The MAX1472 is a crystal-referenced phase-locked loop transmitter designed to transmit OOK/ASK data in the 300MHz to 450MHz frequency range. It supports data rates up to 100kbps. When matched to a 50Ω system, the MAX1472 PA is capable of delivering more than +10dBm of output power while maintaining an effective efficiency greater than 43%. The crystal-based architecture of the MAX1472 eliminates many of the common problems with saw transmitters by providing greater modulation depth, faster frequency settling, higher tolerance of the transmit frequency, and reduced temperature dependence. The power amplifier (PA) of the MAX1472 is a high-efficiency open-drain class-C amplifier. With a proper output matching network, the PA can drive a wide range of impedances, including the small loop PC board trace antenna and any 50Ω antenna. Figure 1 shows a recommended matching network for a 50Ω system. The matching network transforms the 50Ω load to a higher impedance at the output of the PA in addition to forming a bandpass filter that provides attenuation for the higher order harmonics. Figure 1. MAX1472 application circuit. Table 1 shows the recommended output matching network component values for four widely used operating frequencies. These values were used with the MAX1472 evaluation kit (EV-kit). Some fine tunings may be required due to parasitic inductance and capacitance on PCB. Table 1. Output Matching Network Component Values - fRF = 315MHz fRF = 345MHz fRF = 385MHz fRF = 433.92MHz C1 15pF 10pF 10pF 7pF C2 22pF 18pF 15pF 12pF C3 15pF 15pF 12pF 10pF L1 27nH 27nH 24nH 22nH L2 22nH 18nH 18nH 15nH fXTAL 9.84375MHz 10.78125MHz 12.03125MHz 13.56000MHz Figures 2, 3, and 4 illustrate the output power and effective efficiency of the MAX1472 when configured with the above matching networks. Figure 2. Efficiency vs. supply voltage with CW tone. Figure 3. Efficiency vs. supply voltage with 50% OOK signal. Figure 4. Output power vs. supply voltage. 我们期待您的反馈！ 喜欢？不喜欢？有待改善？或为我们提供建议？请与我们联系 — 我们将根据您的意见或建议改善我们的工作。 网页评价或提供建议 自动更新 需要自动接收最新发布的应用笔记吗？请订阅EE-Mail™ (English only)。 更多信息   APP 1954: Mar 25, 2003 MAX1472 300MHz至450MHz、低功耗、基于晶振的ASK发送器 完整的数据资料 (PDF, 244kB) 免费样品   下载，PDF格式 (63kB)  AN1954, AN 1954, APP1954, Appnote1954, Appnote 1954