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[资料] 手机RF设计技巧(免费)

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发表于 2006-5-9 16:19:00 | 显示全部楼层 |阅读模式
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 楼主| 发表于 2006-5-9 16:20:00 | 显示全部楼层
<P 0pt; TEXT-ALIGN: center" align=center><B>手机</B><B><FONT face="Times New Roman">RF</FONT></B><B>设计技巧</B><B><p></p></B></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">1.       </FONT>什么是<FONT face="Times New Roman">RF</FONT>?</P><P 0pt">答:<FONT face="Times New Roman">RF </FONT>即<FONT face="Times New Roman">Radio frequency </FONT>射频,主要包括无线收发信机。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">2.       </FONT>当今世界的手机频率各是多少(<FONT face="Times New Roman">CDMA</FONT>,<FONT face="Times New Roman">GSM</FONT>、市话通、小灵通、模拟手机等)?</P><P 0pt">答:<FONT face="Times New Roman">EGSM RX: 925-960MHz, TX:880-915MHz</FONT>;
<FONT face="Times New Roman">CDMA cellular(IS-95)RX: 869-894MHz, TX:824-849MHz</FONT>。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">3.       </FONT>从事手机<FONT face="Times New Roman">Rf</FONT>工作没多久的新手,应怎样提高?</P><P 0pt">答:首先应该对<FONT face="Times New Roman">RF</FONT>系统<FONT face="Times New Roman">(</FONT>如功能性<FONT face="Times New Roman">)</FONT>有个系统的认识,然后可以选择一些芯片组,研究一个它们之间的连通性<FONT face="Times New Roman">(connectivities among them)</FONT>。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">4.       RF</FONT>仿真软件在手机设计调试中的作用是什么?</P><P 0pt">答:其目的是在实施设计之前,让设计者对将要设计的产品有一些认识。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">5.       </FONT>在设计手机的<FONT face="Times New Roman">PCB</FONT>时的基本原则是什么?</P><P 0pt">答:基本原则是使<FONT face="Times New Roman">EMC</FONT>最小化。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">6.       </FONT>手机的硬件构成有<FONT face="Times New Roman">RF/ABB/DBB/MCU/PMU</FONT>,这里的<FONT face="Times New Roman">ABB</FONT>、<FONT face="Times New Roman">DBB</FONT>和<FONT face="Times New Roman">PMU</FONT>等各代表何意?</P><P 0pt">答:<FONT face="Times New Roman">ABB</FONT>是<FONT face="Times New Roman">Analog BaseBand</FONT>,</P><P 0pt"><FONT face="Times New Roman">DBB</FONT>是<FONT face="Times New Roman">Ditital Baseband</FONT>,<FONT face="Times New Roman">MCU</FONT>往往包括在<FONT face="Times New Roman">DBB</FONT>芯片中。<FONT face="Times New Roman"> </FONT></P><P 0pt"><FONT face="Times New Roman">PMU</FONT>是<FONT face="Times New Roman">Power Management Unit,</FONT>现在有的手机<FONT face="Times New Roman">PMU</FONT>和<FONT face="Times New Roman">ABB</FONT>在一个芯片上面。将来这些芯片<FONT face="Times New Roman">(RF,ABB,DBB,MCU,PMU)</FONT>都会集成到一个芯片上以节省成本和体积。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">7.       DSP</FONT>和<FONT face="Times New Roman">MCU</FONT>各自主要完成什么样的功能?二者有何区别?</P><P 0pt">答:其实<FONT face="Times New Roman">MCU</FONT>和<FONT face="Times New Roman">DSP</FONT>都是处理器,理论上没有太大的不同。但是在实际系统中,基于效率的考虑,一般是<FONT face="Times New Roman">DSP</FONT>处理各种算法,如信道编解码,加密等,而<FONT face="Times New Roman">MCU</FONT>处理信令和与大部分硬件外设(如<FONT face="Times New Roman">LCD</FONT>等)通信。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">8.       </FONT>刚开始从事<FONT face="Times New Roman">RF</FONT>前段设计的新手要注意些什么?</P><P 0pt">答:首先,可以选择一个<FONT face="Times New Roman">RF</FONT>专题,比如<FONT face="Times New Roman">PLL</FONT>,并学习一些基本理论,然后开始设计一些简单电路,只有在调试中才能获得一些经验,有助加深理解。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">9.       </FONT>推荐<FONT face="Times New Roman">RF</FONT>仿真软件及其特点?</P><P 0pt">答:<FONT face="Times New Roman">Agilent ADS</FONT>仿真软件作<FONT face="Times New Roman">RF</FONT>仿真。这种软件支持分立<FONT face="Times New Roman">RF</FONT>设计和完整系统设计。详情可查看<FONT face="Times New Roman">Agilent</FONT>网站。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">10.   </FONT>哪里可以下载关于手机设计方案的相应知识,包括几大模快、各个模块的功能以及由此对硬件的性能要求等内容?</P><P 0pt">答:可以看看<FONT face="Times New Roman">www.gsmworld.com</FONT>和<FONT face="Times New Roman">www.139130.net</FONT>,或许有所帮助。关于<FONT face="Times New Roman">TI</FONT>的<FONT face="Times New Roman">wireless solution,</FONT>可以看看<FONT face="Times New Roman">www.ti.com</FONT>中的<FONT face="Times New Roman">wireless communications.  </FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">11.   </FONT>为什么<FONT face="Times New Roman">GSM</FONT>使用<FONT face="Times New Roman">GMSK</FONT>调制,而<FONT face="Times New Roman">W-CDMA</FONT>采用<FONT face="Times New Roman">HPSK</FONT>调制?