350 rub
Journal Antennas №5 for 2009 г.
Article in number:
The investigation symmetrical transformers characteristics of DF antenna array
Authors:
V. M. Balyukov
Abstract:
Conduct experimental research into VHF band was appear that an errors existed in a case of amplitude and phase unbalance of symmetrical transformers characteristics DF antenna array.
Often a function of DF errors depend on structure and technical characteristics of symmetrical transformers.
Wide band symmetrical transformers has amplitude and phase unbalance.
Value of polarization errors is proportional: , ? asymmetry voltage, ? antenna cur-rent; ? pair aerials capacitance in dipole; ? angular frequency.
Equivalent circuit of connections symmetrical antenna by transformers and transmissions line to DF unit (Figure 1).
As to Kirchhoff law total current-burning voltage in circuits is zero.
(1)
Therefore (1) currents, induced in top and bottom circuits are (2):
(2)
where, ? is the sum secondary isolated circuits current, ? out of phase voltage, induced from antenna; ? in-phase voltage, induced from antenna, ? antenna impedance; ? primary transformer impedance; ? mutual induction coefficient; .
, where, ? input antenna feeder line voltage, ? secondary symmetrical transfor-mers impedance, ? primary transformers currents.
(4)
Equations can be reformulated with:
? out of phase gain;
? in-phase gain;
? coupling coefficient.
Input feed line voltage with ABCD parameters:
; (5)
where ? input current and voltage direction finder.
Equation (5) can reformulated with coefficient ABCD parameters as to un losses feed line:
.
Sum input direction finder voltage is:
.
If in-phase voltage is adding to out phase antenna voltage that out feed line voltage is:
. (6)
Magnitude input direction finder sum voltage is:
(7)
In case and . With this assumption, it is easy to modify the equation (7) for max gain ( ) amplitude of unincluded feed line losses.
.
In case of direction-of-arrival with amplitude method four element circular antenna array bearing is:
, and systematic errors are: .
Errors due to the data sheet symmetrical transformers characteristics of DF antenna array:
, где , ? gain antenna-feeder channel with symmetrical transfor-mers of four element circular antenna array.
Manufactured symmetrical transformers (center-tapped transformers) have amplitude and phase unbalance which is a function of insertion loss and frequency bandwidth (1dB, 2dB, 3dB).
Typical amplitude unbalance: 0.1dB over 1dB frequency range; 0.5dB over entire frequency range and phase unbal-ance:1over 1dB frequency range; 5 over entire frequency range.
Figures 2-4 shows error due to unbalance plotted against total balance symmetrical transformers for four element circular antenna array.
- The investigation symmetrical transformers characteristics with feed line of DF antenna array on accuracy. In-crease DF errors due to unbalance symmetrical transformers less than 0.1дБ over 1dB frequency range is not more than 2% at relation aperture to wave length for four element circular antenna array . Increase unbalance magnitude of symmetrical transformers to 0.5dB over entire frequency range involve increasing DF errors to 10%.
References
- Кукес И. С., Старик М. Е. Основы радиопеленгации. - М.: Сов. Радио, 1964.