System for combining high frequency signals and relevant combiner device

Abstract: In a system for coupling several signals, each signal consisting of a band of high frequencies, comprised e.g. between some hundreds of MHz and some tens of GHz, said system including for each signal at least: a cavity pass-band filter (F₁-F₅), an ancillary circuit (C₁-C₅) for controlling the signal status of said filter, coupling means (12, 23, 34, 45) between the filters, and output and input connectors (Tx1...Tx5;ANT;CR), each cavity is deprived of the zones near to the superior corners that do not significantly cooperate to the filter quality, with a major base body having a section of e.g. rectangular or quadrangular form, and a minor tapered body of substantially trapezoidal form; and the box (60) holding the ancillary circuits shows a width substantially equal to the width of the minor side of the trapezium top.

Description: The present invention concerns a system for coupling several signals each including a band of high frequencies comprised in an interval between some hundreds of MHz and some tens of CHz, said system including for each signal at least: a cavity pass-band filter (Fi) in a cavity having a base (55) and a top part (54), an ancillary circuit (Ci) for controlling the tuning of the filter, coupling means ( 12, 23, 34, 45 ) between the filters, and output and input connectors, ( Tx1, Tx5; ANT, CR). Such system is known from US-A-3 124 768. Usually the telecommunication field presents the problem of combining two or more signals included in different frequency bands on a sole carrier means, e.g. a cable. The signals combination must be made with the minimum possible space requirement by means of a device including, in addition to the channel filters, also the auxiliary circuits that have the aim to survey the characteristics of the signals to be combined, and to signal the status of filters to the control circuits to adapt them, e.g. by means of motors that control them, in the case in which the tuning of some filters must be made automatically. For better fixing the ideas, the simplified scheme of Figure 1A shows the frequency bands B1, B2,....Bn of the signals to be combined, and the scheme of Figure 1B represents the blocks of the circuit to be made. F1, F2,... Fn are filters through which the frequency bands B1, B2,... Bn to be combined pass; C1, C2 ...., Cn indicate the ancillary circuits associated to each filter. Figure 2 represents the schematic front view of a combining circuit made up using the known technics for combining two or more signals each thereof having a band Bi. Each filter Fi is represented by a parallelepiped-shaped box (generally a resonant cavity) surmounted by the box Ci holding the ancillary circuits. At the output of each filter it is provided a coupling line, that is joined externally to two connectors Sa and Sb. The output Sb of each filter is joined to the input Sa of the following filter. The connector Sa of the first filter is closed on a reactive load (CR) that, without dissipating power, causes the signal coming from the input of each filter to be transmitted towards the input connector of the following filter. In this manner on the connector Sb of the first filter F1 are assembled the signals B1,B2....,Bi...Bn coming from the input of all filters F1,F2,...Fn. CO' indicates the connection cable between C1 and F1 (Figure 2b). The described circuit solves the problem in question, but shows also a series of drawbacks, among which are mentioned here the sole drawbacks related to excessive space requirements, difficulty of circuit connections among the filter couples, etc.. A first scope of the invention is to provide a system that does not show the drawbacks of the known Art and has limited total space requirements, low losses, but also a great efficiency, e.g. in fulfilling the connections among filters, and approaching the same filters among one another. These and other scopes are obtained by the system according to the invention that is characterized in that each cavity (CRi) does not include the zones near to the superior corners (52-53) that do not significantly contribute to the filter quality, so that each cavity (CRi) includes a major base body (55) having a rectangular or quadrangular section and a minor tapered body (52-53) substantially in trapezoidal form; and in that a box (60) holding the ancillary circuits (Ci) has a width substantially equal to the width of the minor side of the trapezium top (54). Further characteristics of the system and related implementation devices are referred to in the other claims. The circuit used in the invention is based on the observation that a portion of the pass-band filters, being near to the corners, does not provide a significant contribution to the quality of the same filters and therefore it can be eliminated. Another observation on which the system according to the invention is based concerns the relationship or ratio between the dimensions of pass-band filters and the dimensions of ancillary circuits associated therewith. As the width of ancillary circuits is included in the order e.g. of a third with respect to the width of filters, the whole space included between the same ancillary circuits is wasted and can be completely used by rotating the adjacent filters e.g. of 180° degrees. For getting the maximum exploitation of spaces and for minimizing the length of the connection circuit, the pass-band filters were deprived of the corners adjacent to connectors Sa and Sb. In fact according to what said above, these edges are substantially unused. The different features and advantages of the invention shall appear better in