Linear Technology has developed a high linearity, I/Q demodulator with more than 1 GHz bandwidth and an operating frequency range from 300 MHz to 6 GHz. The LTC5586 is a true zero-IF design that demodulates wideband RF signals directly to baseband DC or low IF. It provides superior performance, with a calibrated OIP2 of 70 dBm and 70 dBc image rejection at 3.5 GHz. The LTC5586 was designed for wireless infrastructure equipment, such as base stations, microwave backhaul, software-defined radios (SDR) and other broadband receivers.
With a single network, the LTC5586’s RF input is matched to 50 Ω from 500 MHz to 6 GHz, covering all the LTE bands and the emerging 4.5G and 5G bands at 3.6 and 5 GHz. An additional capacitor extends the match from 300 to 500 MHz. The demodulator includes an RF switch at the front end that directs one of two inputs to a programmable attenuator, controlled via the on-chip serial bus. The attenuator has a gain control range of 31 dB in 1 dB steps, allowing the receiver to accommodate a wide range of signal inputs. The demodulator consists of I and Q mixers, with their respective LO ports driven by a wideband quadrature phase shifter. After demodulation, two programmable amplifiers route the I/Q signals to external A/D converters. A maximum gain of 7.7 dB in 1 dB steps can be set by the serial port, enabling the output level to be optimized for the A/D converters. The LTC5586 also has built-in SPI tunability, allowing the demodulator to set its LO input to any frequency band from 300 MHz to 6 GHz with no external matching components.
Linear Technology Corp.