Description
The W3011 1 GHz Quadrature Modulator is a monolithic integrated circuit that provides direct modulation of an RF carrier by I & Q baseband inputs. It is particularly suited for use in mobile and handheld cellular telephones designed to the IS-136 (North American 824 MHz to 849 MHz), PDC (Japan RCR-STD27 889 MHz to 958 MHz), and other digital personal-communications standards.
The circuit block diagram is shown in Figure 1. From two LO signals, LOL and LOH, the offset mixer produces an internal LO signal, which prevents the external VCOs from being pulled by the large transmitted signal. The phase shifter splits the LO signal into two carriers with 90° phase separation and equal amplitude.

Features
■ Guaranteed performance at 2.7 V power supply
■ Output power of 3 dBm into 50 W load (single ended) with 3 V operation
■ Direct RF modulation with or without offset mixer
■ Automatic power control (APC) capability
■ Accurate 90° phase shifter for carrier
■ Double-balanced active mixers minimize carrier feedthrough (origin offset)
■ Low-current sleep mode

Applications
■ PDC 800 and American digital cellular mobile terminals
■ Cellular base stations