4-channel/antenna multi-band RF transmitter operating from 525 MHz to 6 GHz

A multi-band transmitter front-end featuring four channels in the range from 525 MHz to 6 GHz is presented. This design is perfectly suited for convenient integration into software defined radio (SDR) applications . The transmitter features a shared selectable low phase-noise local oscillator (LO) for carrier frequency generation and 4 direct conversion I/Q-modulators that meet the specifications for spread spectrum (e.g. CDMA2000, UMTS) and OFDM(A) (e.g. WiMAX) systems. The four I/Q channel inputs are designed to be controlled by A/Dconverters. So the channels can be used for different subchannels, operated as MIMO/diversity transmitter, used for digital beam-forming or for a combination of these possibilities. The loosely packed prototype circuit has been designed on a sixlayer PCB that measures less than 40 times 80 mm without baseband connectors but including powerful voltage regulators and is thus smaller than an actual mobile handset. For phase or error vector magnitude (EVM) critical systems (especially) in the upper bands, the four transmit paths have been designed for precisely matched delays and transmit powers.