Linear introduces ultra-wideband wide direct conversion I/Q demodulators

     Linear Technology Corporation introduces the LTC5585, an ultra-wideband wide direct conversion I/Q demodulator with superior linear performance (IIP3 = 25.7dBm, IIP2 = 60dBm at 1.95GHz). The LTC5585 delivers more than 530MHz of baseband output demodulation bandwidth to meet the bandwidth needs of next-generation broadband LTE multimode receivers and digital predistortion (DPD) receivers.

     I/Q demodulators operate in a wide frequency range from 700MHz to 3GHz, covering almost all cell base station bands. The unique feature of this device is the two built-in calibration functions. One is advanced circuitry that allows system designers to optimize the receiver's IIP2 performance from a nominal value of 60dBm to an unprecedented 80dBm or higher. The other is an on-chip circuit that eliminates DC offset voltages on the I and Q outputs. These two functional circuits both play a role in enhancing the receiver performance.

     In addition, the LTC5585 offers an excellent 16dBm P1dB. To further enhance the device's use in direct conversion receiver applications, the LTC5585 offers very low I/Q amplitude and phase mismatch. The typical value of the amplitude mismatch is 0.05dB and the typical value of the phase error is 0.7 degrees, both values measured at the 1.95GHz frequency. The combination of these two results in a receiver mirror frequency rejection of 43dB.

     Because the LTC5585 provides a very wide bandwidth, it is particularly suitable for multi-mode LTE, W-CDMA and TD-SCDMA base station DPD receivers, as well as for master receiver applications. Especially for DPD, these latest generation base stations are pushing the demodulation bandwidth to more than 300MHz. The LTC5585 can be easily configured to meet these bandwidth challenges. In addition to wireless infrastructure applications, the LTC5585 is suitable for military receivers, broadband communications, point-to-point microwave data links, mirror frequency suppression receivers, and long-range RFID readers.

     The LTC5585 has an RF transformer built in to reduce external components and, coupled with a 24-lead 4mm x 4mm QFN package, provides a highly compact solution. The device specifications are in the housing operating temperature range of -40°C to 105°C. The LTC5585 is powered by a single 5V supply, drawing 200mA of total supply current. The device provides a digital input to enable or disable the chip. When disabled, the typical leakage current absorbed by the IC is 11uA. The modem's 200ns fast on time and 800ns off time enable the device to be used in burst-mode receivers.