RADSOFREQUENCY SIGNAL RECEIVER DESIGNED TO BE INSTALLED
ON A SATELLITE
The invention relates to a radiofrequency signal receiver designed to
5 be installed on board a satellite. The invention notably relates to a satellite
remote control receiver also referred to as a TCR or TTC receiver, from the
acronyms for "Telemetry, Command and Ranging" and "Telemetry Tracking
and Command".
This type of TTC or TCR receiver is installed on board a geostationary
10 or non-stationary satellite and implements a TTC or TCR remote control link
between ground stations and the satellite.
The invention also relates to receivers for telecommunications signals
of the repeater type and to satellite miss-distance receivers designed to be
installed on board satellites.
15 A current need is to be able to know the spectrum of the signals
received by a receiver within a range of operating frequencies over which it
can operate when it is installed on board a satellite.
The knowledge of the spectrum can allow noise interference to be
detected and solutions for resisting noise interference to be implemented or
20 the reception frequencies of several satellites to be optimized during an
orbital position change.
One solution for tracing this spectrum consists in installing a spectrum
analyzer on board the satellite. The spectrum analyzer has the drawback of
being a unit of equipment which as such occupies a non-negligible volume on
25 the satellite. However, one challenge is to limit as far as possible the number
of units of equipment installed on board satellites. Furthermore, this unit of
equipment is complex and costly.
Another solution consists in analyzing, in a ground station, the power
of the signals sent back to this station by a repeater installed on board the
30 satellite. The satellite repeater receives uplink signals, amplifies them and
transmits downlink signals based on the amplified signals. This solution has
the following drawback: the uplink signals which are amplified and retransmitted
are, for example, useful telecommunication signals emitted within
predetermined frequency bands spaced out from one another. The signals
35 are re-emitted within the same bands or within other frequency bands also
spaced out from one another. The analysis on the ground does not allow the
2
spectrum between these bands of frequency to be known. !n other words, it
is not possible to know the power spectrum of the signals received by the
receiver over the entirety of the range of operating frequencies of the
receiver.
5 The aim of the invention is to overcome the aforementioned
drawbacks.
This objective is achieved by equipping a radiofrequency signal
receiver, designed to be installed on board a satellite:
10 - with a device for frequency controlling the receiver allowing the
reception frequency of the receiver to be adjusted based on a
frequency control,
- with a filtering assembly of the bandpass filter type having a
passband, referred to as passband of the filtering assembly, whose
15 width is adjustable and can take a set of vaiues, the filtering
assembly allowing the bandwidth of a first signal representative of
the input signal of the receiver to be limited to the passband of the
filtering assembly,
- with adjustment means allowing the width of the passband of the
20 filtering assembly to be adjusted based on a filtering passband
control,
- with power acquisition means allowing a measurement of the
power of the first signal to be delivered at the output of the filtering
assembly.
25 This solution offers a receiver which is capable of supplying power
spectra with different resolutions of an input signal of the receiver over
analysis bands corresponding to the operating frequency range or to subbands
of the operating frequency range while performing scannings of these
analysis bands with different step sizes and adjusting the width of the
30 passband of the filtering assembiy to a width equal to at least the selected
step size. !t therefore allows, by a suitable command of the control device
and of the adjustment means, the power of the signal received by the satellite
to be known in a continuous manner over any analysis band.
This solution also has the advantage of not requiring the
35 installation of a dedicated spectrum analyzer on board the satellite.
3
Furthermore, this receiver allows the same functions as a spectrum analyzer
to be carried out, namely the tracing of a spectrum exhibiting a higher or
lower resolution since it is possible to scan operating frequencies of the
receiver with several step sizes and to choose a passband width adapted to
5 the step size so as to obtain a continuous spectrum.
Advantageously, the receiver comprises a frequency conversion
chain assembly delivering at its output the first signal centered on a fixed
intermediate frequency, the frequency conversion chain assembly comprising
10 a first frequency conversion chain receiving the input signal from the receiver
and delivering at its output a first intermediate signal centered on a first fixed
intermediate frequency, the first frequency conversion chain comprising:
- a synthesized local oscillator design to deliver an output
signal from the oscillator at a frequency referred to as
15 oscillator frequency taken from amongst a set of
predetermined oscillator frequencies using a frequency
control,
- a mixer receiving the signal received at the input of the
receiver and the output signal from the oscillator and
20 delivering a first intermediate signal centered on a first
intermediate frequency.
Advantageously, the filtering assembly comprises at least one
25 bandpass filter, said bandpass filter being centered on the intermediate
frequency.
Advantageously, the filtering assembly comprises at least one
bandpass filter, said bandpass filter being a low-pass filter when the
intermediate frequency is equal to 0Hz.
