A Prototype SAW-Less LTE Transmitter with a High-Linearity Modulator Using BPF-Based I/Q Summing and a Triple-Layer Marchand Balun

A 65-nm CMOS-technology-based surface-acoustic-wave filterless transmitter (TX) for a long-term evolution (LTE) system was developed and performance tested. The TX incorporates both a passive quadrature modulator (QMOD) using bandpass filter (BPF)-based in-phase/quadrature (I/Q) signal summing and a small triple-layer Marchand balun. The passive operation and BPF-based I/Q summing, respectively, contribute to low noise performance and high input impedance (seen from the baseband signal), resulting in low receiver (RX) band noise and high linearity of the TX. The triple-layer Marchand balun contributes to the small area of the TX. A prototype LTE TX using the QMOD and the balun exhibits in-specification RX-band noise (<-161.6 dBc/Hz), a high output third-order intercept point (OIP3=20.5 dBm), and a small chip area (0.224 mm²).