</P><P 0pt">答:主要是由于<FONT face="Times New Roman">GSM</FONT>和<FONT face="Times New Roman">WCDMA</FONT>标准所定。有兴趣的话,可以看一些有关数字调制的书,了解使用不同数字调制技术的利与弊。<FONT face="Times New Roman">  </FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">12.   </FONT>如何解决<FONT face="Times New Roman">LCD model</FONT>对<FONT face="Times New Roman">RF</FONT>的干扰<FONT face="Times New Roman">?</FONT></P><P 0pt">答:<FONT face="Times New Roman">PCB</FONT>设计过程中,可以在单个层中进行<FONT face="Times New Roman">LCD</FONT>布线。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">13.   </FONT>手机设计过程中,在新增加的功能里,基带芯片发射数据时对<FONT face="Times New Roman">FM</FONT>产生噪声干扰,如何解决这个问题?</P><P 0pt">答:检查<FONT face="Times New Roman">PCB</FONT>设计,找到干扰源并加强隔离。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">14.   </FONT>在做手机<FONT face="Times New Roman">RF</FONT>收发部分设计时,如何解决<FONT face="Times New Roman">RF</FONT>干扰问题?</P><P 0pt">答:<FONT face="Times New Roman">GSM </FONT>手机是<FONT face="Times New Roman">TDMA</FONT>工作方式,<FONT face="Times New Roman">RF</FONT>收发并不是同时进行的,减少<FONT face="Times New Roman">RF</FONT>干扰的基本原则是一定要加强匹配和隔离。在设计时要考虑到发射机处于大功率发射状态,与接收机相比更容易造成干扰,所以一定要特别保证<FONT face="Times New Roman">PA</FONT>的匹配。另外<FONT face="Times New Roman">RF</FONT>前端<FONT face="Times New Roman">filter</FONT>的隔离也是一个重要的指标。<FONT face="Times New Roman">PCB</FONT>板一般是<FONT face="Times New Roman">6</FONT>层或<FONT face="Times New Roman">8</FONT>层,必须要有足够的<FONT face="Times New Roman">ground plane</FONT>以减少<FONT face="Times New Roman">RF</FONT>干扰。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">15.   </FONT>如何消除<FONT face="Times New Roman">GSM</FONT>突发干扰?</P><P 0pt">答:在<FONT face="Times New Roman">PCB</FONT>布线时,要把数字和射频部分很好的隔离开,必须保证好的<FONT face="Times New Roman">ground plane</FONT>。一些电源和信号线必须进行有效的电容滤波。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">16.   </FONT>如何解决<FONT face="Times New Roman">RF</FONT>的电源干扰<FONT face="Times New Roman">?</FONT></P><P 0pt">答:必须确保<FONT face="Times New Roman">RF</FONT>电源已经很好地滤波。如有必要,可以对不同的<FONT face="Times New Roman">RF</FONT>线路使用单独的电源。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">17.   </FONT>有<FONT face="Times New Roman">RF</FONT>应用电路,在<FONT face="Times New Roman">RF</FONT>部分不工作的时候<FONT face="Times New Roman">CPU</FONT>及其它相关外设工作正常;可是当<FONT face="Times New Roman">RF</FONT>启动工作时候,<FONT face="Times New Roman">CPU</FONT>与<FONT face="Times New Roman">RF</FONT>无关的端口也受到了类似于尖脉冲的干扰。请问,是什么原因造成的?怎样克服这样的干扰?</P><P 0pt">答:可能是<FONT face="Times New Roman">RF</FONT>部分没有很好地与<FONT face="Times New Roman">CPU</FONT>部分隔离,请检查<FONT face="Times New Roman">PCB</FONT>版图。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">18.   </FONT>选择手机射频芯片时,主要考虑哪些问题?</P><P 0pt">答:在选择射频芯片时主要考虑以下几点:</P><P 0pt 0pt 0pt 39pt; TEXT-INDENT: -18pt; mso-list: l0 level2 lfo1; tab-stops: list 39.0pt"><FONT face="Times New Roman">①     </FONT>射频性能,包括可靠性。<FONT face="Times New Roman"> </FONT></P><P 0pt 0pt 0pt 39pt; TEXT-INDENT: -18pt; mso-list: l0 level2 lfo1; tab-stops: list 39.0pt"><FONT face="Times New Roman">②     </FONT>集成度高,需要少的外围原器件。</P><P 0pt 0pt 0pt 39pt; TEXT-INDENT: -18pt; mso-list: l0 level2 lfo1; tab-stops: list 39.0pt"><FONT face="Times New Roman">③     </FONT>成本因素。</P><P 0pt 0pt 0pt 21pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">19.   </FONT>如何利用手机射频芯片减少外围芯片的数量?</P><P 0pt">答:手机射频芯片集成度越高,所需要的外围元启件就越少。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">20.   </FONT>射频芯片对于外围芯片会不会产生电磁干扰,应该怎么消除?</P><P 0pt">答:应该说是射频系统会对其他<FONT face="Times New Roman">DBB,ABB</FONT>产生电磁干扰,而不仅是射频芯片。加强射频屏蔽是一个有效的措施。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">21.   </FONT>在无线通信系统中,基带的时域均衡,是否应该位于基带解调并进行位同步抽去后,对每一个位抽取的结果,经过时域均衡,再进行门限判决?</P><P 0pt">答:是的。需要先经过均衡,再进行门限判决。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">22.   </FONT>相同的发射功率,在频率不一样时,是否频率高的(如<FONT face="Times New Roman">900MHz</FONT>)传输距离远,频率低(如<FONT face="Times New Roman">30MHz</FONT>)传输距离短(在开阔地带)?</P><P 0pt">答:应该考虑到波长因素。频率越高,波长越短,在开阔地带,传输损耗越大,因此传输距离较短。</P><P 0pt"><FONT face="Times New Roman"> </FONT></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">23.   </FONT>用定时器<FONT face="Times New Roman">1</FONT>来产生波形,其程序如下:<FONT face="Times New Roman"> </FONT></P><P 0pt"><FONT face="Times New Roman">LDP #232 </FONT></P><P 0pt"><FONT face="Times New Roman">SPLK #0Ah,T1PR </FONT></P><P 0pt"><FONT face="Times New Roman">SPLK #05h,T1CMPR </FONT></P><P 0pt"><FONT face="Times New Roman">SPLK #0000h,T1CNT </FONT></P><P 0pt"><FONT face="Times New Roman">SPLK #0042h,GPTCON </FONT></P><P 0pt"><FONT face="Times New Roman">SPLK #0D542h,T1CON</FONT></P><P 0pt">为什么在<FONT face="Times New Roman">T1PWM/T1CMP</FONT>引脚上没有波形输出?</P><P 0pt">答:可以使用仿真工具进入代码来调试这个问题。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">24.   </FONT>“手机接收机前端滤波器带宽根据接收频率的带宽来决定<FONT face="Times New Roman">,</FONT>必须保证带内信号以最小的插损通过,不被滤除掉。”<FONT face="Times New Roman"> </FONT>在满足能有效接收信号的情况下,对前端滤波器,如果滤波器带宽比较宽,那么滤波器的插损就小(对<FONT face="Times New Roman">SAW</FONT>不知是不是也是这样),但带内噪声就增加,反之相反。那么在给定接收信号频率范围的情况下,应该如何来考虑滤波器的带宽,使带内信号以最小的插损通过?</P><P 0pt">答:应该从系统设计的角度考虑这个问题,包括频率范围<FONT face="Times New Roman">(frequency range,sensitivity)</FONT>和感度<FONT face="Times New Roman">(selectivity)</FONT>等。可以在插损<FONT face="Times New Roman">(insertion loss)</FONT>、带宽<FONT face="Times New Roman">(bandwidth)</FONT>和带外抑制<FONT face="Times New Roman">(out of band rejection)</FONT>之间取得折衷<FONT face="Times New Roman">, </FONT>只要选择的值符合系统需求,就可以了。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">25.   </FONT>一般来说<FONT face="Times New Roman">PA</FONT>、<FONT face="Times New Roman">SWITH</FONT>有一定抑制杂散辐射的能力,但有一定的限制,如何增加其它的方法来更好的解决?</P><P 0pt">答:准确的说法应该是<FONT face="Times New Roman">PA</FONT>的匹配滤波有一定抑制杂散辐射的能力,另外可以选择好的前端<FONT face="Times New Roman">Filter </FONT>以加强带外抑制。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">26.   </FONT>如何选用<FONT face="Times New Roman">RF</FONT>的<FONT face="Times New Roman">LDO?</FONT></P><P 0pt">答:选用<FONT face="Times New Roman">LDO</FONT>时,应考虑其自身所具备的某些特性,如<FONT face="Times New Roman">driving current</FONT>、输出噪声和纹波抑制<FONT face="Times New Roman">(ripple rejection)</FONT>等。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">27.   </FONT>用什么方法可以降低射频系统在待机时的功耗?</P><P 0pt">答:可以在手机听网络<FONT face="Times New Roman">paging</FONT>信息间隙把射频系统关掉。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">28.   TI</FONT>推出的<FONT face="Times New Roman">TRF6151</FONT>芯片采用直接变频技术,会不会导致其他问题?</P><P 0pt">答:<FONT face="Times New Roman">TI</FONT>推出的<FONT face="Times New Roman">TRF6151</FONT>芯片是单芯片<FONT face="Times New Roman">GSM tranceiver,</FONT>采用零中频接收机结构。直接变频技术现在已经很成熟了,不存在技术问题,而且还是目前的主流方案。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">29.   TI</FONT>提供的手机方案在软件方面与<FONT face="Times New Roman">Symbian</FONT>公司有什么关系<FONT face="Times New Roman">?</FONT></P><P 0pt">答:<FONT face="Times New Roman">TI</FONT>的无线<FONT face="Times New Roman">PDA</FONT>方案及<FONT face="Times New Roman">OMAP</FONT>支持包括<FONT face="Times New Roman">Symbian</FONT>的<FONT face="Times New Roman">EPOC</FONT>在内的多种操作系统。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">30.   </FONT>在手机<FONT face="Times New Roman">RF</FONT>电路中,信号传输线路上一般会串联一个<FONT face="Times New Roman">33pF</FONT>的电容,这是为什么?</P><P 0pt">答:一般而言,串联一个<FONT face="Times New Roman">33pF</FONT>的电容目的是隔直和耦合。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">31.   </FONT>据报道<FONT face="Times New Roman">TI</FONT>已开发出单芯片手机,请问在单芯片中如何实现<FONT face="Times New Roman">BB</FONT>与<FONT face="Times New Roman">RF</FONT>的隔离,与传统分立模块设计的要求有何不同?</P><P 0pt">答:<FONT face="Times New Roman">TI </FONT>计划于<FONT face="Times New Roman">2004</FONT>年推出单芯片手机方案。传统分立模块设计可以通过选择更好性能的外围器件,以及通过好的<FONT face="Times New Roman">PCB</FONT>布线来加强<FONT face="Times New Roman">BB</FONT>与<FONT face="Times New Roman">RF</FONT>的隔离,有很大的灵活性。而单芯片方案中<FONT face="Times New Roman">BB</FONT>与<FONT face="Times New Roman">RF</FONT>的有效隔离是由<FONT face="Times New Roman">IC</FONT>设计技术来保证的,<FONT face="Times New Roman">TI</FONT>在这方面已经积累了丰富的经验。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">32.   </FONT>手机设计时,如何减少传导杂散发射和辐射杂散发射?</P><P 0pt">答:要减少杂散发射,应该从线路设计和<FONT face="Times New Roman">PC</FONT>B设计这两个方面考虑。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">33.   </FONT>可否采用屏蔽罩来阻止辐射杂散发射?</P><P 0pt">答:可以。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">34.   </FONT>手机与基站通信中产生的<FONT face="Times New Roman">TDMA</FONT>噪声<FONT face="Times New Roman">Burst Noise</FONT>对于射频部分有影响。在选择射频芯片的时候,单从技术的角度出发,主要是看那些方面的指标?</P><P 0pt">答:首先对于接收机而言,应注意的指标包括:接收灵敏度、选择性、阻塞、交调等。对于发射机而言,包括输出功率、频谱特性、杂散、频率相位误差等。