30 Advantageously, the receiver is a remote control receiver.
Another subject of the invention is a set of receivers comprising a
nominal radiofrequency signal receiver and a redundant radiofrequency
signal receiver, the redundant receiver being a receiver according to the
invention.
4
Another subject of the invention is a satellite equipped with a
receiver according to the invention.
Another subject of the invention is a system for acquisition of a
power spectrum of an input signal of a receiver comprising a receiver
5 according to the invention and control means abie to generate and to send to
the receiver a set of power acquisition commands comprising successive
frequency commands sent to the control device, the frequency commands
being defined such that the control device adjusts the reception frequency of
the receiver to successive acquisition frequencies bounding and marking out
10 an acquisition frequency band and being spaced from one another by the
acquisition step size, the set of acquisition commands furthermore
comprising a filtering passband control sent to the adjustment means in order
to adjust the width of the passband of the filtering assembly to a
predetermined acquisition width while the control device adjusts the reception
15 frequency of the receiver to the successive acquisition frequencies.
In this way, the acquisition means deliver a power measurement
each time that the receiver adjusts its reception frequency to an acquisition
frequency, the power measurements being carried out over elementary
frequency bands having a width equa! to the acquisition width.
20 Advantageously, the control means are configured so as to
generate spectrum acquisition commands in which the acquisition width is
equal to at least the acquisition step size.
Advantageously, the control means are configured so as to
generate spectrum acquisition commands in which the acquisition width is
25 equal to the acquisition step size.
Advantageously, the control means comprise processing means
installed on board the satellite and are able to generate the set of spectrum
acquisition commands starting from a first set of commands previously
received by the onboard processing means and defining the acquisition
30 frequency band and the acquisition width and/or the acquisition step size.
Advantageously, the receiver is a redundant receiver.
Advantageously, the receiver comprises a demodulation circuit
allowing the signal to be demodulated, the demodulation circuit comprising
another bandpass filter allowing the noise frequency band of the first signal to
5
be limited, the filtering assembly being distinct from said other bandpass filter
Advantageously, the system comprises means allowing of envoyer
said power measurements to be sent simultaneously to a ground station from
5 the satellite.
Another subject of the invention is a method for acquisition of a
power spectrum of signals received at the input of a receiver, the method
being implemented by means of an acquisition system according to the
10 invention comprising a receiver according to the invention, in which a power
spectrum of signals received by said receiver is acquired by means of an
acquisition system according to the invention, over a predefined acquisition
frequency band, comprising:
- a step for generating and for sending the successive frequency
15 commands to the control device, by the control means, in such
a manner that the control device adjusts the reception
frequency of the receiver to successive acquisition frequencies
space out one from the next by the acquisition step size,
- a step for generating and for sending to the adjustment means,
20 by the control means, a filtering passband control equal to a
predetermined acquisition width,
- a step for adjustment of the width of the passband of the
filtering assembly to the acquisition width, by means of the
adjustment means,
25 - a scanning step, during which the control device adjusts the
reception frequency of the receiver to the successive
acquisition frequencies,
- and, each time that the receiver adjusts its reception frequency
to an acquisition frequency, a step for filtering the first signal by
30 means of the filtering assembly, and a step for acquiring, by
means of the power acquisition means, the power of the first
signal at the output of the filtering assembly.
Advantageously, the acquisition width is equal to at least the
acquisition step size.
Advantageously, the control means comprise processing means
installed on board the satellite capable of generating the set of spectrum
acquisition commands starting from a first set of commands defining the
acquisition frequency band and the elementary band width and/or the
5 acquisition step size, the method comprising a preliminary step for generating
and for sending the first set of commands to the processing means from a
ground station.
Advantageously, the method comprises a step for transmission of
the power measurements to a transmitter installed on board the satellite and
10 a step for simultaneously sending said measurements to a ground station.
Another subject of the invention is a method for optimizing the
reception frequency of the receiver comprising:
- at least one step for acquiring a spectrum according to the
acquisition method according to the invention,
15 - a step for identifying a frequency band verifying a
predetermined spectral quality criterion based on the power
measurements,
- a step for generating a frequency command designed to adjust
the reception frequency of the receiver to a frequency included
20 within the identified frequency band and a step for sending the
frequency command to the control device,
Other features and advantages of the invention will become
apparent upon reading the detailed description that follows, presented by
25 way of non-limiting example and with reference to the appended drawings in
which:
- figure 1 shows a block diagram of one example of a receiver
according to the invention,
- figure 2 shows a block diagram of a filtering assembly
30 according to the invention,
- figure 3 shows schematically a system for acquiring a spectrum
according to the invention,
- figure 4 shows the steps of a method for acquiring a spectrum
according to the invention.
7
From one figure to another, the same elements are identified by
the same references.
The subject of the invention is a radiofrequency signal receiver
5 that is flexible in frequency designed to be installed on board a satellite.
