Method and apparatus for determining characterics of components of a communication channel under load
Abstract
TO DETERMINE THE CHARACTERISTICS OF COMPONENTS OF A COMMUNICATION CHANNEL, FOR EXAMPLE, OF A TRANSPONDER OF A COMMUNICATIONS SATELLITE, A CLEAN CARRIER F (T) SIGNAL IS MODULATED WITH A PN (T) SEUDORRUDED SIGNAL AND IS TRANSMITTED THROUGH THE CHANNEL OF COMMUNICATIONS, AT A LEVEL LOWER THAN THE LEVEL OF A USEFUL LOAD SIGNAL THAT IS SIMULTANEOUSLY TRANSMITTED THROUGH THE COMMUNICATIONS CHANNEL. THE RECEIVED SIGNAL S '' (T) IS COMPARED TO THE SAME SEUDORRUID SIGNAL PN (T) TO OBTAIN A RECOVERED BEARING SIGNAL F (T). BOTH THE CLEAN CARRIER SIGNAL F '' (T) AS THE RECOVERED CARRIAGE SIGNAL F '' (T) CAN BE USED TO DETERMINE THE DESIRED FEATURES. SINCE THE MODULATED CLEAN CARRIER SIGNAL PN, S (T), IS TRANSMITTED AT A LOW LEVEL, MEASUREMENTS CAN BE MADE WITHOUT DISCONNECTING THE USEFUL LOAD SIGNAL.

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29 claims: 14 independent, 15 dependent
- 1ES 2 175 256 T3 REIVINDICACIONES 1. Método para determinar las características de los componentes de un canal de comunicación, a través del que se transmite una senal de carga a un nivel predeterminado, comprendiendo:- generar una primera senal de pseudo-ruido PN (t);- modular una senal portadora limpia f (t) con dicha primera senal de pseudo-ruido PN (t) a fin de generar una senal portadora limpia modulada PNs (t);- transmitir dicha senal portadora limpia modulada PNs (t) simultéaneamente don dicha senal de carga a traves de dicho canal de comunicaciéon a un nivel inferior al nivel de dicha senal de carga;- recibir una senal de recepcion s' (t) correspondiente a dicha senal portadora limpia modulada PNs (t) una vez que ha circulado por dicho canal de comunicacioén;- correlacionar dicha senal de recepcion s' (t) con la referida senal de pseudo-ruido PN (t) a fin de generar una senal portadora recuperada f' (t);y - determinar la caracterésticas de los componentes del canal de comunicaciéon sobre la base de una comparacion entre dicha senal portadora limpia f (t) y dicha senal portadora recuperada f' (t), en donde se consigue dicha correlacioén de dicha senal de recepcion s' (t) y dicha primera senal de pseudo-ruido PN (t) retardando dicha primera senal de pseudo-ruido PN (t) y multiplicando la primera senal de pseudo-ruido retardada PN (t) y dicha senal de recepcion s' (t).
- 2Méetodo conforme a la reivindicaciéon 1, en donde el nivel de dicha senal portadora limpia modulada PN s(t) es de al menos 15 decibelios por debajo del nivel de dicha senal de carga.
- 3Méetodo conforme a la reivindicaciéon 2, en donde el nivel de dicha senal portadora limpia modulada PN s(t) es de al menos 25 decibelios por debajo del nivel de dicha senal de carga.
- 4Méetodo conforme a cualquiera de las reivindicaciones de la 1 a la 3, en donde dicha primera senal de pseudo-ruido PN (t) es una secuencia binaria de pseudo-ruido.
- 5Méetodo conforme a la reivindicaciéon 4, en donde dicha secuencia binaria de pseudo-ruido se genera a travées de un registro de desplazamiento de realimentaciéon, o un dispositivo de memoria en el que es almacenada una secuencia de valores de una senal de pseudo-ruido.
- 6Méetodo conforme a cualquiera de las reivindicaciones de la 1 a la 5, en donde la velocidad del chip de dicha primera senal de pseudo-ruido PN (t) es inferior a 5 Mchip/s.
- 7Méetodo conforme a la reivindicaciéon 6, en donde la velocidad del chip de dicha primera senal de pseudo-ruido PN (t) es inferior o igual a 2,5 Mchip/s.
