Engineers can simplify wireless-product development by using high-performance, low-cost, surface-mount-technology (SMT) component solutions. It is essential, however, that the SMT devices be correctly interfaced to the receiver, transmitter, or transceiver circuit. In a three-page application note titled, "Integrating SMT Synthesizer Solutions into Wireless Designs," M/A-COM Technology Solutions pinpoints some areas of concern while providing analysis methodologies and possible solutions.
To minimize spurious signals from synthesizers, for example, it is critical to use clean sources of regulated DC power. The note provides a formula to calculate the quality of the necessary supply. It is recommended that the designer allow some margin in the spur specification. To achieve the needed phase-noise specifications, it also is essential to utilize low-noise regulator designs. Using the provided formula, it is possible to estimate the maximum allowable noise voltage density at a given offset. Although it is hard to relate synthesizer noise density to a regulator specification, the note shows how to make a first-order assessment if the distribution is assumed to be flat.
In a section on output load, the note emphasizes that the load will impact SMT synthesizer performance. The optimal load form comprises a resistive pad followed by an amplification stage to restore output power. Tips are provided for external-reference selection, which should consider both the waveform and level. Discussions also cover the lock detector circuit and noise contributors as well as clock, data, and load-enable outputs.M/A-COM Technology Solutions, Inc., 100 Chelmsford St., Lowell, MA 01851; (978) 656-2500, www.macomtech.com.