30 January 2012
Linear introduces new wideband I/Q demodulator
Linear Technology has launched the LTC5585, an ultrawide bandwidth direct conversion I/Q demodulator with linearity performance of IIP3 = 25.7dBm and IIP2 = 60dBm at 1.95GHz.
According to Linear, the device is capable of baseband output demodulation bandwidth of over 530MHz, which can support new generation wideband LTE multimode receivers' and digital pre-distortion (DPD) receivers' bandwidth requirements.
The I/Q demodulator operates over a frequency range from 700MHz to 3GHz, covering virtually all cellular base station frequency bands. Unique to this device are two built in calibration features. One is advanced circuitry that enables system designers to optimise the receiver's IIP2 performance, increasing from a nominal 60dBm to 80dBm or higher. The other is on chip circuitry to null out the dc offset voltages at the I and Q outputs. Both are designed to serve to enhance receiver performance. The LTC5585 delivers P1dB of 16dBm.
Suitable for use in direct conversion receiver applications, the LTC5585 offers low I/Q amplitude and phase mismatch. The amplitude mismatch is typically 0.05dB, while the phase error is typically 0.7 degree, both measured at 1.95GHz. This combination produces a receiver image rejection capability of 43dB.
Because of its bandwidth capability, the LTC5585 is suitable for multimode LTE, W-CDMA and TD-SCDMA base stations DPD receivers as well as for main receiver applications. Particularly for DPD, the latest generation base stations are pushing demodulation bandwidth of more than 300MHz. The device can be easily configured to meet these bandwidth challenges. Beyond wireless infrastructure applications, Linear says the LTC5585 is ideal for applications in military receivers, broadband communications, point to point microwave data links, image reject receivers and long range rfid readers.
The device has an on chip rf transformer to reduce external components, is available in a 24 lead 4x4mm QFN package and is specified for case operating temperature from -40 to 105°C. The LTC5585 is powered from a single 5V supply, drawing a total supply current of 200mA and provides a digital input to enable or disable the chip. When disabled, the IC draws typically 11µA of leakage current. The demodulator's turn on time of 200ns and turn off time of 800ns enables it to be used in burst mode receivers.
Production quantities are now available.