Any dual-frequency band 3dB branch directional coupler
Technical field
The present invention relates to a kind of microstrip line branch directional coupler, relate in particular to a kind of any dual-frequency band 3dB branch directional coupler.
Background technology
Its branch line electric bridge of microstrip line branch directional coupler commonly used at present is made up of two ribbon feeders, realizes coupling by branch line, all is 1/4th operation wavelengths in the length of centre frequency top set line and interval therebetween.Because the linear phase-frequency response characteristic of branch line, such directional coupler can only be operated in design frequency f
0With its odd frequency multiplication such as 3f
0, 5f
0... on.And in two-band or multiband communication system, the selection of each band frequency is independently, is not the relation of odd frequency multiplication generally, so traditional branch directional coupler can not directly satisfy the logical frequency range requirement of these systems.
In April, 2004, the T.Itoh professor of Univ California-Los Angeles USA has reported any dual-frequency directional coupler that utilizes left-right-hand composite transmission line to realize on the 52nd phase of IEEE TransactionsMicrowave Theory Techniques.On each microstrip branch line of this coupler, all loaded the series capacitance and the shunt inductance of lump, thereby realized nonlinear phase frequency response, and then the directional coupler that centre frequency is respectively 930MHz and 1780MHz has been finished in design.Yet, because the bigger further research and extension that has limited this type of directional coupler of parameter such as the finiteness of the discrete choosing value of lamped element and parasitic drains.In addition, the left-right-hand composite transmission line based on complete little band distributed frame also should not directly apply in the design of directional coupler because complex structure is difficult to precise design.
Summary of the invention
Technical problem: goal of the invention of the present invention provides a kind of any dual-frequency band 3dB branch directional coupler, this any dual-frequency band 3dB branch directional coupler can work in any dual-frequency band, simple in structure, loss is little, be convenient to processing and cost low.
Technical scheme: any dual-frequency band 3dB branch directional coupler of the present invention, comprise first branch line and second branch line, between first branch line and second branch line, be provided with the 3rd branch line and the 4th branch line, and above-mentioned four branch lines form rectangle, and be respectively equipped with the first input end mouth and second input port at the two ends of first branch line, be respectively equipped with first output port and second output port at the two ends of second branch line, at above-mentioned first branch line, second branch line, the inboard of the 3rd branch line and the 4th branch line is respectively equipped with distributed inductance, end at distributed inductance is provided with plated-through hole, and plated-through hole is connected down on the metallic plate.
Distributed inductance is located at the middle part of first branch line, second branch line, the 3rd branch line and the 4th branch line respectively.
The outside at described first branch line, second branch line, the 3rd branch line and the 4th branch line is respectively equipped with metal patch, and each metal patch and corresponding distributed inductance are symmetrically distributed in the both sides of every branch line.
Distributed inductance linearly or curve.
Beneficial effect: compared with prior art, the present invention has the following advantages:
1, the present invention can be operated in any dual-frequency band.Four branch lines of the present invention have formed four reduced form left-right-hand composite transmission lines together with the distributed inductance of inboard, this distributed frame has taken into full account the equivalent electric circuit dispersion characteristics of microstrip line with frequency, and this just makes this type of novel coupler can work in any microwave frequency band.Because the effect of the inboard distributed inductance that connects makes this type of reduced form left-right-hand composite transmission line keep the part nonlinear phase-frequency response characteristic of traditional left-right-hand composite transmission line, and then makes the present invention can work on the double frequency-band of any needs.
2, the present invention is simple in structure, and it is low to be convenient to processing and cost.With respect to lumped-circuit of the prior art, employing distributed inductance of the present invention and then formed discrete circuitry, like this, just make that the present invention is simple in structure, the present invention adopts single-layer printed circuit plate (PCB) explained hereafter, one-shot forming need not external any lamped element, thereby is convenient to processing, has reduced production cost.
3, loss of the present invention is little and be convenient to regulate.Because the present invention adopts distributed microstrip structure, this has just reduced because use the influence such as welding loss, lamped element parameter error dispersion etc. that lamped element brought, make the loss of the present invention when work reduce, simultaneously owing to distributed inductance is located at the middle part of branch line, and be provided with metal patch in the outside of branch line, can regulate the performance of operating frequency passband of the present invention easily.
Description of drawings
Fig. 1 is a structural representation of the present invention.
Fig. 2 is a S parameter amplitude simulation result of the present invention.
Fig. 3 is a S parameter amplitude experimental measurements of the present invention.
Fig. 4 is the phase difference emulation and the measurement result of first output port of the present invention and second output port.
Have among the above figure: first branch line 1, second branch line 2, the 3rd branch line 3, the 4th branch line 4, distributed inductance 5, plated-through hole 51, following metallic plate 8, metal patch 9, first input end mouth 10, second input port 11, first output port 12, second output port 13.
Embodiment
A kind of any dual-frequency band 3dB branch directional coupler, comprise first branch line 1 and second branch line 2, between first branch line 1 and second branch line 2, be provided with the 3rd branch line 3 and the 4th branch line 4, and above-mentioned four branch lines form rectangle, and be respectively equipped with the first input end mouth 10 and second input port 11 at the two ends of first branch line 1, be respectively equipped with first output port 12 and second output port 13 at the two ends of second branch line 2, at above-mentioned first branch line 1, second branch line 2, the inboard of the 3rd branch line 3 and the 4th branch line 4 is respectively equipped with distributed inductance 5, be provided with plated-through hole 51 in the end of distributed inductance 5, plated-through hole 51 is connected down on the metallic plate 8, and distributed inductance 5 is located at first branch line 1 respectively, second branch line 2, the middle part of the 3rd branch line 3 and the 4th branch line 4.
The outside at described first branch line 1, second branch line 2, the 3rd branch line 3 and the 4th branch line 4 is respectively equipped with metal patch 9, by changing the length of metal patch 9, just can realize the fine setting to operating frequency passband performance of the present invention like this.
Described distributed inductance 5 can be straight line or curve, when being designed to curve, just further dwindles inner structure size of the present invention.
Fig. 2 and Fig. 3 have provided S parameter amplitude of the present invention (dB) emulation and measurement result relatively, and we are respectively the 3dB constant power output (S that 900MHz and 1800MHz have realized first port one 2 and second port one 3 in centre frequency as can be seen from two figure
21≈ S
31≈ 3dB), on this two centre frequency, the reflection coefficient (S of first input end mouth 10
11) less than-21dB, the isolating coefficient (S of first input end mouth 10 to second input ports 11
41) greater than 25dB, promptly realized well low reflection and high isolation performance.Fig. 4 is the phase difference of first output port and second output port, and we are respectively on 900MHz and the 1800MHz in centre frequency as can be seen from figure, and two output port phase differences are 90 degree ± 1.8 degree, have promptly realized good signal in orthogonal output characteristic.