Subsystems and Systems

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Until recently, all A-GPS testing to industry standards was performed using a cabled RF connection. As a consequence, devices that pass all tests in the existing conformance standards may perform poorly in the real world, resulting in an inferior enduser experience of LBS applications. This has led some industry leaders to put in place their own A-GPS OTA solutions.

This article will begin by describing a typical Zero-IF or direct-conversion transmitter along with providing a brief introduction to digital modulation. The imperfections introduced by the modulator will be examined with particular focus on the effect of temperature and frequency changes. In-Factory and In-Field algorithms that can reduce the effect of these modulator imperfections will also be discussed. Particular focus will be placed on the efficacy of In-Factory “set-and-forget” algorithms.