CN101056094B - Coaxial high-power low-pass filtering-impedance converter - Google Patents

Abstract

The present invention relates to a coaxial big-power low-pass filtering- impedance converter which is characterized in that: the device has a coaxial structure formed by the inner and outer conductor and the insulated supporting plate, and the inner and outer conductor and the medium between then form the high and low impedance transmitting line; the high and low impedance transmitting lines are arranged at intervals, and the an insulated supporting plate is positioned between the inner and outer conductor of the low impedance transmitting line; the adjacent conductors are connected by screws. The advantages of the present invention reside in: a wider working frequency band and a bandwidth>=30% are provided; the device has a performance of lowpass amplitude-frequency and the secondary or more harmonic wave can be restrained effectively in the system; the output lowpass wave of the transmitter can be saved by using the device in the present invention to replace the impedance convertor in the multiway synthesizer and the inserted consumption of the RF output system is reduced, thus, the output system of the transmitter RF is simplified and the cost is also reduced.

Description

Coaxial high-power low-pass filtering-impedance converter

Technical field

The present invention relates to the impedance transformer in the wireless communication technique field, particularly a kind of coaxial high-power low-pass filtering-impedance converter.

Background technology

Impedance transformer is extensive use of in wireless telecommunications transmitter and antenna, is a key technology of designing high-power multichannel RF synthesizer, and impedance transformer is finished two different impedance Z usually _LTo Z _HConversion (Z _L＜Z _H), impedance no-load voltage ratio r=Z _H/ Z _L＞1; In the synthesizer of transmitter n road (n is a positive integer), common Z _H=50 Ω, Z _L=112.5/n; The major function of common impedance transformer is impedance conversion, even it has the low pass width of cloth-frequency characteristic, but its stopband characteristic is relatively poor, therefore also needs to use low pass filter in transmitter usually.

Summary of the invention

The object of the invention provides a kind of coaxial high-power low-pass filtering-impedance converter, is applied in the radio and television transmitter in the multiplexer, makes it possess impedance conversion and two kinds of functions of low pass filtered simultaneously; Impedance no-load voltage ratio r=1.33～10.7, relative bandwidth 〉=30%, power capacity 〉=10KW; Replace impedance transformer in the former synthesizer with this equipment, save the output low pass filter, this simplifies transmitter RF output, inserts loss and reduces, and reduces equipment cost.

In order to realize purpose of the present invention, the present invention adopts technical scheme as follows:

Coaxial high-power low-pass filtering-impedance converter is characterized in that: this equipment is coaxial configuration, is made up of outer conductor, inner wire and insulated supporting plate; Inner and outer conductor and between medium constitute transmission line, comprise high characteristic impedance transmission line and low characteristic impedance transmission line; Eight sections high and low impedance transmission lines forming low-pass filtering-impedance transformer network are distributed in distance; Be provided with insulated supporting plate between the low characteristic impedance transmission line inner and outer conductor, adopt between the adjacent inner conductors to be threaded;

Characteristic impedance span 100～120 Ω of high characteristic impedance transmission line, low characteristic impedance line characteristic impedance span 5～10 Ω, eight joint inner wire length L＜λ g/8 of low-pass filtering-impedance transformer network of forming, wavelength when wherein λ g passes through transmission line for the working frequency range center frequency signal;

With the equivalence of high resistant transmission line is series inductance, the low-resistance transmission line equivalence is a shunt capacitance, under the condition of impedance no-load voltage ratio r=1.33～10.7, relative bandwidth 〉=30%, operating frequency 88～108MHz, power capacity 〉=10KW, the parameters of transmission line structure with reference to the normalized parameter span by calculating.

The invention has the advantages that:

● broad working band, relative bandwidth 〉=30%;

● equipment has the fabulous low pass width of cloth-frequency characteristic, the above harmonic wave of secondary and secondary in the effectively inhibition system;

● replace former multiplexer middle impedance converter with present device, can save transmitter output low pass filter, transmitter RF output system is simplified, and the RF output system is inserted loss and reduced;

● device fabrication is simple, and the present invention is the electric property that guarantees equipment with the machine components size, as long as the machine components ERROR CONTROL is in allowed limits, equipment does not need debugging when producing.

Description of drawings

Fig. 1: coaxial high-power low-pass filtering-impedance converter structure chart

Fig. 2: coaxial high-power low-pass filtering-impedance converter equivalent electric schematic diagram

Fig. 3: FM frequency range No. 8 synthesizer theory diagrams

Fig. 4: FM frequency range 14.06 Ω → 50 Ω low-pass filtering-impedance converter characteristic curves

Embodiment

Below in conjunction with accompanying drawing the present invention is described in further detail:

Coaxial high-power low-pass filtering-impedance converter, structure is seen Fig. 1, it is characterized in that: equipment is coaxial configuration, is made up of outer conductor M1, inner wire T0～T9, insulated supporting plate E1～E4; (air and insulated supporting plate E1～E4) constitute transmission line TL0～TL9 for inner and outer conductor and the medium between them; The TL0 characteristic impedance is Z _L, the TL9 characteristic impedance is Z _H, impedance no-load voltage ratio r=Z _H/ Z _LTL1, TL3, TL5, TL7 characteristic impedance span 100～120 Ω, because its characteristic impedance is higher, we are called the high resistant transmission line; TL2, TL4, TL6, TL8 characteristic impedance span 5～10 Ω, because its characteristic impedance is lower, we are called low-resistance transmission line; TL1～TL8 constitutes impedance conversion and low-pass filter network; The length L of inner wire T1～T8＜λ g/8, wavelength when wherein λ g passes through transmission line for the working frequency range center frequency signal.