<FONT face="Times New Roman">TDMA </FONT>噪声主要影响手机的音频部分。要避免这种噪声,应该注意<FONT face="Times New Roman">PCB</FONT>设计,如音频部分布线。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">35.   3</FONT>阶截点和<FONT face="Times New Roman">1db</FONT>增益压缩点是越大越好吗?如果不是,大概应该在一个什么样的值才比较合适?</P><P 0pt">答;对于<FONT face="Times New Roman">3</FONT>阶截点和<FONT face="Times New Roman">1db</FONT>增益压缩点,并不是越大越好,而是足够满足设计要求即可,因为必须考虑成本因素,越大就意味着芯片的价格越高。<FONT face="Times New Roman">GSM900 IIP3 </FONT>在<FONT face="Times New Roman">-17dBm</FONT>应该足够满足要求。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">36.   </FONT>在整体设计手机系统时,怎样考虑射频芯片的电磁兼容性能?</P><P 0pt">答:考虑射频芯片的电磁兼容性能,必须加强射频屏蔽。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">37.   </FONT>在<FONT face="Times New Roman">RFIC</FONT>中,<FONT face="Times New Roman">DC Offset Cancellation</FONT>是怎样的原理?</P><P 0pt">答:<FONT face="Times New Roman">DC</FONT>偏移电压会影响直接转换接收机中的<FONT face="Times New Roman">BER</FONT>性能。<FONT face="Times New Roman">DC</FONT>偏移电压出自<FONT face="Times New Roman">LO</FONT>自混频等,因此必须在接收信号之前消除它。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">38.   GSM</FONT>手机使用非线性功放,而<FONT face="Times New Roman">W-CDMA</FONT>必须使用线性功放,这是为什么?</P><P 0pt">答:这主要是由调制技术决定的。<FONT face="Times New Roman">GSM</FONT>采用<FONT face="Times New Roman">GMSK</FONT>调制,可以使用非线性功放,提高效率。而<FONT face="Times New Roman">W-CDMA</FONT>采用<FONT face="Times New Roman">HPSK</FONT>调制<FONT face="Times New Roman">,</FONT>则必须使用线性功放,减少失真。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">39.   </FONT>手机接收机前端滤波器带宽是如何确定的?</P><P 0pt">答:手机接收机前端滤波器带宽根据接收频率的带宽来决定<FONT face="Times New Roman">,</FONT>必须保证带内信号以最小的插损通过,不被滤除掉。例如,<FONT face="Times New Roman">GSM900</FONT>接收机频率范围为<FONT face="Times New Roman">880-915MHz</FONT>。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">40.   </FONT>手机接收前端放大需考虑什么因素来设计,要求至少放大多少<FONT face="Times New Roman">dB</FONT>,<FONT face="Times New Roman">TI</FONT>公司相对应的器件如何找到?</P><P 0pt">答:需要考虑手机接收前端<FONT face="Times New Roman">LNA</FONT>的<FONT face="Times New Roman">gain,P1dB,IP3,NF,frequency range </FONT>等,在<FONT face="Times New Roman">TI</FONT>方案中,<FONT face="Times New Roman">gain </FONT>在<FONT face="Times New Roman">17dB </FONT>左右。<FONT face="Times New Roman">TI</FONT>有<FONT face="Times New Roman">Superheterodyne,zero-IF</FONT>方案。你可以登录<FONT face="Times New Roman">www.ti.com</FONT>查看<FONT face="Times New Roman">GSM transceiver TRF6053,TRF6150,TRF6151</FONT>。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">41.   </FONT>手机待机时间的长短如果在电池容量一定的情况下主要可从哪几方面使待机时间增加?</P><P 0pt">答:从以下两个方面:</P><P 0pt 0pt 0pt 39pt; TEXT-INDENT: -18pt; mso-list: l0 level2 lfo1; tab-stops: list 39.0pt"><FONT face="Times New Roman">①     </FONT>工作模式下<FONT face="Times New Roman">RX</FONT>、<FONT face="Times New Roman">DBB</FONT>和<FONT face="Times New Roman">ABB</FONT>的功耗,对于这些模块而言,功耗因解决方案而异。</P><P 0pt 0pt 0pt 39pt; TEXT-INDENT: -18pt; mso-list: l0 level2 lfo1; tab-stops: list 39.0pt"><FONT face="Times New Roman">②     </FONT>解决方案的电源管理机制,一个好的解决方案应该做到在待机模式中尽可能关闭更多的功能块。</P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">42.   </FONT>准备设计一个新款手机,即能登陆公网,又能在小范围内独立组网,该怎么做?</P><P 0pt">答:可以设计一种双模手机,一个模式使用<FONT face="Times New Roman">GSM</FONT>或<FONT face="Times New Roman">CDMA</FONT>技术接入公众网,另一个模式使用私有网络技术。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">43.   </FONT>在设计一款<FONT face="Times New Roman">CDMA 1X</FONT>手机时,测试过程中,发现天线无线灵敏度指标不是很理想(<FONT face="Times New Roman">-103db</FONT>)<FONT face="Times New Roman">,</FONT>而天线有线灵敏度指标还可以(<FONT face="Times New Roman">-108db</FONT>),能否通过更改<FONT face="Times New Roman">PCB</FONT>设计(<FONT face="Times New Roman">RF GND</FONT>)进行改良或者在天线端重新进行匹配?</P><P 0pt">答:可按以下程序进行检查:</P><P 0pt 0pt 0pt 39pt; TEXT-INDENT: -18pt; mso-list: l0 level2 lfo1; tab-stops: list 39.0pt"><FONT face="Times New Roman">①     </FONT>检查天线性能是否完好。</P><P 0pt 0pt 0pt 39pt; TEXT-INDENT: -18pt; mso-list: l0 level2 lfo1; tab-stops: list 39.0pt"><FONT face="Times New Roman">②     </FONT>如果天线没有问题,将天线匹配调至最佳。</P><P 0pt">如有需要,可以修改<FONT face="Times New Roman">PCB</FONT>布线以提高匹配性能。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">44.   </FONT>如何为适当的锁定时间选择<FONT face="Times New Roman">LPF</FONT>值?