CN1142291A - 频带分离信号数字化器和方法 - Google Patents

频带分离信号数字化器和方法 Download PDF

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CN1142291A
CN1142291A CN95191828A CN95191828A CN1142291A CN 1142291 A CN1142291 A CN 1142291A CN 95191828 A CN95191828 A CN 95191828A CN 95191828 A CN95191828 A CN 95191828A CN 1142291 A CN1142291 A CN 1142291A
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保罗·菲尔丁·史密斯
丹尼·托马·平克利
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Motorola Solutions Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/0003—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain
    • H04B1/0007—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain wherein the AD/DA conversion occurs at radiofrequency or intermediate frequency stage
    • H04B1/0017—Digital filtering
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
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    • H03M1/121—Interleaved, i.e. using multiple converters or converter parts for one channel
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/0003—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/0003—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain
    • H04B1/0007—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain wherein the AD/DA conversion occurs at radiofrequency or intermediate frequency stage
    • H04B1/001—Channel filtering, i.e. selecting a frequency channel within the SDR system
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H04B1/26—Circuits for superheterodyne receivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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    • H—ELECTRICITY
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    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/14—Channel dividing arrangements, i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only

Abstract

一个频带分离信号数字化器(10)包括第一混频器(18)，用于变换多倍取样频率周围的频带分离信号(200)。这样变换的频带分离信号然后传送到模/数变换器(26)。分析数字化的信号，恢复频带分离信号的原始部分和混叠为单个奈奎斯特频带的信号的第二部分。

