Built-in Test of Frequency Modulated RF Transmitters Using Embedded Low-Pass Filters

Frequency modulation is used in many important communication and wireless applications. A key defining characteristic of frequency modulated systems is the constant amplitude of the transmitted signal making it impossible to use envelope-based built-in test (BIT) techniques. In this paper, an efficient BIT technique for such transmitters using lowpass filters is proposed. The proposed BIT technique is low-cost and has minimal impact on RF transmitter performance. It can also be used to efficiently test devices such as voltage-controlled oscillators (VCOs), phase locked loops (PLL) etc through frequency discrimination. Simulation results and hardware measurements demonstrate the feasibility of the proposed approach.