# Presentation: 226795

## NTIA TRANSMIT SPECTRUM REQUIREMENTS FOR THE REVISED DCPRS CERTIFICATION STANDARDS

- DCS MANUFACTURERS MEETING NOVEMBER 10, 2004
- Peter Woolner
- Mitretek Systems
- _[pwoolner@mitretek.org](mailto:pwoolner@mitretek.org)_
- 703-610-1724

## OUTSTANDING QUESTION AT AUGUST O4 MEETING

- What is the meaning of NTIA Manual section 5.2.2.2? (Go to _[www.ntia.doc.gov](http://www.ntia.doc.gov/)_ and select Publications and Reports.)
- The mean power of any emission supplied to the antenna transmission line, as compared with the mean power of the fundamental, shall be in accordance with the following:
- 1. On any frequency removed from the assigned frequency by more than 75 percent, up to and including 150 percent, of the authorized bandwidth, at least 25 decibels attenuation;
- 2. On any frequency removed from the assigned frequency by more than 150 percent, up to and including 300 percent, of the authorized bandwidth, at least 35 decibels attenuation; and
- 3. On any frequency removed from the assigned frequency by more than 300 percent of the authorized bandwidth:
- b. For transmitters with mean power less than 5 kilowatts, spurious output shall not exceed 50 microwatts (i.e., 43 + 10 log (pY)) decibels attenuation

## NTIA DEFINITIONS

- “Fundamental” refers to the signal at or near the desired frequency, as compared to harmonics of that frequency.  The word “fundamental” may be applied to either a modulated or an unmodulated signal.
- 	(From conversation only)
**“****Emission: **Radiation produced, or the production of radiation, by a radio transmitting station.”
- 	(Subsection 6.1, Page)
- Necessary Bandwidth = 2RK/Log2 (S)
- 	R = Data transmission rate over the radio link (= user rate / code rate)
- 	K = Ratio between 0.5 and 1.0, (= 1.0 for an excess bandwidth factor of 1.0)
- 	    = (1 + α) / 2
- 	S  = Number of signaling states (= 8 for 8PSK)
- 	(Table A part III, page J-14)

## NTIA CONCERNS

- NTIA view the requirement in subsection 5.2.2.2 as similar to the requirement in 5.6.2 except no bandwidth is specified for the measurement.
- The level of any peak must be accurately measured, so there is no averaging of high and low parts of an emission.
- NTIA refused to change any part of the existing requirements without extensive analysis and discussion as they want to be sure any change would correctly apply to all possible modulation types, symbol rates, etc.

## NTIA RESPONSE

- The intent of subsection 5.2.2.2 of the NTIA Manual is to compare the power per Hertz in the out-of-band frequency ranges identified therein, with the maximum power per Hertz in the authorized bandwidth.  Therefore the bandwidth used to show compliance with 5.2.2.2, must be narrow enough to accurately measure the power at each peak of the emission when normal modulation is applied.
**The ratio of the peak power per Hertz in the authorized bandwidth to the power per Hertz at each peak in the out-of-band frequency ranges shall comply with the limits specified in sub-parts 1, 2, and 3 of 5.2.2.2.**
- It should be noted that subsection 5.1.5 requires that the resolution bandwidth to be used for power spectral density measurements should not be greater than the necessary bandwidth of the transmitter being measured.  This implies a lesser bandwidth may be used, and it is recommended it should be used if it is necessary to provide an accurate measurement of all peaks in the emission.

## NTIA SPEC FOR 300 BPS

- NB = Necessary Bandwidth

- 0.75 NB

**NTIA Emission**
**Requirement**

**Theoretical Square**
**Wave Power Dist.**

- 3.0 NB

- 1.5 NB

- -53 dB applies
- to 10 watt Tx

## NTIA SPEC FOR 1200 BPS

- 0.75 NB

- 1.5 NB

- 3.0 NB

**NTIA Emission**
**Requirement**

**Theoretical Square**
**Wave Power Dist.**

- NB = Necessary Bandwidth

- -53 dB applies
- to 10 watt Tx

## JURISDICTIONAL QUESTION

- NTIA cites the Communications Act (1934) and Executive Order 12046 of 1978 as its source of authority over all Federal Agencies.
- NESDIS has set precedents of acceptance by revising GOES N application and by submitting this question to them.
- All existing DCPR transmitters do not comply with NTIA regulations, but in my opinion, existing units do not need to be changed unless some entity can show it is being harmed by the old units and it will stop if compliant units are used.

## SUGGESTED 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 an excess bandwidth factor, α, of 1.0 for 300 bps and for 1200 bps.
- 	When modulated with a random data stream and measured on a spectrum analyzer using a 1 Hz resolution bandwidth, the peak response of the undesired part of the emission, relative to the peak response in the necessary bandwidth (NB), shall be equal to, or better than the following limits.  (The NB is 300 Hz for 300 bps and 1200 Hz for 1200 bps.)
- At any frequency removed from the channel center frequency by more than 75% of the NB, up to and including 150%, at least 25 dB attenuation.
- At any frequency removed from the channel center frequency by more than 150%, up to and including 300%, at least 35 dB attenuation.
- At any frequency removed from the channel center frequency by more than 300% of the NB, at least 43 + 10 log (P) dB attenuation, where P is the total mean power in watts in the necessary bandwidth.

## 300 BPS CHANNELS (α=1)

## 1200 BPS CHANNELS (α=1)

## 300 BPS CHANNELS (α=0.22)

## 1200 BPS CHANNELS (α=0.22)

## RECOMMENDATIONS

- Use 750 Hz channels for 300 bps links
- Use 2250 Hz channels for 1200 bps links
- Use a necessary bandwidth of 300 Hz for 300 bps and 1200 Hz for 1200 bps
- Use RRC filters with α = 1.0 because:
- Studies seem to show relatively small differences between Bessel and RRC
- Greater back-off limits transponder loading
- Receive filter will pass less OOB energy
- RRC can be fully specified as an ideal