</P><P 0pt">答:首先根据设定的锁定时间,估计<FONT face="Times New Roman">LPF</FONT>带宽,然后计算<FONT face="Times New Roman">LPF R</FONT>、<FONT face="Times New Roman">C</FONT>值。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">45.   </FONT>如果未锁定<FONT face="Times New Roman">PLL</FONT>,如何调整<FONT face="Times New Roman">PLL</FONT>以稳定锁相回路?</P><P 0pt">答:如果<FONT face="Times New Roman">PLL</FONT>处于解锁状态,请使用开路分析<FONT face="Times New Roman">(open loop analysis)</FONT>检查环路<FONT face="Times New Roman">(loop)</FONT>稳定性。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">46.   </FONT>如果相位边限<FONT face="Times New Roman">(phase margin)</FONT>改变,杂散<FONT face="Times New Roman">(spurious)</FONT>会不会改变?</P><P 0pt">答:如果相位边限改变了,很可能<FONT face="Times New Roman">LPF</FONT>带宽也会改变,那么杂散也将改变。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">47.   </FONT>在校准<FONT face="Times New Roman">AGC</FONT>参数时,如何更好地兼顾不同信道的增益平坦度?</P><P 0pt">答:首先应考虑前端部分的带内平坦度,在此基础上,可以将整个<FONT face="Times New Roman">RX</FONT>频带划分成若干子带以补偿带内波动。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">48.   </FONT>为什么<FONT face="Times New Roman">RITA</FONT>要用内部和外部两套参考源?有什么区别?哪个更好?可否改为<FONT face="Times New Roman">13MHz</FONT>参考源?</P><P 0pt">答:使用<FONT face="Times New Roman">Rita</FONT>系统,可以有两种选择:使用内部<FONT face="Times New Roman">VCXO</FONT>电路,或者使用外部<FONT face="Times New Roman">VCXO</FONT>模块。两种方法都可以,只是成本不同。不管用哪一种方法,都应该使用<FONT face="Times New Roman">26MHz</FONT>参考时钟。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">49.   </FONT>目前零中频接收机的技术已经成熟了吗?</P><P 0pt">答:目前零中频接收机的技术已经成熟,已经有大量的手机在市场上销售。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">50.   </FONT>现在基带处理好多用零中频,什么是零中频技术?</P><P 0pt">答:零中频<FONT face="Times New Roman">(Zero-IF)</FONT>是目前接收器设计中最常用的技术,采用这种技术则无须使用<FONT face="Times New Roman">IF LO</FONT>,并可将射频直接转换为<FONT face="Times New Roman">BB</FONT>信号。这种技术可以说是一种高成本效益且灵活的解决方案,可在同一<FONT face="Times New Roman">RF</FONT>设计中适应不同通信标准。</P><P 0pt">附:英文回答原文如下:</P><P 0pt"><FONT face="Times New Roman">Zero-IF is the most common technology currently used in receiver design which eliminates the IF LO and converts directly the RF to BB signal. It's a cost effective and flexible solution which can accommodate different communication standards in the same RF design.</FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">51.   </FONT>在零中频接收机中,直流电压失调一般是如何解决的?</P><P 0pt">答:直流电压失调已经不在是阻碍零中频商用的原因,可以被校准掉。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">52.   </FONT>什么方法可以测试手机互调?</P><P 0pt">答:可以使用两个信号发生器同时生成目标信号和干扰信号来进行测试。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">53.   </FONT>协议规定的手机静态灵敏度为<FONT face="Times New Roman">-102dBm</FONT>,但有些厂家号称可以做到<FONT face="Times New Roman">-106dBm</FONT>或更高,请问<FONT face="Times New Roman">TI</FONT>的解决方案中,假设采用普通的前端和混频、中放等电路,可以做到多少?</P><P 0pt">答:采用<FONT face="Times New Roman">TI</FONT>的解决方案,<FONT face="Times New Roman">EGSM</FONT>下可以做到<FONT face="Times New Roman"> -108dBm</FONT>。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">54.   </FONT>有什么更好的系统设计方法可以提高静态灵敏度?</P><P 0pt">答:要提高灵敏度,必须减少系统<FONT face="Times New Roman">NF</FONT>,可以提高前端匹配并选择低插损组件。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">55.   </FONT>在点测时,<FONT face="Times New Roman">PHASE PEAK</FONT>、<FONT face="Times New Roman">RMS</FONT>指标合格,但在场测时(耦合测试)上述指标不合格,在<FONT face="Times New Roman">GSM</FONT>与<FONT face="Times New Roman">DCS</FONT>都存在上述问题!怎么办?</P><P 0pt">答:应该检查一下设计,<FONT face="Times New Roman">TX</FONT>部分的某些关键电路可能没有足够的设计余量<FONT face="Times New Roman">(design margin)</FONT>,它对外部干扰非常敏感。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">56.   </FONT>在<FONT face="Times New Roman">RITA</FONT>上,有一个<FONT face="Times New Roman">bandgap voltage output</FONT>管脚,推荐线路用电容接地,请问什么含义?在手机整个线路中有什么可以扩展的作用或功能?</P><P 0pt">答:电容起滤波作用,抑制<FONT face="Times New Roman">bandgap</FONT>的噪声输出。该管脚输出在<FONT face="Times New Roman">Rita</FONT>内部用于<FONT face="Times New Roman">LDO</FONT>电压参考,不应联接到其他外部电路,用于其他用途。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">57.   What is the requirement for phase noise at 1k offset, 10kHz offset, and 100kHz offset for GSM handset? GSM</FONT>手机的相位噪声为<FONT face="Times New Roman">1k</FONT>、<FONT face="Times New Roman">10kHz</FONT>和<FONT face="Times New Roman">100kHz</FONT>的情况下,需要满足什么条件?