that will be the easiest for making schemes, quick and accurate calculations and have
low requirements for the capabilities of the computer. The best way for our
development is to chose Micro-Cap 9.
Fig. 4.1 shows developed circuit in the mode of the sweep frequency oscillator.
Figure 4.1. Scheme of frequency characteristic meter
Start frequency is
0
37,5кГц
f=
, velocity of frequency changing –
50кГц/с
=
.
3
32
2
sin(2
37,510
5010
)
E
t
t
=
+
.
In the input of the stroboscopic mixer provides sum of reference generator’s
harmonics V1, V2 with frequencies 50 kHz and 50.01 kHz (Fig 4.2, conditionally 10
harmonics) or 50 kHz and 50, 1 kHz (fig. 4.3, conditionally 100 harmonics). The output
of mixer X1 connected with a bandpass filter (R1, C1, R3, C3) with a critical
frequencies 250 kHz and 24.75 kHz. The low pass filter at the output of the quadrator
X2 (R2, C2) has a bandwidth of 250 kHz. The time of transients is equal to 0.5 s, and
pulse at the output of the marker maker (Fig. 3.1) appears in the middle of the time
dependencies and corresponds to the instant frequency of the swip-generator – 50 kHz.
Fig. 4.2, 4.3 shows the time dependences of the voltage at the input of the quadrator
X2 and the output of the circuit.
Calculation by (3.1) gives the correct result for fig. 4.2 and 4.3 respectively:
1
50,01
50(кГц),
5,0015
M
f
==
−
1
0,50,1
50(кГц).
0,50010,5
M
f
==
−
In fig. 4.4 and 4.5 depicted the studied scheme and the results obtained for the
fixed frequency of the swip-generator V2. This case has not been considered in detail
in this work. The purpose of this work is to show that the meter accurately determines
the frequency F of the oscillation at the output of the circuit in case of stopping the
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