the detailed description of the embodiments represented in the annexed drawings, in which: Figures 3a, 3b, and 3c represent schematical and partial views of the structural configuration of a filter according to the invention, said views being respectively rear views, i.e posterior (Figure 3a), lateral (Figure 3b) and front or anterior views (Figure 3c) respectively; Figure 4A is a section view of Figure 3a or better a section view made by a plane having as path the line A-A in Figure 3c; Figure 4B is a section view according to the line B-B of Figure 4A; Figure 5 is a schematic plan view of a combiner according to the invention, including five single filters indicated from 1 to 5 in the Figures 3a-c and 4A-4B, each filter being rotated of 180° with respect to the preceding and the following ones, each couple of filters being provided with its connection bridges 1-2, 2-3, 3-4 and 4-5 respectively; and Figure 6 is a schematic and partial view of said bridge along the line Y-Y of Figure 5. According to a first feature of the invention, each filter Fi has now (Figures 3a-3c and 4B) a configuration countersunk in the superior part that, being engaged and resting on two lateral plane and parallel walls 50-51, is limited by a preferably trapezoidal portion including the two sloped sides 52 and 53 (with respect to A-A) and the top part 54, parallel but much smaller than the bottom or base 55. Preferably the slope of 52-53 is 45°; on the higher sides 52-53 is now formed the box 60 holding an ancillary circuit Ci and having a width 62 substantially equal to the width of said top part 54, and a height H. According to another feature of the invention, the now tapered configuration (trapezoidal or equivalent triangular shape) of the top part 52-53-54 of each filter Fi and also the width 62 of ancillary circuits Ci substantially equal to the width of said top part 54 allow an advantageously critical juxtaposition (approach) of the filters (and of related ancillary circuits). As it can be better seen from Figure 5, in which for illustrative clarity's sake it is represented a typical (but not limitative) combiner made up of five filters F1, F2, F3, F4 and F5 (each with related ancillary circuits indicated with C1 to C5), the filter F2 is turned of 180° with respect to the preceding filter F1 in the sense that F1 (remained e.g. in the position of Figure 3c) has the side 51 approached to the side 61 of C2 while the side 50 of the filter F2 is near to the side 60 of C1. According to another feature of the invention, these following overturnings shall allow to position the sloped sides 52 of a filter, e.g. F1, directly near to the side 53 of the following filter. Now it is extremely advantageous and simple to make the coupling between the following filters e.g. between F1 and F2, applying a bridge 1-2 inserted in a box 12' e.g. of rectangular shape, whose major side "l" is preferably orthogonal to the sloped flanked sides 52 of F1 and 53 of F2. In this manner it is obtained not only a great reduction of the overall dimensions for the combined effects of: the configuration e.g. trapezoidal in form of each filter; the 180°-overturning in succession of the same filters; the creation of a border line 52 of F1 very near to 53 of F2 and so on; but additionally also an easy, reliable and no dispersive connection between the filters by the bridges or U-bridges 1-2, 2-3, 3-4, 4-5 that connect the two sloped flanked sides of each filter couple. A typical connection bridge is represented in Figure 6 and includes an external body 71, a first internal (horizontal) lead 72, sleeves 73 and 77 e.g. made of PTFE (polytetrafluorethylene), two other vertical leads (not represented), a threaded pin 75, clips 74, caps 78 and pins 79. Even if the structure of the coaxial U-bridge of Figure 6 cannot be really included in the present invention, as the embodiment of the invention can be also carried out by replacing this U-bridge with bridges of other type, said U-bridge 1-2 or 4-5 was described for showing clearly another advantageous feature of the invention, that is represented in the Figures 4A, 4B and 5. The Figure 5 shows that an U-bridge, e.g. 1-2, between the filters F1 and F2, forms a bridge between the end 81 of the connection line 101 of the filter F1 and the end 82 of the line 102 in the filter F2. The Figure 4B shows better as a line e.g. 101 joins the antenna connector ANT with the internal connector of the cavity CR1. It has been found advantageous to adjust at the best the length of each of said lines 101...105 by conforming some as a curved plate (in circular, elliptic sector forms, etc.) and adjusting its distance from the wall PA of the cavity CR1 by an external screw 85, that approaching or moving away (for a very short distance) the curved lamina, e.g. 101, from the wall PA of the cavity CR1, optimizes its coupling. The Figures 4A and 4B represent the more advantageous embodiment of the invention, in which as resonant cavity CR1 it is used a resonator, whose tuning is adjusted by two dielectric elements, the first one formed as female element Df and the second one as male element Dm, that is moved within Df and for this aim it is supported by two concentrical guides GU and by a central screw or shaft AL driven preferably by a motor MOT. In this manner changing the coupling, that is the penetration of Dm into Df, it is possible to tune perfectly the cavity CR1 and then the related filter F1 within a wide frequency range. The embodiment of the double dielectric resonator with penetration controlled by manual screw or motor is described in the contemporaneous European Patent Publication 0492304. In a similar manner the second contemporaneous