A 'receiver flexible in frequency' is understood to mean a receiver
having an adjustable operating frequency able to take a plurality of values
within a range of operating frequencies or any desired value within this
range. This type of receiver comprises control means, or a control device,
10 allowing the reception frequency of the receiver to be adjusted. This may be
a telecommunications receiver of the repeater type, a miss-distance receiver
for a satellite whose function is to orient a satellite antenna so that it points
toward a given point on the ground.
15 In one preferred embodiment, the receiver is a remote control
receiver such as previously defined. The remote control receiver already
incorporates a bandpass filter withn its ASIC having a width equal to the
width of the modulation that it receives (in other words to the width of the
bandwidth of the useful signal) with the aim of measuring the level of power
20 received: filters are readily added into the ASIC for the purposes of
measuring a spectrum.
Figure 1 shows a block diagram of a remote control receiver 1
according to the invention.
It comprises a frequency control device 100 allowing, based on a
25 frequency command, the adjustment of the reception frequency of the
receiver over the operating frequency range. The reception frequency FR is
the frequency on which the reception frequency window of the receiver is
centered. The range of operation of a radiofrequency receiver designed to be
installed on board a satellite is a wide band of the order of a GHz. For
30 example, in the Ku band, the range of operating frequencies of the receiver
extends between 13750 MHz and 14500 MHz.
This range of operating frequencies may be for example scanned
with a step size in the range between 100Hz and 100kHz during the
acquisition of a spectrum. This scanning may be carried out over all or a part
35 of the frequency range.
8
When the receiver scans an acquisition frequency band with an
acquisition step size, it adjusts its reception frequency FR to consecutive
frequencies of the analyzing frequency band spaced out one from the next by
5 the acquisition step size.
As can be seen in figure 1, the frequency control device 100 for
the receiver 1 receives a signal Se obtained at the input of the receiver and
delivers a first signal S1. The first signal corresponds to the input signal
obtained at the input of a receiver, when the latter is operating at the
10 reception frequency, this input signal being filtered, and amplified, and shifted
into an intermediate frequency. It should be noted that the intermediate
frequency may, for example, be equal to zero; this shift is then referred to as
conversion into baseband.
The control device comprises a frequency conversion assembly
15 delivering, at its output, a signal, referred to as intermediate signal Si, at a
predetermined (fixed) intermediate frequency Fl.
The frequency conversion assembly comprises a first frequency
conversion chain 101 delivering, at its output, a signal centered on a first
predetermined intermediate frequency FI1 which is fixed for the receiver.
20 The first frequency conversion chain 101 comprises:
- a synthesized local oscillator 103, for example a fractional
oscillator, designed to deliver an output signal So from the
oscillator at a frequency referred to as oscillator frequency FO
taken from amongst a predetermined set of oscillator
25 frequencies, based on a frequency command 104,
- a mixer 102 receiving the input signal Se from the receiver and
the output signal So from the oscillator 103 and delivering a
first intermediate signal Si1 centered on a first intermediate
frequency FI1.
30 In the embodiment in figure 1, the frequency conversion assembly
comprises a single frequency conversion chain which is the first frequency
conversion chain 101. The first intermediate frequency FI1 is therefore equal
to the intermediate frequency Fl and the first intermediate signal Si1 is the
intermediate signal Si.
9
Given that the intermediate frequency Fl is fixed, modifying the
frequency of the oscillator modifies the reception frequency of the receiver. In
the case where the conversion assembly comprises a single conversion
chain, the frequency scanning step size of the oscillator is furthermore equal
5 to the frequency scanning step size of the reception frequency. The reception
frequency is given by the following formula FR = FO ±FI. In other words,
scanning all of the oscillator frequencies allows the reception frequencies to
be scanned with the same step size.
As a variant, the frequency conversion assembly comprises a
10 plurality of frequency conversion chains. It then comprises at least a second
conversion chain, the second conversion chain receives, at its input, the
output of the first conversion chain.
The control device also comprises an assembly of filtering and
amplification circuits 105 allowing the signal at the output of the conversion
15 assembly chain 101 to be amplified and filtered and delivering, at its output,
the first signal s1.
The receiver furthermore comprises:
- a demodulation circuit 106 whose function is to demodulate the
signal at the output of the frequency conversion chain
20 assembly in order to recover the data included in the input
signal of the receiver,
- a filtering assembly 107 allowing the frequency band of the first
signal S1 to be limited to a predefined bandwidth.
25 The demodulation circuit 106 is generally speaking a circuit whose
function is to demodulate a first signal S1 representative of the input signal of
the receiver.
The filtering assembly 107 is of the bandpass filter type. It has an
adjustable passband, referred to as passband of the filtering assembly. The
30 filtering assembly 107 allows the bandwidth of the first signal S1
(representative of the input signal of the receiver Se) to be limited to the
passband of the filtering assembly.
