Whether for global roaming, or staying on a single consolidated operator's disparate network, mobile terminals must operate in multiple modes to maintain coverage. Such mobiles have increased complexity over single mode devices, which is undesirable economically for many reasons. Problems are especially exacerbated for mobiles that must operate both full duplex for CDMA systems, and half duplex for time division systems. Conventional transmitter architectures for constant envelope half-duplex signals (e.g. GSM/GPRS) generally have little in common with conventional transmitter architectures for envelope varying full duplex signals (e.g. CDMA). By changing the signal processing coordinate system from rectangular to polar, transmitter architectures can be realized that support both constant envelope and envelope varying signals with identical RF hardware. This polar transmitter design has no requirement for linear RF circuitry, allowing circuit design to focus on maximizing efficiency rather than optimizing linearity. A strongly nonlinear multiband and multimode RF transmitter using polar signal processing is described which provides extremely linear system operation for GSM, GPRS, EDGE/EGPRS, ANSI-136, cdmaOne, and AMPS cellular signals. Measurements of all modes show outstanding performance.
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