GB2285540A - System to combine high frequency signals - Google Patents

Description

2285540

DESCRIPTION

Field of the invention

The present invention refers to a system to combine (2n) high frequency signals (modulated) in one composite signal having a wide band (BW) on only one line of reduced length.

In particular the invention concerns a system to combine 2n signals of high frequency (microwave) coming from different sources, for instance from 2n transmitters, by coupling, through band-pass filters, each source with a unique common line (L) connected, for example, to a unique transmission line.

In one specific embodement this system comprises a network involving at least: 2n transmitters (Tna, Tnb), 2n filters (Fna, Fnb), a comon line (L) and n structures (Sn) coupling filter and transmitter pairs to said line (L), on its turn, connected to an antenna (Ant).

Prior Art

Systems and devices for the combination of several high frequency signals (each having a different frequency band) which come from several transmitters (Tx) and are to be transferred, via filters (F), to an unique line connected to a unique antenna, are abundantly described in the current litterature.

The problem has however assumed a capital importance because of the recent developments of sophisticated technologies related for instance to the mobile telephony in particular to GSM and PM. The Applicant has contributed to such developments with system and devices forming the -Isubject-matter of international patents among which we mention the US Patents NI 5.206.612 and NI 5.243.305 and the European Patent Publications NI 0492.302, NI 0492304 and NI 0551618 (Sia).

This last Pat. Publ. NI 0551618 refers to the combination of more signals from more trnsmitters operating in the field of themicrowaves comprised between hundreds MHz and tens GHz, in particular to the radio mobile tranmitter basic stations, in which the combination of the n filters coupling the signals from n tranmitters comprises n/2 pairs of filters which are inductively coupled and positioned on both sides of the common line L formed of n portions having /2 length where corresponds to the length of the combined band (BW) central frequency.

Each line portion is divided in two half-pieces SPI-SP2, SP3-SP4 which are parallel disposed and coupled each, with a filter (F1, F2 etc.). Typically each filter pair (F1- F2, Fn-1 - Fn) consists of two resonant cavities which are open an at least a portion thereof and are disposed on each side of a central plate (PIA) consisting of a core (Nu) and of two outer major faces (F01, F02) each forming the cavity wall.

Preferably the core (Nu) houses the means of control electromagnetic coupling organ which can be a curved lamina (R2), missing of an said central comon plate introducing a dielectric resonator, in each cavity.

Independently from this embodiment, the problem of combining more modulated signals of different frequencies assumes to day critical features in the sense that it is necessary to combine an always increasing number of modulated signals and thus to form a composite signal having a maximal band width (BW) operating on always higher frequencies. For this maximization of (BW) it is however not possible to increase the line length above given limits.

Object of the present invention is a system of the type indicated in the introduction of the description and in the preamble of the main claim, which allows the maximization of the widening of the utilizable frequencies band and the minimization of the circuit length. This and other objects are reached with a system characterized in that the common line is uninterrupted on its whole length and shows coupling means in n points PI, P2 --- Pi--Pn in which the coupling of the n pairs of filters with the line is brought about with the aid of high impedance loops LOla, LOlb etc. each loop having a (k /4 length ( (- corresponding to the total band central frequency), and in which system the distances on the line (L) of successive coupling points Pi - Pi +1 can be also not-uniform but are always multiple(s) of half wave length.

An other object of the invention is to provide a system to incorporate each pair of facing filters Fla -Flb etc. and each pair of relevantloops (LOi) of coupling to the central uninterrupted line L, within single means or structures Si centered in points Pi ununiformly spaced in respect to the means in the preceding point Pi-l and in the followinf point Pi+I so to minimize the line total length and to maximize the band widening (BW).

According to an important feature of the invention the disuniform distances between pairs of points Pi - Pi+l are obtained by decreasing the distances between the point pairs of the type PI-P2; P3-P4; Pn-l -Pn and by increasing the distances between couples of the type P2-P3, P4-P5, --Pn-2-Pn-1.

In one advantageous embodiment, all the means or structures from S1 to Sn are modular (equal to each other) and the dissimetry between the distances of the alternated pairs of the coupling points is obtained by simply rotating on 1801 the structures of, for instances, pair S2, S4--Sn over to the impair structures.

In one particularly advantageous embodiment of the invention each structure Si comprises: a complex element which forms two resonant cavities separated by a common wall carrying, on each of its two faces, a stationary dielectric female resonator, each cavity being open at the end opposite to the end of the relevant face of the common wall; two bodies each penetrating in a cavity through said open wall and having a mobile resonator; a cap closing the initially open wall and a motor to displace the male resonator; and a device carrying on one face the line coupling loops having an end connected to said line and the other end being earthed, and, on the other face, different coupling organs which provide to couple cavities of near structures and of distant structures, as well as to render continuous and uninterrupted the line on all its extension now minimized and to determine disuniform distances.