The device furthermore comprises adjustment means, in other
words a device for adjusting the width of the passband 108a, 108b, which
35 can be seen in figure 2, allowing the width of the passband of the filtering
assembly to be adjusted using a filtering passband control 110. The
adjustment device can be, in the case of a digital filter, a register whose
coefficients are modified in order to modify the passband. In the case of an
anaiog filter, the adjustment device is, for example, a switching circuit.
5 In other words, the width of the passband of the filtering assembly
can take a set of values.
The filtering assembly 107 may comprise a single filter whose
bandwidth is adjustable by setting coefficients (case of digital filters). The
width of the passband may be adjustable in a continuous fashion or may be
10 able to take a plurality of predetermined discrete values. The controliing
means, in other words adjustment means, for such filters, for example a
register, act on the setting of coefficients.
It may also comprise a plurality of bandpass filters having
passbands of different widths. The adjustment means then comprise
15 selection means, in other words a selection device, for the filter toward which
the first signal S1 is oriented as in the example described hereinbelow.
As can be seen in figure 2, the filtering assembly 107 comprises a
plurality of bandpass filters 109j with i= 1 to N where N is equal to at least 2
20 and N = 3 in the example in figure 2. It also comprises adjustment means for
the width of the passband of the filtering assembly comprising first orientation
means 108a, in other words a first onentation device, allowing the first signal
S1 to be oriented toward a bandpass filter referred to as selected bandpass
filter, taken from amongst allot the bandpass filters based on a band-width
25 command 110. The adjustment means also comprise second orientation
means 108b, in other words a second orientation device, allowing only the
signal at the output of the selected filter to be transmitted toward the means
for measuring the power 111. The filtering assembly and the adjustment
means allow the bandwidth of the first signal S1 to be limited to the passband
30 of the selected bandpass filter depending on the required resolution. Here,
the means 108a and 108b are of the multi-position switch type. The
orientation devices are, for example, switching circuits.
The receiver also comprises power acquisition means 111, in
other words a power acquisition device, allowing a measurement of the
35 power of the first signal S1 to be delivered at the output of the bandpass
11
filtering assembly 107. The power acquisition device is for example an
analog power detection circuit or a processor in the digital case. In other
words, each time that the receiver adjusts its reception frequency to a
frequency of operation, the power acquisition means 111 carry out the
5 acquisition of the power received by the receiver over a frequency band of
width equal to the width of the passband of the filtering assembly such as
adjusted by the adjustment means.
The filtering assembly 107 is configured in such a manner that the
10 power measurement is representative of the power of the input signal, within
the bandwidth of the selected bandpass filter, centered on the reception
frequency of the receiver. For the embodiments in figures 1 and 3, this
implies that the bandpass filters are centered on the intermediate frequency
Fl if the intermediate frequency is not zero. In other words, the passbands
15 are centered on the intermediate frequency. In the case where the
intermediate frequency is zero, the filtering is carried out by bandpass filters.
The receiver according to the invention offers the possibility, by
carrying out a joint intelligent control of the control means and adjustment
means 108a, 108b for the bandwidth, of measuring the power spectrum of
20 the signal received by the receiver, over the entirety of its operating
frequency range in a continuous fashion and with several degrees of
precision or resolutions of analysts. The continuity of the spectrum is
obtained by adjusting the passband of the filtering assembly 107 over a band
width at least equal to the acquisition step size.
25 As a result, the receiver allows a true spectrum analyzer function
to be provided. By installing this type of receiver on board a satellite, it is no
longer necessary to install onboard equipment dedicated to the analysis of
this spectrum.
30 By scanning the range of operating frequencies of the receiver
with a predetermined acquisition step size and by choosing a bandwidth of
width equal to the scanning step size, a spectrum is formed that has as high
a resolution as possible for this step size. By scanning the band of operation
of the receiver with the scanning step size and by choosing a bandpass filter
35 of width greater than the scanning step size, a spectrum with a slightly lower
12
resolution, in other words smoothed or redundant, is obtained. It should be
noted that remote control receivers conventionally have a control device for
the frequency of the receiver, a bandpass filter and, potentially, means of
acquisition of the power over a band having the width of the bandwidth of this
5 filter. The bandwidth of the bandpass filter is of the order of 1MHz (for a
conventional frequency modulation receiver) which corresponds to the
bandwidth of the useful radio control signal which is sent to the receiver
under the normal conditions of use. However, this bandpass filter does not
allow a high-resolution spectral analysis to be carried out within the operating
10 frequency band of the receiver.
These frequency acquisition means allow the power of the useful
remote control signal received by the remote control receiver in the useful
frequency band of the receiver to be measured in order to verifier that the
level of the useful signal received is higher than a predetermined threshold.
