CN2123145U

CN2123145U - Wide-band lumped parameter 90 deg. directional coupler

Info

Publication number: CN2123145U
Application number: CN 91229271
Authority: CN
Inventors: 周强
Original assignee: SHIJIAZHUANG INST NO 54 MINISTRY OF MACHINE BUILDING AND ELECTRONIC INDUSTRY; Beijing Institute of Technology BIT
Current assignee: SHIJIAZHUANG INST NO 54 MINISTRY OF MACHINE BUILDING AND ELECTRONIC INDUSTRY; Beijing Institute of Technology BIT
Priority date: 1991-11-29
Filing date: 1991-11-29
Publication date: 1992-11-25

Abstract

The utility model belongs to the impedance network technical field. According to the problem of too narrow frequency band of the present lumped parameter 90 deg. directional coupler, the utility model utilizes the parity module theory and discloses a novel circuit. By optimum design of the component parameter in the circuit t, the utility model can produce a lumped parameter 90 deg. directional coupler with bandwidth close to the frequent distance. The circuit only comprises a unideal transformer and six electric capacitors. The structure is simple and compact, in favor of integration and batch production. The utility model is widely used in the technical fields of radar, communication, measurement, electronic reconnaissance, etc.

Description

Wide-band lumped parameter 90 deg. directional coupler

The utility model belongs to the impedance network technical field.

Directional coupler is one of most widely used passive device in the microwave technology.In microwave band, the directional coupler of 90 ° (orthogonal types) generally adopts the form of single-unit or the quarter-wave parallel coupled line structure of more piece.Usually be referred to as the directional coupler of distributed constant.Wherein the directional coupler of single-unit generally has the bandwidth of an octave.The form of more piece can obtain wideer frequency band.But the size of the directional coupler of distributed constant is relevant with frequency, when the size that is used for lower frequency (for example tens to the hundreds of megahertz) coupler seems excessive.

The element of employing lumped parameter can dwindle the size of coupler greatly and be easy to make becomes integrated circuit modules.Document Chen Y.Ho: " Design of Lumped Quadrature Couplers ", Mlcrowave J., Sept., 1979., provided a kind of 90 ° of directional couplers forming by inductance capacitor element among the pp.67-70.But sort circuit can only provide very narrow frequency bandwidth (less than 10%), thereby has limited its application greatly.The band spread that how to make 90 ° of directional couplers of lumped parameter is very significant.

The purpose of this utility model be design a kind of can near or 90 ° of (orthogonal type) directional couplers of lumped parameter with octave bandwidth.

In order to help illustrating enforcement of the present utility model, provide description of drawings earlier:

The several 90 ° of directional coupler electrical schematic diagrams of Fig. 1 wide band lumped parameter

The strange mould equivalent electric circuit of the directional coupler of Fig. 2 Fig. 1

The even mould equivalent electric circuit of the directional coupler of Fig. 3 Fig. 1

The installation diagram of the directional coupler of Fig. 4 Fig. 1

Embodiment of the present utility model as shown in Figure 1. It is by 6 electric capacity and 1 four port devices that non-ideal transformer forms. In the accompanying drawing 1, element (1), (2), (3), (4) they are four input and output terminals, they consist of respectively four ports of directional coupler with ground. Any one port can be as input port. Port on its diagonal angle is isolated port. Two other port is the output port of coupler, and one of them is called straight-through port, and another is called coupling port. For example, as input, then port 3 is isolated port with port one, and port 2 is straight-through port, and port 4 is coupling port.

(5) in the accompanying drawing 1-(10) are capacity cell, wherein (5), the appearance value of (6) is Co, they are connected across respectively terminal (1) and (4), on (2) and (3). (7), (8), (9), the appearance value of (10) is C1, respectively Be connected across between four terminals and the ground.

Element in the accompanying drawing 1 (11) is a nonideal transformer.So-called non-ideal transformer is meant a kind of double-wound coil, and we select the number of turn of two windings identical here, and it has self-induction L and mutual inductance M, and L＞M.Stain is represented end of the same name in the accompanying drawing 1.

Capacitor C o and C1, transformer self-induction L mutual inductance M will determine with the requirement of centre frequency, bandwidth and the degree of coupling.

This network structurally has two planes of symmetry.According to network theory, if network mates entirely, then this four port network necessarily has directionality, and must be 90 ° of orthogonal type directional couplers.