Description

频带分离信号数字化器和方法
本发明涉及多信道数字收发信机，具体涉及有效地数字化频带分离信号的频带分离信号数字化器和方法。
使用数字技术实现无线通信系统有很多优点。最明显的是，增强系统容量，减少噪声和减少硬件及有关的功耗。业已提出了几个数字无线电通信系统，例如，共同受让的美国专利申请，名称为“多信道数字收发信机和方法”(与本申请在相同日期提交，本申请人是共同发明人)中已表示和叙述了实现数字技术的无线电通信系统的几个优选实施例。
数字无线电通信系统的基础是要求对接收的模拟无线电信号数字化。公知的奈奎斯特准则假定这种数字化是使用取样率大于两倍的模拟信号带宽的模/数变换器(ADC)以最小误差实现的。在美国专利5251218中，公开了用于数字化模拟射频信号的现有技术的方法。但是，可以理解，无线电信号占用大的带宽，要求ADC能够以非常高的取样速率工作。这种装置在它们可利用的程度上是昂贵的而且经常性能降低，即在高取样速率工作时，具有显著的失真和增加功耗。
针对数字化的要求而言，分配给无线电通信系统的频谱通常很宽。但是，在一些无线电通信系统中，虽然需要的信号占用大的带度，但不是所有的带宽都是由感兴趣的信号占用。例如在蜂窝无线电话通信系统中，通信带宽不是邻接的。在无线电频谱开始分配给蜂窝无线电话通信时，两个邻接的10MHz频谱段分别分配用于“A波段”操作者和“B波段”操作者。但是随着增强蜂窝无线通信系统容量的需求聚增，需要额外的带宽。遗憾的是，与原始分配频段相邻的足够大的带宽段不能使用。为此，分配另外的2.5MHz带宽段。由此得到的A波段在图2A中表示为以由B波段占用的一个10MHz频段分隔开的一个11MHz频段和一个1.5MHz频段。鉴此，虽然蜂窝A波段和B波段在频谱上各具有12.5MHz的带宽，但是整个A波段覆盖了在两个连续部分的22.5MHz的带宽。
为了数字化A波段，例如，根据奈奎期特准则，需要一个ADC能够至少以45MHz或每秒45百万个样值(Ms/s)，而更可靠地以56Ms/s工作。分离该信号成为较小的段允许以较低的取样速率使用多个ADC。使用多个ADC具有需要更多的硬件的缺点。加之，时钟频率及其较高次谐波不可避免地落入被数字化的信号的频带中。再一个缺点是滤波、内插、补偿频带重叠和对得到的多个数字信号求和需要大量的数字数据处理。
据此，现在需要一种用于数字化频带分离信号的设备和方法，它不要求高的取样速率，而且不显著地增加通信系统所要求的硬件数量。本发明提供了这种设备和方法，而且本领域普通技术人员很容易从下面的详细叙述和附图知道本发明的许多优点和特性。
图1示出根据本发明的优选实施例的频带分离数字化器的方框图；
图2A示出频带分离信号的频谱；
图2B示出根据本发明的优选实施例在传输之后图2A所示的频带分离信号的频谱；
图2C示出根据本发明的优选实施例在变换为数字信号之后图2B所示的频带分离信号的频谱；和
图3示出根据本发明的优选实施例说明数字化频带分离信号的方法的流程图。
本发明以降低的取样频率和降低的硬件要求实现了对于频带分离模拟信号的数字化。本发明提供对于以基准频率为中心的整个分离频率带宽进行混合，这允许以降低的取样频率数字化。基准频率选择得可使分离频率带宽的各段占用相邻的混叠(aliasing)频段。以降低的取样频率进行的数字化产生一种数字信号，它具有在取样频率的单个奈奎期特频段中表示的整个频带分离信号。
参见图1，图中示出了组成本发明数字化器的一个数字无线电接收机10。频带分离模拟信号由天线12接收，并且下混频和经过滤波器14放大器16进行信号处理，如本领域所公知的。然后频带分离信号传送到混频器18，与本机振荡器20来的的信号进行频率变换。
参见图2A-2C，图中示出频带分离信号200。信号200典型地是蜂窝A波段的信号，但是，可以理解，本发明可应用于数字化任何类型的频带分离的模拟信号。在混频器18中信号200与基准频率混频的结果是图2B的信号200’。如可看到的，在混频之后，频带分离信号被变换了，使得信号200’的分离段位于以fs/2表示的基准频率附近。可以理解，根据频带分离的信号可选择适当的本机振荡频率用于高端或低端插入，以变换基准信号周围的信号。
已混频的频带分离信号通过滤波器22和放大器24作进一步处理。然后变换的频带分离信号传送到模/数变换器(ADC)26。模/数变换器26以公知的方法式以取样率fs数字化频带分离模拟信号，产生数字信号27。数字信号27在图2C中以200”表示。如从图2C可看到的，数字化信号200’导致信号200’的分离频带段(以虚线表示)与包含在取样频率fs的奈奎斯特频段中的混叠段相混淆。
在本发明的优选实施例中，取样频率fs选择约为2.5倍的频带分离信号的较宽段的带宽。基准频率选择约为其取样频率的一半或多倍。可以理解，使用取样速率它小于频带分离信号的两倍的总频谱带宽，(例如，如图2A所示的)数字化整个频带分离信号。再参看图2C，示出用于蜂窝A波段的选择取样频率的具体例子。从所示的频谱图可进行两个计算，第一：
X＋1.5＋2Y＝10            (a)和第二：
Z＋11＋X＋1.5＋Y＝fs/2   (b)由此可确定：
fs＝33.5＋X＋2Z          (c)式中X、Y和z为图2C中所示的，而11MHz和1.5MHz分别为被数字化段的带宽。这个关系是正确的而不考虑混叠频带。从上面可看出，与56Ms/S相比fs可接近33.5Ms/S，这是数字化蜂窝A波段所要求的。在实际应用中，fs取决于滤波，即X段必须宽得足以允许抗混叠滤波器通过11MHz波段，但衰减1.5MHz混叠。Z段必须足够大，在混频之后，由取样产生的影象可被滤除掉。实际上，fs实际上可接近35Ms/S。
然后数字信号200”传送到信道处理器28。信道处理器操作信号200”以恢复整个频带分离信号的数字表示。这种信道处理器的讨论可在名称为“多信道数字收发信机和方法”的前述美国专利申请中找到。应该注意由于混叠而使该信号的数字表示包含频带分离信号的位移段，但这是技术人员的常识，以便从这些位移段恰当地重构频带分离信号。
参见图3，图中示出根据本发明的优选实施例数字化频带分离信号的方法步骤300-308。在步骤302，收到频带分离信号，并且在步骤304进行混频，使得变换的频带分离信号段位于基准频率周围。然后在306数字化该混频的信号，产生包括频带分离信号的混叠的数字信号。混频的信号以小于频带分离信号的两倍的总带宽被数字化。然后，步骤308，从信道处理器卡中的数字信号中恢复频带分离信号。
正如本领域普通技术人员从前面讨论中可知道的，本发明提供一个数字化器和方法，它降低了用于数字化频带分离信号的取样频率和/或硬件要求。本发明的许多特点、优点和公正的范围很容易从前面的讨论和所附的权利要求书中了解。
权利要求书
按照条约第19条的修改
1.一种频率分离信号数字化器，其特征在于，包括：
第一频率变换器，被连接用于接收模拟频带分离信号，该模拟频带分离信号包括具有第一带宽的第一段和具有第二带宽的第二段，该模拟频带分离信号具有总带宽大于第一与第二带宽之和，该频率变换器从接收的信号产生频率交换的信号，该频率变换的信号具有与模拟频带分离信号的总带宽基本上相同的总带宽；
一个模/数变换器，响应该频率变换器，该模/数变换器通过以小于频带分离信号的两倍总带宽的取样速率取样频率变换的信号，来数字化频率变换的信号以产生数字信号，该数字信号包含数字化型的第一和第二段和混叠型的第一和第二段。
2.根据权利要求1的频率分离信号数字化器，其特征在于，包括一个处理器，从该数字信号恢复模拟频带分离信号的数字表示。
3.根据权利要求1的频率分离信号数字化器，其特征在于，第一和第二段和混叠型的第一和第二段的至少一段在频谱上都位于小于模拟频带分离信号的两倍总带宽的一个带宽内。
4.根据权利要求1的频率分离信号数字化器，其特征在于，还包括分析装置，响应模/数变换器，用于接收该数字信号和提取模拟频带分离信号的数字表示。
5.一种用于数字化模拟频带分离信号的方法，其特征在于，包括以下步骤：
接收模拟频带分离信号，该模拟频带分离信号具有第一带宽的第一段、第二带宽的第二段和总带宽大于第一和第二带宽之和的总带宽段；
频率变换该接收信号产生频率变换的信号、使得基准频率位于与该频率变换的信号中的频率变换型的第一段和第二段有关的频率之间；和
通过以小于模拟频带分离信号的两倍总带宽的取样速率取样该频率变换的信号来数字化该频率变换的信号以产生数字信号，该数字信号包含数字表示，的第一和第二段和混叠型的第一与第二段。
6.根据权利要求5数字化模拟频带分离信号的方法，其特征在于，该数字表示的第一与第二段和混叠型的第一和第二段的至少一个段位于小于频带分离信号的两倍总带宽的一个带宽内。
7.根据权利要求5数字化模拟频带分离信号的方法，其特征在于，该基准频率约为取样速率的一半。
8.根据权利要求7数字化模拟频带分离信号的方法，其特征在于，该混叠型的第一和第二段的至少一个段包含在基于取样速率的奈奎斯特段内。
9.根据权利要求5数字化模拟频带分离信号的方法，其特征在于，频率变换模拟频带分离信号的步骤包括变换整数倍奈奎斯特频率的摸拟频带分离信号周围的模拟频带分离信号。
10.一种数字接收机，其特征在于，包括：
一个接收机，检测模拟频率分离信号，该信号具有第一带宽的第一段和具有第二带宽的第二段，该模拟频率分离信号的总带宽大于该第一和第二带宽之和；以及
一个模/数变换器，响应该接收机，该模/数变换器通过以小于模拟频率分离信号的两倍总带宽的取样速率取样模拟频率分离信号，来数字化该模拟频率分离信号，以产生数字信号，该数字信号包含数字化型的第一和第二段及混叠型的第一和第二段。