15 The bandpass filter has a first function which is to limit the noise
band of the received signal in order to optimize the demodulation of the
useful signal. Its band width is the bandwidth of the useful signal. This
bandpass filter not shown is disposed in the demodulation chain 106.
According to the invention, the receiver comprises either at least
20 one additional bandpass filter, whose band width may be fixed or adjustable,
or a single bandpass filter but whose bandwidth is necessarily adjustable. In
the first case, the receiver according to the invention therefore comprises at
least one bandpass filter which is no ionger dedicated to the measurement of
the power of the useful signal but above all which is no ionger dedicated to
25 the limitation of the noise frequency band of the received signal in order to
optimize the demodulation of the signal. The additional bandpass filter whose
bandwidth is adjustable is dedicated to the tracing of a power spectrum. In
this first case, the bandpass filter allowing the noise frequency band to be
limited in order to optimize the demodulation of the first signal is incorporated
30 into the demodulation circuit 106. In this case, the bandpass filter whose
bandwidth is adjustable, in other words the filtering assembly 107, is distinct
from the bandpass filter included within the demodulation circuit 106. In other
words, the filtering assembly 107 is situated outside of the demodulation
circuit 106. The bandwidth of the bandpass filter which is integrated into the
35 demodulation circuit 106 is fixed. The receiver according to the invention
13
allows both the measurement of a power spectrum to be carried out and its
function for demodulating the received signal to be carried out.
Advantageously, the filtering assembly 107 is configured so as to
be able to have at least one passband with a width less than the bandwidth
5 of the useful signal sent to the receiver under the norma! conditions of use
and preferably in the range between 100 Hz and 100kHz.
Advantageously, the filtering assembly 107 has a passband with
an adjustable width able to take a set of values comprising a value at least 10
times lower than the width of the bandwidth of the useful signal. This feature
10 allows a spectrum to be obtained that has a good resolution by choosing this
passband width and by scanning the frequencies with a step size equal to
this passband.
Another subject of the invention is an assembly of receivers
comprising a nominal radiofrequency signal receiver and a redundant
15 radiofrequency signal receiver. The redundant receiver is intended to replace
the nominal receiver when the latter is defective. Advantageously, the
redundant receiver is the radiofrequency receiver. This feature allows, by a
suitable joint control using the control and adjustment means, the power
spectrum of the signals received by the receiver to be acquired, during or
20 outside of the operation of the receiver.
As a variant, the nominal receiver is a receiver according to the
invention. It is possible to acquire the power spectrum of the signals received
by the useful receiver only outside of the operation of the receiver, in other
words when the latter is not receiving remote control signals (in the case of a
25 remote control receiver).
Figure 3 shows a system for acquiring a power spectrum of the
signals received by a receiver according to the invention.
This system comprises:
- a receiver 1 according to the invention installed on board a
30 satellite 3,
- control means 2, in other words a control device, capable of
generating and of sending to the receiver 1 a set of commands for acquiring
a spectrum in order for the receiver to acquire power measurements over an
acquisition frequency band, corresponding to all or part of the operating
35 frequency band, by scanning said acquisition frequency band with an
acquisition step size, and by measuring, for each reception frequency of the
receiver, the power of the first signal over an elementary acquisition
frequency band having a width equal to an acquisition width taken from
amongst the passband widths that the filtering assembly can have. The set of
5 acquisition commands comprises successive frequency commands 104
successively sent to the control device, the control frequencies being defined
such that the control device 100 adjusts the reception frequency of the
receiver 1 to successive frequencies bounding and marking out the
acquisition frequency band and being spaced out one from the next by the
10 acquisition step size. The set of acquisition commands furthermore
comprises a filtering passband width command 110 corresponding to the
acquisition width.
The system comprises a communications uplink 4 between the
ground station 7 and the satellite 3 allowing the ground station 7 to send data
15 to the satellite 3. This could, for example, be the communications uplink
between the receiver 1 and a transmitter 8 situated in a ground station 7 or
between another receiver and a transmitter 8 situated in a ground station 7.
It also comprises a communications downlink 5 allowing a
transmitter 6 installed on board the satellite 3 to send data to the ground
20 station. The transmitter is, for example, a remote measurement TTC or TCR
transmitter situated on board the satellite 3. The transmitter is designed to
send data to a receiver 9 situated in a ground station 7.
Advantageously, the control means 2 are configured so as to
generate spectrum acquisition commands 104, 110 such that the acquisition
25 width is at least equal to the acquisition step size.
Advantageously, the control means 2 are configured so as to
generate spectrum acquisition commands in which the acquisition width is
equal to the acquisition step size, the receiver comprising a filter passband
equal to the acquisition step size. This allows a non-redundant power
30 spectrum to be obtained that is continuous over the acquisition frequency
band.
