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04-05-2018

300MHz to 9GHz High Linearity I/Q Demodulator Supports 1GHz Bandwidth & Achieves up to 60dB Image Rejection

Analog Devices » LTC5594

Analog Devices announces LTC5594, a wideband, high linearity true zero-IF (ZIF) demodulator with 1 GHz instantaneous I and Q 1 dB bandwidth. The demodulator is capable of 37 dB image rejection typical. Using the on-chip serial port, the device allows correction of the I and Q phase and amplitude imbalance, hence can be tuned to achieve an image rejection of better than 60 dB. This feature greatly eases calibration while significantly improving receiver performance and reducing FPGA resources needed to null the residual image. In addition, the device has integrated baseband amplifiers with adjustable gain, providing a maximum power conversion gain of 9.2 dB at 5.8 GHz, while delivering 37 dBm output IP3 performance. The RF input has an integrated wideband balun transformer, allowing single-ended operation with 50 Ω matching from 500 MHz to 9 GHz. The same input can be matched at lower frequencies from 300 MHz to 500 MHz by changing one external matching component value. Its high level of integration results in minimum external components and small solution size.

Analog Devices - LTC5594

By using the on-chip serial port, all the calibration can be easily set. Besides image rejection, the linearity performance including IP2 (2nd order intercept), HD2 (2nd order harmonic distortion), HD3 (3rd order harmonic distortion), and IIP3 can also be optimized. Moreover, the output DC offset voltage can be nulled via the serial port to allow DC coupling to the ADC for true ZIF operation. Once calibrated at room temperature, these performance metrics are remarkably stable at cold or hot, right up to the rated temperature extremes from –40 °C to 105 °C case.

The LTC5594 Typical Application
The LTC5594 Typical Application.

The LTC5594 is ideally suited for 5G microwave wireless infrastructure platforms that require 1 GHz or more bandwidth, and dynamic range performance to support the high order modulation and gigabit data rates required. In addition, the device benefits other applications such as broadband microwave point-to-point backhaul, high performance GPS systems, satellite communications, aircraft avionics, RF test equipment and radar systems. Its superb linearity and image rejection performance are particularly compelling for DPD (digital pre-distortion) receiver applications.

Gain, OIP3, and OIP2 vs Frequency
Gain, OIP3, and OIP2 vs Frequency (Unoptimized).

The LTC5594 is offered in a 32-lead, 5 mm × 5 mm plastic QFN package. The demodulator is powered from a single 5 V supply, drawing a nominal 470 mA current. The baseband amplifiers can be selectively disabled, so the demodulator can run on 250 mA current. An enable pin allows an external controller to shut down the device. When disabled, the device typically draws 20 μA supply current. Samples and production quantities are available immediately.

Demonstration circuit 2645A for the LTC5594 demodulator
Demonstration circuit 2645A for the LTC5594 demodulator.

Summary of Features: LTC5594

  • Matched RF Input Frequency 500 MHz to 9 GHz
  • I & Q Baseband Bandwidth (1 dB) 1 GHz
  • Image Rejection 37 dB Typical With Calibration 60 dB Typical
  • High Output IP3 37 dBm at 5.8 GHz
  • Adjustable Gain 8 dB in 1 dB Steps
  • Max Power Gain 9.2 dB @5.8 GHz

Pricing & Availability

Product Production Availability Price Each Per 1,000 Package
LTC5594 Now Starts at $15.70 32-Lead, 5 mm × 5 mm Plastic QFN

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