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JANUS frequency-band proposal of EDA-SALSA consortium


Introduction

SALSA (2018-2022) is a European Defence Agency (EDA) project of five nations (Netherlands, Norway, Germany, Sweden, Finland), six industries (Kongsberg Maritime, Wärtsilä ELAC Nautik, ATLAS Elektronik, Develogic, Saab, Patria Aviation) and five research establishments (TNO, FFI, WTD71, Fraunhofer FKIE, FOI). All SALSA participants jointly decided to adopt the following two frequency bands:
  • 4-8 kHz (hereafter marked “LF”);
  • 24-32 kHz (hereafter marked “HF”).
Both LF and HF frequency bands are chosen such that they avoid overlap with the frequency band for military underwater telephony (UWT, 8,087-11,087 Hz, STANAG 1074/1475). The LF band was originally selected in the EDA-RACUN project (2010-2014). The HF band was selected by the SALSA consortium during project preparation and is the overlapping frequency band of the transducers applied by SALSA’s modem suppliers (Kongsberg, ELAC, Develogic, TNO/FFI). The HF band is sufficiently high for avoiding ambient/self-noise and for use by compact AUVs, and is sufficiently low for avoiding AUV sonar interference and for maintaining reasonable communication ranges.

An additional advantage of the HF band is that it falls within the 20-60 kHz frequency band, which is free of export restrictions (EC Regulation 428/2009, ITAR CCL 774/1; Art. 5A001.b.1.a). Furthermore, as the HF band is above 12 kHz, it is available for both military and non-military use.

Problem

The present JANUS standard (STANAG 4748) uses the 9,440-13,600 Hz frequency band, which partially overlaps with the NATO UWT band that should be kept available as much as possible for (emergency) communication with submarines. Furthermore, the JANUS standard defines a Q-factor (centre frequency over bandwidth) of approx. 3, which for the two SALSA centre frequencies (6 and 28 kHz) results in a quite narrow LF band (2 instead of 4 kHz) and in a too broad (>10%) HF band (9.3 instead of 8 kHz).

Proposal

The alternative JANUS bandwidths proposed by SALSA are 2×13×125=3250 Hz and 2×13×250=6500 Hz (81% of the 2 SALSA bands), where 2×13 corresponds to the 13 evenly-spaced tone pairs of the JANUS modulation. Advantage of using 125 and 250 Hz bandwidth for the JANUS carriers is that this translates into integer values for the sample durations (in milliseconds). In combination with the two SALSA centre frequencies, this results in the following two JANUS frequency bands:
  • 4,375-7,625 Hz, for military use
  • 24,750-31,250 Hz, for general-purpose use (export-free)



Dear Henry and SALSA friends,

this is a very welcome proposal as we move JANUS forward. Thank you for this.

I'm particularly happy with the fact that this proposal comes with actual industrial backing.

The 1/3 factor of Bw/Fc should not be rigid. Although we may be losing something at the higher band, the fact that several manufacturers are on board is a great starting point.

Do you have any results with those bands?

Many thanks

João


Dear Joao,

Good to hear that the proposal is welcome!

Yes, we have collected many results for JANUS in both bands this year.
The SALSA consortium is currently analyzing the results...

Best regards,

Henry

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