SE523612C2 - Signal coupling arrangement has two transformer sides with respective windings, second winding having additional terminals connected to ground for reducing noise and preferably reducing losses through the M factor and/or enhancing Q factor - Google Patents

Abstract

The arrangement includes a first transformer side with a first winding connected to a signal input and a second transformer side with a second winding with two terminals and connected to a signal output. The second winding has additional terminals connected to a ground for reducing noise and preferably reducing losses through the M factor and/or enhancing Q factor which provides for a dynamic and high bandwidth Independent claims are also included for the following: (a) an arrangement for coupling/decoupling a data singal; (b) a method of reducing noise in a signal coupling arrangement.

Description

25 30 n I n., O -. , _ _ 'I ". A." u e .... n., _ _ 'I n. u .ø- n. h,, "ß n. '4 I. ,, .." 1 I n n », One can easily calculate the reactance to be the same as the impedance of the network, i.e. Xc = a> L2 = 100 ohms and mL. = 50 ohms.

The conduction impedance ZO can be calculated as: Z flfl l / IQ ° =: ii- RsRg where M = K L, * Lz Q = mL, / Rs K factor depends on the physical distance between the two coils and their orientation relative to each other. Optimal energy transfer is achieved when (ZrçfMY / Rs is equal to Rg. The disadvantage of these couplers is: losses through the M-factor which will give efficiency at 25-40%.

The Q factor provides a limited bandwidth of some 6-8 MHz. manufacturing problems, which force to trim all devices.

PPV “Shielding to reduce EMC will affect the performance of the coupler.

To improve the performance of the coupler, it is possible to increase the K-factor and eliminate the Q-parameter; preferably by using a coupler with a ferrite core.

This solution is very common in broadband power amplifiers in radio frequency (RF) bands. To achieve the broadband solution, the wires are wound in a two-wire mode on a core. This design acts as a transmission line and the winding of a representative toroid, the signal is coupled in a magnetic mode at lower frequencies and capacitive at higher frequencies. A coupler wound in transmission mode has the transfer function expressed mathematically as: Power output _ 4 (1+ cos ßl) 2 _ To gangzfgkfa fi su + cos ßzy + 4 51112 ßz '10 15 20 25 0 u now. , u .. a., _ "0- I nunp - ua nu .. a n. .., _ _ -. a _ .. u» .u ,,, '~ a.,::: ~: - ; ~ 'n 3 where ß is the phase constant and I is the length of the wire.

This means that the response is down 1 dB at l = Ä / 4 and zero level occurs at l = Ä / 2. For a good broadband response, the transformer must be small. The K-factor is close to 1. A possible bandwidth is e.g. 1 MHz to 50 MHz.

An alternative is the binocular broadband transformer, as shown in Figures 4a and 4b. Because the wires are surrounded by more core volume of iron material, it is less sensitive to the interdependence between the wires. This means that the wires can be wound in a straighter way and the function is more similar to a regular transformer, i.e .: Qi _ A _ (new _ 22 'where n1 and n2 are the number of coils and Z1 and Z2 the impedance of the first and second coils.

The equivalent scheme of the binocular is shown in Fig. 5 and is as follows: The following formulas can be used for this circuit: ZC_ ÅL ..

CD i .. Zl 2 co ”SD.- 1 2 wHZc Le = Z ° ZaJL where Zc corresponds to the representative transformer impedance wH high refraction of angular frequency cuL low refraction of angular frequency LL is the leakage inductance nnnn .W 10 15 20 25 30 35 u o o. . . a a | . ., 523 612 4 Cd The capacitance, mainly between wires Le Equivalent magnetizing inductance.

The formulas show that the bandwidth is width at minimum CD and LL, which depends on a few lead windings. The le value is maintained by a high AL value, which also gives smaller number of windings. The disadvantages of ferrite couplers are due to its high coupling factor, it is also sensitive to longitudinal noise and transients.

There are a number of patent documents relating to this field, which do not solve the mentioned problems in a satisfactory manner.

EP 961 415 A1 relates to a data transmission method which has a signal to be transmitted supplied to a power line by LV, MV or HV installation and extracts simultaneously via at least 2 output switches. Their signals are combined via a selection and combination step, to provide a simple output signal.

WO 93/25011 provides a coupling device for coupling a transmitting unit to a transmission line. According to this application, a transformer is provided whose secondary winding is part of a transmission line and whose primary winding is integrated into a parallel resonant circuit, the resonant frequency of which is tuned each time to a carrier frequency of transmitted signal. In addition, a setting unit can also be provided for automatic setting of the parallel resonant circuit.