- 8Méetodo conforme a cualquiera de las reivindicaciones de la 1 a la 7, que comprende:- generar una segunda senal de pseudo-ruido PNR (t);- modular una senal portadora de referencia f R (t) con dicha segunda senal de pseudoruido PN r (t), a fin de generar una senal portadora de referencia modulada PN SR (t);- transmitir dicha senal portadora de referencia modulada PN SR (t) de forma simulténea con dicha senal de carga a traves de dicho canal de comunicacioén a un nivel inferior al nivel de dicha senal de carga;- recibir una senal de recepcion de referencia S R (t) correspondiente a dicha senal portadora de referencia modulada PN SR (t) una vez que ha circulado a traveés de dicho canal de comunicaciéon;- correlacionar dicha senal de recepcion de referencia Sr (t) con dicha segunda senal de pseudo-ruido PNR (t) a fin de generar una senal portadora de referencia recuperada f R (t), y - determinar las caracterésticas de los componentes del canal de comunicaciéon tambiéen sobre la base de la comparaciéon entre dicha senal portadora de referencia f R (t) y dicha senal portadora recuperada f R (t) .
- 9Méetodo conforme a la reivindicaciéon 8, en donde el nivel de dicha senal portadora de referencia modulada PN SR (t) es de al menos 15 decibelios por debajo del nivel de dicha senal de carga.
- 10Méetodo conforme a la reivindicaciéon 9, en donde el nivel de dicha senal portadora de referencia modulada PN SR (t) es de al menos 25 decibelios por debajo del nivel de dicha senal de carga.
- 11Méetodo conforme a cualquiera de las reivindicaciones de la 8 a la 10, en donde dicha segunda senal de pseudo-ruido PN R (t) es una secuencia binaria de pseudo-ruido.
- 12Méetodo conforme a la reivindicaciéon 11, en donde dicha secuencia binaria de pseudo-ruido se genera a travées de un registro de desplazamiento de realimentaciéon, o un dispositivo de memoria en el que es almacenada una secuencia de valores de una senal de pseudo-ruido.
- 13Méetodo conforme a cualquiera de las reivindicaciones de la 8 a la 12, en donde dicha correlacion de dicha senal de recepcion de referencia Sr (t) y dicha segunda senal de pseudo-ruido PNR (t) se consiguen retardando dicha segunda senal de pseudo-ruido PN R (t) y multiplicando la segunda senal de pseudo-ruido retardada PN R (t) y dicha senal de recepcion de referencia S R (t) .
- 14Méetodo conforme a cualquiera de las reivindicaciones de la 1 a la 13, en donde dicho canal de comunicaciéon es un repetidor de un satéelite de telecomunicaciéon.
- 15Méetodo conforme a las reivindicaciones 13 y 14, en donde dicha senal portadora de referencia modulada PN SR (t) es transmitida a travées del mismo repetidor del satélite y dicha segunda senal de pseudo-ruido PNR (t) no se correlaciona con dicha senal de pseudo-ruido PN (t). ES 2 175 256 T3
- 16Méetodo conforme a las reivindicaciones 13 y 14, en donde dicha senñal portadora de referencia modulada PN SR (t) es transmitida a travées de un repetidor diferente del satéelite.
- 17Méetodo conforme a cualquiera de las reivindicaciones de la 1 a la 16, donde una de las caracterésticas de dicho canal de comunicaciéon es el retardo de grupo o la amplitud de respuesta.
- 18Aparato para determinar las caracterésticas de los componentes de un canal de comunicaciéon a travées del cual se transmite una senñal de carga a un determinado nivel, comprendiendo:- medios generadores de una primera senñal de pseudo-ruido (9) que generan una senñal de pseudo-ruido PN (t);- medios moduladores iniciales (10) que modulan una senñal portadora limpia f (t) con dicha primera senñal de pseudo-ruido PN (t) a fin de generar una senñal portadora limpia modulada PNs (t);- medios transmisores (11, 12, 13) para transmitir dicha senñal portadora limpia modulada PNs (t) simultéaneamente con dicha senñal de carga a travées de dicho canal de comunicaciéon a un nivel inferior al nivel de dicha senñal de carga;- medios receptores (13, 14) para recibir una senñal de recepciéon s' (t) correspondiente a dicha senñal portadora limpia modulada PNs (t) una vez que ha circulado por dicho canal de comunicaciéon;- medios iniciales de correlaciéon (14) para correlacionar dicha senñal de recepciéon s' (t) con dicha senñal de pseudo-ruido PN (t) a fin de generar una senñal portadora recuperada f' (t);y - medios iniciales de retardo (16) para retardar dicha primera senñal de pseudo-ruido PN (t).
- 19Aparato conforme a la reivindicacioén 18, en donde el nivel de dicha senñal portadora limpia modulada PNs (t) es de al menos 15 decibelios por debajo del nivel de dicha senñal de carga.
- 20Aparato conforme a la reivindicacioén 19, en donde el nivel de dicha senñal portadora limpia modulada PNs (t) es de al menos 25 decibelios por debajo del nivel de dicha senñal de carga.