The various scopes and advantages of the invention will more clearly appear from the description of the non-limitative embodiment shown in the accompanying drawing in which:

Figure 1 is a typical scheme of the Prior Art;

Figure 2 is a scheme according to the invention; Figure 3 shows a cross-section of an exploded structure Si; Figure 3A shows the compacted structure of said Fig. 3; Figure 4 is a plant view of a system comprising the four structures from Sl to S4 of Fig. 2 with Sl-S2 and S3-S4 at a mutual distance /2 but with S2 at a distance tl\ from S3; and Figure 5 shows said sections Sl-S4 in the cross section of line Q-Q on Fig.4, Fig. 5A being an exploded representation of the continuous, uninterrupted line having a lenght minimized according to the invention.

Just to fix ideas, Fig. 1 shows a conventional circuit to combine in one antenna several signals of diferent frequencies. The circuit consists of the following parts:

a) a line L starting from an end CA of an open circuit and terminating to the other end Ant connected to the transmission antenna Ant. In n points line L is divided in two paths Pis-Qla-Pld, Pls-Qlb-Pld, P2s-Q2b-P2d.... Pns-Qna-Pnd, Pns, Qnb-Pnd; b) 2 n pairs of filters Fla, Flb, F2a, F2b... Fna, Fnb inductively coupled to the pairs of paths Qia, Qib in which the main line is subdivided, for instance through the inductances Ii'a-Iib; the filters have inputs Tla, Tlb, T2a, T2b... Tna, Tnb to which can be connectet the transmitters Txn (not shown) the signals of which must be combined and sent to antenna Ant.

The (inductive) coupling points Qla, Qlb, Q2a, Q2b..Qna, Qnb must have distances from the open circuit CA, which are unpair multiples of a wave length Quarter m A /4 (where m is an unpair number and rk is the wave length corresponding to the central frequency of the frequency band occupied by transmitters Txn). In Fig. 1 the distance X1 between pointsI and 2 is (Q4 to render the filters input coupling and thus their band width as constant as possible. Consequently the paths Y=Qla-Pld-P2s-Q2a (distance between points 2 and 3), Y'=Qlb-Pid-P2s-Q2b (distance between points 21 and 3') etc. must have a length of a whole multiple of half wave length (mi /2, where mi is a whole number).

In order to impart to the system the maximum band width (BW mx) the path Y and Y1 must have the possibly lower length. This implies that the distance between successive filters Fla-F2a respectively Fib-F2b be equal or very near to a wave length half A /2. This goal is the easier reached, the higher is i.e. the lower is the band BW central frequency. For instance the filters of the mobile telephone system GSM in the band of 935-960 MHz can be at a distance of only one half wave length even by using the above mentioned method ( see EP NO 0551618, Applicant's reference F10 Siamesi).

When however said central frequency is high, as for instance in the new system so called DCS 1800 (PCN) with transmitters in the band of 18051880 MHz, the above described method shows the disantvage of needing high and difficultly tollerable line lengths whereby they do not allow the minimization of adjacent transmitters distance..

As anticipated the first object of the present invention is to provide an effective solution to the problem of the minimization of the line length and of the maximization of the band width BW. The circuit of Fig. 2 shows the system of the invention. To make easer its comprehension the particularly simple system is shown with 8 filters Fla, Flb... F4a, F4b, contained, two by two, on four structures S1, S2, S3 and each housing a portion "lill of line L in the points Pl-P4 of which are connected, according to the invention two high impedance conductor tracts Cla-Pl, Clb-Pl... C4a-P4, C4b-P4 of a A14 length.

Characteristically said tracts are, each, earthed (Er) at the other end, i.e. at the end remote over the points Pl, P2, P3, P4. Preferably said tracts are loops LO la LO IbI LO 2a' LO 2b etc. having an end 70-70' connected to a conductor piece "la" on the line L, and the other end C lal C lb etc. to EARTH Er. It has been found that with this coupling type it is possible to reach the advantage that points Pl-P4 can be at the center of line tracts 'Ili" passing through the structures S1, S2, S3, S4 whereby the line portion Pl-P2 can have a length other than that of tract P2-P3, as shown in Fig. 2.

Therefore the distance between points Pl-P2-, P3-P4.. Pnl- Pn can be different from that between points P2-P3, P4-P5 etc. However if the structures S2 and S4 were 1800 turned in the sheet plane, the distance PIP2, P2-P3, P3-P4 would be all equal. As it will be described with reference to an application example, the tracts Pl-P2 and P3-P4 (P5-P6 etc.) in Fig. 2 have a half wave length ( A/2) while the tracts P3-P4 have one wave length ().

