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ssrs barcode image Fourteen in Software
Fourteen Decode QR Code JIS X 0510 In None Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications. QR Code 2d Barcode Generation In None Using Barcode generator for Software Control to generate, create QR image in Software applications. [N is given by Eq. (14.38)]. Two numbers are relatively prime when their greatest common divisor is 1. A general formula for finding (N ) is (see Ore, 1988) (N) Na p1 p1 1 pr 1 b c a p b Recognizing QR Code JIS X 0510 In None Using Barcode reader for Software Control to read, scan read, scan image in Software applications. QR Code ISO/IEC18004 Generation In C# Using Barcode maker for .NET Control to generate, create Quick Response Code image in VS .NET applications. (14.43) Make QR Code ISO/IEC18004 In .NET Using Barcode drawer for ASP.NET Control to generate, create Denso QR Bar Code image in ASP.NET applications. QR Printer In .NET Using Barcode printer for Visual Studio .NET Control to generate, create QR Code JIS X 0510 image in .NET framework applications. where p1 . . . pr are the prime factors of N. For example, for n 8, N 28 1 255. The prime factors of 255 are 3, 5, and 17, and hence (255) 2 4 16 255a b a b a b 3 5 17 128 The total number of maximal sequences that can be generated by an eightstage code generator is therefore Smax 128 8 16 Creating Quick Response Code In VB.NET Using Barcode encoder for .NET Control to generate, create QR Code 2d barcode image in Visual Studio .NET applications. Print UPCA Supplement 2 In None Using Barcode maker for Software Control to generate, create UPCA Supplement 5 image in Software applications. As a somewhat simpler example, consider the case when n 3. In this instance, N 7. There is only one prime factor, 7 itself, and therefore (7) and Smax (7) 3 2 7# 6 7 6 Encode Bar Code In None Using Barcode generation for Software Control to generate, create barcode image in Software applications. Code 39 Encoder In None Using Barcode creator for Software Control to generate, create Code 3 of 9 image in Software applications. In this case there are only two distinct maximal sequences. One of the most important properties of c(t) is its autocorrelation function. The autocorrelation function is a measure of how well a timeshifted version of the waveform compares with the unshifted version. Figure 14.35a shows how the comparison may be made. The c(t) waveform is multiplied with a shifted version of itself, c(t t), and the output is averaged (shown by the integrator). The average, of course, is independent of time t (the integrator integrates out the timet dependence), but it will depend on the time lead or lag introduced by t. When the waveforms are coincident, t 0, and the average output is a maximum, which for convenience will be normalized to 1. Any shift in time, advance or delay, away from the t 0 position will result in a decrease in output voltage. A property of msequence code waveforms is that the autocorrelation Encoding UCC128 In None Using Barcode printer for Software Control to generate, create EAN 128 image in Software applications. Create Code 128 Code Set A In None Using Barcode encoder for Software Control to generate, create Code 128 Code Set C image in Software applications. Satellite Access
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Encode Code 39 Extended In None Using Barcode creation for Excel Control to generate, create Code39 image in Office Excel applications. Recognizing Barcode In .NET Framework Using Barcode recognizer for VS .NET Control to read, scan read, scan image in .NET applications. Tch (b) Printing UCC  12 In Java Using Barcode creation for BIRT Control to generate, create GS1  12 image in BIRT reports applications. EAN 13 Recognizer In Visual Studio .NET Using Barcode reader for .NET framework Control to read, scan read, scan image in .NET applications. (a) Generating the autocorrelation function; (b) the autocorrelation
waveform.
function decreases linearly from the maximum value (unity in this case) to a negative level 1/N, as shown in Fig. 14.35b. The very pronounced peak in the autocorrelation function provides the chief means for acquiring acquisition and tracking so that the locally generated msequence code can be synchronized with the transmitted version. 14.10.3 Acquisition and tracking
One form of acquisition circuit that makes use of the autocorrelation function is shown in Fig. 14.36. The output from the first multiplier is e(t) c(t c(t t)c(t)p(t) cos wDt t)c(t) cos[wDt (t)] (14.44) Here, the information modulation, which is BPSK, is shown as (t) so that the effect of the following bandpass filter (BPF) on the amplitude can be more clearly seen. The BPF has a passband centered on wD, wide with respect to the information modulation but narrow with respect to the code signal. It performs the amplitudeaveraging function on the X c(t)p(t)cos
To coherent detector
c(t ) VT
VAVG>VT Enable tracking Threshold detector VAVG shift VAVG<VT PN GEN Autocorrelator
Envelope detector
Acquisition of a carrier in a CDMA system.
Fourteen
code signal product (see Maral and Bousquet, 1998). The averaging process can be illustrated as follows. Consider the product of two cosine terms and its expansion: 1 5cos[ t 2 1 [cos(2 t 2 cos t cos( t
( t ) )] cos ] cos[ t
)]6 (14.45) The BPF will reject the highfrequency component, leaving only the average component 0.5 cos( ). This signal may be considered analogous to the c(t)c(t t) term in Eq. (14.44). The envelope detector following the BPF produces an output proportional to the envelope of the signal, that is, to the average value of c(t)c(t t). This is a direct measure of the autocorrelation function. When it is less than the predetermined threshold VT required for synchronism, the time shift t incremented. Once the threshold has been reached or exceeded, the system switches from acquisition mode to tracking mode. One form of tracking circuit, the delay lock loop, is shown in Fig. 14.37. Here, two correlators are used, but the local signal to one is advanced by half a chip period relative to the desired code waveform, and the other is delayed by the same amount. The outputs from the correlators are subtracted, and this difference signal provides the control voltage for the VCO that drives the shift register clock. With the control voltage at the zero crossover point, the locally generated code signal is in phase with the received code signal. Any tendency to drift out of phase changes the VCO in such a way as to bring the control voltage back to the zero crossover point, thus maintaining synchronism. The acquisition and tracking circuits also will attempt to correlate the stored version of c(t) at the receiver with all the other waveforms being received. Such correlations are termed crosscorrelations. It is essential that the crosscorrelation function does not show a similar peak as the autocorrelation, and this requires careful selection of the spreading functions used in the overall system (see, for example, Dixon, 1984).