- 21Aparato conforme a cualquiera de las reivindicaciones de la 18 a la 20, en donde dichos medios generadores de una primera senñal de pseudoruido (9) son un registro de desplazamiento de realimentaciéon o un dispositivo de memoria, en el que se almacena una secuencia de valores de una senñal de pseudo-ruido.
- 22Aparato conforme a cualquiera de las reivindicaciones de la 18 a la 21, en donde la velocidad del chip de la primera senñal de pseudo-ruido PN (t) es inferior a 5 Mchip/s.
- 23Aparato conforme a la reivindicaciéon 22, en donde la velocidad del chip de la primera senñal de pseudo-ruido PN (t) es inferior o igual a 2,5 Mchip/s.
- 24Aparato conforme a cualquiera de las reivindicaciones de la 18 a la 23, comprendiendo:- medios secundarios generadores de pseudoruido (17), a fin de generar una segunda senñal de pseudo-ruido PNR (t);- medios moduladores secundarios (18), los cuales modulan una senñal portadora de referencia fR (t) con dicha segunda senñal de pseudo-ruido PNR (t) a fin de generar una senñal portadora de referencia modulada PN SR (t);- medios transmisores (11, 12, 13) para transmitir dicha senñal portadora de referencia modulada PN SR (t) simultaéneamente con dicha senñal de carga a travées de dicho canal de comunicaciéon a un nivel inferior al nivel de dicha senñal de carga;- medios receptores (13, 14) para recibir una senal de recepcion de referencia S R (t) correspondiente a dicha senñal portadora de referencia modulada PN SR (t) una vez que ha circulado a travées de dicho canal de comunicaciéon;y - medios secundarios de correlaciéon (20) para correlacionar dicha senñal de recepciéon de referencia S R (t) con dicha segunda senal de pseudo-ruido PNR (t) a fin de generar una senal portadora de referencia recuperada f R (t). R
- 25Aparato conforme a la reivindicaciéon 24, en donde el nivel de dicha senñal portadora limpia modulada PNs (t) es de al menos 15 decibelios por debajo del nivel de dicha senñal de carga.
- 26Aparato conforme a la reivindicacioén 25, en donde el nivel de dicha senñal portadora limpia modulada PNs (t) es de al menos 25 decibelios por debajo del nivel de dicha senñal de carga.
- 27Aparato conforme a cualquiera de las reivindicaciones de la 24 a la 26, en donde dichos medios generadores de una segunda senñal de pseudoruido (9) son un registro de desplazamiento de realimentaciéon o un dispositivo de memoria, en el que se almacena una secuencia de valores de una senñal de pseudo-ruido.
- 28Aparato conforme a cualquiera de las reivindicaciones de la 24 a la 27, comprendiendo ademéas medios secundarios de retardo (19) para retardar la segunda senñal de pseudo-ruido PNR (t).
- 29Aparato conforme a cualquiera de las reivindicaciones de la 18 a la 28, en donde una de las caracterésticas de dicho canal de comunicaciéon es el retardo de grupo o la amplitud de respuesta. NOTA INFORMATIVA:Conforme a la reserva del art. 167.2 del Convenio de Patentes Europeas (CPE) y a la Disposición Transitoria del RD 2424/1986, de 10 de octubre, relativo a la aplicacion del Convenio de Patente Europea, las patentes europeas que designen a España y solicitadas antes del 7-10-1992, no producirán ningún efecto en Espana en la medida en que confieran protección a productos químicos y farmaceuticos como tales. Esta informacioón no prejuzga que la patente estóe o no incluóda en la mencionada reserva.
Independent claims29
55 paragraphs in 2 sections, as filed
IS 2 175 256 T3
DESCRIPTION
Method and apparatus for determining the characteristics of the components of a load communication channel.
This invention relates to a method and an apparatus for determining the characteristics of the components of a communication channel, especially those of a telecommunication satellite repeater on load.
The characteristics of a communication channel may vary during the useful life of the equipment in question. It is possible to carry out various tests, not only at the beginning but also repeatedly during the life of the equipment, in order to verify that the communication channel complies with the predetermined specifications. Generally, these tests are carried out outside the normal communication traffic, that is, when the communication channel is not being used to transmit a communication signal. This scenario, related to communication satellites, will be explained in greater detail below, although the invention described below is not limited solely to this application, although it is specifically applicable to this field.
