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Antenna load mismatch effects in EER-based transmitters for digital audio broadcast.

机译：基于EER的数字音频广播发射机中的天线负载失配效应。

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摘要

Digital Audio Broadcasting (DAB) is paving the way for the digital era of broadcasting. This is true not only for satellite transmission but also for terrestrial distribution which is using conventional Analog Modulation (AM) and Frequency Modulation (FM) bands. The accepted terrestrial DAB standard is referred to as HD Radio and was developed by iBiquity Digital. It uses orthogonal frequency division multiplexing (OFDM) signalling to transmit digital data using an in-band on-channel (IBOC) signalling. The HD Radio standard permits both digital-only and hybrid analog-digital operating modes. The large base of installed AM transmitters and the associated large investment in the design of AM transmitters has generated interest in examining the existing AM and FM analog hardware to determine where potential problems may exist in using digital signals with these systems. The spectrum re-growth causing adjacent channel interference is of special interest in this kind of investigations.;This project analyzes the antenna impedance mismatch effects of the spectrum re-growth in the hybrid AM signal at the passband as being transmitted from the broadcasting station. Antenna impedance is difficult to control and changes with weather conditions, e.g., icing on the transmitter antenna causes "complex load terminations" which increases spectral re-growth and further deteriorates the transmitted signal. Therefore, it is of interest to design AM amplifiers that are not sensitive to changes in the antenna load. This project, first documents the spectrum re-growth results when modeling the antenna load as a resonant circuit in cases of series and shunt load mismatch when the inverse Chebychev reconstruction filter is deployed in the EER amplifier. Then the work attempts to design other filters of the same order that would offer comparable spectral performance when working with the antenna impedance deviations from the nominal resistive value of 50 O. Different selectivity factors, Q, for antenna resonant circuit are considered, and the conclusion is reached that the inverse Chebychev reconstruction filter offers the most robust performance.;In the project, the AM transmitter simulation environment in Advance Design System (ADS) from Agilent Technologies was developed for various design testing purposes. The environment combines analog and digital circuitry co-simulations and will be useful for future developments in this area. The ADS simulated waveforms corresponding to AM transmission at 1.7 MHz are also verified in a hardware platform using Agilent instrumentation, which for the purpose of this project is referred to as Software Defined Instrumentation (SDI).;In preparing for the arrival of HD Radio for AM broadcast, it is important to consider the bandwidth performance of a station's antenna system. Since the majority of AM power amplifiers is using envelope elimination and restoration technique (EER) based on the pulse duration modulation, the restoration filter in the envelope path of the high power baseband signal plays a crucial role in the amplifier performance.
机译：数字音频广播（DAB）为广播的数字时代铺平了道路。这不仅适用于卫星传输，也适用于使用常规模拟调制（AM）和频率调制（FM）频段的地面分布。公认的地面DAB标准称为高清广播，由iBiquity Digital开发。它使用正交频分复用（OFDM）信令，通过带内同频（IBOC）信令传输数字数据。 HD Radio标准允许仅数字模式和混合模拟数字模式。已安装的AM发射器的庞大基础以及在AM发射器的设计上进行的大量投资引起了人们对检查现有AM和FM模拟硬件以确定在这些系统中使用数字信号时可能存在潜在问题的兴趣。在这种类型的研究中，引起相邻信道干扰的频谱重新增长特别有意义。该项目分析了从广播电台发射的通带处混合AM信号中频谱重新增长的天线阻抗失配效应。天线阻抗难以控制，并且会随天气条件而变化，例如，发射器天线上的结冰会导致“复杂的负载终端”，这会增加频谱的重新增长并进一步恶化发射信号。因此，感兴趣的是设计对天线负载变化不敏感的AM放大器。该项目首先记录了当将反向Chebychev重建滤波器部署在EER放大器中时，在串联和并联负载不匹配的情况下，将天线负载建模为谐振电路时，频谱重新增长的结果。然后，工作尝试设计相同阶数的其他滤波器，当天线阻抗偏离标称电阻值为50 O时，可以提供可比的频谱性能。考虑了天线谐振电路的不同选择性因子Q，并得出结论逆Chebychev重构滤波器可提供最强大的性能。在该项目中，Agilent Technologies的Advanced Design System（ADS）中的AM发射机仿真环境被开发用于各种设计测试目的。该环境结合了模拟和数字电路的协同仿真功能，对于该领域的未来发展将非常有用。还使用安捷伦仪器在硬件平台上验证了与1.7 MHz AM传输相对应的ADS仿真波形，在本项目中，该平台被称为软件定义仪器（SDI）。 AM广播，重要的是要考虑电台天线系统的带宽性能。由于大多数AM功率放大器使用基于脉冲持续时间调制的包络消除和恢复技术（EER），因此高功率基带信号的包络路径中的恢复滤波器在放大器性能中起着至关重要的作用。

著录项

  • 作者

    Goldy, Manmeet Singh.;

  • 作者单位

    Dalhousie University (Canada).;

  • 授予单位 Dalhousie University (Canada).;
  • 学科 Engineering Electronics and Electrical.
  • 学位 M.Eng.
  • 年度 2006
  • 页码 63 p.
  • 总页数 63
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 非洲史;
  • 关键词

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