Claims (10)

1.一种频率分离信号数字化器，其特征在于，包括：
第一频率交换器，被连接用于接收模拟频带分离信号，该模拟频带分离信号含有具有第一带宽的第一段和具有第二带宽的第二段，该模拟频带分离信号具有总带宽大于第一与第二带宽之和，该频率变换器从接收的信号产生频率交换的信号；
一个模/数变换器，响应该频率交换器，该模/数变换器通过以小于频带分离信号的两倍总带宽的取样速率取样频率，来数字化该频率变换的信号以产生数字信号，该数字信号含有数字化型的第一和第二段和混叠型的第一与第二段。
2.根据权利要求1的频率分离信号数字化器，其特征在于，包括一个处理器，从该数字信号恢复模拟频带分离信号的数字表示。
3.根据权利要求1的频率分离信号数字化器，其特征在于，第一和第二段和混叠型的第一和第二段的至少一段在频谱上都位于小于模拟频带分离信号的两倍总带宽的一个带宽内。
4.根据权利要求1的频率分离信号数字化器，其特征在于，还包括分析装置，响应模/数变换器，用于接收该数字信号和提取模拟频带分离信号的数字表示。
5.一种用于数字化模拟频带分离信号的方法，其特征在于，包括以下步骤：
接收模拟频带分离信号，该模拟频带分离信号具有第一带宽的第一段、第二带宽的第二段和总带宽大于第一和第二带宽之和的总带宽段；
频率变换该接收信号，产生频率变换的信号，使得基准频率位于与该频率变换的信号中的频率变换型的第一段和第二段有关的频率之间；和
通过以小于模拟频带分离信号的两倍总带宽的取样速率取样该频率变换的信号，来数字化该频率变换的信号，以产生数字信号，该数字信号包含数字表示的第一和第二段和混叠型的第一与第二段。
6.根据权利要求5数字化模拟频带分离信号的方法，其特征在于，该数字表示的第一与第二段和混叠型的第一和第二段的至少一个段位于小于频带分离信号的两倍总带宽的一个带宽内。
7.根据权利要求5数字化模拟频带分离信号的方法，其特征在于，该基准频率约为取样速率的一半。
8.根据权利要求7数字化模拟频带分离信号的方法，其特征在于，该混叠型的第一和第二段的至少一个段包含在基于取样速率的奈奎斯特段内。
9.根据权利要求5数字化模拟频带分离信号的方法，其特征在于，频率变换模拟频带分离信号的步骤包括变换整数倍奈奎斯特频率的摸拟频带分离信号周围的模拟频带分离信号。
10.一种数字接收机，其特征在于，包括：
一个接收机，检测模拟频率分离信号，该信号具有第一带宽的第一段和具有第二带宽的第二段，该模拟频率分离信号的总带宽大于该第一和第二带宽之和；以及
一个模/数变换器，响应该接收机，该模/数变换器通过以小于模拟频率分离信号的两倍总带宽的取样速率取样模拟频率分离信号，来数字化该模拟频率分离信号，以产生数字信号，该数字信号包含数字化型的第一和第二段及混叠型的第一和第二段。
CN95191828A 1994-12-29 1995-11-22 频带分离信号数字化器和方法 Expired - Fee Related CN1057413C (zh)

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