In a telecommunication satellite, the communication channel is created by a repeater of said satellite, made up of various components, such as a receiving antenna, an input demultiplexer, a power amplifier, an output multiplexer and a transmitting antenna. Repeater characteristics, such as response amplitude and group delay, are measured not only at the beginning of the plane's life on the ground and, after launch, at eorbit, but also during its useful life. These measurements are usually carried out without normal traffic on the repeater, that is, when a load signal is not transmitted to the repeater and when said signal is not retransmitted by the repeater.
The need to disconnect the load signal during the tests represents a significant disadvantage, not only for the repeater user, since communication is interrupted, but also for the satellite operator, since the tests have to be carried out quickly. in order to minimize the duration of the interruption as much as possible. In some cases it is impossible to interrupt communication through the communication channel, which is why the components of these channels cannot be tested once they begin to function.
The US-A-4,637,017 standard is related to the supervision of the input power to a repeater of a TDMA satellite communication system. In TDMA systems, only one carrier frequency is present at the input of the traveling wave valve amplifier, which can therefore be operated close to the TWT saturation point in the absence of non-linearity and intermodulation. In order to measure the input-recoil, a monitoring station transmits a CW pilot signal within the bandwidth of the amplifier. In the protection time between discharges, the supervising station measures the output signal level not suppressed by the amplifier. While a ground station is transmitting an unmodulated carrier signal during the recovery time of the same or a carrier signal modulated at the frequency of the pilot clock during the recovery of said clock, the supervising station measures the suppressed output signal level. by the non-linear interaction of the pilot signal and the carrier. The amount of pilot signal suppression is related to the input-reverse energy of the carrier signal through a previously measured or theoretically derived relationship. The carrier signal-suppressed noise ratio is determined by measuring the level of the carrier signal during the recovery of said signal, as well as by measuring the suppressed noise during the recovery period of the carrier signal or the pilot clock through a noise filter. placed away from any transmission signal or from the intermodulations generated.
Regulation DE-A-36 44 175 discloses a method of satellite transmission of data and auxiliary information to control the data channel or the data network, respectively. Auxiliary information is transmitted as pseudo-noise sequences, in such a way that the same frequency can be used for transmission of data and auxiliary information.
The US-A-5, 546, 421 standard discloses a spread spectrum self-compensating hybrid system that is used in a communications station coupled to a bidirectional input-output path signal. Such a communications station could be, for example, a simple equipment of a telephone line terminal. A hybrid circuit is defined as a multi-port component that links an input signal to one of the nearby ports without influencing the other ports. This property is called "directivity", the quality of directivity being characterized by "isolation". Maximum isolation is achieved when the bi-directional path transmission signal presents an impedance with the bi-directional signal of the hybrid circuit port that matches the impedance for which said hybrid circuit has been designed. The US-A-5, 546, 421 standard identifies the problem that the impedance presented in the bidirectional path signal to the hybrid circuit can change dynamically during operation. Therefore, it is suggested to make use of the spread spectrum pilot signal. The spread spectrum pilot signal covers the bandwidth of the information signal, and is reflected by the bidirectional path signal. The pilot signal is detected in phase, processed and applied to the hybrid circuit to minimize the amount of transmitted signal coupled to the receiving panel in a closed loop operation.
The purpose of this invention is to provide a method and apparatus for determining the characteristics of the components of a communication channel, especially a telecommunication satellite repeater, without the need to interrupt the traffic through the communication channel.
This and other purposes are accomplished by a method of determining the characteristics of
ES 2 175 256 T3 the components of a communication channel, through which a load signal is transmitted at a predetermined level, said method comprising: generating a first pseudo noise signal PN (t); modulating a clean carrier signal f (t) with said first pseudo-noise signal PN (t) in order to generate a clean carrier signal modulated PNs (t); transmitting said PNs (t) modulated clean carrier signal simultaneously with said load signal through said communication channel at a level lower than the level of said load signal; receiving a reception signal s' (t) corresponding to said PNs modulated clean carrier signal (t) once it has circulated through said communication channel; correlating said reception signal s '(t) with said first pseudo-noise signal PN (t) in order to generate a recovered carrier signal f' (t); and determining the characteristics of the components of the communication channel based on a comparison between said clean carrier signal f (t) and the recovered carrier signal f '(t), where said comparison of said reception signal s' (t) and said first pseudo-noise signal PN (t) are achieved by delaying said first pseudo-noise signal PN (t) and multiplying this first delayed pseudo-noise signal PN (t) by said reception signal s' (t ).
As an advantage, the level of said PNs modulated clean carrier signal (t) is at least 15 decibels, preferably 25 decibels or more below the level of said load signal.
In another possible application, said first pseudo-noise signal PN (t) is a binary pseudo-noise sequence, which is preferably generated by means of a feedback shift register.
