Balanced 3-phase analog signal processing for radio communications

Radio communication systems often use two analog signals as real and imaginary parts of a complex number; the two signals are usually called I and Q signals. The analog signal on an integrated circuit is usually a differential signal which is the voltage difference between positive and negative nodes. Therefore, a complex number is expressed using 4-node voltages. If a single-ended signal system is used, I and Q signals are expressed with 3-node voltage, i.e., I-signal, Q-signal, and a ground node voltage. So the 4-node system has some redundancy. However, most radio terminals employ the 4-node system, because a single-ended signal system needs a low-impedance ground node, which is troublesome on an integrated circuit. In this paper, balanced 3-phase analog signal processing and circuits for the 3-phase system are proposed. The proposed circuits are simply expanded differential circuits and expected to have small chip area because of the lower redundancy in processing a complex number. The smaller chip area means lower manufacturing cost. The proposed system is expected to reduce the cost of a radio interface