Modulators, Uplink RF, IF & Sub-Carrier

Model 786 PSK Subcarrier Command Modulator
Model 786 PSK Command Modulator

Model 786 contains the facilities to generate a subcarrier modulated with data received via the RS232 Remote Control, direct TTL serial data and clock inputs from the rear panel, or from the internal pseudo-random or fixed data pattern generators. The modulator is capable of applying any of the standard IRIG codes to the data prior to using it as the modulation stimulus. Modulation types are BPSK and QPSK.

Data received via the RS232 interface is placed into a First-In-First-Out (FIFO) memory buffer. Modulation of the subcarrier with this data is initiated either automatically or by the issuance of a start command (Burst Mode). In between bursts of data a user specified idle data sequence is applied to the subcarrier. Additional start commands can be issued to retransmit a data sequence stored in the FIFO. TTL external data and clock can also be selected by the user as the modulation source. This information is applied directly to the modulation input of the subcarrier generator. It is not stored in the FIFO. A third data source is a pattern generator located on the modulator subcarrier generator. It can generate a 215 -1 PRN pattern; or a continuously repeated fixed word pattern: 1100, 0111, 1010, 1000, 1111, or 0000. The selected data may be passed on to the bit code converter that can decode and / or encode data in NRZ-L/M/S, BiPhase-L/ M/L or DM-M/S.

  1. BPSK or QPSK Modulation
  2. Coherent BPSK Modulation
  3. Tunable Subcarrier (DC to 10 MHz)
  4. Data Input TTL or RS-232
  5. Burst or Continuous Output
  6. Programmable Idle Data
  7. Internal Pseudo-Random Data Generator
  8. Modulated Subcarrier Output Level Adjustable from +20 dBm to –30 dBm
  9. All functions Controlled via Front Panel or Remote Control (RS-232)
  10. Full IRIG NRZ, BiPhase, DM Data Encode / Decode
  11. 3 1/2 inch high standard Rack Mount Chassis with Slides

MODULATION DATA — Selectable: External Data/Clock, Internal PRN Data, RS232.
External Data (J4) and Clock (J6) Inputs:
Data/Clock
0 degree clock required for code conversion
Signal levels
TTL, unbalanced
Data rate
1 bps to 10 Mbps. Nominally, data rate should be less than 1/4 subcarrier frequency for PSK modulation

RS232 DATA:
Received via RS232 Remote Control interface. Data bytes (8-bit) are stored in FIFO memory and serialized to the input of the Modulator. (Burst or Streamer mode)
Burst Mode
Start command required to start transfer.
Streamer Mode
Transfer is immediate and continuous
Input Data Rate
RS232 Interface, selectable 300 to 38.4K baud.
Idle Data (Burst Mode)
zeros, ones, dotting , or settable eight-bit pattern.

Internal Data Generator:
PRN Pattern
215 - 1 pattern length;
Recursive word patterns
1-0-0-0; 0-1-1-1; 1-0-1-0; 1-1-0-0; 0-0-0-0 and 1-1-1-1

EXTERNAL REFERENCE INPUT
Amplitude
1.0 Vpp, 75 ohms (sine wave)
Frequency
Selectable; 1 MHz, 2 MHz, 5 MHz or 10 MHz

SUB-CARRIER GENERATOR
Frequency
Tunable from DC to 10 MHz; Resolution: 0.01 Hz; Sine wave
Frequency Accuracy
100 ppm, (Optional, to 1 ppm)
Amplitude adjustable from 0.5 Vpp to 2.8 Vpp; 75 Ohms

BPSK/QPSK MODULATOR OUTPUT
BPSK
Coherent or Non-coherent (Coherent BPSK limited to 2 MHz.)
QPSK
Absolute or differential mode.
Code Conversion
NRZ-L/M/S, BiPhase-L/M/S, DM-M/S , BYPASS