GW Instek SFG-830 User Manual - Manual (Page 40)

SFG-830 p.37
(3) Triangle Waveform
When the user input a frequency, the MPU will calculate the correspondent data
then save it in RAM(II) (U211-U213), and save the number of the data in the
Up/Down Counter (U215-U218) 74F193. As the Up/Down counter is controlled
by the B11 in DDS1 through 74F193 CLK Input, the desired frequency value can
be obtained by changing the counter’s reading frequency, i.e., the frequency of
CLK. The output frequency of triangle waveform is lower that that of sine waveform
and square waveform due to the different paths. The triangle wave passes a 7-
level LPF1 and does not go through F.D.
(4) Ramp
The procedure of generating ramp is the same as that of generating triangle
waveforms.
(5) AM Modulation
This includes internal modulation and external modulation with the same operation
procedure. Take internal modulation for example, the input data will be calculated
by MPU and be written in RAM(III) (8k
×8); the Up/Down Counter will then read out
the data in RAM and send it to the Amplitude Control (U501, AD834) via DAC.
Different input voltages can change the output voltages of Amplitude Control, thus
achieve the modulation effect.
(6) Sweep
(a) Sine wave and Square wave:
As to the sine wave sweep, the input data will be calculated by MPU and be
written in RAM(I) (8k
×8); DDS2 will then send a fixed frequency to read the
sweep data from RAM(I), and send it to DDS1 through the Bus Selector. The
digital sine wave signal generated from DDS1 will pass DAC, 9-level LPF, F.D.,
Amplitude Control, Output Amplitude, ATT, then output via DUT.
The procedure of square wave sweep is similar to the above one, except that
the digital signal generated from DDS1 passes a Square Waveform
Comparator between the F.D. and Amplitude Control.
(b) Triangle wave and Ramp:
The input data will be calculated by MPU and be written in RAM(II); DDS1 will
then send a B11 control frequency to read the sweep data from RAM(II).
Afterwards, the signal will pass the Bus Selector, DAC, 7-level LPF, Amplitude
Control, Output Amplitude, ATT, then output via OUT BNC.
(7) FM Modulation
The principle of FM modulation is the same as that of Sweep, except that the data
stored in RAM (I) is relevant to FM modulation.