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(11) | EP 2 073 306 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Antenna pointing aid device and method |
| (57) In an antenna pointing system, audio feedback to the operator is established by making
use of an existing RF channel in the return path, e.g. an existing RF on/off channel
(TDMA) in the return path. During antenna pointing, the return channel RF cable (52)
or other connection means is disconnected from the transmitter input of the outdoor
unit and is connected to a unit including an audio module (8). A demodulator such
as an AM demodulator is required in the outdoor unit. In one aspect of the present
invention, an indication for antenna positioning is based on a quality property of
the signal received from the satellite, e.g. a received signal strength, until receiver
lock on the forward signal. After this step, the indication is based on signal to
noise ratio.
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[0001] The present invention relates to antenna pointing especially during installation of terminals, e.g. in a two-way satellite communication network, for example, a consumer satellite reception system equipped with a return channel, as well as to an antenna Pointing Aid Device. The present invention also relates to a reception system including the antenna pointing device.
TECHNICAL BACKGROUND
[0002] Satellite communication systems require accurate pointing of the ground antenna in the direction of the satellite. It is known that a pointing accuracy of around 1 to 2° is required. It is also known that for bidirectional systems, i.e. with a transmitter, the pointing must be more accurate. In such a case a more accurate pointing is needed of around 0.1 °. The alignment is generally done manually. It is also known that information representing the received strength is needed to perform this type of adjustment.
[0003] During installation of terminals, for example, in a two-way satellite communication network, a single installer at the antenna (which is probably outdoors or at a first location) can preferably adjust azimuth and elevation of the antenna dish without assistance of someone at the indoor unit (indoors or at a second location), thus shortening installation time and cost, without compromising pointing accuracy. In known solutions the ratio of the measured signal from the antenna to noise (or signal strength) at the receiver is an indication of the pointing correctness. This information is to be transmitted to the installer at the antenna in some way so that the pointing of the antenna can be optimised. Known solutions use the return channel RF cable for this purpose. For example, an extra audio generator can be provided in the indoor unit, whereby the audio signal is either switched with operational return signal or added with the return signal. At the outdoor unit and AC coupled headphones can be used to hear the audio signal and hence to adjust the antenna in accordance with the audio signal. One disadvantage of this arrangement is the extra cost for the indoor unit, with possibly an additional disadvantage being limited audio bandwidth.
SUMMARY OF THE INVENTION
[0004] The present invention has as an object to provide an alternative antenna pointing method especially during installation of terminals, e.g. in a two-way satellite communication network, as well as an antenna Pointing Aid Device. In particular, an object is to reduce the amount of additional equipment needed and/or expense of prior art solutions.
[0006] The present invention provides a radio frequency reception system comprising:
an indoor unit equipped with a reception unit and means for measuring a quality property of a received signal, an outdoor unit linked to the indoor unit by a communication path, the outdoor unit, an adjustable antenna, adjustment means for adjusting the positioning of the antenna, and an first audio module for providing an operator with a signal representative of the quality property of a received signal, the reception unit having a memory for storing a last best value of the quality property of a received signal, means for comparing the last best value with a current value, and a second audio module for generating at least two tones, the second audio module being adapted to generate a first tone when the quality signal is better than the last best value and a second tone when the quality signal is worse than the last best value or when the quality signal is below a certain threshold underneath the last best value, wherein the first tone is provided as a continuous audio tone and the second tone is provided as discontinuous or bursty audio tone, and a transmission unit for transmitting the first or second tones along the communication path to the first audio module in the outdoor unit.
[0007] The transmission unit is preferably adapted to provide the first or second tone as an AM modulated carrier on the communication path, for example the communication path can be linked to a satellite return channel.
[0009] The present invention also provides a method of assisted positioning of an antenna in a reception system, comprising:
generating a first tone having a property giving an indication of a signal quality of a signal received by the reception system, wherein the first tone is provided as a continuous audio tone,
storing at each moment of time a value of the last best signal quality,
comparing a current signal quality with the stored last best value,
generating a second tone when the current signal quality is worse than the last stored best value, or when the quality signal is below a certain threshold underneath the last stored best value, wherein the second tone is provided as a discontinuous or bursty audio tone and
making a rough adjustment in accordance with at least the first tone.
[0010] The method may also comprise fixing the azimuth and elevation of the antenna, and making fine adjustments to the antenna pointing by small elastic direction adjustments in azimuth and/or elevation directions.
[0011] The may also comprise making a series of rough adjustment including freely moving the antenna while receiving the first and/or second tone.
[0012] The first tone is preferably amplitude- and/or frequency-modulated according to the measured quality of the received signal. Further the second tone is preferably audibly distinct from the first tone.
