更多信息 - 无线主页 - 应用笔记和技术讲座 - 评估板软件 - 技术支持   摘要：基于MAX3580的DVB-T参考设计可以满足NorDig和MBRAI标准的技术指标要求。本NIM形式的参考设计包含MAX3580直接变频调谐器和一个基于COFDM的DVB-T解调器芯片。同时本设计也包含了一个基于分离器件的低功耗、低成本有源环通电路。 图1. 基于MAX3580、满足NorDig和MBRAI标准的DVB-T调谐器参考设计。 图2. 系统框图 实验室测试结果 图3. 在VHF频段，测试数据显示本参考设计相对于NorDig 1.0.2标准具有2dB以上的裕量。 图4. 在UHF频段，测试数据显示本参考设计相对于NorDig 1.0.2标准具有3.5dB至5dB的裕量。 NorDig指标比较 Parameter Conditions Measured NorDig Units Operating Frequency Range VHF-III Band: 170MHz to 230MHz – UHF Band: 470MHz to 870MHz – Sensitivity, Gaussian Channel (VHF-III Band) QPSK, 8k, CR = 1/2, GI = 1/4 -97.3 -94.6 dBm 16QAM, 8k, CR = 3/4, GI = 1/4 -88.5 -85.1 64QAM, 8k, CR = 7/8, GI = 1/4 -79.6 -77.2 Sensitivity, Gaussian Channel (UHF Band) QPSK, 8k, CR = 1/2, GI = 1/4 -96.6 -92.1 dBm 16QAM, 8k, CR = 3/4, GI = 1/4 -87.9 -82.6 64QAM, 8k, CR = 7/8, GI = 1/4 -79.6 -74.7 Maximum Input, Gaussian Channel (VHF-III Band) 64-QAM, 8k, CR = 2/3, GI = 1/8 > 0 -35 dBm 64-QAM, 8k, CR = 2/3, GI = 1/4 > 0 -35 64-QAM, 8k, CR = 3/4, GI = 1/8 > 0 -35 Maximum Input, Gaussian Channel (UHF Band) 64-QAM, 8k, CR = 2/3, GI = 1/8 > 0 -35 dBm 64-QAM, 8k, CR = 2/3, GI = 1/4 > 0 -35 64-QAM, 8k, CR = 3/4, GI = 1/8 > 0 -35 Adjacent Channel Selectivity N+1 DVB-T adjacent channel 47 ≥ 28 dBc N-1 DVB-T adjacent channel 45 N+2 DVB-T adjacent channel 47.8 ≥ 38 N-2 DVB-T adjacent channel 46 MBRAI指标比较   Case Category Measure MBRAI Units Selectivity, S1 Pattern N+1 Category a, b1 48 37 dBc N+1 Category b2, c 45 37 dBc N-1 Category a, b1 54 37 dBc N-1 Category b2, c 51 37 dBc N+2 Category a, b1 47 37 dBc N+2 Category b2, c 55 37 dBc N-2 Category a, b1 45 37 dBc N-2 Category b2, c 58 37 dBc Selectivity, S2 Pattern N+1 Category a, b1 and b2, c 39 29 dBc N-1 Category a, b1 and b2, c 38 29 dBc N+2 Category a, b1 43 40 dBc N+2 Category b2, c 45 40 dBc N-2 Category a, b1 42 40 dBc N-2 Category b2, c 44 40 dBc Linearity L1 – Category a, b1 45.5 45 dBc – Category b2, c 47 45 dBc Linearity L2 – Category a, b1 45.2 45 dBc – Category b2, c 47 45 dBc Linearity L3 – Category a, b1 40.7 40 dBc – Category b2, c 42 40 dBc 全模式下的灵敏度指标 DVB-T全模式灵敏度指标的测试是基于7个同时输入的频道。 