available. To address 4G, some of the challenges to overcome included the fact that bit rates go up dramatically, from 2 or 3 Mbps over cellular, now to 50-100 Mbps, driving error corrections into a whole new range of performance requirements. This and other challenges drove architectural changes and enhancements to the instruction set. The SB3500 provides third-party application developers with a common platform based entirely on the C programming language, expediting the development and rapid distribution of new features and functions. The software-based design of the SB3500 baseband chip alters the landscape of the mobile industry by accelerating the cost efficient development and distribution of faster, more flexible ultramobile-devices with the capacity for virtually unlimited communications protocols and multimedia applications. www.mwee.com/212200898 Microwave Engineering Europe ● December 2008 ● www.mwee.com http://www.mwee.com/211800413 http://www.mwee.com/212200819 http://www.mwee.com/212200898 http://www.mwee.com
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