The Model 793 Multimode Modulator is a B/S/QPSK subcarrier generator and modulator, a PM/FM/AQPSK subcarrier generator and modulator, a programmable psuedorandom number (PRN) data generator and an IRIG-106 code converter with convolutional encoding and V.35 and V.35M data randomizing. The unit can be phaselocked to an external station reference frequency.

Features

• Tunable Modulated Subcarriers
• B/S/QPSK Modulation Data Rates to 6.25 Mbps
• AQPSK Modulation Data Rates to 7.5 Mbps / Input
• FM Modulation Index 0 to 10 MHz/V

• PM Modulation Index 0 rad to 3.14 rad/V
• Code Converters IRIG-106
• PRN Data Generator
• Data Randomizer V.35 / V.35M
• Convolution Encoder

The B/S/QPSK modulator accepts externally supplied data and clock, or the internally generated PRN data and clock. The selected data source is used to BPSK, QPSK or SQPSK (Staggered QPSK) modulate a subcarrier which is tunable to 10 MHz The B/S/QPSK output is internally connected as a selectable modulation input to the FM/PM modulator.

The PRN bit rate is tunable to 10 Mbps and the PRN generator may be programmed to output a pseudo-random pattern up to 223-1 bits in length or one of several preset recirculating word patterns. Modulation data can be selectively processed by a differential code converter, convolutional encoder (rate ½, K=7, 9) and a V.35 data randomizer.

The B/S/QPSK Modulation can be turned off to provide a continuous wave (CW), sinusoidal subcarrier output. The modulator output level is adjustable from -20 dBm to +10 dBm. Modulation data and clock are output via the unit rear panel.

The FM/PM/AQPSK modulator can output an AQPSK (Asynchronous QPSK), PM or FM modulated subcarrier. In the AQPSK modulation mode, the modulator accepts two externally supplied asynchronous TTL data and clock inputs. Two independent differential code converters can process the modulation data. I/Q channel unbalance is programmable up to 30 dB permitting adjustment of the ratio of energy per bit (Eb) to noise density (N0) for two modulation channels of unequal modulation data rates.

When set for frequency modulation (FM) mode or linear phase modulation (PM) mode, the modulator accepts up to two analog inputs that are linearly summed prior to modulation. The FM/PM/AQPSK subcarrier is tunable to 20 MHz. Modulation can be turned off to provide a continuous wave (CW) subcarrier output. The modulator output level is adjustable from -20 dBm to +10 dBm.