Multivariate amount to brace up child aerial
Half Zhen Zitian line and amount to Zhen Zitian the gain of the line is small, wave segment or section is broad, ahead and rear have identical reception ability, so they apply to signal only strong, disturb little place, should receive a dot to leave a TV station further, signal weaker or signal is stronger but interference is bigger when reflection wave effect is more serious, be about to use multivariate tall gain is directional aerial, this is multivariate brace up child aerial, call 8 wood aerial again, in active brace up child reflector is added at the back of, director is added in front, form multivariate brace up child aerial, bring Xiang Zhenzi, reflex brace up child with active brace up child the unit number that the amount that add up is aerial. 
Multivariate the rear wave valve of Zhen Zitian line disappears, ahead sensitivity rises greatly, the principle is as follows:
1. reflector chooses the action of the signal that come to ahead P dot and rear Q
The active in right graph brace up child the job is in syntonic condition, its impedance is pure resistor, reflector grows 5%-15% than having Zhenzi with length, and present sensibility. Set reflector and active Zhen Zixiang to be apart from λ / 4, the electromagnetic wave that from the P of aerial ahead the point comes arrives at active first brace up child, the E1 of generation reaction electromotive force that makes, faradic I1. Electromagnetic wave repass λ / the by way of of 4 just arrives at reflector, the E2 of generation reaction electromotive force that makes and faradic I2. As a result of reflector and active brace up child in λ of empty photogenic difference / the distance of 4, e2 is so more backward than E1 90 ° , and I2 presents sensibility as a result of reflector again and lag behind than E2 90 ° , reason I2 is more backward than E1 180 ° , the radiation field that I2 of reflector electric current produces arrives at active brace up child formation magnetic field H2 lags behind than I2 again 90 ° , namely H2 is more backward than E1 270 ° . According to electromagnetism induction law, the E1-2 of inductive electromotive force that H2 produces in active Zhenzi is more backward than H2 90 ° , result E1-2 is more backward than E1 360 ° , that is to say reflector is in active brace up child the E1 of inductive electromotive force of the E1-2 of inductive electromotive force that produces and Yuan Zhenzi is inphase, aerial output voltage is to be equal to E1 and E1-2 the sum, before visible reflector makes aerial is received advocate the sensitivity of signal rose, the derivation with similar ground is knowable: 絈 of midge of courtyard of porcelain Gan Ju nods the signal that come to have the effect of quits output.
The action of 2. director
Director compares active brace up child short 5%-10% , its impedance shows capacitance sex, hypothesis director and active brace up child the distance between also is λ / 4, it is OK to use same method derivation gives undermentioned verdict: Is amine of Yun of Zha Ju chewed blow a small tinkling bell other Hu of card of male lotus root to engrave illuminate does lotus root of Ling Su triangular bream cast Yong?
The place on put together is narrated, the move since reflector removes the effect of the valve after aerial direction pursues, reflector and director have the effect that heightens aerial ahead sensitivity. Thinking stalks of grain
Amateur makes the point of paraboloid antenna---The relation of the radiation deflection Q of the F/D of paraboloid antenna and source of make a present of
F/D (the focus that F is parabola, the caliber that D is parabola) the deflection Q with source of make a present of is appurtenant relation, the diameter of the paraboloid antenna that ability decides to you want to make after the deflection that has cause of make a present of only that is to say is affirmatory reachs focal length. Know F/D=0.3 only as an amateur- - 0.5 it is insufficient, how can just make the form a complete set of an antenna and source of make a present of uses appropriate F/D namely, this problem is very serious, the efficiency that it affects aerial system directly and letter a confusion of voices are compared etc. It is place of source of make a present of is inherent that graph 1-1 place shows Q, source of make a present of decided, q also decided.
The antenna that make should decide source of make a present of above all, only the deflection of source of make a present of is foregone, ability makes the antenna of different diameter by different F/D, and source of make a present of just is made after should not making antenna good, because come so the effect of very inaccessible ideal, sure generation is like the circumstance of graph 1-2 or graph 1-3. The circumstance of graph 1-2 can make ground catoptric clutter enters source of make a present of, and the microwave of aerial brim and diffraction wave also can enter source of make a present of, make the letter a confusion of voices that aerial receives a system is compared reduce. The circumstance of graph 1-3 can make the utilization rate of aerial reduces the waste that creates a person to be and of signal by valve also entered source of make a present of at the same time. The relation of F/D and Q is: F/D=1/4*Ctg Q/2.
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The antenna that so first deflection of source of make a present of makes how many diameter according to you want again decides F=D* after that (1/4*Ctg Q/2) , next according to parabola equation: X=Y*Y/4F scale gives a model.
The caliber of parabola antenna can use next form calculation:
| The deflection of source of make a present of (Q) |
100 degrees |
120 degrees |
160 degrees |
180 degrees |
| The efficiency of aerial (K) |
70% |
60% |
55% |
50% |
General amount to half brace up child source of make a present of (the reflector after the belt) the deflection with source of helix make a present of is 100 degrees or so. Thinking stalks of grain
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