Real-Time I/Q Baseband Generator User’s and Programming Guide
6-3
ESG Family Signal Generators
Theory of Operation
Options UN8 and 202
Data and Control Bits in Pattern RAM
I/Q Modulator
The I/Q modulator supplies the modulating signal to the RF hardware.
RF Hardware
The RF hardware produces the carrier signal and modulates it with the I/Q modulator.
Burst Modulator
The burst modulator controls the amplitude of the RF signal.
Data and Control Bits in Pattern RAM
Pattern RAM not only contains the data bits to be modulated, but also contains the control
bits for digitally modulating the carrier with burst.
The signal generator’s firmware adds seven control bits to each bit of data to be modulated.
Therefore, each bit of user-defined data is contained within an 8-bit byte, or “address” in
pattern RAM. Each byte in PRAM is organized as shown in the following table.
When designing waveform data for subsequent direct download into pattern RAM, every
bit of “modulation data” must be accompanied by these other seven control bits, forming an
8-bit byte that will occupy a specific address in PRAM. For further information, refer to the
programming guide.
Table 6-1 Control Bit Definitions for a Pattern RAM Address
Bit
Function
Value
Description
0
Data
0/1
This bit is the data to be modulated.
This bit is a “don’t care” when burst (bit 2) is set to 0.
1
Reserved
0
Always 0.
2
Burst
0/1
1 = RF on
0 = RF off
For non-bursted, non-TDMA systems, this bit is set to 1 for all
memory locations, leaving the RF output on continuously.
For framed data, this bit = 1 for on timeslots and 0 for off timeslots.
3
Reserved
0
Always 0
4
Reserved
1
Always 1
Summary of Contents for ESG series
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