Giga-tronics GT 9000, Operation & Maintenance Manual

Page: 218 / 238

A.15 Option 27: Scan Modulation/Linear AM
In instruments with Option 27, a scan modulator (an FET-based variable attenuator) is placed in
the RF path, between the level control system and the output step attenuator. This modulator is
digitally controlled and linearized, and can operate in Scan mode (DC coupled, with depth
specified in dB) or Linear AM mode (AC coupled, with depth specified in per cent).
The modulator can also be used as a variable attenuator; attenuation values entered (in dB) are
relative to the power level set by the instrument’s level control system (if the instrument’s level
is set to -10 dBm, and a variable attenuation value of -12 dB is specified, the instrument’s
actual output level will be -22 dBm). All modes of scan modulation can be operated
simultaneously with pulse modulation and frequency modulation.
Installation of Option 27 can degrade the maximum output level by as much as 2 dB when not
activated, by as much as 8 dB when activated in scan mode or variable attenuation mode, and
by as much as 14 dB when activated in linear AM mode. Also, standard amplitude modulation
(the specifications for which are given in Chapter 1 of this manual) is not available in
instruments with Option 27. All attenuation specifications are relative to the instrument’s
unmodulated output level with the attenuator set to 0 dB.
Specifications (General)
Frequency Of Operation: 100 MHz to 20 GHz.
RF Carrier Harmonics: Not specified.
Specifications (DC Coupled Scan mode, or Variable Attenuator mode)
Max Power Degradation:
≤
8 dB
Range: 0 to 60 dB (>1 GHz); 0 to 55 dB (.5 to 1 GHz); 0 to 55 dB typical (<.5 GHz)
Frequency Response: DC to 150 kHz, sine wave
Step Response:
<1
µ
s, for 50 dB change
Linearity (at cal points):
±
.6 dB (0 to 20 dB);
±
1 dB (20 to 60 dB).
Sensitivity: -10 dB/V
Input Impedance:
50
Ω
, nominal
Specifications (AC Coupled Linear AM Mode)
Max Power Degradation: <14 dB
Modulation Depth: 0 to 90%
Modulation Bandwidth:
10 Hz to 50 kHz,
±
3dB
Input Sensitivity:
1 Vpp, for 50% depth
±
10% depth, at 1 kHz
Input Impedance:
50
Ω
, nominal
Internally Generated Scan/AM Envelope
Waveform: sine, square, or triangle wave
Rate: 1 Hz to 100 kHz
Resolution: 1 Hz
Accuracy:
±
0.01 Hz
Model GT 9000 Microwave Synthesizer
A-12
Manual No. 120AM00250, Rev C, September 1998