The chip speed of said first pseudo-noise signal PN (t) is less than 5 Mchip / s and preferably less than or equal to 2.5 Mchip / s.
In order to obtain a reference, the method according to the invention further comprises: generating a second pseudo-noise signal PN<sub>R</sub> (t); modulate a reference carrier signal f<sub>R</sub> (t) with said second pseudo-noise signal PN<sub>r </sub>(t), in order to generate a PN SR modulated reference carrier signal (t); transmit said reference carrier signal modulated PN S<sub>R </sub>(t) simultaneously with said load signal through said communication channel at a level lower than the level of said load signal; receiving a reference reception signal Sr (t) corresponding to said PN modulated reference carrier signal SR (t) once it has circulated through said communication channel; correlate said reception signal of reference Sr (t) with said second signal of pseudo-noise PN<sub>R </sub>(t) in order to generate a recovered reference carrier signal f<sub>R</sub> (t), and determine the characteristics of the components of the communication channel also on the basis of the comparison between said reference carrier signal f<sub>R</sub> (t) and said recovered carrier signal f<sub>R</sub> (t).
As an advantage, the level of said modulated reference carrier signal SR (t) is at least 15 decibels, preferably 25 decibels or more below the level of said load signal.
In another possible application, said second pseudo-noise signal PN<sub>R</sub> (t) is a binary pseudo-noise sequence, which is preferably generated by means of a feedback shift register.
In another possible application, said correlation between said reception signal of reference Sr (t) and said second signal of pseudo-noise PN<sub>R </sub>(t) is achieved by delaying said second PNR pseudo-noise signal (t) and multiplying the second delayed pseudo-noise signal PN<sub>R</sub> (t) for said reference reception signal <sup>S</sup>R <sup>(t)</sup>.
The method of this invention, as described above, is especially applicable when said communication channel is a repeater of a telecommunication satellite. Said modulated reference signal PN SR (t) can be transmitted through the same repeater of the satellite, but then, said second signal of pseudo-noise PN<sub>R </sub>(t) must not be correlated with said pseudo-noise signal PN (t). Said modulated reference signal PN SR (t) can also be transmitted through a repeater other than the satellite.
The characteristics of this communication channel can be the group delay and the response amplitude.
The above objectives and others are also achieved with an apparatus for determining the characteristics of the components of a communication channel, through which a load signal is transmitted at a predetermined level. Said apparatus comprises: means for generating a first pseudo-noise signal that generates a pseudo-noise signal PN (t); initial modulator means modulating a clean carrier signal f (t) with said first pseudo-noise signal PN (t) in order to generate a clean modulated carrier signal PNs (t); transmitting means for transmitting said PNs (t) modulated clean carrier signal simultaneously with said load signal through said communication channel at a level lower than the level of said load signal; receiving means for receiving a reception signal s' (t) corresponding to said PNs modulated clean carrier signal (t) once it has circulated through said communication channel; initial correlation means for correlating said reception signal s '(t) with said pseudo-noise signal PN (t) in order to generate a recovered carrier signal f' (t); and also comprises initial delay means for delaying said first pseudo-noise signal PN (t).
As an advantage, the level of said PNs modulated clean carrier signal (t) is at least 15 decibels, preferably 25 decibels or more below the level of said load signal.
In another possible application, said initial means for generating the pseudo-noise signal consist of a feedback shift register.
The chip speed of said first pseudo-noise signal PN (t) is less than 5 Mchip / s and preferably less than or equal to 2.5 Mchip / s.
In order to obtain a reference, the above apparatus further comprises secondary pseudo-noise generating means, which generate a second pseudo-noise signal PN<sub>R</sub> (t); secondary modulating means, which modulate a
ES 2 175 256 T3 reference carrier signal f<sub>R</sub> (t) with said second pseudo-noise signal PN<sub>R</sub> (t) in order to generate a modulated reference carrier signal PN SR (t); transmitting means for transmitting said PN S modulated reference carrier signal<sub>R</sub> (t) simultaneously with said load signal through said communication channel at a level lower than the level of said load signal; receiving means for receiving a reference reception signal S<sub>R</sub> (t) corresponding to said PN SR modulated reference carrier signal (t) once it has circulated through said communication channel; and secondary correlation means for correlating said reference reception signal S<sub>R</sub> (t) and said second pseudo-noise signal PN<sub>r</sub> (t) in order to generate a recovered reference carrier signal <sup>F</sup>R ' <sup>(t)</sup>.
The advantage is that the level of said modulated reference carrier signal s (t) is at least 15 decibels, preferably 25 decibels or more below the level of said load signal.
In another possible application, said secondary means for generating the pseudo-noise signal consist of a feedback shift register.