Brief Description of the Invention The main object of the invention is to provide a signal coupler which reduces and eliminates disadvantages of the known couplers, the advantages of the coupler according to the invention are that: less loss by the M-factor, better Q-factor gives a dynamic and high bandwidth, simple manufacture, less trimming and adjustment work and better shielding, which gives better performance of the coupler. In addition, the invention provides a more compact coupler.

For these reasons, in the initially mentioned device the second winding is provided with further tenninal ends connected to ground. Advantageously, the tennin terminals are arranged 523 612 (substantially) at the same distance from said first and second terminals. Preferably, the terminals are arranged at the same distance from said first and second terminals.

Advantageously, the coupler consists of a coil for radio frequencies. According to one embodiment, said transmitter consists of a toroidal coil or a cylindrical coil.

In a power line system connected to a data transmission system, the invention also relates to a device for coupling / disconnecting a data signal, comprising a first transmitting side provided with a first winding connected to a signal input and a second transmitting side comprising a second winding comprising a first and second terminals. and connected to a signal output. The second winding comprises additional terminals connected to ground.

The invention also relates to a method for reducing noise in a signal switching device, comprising a first winding connected to a signal input and a second winding connected to a signal output. Method comprises the steps of grounding a longitudinal component in said winding of at least one of the windings at substantially a midpoint. Brief Description of Drawings In the following, the invention will be described in more detail with reference to a number of exemplary embodiments illustrated in accompanying drawings, in which: Fig. 1 shows a schematic illustration of an information transmission system over a power line network; Figs. 2a and 2b show schematic layouts of an air coupler and its electrical equivalent.

Fig. 3 shows an electrical equivalent diagram of a coupler, Figs. 4a and 4b show in a schematic manner a binocular transformer from the front and from the side, Fig. 5 shows an equivalence diagram for a ferrite coupler, Fig. 6 shows an equivalence diagram illustrating a coupler according to a first embodiment of the invention, Figs. 7a and 7b show attenuation of "common mode" interference currents, Fig. 8 shows an equivalence diagram Fig. 9 shows a measuring set for measuring noise in a coupler according to prior art, Fig. 10 shows the result of a measurement according to the set in Fig. 9, aaaa. Fig. 11 shows a measurement set for measuring noise in a coupler according to the present invention, Fig. 12 shows the result of a measurement according to the set in Fig. 11, Fig. 13 shows a measuring set for measuring noise in a coupler according to a second embodiment according to the present invention, Fig. 14 shows a first embodiment of the invention applied to a troid coil, Fig. 15 shows a first embodiment of the invention applied to a P9 coil, Fig. 16 shows an equivalence diagram showing a coupler according to Figs. 14 and Fig. 17 shows the result of a measurement according to the set in Fig. 13, Fig. 18 shows the result of a measurement according to the set in Fig. 17, Detailed description of the embodiments The coupler according to the present invention solves the problems of changing it from an unbalanced embodiment. to a balanced one.

The solution is shown schematically in Fig. 6, which shows an exemplary coupler for verifying attenuation noise. The signal at the output is measured by means of an oscilloscope with a high impedance input. Compared to an unbalanced coupler, the noise floor is lower than about 10-20 dB. The invention includes arranging a grounded central socket on the coupler coil.

When an unbalanced coupler is used, the longitudinal noise is superimposed on the signal on the secondary side of the coupler, i.e. on the unshielded wire in the core and the connecting wire picks the longitudinal noise and transient components as a wire antenna. The balanced coupler will direct the noise to the center socket of the coupler and extinguish the noise, i.e. the length component is grounded neutral via the center socket of the coupler. One result is that the noise floor is reduced for the benefit of the dynamic signal. This is schematically illustrated in Figures 7a and 7b, comparing the noise current ic in an unbalanced (Fig. 7a) and balanced (Fig. 7b) according to the invention. In an unbalanced switch common-mode noise currents, ic, are connected directly to the output of the switch as the noise is modulated on the output signal.

This is due to the coupling capacitance, Cmy, between the primary and secondary sides. 10 15 20 25 30 35 525 612 7 In a balanced coupler, the capacitance, Cway, between the primary and secondary sides is focused on a center terminal region and transforms the common-mode noise currents to the center terminal; thus eliminating the noise on the output signal.

Fig. 8 shows a proposal for a front receiver including a balanced coupler according to the present invention. To improve attenuation of the noise and EMC (also on the TX side), a filter inductor is inserted on the 220 V line. The amplifier operates with high impedance and transforms the signal to a low impedance state.

To better illustrate the parts of the invention, a number of measurements were made, which are shown in Figures 9 to 14.