The control means 2 comprise processing means 10 installed on
board the satellite. These could, for example, be of a processor module
integrated into the receiver, a processing function or an onboard computer
15
installed on the satellite as shown in figure 3. In other words, the control
means comprise at least one processor 10.
The processing means 10 are capable of generating the set of
spectrum acquisition commands starting from a first set of commands 112
5 previously received by the processing means 10 and defining the acquisition
frequency band (for example the minimum frequency and the maximum
frequency) and a spectral resolution.
The resolution of the spectrum corresponds to the precision with
which the spectrum is to be generated, and this could, for example, be the
10 elementary band width. The processor then generates an acquisition step
size which is, at the most, equal to this band width. It could also be the
acquisition step size. The processor then generates a command for a width
of frequency band taken from amongst the band widths of the whole
assembly of bandpass filters at least equal to the step size. The first set of
15 commands may also comprise a command for the time at which the
processor is to start the acquisition of the spectrum.
Advantageously, the control means 2 comprise first means 11
installed in a control ground station 7 for generating the first set of commands
20 112, the first means being a first device, for example a processor, and this
first set of commands 112 being sent to the processing means 10 via the
uplink 4. The reception of these commands generates the acquisition of the
spectrum within the acquisition band defined on the ground, instantaneously
or at the time indicated. As a variant, the first means are installed on the
25 ground outside of the control station 7. They are connected to the control
station 7 via a ground link. These means could, for example, be a processor
installed in a SCC (satellite control center) where the remote control signals
destined for the receiver are generated and where the remote measurements
coming from the receiver are received. This SCC can be connected to the
30 control station 7 via a terrestrial network. The control station 7 receives the
control signals 112 via the network, modulates them and transmits them via
the link 4.
The generation of the frequency and filtering passband width
commands on board the satellite enables the acquisition of a spectrum to be
35 quickly carried out. Indeed, the successive frequency commands are not sent
directly from the ground station to the receiver or to an onboard computer
which would be very time consuming and constraining since this assumes
that the uplink will not be loaded when these commands are sent.
As a variant, the control means 2 are integrated into the ground
5 station. The set of acquisition commands is sent by the ground station to the
receiver via the uplink.
As a variant, the control means are integrated on board the
satellite.
Advantageously, the receiver 1 comprises transmission means, in
10 other words a transmission device, allowing the power measurements
acquired during the acquisition of the spectrum to be simultaneously sent to a
ground station from the satellite. These means advantageously comprise
means for storing data 12, in other words a memory, allowing of stocker the
measurements to be stored prior to sending it to the ground via the
15 transmitter. This allows the occupation of the bandwidth to be limited to the
minimum and the speed of the process to be increased.
Another subject of the invention is a method for acquiring a
spectrum from the signals received by the receiver by means of an
20 acquisition system according to the invention over an acquisition frequency
band corresponding to all or part of the operating frequency range of the
receiver. The method comprises, as can be seen in figure 4,
- a step 210 for generating and for sending successive frequency
commands to the control device, by the control means 2, in
25 such a manner that it adjusts the reception frequency of the
receiver to successive acquisition frequencies of the
acquisition frequency band spaced out one from the next by
the acquisition step size,
- a step 220 for generating and for sending to the adjustment
30 means, by the control means 2, a filtering passband control
equal to a predetermined acquisition width,
- a step 230 for adjusting the width of the passband of the
filtering assembly to the acquisition width,
17
- a scanning step, during which the control device adjusts 235
the reception frequency of the receiver to the successive
acquisition frequencies,
- and, each time that the receiver adjusts 235 its reception
5 frequency, to an acquisition frequency, a step 250 for filtering
the first signal by means of the filtering assembly 107, and a
step 260 for acquiring, by means of the power acquisition
means 111, the power of the first signal at the output of the
filtering assembly,
10
The method also comprises a step 240 for the transformation of
the signal received at the input of the receiver into a first signal S1 when the
receiver is such as that shown in figure 1.
During the scanning step, the receiver adjusts for example first of
15 all its frequency to the minimum frequency and increments its frequency with
the acquisition step size up to the maximum frequency.
The acquisition width is advantageously equal to at least the
acquisition step size. It is advantageously equal to the acquisition step size.
Advantageously, the method comprises a preliminary step for
20 generating and for sending 200 the first set of commands to the processing
means from a ground station. As a variant, the spectrum acquisition
commands are generated in a ground station and sent to the receiver from
the ground station.
At the end of the method, power measurements are obtained that
25 are representative of the power of the signals received by the satellite within
the acquisition frequency band over elementary analysis bands having a
width equal to the acquisition width and being centered around the operating
frequencies scanned by the receiver during this acquisition.
