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Optimized to offer high linearity and wide dynamic range, Linear Technology's active downconverting RF mixer LT5527 brings a high level of integration to simplify the design of 3G cellular base stations. The active double-balanced RF mixer features an operating frequency range of 400 MHz to 3.7 GHz. At 1.9 GHz, the LT5527 offers input third-order intercept point (IIP3) linearity of 23.5 dBm, conversion gain of 2.3 dB, and a noise figure of 12.5 dB. It also meets the dynamic range requirements of 3G cellular base stations and other high-performance wireless infrastructure receivers. The LT5527's local oscillator (LO) and RF inputs operate single-ended and have built-in 50 Ω impedance, requiring few external matching components, reducing base station cost and design time.

Moreover, the active mixer incorporates a low noise differential LO buffer, allowing operation at a -3 dBm LO drive level, resolving the challenges of RF isolation and reducing the need for external filtering. Since it operates over a wide frequency range from 400 MHz to 3.7 GHz, it covers the 850 MHz cellular band, the 1.9 GHz and 2.1 GHz W-CDMA and UMTS bands, as well other high-performance wireless applications that operate in bands at 450 MHz, 2.4 GHz and 3.5 GHz.

In addition, the high linearity mixer features on-chip RF transformers at both the RF and LO inputs (see figure below). The broadband integrated transformers facilitate 50 Ω impedance matching and allow these inputs to operate single-ended, simplifying product development and speeding time to market. The RF input is internally matched to 50 Ω from 1.7 GHz to 3 GHz and the LO input is internally matched to 50 Ω from 1.2 GHz to 5 GHz. However, simple external matching easily extend the frequency range of both the ports. The IF output is partially matched and usable for IF frequencies up to 600 MHz. Also, the differential IF output permits interfacing to differential IF filters and amplifiers. It can also be easily matched to drive 50 Ω single-ended, with or without an external transformer.

Other features include low LO to RF leakage of -44 dBm (f_LO = 400 MHz to 2100 MHz) and -36 dBm ( f_LO = 2100 MHz to 3200 MHz) and high RF to IF isolation of more than 42 dB at f_RF = 400 to 800 MHz and >54 dB at f_RF = 800 to 3700 MHz. The LT5527 is implemented in an RF bipolar process with ft of 30 GHz, and operates from a single 5 V supply voltage. While its typical operating current is 78 mA. The device can be shutdown by an ENABLE pin. When disabled, the chip draws 100 µA maximum quiescent current to conserve power. This mixer does not offer image rejection.

Available in a 16-pin 4 mm × 4 mm surface-mount QFN package, it is priced at $5.80 each in 1,000-piece quantities.

Linear Technology Corp.
(408) 432-1900
www.linear.com

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