In another of the applications, said apparatus further comprises secondary delay means for delaying said second pseudo-PNR signal (t).
In summary, in order to determine the characteristics of the components of a communication channel, for example, of a repeater of a telecommunication satellite, a clean carrier signal f (t) is modulated with a pseudo-noise signal PN (t) y It is transmitted through a communication channel at a level lower than the level of the load signal, which is transmitted simultaneously on the communication channel. The received signal s '(t) is correlated with the same pseudo-noise signal PN (t) in order to obtain a recovered carrier signal f' (t). The clean carrier signal f (t) and the recovered carrier signal f '(t) are used together to determine the desired characteristics. Because the PN modulated clean carrier signal s (t) is transmitted at a low level, it is possible to perform measurements without having to disconnect the load signal.
The most important advantage of the method and apparatus according to this invention is, of course, the fact that the load signal does not need to be switched off to carry out measurements. This considerably reduces the downtime required for maintenance and verification of the communication channel, and thus increases the availability of services.
Another very important advantage is the fact that with this method and this apparatus it is possible to measure the characteristics of the components of the communication channel in real conditions. For example, in a satellite repeater the IMUX and OMUX filters are waveguide filters, whose characteristics change with temperature. Filters do not normally heat up uniformly during operation, but rather according to the load signal. When the load signal is disconnected, the temperature distribution changes compared to normal operation, even when the test signals provide a certain power to heat these filters. Thus, with conventional methods, the characteristics cannot be determined under the conditions existing when the communication channel is loaded. Furthermore, in the suggested method, the spectral power density of the measurement signal is considerably lower than the spectral power density of the load signal, so that it is possible to describe the behavior of the communication channel in the most real conditions. .
Another additional advantage of this invention consists in that in the case of a satellite communication channel, the conversion frequency of the transmission / reception can be measured without interrupting the load signal and simultaneously with the other measurements.
An application of the invention is described below in greater detail, and with reference to the drawings.
Figure 1: Shows a schematic diagram of a repeater of a telecommunication satellite;
Figure 2: Shows a schematic diagram of a first application of an apparatus according to the invention;
Figures 3a and 3b show diagrams representing the result of measurements;
Figure 4: Shows a schematic diagram of a second application of an apparatus according to the invention.
In order to describe an application of the invention, the
Figure 1 shows the components of a telecommunication satellite repeater as an example of a communication channel.
A repeater of a telecommunication satellite comprises a receiving antenna 1 for receiving a transmission signal sent from a ground station (not shown). An output signal of said receiving antenna 1 is connected to an input demultiplexer (IMUX) 3 once the frequency conversion has been carried out in the frequency converter 2. Said input demultiplexer 3 is composed of various primary filters 4-1 to 4-2, which separate the individual signals within the antenna signal. The normal thing is that there is a filter for each signal, in order to separate it from the other signals received through said receiving antenna 1, and which corresponds to a communication channel. The output signals n of said input demultiplexer 3 are connected to the corresponding number of high power amplifiers 5-1 to 5-n, in each of which a traveling wave tube (TWT) is used in order to amplify the signals. output signals from said input demultiplexer 3. Because each of these high-power amplifiers operates normally at its saturation point, multiple signals will create intermodulation and distortion products in the signals. The amplifier output signals pass through secondary filters 6-1 through 6-n, which are
ES 2 175 256 T3 starts from an output multiplexer (OMUX) 7, which combines the output signals of amplifier n. The output signal of said output multiplexer 7 is connected to a transmitting antenna 8 in order to be transmitted to the desired terrestrial area.
Since the filters of the input demultiplexer (IMUX) 3 and the output multiplexer (OMUX) 7 exert a strong influence on the behavior of the repeater, the method according to the invention will be explained below, related to the measurement of two characteristics specific to these components of the repeater's communication channels: response amplitude and group delay; the method of this invention being especially suitable for this application. However, the same or other characteristics of other components of the communication channel can be determined by means of this method and the apparatus, according to the invention.
According to this invention, in a ground station, as shown in figure 2, a pseudo-noise signal PN (t) is generated by means of a pseudo-noise signal generator 9, for example, a shift register feedback or a memory device, in which a sequence of values of a pseudo-noise signal is stored. The pseudo-noise signal PN (t) has a very accurate autocorrelation function at the zero degree of delay. This makes it possible to determine the delay time between the locally generated pseudo-noise signal PN (t) and a reception signal delayed due to propagation time. A clean carrier signal f (t) of variable frequency, which is modified as explained below, is modulated with said pseudo-noise signal PN (t) by means of a first multiplier 10 in order to form a clean carrier signal modulated PN s (t) = PN (t) xf (t). The chip speed of the pseudo-noise signal PN (t), which determines the bandwidth of this signal, is chosen taking into account that the bandwidth of the clean carrier signal modulated PN s (t) is lower than the expected peaks of the group delay of the communication channel. Normally, the chip speed of the pseudo-noise signal can be set to less than 5 Mchip / s.
