Datenblatt-Suchmaschine für elektronische Bauteile |
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LMS7002M Datenblatt(PDF) 7 Page - List of Unclassifed Manufacturers |
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LMS7002M Datenblatt(HTML) 7 Page - List of Unclassifed Manufacturers |
7 / 27 page LMS7002M 7 LMS7002M – FPRF MIMO Transceiver IC Decimation Decimation IQ Phase Corr IQ Gain Corr RX DC Corr IQ Phase Corr IQ Gain Corr RX DC Corr CMIX RXNCO G. P. FIR 1 G. P. FIR 1 G. P. FIR 2 G. P. FIR 2 RSSI RXI RXQ RYQ RYI G. P. FIR 3 G. P. FIR 3 Figure 11: Structure of the RXTSP CMIX TXNCO Interpolation Interpolation G. P. FIR 1 G. P. FIR 2 G. P. FIR 1 G. P. FIR 2 TXQ TXI G. P. FIR 3 G. P. FIR 3 IQ Phase Corr IQ Gain Corr TX DC Corr IQ Phase Corr IQ Gain Corr TX DC Corr TYI TYQ INVSINC INVSINC Figure 12: Structure of the TXTSP The two Numerically Controlled Oscillators (NCO) and digital complex mixer (CMIX) in the TXTSP and RXTSP paths enable the LMS7002M to run in low digital IF. Inverse sinc filters (INVSINC) within the TXTSP chain compensate for sinx/x amplitude roll off imposed by the DACs themselves. The Tx DC Corr block is used to cancel residual DC offset of TXLPF. It is also used to cancel TX LO leakage feed-through as mentioned earlier. There are three sources of the DC component at the RX output. These are the residual DC offset of the RXPGA and RXLPF, RX LO leakage feed-through and second order distortion (IP2). The Rx DC Corr blocks compensate for all of these sources of offset. The block is implemented as a real time tracking loop so any change of the RX DC due to either the signal level change, or due to RX gain change as well as any temperature effect will be tracked and cancelled automatically. The IQ Gain Corr and IQ Phase Corr blocks correct IQ imbalance in both TXTSP and RXTSP in order to minimize the level of unwanted side band (image) component. The last stage in the RXTSP path is a digital implementation of an Adaptive Gain Control (AGC) loop. Assuming that the BB modem does not require 12-bit full scale ADC outputs, the digital AGC block can provide a certain level of automatic gain control before the BB involves RF and IF gain stages. More detailed descriptions of all the various TSP blocks are given in the following sections. IQ Gain Correction This block implements the following equation: Q G Qin Qout I G Iin Iout _ _ . Corresponding hardware is given in Figure 13. G_I and G_Q are programmable correction factors which are altered by the BB modem to minimize any unwanted side band component. The BB modem can combine IQ gain correction and digital gain control using the same module by calculating G_I and G_Q in the following way: digi G corr Q G Q G digi G corr I G I G _ * _ _ _ _ * _ _ _ , where G_I_corr and G_Q_corr are IQ gain correction factors and G_digi is the desired digital gain. G_I G_Q Qout Iout Iin Qin Figure 13: IQ gain correction implantation IQ Phase Correction IQ phase correction is in fact equivalent to vector rotation. If the quadrature phase error is then the I and Q vectors are both rotated by /2 but in opposite directions hence IQ outputs of the corrector circuit are 90o phase shifted. IQ phase correction equations are given below while Figure 14 shows the hardware implementation. 2 tan 2 tan Iin Qin Qout Qin Iin Iout . The value of tan( /2) should be stored in the configuration register as a programmable correction parameter. The BB modem should adjust this value to minimize the unwanted side band component. The BB modem can also use the following approximation formula: 2 2 tan when is small, which is usually the case. The IQ phase corrector of the LMS7002M is designed to correct an IQ phase error up to +/- 20o. |
Ähnliche Teilenummer - LMS7002M |
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Ähnliche Beschreibung - LMS7002M |
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