</P><P 0pt">答:<FONT face="Times New Roman">For GSM handset RX it has several architectures to implement: Superheterodyne,near zero-IF,zero-IF,different architecture may have different </FONT></P><P 0pt"><FONT face="Times New Roman">LOs requirement and frequency plan,also it's related to the design of filters.</FONT></P><P 0pt">对于<FONT face="Times New Roman">GSM</FONT>手机<FONT face="Times New Roman">RX</FONT>,需要实现:超外差接近于零中频<FONT face="Times New Roman">(zero-IF)</FONT>。不同架构的零中频不同。<FONT face="Times New Roman">Los</FONT>要求以及频率规划<FONT face="Times New Roman">(frequency plan)</FONT>,这与滤波器的设计有关。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">58.   </FONT>接受机在接受灵敏度很高的情况下静态音质量很好,而在一定移动时却不好,可能是什么原因?</P><P 0pt">答:可能是<FONT face="Times New Roman">fading</FONT>的影响。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">59.   </FONT>决定一个射频电路设计是否能够量产的关键因素有哪些<FONT face="Times New Roman">?</FONT></P><P 0pt">答:在大量生产时要求射频性能一致、可靠、稳定,没有离散性,并且满足生产工艺的要求。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">60.   </FONT>请问在<FONT face="Times New Roman">TI</FONT>的解决方案中<FONT face="Times New Roman">, DSP</FONT>软件是否与<FONT face="Times New Roman">MCU</FONT>软件共用同一操作系统<FONT face="Times New Roman">?</FONT></P><P 0pt">答:在<FONT face="Times New Roman">TI</FONT>的解决方案中,以至于所有的解决方案中,<FONT face="Times New Roman">DSP</FONT>软件都不能和<FONT face="Times New Roman">MCU</FONT>软件共用一个操作系统。它们虽然集成在一个芯片上,但是属于独立的模块,相当于两个独立的处理器。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">61.   </FONT>如何降低<FONT face="Times New Roman">spectrum_switch</FONT>?</P><P 0pt">答:如果是闭环功率控制,必须注意<FONT face="Times New Roman">PA</FONT>输出功率检测电路能够满足<FONT face="Times New Roman">GSM</FONT>动态范围。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">62.   </FONT>手机的切换频率很快,以前我们所用的手机一般用两个锁相环来锁频,现在在单芯片系统中,只用一个锁相环,采用<FONT face="Times New Roman">N</FONT>分数锁频技术,请问一般时间控制在多少秒比较合适?</P><P 0pt">答:锁定时间取决于具体应用,小于<FONT face="Times New Roman">250us</FONT>可以满足<FONT face="Times New Roman">gprs class 12 </FONT>的要求。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">63.   </FONT>在设计初期和后期的<FONT face="Times New Roman">pcb</FONT>调试中应该注意那些问题?</P><P 0pt">答:需要调整<FONT face="Times New Roman">burst ramp up </FONT>和<FONT face="Times New Roman"> ramp down</FONT>的功率控制。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">64.   TI</FONT>可否提供<FONT face="Times New Roman">MMI</FONT>的源代码?</P><P 0pt">答:一般情况下,<FONT face="Times New Roman">TI</FONT>将<FONT face="Times New Roman">MMI</FONT>源代码与某些驱动器<FONT face="Times New Roman">(LCD</FONT>等<FONT face="Times New Roman">)</FONT>源代码一同提供给用户。包括<FONT face="Times New Roman">MMI</FONT>、协议堆栈和<FONT face="Times New Roman">layer1</FONT>源代码在内的所有源代码将根据业务关系决定是否提供。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">65.   </FONT>怎样解决高频<FONT face="Times New Roman">LC</FONT>振荡电路的二次谐振或者多次谐振?</P><P 0pt">答:可以改善振荡器反馈网络的频率选择性,或者利用输入匹配电路以削弱谐波。</P><P 0pt">附:相关英文回答原文:</P><P 0pt"><FONT face="Times New Roman">You can improve the frequency selectivity of oscillator feedback network or take advantage of the output matching circuitry to attenuate the harmonics.</FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">66.   RF</FONT>端口匹配结果好坏直接影响<FONT face="Times New Roman">RF</FONT>链路的信号质量。如何最快最好地调试这些匹配电路?</P><P 0pt">答:第一步:可以基于电路板设计使用网络分析仪测量实际的<FONT face="Times New Roman">S</FONT>参数,并将其输入到<FONT face="Times New Roman">RF</FONT>仿真<FONT face="Times New Roman">SW</FONT>中,以获得初始的匹配网络。<FONT face="Times New Roman"> </FONT></P><P 0pt">第二步:可以基于匹配网络的仿真结果,在板上做一些进一步的优化工作。<FONT face="Times New Roman"> </FONT></P><P 0pt">附:相关英文回答:</P><P 0pt"><FONT face="Times New Roman">Step 1: You can measure the actual S parameters using network analyser based on your board design and input it to the RF simulation SW to get the initial matching network. </FONT></P><P 0pt"><FONT face="Times New Roman">step 2: Based on the simulation result of matching network you can do some further optimization work on your board.  </FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">67.   </FONT>手机电路画电路板时,如何解除<FONT face="Times New Roman">DC-DC CONVERTER</FONT>对<FONT face="Times New Roman">RF</FONT>电路的影响?</P><P 0pt">答:可以增加电容来滤除对直流线路的影响,也可以使用针对<FONT face="Times New Roman">RF</FONT>线路的专用<FONT face="Times New Roman">LDO</FONT>。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">68.   RF</FONT>通行的最远能达到<FONT face="Times New Roman">1</FONT>公里或更远吗?</P><P 0pt">答:这由<FONT face="Times New Roman">RF</FONT>频率、发射功率和天线等因素决定。