The measurement of the power of the ambient noise in the
30 environment of the receiver over the acquisition frequency band is therefore
obtained when the acquisition of the spectrum is carried out outside of the
periods of acquisition of a useful signal by the useful receiver and the power
measurement of the ambient noise, together with the power measurement of
the received signal when the measurement of the spectrum is carried out,
during the acquisition of a useful signal (here a remote control signal), by a
redundant receiver.
The method advantageously comprises a step 270 for
transmission of the power measurements to a transmitter installed on board
5 the satellite, for example a TTC transmitter, directly or via the processor
installed on board the satellite, and a step 280 for sending said
measurements to a ground station via the downlink 5. The measurements
are advantageously sent simultaneously to the ground station. These
measurements are then stored in memory 275 on board the satellite in the
10 storage means 12, and are sents at the same time to the onboard station.
This allows the occupation of the downlink to be limited.
The spectrum is obtained by normalizing these measurements in
spectral densities, in other words by transforming them into spectral power :
densities over elementary bands centered on the operating frequencies
15 scanned by the receiver during this acquisition and having a width equal to
the acquisition width. This operation is an operation well known to those
skilled in the art.
Advantageously, another subject of the invention is a method for
optimizing the frequency of the receiver based on the power measurements.
20 The use of the power measurements allows the optimum frequencies to be
identified, for example, those without noise interference, to which the
reception frequency of the receiver should be adjusted.
The method comprises:
- at least one step for acquiring a spectrum using the acquisition
25 method according to the invention,
- a step for identifying a frequency band verifying a
predetermined spectral quality criterion based on the power
measurements,
- a step for generating a frequency command designed to adjust
30 the reception frequency of the receiver to a frequency included
within the frequency band identified and a step for sending the
frequency command to the control device.
The method advantageously comprises a step for tracing the
spectrum (or spectra) over the acquisition frequency band based on said
measurements,
The spectral quality criterion can be a criterion for absence of
5 occupation or noise interference of a frequency band. Advantageously, this
band verifies a second bandwidth criterion which must be equal to at least
the width of the bandwidth of the useful signal to be sent to the receiver
under the normal conditions of use. The frequency command is defined such
that the control device adjusts the frequency of the receiver to the center of
10 the identified frequency band.
Advantageously, these steps are carried out in the ground station.
A frequency band without noise is for example a frequency band in
which the power spectral density is less than a predetermined threshold or a
frequency band in which the spectrum is in accordance with a reference
15 spectrum that the receiver is supposed to receive under the normal operating
conditions.
Advantageously, the method comprises a plurality of successive
steps for acquisition of the spectrum over the band. The identification of the
unoccupied frequency band or that without noise interference is carried out
20 using the various spectra. The tracing of several spectra allows for example
the maximum of the spectral density over a given period of time or else the
average of the spectral density over a given period of time to be calculated.

CLAIMS
1. A radiofrequency signal receiver (1) designed to be installed on board
5 a satellite comprising:
- a device (100) for frequency controlling the receiver allowing
the reception frequency of the receiver to be adjusted based
on a frequency command (104), characterized in that it
furthermore comprises:
10 a filtering assembly (107) of the bandpass filter type
exhibiting a passband, referred to as passband of the
filtering assembly, having an adjustable passband width
able to take a set of values, the filtering assembly (107)
allowing the bandwidth of a first signal (S1) representative of
15 the input signal of the receiver to be limited to the passband
of the filtering assembly,
- adjustment means (108a, 108b) allowing the width of the
passband of the filtering assembly to be adjusted using a
filtering passband control,
20 - power acquisition means (111) allowing a measurement of
the power of the first signal to be delivered at the output of
the filtering assembly (107).
2. The receiver as claimed in claim 1, comprising a frequency conversion
25 chain assembly delivering at its output the first signal (S1) centered on
a fixed intermediate frequency, the frequency conversion chain
assembly comprising a first frequency conversion chain (101)
receiving the input signal (Se) of the receiver and delivering at its
output a first intermediate signal centered on a first fixed intermediate
30 frequency, the first frequency conversion chain (101) comprising:
- a synthesized local oscillator (103) designed to deliver an
output signal (So) from the oscillator at a frequency referred
to as oscillator frequency taken from amongst a set of
predetermined oscillator frequencies based on a frequency
35 control (104),
21
- a mixer (102) receiving the signal received at the input of
the receiver (se) and the output signal from the oscillator
(103) and delivering a first intermediate signal (s1) centered
on a first intermediate frequency.
5
3. The receiver as claimed in claim 2, in which the filtering assembly
comprises at least one bandpass filter, said bandpass filter being
centered on the intermediate frequency.
10 4. The receiver as claimed in claim 2, in which the filtering assembly
comprises at least one bandpass filter, said bandpass filter being a
low-pass filter when the intermediate frequency is equal to 0Hz.
5. The receiver as claimed in any one of the preceding claims, in which
15 the receiver is a remote control receiver.
