Linear Technology’s LTC5585 is an ultra-wide bandwidth direct conversion I/Q demodulator with high linearity performance (IIP3 = 25,7 dBm and IIP2 = 60 dBm at 1,95 GHz). The device is capable of baseband output demodulation bandwidth of over 530 MHz, which can support new generation wideband LTE multimode receivers’ and digital pre-distortion (DPD) receivers’ bandwidth requirements.
The device operates over a wide frequency range from 700 MHz to 3 GHz, covering virtually all cellular base station frequency bands. Unique to this device are two built-in calibration features. One is advanced circuitry that enables the system designer to optimise the receiver’s IIP2 performance, increasing from a nominal 60 dBm to 80 dBm or higher.
The other is on-chip circuitry to null out the DC offset voltages at the I and Q outputs. Both serve to enhance receiver performance. Moreover, the LTC5585 delivers P1dB of 16 dBm.
To further enhance its use in direct conversion receiver applications, the IC offers very low I/Q amplitude and phase mismatch. The amplitude mismatch is typically 0,05 dB, while the phase error is typically 0,7 degrees, both measured at 1,95 GHz. This combination produces a receiver image rejection capability of 43 dB.
Because of its very wide bandwidth capability, the LTC5585 is especially well suited for multimode LTE, W-CDMA and TD-SCDMA base stations’ DPD receivers as well as for main receiver applications. Particularly for DPD, these latest generation base stations are pushing demodulation bandwidth over 300 MHz. The LTC5585 can be easily configured to meet these bandwidth challenges.
Beyond wireless infrastructure applications, the device is well suited for applications in military receivers, broadband communications, point-to-point microwave data links, image reject receivers and long-range RFID readers. The IC has an on-chip RF transformer to reduce external components, providing a highly compact solution with its 24-lead 4 x 4 mm QFN package. It is specified for case operating temperature from -40°C to 105°C.
The LTC5585 is powered from a single 5 V supply, drawing a total supply current of 200 mA. It provides a digital input to enable or disable the chip. When disabled, the IC draws typically 11 μA leakage current. The demodulator’s fast turn-on time of 200 ns and turn-off time of 800 ns enable it to be used in burst mode receivers.
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