The PN modulated clean carrier signal s (t) is connected to a frequency upconverter 11 and, through a high power amplifier 12, to an antenna 13, which transmits the PN modulated clean carrier signal s (t) at a repeater of the telecommunication satellite under test. However, from the point of view of a user transmitting a load signal to the satellite, it is possible to use the repeater during the test and the repeater can be continuously fed with a load signal.
According to this invention, the level of the transmitted PN s (t) modulated clean carrier signal is sufficiently lower than the level of the load signal, for example, about 15 or 25 decibels, or even more, so that there is no deterioration. noticeable in the charging signal. For this reason, the modulated clean carrier signal PN s (t) can be transmitted while the communication channel is in use, that is, at the same time that a load signal is transmitted to the satellite repeater from the same station or from another station. land.
The frequency of the clean carrier signal f (t) is varied so that it passes from the lowest to the highest frequency of the passband of the satellite repeater filters, or any other component of a general communication channel under test. The modulated clean carrier signal PN s (t) has a narrow bandwidth, due to the pseudo-noise signal PN (t), so that the response amplitude and the group delay of the communication channel can be determined at selected discrete frequencies, as described below.
In this application, the antenna 13 is also used to receive the signal relayed by the satellite repeater, in other words, the signal that has traveled through the communication channel. The output signal of the antenna 13 passes through a subconverter 14 in order to obtain a reception signal s' (t), which is connected to a second multiplier 15 that also receives the same pseudo-noise signal PN (t ) but delayed. The delay is generated by delay means 16, which are arranged in such a way that the output of the second multiplier 15 becomes the maximum. In this way, the reception signal s' (t) is multiplied, in other words, it is correlated with the same pseudo-noise signal PN (t), which has been used to generate the modulated clean carrier signal PN s (t ) and a recovered carrier signal f '(t) is obtained, which is only delayed and attenuated compared to the clean carrier signal f (t). Thus, the response amplitude, which corresponds to the attenuation of the recovered carrier signal f '(t), and the group delay, which corresponds to the delay of the recovered carrier signal f' (t) of the satellite repeater, as an example of a general communication channel, can be easily determined. The operating time of the narrow band signal, at its center frequency, corresponds to the group delay of the filters if the phase can be approximated linearly in the bandwidth of the signal. The chip speed of the PN signal is determined accordingly.
As far as telecommunication satellites are concerned, it is sufficient to determine the response amplitude and the group delay on the passband of the repeater, relative only to the response amplitude and the group delay at the center frequency of the bandwidth. He passed. Therefore, it is sufficient to delay the pseudo-noise signal PN (t) so that the amplitude of the recovered carrier signal f '(t) becomes the maximum and subtract the amplitude and the delay of the central frequency, from the amplitude and delay of any other frequency in the passband, respectively.
Figures 3a and 3b show typical results of response amplitude measurements (Figure 3a) and group delay (Figure 3b) obtained by the method according to the invention.
In the case of a telecommunication satellite channel, for example, a repeater, it should be noted that during the measurements, and due to the movements of the satellite, the distance at which it is located may vary. Also, during measurements, due to at5 effects
ES 2 175 256 T3 mospheric, the attenuation of the loss of passage between the ground station and the satellite can also vary. Since in the above application the response width and group delay are determined by subtracting the response width and group delay of the center frequency from the respective values of other discrete frequencies, it is possible to incur an error due to the above mentioned movements of the satellite, as well as atmospheric effects or other influences.
As shown in Figure 4, it is possible to use the reference signal S<sub>R</sub> (t) to compensate for the aforementioned measurement error. In Figure 4, the same reference signs are used to identify those parts described above, with reference being made to the previous description of said parts. The reference signal SR (t) is generated by means of a third multiplier 18, which receives a second pseudo-noise signal PN<sub>R</sub> (t), which is not correlated with the first pseudo-noise signal PN (t), and which is generated by a second pseudo-noise generator 17, and a reference carrier signal fR (t), which can be located on a fixed frequency somewhere in the passband of the same repeater or in the passband of another repeater on the same satellite, but with a different center frequency. As in the previous application, a PN S modulated reference carrier signal is transmitted to the satellite.<sub>R </sub>(t) and the reference receive signal <sup>S</sup>R <sup>(t)</sup> multiplied by the second pseudo-noise signal PN<sub>r</sub> (t) in order to obtain the recovered reference signal f<sub>R</sub> (t). While the measurement signal is varied in frequency along the passband of the repeater, the frequency of the reference carrier signal fR (t) remains at a fixed frequency. Therefore, it is possible to obtain a corrected communication channel response amplitude and group delay by subtracting the values of the reference signal from the values of the measurement signals in their respective time.