This solution is not possible with the circuit of Fig. 1 since the tract Ql-Pld-P2s-Q2a is longer than the tract Pl-P2 of Fig. 2 because of the branching that the line couples Pls-Qla-Pld, Pls-Qlb-Plb.... Pns-Qna-Pnd must have. One particularly advantageous (and thus prefered) embodiment of one coupling unit according to the invention f. i. Sl (Figures 3 and 3A) comprises an element CR 1 which forms two cavities CT1a, CT1b and is generally a cylindrical body (in alloy of A1 or other metals) with an intermediate wall PS1, two openings at the transversal ends PA1a, PA1b (remote and opposite to the respective faces 50-50' of the separation wall PS1) and a fenster Fin which is in correspondence to the center of the intermediate wall PS1 and extends on two portions 52-52' of the upper longitudinal walls 51-511.

The fenster Fin houses a plate PIA carrying, on the lower face, the loops L01a, L01b of the coupling to the line L, and the conductor piece "lab" to be soldered to the loop ends 7070', and, on the upper face, the stems of screws, studs or pins 28, 29-29', 30-301 to engage mechanically and electrically the small bridges CAVP 1-21 CAP 3-4 acting as couplers of cavities Ma-CT2a (CT1b-CT2b) of near structures S1-S2.

Each small bridge CAVP is arranged centrally on the plate PIA, has a minimum length and extend thus only on one single plate. To couple the cavities CT 2a-CT 3a of distant structures, long bridges as CAVG 2-3 are utilized which are bridge grafted on the internal ends EIV EI 2 of two successive plates PIA 21 PIA 3 Inside the short bridges CAVP 1-2 and CAVP 3-4 horse backing two near structures SI-S2 and S3-S4, there are line pieces 1 1-2 and 1 3-4 enough short just to step over near structure cavities. These line pieces connect, by means of screws 29-29', 39-39' the very line pieces 41, 42, 43 and create thus the connection between P1-P2, P3-P4 of reduced length /2 whereas the long bridges (only one CAVG 2-3 is shown in figures 4 and 5 concerning the case of figure 2 having only four filter pairs and four structures S1... S4 in the points P1... P4) have a major length such as to bridge successive plates PIA 2 and PIA3 associated to distant structures.

Fig. 5A shows the construction of the uninterrrupted line L of length 1 formed now of pieces of conductive strips 41, 42, 43 and 44 external to the bridges, and of the line pieces 1 1-2 and 1 3-4 internal to the short bridges, as well of the line tract 1 2-3 internal to the long bridge CAG 2-3 Preferably the line short pieces 1 1-2 and 1 3-4 inside the small bridges CAVP 1-21 CAVP 3-4 as well as line long piece 1 2-3 inside the big bridge CAVG 2-3 are of the coaxial type whereas the external pieces 41, 42, 43 and 44 are simple straps of copper alloy.

Each external piece 41, 42, 43 and 44 can be imaginated as formed of the tract Lpo between pin 30 and P1, and of tract Lp 1 between P1 and stud C 29, followed by the short coaxial line 1 1-2 between 29 and 29' and the plaque line 42 consisting of two imaginary pieces LP2, LP3 and so on.

Each line piece "li", for ex. between 90 and 91 inside each structure Si comprises a short tract 41, 42, 43 of strap conductor outside the short bridge CAVP and the half of the coaxial line tract inside CAVP. As to the assembly, it can easely be figured out that each plate PIA (secured through screws 44 to the walls 51-51' of cavities CT1a, CT1b) carries, besides the holes for the passage of said screws 14-141, also the holes to house dielectric washers (difficult to see from the drawings) which support the projecting pins 29-29' etc. on which are grafted the small bridges CAVP 1-2' CAVP 3-4 and projecting pins 31-31' to fix the long bridge CAG 23' On the first terminal plate PIA 1 is also secured the short circuit plate PCC (60) whereas on the last terminal plate PIA 4 is fixed the strap -g- of input to the antenna IN-Ant 1161). The pins 31-311 to secure the long bridge CAVG 2-3 and the pins for the short bridges are made of conductive material. Figures 3A, 4 and 5 show resonant cavities CTia and CTib each with two dielectric bodies which have a compenetration (and thus a tuning) controlled by a remotely controlled motor, according to EP N11 0492304 and US Pat. NI 5.206.612.

This cavity type finds here a particularly happy application of simple realization. Indeed, according to a feature of the invention, to each face 50-50' of the partition wall PS (see figures 3 and 3A) we associate a stationary support 12a, 12b of the female (stationary) dielectric resonator DFla, DFIb.

Through each open wall PAla (PAlb) we insert a control device REGa (REGb) consisting of the male mobile dielectric resonator DMa and of the relevant support 13a protruding from the base SUa which is fixed to the wall CHa and is moved for-and back-ward by the electric motor Ma remotely controlled by the control organ ORa whic receives, from the remote central station, signals able to control the penetration of said male dielectric element DMa inside said stationary dielectric resonator DFa in order to obtain the requested tuning.

