Figure 19. Phase modulation vectors for 16-tone DPSK data modem
10. GENERAL
10.1 Scope. This appendix describes the sixteen-tone differential phase-shift keying (DPSK) mode.
10.2 Applicability. This appendix is a nonmandatory part of FED-STD-1052, however, when the
optional 16-tone DPSK mode is used, it shall be implemented in accordance with this appendix.
20. APPLICABLE DOCUMENTS. See section 2.
30. DEFINITIONS. See section 3.
40. GENERAL REQUIREMENTS.
40.1 Introduction. The modulator accepts serial binary data signals at the input and converts this
information into DPSK data tones transmitted at the modulator output. The input data signaling rate
determines the type of modulation and the degree of in-band diversity that is used. The modulation
rate of the modulator output signal is constant for all input signaling rates accepted by the modulator.
The modulator-demodulator (modem) provides a means for synchronization and, if required, a
separate tone for doppler correction. The demodulator accepts the DPSK data tones at the input and
reconverts this information into serial binary data signals at the demodulator output.
40.2 Input/output data signaling rates. The modulator input shall accept, and the demodulator
output shall deliver, a serial binary bit stream with standard data signaling rates ranging from 75 to
2400 bits per second (b/s).
50. DETAILED REQUIREMENTS
| Even and odd bit locations of serial binary bit stream, encoded and phase modulated on each data tone employing: | |||||||
| Quadrature-phase modulation | Biphase modulation | ||||||
| Tone frequency (hz) | Function | 2400 b/s | 1200 b/s | 600 b/s | 300 b/s | 150 b/s | 75 b/s |
605 | Continuous doppler tone | In-band diversity (see par. 50.6) | |||||
825* | Synchronization slot | ||||||
| 935 | Data tone 1 | 1 2 | 1 2 | 1 | 1 | 1 | 1 |
| 1045 | Data tone 2 | 3 4 | 3 4 | 2 | 2 | 2 | 1 |
| 1155 | Data tone 3 | 5 6 | 5 6 | 3 | 3 | 1 | 1 |
| 1265 | Data tone 4 | 7 8 | 7 8 | 4 | 4 | 2 | 1 |
| 1375 | Data tone 5 | 9 10 | 9 10 | 5 | 1 | 1 | 1 |
| 1485 | Data tone 6 | 11 12 | 11 12 | 6 | 2 | 2 | 1 |
| 1595 | Data tone 7 | 13 14 | 13 14 | 7 | 3 | 1 | 1 |
| 1705 | Data tone 8 | 15 16 | 15 16 | 8 | 4 | 2 | 1 |
| 1815 | Data tone 9 | 17 18 | 1 2 | 1 | 1 | 1 | 1 |
| 1925 | Data tone 10 | 19 20 | 3 4 | 2 | 2 | 2 | 1 |
| 2035 | Data tone 11 | 21 22 | 5 6 | 3 | 3 | 1 | 1 |
| 2145 | Data tone 12 | 23 24 | 7 8 | 4 | 4 | 2 | 1 |
| 2255 | Data tone 13 | 25 26 | 9 10 | 5 | 1 | 1 | 1 |
| 2365 | Data tone 14 | 27 28 | 11 12 | 6 | 2 | 2 | 1 |
| 2475 | Data tone 15 | 29 30 | 13 14 | 7 | 3 | 1 | 1 |
| 2585 | Data tone 16 | 31 32 | 15 16 | 8 | 4 | 2 | 1 |
| * No tone is transmitted at this frequency (see par. 50.4). | |||||||
50.2 Data tone frequencies. The frequency of each data tone shall be as listed in Table XXXII. The tone frequencies shall maintain an accuracy of ±0.1 hertz (Hz).
| Input data signaling rate (b/s) | Degree of in-band diversity combining | Type of modulation | Logic sense of dibits or bits in serial binary bit stream depending on: | Phase (in degrees) of data tone signal element relative to phase of preceding signal element | |
| Even bit locations | Odd bit locations | ||||
| Four-phase | MARK | SPACE | +45 | ||
| SPACE | SPACE | +135 | |||
| SPACE | MARK | +225 | |||
| MARK | MARK | +315 | |||
| 600 | Two-phase | MARK* | +315 | ||
| 300 | |||||
| 150 | SPACE* | +135 | |||
| 75 | 16 | ||||
| * Regardless of even or odd bit locations. | |||||
50.3 Phase modulation and encoding. For data signaling rates of 75, 150, 300, or 600 b/s at the modulator input, each data tone signal element shall be two-phase (biphase) modulated as shown on Figure 19a. Each bit of the serial binary input signal shall be encoded, depending on the MARK or SPACE logic sense of the bit, into a phase change of the data tone signal element as listed in table XXXII. For data signaling rates of 1200 or 2400 b/s at the modulator input, each data tone signal element shall be four-phase (quadrature-phase) modulated as shown on Figure 19b. Each dibit of the serial binary input signal shall be encoded, depending on the MARK or SPACE logic sense and the even or odd bit location of each bit, into a phase change of the data tone signal element as listed in Table XXXII. The phase changes of the data tone signal elements specified in Table XXXII shall be relative to the phase of the immediately preceding signal element.
Figure 19. Phase modulation vectors for 16-tone DPSK data modem
50.4 Synchronization. Upon receipt of a transmit command, the modem shall initiate a
synchronization preamble. The preamble shall consist of two tones with frequencies of 605 Hz and
1705 Hz, for a minimum duration of 66-2/3 ms, corresponding to a duration of 5 to 32 data tone
signal elements. The 605 Hz tone shall unmodulated and used for doppler correction, if required.
The 1705 Hz tone shall be phase shifted 180 degrees for each data tone signal element and shall be
used to obtain proper modem synchronization by the demodulator. During the preamble, the
transmitted level of the 605 Hz tone shall be 7 decibels (dB) (±1 dB) higher than the level of the
1705 Hz tone. The composite transmitted signal level of the 605 Hz and 1705 Hz tones during the
preamble shall have a root-mean-square (rms) value within ±1 dB of the rms value of the
modulator output signal level during data transmission when all 16 data tones plus doppler correction
tone are transmitted. At the completion of the preamble, all data tones shall be transmitted for the
duration of one signal element (13-1/3 ms) prior to the transmission of data to establish a phase
reference. During data transmission, synchronization shall be maintained by sampling the signal
energy in the 825 Hz synchronization slot. No tone shall be transmitted in the synchronization slot
of 825 Hz.
50.5 Doppler correction. For those applications where a doppler correction capability is required,
a tone with a frequency of 605 Hz shall be used. The level of the 605 Hz tone shall be 7 dB (±1
dB) higher than the normal level of any one of the subcarriers.
50.6 In-band diversity combining. In-band diversity combining shall be accomplished at data
signaling rates from 75 b/s to 1200 b/s. The data tones shall be combined in accordance with table
XXXI. The degree of diversity combining shall be as listed in Table XXXII.