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TRANSMIT SPECTRUM ISSUES

TRANSMIT SPECTRUM ISSUES. MANUFACTURERS MEETING AUGUST 2004 Peter Woolner Mitretek Systems pwoolner@mitretek.org 703-610-1724. SOME CHANGE IS NEEDED.

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TRANSMIT SPECTRUM ISSUES

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  1. TRANSMIT SPECTRUM ISSUES MANUFACTURERS MEETING AUGUST 2004 Peter Woolner Mitretek Systems pwoolner@mitretek.org 703-610-1724

  2. SOME CHANGE IS NEEDED • The NTIA controls spectrum allocations and sets performance standards for ALL radio operations by ALL U.S. Government agencies. (See Preface to NTIA Manual.) • The previous proposed change incorrectly cited ITU requirements that NTIA do not allow for transmissions at frequencies below 470 MHz. • The correct performance standard that applies is NTIA subsection 5.2.2.2.

  3. NTIA SPEC FOR 300 BPS

  4. NTIA SPEC FOR 1200 BPS

  5. DEMODULATOR FILTER • NESDIS believes that the explicit transfer function used in the CDA receivers needs to be identified to provide DCPRS designers with a guide for spectral match. • SRRC advantage is reduced adjacent channel interference and minimum ISI, its disadvantage is it has higher peak-to-average power ratio. • Worse peak-to-average power ratio can be eliminated by reducing the maximum output power allowed from any DCPRS by 1 dB. • Therefore a SRRC filter will be recommended for the CDA receivers.

  6. DCPRS FILTER • Narrow band and wide band attenuations must meet NTIA requirements • PROPOSAL: Don’t require DCPRS use SRRC filter – leave it as a design decision

  7. DERIVATION OF REQUIREMENT • NTIA require the mean power of any emission be compared to the mean power of the fundamental • “Fundamental” and “any emission” are not defined but may be inferred from the basic (sin(x)/x) spectral distribution • A spectrum analyzer could use any RBW small enough to resolve the actual sideband peaks and nulls • The NTIA requirement could be reduced by 3 dB because the fundamental is at least twice the bandwidth of any other spectral lobe

  8. DERIVATION (Cont.)

  9. PROPOSED NEW CS TEXT 4.5 DCPRS Transmit Spectrum The DCPRS shall be designed to be received by the CDA stations, which will include a SRRC demodulator filter with α = 1.0, using at least 100 taps [To Be Confirmed]. 4.5.1 Narrow Band Transmit Spectrum When modulated with a random data stream and measured on a spectrum analyzer using any convenient resolution bandwidth of 1 Hz to 100 Hz, the peak response of the unwanted signals, relative to the peak response in the necessary bandwidth, shall be equal to, or better than: At any frequency removed from the assigned channel center frequency by more that 75% of the necessary bandwidth, up to and including 150%, at least 22 dB attenuation. At any frequency removed from the assigned channel center frequency by more that 150%, up to and including 300%, at least 32 dB attenuation. The “necessary bandwidth” is 300 Hz for 300 bps and 1200 Hz for 1200 bps. 4.5.2 Wide Band Transmit Spectrum The power in any sideband, harmonic, or spurious signal, that is more than 900 Hz from the assigned channel center frequency (for 300 bps) or more than 3600 Hz from the assigned channel center frequency (for 1200 bps) shall be at least 60 dB below the power in the unmodulated carrier. If the power of the signal applied to the antenna transmission line is greater than 50 watts, the power in any of these undesired emissions shall be not more than 50 microwatts.

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