Fig. 99 shows a measuring set consisting of an unbalanced coupler. An AMIDON transformer (N = 3: 4) was used for the measurement, which was connected to the 220 V power line through two 10 nF filter capacitors. A TEKTRONIX 3032 oscilloscope was used to measure the signal over a coaxial cable. The result is shown in the digram in Fig. 10. At 30 MHz, the noise was measured at -90 dB, which corresponds to -120 dBm.

Fig. 11 shows a measuring set consisting of a balanced coupler. An AMIDON transformer (N = 3: 4) and TOKO 1026 (N = 1: 1 * 1) transformer were used for the measurement. The AMIDON transformer was connected to the 220 V power line through two ond lter capacitors. In the first measurement 10 nF capacitors were used and in the second 470 pF capacitors. The center of the coils was grounded.

A TEKTRONIX 3032 oscilloscope was used to measure the signal over a coaxial cable. The result is shown in the digram in Fig. 12 for 10 nF. At 30 MHz, the noise was measured at -100 dB, which corresponds to -130 dBm. For 470 pF capacitors, the change was marginal: -99 dB.

Fig. 13 is a measuring set comprising a balanced coupler. For the measurement, two TOKO 1026 (N = 1: 1 * 1) transformers were used, which were connected to a 220 V power line through two 470 pF filter capacitors. A TEKTRONIX 3032 oscilloscope was used to measure the signal over a coaxial cable. The result is shown in the digram in Figs. 17 and 18. The digram in Fig. 17 shows that the coupler was not connected to the power line. The diagram in Fig. 18 shows the coupler connected to the power line. At 30 MHz, the noise was measured at -90 dB, which corresponds to -120 dBm. 10 15 20 25 30 ~ a ø. . n. - -. Figs. 14 and 15 show the physical appearance of two embodiments of couplers according to the invention. In Fig. 14, the coupler 14 includes a ring totoid 141 with a primary winding 142 and secondary winding 142. The primary winding includes a center socket 144. The equivalence diagram is shown in Fig. 16. The end sockets are denoted by Roman numerals i to vi, where i and v are the end sockets of the secondary winding, ii and iii the middle socket, and v and vi the primary side end sockets.

Fig. 15 shows the core (P9) of a transformer 150 comprising a cylindrical core 151 with a primary winding 152 and a secondary winding 153. The center socket 154 is arranged at the secondary winding 153. The equivalence diagram in Fig. 16 also relates to this embodiment. Thus, the end sockets mentioned in the previous embodiment are denoted by Roman numerals i to vi, where i and v are the end sockets of the secondary winding, ii and iii of the middle socket, and v and vi are the end sockets of the primary side.

Of course, the invention is not limited to the transformers described above and other transformers are also possible.

It should be noted that the above measurements are given as non-limiting examples and the measurement results may vary due to parameters involved in the measuring instruments, etc. the invention is not limited to the embodiments shown, but can be varied in different ways without being removed from the scope of the appended claims, and the device and method can be implemented in different ways depending on application, functional units, needs, requirements and so on.

Claims (1)

1. 0 15 20 25 30 35 523 612 q. . DEMAND us. A signal coupler (140, 150) for connecting signals to a power line, which signal coupler comprises a core (141, 151), on which a primary winding (143, 153) is arranged connected to a signal input and a secondary winding (142, 152). , characterized in that said secondary winding consists of parallel conductors, a first and a second conductor, said first conductor comprising first and second terminals (i, vi) for connection to a signal output, and that said second conductor comprises first and second terminals ( 144, 154) for connection to earth. Coupling device according to claim 1, characterized in that said first and second terminals (144, 154) are arranged substantially at the same distance from said first and second terminals of said first conductor. . Coupling device according to claim 1, characterized in that said terminal (144, 154) is arranged at the same distance to said first and second terminals of said first conductor. Coupling device according to claim 1, characterized in that said core consists of a coil for radio frequencies. Coupling device according to any one of claims 1-4, characterized in that said core consists of a toroidal coil (141). Coupling device according to any one of claims 1-4, characterized in that said core consists of a cylindrical coil (141). '-4 10 15 523 612 lo' '. In a power line system connected to a data transmission system, a device (140, 150) for coupling / disconnecting a data signal to the power line system, comprising a core (141, 151) provided with a primary winding (143, 153) connected to a signal input and a secondary winding ( 142, 152), characterized in that said secondary winding consists of parallel conductors: a first and a second conductor, said first conductor comprising first and second terminals (i, vi) connected to a signal output, and that said second conductor comprises first and other terminals (144, 154) for grounding. A method of reducing interference in a signal switching device (140, 150), comprising a core (141, 151) provided with a primary winding (143, 153) connected to a signal input and a secondary winding (142, 152) connected to a signal output, which method comprises the steps of grounding a longitudinal component in said winding of at least one of the windings at substantially a center point.