6. The receiver as claimed in any one of the preceding claims, having a
bandwidth with an adjustable passband width able to take a set of
values comprising a value at least 10 times lower than the width of the
20 bandwidth of the useful signal.
7. The receiver as claimed in any one of the preceding claims,
comprising a demodulation circuit (106) allowing the signal to be
demodulated, the demodulation circuit compnsing another bandpass
25 filter allowing the noise frequency band of the first signal to be limited,
the filtering assembly being distinct from said other bandpass filter.
8. A set of receivers comprising a nominal radiofrequency signal receiver
and a redundant radiofrequency signal receiver, the redundant
30 receiver being a receiver as claimed in any one of claims 1 to 7.
9. A satellite equipped with a receiver as claimed in any one of claims 1
to 7 or with a set of receivers as claimed in claim 8.
35 10.A system for acquiring a power spectrum of an input signal of the
receiver compnsing a receiver (1) as claimed in any one of claims 1 to
7 and control means (2) capable of generating and sending to the
22
receiver a set of power acquisition commands comprising successive
frequency commands (104) sent to the control device, the frequency
commands being defined in such a manner that the control device
adjusts the reception frequency of the receiver to successive
5 acquisition frequencies bounding and marking out an acquisition
frequency band and being spaced out from the next by the acquisition
step size, the set of acquisition commands furthermore comprising a
filtering passband control (110) sent to the adjustment means
(108a, 108b) in order to adjust the width of the passband of the
10 filtering assembly (107) to a predetermined acquisition width while the
control device adjusts the reception frequency of the receiver to the
successive acquisition frequencies.
11. System as claimed in the preceding claim, in which the control means
15 (2) are configured so as to generate spectrum acquisition commands
in which the acquisition width is equal to at least the acquisition step
size.
12.The system as claimed in the preceding claim, in which the control
20 means (2) are configured so as to generate acquisition commands in
which the acquisition width is equal to the acquisition step size.
13.The system as claimed in the preceding claim, in which the control
means (2) comprise processing means (10) installed on board the
25 satellite and being capable of generating the set of spectrum
acquisition commands starting from a first set of commands (112)
previously received by the onboard processing means (10) and
defining the acquisition frequency band and the acquisition width
and/or the acquisition step size.
30
14.The system as claimed in any one of claims 10 to 13, in which the
receiver is a redundant receiver.
15.The system as claimed in any one of claims 10 to 14, comprising
35 means (12) allowing said power measurements to be sent
simultaneously to a ground station from the satellite.
16. A method for acquiring a power spectrum, the method being
implemented by means of an acquisition system as claimed in any one
5 of claims 10 to 15 comprising a receiver as claimed in any one of
claims 1 to 7, in which a power spectrum of signals received by said
receiver is acquired over a predefined acquisition frequency band, the
method comprising:
- a step for generating and sending successive frequency
10 commands to the control device (210), by the control means, in
such a manner that the control device adjusts the reception
frequency of the receiver to successive acquisition frequencies
spaced out one from the next by the acquisition step size,
- a step for generating and sending (220) to the adjustment
15 means, by the control means, a filtering passband control
equal to a predefined acquisition width,
- a step (230) for adjusting the width of the passband of the
filtering assembly to the acquisition width by means of the
adjustment means (108a, 108b),
20 - a scanning step, during which the control device adjusts (235)
the reception frequency of the receiver to the successive
acquisition frequencies,
- and, each time that the receiver adjusts (235) its reception
frequency to an acquisition frequency, a step (250) for filtering
25 the first signal by means of the filtering assembly (107), and a
step (260) for acquiring, by means of the power acquisition
means (111), the power of the first signal at the output of the
filtering assembly.
30 17. The method as claimed in the preceding claim, in which the
acquisition width is equal to at least the acquisition step size.
18.The method as claimed in any one of claims 16 to 17, in which the
control means (2) comprise processing means (10) installed on board
35 the satellite capable of generating the set of spectrum acquisition
commands starting from a first set of commands defining the
24
acquisition frequency band and the elementary band width and/or the
acquisition step size, the method comprising a preliminary stepl(200)
for generating and for sending the first set of commands to the
processing means (200) from a ground station.
5
19. The method as claimed in any one of claims 16 to 18, comprising a
step for transmission of the power measurements to a transmitter
installed on board the satellite and a step for simultaneously sending
said measurements to a ground station.
10 . .
20.A method for optimizing the reception frequency of the receiver
comprising:
- at least one step for acquiring a spectrum according to the
method of acquisition as claimed in any one of claims 16 to 19,
15 - a step for identifying a frequency band verifying a
predetermined spectral quality criterion based on the power
F measurements,
f - a step for generating a frequency command designed to adjust
the reception frequency of the receiver to a frequency included
20 within the identified frequency band and a step for sending the
frequency command to the control device.