并非固定距离。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">69.   </FONT>在设计如<FONT face="Times New Roman">wireless LAN card </FONT>的时候常会使用屏蔽罩用以屏蔽掉<FONT face="Times New Roman">RF</FONT>部分的辐射。这样做会增加成本。有什么办法可以少用甚至不用屏蔽罩?</P><P 0pt">答:可将高功率<FONT face="Times New Roman">RF</FONT>信号置于<FONT face="Times New Roman">PCB</FONT>中间层,并确保良好接地以减少散射。但是屏蔽罩仍是保证稳定发射性能的首选。</P><P 0pt"><FONT face="Times New Roman">You can put high power RF signal in the middle layer of PCB and make sure have good grounding to reduce the radiation,but shielding can is still the preferred way to gurantee the stable radiation performance.</FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">70.   10</FONT>~<FONT face="Times New Roman">30mV</FONT>的有用信号:放大<FONT face="Times New Roman">100</FONT>~<FONT face="Times New Roman">120dB</FONT>后,有用信号达到峰峰值<FONT face="Times New Roman">3V</FONT>~<FONT face="Times New Roman">~4V</FONT>,但噪声信号也达到了<FONT face="Times New Roman">300mV</FONT>左右,但实际要求噪声信号在<FONT face="Times New Roman">20mV</FONT>以下,如何解决?(前级放大问题不明显,矛盾不突出,关键到最后一级放大后,问题就出现了。)</P><P 0pt">答:首先要确保有用信号有非常好的信噪比,然后才将其输入放大器链,接着计算获得目标信号振幅和噪声水平所需的增益与<FONT face="Times New Roman">NF</FONT>的大小,最后根据这些数据选择合适的器件设计放大器链路。</P><P 0pt"><FONT face="Times New Roman">First please make sure the useful signal has very good SNR before you input it to amplifiers chain,then you can calculate how much gain and NF you need to get the targeted signal amplitude and noise level, based on this you can choose the right components to design amplifiers chain.  </FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">71.   </FONT>在开发<FONT face="Times New Roman">WLAN</FONT>的<FONT face="Times New Roman">PCB Layou</FONT>时候,怎样匹配或计算线路为<FONT face="Times New Roman">50ohm.</FONT>?</P><P 0pt">答:<FONT face="Times New Roman">50ohm</FONT>匹配由<FONT face="Times New Roman">PCB</FONT>层叠决定。将<FONT face="Times New Roman">PCB</FONT>参数<FONT face="Times New Roman">(</FONT>层厚度、<FONT face="Times New Roman">)</FONT>使用<FONT face="Times New Roman">RF</FONT>仿真工具计算阻抗、<FONT face="Times New Roman">line thickness</FONT>和<FONT face="Times New Roman">line width</FONT>。</P><P 0pt"><FONT face="Times New Roman">You can calculate the impedance using RF simulation tools by setting PCB parameters like layer thickness, line thickness and line width.</FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">72.   </FONT>如果线路匹配不好,怎样在网络分析仪下计算所匹配的元件(<FONT face="Times New Roman">L </FONT>,<FONT face="Times New Roman">C</FONT>)?</P><P 0pt">答:如果线路不匹配,可以使用网络分析仪测量<FONT face="Times New Roman">S</FONT>参数,并借助史密斯圆图使用<FONT face="Times New Roman">LC</FONT>元件来补偿这种不匹配。</P><P 0pt"><FONT face="Times New Roman">If there's mismatching you can use network analyser to measure the S-parameters and use LC conponents to compensate the mismatch using Smith chart.</FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">73.   </FONT>在网房中测试<FONT face="Times New Roman">LNA</FONT>接收灵敏度,测试点应该选择哪儿点上最佳?</P><P 0pt">答:通常测试<FONT face="Times New Roman">RX</FONT>灵敏度,而不测试<FONT face="Times New Roman">LNA</FONT>灵敏度。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">74.   </FONT>在射频电路比如放大器的设计中,其管子的信号地与偏置电路的电源地是否分开为好,或者至少在同一层分开?<FONT face="Times New Roman"> </FONT></P><P 0pt">答:一般不需要分开信号地和电源地。<FONT face="Times New Roman">  </FONT></P><P 0pt"><FONT face="Times New Roman">Normally you don't need to seperate the ground of power supply with the ground of amplifier</FONT>。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">75.   </FONT>不少射频<FONT face="Times New Roman">PCB</FONT>布板在空域即无元件和走线的地方没有布大面积地,这如何解释?在微波频段是否应不一样?</P><P 0pt">答:可以在<FONT face="Times New Roman">DC</FONT>线路上加足数的小电器。</P><P 0pt"><FONT face="Times New Roman">you can add enough small capacitors on DC line.</FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">76.   </FONT>目前有没有置于低温环境中的放大器管子外销?</P><P 0pt">答:放大器的工作温度范围应该在<FONT face="Times New Roman">-10</FONT><st1:chmetcnv w:st="on" TCSC="0" NumberType="1" Negative="True" HasSpace="False" SourceValue="8" UnitName="℃"><FONT face="Times New Roman">-8</FONT>℃</st1:chmetcnv>,可以查看参数表,上面的规定应该也是如此。</P><P 0pt"><FONT face="Times New Roman">For amplifier it should have its working temperature range like -10<st1:chmetcnv w:st="on" TCSC="0" NumberType="1" Negative="True" HasSpace="False" SourceValue="85" UnitName="C">-85c</st1:chmetcnv>, you can check the datasheet,it should have this specification.