|Linear - New I/Q demodulator
reduces the cost of 3G / WiMAX basestation receivers
Other topics: WiMAX Basestation Receivers,
WiMAX Radio Integration
October, 9 2007
A new high-linearity direct-conversion I/Q demodulator has been
announced by Linear Technology. The device significantly reduces the
cost of 3G and WiMAX basestation receivers, says the company.
The LT5575's extended operating frequency range from 800MHz to 2.7GHz
covers all of the cellular and 3G infrastructure, WiMAX and RFID bands
with a single part. Its capability to convert from RF directly to
baseband at DC or low frequency results in simplified receiver designs,
reduced component count and use of lower cost, low frequency components.
|The device offers an
outstanding IIP3 of 28dBm and IIP2 of 54.1dBm at 900MHz, and an IIP3 of
22.6dBm and IIP2 of 60dBm at 1.9GHz. Moreover, the device has a
conversion gain of 3dB, which when combined with a DSB Noise Figure of
12.7dB produces excellent receiver dynamic range. The device's I
(In-phase) and Q (Quadrature phase) outputs have typical amplitude and
phase matching of 0.04dB and 0.6 degree, respectively, providing an
unprecedented level of demodulation accuracy.
The LT5575 is capable of supporting multiband basestations covering both
the 850MHz GSM/EDGE bands and the 1.9GHz/2.1GHz 3G wireless services
(including CDMA2000, WCDMA, UMTS, and TD-SCDMA). It is ideal for single
carrier micro- and pico-basestations, where low cost architectures are
key. Its performance is also well suited to 2.6GHz WiMAX basestations,
and as an IF demodulator in a microwave radio link or satellite
receiver. Additionally, the LT5575's high 13.2dBm P1dB (1dB compression
point) performance at 900MHz makes it an 'exceptional' demodulator for
high-performance RFID readers.
The LT5575 integrates two matched, high-linearity mixers. These are
driven in quadrature by a low-noise, buffered LO (Local Oscillator) with
an on-chip precision 0 degree and 90 degree phase shifter. The mixers
produce accurate I and Q demodulated outputs capable of supporting a
baseband bandwidth from DC up to 490MHz. Both the RF and the LO inputs
have integrated on-chip transformers that enable 50ohm broadband
matching and single-ended operation. This simplifies the design and
The LT5575 operates from a single 5V supply, drawing a quiescent supply
current of 132mA. The device comes in a 16-lead 4mm x 4mm QFN package,
says the company.
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