A kind of temperature compensation means of 3.5GHz frequency band filter
Technical field
The utility model relates to filter, particularly relates to a kind of temperature compensation means of 3.5GHz frequency band filter.
Background technology
Along with the continuous development of microwave technology, system operator is more and more higher to the performance requirement of microwave passive component, and wherein temperature drift is the important indicator of weighing the passive cavity filter performance always.Because the characteristic that metal self expands with heat and contract with cold make that in low temperature and hot environment, the resonance frequency of filter self changes, thereby free transmission range changes, loss is inserted in influence, return loss, indexs such as the outer inhibition of band.It is big more that temperature is floated amplitude, and the difficulty that other indexs realize is just high more, therefore how to reduce the amplitude of temperature drift as far as possible, becomes the problem that needs emphasis to consider in the Design of Filter.
Chang Yong temperature compensation now is to use different metal materials to come process chamber and resonant rod respectively, utilizes the difference of the intermetallic coefficient of expansion, and the distance between resonant rod top and the cavity top (below abbreviate gap as) is carried out temperature-compensating.Generally speaking, the cavity of filter often uses aluminium to process, and resonant rod can adopt brass according to the difference of frequency range, materials processings such as stainless steel.
Traditional temperature compensation, lower in frequency, below 3GHz, under the less situation of cavity, good compensation characteristic can be arranged.But along with frequency raises, cavity increases, and the situation of undercompensation will occur, is embodied in, and temperature raises, and band connection frequency is low to be floated; Otherwise the band connection frequency height floats.Should guarantee centre frequency, reduce gap again as far as possible, become the principal contradiction in the temperature-compensating process in this case.
Summary of the invention
Technical problem to be solved in the utility model is exactly the temperature compensation means that a kind of 3.5GHz frequency band filter is provided for the defective that overcomes above-mentioned prior art existence.
The purpose of this utility model can be achieved through the following technical solutions: a kind of temperature compensation means of 3.5GHz frequency band filter, it is characterized in that, comprise filter cavity, cushion block, resonant rod, cover plate and tuning screw, described filter cavity is cylindrical, described cushion block is in the form of annular discs, this cushion block is located at the bottom of filter cavity, and it is concentric with filter cavity, described resonant rod is fixed on the cushion block, described tuning screw is positioned at the top of resonant rod, both are concentric, an end of this tuning screw by nut fixing with cover plate on.
The diameter of described filter cavity is 42mm.
The height of described cushion block is 4mm, and diameter is 16mm.
Described cushion block is the invar cushion block.
The height of described resonant rod is 6.8mm, and diameter is 6mm.
Described tuning screw diameter is 3mm.
Described tuning screw is a brass screw.
Compared with prior art, cushion block of the present utility model adds the form of resonant rod, can significantly reduce gap, thereby further strengthen effect temperature compensation not changing under the prerequisite of resonance frequency substantially.
Description of drawings
Fig. 1 is a structural representation of the present utility model.
Embodiment
Below in conjunction with accompanying drawing the utility model is described further.
As shown in Figure 1, a kind of temperature compensation means of 3.5GHz frequency band filter, comprise filter cavity 1, cushion block 2, resonant rod 3, cover plate 4 and tuning screw 5, described filter cavity 1 is cylindrical, described cushion block 2 is in the form of annular discs, this cushion block 2 is located at the bottom of filter cavity 1, and it is concentric with filter cavity 1, described resonant rod 3 is fixed on the cushion block 2, described tuning screw 5 is positioned at the top of resonant rod 3, both are concentric, an end of this tuning screw 5 by nut fixing with cover plate 4 on.
The diameter of described filter cavity is 42mm; The height of described cushion block is 4mm, and diameter is 16mm; Described cushion block adopts the invar cushion block; The height of described resonant rod is 6.8mm, and diameter is 6mm; Described tuning screw diameter is 3mm; Described tuning screw adopts brass screw.
During assembling, cushion block and resonant rod with same screw at cavity bottom.Cavity depth 16mm, resonant rod, cushion block, cavity bottom boss height and be 12mm, frequency can reach requirement, and the distance at resonant rod distance from top cavity top is 4mm.And according to conventional design, the resonant rod height is 9mm, and the distance at top and cavity top is 7mm.So the design can reduce the distance between resonant rod top and the cavity top greatly, thereby plays temperature compensation function.