</FONT></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">77.   </FONT>手机<FONT face="Times New Roman">RF IC</FONT>处理信号的原理如何?</P><P 0pt">答:当射频/中频(RF/IF)IC接收信号时,系接受自天线的信号(约800Hz~3GHz)经放大、滤波与合成处理后,将射频信号降频为基带,接着是基带信号处理;而RF/IF IC发射信号时,则是将20KHz以下的基带,进行升频处理,转换为射频频带内的信号再发射出去。<p></p></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">78.   </FONT>一般手机射频<FONT face="Times New Roman">/</FONT>中频模块由哪些部分组成?</P><P 0pt">答:一般手机射频/中频模块系由无线接收、信号合成与无线发射三个单元组成,其中无线接收单元系由射频头端、混波器、中频放大器与解调器所组成;信号合成部份包含分配器与锁相回路;无线发射单元则由功率放大器、AGC放大器与调变器组成。<p></p></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">79.   </FONT>手机基带处理器的组成和主要功能是什么?</P><P 0pt">答:常见手机基带处理器则负责数据处理与储存,主要组件为DSP、微控制器、内存(如SRAM、Flash)等单元,主要功能为基带编码/译码、声音编码及语音编码等。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">80.   </FONT>如何理解手机的射频、中频和基频?</P><P 0pt">答:手机内部基本构造依不同频率信号的处理可分成射频(RF)、中频(IF)及基频(BF)三大部分,射频负责接收及发射高频信号,基频则负责信号处理及储存等功能,中频则是射频与基频的中介桥梁,使信号能顺利由高频信号转成基频的信号。<p></p></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">81.   </FONT>手机最后的发射频率是在<FONT face="Times New Roman">890--915Mhz</FONT>,这是调频波还是调幅波?测使用<FONT face="Times New Roman">gmsk</FONT>调制的<FONT face="Times New Roman">gsm</FONT>手机的射频部分,为何在测试时使用固定的<FONT face="Times New Roman">902.4Mhz</FONT>的固定频率?</P><P 0pt">答:<FONT face="Times New Roman">GMSK</FONT>调制指高斯最小频移键控,是数字调制,某种程度上可以理解成是调频,但频率的改变以离散的(不连续的)方式进行,而调频纯粹是模拟调制,频率的改变是连续的。<FONT face="Times New Roman"> </FONT></P><P 0pt">从<FONT face="Times New Roman">890MHZ</FONT>到<FONT face="Times New Roman">915MHZ</FONT>共<FONT face="Times New Roman">25MHZ</FONT>频带宽度,信道间隔为<FONT face="Times New Roman">200KHZ</FONT>(即<FONT face="Times New Roman">0.2MHZ</FONT>),共有<FONT face="Times New Roman">125</FONT>个上行信道,测试时不可能<FONT face="Times New Roman">125</FONT>个信道都测,通常会选<FONT face="Times New Roman">3</FONT>个有代表性的频点(信道),两边两个,中间一个,<FONT face="Times New Roman">902.4MHZ</FONT>刚好是中间的信道。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">82.   </FONT>手机测试项目:射频载波功率、时间<FONT face="Times New Roman">/</FONT>功率包络、相位误差、接收报告电平的英文表达是什么?<FONT face="Times New Roman"> </FONT></P><P 0pt">答:射频载波功率:<FONT face="Times New Roman">RF Carrier Power</FONT>;时间<FONT face="Times New Roman">/</FONT>功率包络:<FONT face="Times New Roman">Time/Power Template</FONT>;相位误差:<FONT face="Times New Roman">Phase Error</FONT>;接收报告电平:<FONT face="Times New Roman">RSSI</FONT>。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">83.   </FONT>现在较流行的射频仿真软件有哪些?</P><P 0pt">答:一般来说生产射频器件的厂商都有这样的软件。如<FONT face="Times New Roman">EIC</FONT>的产品就有这样的软件,只要将设计电路的器件参数输入,即可。目前较流行的射频仿真软件有:<FONT face="Times New Roman">HP-ADS</FONT>、<FONT face="Times New Roman">ADS</FONT>、<FONT face="Times New Roman">microwave office</FONT>、<FONT face="Times New Roman">Ansoft</FONT>等。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt 0pt 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt"><FONT face="Times New Roman">84.   </FONT>手机主要有基带和射频组成,射频现在很多<FONT face="Times New Roman">IC</FONT>厂家都已经有单芯片产品。同时基带也有将<FONT face="Times New Roman">DSP</FONT>和<FONT face="Times New Roman">ARM</FONT>核集成在一块<FONT face="Times New Roman">IC</FONT>中。<FONT face="Times New Roman">TI</FONT>目前是否有单芯片的基带?<FONT face="Times New Roman"> </FONT></P><P 0pt">答:目前<FONT face="Times New Roman">TI</FONT>的数字基带芯片中已经把<FONT face="Times New Roman">ARM7</FONT>和<FONT face="Times New Roman">DSP</FONT>集成在一起了。</P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P><P 0pt"><p><FONT face="Times New Roman"> </FONT></p></P>
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发表于 2006-5-9 18:27:00 | 显示全部楼层
以前就有了呀!!
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发表于 2006-9-19 18:11:00 | 显示全部楼层
不错!
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发表于 2014-4-14 00:48:19 | 显示全部楼层
谢谢分享!
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发表于 2014-5-20 16:24:13 | 显示全部楼层
不错! 谢谢分享!
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发表于 2014-5-25 21:37:15 | 显示全部楼层
zhe kankan
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发表于 2014-11-12 22:20:26 | 显示全部楼层
哥一大页是什么
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发表于 2016-8-25 15:38:02 | 显示全部楼层
可惜了好东西啊,没金币
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