The spectrum
Analyzer permits the detection of spectrum
components of electrical signals in the frequency range of
0.15 to 1050 MHz for Models
2625 and
2630 and 0.15 to 500
MHz for Models 2615 and 2620. The detected signal and its
content have to be repetitive. In contrast to an
Oscilloscope operated in Yt mode, where the amplitude is
displayed on the time domain, the spectrum
Analyzer displays
amplitude on the frequency domain (Yf). The individual
spectrum components of “a signal” become visible on a
spectrum
Analyzer. The
Oscilloscope would display the same
signal as one resulting waveform.
Models
2625 and 2630
The spectrum
Analyzer works according to the triple superhet
receiver principle. The signal to be measured (fin = 0.15
MHz to 1050 MHz) is applied to the 1st mixer where it is
mixed with the signal of a variable voltage controlled
Oscillator (fLO 1350 MHz - 2350 MHz). This
Oscillator is
called the lst LO (local oscillator). The difference between
the
Oscillator and the input frequency (fLO - fin = 1st IF)
is the first intermediate frequency, which passes through a
waveband
Filter tuned to a center frequency of 1350 MHz. It
then enters an
Amplifier, and this is followed by two
additional mixing stages, oscillators and amplifiers. The
second IF is 29.875 MHz and the third is 2.75 MHz. In the
third IF stage, the signal can be selectively transferred
through a
Filter with 400 kHz or 20 kHz bandwidth before
arriving at an AM demodulator. The logarithmic output (video
signal) is transferred directly, or via a low pass
Filter to
another
Amplifier. This
Amplifier output is connected to the
Y deflection plates of the CRT.
Models
2615A and 2620A
The spectrum
Analyzer works according to the triple superhet
receiver principle. The signal to be measured (fin = 0.5 MHz
to 500 MHz) is applied to the 1st mixer where it is mixed
with the signal of a variable voltage controlled
Oscillator
(fLO 610 MHz - 1110 MHz). This
Oscillator is called the 1st
LO (local oscillator). The difference between the
Oscillator
and the input frequency (fLO - fin = 1st IF) is the first
intermediate frequency, which passes through a waveband
Filter tuned to a center frequency of 609.5 MHz. It then
enters an
Amplifier, and this is followed by two additional
mixing stages, oscillators and amplifiers. The second IF is
29.5 MHz and the third is 2.9 MHz. In the third IF stage,
the signal can be selectively transferred through a
Filter
with 250 kHz or 20 kHz bandwidth before arriving at an AM
demodulator. The logarithmic output (video signal) is
transferred directly, or via a low pass
Filter to another
amplifier. This
Amplifier output is connected to the Y
deflection plates of the CRT.
The X deflection is performed with a ramp
Generator voltage.
This voltage can also be superimposed on a dc voltage which
allows for the control of 1st LO. The spectrum
Analyzer
scans a frequency range depending on the ramp height. This
span is determined by the scan width setting. In ZERO SCAN
mode only the direct voltage controls the 1st LO.
Models
2620A and
2630 each include a tracking
Generator.
This
Generator provides sine wave voltages within the
frequency range of 0.1 to 1050 MHz for Model
2630 and 0.1 to
500 MHz for Model
2620A, The tracking
Generator frequency is
determined by the first
Oscillator (1st LO) of the spectrum
Analyzer section. Spectrum
Analyzer and tracking
Generator
are frequency synchronized.
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