The space between the distant sections S2-S3, S4-S5 can be used to house other complementary devices 11not shown). The wall CHa closes hermetically the aperture PAla of cavity Ma as it is fixed at the end of the cylindrical wall 51 by means of screws 16-161.

While Fig. 3 shows the structure S1 with the two cavities Ma, CT1b in exploded form, Figure 3A shows S1 at the end of the assembly i.e. in 10compacted form with the control devices REGa and REGb assembled to the cavity forming body WC1.

For the working of the compenetrating dielectrics cavities reference is made to EP NO 0492304 and US Pat. NI 5206612 and for their remote control reference is made to EP NI 0492302, the specifications of said patents being considered as herein incorporated.

Claims (1)

1) System to combine 2n (modulated) high frequency signals, each having its band width, on a common line (L) coupled trough 2n band-pass filters to the 2n sources of said signals, characterized in that to maximize the band width (SW) formed by the 2n signals bands, by minimizing the length (1) of the common line (L), this last is a line uninterrupted on its whole length (1) and shows n means to couple the n filters pairs, disposed in points P1-P2-Pn on said line, each coupling means comprising two high impedance loops, each loop having a /4 length (where (k is the wave length corresponding to the central frequency of the combined band BW) and being earthed at the end (Er) remote over the end (Ec) arriving to the point 10i) of connection to the line (L), the distances between the successive pairs of the n points PI... Pn being dissimetric but remaining multiple of half wave length.

2) System according to claim 1, characterized in that the coupling points pairs PI-P2, P3-P4... Pn-2- Pn-1 have mutual reduced distances which are lower than the distances between the couples P2-P3, P4-P5... Pn-I-Pn.

12- 3) System according to the claim 2, characterized in that the the short distances between couples P1-P2, P3-P4... Pn-1 - Pn are equal to /2 whereas the long distances between P2-P3, P4-P5 etc. are equal to 4) System according to the preceding claims, characterized in that each short length tract line Illill is contained in a structure (Si) comprising two filters whose outputs on the line (L) are in approached points P1-P2, P3-P4, the outputs P2-P3, P4-P5 being in more distant points.

5) System according to the claim 4, characterized in that the structures S1... Sn are modular whereby the structure Si can be turned of 1800 over the preceding structure Si-1.

6) System according to the claim 4, characterized in that a modular structure (Si) comprises:

-an element which forms two cavities CT1a, CT1b and consists of a cylindrical body (CFC) having two transversal open ends (PA1a, PA1b), a transverse central wall (PS) which forms the bottoms of said two cavities and carries stationary dielectric resonator, and a fenster liFin) on the longitudinal cylindrical wall (51), in correspondence to the center of the separation transversal wall (PS); -two elements (REGa, REGb) for the tele-control of the said cavities frequencies, each element (REG) comprising a support (13) of a mobile dielectric IIDM), a closing wall (CH), a motor (M) and a control organ thereof (OR); and -a complex coupling device comprising at least: plates(PIA) overlapping each fenster (Fin); small bridges (CAVP) which are disposed centrally on each plate (PIA), bridge approached structures (S1-S2) and 13 contain internally a line portion (1 1-2); and long bridges (CAGV) bridging plates (PIA2, PIA3) associated to distant structures (S2-S3) and carry internally a line long tract. System according to the claim 6, characterized in that each plate (PIA) carries the two coupling loops - LO1a, L01b) prodruting from its lower face to penetrate, each, a resonant cavity (Ma, CT1b), and several pin screw or bolt heads (28, 29, 291, 31, 311, 39, 39') which protrude from the upper face to engage said bridges.

8) System according to the claim 7, characterized in that at the center of each plate (PIA) lower face, in correspondence to the wall (PS)of separation of each cavity a line tract (lab) is disposed to which are soldered the loop internal terminals which form the points (Ec) of connection to the line, said points (Ec) being, on their turn, connected, through said screws or pins (28, 29, 291, 31, 311, etc.) to the line portion within said bridges, the external loop ends (Cla, C1b) being earthed on the plate lower portion.

9) System according to at least one of claims 6, 7 and 8, characterized in that the second long bridge (CAVG) is grafted on the two plates (PIA 21 PIA 3 of consecutive distant structures of the type (S2-S3 Sn-2 -Sn-1) and houses internally the long tract (1 2-3) of the line, preferably of the coaxial type.

10) System according to the claim 8, characterized in that at the free ends of the first respectively last plate (PIA1, PIA4) are grafted, through pins (30-30% the strabs of short circuit 11PCC) respectively of connection to the antenna XIN-Ant).

) 4 11) A system for combining 2n (modulated) high frequency signals substantially as herein particularly described with reference to and as illustrated in the accompanying drawings.

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