BINARY OFFSET CARRIER MODULATIONS FOR RADIONAVIGATION PDF

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 – Wikipedia

But bandwidth limitations preclude further improvements that might be obtained using PSK-R modulations with faster keying rates. The peaks are separated by While the signals are designed to occupy the 24 MHz allocation, the 30 MHz bandlimiting approximates that which occurs at GPS satellites.

Journal of Communications Technology and Electronics. For example, n 4 for both BOC 10,5 and BOC 8,4 modulations, and their spectra have two sidelobes between the two mainlobes. Retrieved from ” https: If desired, filtering can be used to select only the desired sideband and prevent aliasing at lower sampling rates.

The third section introduces some example BOC modulations of particular interest, defines measures for evaluating characteristics of modulations for radionavigation, and evaluates these measures for the example BOC modulations. While BOC modulations were developed to provide spectral isolation from heritage signals modulating the same carrier frequency, it radionavigatin quickly determined that they offer performance advantages as well.

Vinary has been focused primarily on the design of the spreading code and selection of the keying rates. Figure 7 portrays the spectra of BOC 8,4 and The effect of specular multipath environment on bias errors in code tracking is then examined.

For an ideal BOC modulation with infinite bandwidth, the autocorrelation function consists of a set of connected line segments with in general multiple zero crossings and multiple lobes. When the RMS bandwidth is computed over finite bandwidth, two separate effects occur: To understand why this phenomenon occurs, note that two different and counteracting effects occur with early — late processing of bandlimited signals as the early — late spacing becomes small while the bandwidth of the codetracking loop is held constant.

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It defines the modulations, outlines the approach for generating them, and presents expressions for their second-order statistics.

Binary offset carrier modulation

The maximum of the power spectral density for the BOC 5,2 modulation is more than 6 dB lower than that for 1. While the discriminator gain becomes smaller for early — late spacing greater than 30 ns, the effect of early — late spacing on code-tracking accuracy cannot be inferred from this behavior, as seen later in this section. Yet another way to verify this asymptotic behavior is to recognize that, with vanishing early — late spacing, early — late processing approaches an ideal differentiator, which is the maximum-likelihood estimator of time of arrival in white Gaussian noise.

To distinguish between the two, equation 13 defines the RMS bandwidth using the normalized bandlimited power spectral density, and the loss of power is accounted for separately through equation For example, while Figure 10 shows that rradionavigation gain increases as early — late spacing decreases from 40 ns, Figure 13 shows that there is no further reduction in code-tracking error.

Another degradation is due to the change in spectral shape radjonavigation the resulting reduction in RMS bandwidth. From Wikipedia, the free encyclopedia. Whenever n carier even, qnTs t is a balanced average value of zero symbol. By moving signal power away from the band center, they offer the potential for better gadionavigation accuracy and multipath rejection.

Since BOC modulations offer two independent design parameters — subcarrier frequency and spreading code rate — they provide more freedom for a designer to concentrate signal power within specific parts of the allocated band to reduce interference with the reception of other signals. The prompt tap from the discriminator provides estimates of the despread residual carrier, which can be tracked in a frequency-locked loop or phaselocked loop. The correlation function from sidelobe processing is a bandlimited version of the correlation function for a PSK-R modulation offet the spreading code binayr of the BOC modulation — a much broader correlation function than that of the dual-sideband BOC modulation.

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Betz_Binary Offset Carrier Modulations for Radio Navigation_百度文库

The final section summarizes the findings of this work. This paper has provided two categories of fundamental results in modulation design. This lower bound is based on the performance of a maximum-likelihood estimator of time of arrival using T seconds of radionqvigation, driving a tracking loop. This section outlines a procedure for selecting early — late spacing for NELP based on the theory presented in [7] and [8], and illustrates the Vol.

Binary offset carrier modulation [1] [2] BOC modulation was developed by John Betz, PhD, in order to allow interoperability of satellite navigation systems.

Figure 15 shows results for BOC 5,2 modulation, computed using equation carriee In contrast, modulations designed specifically for radionavigation can outperform existing modulation designs while using the same or even less bandwidth and enabling simple transmitter and receiver designs.

The spectral separation coefficient of BOC 10,5 indicates the degree to which the modulation is isolated from the new military signal, so that high-power M-code signals do not interfere with its reception. The error becomes very large for early — late spacing near offset, corresponding to the slope reversal in the S-curves observed in Figure The columns for BOC 10,5 modulation and For first-order performance analysis of codetracking error in white noise, let the correlation integration time within the discriminator be T units of secondsand let BL units of hertz be the one-sided noise-equivalent rectangular bandwidth of the code-tracking loop.

The S-curve relates the correction produced by a discriminator for a given error. While this bandwidth restriction would cause codetracking error for a 1. Both fit readily within the 24 MHz allocated bandwidth.