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1、Texas Instruments High Speed Products Solutions for Wireless InfrastructureTechnical Training3Q 2011Abstract An overview of TIs signal chain devices targeting cellular wireless infrastructure (3G/4G/MC- GSM) applications. Solutions for radio architectures including direct conversion (quadrature) rec
2、eive and transmit solutions, as well as super-heterodyne architectures will be presented. Example radio diagrams are given using high speed ADC/DACs, RF, clocking, amplifier and digital radio blocks.Direct Conversion Receiver Antenna 2ch ADCADC ADCWireless Communications Common Rx/Tx TypesDirect Con
3、version TransmitterIQ DEMODTRF3711DDC/DUC/FPGA2ch DACDAC DACIQ MODTRF3720IF (Heterodyne) Receiver AntennaAMPTHS77001ch ADCADCBPFBPF1ch DACDACIF (Heterodyne) TransmitterGC6016 (DDC/DUC) GC5330 (with DPD)BPFAMPTHS77001ch ADCADCDigital Pre-Distortion FeedbackCLOCKCDCE72010 This presentation will walk a
4、round the radio from Digital, to DAC, to RF Upconvert, to RF Downconvert, to ADC and back to Digital.Introduction to Transmit/Receive Basic Basestation Radio Architecture Digital Up-Conversion (DUC) DAC Analog Issues RF Up-Convert RF Down-Convert ADC Sampling Issues Digital Down Conversion (DDC) Clo
5、cking IssuesObjective: Get Between Baseband and RFBaseband to RF transmit and receive chain simply shifts the baseband up to the higher RF frequencies and vice versa:Typical Basestation Radios shift the baseband in two steps, Digital Up and Down convert between baseband (BB) and an intermediate freq
6、uency (IF), and analog up and down convert between IF and RF:0RFBWRF= BWBBTransmit: BB upconvert to RF0RFBWRF= BWBBReceive: RF downconvert to BBTransmit:Receive:0RFDigital Up Convert to IFIFAnalog Up Convert to RF0RFDigital Down Convert to BBIFAnalog Down Convert to IFSingle-Carrier vs. Multi-Carrie
7、r TransmittersMultiple Carriers can be up-converted individually using multiple Single carrier radios: (low complexity, but high cost) Or Multiple Carriers can be “stacked” at baseband and up-converted as a group using a Wideband direct up-convert radio: (low cost, single RF stage, but difficult to
8、meet specs) Or Multiple Carriers can be “stacked” at IF and up-converted as a group using a Wideband IF up-convert radio: (medium cost, best performance)0RF1Carrier 10RF1Carrier 2RF20RF1Carrier 3RF2RF30RF1RF2RF3BB1BB2BB3Carrier groupRF1RF2RF30IF1IF2IF30IF1IF2IF3Carrier groupSingle-Carrier vs. Multi-
9、Carrier ReceiversMultiple Carriers can be down-converted individually using multiple Single carrier radios: (low complexity, but high cost) Or Multiple Carriers can be down-converted as a group using a Wideband direct down-convert radio:(simple, but too difficult to meet specs)Or Multiple Carriers c
10、an be down-converted to an IF and individually down-converted from there using a Wideband IF down-convert radio:(medium cost, best performance)0RF1Carrier 10RF1Carrier 2RF20RF1Carrier 3RF2RF30RF1RF2RF3BB1BB2BB3Carrier group0IF1IF2IF3RF1RF2RF30IF1IF2IF3Carrier group Receive diversity uses two basesta
11、tion antennas to prevent multi- path fading of the signals coming from a mobile phone to a basestation.phoneObject (car, wall, Mountain)Main antenna The reflected signal may be 180 degrees out of phase (a half wavelength path difference, or 3 inches at 2GHz) which will “fade” the main signal. A seco
12、nd antenna is used to provide “spatial diversity”. If the diversity antenna is placed correctly, one can guarantee that both antennas cannot receive the two paths 180 degrees out of phase. The basestation combines the main and diversity versions of the signal to get the best reception. Reflected pat
13、hDirect pathDiversity antennaWhy Receive Diversity? The same multi-path fading can occur when the basestation transmits a signal to the mobile phone. Since the basestation can transmit stronger signals, transmit diversity is not always used. Spatial diversity can not be used because it requires two
14、antennas and two receivers in the mobile phone. Instead, the basestation sends two differently encoded versions of the same data to the mobile, one from each antenna. The mobile phones antenna receives both versions of the data. If one is faded due to multi-path, then the other should be good. This
15、is called “code” diversity.Why Transmit Diversity?Requirements are a function of Diversity Two DDCs and two DUCs are required for each carrier in the radio One per carrier for the Main antenna. One per carrier for the diversity antenna. Not all systems require diversity for transmit (main only for t
16、ransmit). Two ADCs are needed per radio. Multiple DACs are needed per radio. One for radios without transmit diversity (2 for direct IQ Modulation). Two with transmit diversity (4 for direct IQ Modulation).The Transmitter DUC DAC RF ModulatorDigital Up-Conversion The PFIR shapes the spectrum of the input data and interpolates by a factor of L. The PFIR is programmable so that the spectral shape can be