European publication 0492302 (US Patent 5311157) of the Applicant describes the embodiment of resonant cavity filters F1-Fn (preferably with double dielectric), each thereof including two filtering sections, a pass-band filter F1A for the high frequency signal (e.g. from 700 MHz to 12 GHz), and a pass-band filter F2B for the low frequency control signal (e.g. tuning signal) (from 0 to 300 MHz). Advantageously F1A is coupled by an inductance to the cavity for the high frequency signal and F2B is made up by a printed circuit CSR housed in a niche NI formed in the wall PA of the cavity CR1. As it can be noticed easily, the low frequency signal outgoing from the low-pass filter section F2B controls the motor MOT, that by moving the male dielectric Dm and adjusting its penetration "p" in the female dielectric Df adjusts the tuning of the filter Fi. The remote controlled motor system has actually a wide and very useful application in telecommunication for mobile radio sets. Also the description of the second contemporaneous patent application of the Applicant relates to its embodiment of a low-pass filter section with printed circuit CST inserted in the niche NI, and of the pass-band filter section coupled with inductance and without capacitor. The operation of the preferred automatic system according to the invention can be resumed as follows. The filter F1 (therefore any other filter Fi of Figure 5) has its cavity CR1 provided with a first support SU for the motor MOT on one side and with a support plate 75 for the box 60 of ancillary circuits C1, said plate acting also as cover for CR1. (Figure 4A). Therefore the plate 75 has the two functions of cover for the filter F1 and support for the box 60. With reference to the Figures 3 the signal that, through the filter F1 must be sent to the antenna ANT together with the signals coming from the other filters F2-Fn, is sent to the connector 6 (Figure 3b) that forms the input of the box 60. After that a smaller amount of the signal has been extracted to give to the auxiliary circuits Ci information on its status, the status of the same signal is sent through the output connector 7 and the cable 8 (Figure 3a) to the input connector 9 of the filter Fi (see also Figure 3b). A part of the signal is reflected by said filter and reaches the box 60 and supplies thereto information on the filter tuning status through the cable 8 and the connector 7. The package of information collected by the box 60 shall be processed by the ancillary circuits Ci hold in 60 and shall be used for sending the controls to the motor MOT that automatically tunes the filter Fi (changing the penetration of the male dielectric Dm into the female dielectric Df).

Claims: A system for coupling several signals each including a band of high frequencies comprised in an interval between some hundreds of MHz and some tens of GHz, said system including for each signal at least: a cavity pass-band filter (Fi) in a cavity (CRi) having a base (55) and a top part (54), an ancillary circuit (Ci) for controlling the tuning of the filter, coupling means (12,23,34,45) between the filters, and output and input connectors, (Tx, Tx5; ANT,CR) characterized in that each cavity (CRi) does not include the zones near to the superior corners (52-53) that do not significantly contribute to the filter quality, so that each cavity (CRi) includes a major base body (55) having a rectangular or quadrangular section, and a minor tapered body (52-53) substantially trapezoidal in form; and in that a box (60) holding the ancillary circuits (Ci) has a width substantially equal to the width of the minor side of the trapezium top (54). The system according to claim 1, characterized in that the assemblies of cavities and ancillary circuits are shaped in "bottle" form, are 180°-overturned with one another, the neck of a bottle represented by the box (60) of ancillary circuits (Ci) being located adjacent and fitting together with the side of the major body (50-51) of the preceding and following cavity. The system according to claim 1, in which the tapering sides (52-53) of the minor trapezoidal body of the cavity top part (54) are sloped of about 45°. The system according to one of the claims from 1 to 3, characterized in that the coupling means (12,23,34,45) in form of bridge for the connection of the signals of near filter couples is placed on the sloped sides (52-53) adjacent with one another of two overturned near cavities, said bridge (12,23 etc.) being preferably oriented at 90° with respect to the couple of said sloped sides (52-53). The system according to claim 4, characterized in that each bridge (12, 23 ETC.) connects two curved laminae (101-102; 103 -104 etc.), each thereof being in the inside of a cavity (Ci), the lamina curvature defining and adjusting the length of same laminae while the distance between the faced surfaces of the cavity internal wall (PA) and of the lamina opposing wall is adjusted using a dielectric screw (85) crossing said cavity wall. The system according to preceding claims, characterized in that the cavities contain two compenetrating dielectric elements (DF, DM), whose compenetration is manually or automatically controlled to regulate the cavity resonance frequency. The system according to claim 6, in which in a wall (50) of the cavity (Ci) a niche (NI) is formed to house low-pass filter (CST) in printed circuit form whose signal acts on the compenetration of the dielectric elements (DF, DM).

Inventors: CAVALIERI D ORO ENZO, TANSINI VITTORIO, CAVALIERI D'ORO, ENZO, TANSINI, VITTORIO
Applicants: FOR E M S P A, FOR.E.M. S.P.A.
Application year: 1991
Main classification: H01P1
IPC codes: H01P1, H01P7