15.1 Radio Beacon Goniometric Radio Navigation Systems
287
This voltage contains an information on ADP rotation rate (rough channel
frequency) =
2πn
60
= 2π F r , where from at n = 900 rpm, F r = 15 Hz.
The voltage also contains an information on precise channel frequency K =
K
2πn
60
= 2π F p , where F p = 135 Hz.
Signal, containing reference oscillations, is radiated through the central antenna
A 1 . Reference signals of rough and precise channels are transmitted via pulse-code
modulation (PCM).
Transmitter of PVOR radio beacon operates in pulse mode. Each signal of a
transmitter represents a group of two pulses of 3,2 μs duration with fixed interval
between them equals to 12 μs. Radio beacon signals, excepting signals of reference
voltage, have a random distribution in time. Number of chaotically running in time
signals equals to 2700 pulses per second or 180 pulses per one antenna revolution.
Reference signals of rough measuring are transmitted once per one antenna revolution, when a maximum of radiation comes through north direction. North reference
signal represents a sequence of twelve (12) pairs of pulses, following one by one with
a fixed interval of 30 μs. Consequently, for rough measuring, 12 × 15 = 180° pairs
of pulses are transmitted.
Reference signals of precise measuring are transmitted each time when consecutive maximum of nine-lobed characteristic goes through north direction. Reference
signal of precise measuring represents a sequence of six (6) pairs of pulses, following
one by one with a fixed interval of 24 μs. Totally, 6 × 8 = 75° pairs of pulses are
transmitted per second.
Total amount of pulse pairs, radiated per second by PVOR RB, reaches 3600.
Low-frequency voltage of reference signal is produced onboard an AV.
u ref (t) = U rrefM cos ϕ rref + U prefM cos ϕ pref ,
(15.19)
where ϕ rref (t) = t—reference signal phase of rough channel; ϕ pref (t) = K t—
reference signal phase of precise channel.
Availability of two azimuthal and two reference signals permits to conduct two
steps of measurement of phase difference: rough at 15 Hz frequency, precise at
135 Hz. At rough measurements ϕ r (t) = θ r . Azimuth is univalently determined,
but with low accuracy. At precise measurements ϕ p (t) = K θ p , azimuth is determined precisely, but not univalently (single-valued). Two-step measurements permit
to determine azimuth univalently and with high accuracy. Two-step measurement
technique is shown in Fig. 15.8.
Rough measurement of phase difference ϕ r permits to define single-valued
read-out zone of 360
◦
/K width, within limit of which an AV azimuth is located and
to obtain a number of such k zones, including in azimuth. Precise measurement of
phase difference ϕ p permits to define a precise AV position inside of this zone θ p .
AV azimuth is a sum of measurement results: θ = k · 40
◦
+ θ p , 0 ≤ θ p ≤ 40
◦ ,
k = 0, 1, 2, . . . , 8.
If both measurement steps are performed by the same units (phase meters) and
in equal conditions, then measurement errors of phase difference can be considered
as equal. Due to oscillation frequency increase by K times, an accuracy should be
287
This voltage contains an information on ADP rotation rate (rough channel
frequency) =
2πn
60
= 2π F r , where from at n = 900 rpm, F r = 15 Hz.
The voltage also contains an information on precise channel frequency K =
K
2πn
60
= 2π F p , where F p = 135 Hz.
Signal, containing reference oscillations, is radiated through the central antenna
A 1 . Reference signals of rough and precise channels are transmitted via pulse-code
modulation (PCM).
Transmitter of PVOR radio beacon operates in pulse mode. Each signal of a
transmitter represents a group of two pulses of 3,2 μs duration with fixed interval
between them equals to 12 μs. Radio beacon signals, excepting signals of reference
voltage, have a random distribution in time. Number of chaotically running in time
signals equals to 2700 pulses per second or 180 pulses per one antenna revolution.
Reference signals of rough measuring are transmitted once per one antenna revolution, when a maximum of radiation comes through north direction. North reference
signal represents a sequence of twelve (12) pairs of pulses, following one by one with
a fixed interval of 30 μs. Consequently, for rough measuring, 12 × 15 = 180° pairs
of pulses are transmitted.
Reference signals of precise measuring are transmitted each time when consecutive maximum of nine-lobed characteristic goes through north direction. Reference
signal of precise measuring represents a sequence of six (6) pairs of pulses, following
one by one with a fixed interval of 24 μs. Totally, 6 × 8 = 75° pairs of pulses are
transmitted per second.
Total amount of pulse pairs, radiated per second by PVOR RB, reaches 3600.
Low-frequency voltage of reference signal is produced onboard an AV.
u ref (t) = U rrefM cos ϕ rref + U prefM cos ϕ pref ,
(15.19)
where ϕ rref (t) = t—reference signal phase of rough channel; ϕ pref (t) = K t—
reference signal phase of precise channel.
Availability of two azimuthal and two reference signals permits to conduct two
steps of measurement of phase difference: rough at 15 Hz frequency, precise at
135 Hz. At rough measurements ϕ r (t) = θ r . Azimuth is univalently determined,
but with low accuracy. At precise measurements ϕ p (t) = K θ p , azimuth is determined precisely, but not univalently (single-valued). Two-step measurements permit
to determine azimuth univalently and with high accuracy. Two-step measurement
technique is shown in Fig. 15.8.
Rough measurement of phase difference ϕ r permits to define single-valued
read-out zone of 360
◦
/K width, within limit of which an AV azimuth is located and
to obtain a number of such k zones, including in azimuth. Precise measurement of
phase difference ϕ p permits to define a precise AV position inside of this zone θ p .
AV azimuth is a sum of measurement results: θ = k · 40
◦
+ θ p , 0 ≤ θ p ≤ 40
◦ ,
k = 0, 1, 2, . . . , 8.
If both measurement steps are performed by the same units (phase meters) and
in equal conditions, then measurement errors of phase difference can be considered
as equal. Due to oscillation frequency increase by K times, an accuracy should be