Request PDF on ResearchGate | Binary Offset Carrier Modulations for Radio Navigation | Current signaling for GPS employs phase shift keying (PSK). Abstract: Current signaling for GPS employs phase shift keying (PSK) modulation using conventional rectangular (non – return to zero) spreading symbols. The first model defines the BOC modulation as the result of . The Binary Offset Carrier Modulation can be expressed as a BCS sequence . [J.W. Betz, a] J.W. Betz, Binary Offset Carrier Modulations for Radionavigation.

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Binary offset carrier modulation

Considered in this sense, the BOC modulation generalizes a Manchester modulation to more than one zero crossing per spreading symbol i. The channel thus has the transfer function H f 1 ei 2 fd 23 Fig.

But bandwidth limitations preclude further improvements that might be obtained using PSK-R modulations with faster keying rates. Journal of Communications Technology and Electronics.

Second, it has introduced binary offset carrier BOC modulations, and shown that they offer significant benefits over comparable phase shift key modulations using rectangular carreir PSK-R.

The maxima of the power spectral densities for these two modulations are almost identical. The subcarrier frequency is actually 1. In addition, it is easy to extract the separate upper and lower subcarriers from the received signal and to track these as well. Since the emphasis in this paper radiohavigation on modulation design, long spreading codes are assumed, leading to smooth spectra without spectral lines.

BOC 5,2 places spectral peaks in spectral nulls of radionavgiation heritage civilian signals and the new military signal [4]. Definition of Binary Offset Carrier Modulation The complex envelope of an offset carrier signal is given by [2] note that all the analysis here uses analytic signal representations and lowpass-equivalent representations of linear time-invariant systems: In many respects, including maximum power spectral density, out-of-band loss, and spectral separation with itself, the two modulations are very similar.

In contrast, n 5 for a BOC 5,2 modulation, and its spectrum has three sidelobes between the two mainlobes, radionavigatoin n 10 for a BOC 5,1 modulation, and its spectrum has eight sidelobes between the two radionavigatiion.

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Figure 17 compares code-tracking accuracy for the set of modulations considered in this paper, using a 24 MHz front-end bandwidth, a code-tracking loop with equivalent rectangular bandwidth of 0. Sideband processing is straightforward to implement and has been demonstrated in hardware [11].

However, studies and hardware testing have demonstrated that the BOC modulation designs described in this section provide robust and practical performance. This representation shows that, when the spreading symbol is rectangular, offset carrier signals are conventional PSK-R signals modulating a periodic signal. For example, when the subcarrier frequency is much greater perhaps by more than a factor of 10 than the spreading code rate, the correlation function has many closely spaced in amplitude and delay peaks that can introduce carriee effects in code tracking.

BOC 10,5 reduces the worst-case bias error from 5. The columns for BOC 5,2 modulation and 1.

While BOC modulations were developed to provide spectral isolation from heritage signals modulating the same carrier frequency, it was quickly determined that they offer performance advantages as well.

The locations of spectral peaks and their maximum power spectral densities are selfexplanatory.

The error becomes very large for early — late spacing near ns, corresponding to the slope reversal in the S-curves observed in Figure Figure 13 shows results for BOC 10,5 modulation, computed using equation When the RMS bandwidth is computed over morulations bandwidth, two separate effects occur: The discriminator gain is defined as the 0: The BOC 8,4 modulation offers performance comparable to or better than that of a The smaller is the out-of-band power loss outside 24 MHz, the greater is the in-band power available to a receiver.

Views Read Edit View history. By moving signal power away from the band center, they offer the potential for better code-tracking accuracy and multipath rejection. The number of negative and positive peaks in the magnitude autocorrelation function is 2n 1, and the peaks are separated in delay by Ts.

Binary offset carrier modulation [1] [2] BOC modulation was developed by John Betz, PhD, in order to allow interoperability of satellite navigation systems. All of the baseband signals in Figure 1 are binary-valued, and thus can be implemented using binary logic. The spectral separation coefficient, defined in equation 16indicates the extent to which signals interfere with each other. While the discriminator gain becomes smaller for early — late spacings modulatiions greater than 60 ns, the effect of early — late spacing on code-tracking accuracy cannot be inferred from this behavior.

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Viewed another way, obtaining the same codetracking error with As in conventional PSK, the zero crossings of each mainlobe are spaced by binnary the code rate, while the zero crossings of each sidelobe are spaced at the code rate. More significant, BOC 10,5 offers 17 dB better spectral separation from civilian signals that use 1.

Betz_Binary Offset Carrier Modulations for Radio Navigation_百度文库

In addition, a smaller spectral separation coefficient indicates the ability of a modulation to provide enough processing gain against multipleaccess interference from similar signals so that it can support higher data rates. Further, more advanced modulations can better radlonavigation existing frequency allocations with each other and with heritage signals, thus preserving spectrum. Many of the advantages of BOC modulations are clear in the examples presented in this paper.

The normalized autocorrelation functions are portrayed in Figure 6, showing the narrower peak and multimode structure of the BOC correlation function.

BOC 5,2 has substantially less multipath-induced bias at most multipath delays. A very small antenna and simple RF electronics having only enough bandwidth to pass one sideband, combined with the reduced sampling rate and processing throughput requirements associated with the bandwidth of one sideband, would help minimize the cost, size, and power consumption of the receiver.

Yet the BOC 8,4 modulation provides slightly 0. Some measures, such as those of spectral occupancy, have been used extensively for many offdet in assessment of modulations for radionavigation.

While BOC 8,4 fits comfortably within a bandwidth of less than 24 MHz, its superior code-tracking accuracy and multipath resistance would be desirable for a high-performance civilian signal. Fro other sources of error diminish, contributions from noise and multipath start to dominate.

Figure 15 shows results for BOC 5,2 modulation, computed using equation