Background technology
Along with the number of carriers of mobile communication system and the continuous increase of power, also more and more higher to the intermodulation requirement of equipment.Indispensable matching unit during load covers as each communication requires also corresponding raising to its intermodulation, thereby impels the generation of various low intermodulation load designs.The at present low common scheme of intermodulation load is the Wound-rotor type load, decline naturally by sufficiently long cable realizes load characteristic exactly, it is formed by connecting by a radio frequency coaxial-cable winding that is formed by the coaxial cable coiling and broadband waveguide-coaxial converter or radio frequency connector, can be applicable to the 200MHz of microwave communication equipment or microwave measurement system under the perfect condition in the frequency range of 40GHz, minimum passive intermodulation level can reach-125dBm even lower, thereby satisfies communication system to the high requirement of intermodulation.But in the reality, because the consideration of factors such as cost, the length of coaxial cable can not be oversize, just lost coupling so general Wound-rotor type loads on 500MHz.
Cable shown in Figure 2 decay schematic diagram, L1, L2 and L3 are representing the attenuation of the cable of equal length varying cross-section diameter respectively, L1 diameter maximum wherein, L3 minimum.As can be seen from Figure 2, the cable of equal length, frequency is more high, and it is more big to decay.Because RL=K * L * 2 (general RL 〉=-23dB, also can require to adjust according to difference), wherein RL is return loss; K is the decline system, the loss of expression when cable length is 1 meter; L is cable length; 2 expression reflected signals need be through 2 declines, and namely behind open circuit or short-circuit end, the transmission path that turns back to input port again is equivalent to the length of 2 times of coaxial cables to signal from input port.As can be seen under the same situation of cable length L, RL is directly proportional with K from formula.The conclusion that draws in conjunction with Fig. 2 and the formula of above-mentioned return loss can draw, and RL is directly proportional with frequency.When frequency very low (as 0MHz), return loss RL is 0, regardless of cable length L, return loss RL can't improve, so the cable echo loss is little when low-frequency range (such as 0MHz), causes the standing wave ratio, the effect of power absorption can't be played, load characteristic can't be realized.
Summary of the invention
The purpose that the utility model provides is to provide a kind of low intermodulation performance that both satisfied, and can realize the low intermodulation load of wideband of low-frequency range load characteristic again.
A kind of wideband hangs down the intermodulation load, comprise the radio frequency coaxial-cable winding that formed by the coaxial cable coiling, with broadband waveguide-coaxial converter that the radio frequency coaxial-cable winding is connected, it is characterized in that: the terminal of described coaxial cable is connected with the absorbing medium parts for consumed power.
A kind of wideband hangs down the intermodulation load, comprise the radio frequency coaxial-cable winding that formed by the coaxial cable coiling, with the radio frequency connector that the radio frequency coaxial-cable winding is connected, it is characterized in that: the terminal of described coaxial cable is connected with the absorbing medium parts for consumed power.
The beneficial effects of the utility model are:
1, compare with general Wound-rotor type load, increased the absorbing medium parts, the load characteristic when being implemented in low-frequency range has been widened the application band of load, the minimum 0MHz that reaches.
2, the absorbing medium parts of Zeng Jiaing can consume the dump power of cable termination, reduce the caloric value of cable, improve heat dispersion.
Embodiment
As Fig. 1 and shown in Figure 5, the low intermodulation load of wideband comprises radio frequency coaxial-cable winding, radio frequency connector and absorbing medium parts.The radio frequency coaxial-cable winding is formed by the coaxial cable coiling, and concrete cable length requires and concrete the setting according to the low intermodulation performance of reality.Difference as required, radio frequency connector can adopt broadband waveguide-coaxial converter to replace.The radio frequency coaxial-cable winding is connected with radio frequency connector or broadband waveguide-coaxial converter, and the coaxial cable terminal of radio frequency coaxial-cable winding connects the absorbing medium parts.Signal is imported from input port, arrives its terminal through coaxial cable, no longer derives behind the signal input absorbing medium parts, and namely signal is absorbed media components and has absorbed.
