coordinate marks in the swip-generator’s oscillation band (SG) (fig. 3.2, g).
Beginning from the third deployment period of the swip-generator, the
microcontroller turns off the second reference generator. At the output of the device
form pulses of coordinate marks M (fig. 3.2, g). Expression (3.1) doesn’t include the
frequency of the sweep generator, so non-linearity of deployment doesn’t affect the
accuracy of determining the coordinate marks frequency.
Next step we will analyze the work of the meter according to structural model
(fig. 3.3), which shows the voltages u at different points, the coefficients of
transmission (TC) to individual nodes, the frequencies of the swip-generator and the
reference generators.
The frequency of the output voltage of the swip-generator changes in time
according to expression
0
SG
f
f
t
=+
, (3.2)
where,
0
f – start frequency;
– velocity on frequency change.
SG
SM
LPF1
CF
LPF2
ADD
RG1
RG2
Input
Output
1
nf
2
nf
IN
SG
uu
=
К
SM
SM
u
1
К
F
К
CF
2
К
F
CF
u
1
F
u
2
OUT
F
uu
=
ADD
K
2
u
1
u
ADD
u
Figure 3.3. Structure model of frequency meter
Output voltage of swip-generator:
(
)
(
)
2
0
cos2
cos2
SG
SG
SG
SG
u
U
ftdt
U
ft
t
=
=
+
. (3.3)
Output voltage provides to the first input of the stroboscopic mixer SM, to the
second input through adder (ADD) provides the amount of two voltages
12
uu
+ from
the reference generators. Voltages
1
u і
2
u have many harmonics with frequencies that
is multiple to
1
f і
2
f respectively.
Let`s see the situation when we have active (those that create a useful
transformation product) n harmonics.
Therefore, we have a situation when the frequency of first reference generator
1
f
- 476 -