With the equivalence of high resistant transmission line is series inductance, and the low-resistance transmission line equivalence is a shunt capacitance, and the equivalent electric schematic diagram of low-pass filtering-impedance transformer network that TL1～TL8 forms as shown in Figure 2; As impedance no-load voltage ratio r=Z _H/ Z _L=1.33～10.7, each device normalized parameter span sees Table one among Fig. 2:

Table one:

L1	C1	L2	C2	L3	C3	L4	C4
								0.4～1.5	0.5～1.5	1.1～4.5	0.35～2	1.2～7.5	0.2～1.5	1.0～11.0	0.05～0.7

We need design No. 8 synthesizers that use in the FM broadcast transmitter, operating frequency range 88～108MHz, and theory diagram is seen Fig. 3, power capacity＞10KW; The function that needs impedance transformer wherein to finish is: with impedance Z _L=14.06 Ω transform to Z _H=50 Ω can surpass 35dB to the inhibition ability of secondary and above harmonic wave simultaneously.We can take following method to realize:

Adopt coaxial type structure shown in Figure 1, it is the 79.4mm copper pipe that outer conductor M1 adopts external diameter, and inner wire T1～T8 adopts copper or aluminium, and insulated supporting plate E1～E4 adopts polytetrafluoroethylmaterial material, its relative dielectric constant ε _r=2.1; Adopt " being threaded " method between the adjacent inner wire, for example T1 and T2, T2 and T3, T3 and T4...... etc. in the drawings.

Line characteristic impedance is selected: TL0 characteristic impedance Z _L=14.06 Ω, TL9 characteristic impedance Z _H=50 Ω for convenience of calculation, all select 110 Ω with high resistant line TL1, TL3, TL5, TL7 characteristic impedance, and 7 Ω are all selected in low-resistance line TL2, TL4, TL6, TL8 characteristic impedance, according to TL0～TL9 characteristic impedance, calculate the diameter of T0～T9.

According to impedance no-load voltage ratio r=Z _H/ Z _L, known quantity such as relative bandwidth calculates or tables look-up and obtain each device normalized parameter of equivalent electric circuit (Fig. 2), carries out anti-normalization again and calculates, and obtains inductance in the circuit, capacitance parameter; Use high resistant transmission line equivalent series inductance at last, low-resistance transmission line equivalent parallel electric capacity calculates the length of T1～T8.T0 and T9 length can be according to the practical structures size Selection.

Because there is distributed capacitance in the high resistant transmission line, there is distributed inductance in low-resistance transmission line, therefore needs to adopt " repeatedly approaching " method to improve design accuracy when designing and calculating.

Fig. 4 is a simulation curves of the present invention, by this curve as can be seen, in working band 88～108MHz, inserts loss＜0.1dB, and reflection loss is better than-30dB, and (＞176MHz) inhibition ability surpasses 40dB with upper frequency to second harmonic.Because its good broadband performance can be operated on the optional frequency of FM frequency range 88～108MHz power capacity＞10KW.

The above the present invention for convenience of description that only gives an actual example, the person of ordinary skill in the field can be according to the impedance no-load voltage ratio, given prototype circuit normalized parameter in relative bandwidth and the table one, carry out " anti-normalization " conversion, present device can be operated in other frequency range, VHF-I wave band for example, the VHF-III wave band, in the UHF television transmitter, if we have determined the characteristic impedance of TL1～TL8, when the impedance no-load voltage ratio, relative bandwidth, when operating frequency changed, the present device overall structure only was embodied in the variation and the equipment overall structure change in size of T1～T8 length; Therefore these aspects all should be included in the above claim.

Claims (1)

1. coaxial high-power low-pass filtering-impedance converter, it is characterized in that: this equipment is coaxial configuration, is made up of outer conductor, inner wire and insulated supporting plate; Inner and outer conductor and between medium constitute transmission line, comprise high characteristic impedance transmission line and low characteristic impedance transmission line; Eight sections high and low impedance transmission lines forming low-pass filtering-impedance transformer network are distributed in distance; Be provided with insulated supporting plate between the low characteristic impedance transmission line inner and outer conductor, adopt between the adjacent inner conductors to be threaded;

Characteristic impedance span 100～120 Ω of high characteristic impedance transmission line, low characteristic impedance line characteristic impedance span 5～10 Ω, eight joint inner wire length L＜λ g/8 of low-pass filtering-impedance transformer network of forming, wavelength when wherein λ g passes through transmission line for the working frequency range center frequency signal;

With the equivalence of high resistant transmission line is series inductance, the low-resistance transmission line equivalence is a shunt capacitance, under the condition of impedance no-load voltage ratio r=1.33～10.7, relative bandwidth 〉=30%, operating frequency 88～108MHz, power capacity 〉=10KW, the parameters of transmission line structure with reference to the normalized parameter span by calculating.

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