Dual-Band Adjustable and Reactive I/Q Generator With Constant Resistance for Down- and Up-Converters

Adjustable and reactive in-phase/quadrature (I/Q) generators with constant resistance are proposed for the first time in this paper with the properties of low loss, dual-band implementation, and high quadrature accuracy. The quadrature phase property and input matching of the I/Q generator can be achieved at all frequencies simultaneously by the constant-resistance I/Q generator. However, the magnitude balance of the dual-band I/Q generator is achieved at two designed frequencies. A 2.4/5.2-GHz I/Q down-converter and a 2.4/5.7-GHz single-sideband up-converter are fabricated using 0.35-mum SiGe BiCMOS technology. The dual-band I/Q generator along with two single-to-differential amplifiers is integrated to provide differential quadrature local oscillator signals for dual-band mixers. The magnitude imbalance and phase error between the I and Q channels of the down-converter are < 1% and < 1deg, respectively, while the maximum sideband rejection ratio of the up-converter is up to 50 dB. Additionally, the operation bandwidth (sideband rejection ratio > 30 dB) is 200 MHz at 2.4 GHz and 720 MHz at 5.7 GHz.