[0013] In one aspect of the present invention, the audio feedback is established by making use of an existing RF channel in the return path, e.g. an existing RF on/off channel (TDMA) in the return path. During antenna pointing, the return channel RF cable or other connection means is disconnected from the transmitter input of the outdoor unit and is connected to a unit including an audio module. A demodulator such as an AM or FM demodulator is required in the outdoor unit. No additional hardware is required in the indoor unit. In one aspect of the present invention, an indication for antenna positioning is based on a quality property of the signal received from the satellite, e.g. a received signal strength, until receiver lock on the forward signal. After this step, the indication is based on signal to noise ratio.
[0014] In a particular embodiment of the present invention, the audio signal is transmitted as an AM or FM modulated RF carrier on the return path which differs from the existing solutions in which the audio is coupled in/out on the signal path.
[0015] In a further embodiment of the present invention, a pointing procedure is provided comprising:
First, a first tone is generated, e.g. a continuous audio tone is generated, the pitch being an indication of the signal quality received by the antenna. Decreasing or increasing frequency of the tone (lower or higher pitch within the audio band) indicates better pointing, i.e. a received signal of higher quality. At each moment of time the best signal quality until that time point is kept in memory, and each new value is compared with the stored value. When the actual quality drops below the last stored best value (e.g. optionally within a certain threshold), a second tone is generated, e.g. the tone becomes discontinuous or bursty. Only when the last best value has been reached (or exceeded) again, does the second tone revert to being the first tone, e.g. becomes continuous again. In a further embodiment, when the installer achieves more or less correct pointing (e.g. the tone is the first tone being continuous), he/she fixes the azimuth and elevation fixing devices, e.g. bolts.
[0016] Then, the dish is pushed a little back and forth in elastic deflections in both azimuth and elevation directions. If a better a pointing exists, the first tone will change, e.g. decrease or increase in frequency during one of these actions, and will assume the second tone; e.g. become bursty when the dish is released again. The installer now knows in which direction the dish pointing is to be fine tuned in order to improve the signal quality.
[0017] As indicated above the present invention provides a method of storing or 'clamping' of the best signal quality at any moment up to a current time, and communicating deviations from this last best signal to the installer (e.g. continuous and/or bursty tones).
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The invention will be better understood, and other particular features and advantages will emerge on reading the description that follows, the description referring to the appended drawings in which:
Figure 1 represents a satellite reception system as used with embodiments of the present
invention.
Figure 2 represents an indoor reception unit as used with embodiments of the present
invention.
DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
[0019] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are nonlimiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.
[0020] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
[0021] Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.
[0022] It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
[0023] Similarly, it is to be noticed that the term "coupled", also used in the claims, should not be interpreted as being restricted to direct connections only. Thus, the scope of the expression "a device A coupled to a device B" should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means.
[0024] The present invention has an RF reception system which comprises an indoor unit equipped with reception means and means for measuring a quality property of the received signal, e.g. a received signal strength, an outdoor unit linked to the indoor unit by at least one communication means such as a coaxial cable, and mechanical adjustment means for adjusting the positioning of the antenna.
[0025] An audio signal generator is placed in the indoor unit which generates audio tones of at least two types for sending to the operator who is adjusting the antenna. The nature of the at least two tone types depends upon the quality value of quality property of the received signal, e.g. according to a measured signal strength. At the outdoor unit the operator is able to receive the audio signals. For this purpose the outdoor location has an additional module including an audio module. The audio module can include an audio signal reproduction device such as a headset and a suitable connection to be linked to the indoor unit. The connection can be provided in an existing satellite return channel.
[0026] The invention also includes a method of antenna positioning in which one or more rough adjustments are made to obtain a rough pointing of the antenna, followed by a series of fine adjustment steps in which the operator makes small movements to the antenna pointing direction from the rough pointing to determine an optimum setting.
[0027] During the one or more rough adjustment steps, the operator can move the antenna freely while receiving information representing the quality of the received signal, e.g. a received signal strength. The information representing the strength of the received signal can be a sound amplitude- and/or frequency of a first audio tone, e.g. a continuous tone according to quality of the received signal, e.g. the strength of the received signal.
[0028] During all adjustment steps, the quality value, e.g. the last best received signal strength measurement is automatically stored. Adjustment steps can comprise the following:
rotation by a quantity in azimuth and/or elevation relative to the position corresponding to a first adjustment in a first direction and listening to the first tone of the audio signal as to whether it indicates and improvement in quality or whether it changes to a second tone,
rotation by a quantity in azimuth and/or elevation relative to the position corresponding to the first adjustment in a second direction different from the first direction and listening to the first tone of the audio signal as to whether it indicates and improvement in quality or whether it changes to a second tone,
repeating of the above steps as required to determine a new position of the antenna. Optionally repeating these steps until any movement of the antenna results in a change from the first to the second tone, being indicative of an optimum position.
