Receiver performance improved with IIP2 optimization and DC offset cancellation.

February 13, 2012 – Linear Technology Korea (CEO Hong Sa-kwak) announced the release of the ultra-wideband direct conversion I/Q demodulator (product name: LTC5585), featuring outstanding linear performance (IIP3 = 25.7dBm and IIP2 = 60dBm @ 1.95GHz). This device enables a baseband output demodulation bandwidth of over 530MHz, allowing it to support the bandwidth requirements of digital pre-distortion (DPD) receivers in next-generation broadband LTE multimode receivers. Operating over a wide frequency range of 700MHz to 3GHz, this I/Q demodulator can cover virtually all mobile phone base station frequency bands. Unique features of this device include two built-in calibration functions. One is a state-of-the-art circuit that allows system designers to optimize the receiver's IIP2 performance, raising it from a nominal 60dBm to an unprecedented level of over 80dBm. Another feature is an on-chip circuit that enables the nulling of DC offset voltages at the I and Q outputs. Both improve receiver performance. In addition, the LTC5585 provides an excellent P1dB of 16dBm.
To enhance usability in direct conversion receiver applications, the LTC5585 provides very low I/Q amplitude and phase mismatch. Amplitude mismatch is typically 0.05 dB, and phase error is typically 0.7 degrees (both measured at 1.95 GHz). Based on this performance, receiver image rejection reaches 43 dB.
Due to its very wide coverage bandwidth, the LTC5585 is ideal for main receiver applications, including multimode LTE, W-CDMA, and TD-SCDMA base station DPD receivers. Particularly for DPDs, these latest generation base stations require demodulation bandwidths of over 300 MHz. The LTC5585 is easily configurable to meet these bandwidth requirements. Beyond wireless infrastructure applications, the LTC5585 is suitable for applications such as military receivers, broadband communications, P2P microwave data links, image removal receivers, and long-range RFID readers.
The LTC5585 features an on-chip RF transformer, which reduces the number of external components and enables a very compact solution in a 24-pin 4mm x 4mm QFN package. The device operates over a temperature range of -40°C to 105°C.
The LTC5585 operates on a single 5V supply with a total power consumption of 200mA. It also provides a digit input to enable/disable the chip. When disabled, it typically consumes 11μA of leakage current. With a fast turn-on time of 200ns and a turn-off time of 800ns, this demodulator can be used in burst mode receivers. The LTC5585 starts at $5.98 per unit in 1,000-piece quantities. Production-ready products are available for immediate purchase. For more information, please refer to www.linear.com/product/LTC5585 .

Photo caption: Broadband high-linearity I/Q demodulator