According to microwave network theory, the bandwidth of 90 ° of directional couplers of the parallel lines form of single-unit has the frequency band of broad (an about octave) again.Learn that with even odd mode theory analysis its strange mould and even moding circuit are one section are called odd mode impedance and even mode impedance for the characteristic impedance of these two line segments of quarter-wave transmission line section (being equivalent to 90 ° of phase shifts) on centre frequency.Can imitate such distributed constant directional coupler with circuit of the present invention so.The circuit of accompanying drawing 1 can be represented its strange mould and even moding circuit by accompanying drawing 2 and accompanying drawing 3 respectively.They are the pi network of a lamped element.Choose the lamped element parameter value, this pi network can equivalence be 90 ° of phase shifters with certain characteristic impedance.If choose component parameters, make that its characteristic impedance of pi network of accompanying drawing 2 and accompanying drawing 3 is identical with even mode impedance with above-mentioned single-unit parallel lines coupler odd mode impedance respectively, like this, the circuit of accompanying drawing 1 just can be similar to the parallel lines directional coupler of regarding distributed constant as, and has similarly (being slightly smaller than) bandwidth.

Employing can make frequency band wideer (to an octave) to the way of component value optimization.The strange moding circuit of Fig. 2, wherein (12) are the poor of non-ideal transformer (11) self-induction L and mutual inductance M, i.e. Lo=L-M, (13), (16) are equal to 2Co, and (14), (15) are equal to C1.Even moding circuit shown in Figure 3, wherein (17) are the self-induction L and the mutual inductance M sum of non-ideal transformer (11), i.e. Le=L+M, (18), (19) are equal to C1.

The A parameter matrix of strange mould and even moding circuit is respectively:

Can obtain the reflection coefficient and the transmission coefficient of Qi Mo and even moding circuit thus:

Γo＝（ (A11＋A12／ZO－A21－A22)/(A11＋A12／ZO－A21＋A22) ）odd

To＝（ 2/(A ₁₁＋A ₁₂／ZO＋A ₁₂＋A ₂₂) ）odd

Γe＝（ (A ₁₁＋A ₁₂／ZO－A ₂₁－A ₂₂)/(A ₁₁＋A ₁₂／ZO＋A ₂₁＋A ₂₂) ）even

Te＝（ 2/(A ₁₁＋A ₁₂／ZO＋A ₂₁＋A ₂₂) ）even

Can obtain the S parameter of directional coupler by network theory

s ₁₁＝（Γe＋Γo）／2

s ₂₁＝（Γe－Γo）／2

s ₃₁＝（Γe－Γo）／2

s ₄₁＝（Γe＋Γo）／2

With element Co, the L of C1 and transformer, M(or Lo Le) as optimizing variable, are optimized design to following desired value in given frequency band:

s ₁₁＝0

s ₃₁＝0

s ₂₁＝

s ₄₁＝K

This directional coupler can be designed to have an octave or narrower frequency band.K is the degree of coupling in the following formula, represents with decibel:

C（dB）＝201og?k

Say that in principle this directional coupler can be designed to any degree of coupling.For close coupling, for example in 3dB even the 3dB, also be easier to realize.

The utlity model has good effect.90 ° of directional couplers that it has adopted lamped element to constitute to have octave bandwidth have dwindled the volume when this type of device is used in the microwave frequency low side greatly, and have been easy to integrated production.Can be widely used in technical fields such as radar, communication, measurement and electronic reconnaissance.

Embodiment 1

Produce the 3dB90 ° of directional coupler test piece of 100-200MHz.Component parameters is chosen as

L＝76mμH M＝56mμH Co＝5.6pF C1＝18pF

Measurement result is:

Straight-through :-3.5dB ± 1dB

Coupling :-3.5dB ± 1dB

Isolate:＞15dB

Reflection loss:＞15dB

Embodiment 2

Produce the 3dB90 ° of directional coupler test piece of 200-400MHz.Component parameters is chosen as

L＝38mμH M＝28mμH Co＝2.7pF C1＝9.6pF

Measurement result is:

Straight-through :-3.1dB ± 0.5dB

Coupling :-3.1dB ± 0.5dB

Isolate:＞15dB

Reflection loss:＞15dB

Claims

1, the several 90 ° of directional couplers of a kind of wide band lumped parameter, it is characterized in that it is by 6 capacitors and 1 four port devices that non-ideal transformer is formed, terminal (1) (2) (3) (4) constitutes its four ports with ground respectively, capacitor (7) (8) (9) (10) one end is continuous with corresponding terminal (1) (2) (4) (3) respectively, and capacitor (5) (6) is connected across respectively on terminal (1) (4) and (2) (3).

2, device according to claim 1 is characterized in that its capacitor (5) (6) has identical capacitance Co, and capacitor (7) (8) (9) (10) has identical capacitance C1, Co, and the C1 value is determined by optimal design.

3, device according to claim 1 is characterized in that the no-load voltage ratio n=1 of its non-ideal transformer (11) and has self-induction L and mutual inductance M and L＞M, and L and M value are determined by optimal design.