Microwave Engineering Europe - October 2007 - (Page 38)

38 DIRECT SYNTHESIS during the manufacturing process. The oscilloscope’s high accuracy and traceability makes possible its use in the waveform generator calibration procedures. Experiment observations Basic experimental results are composed by EVM data sets gathered for different bit rates and modulations schemes (QPSK and DCM). Table 3: Measurement results for Direct RF Synthesis. Signals were generated using AWG7102 in interleaving mode. All measurements conducted for Band Group 1 : RF center frequency of 3960 MHz. Sampling rate in the AWG set at 20 GHz. *TFCs were chosen randomly. All data suggest that direct RF synthesis would yield a very good EVM of around 30 dB better than the -19.5 dB EVM speciﬁed in the standard as shown in Table 3. You also have the ability to frequency hop without the necessity of an external frequency hopper due to high sampling rate and bandwidth of the AWG. The set up is straight forward, easy to control and conﬁgure. A very good ﬂatness is achieved without any predistortion in Band Group 1 using the Tektronix AWG 7102. Refer to Figure 2 which provides the spectrum of the signal captured on the Tektronix oscilloscope. RF/IF/IQ waveform creation and editing tools The next sections will discuss the use of RF/ IF/IQ Waveform Creation and Editing Tools, speciﬁcally Tektronix RFXpress software, to generate UWB-WiMedia Signals. PPDU structure Figure 3 shows the format of PLCP Protocol Data Unit (PPDU), which is composed of three major components: • PLCP Preamble (Physical Layer Convergence Protocol) • PLCP Header • PSDU - PHY Service Data Unit They are transmitted in the same order as stated above. PLCP preamble The PLCP preamble is the ﬁrst component of the PPDU and can be further decomposed into a packet/frame synchronization sequence and a channel estimation sequence. The goal of the PLCP preamble is to aid the receiver in timing synchronization, carrier-offset recovery and channel estimation. The Preamble is deﬁned to be a real baseband signal. For the lowest data rate modes (53.3 Mb/s and 80 Mb/s), the data type of the preamble is the same as the payload, that is, both signals are real. For the higher data rates, the preamble is inserted into the real portion of the complex base band signal. Two preambles are deﬁned: a standard PLCP preamble and a burst PLCP preamble. The burst preamble is only used in the streaming mode when a burst of packets is transmitted, separated by a minimum interframe separation time (pMIFS). RFXpress allows the changing of all of these for testing the receiver. For example, in custom mode one can edit the Base timedomain sequence and test the receiver for any corrupted preamble sequence. Figure 2: Spectrum of Band Group 1 (Direct RF synthesis). Figure 3: PPDU structure. Figure 4: Frame related parameters. Microwave Engineering Europe ● October 2007 ● www.mwee.com 034-036-038-040-042-044_MWEE.ind38 38 20/09/07 17:34:44 http://www.mwee.com

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Microwave Engineering Europe - October 2007 Contents Comment News CMOS RF: Si-On-Sapphire Goes Mainstream Cover Feature: New Data Protection Concept for UHF RFID Tags CMOS RF: RF Design Team Touts CMOS Spin for 3G PAs Wireless HID – Are You Following the Standard to Another “Average” Product Development? Phase Optimisation of the RF Front-End Direct Synthesis of UWB-WiMedia Signal Generation 4G Chips to Target 700 MHz Applications Femtocells Mobilize to Fight Wi-Fi in the Home Products Product Feature: AXIEM Pioneers the Future of EM Technology Calendar

Microwave Engineering Europe - October 2007

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