VHF UHF Frequency (MHz) 177.5 226.5 474 570 674 770 858 QPSK, 8k, CR = 1/2, GI = 1/4 Sensitivity (dBm) -97.3 -97.3 -97.2 -97.1 -96.7 -96.5 -96.2 Max-Input (dBm) > 0 > 0 > 0 > 0 > 0 > 0 > 0 QPSK, 8k, CR = 2/3, GI = 1/4 Sensitivity (dBm) -95.9 -95.7 -95.7 -95.6 -95.3 -94.9 -94.8 QPSK, 8k, CR = 3/4, GI = 1/4 Sensitivity (dBm) -94.8 -94.8 -94.7 -94.6 -94.5 -94.1 -94 QPSK, 8k, CR = 5/6, GI = 1/4 Sensitivity (dBm) -93.8 -93.7 -93.6 -93.6 -93.3 -93 -92.8 QPSK, 8k, CR = 7/8, GI = 1/4 Sensitivity (dBm) -93.3 -93.1 -93.1 -92.7 -92.7 -92.4 -92.2 16QAM, 8k, CR = 1/2, GI = 1/4 Sensitivity (dBm) -91.7 -91.7 -91.5 -91.5 -91.4 -90.9 -90.7 16QAM, 8k, CR = 2/3, GI = 1/4 Sensitivity (dBm) -89.8 -89.7 -89.5 -89.5 -89.3 -88.9 -88.8 16QAM, 8k, CR = 3/4, GI = 1/4 Sensitivity (dBm) -88.6 -88.3 -88.4 -88.1 -88.1 -87.5 -87.3 16QAM, 8k, CR = 5/6, GI = 1/4 Sensitivity (dBm) -87.1 -87 -87 -86.9 -86.9 -86.4 -86.3 16QAM, 8k, CR = 7/8, GI = 1/4 Sensitivity (dBm) -86.4 -85.7 -86.1 -85.9 -85.7 -85.4 -85.6 64QAM, 8k, CR = 1/2, GI = 1/4 Sensitivity (dBm) -87 -86.9 -86.9 -86.6 -86.7 -86.2 -85.9 64QAM, 8k, CR = 2/3, GI = 1/4 Sensitivity (dBm) -84.1 -84.1 -83.8 -83.8 -83.7 -83.3 -83.2 64QAM, 8k, CR = 3/4, GI = 1/4 Sensitivity (dBm) -82.5 -82.2 -82.3 -82.4 -81.8 -81.5 -81.4 64QAM, 8k, CR = 5/6, GI = 1/4 Sensitivity (dBm) -80.9 -80.9 -80.7 -80.7 -80.4 -80.2 -79.8 64QAM, 8k, CR = 7/8, GI = 1/4 Sensitivity (dBm) -79.9 -79.7 -79.5 -79.5 -79 -78.9 -78.8 Max-Input (dBm) -2 -0.2 > 0 > 0 > 0 > 0 > 0 供电电流 供电电流的测试条件包含了射频输入端和TV输出端的75Ω端接负载、正常工作模式并且系统调谐至信道69 (858MHz)。 Parameter Conditions Measured Units 5V LNA Supply Current 12 mA 5V for Tuner and LNA* {8k, QPSK, CR = 1/2, GI = 1/4} 196 mA {8k, 64QAM, CR = 7/8, GI = 1/4} 196 mA 3.3V Digital Supply Current for Demodulator {8k, QPSK, CR = 1/2, GI = 1/4} 8 mA {8k, 64QAM, CR = 7/8, GI = 1/4} 10 mA 2.5V Analog Supply Current for Demodulator {8k, QPSK, CR = 1/2, GI = 1/4} 36 mA {8k, 64QAM, CR = 7/8, GI = 1/4} 36 mA 1.0V Digital Supply Current for Demodulator {8k, QPSK, CR = 1/2, GI = 1/4} 90 mA {8k, 64QAM, CR = 7/8, GI = 1/4} 92 mA 1.0V Analog Supply Current for Demodulator {8k, QPSK, CR = 1/2, GI = 1/4} 3 mA {8k, 64QAM, CR = 7/8, GI = 1/4} 3 mA *注：MAX3580所需的3.3V供电电源通过一个LDO从5V降压获得。 详细说明 本DVB-T接收电路参考设计满足NorDig 1.0.2及MBRAI标准。此电路可以用于地面接收的机顶盒，封装于NIM调谐器的尺寸之内。此参考设计覆盖了VHF-III频段(170MHz至230MHz)及UHF频段(470MHz至870MHz)，能够与一个接口板相连完成系统测试。 本参考设计包含： 一个用于实现有源环通的分离低噪声放大电路。环通具有14dB的增益和小于3.5dB的噪声系数，并且消耗60mW的功率。 一个完全集成的MAX3580硅调谐器芯片，包含低噪声放大器、射频/中频可调增益放大器、混频器以及基带低通滤波器。该调谐器芯片只需要单路3.3V供电以及少量无源器件便可完成一个完整的DVB-T射频前端电路。 一个满足DVB-T/H标准的解调芯片，可以完全支持DVB-T和DVB-H标准的帧结构、信道编码和解调。 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)。 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   下载，PDF格式 (101kB)  AN4173, AN 4173, APP4173, Appnote4173, Appnote 4173