A variation of the described group delay measurement would consist in measuring the phase of the reconstructed carrier of the modulated PN signal at a specified frequency very close to the first frequency. It is possible to approximate the group delay to the frequency located between the two measurement frequencies, by calculating the phase difference and dividing by the frequency difference.
Only pseudo noise signals have been described here, as these signals can be generated relatively easily. However, it is also possible to use actual noise signals with the method and apparatus related to this invention. The properties of pseudo noise and real noise signals are well known to those skilled in the art, and are described, for example, in the book "Digital Communications - Fundamentals and Applications", Prentice Hall, 1988, by Bernard Sklar.
Contents2
4 sheets
Sheet 1 Sheet 2 Sheet 3 Sheet 4
50 members in 21 offices
Members50
| Document | Office | Kind | |
|---|---|---|---|
| CA2315065A1 | Canada | A1 | |
| WO9933204A1 | World Intellectual Property Organization (WIPO) | A1 | |
| AU2414999A | Australia | A | |
| EP0930734A1 | European Patent Office (EPO) | A1 | |
| WO9933204B1 | World Intellectual Property Organization (WIPO) | B1 | |
| EP0967744A1 | European Patent Office (EPO) | A1 | |
| NO20003157D0 | Norway | D0 | |
| NO20003157L | Norway | L | |
| HK1023237A1 | Hong Kong, China | A1 | |
| BR9813696A | Brazil | A | |
| TR200001785T2 | Türkiye | T2 | |
| EA200000670A1 | Eurasian Patent Organization (EAPO) | A1 | |
| CN1284223A | China | A | |
| KR20010024769A | Republic of Korea | A | |
| PL341200A1 | Poland | A1 | |
| IL136766D0 | Israel | D0 | |
| AU739074B2 | Australia | B2 | |
| AR017914A1 | Argentina | A1 | |
| EA002140B1 | Eurasian Patent Organization (EAPO) | B1 | |
| JP2001527319A | Japan | A | |
| EP0930734B1 | European Patent Office (EPO) | B1 | |
| AT215287T | Austria | T | |
| ATE215287T1 | Austria | T1 | |
| DE69711408D1 | Germany | D1 | |
| DK0930734T3 | Denmark | T3 | |
| PT930734E | Portugal | E | |
| ES2175256T3This record | Spain | T3 | |
| DE69711408T2 | Germany | T2 | |
| US6535546B1 | United States of America | B1 | |
| EP0967744B1 | European Patent Office (EPO) | B1 | |
| AT250303T | Austria | T | |
| ATE250303T1 | Austria | T1 | |
| DE69725012D1 | Germany | D1 | |
| DK0967744T3 | Denmark | T3 | |
| PT967744E | Portugal | E | |
| EP1385284A2 | European Patent Office (EPO) | A2 | |
| KR100417168B1 | Republic of Korea | B1 | |
| CA2315065C | Canada | C | |
| CN1149762C | China | C | |
| ES2207899T3 | Spain | T3 | |
| CN1505278A | China | A | |
| EP1385284A3 | European Patent Office (EPO) | A3 | |
| DE69725012T2 | Germany | T2 | |
| JP3554275B2 | Japan | B2 | |
| HK1062236A1 | Hong Kong, China | A1 | |
| IL136766A | Israel | A | |
| NO320227B1 | Norway | B1 | |
| PL192542B1 | Poland | B1 | |
| CN1327637C | China | C | |
| BR9813696B1 | Brazil | B1 |
1 legal event, as the office reported them to INPADOC
Events
| Event | Code | |
|---|---|---|
| Definitive protectionFG2A | FG2A |
Numbers
- Publication
- 2175256
- Application
- 97122421
Titles2
- Spanish
- METODO Y APARATO PARA DETERMINAR LAS CARACTERISTICAS DE LOS COMPONENTES DE UN CANAL DE COMUNICACION EN CARGA.
- English
- METHOD AND APPLIANCE TO DETERMINE THE CHARACTERISTICS OF THE COMPONENTS OF A LOADED COMMUNICATION CHANNEL.
Classification
- CPC, 4
- H04B7/18519
- H04B7/185
- H04B7/18513
- H04B17/346
- IPC, 4
- H04B7 185
- H04B7 26
- H04B17 00
- H04B17 40