The described cable of Fig. 2 decay schematic diagram, L1, L2 and L3 are representing the attenuation of the cable of equal length varying cross-section diameter respectively, L1 diameter maximum wherein, L3 minimum.As can be seen from Figure 2, the cable of equal length, frequency is more high, and it is more big to decay.Again because RL=K * L * 2, RL is return loss, K is fading coefficients, the loss of coaxial cable when the expression cable length is 1 meter, L is coaxial cable length, 2 expressions transmit 2 times of process declines, after namely signal arrived open circuit or short-circuit end from input port, the transmission path that turns back to input port again was equivalent to the length of 2 times of coaxial cables.By the formula of return loss as can be seen under the situation of same cable length, return loss RL is directly proportional with fading coefficients K, the same in conjunction with cable length that Fig. 2 draws, the conclusion that frequency is directly proportional with decay, can draw under the situation of same cable length, return loss RL is directly proportional with frequency, and frequency is more low, and return loss is more low.When return loss during greater than-23dB, load characteristic will variation, and frequency is more low, and load characteristic is more poor.As seen, cable type loads on low-frequency range and can not realize good load effect.In theory, cable length is more long, cable resistance is more big, it is also more big to decay, so realize high return loss by increasing cable length, if but realize improving load performance by the length that changes cable, the power of signal all is converted into heat energy by the consumption of cable, can cause cable heating and influence the stability of loaded work piece, also can there be the problem of aspects such as cost, volume in the while.So in real world applications, cable length all can not be infinitely great, as long as can guarantee low intermodulation function.
The overall structure schematic diagram of the low intermodulation load of existing Wound-rotor type as shown in Figure 1, the terminal of its standard coaxial cable be for open circuit, in addition the common situation that also has short circuit.The design principle figure of the coaxial cable terminal of existing load as shown in Figure 3 and Figure 4, coaxial cable terminal be respectively the open circuit and short circuit.Under the situation of terminal for open circuit or short circuit of coaxial cable, signal is from importing with the input port of radio frequency coaxial-cable winding, and through arriving the terminal of coaxial cable behind the coaxial cable, remaining signal generation total reflection feeds back to input port by coaxial cable.Through behind this transmission path, most of power of signal all is converted into thermal energy consumption on coaxial cable, but generally speaking, the limited length of coaxial cable can not be fallen the power consumption of signal fully, so still there is part signal to be fed back to input port, when return loss during greater than-23dB, load performance can be influenced, and along with frequency is more low, load performance can be more poor.
Load in the present embodiment shown in Figure 5 is connected the terminal of coaxial cable 2 with absorbing medium parts 3, is different from the open circuit of traditional Wound-rotor type load or the mode of short circuit.Signal is transferred to absorbing medium parts 3 through coaxial cable 2 after importing by input port 1, the power of signal is converted into heat energy through coaxial cable the time, consumed a part, remaining signal power is absorbed media components 3 and all consumes, be converted into other forms of energy, as heat energy etc., can not cause the derivation of signal, be equivalent to signal and be absorbed media components 3 and absorbed.Under the acting in conjunction by coaxial cable 2 and absorbing medium parts 3, particularly under the situation of low frequency, when only high return loss can't be realized by coaxial cable 2, pass through the mating reaction of absorbing medium parts 3 again, improve return loss, the performance of proof load.In addition, adopt the implementation of traditional Wound-rotor type load, low intermodulation performance that can proof load.
Mode by open circuit or short circuit, signal feed back to input port 1 through coaxial cable 2 at open circuit or short-circuit end again through meeting after the total reflection, and in the transmission course, coaxial cable 2 will generate heat twice, cause the temperature of load too high, and influence the stability of its work.And behind the load signal of the present embodiment process absorbing medium parts 3, all consumed, do not have the derivation of signal, can avoid residual signal to feed back to the situation of input port 1 by coaxial cable 3, can not cause the heating again of coaxial cable, reduce the temperature of load, guaranteed the stability of loaded work piece.
Further, the impedance of absorbing medium parts 3 and coaxial cable 2 couplings, for example 50 ohm coaxial cable 2 can be with 75 ohm absorbing medium parts 3 with the coaxial cable 2 of 3,75 ohm of 50 ohm absorbing medium parts.Preferably, the absorbing medium parts can adopt heavy wall resistance or ceramic resistor, and the electronic component of other big power consumptions is suitable for too.
Further, the load of present embodiment also comprises shielding box 4, is set in the outside of coaxial cable 2 terminals and absorbing medium parts 3, is used for preventing the leakage of electromagnetic signal.
As shown in Figure 6, the standing-wave ratio VWSR of present embodiment≤1.0, return loss≤-26dB, load characteristic is good, and the frequency of load can be low to moderate 0MHz, among Fig. 6 because the restriction of tester, only show 100KHz to the frequency range of 3GHz, and intermodulation inhibition index is good.
Obviously, those skilled in the art can carry out various changes and modification to the utility model and not break away from spirit and scope of the present utility model.Like this, if of the present utility model these are revised and modification belongs within the scope of the utility model claim and equivalent technologies thereof, then the utility model also is intended to comprise these changes and modification interior.