[0029] Figure 1 shows a satellite reception system which comprises an antenna 1 which includes an outdoor unit 2, an indoor reception unit 3 which converts the received signal into a useful signal for a user equipment 4, an outdoor transmission unit 9, a return channel unit 16 and at least one communication link 5 linking the outdoor unit 2 and the indoor unit 3. The communication link 5 can comprise a cable such as a coaxial cable. The system is bidirectional and therefore also has an existing satellite return channel. Figure 1 shows the arrangement for antenna pointing adjustment. There is a coaxial cable 52 for reception and a coaxial cable 54 for transmission in normal operation of the satellite system. The coaxial cable 54 is also doubles up for use during the adjusting of the positioning of the antenna to reduce the number of cables used. So according to the invention, the cable 54 is disconnected from the outdoor transmission unit 9/antenna 1 and is connected to an outdoor audio module 8 instead of to the outdoor transmission unit 9 or a return channel terminal of the antenna 1. This may be achieved by a switch 17 or manually.
[0030] The indoor reception unit 3 includes, for example, a return channel, e.g. for interactive programs. The indoor reception unit 3 may comprise a reception unit 14, the return channel unit 16 and an audio signal generator module 7. An optional switch 18 may be provided to switch from the return channel unit 16 to the audio signal generator module 7 or this switching may be done manually. Most of the indoor reception unit 3 can be the similar to known reception units in principle and will not be described further in detail. Generally, as shown schematically in Figure 2, the indoor reception unit 3 will include a power supply 12, a processing engine 20 such as a microprocesor, a microcontroller, an FPGA etc. having a memory 22 and a processor 24 enabling it to perform control and processing functions. The indoor reception unit 3 can include a bandpass filter 26 for filtering out signals from the signal received from the satellite along communication link 5. These signals are then transposed to baseband and demodulated by a demodulator 28 into a bit stream for supply to user equipment 4. The processing engine 20 is adapted, e.g. programmed, to generate a signal relevant to the quality of the received signal such as received signal strength or any other signal that may be used as a measure of the quality of the receive path such as bit error rate, frame error rate, symbol error rate, etc.
[0031] The audio signal generator module 7 of the indoor reception unit 3 is in communication with the processing engine 20 and is adapted to generate at least two audio tones as well as to modify these tones, e.g. change their frequency depending on the signal relevant to the quality of the received signal such as the received signal strength or any other signal that may be used as a measure of the quality of the receive path. In particular the audio signal generator module 7 is adapted to receive the quality signal from the processing engine 20 and to generate electrical signals of at least a first and a second audio tone. The first tone may be a continuous tone and the second tone may be a discontinuous tone, e.g. a bursty tone. The audio signal generator module 7 can be adapted to alter a property of the tone, e.g. the frequency of the audio tone it generates and to alter the property, e.g. the frequency depending upon the value of the quality signal it receives. A memory 22 of the indoor reception unit is used to store the last best value of the quality signal at any moment. For this purpose the processing engine 20 may be adapted to write the last best value of the quality signal into the memory 22. The processing engine 20 is also adapted to read the last best value from the memory 22 and to compare a current value of the quality signal with the read-out last best value of the quality signal and to provide the audio signal generator module 7 with a first signal when the current value is better than (or optionally the same as) the stored value and a second signal when the value is the worse than (or optionally the same as) the stored value. The audio signal generator module 7 is adapted to generate electrical signals for the first tone when it receives the first signal from the processing engine 20, e.g. a continuous tone and to generate electrical signals for the second tone when the second signal is received. The processing engine 20 is adapted to generate the first signal modified in a suitable way (e.g. as a digital signal or an analog signal with varying amplitude) in accordance with a value of a property that is related to the quality of the received signal. The audio signal generator module 7 is adapted to change a characteristic of the first tone in accordance with the value of the property of the first signal, e.g. to change the frequency of the first tone upwards (or downwards) when the quality improves and to change the frequency of the first tone downwards (or upwards) when the quality decreases.
[0032] In normal operation, the return channel unit 16 is designed to provide a signal for transmission to the satellite. The return channel unit 16 can comprise a modulator 30 which receives a bit stream and modulates it in the baseband. The modulated signals are then transposed and filtered (32) and supplied to the cable 54 for transmission to the outdoor transmission unit 9 and antenna 1 and from there to the satellite.
[0033] During antenna positioning, an indoor transmission unit 11 is adapted to receive the audio signal from the audio module 7 and to impose this on a carrier in the return channel as an AM modulated RF carrier on the return channel. This AM modulated signal is received at the audio module 8 of the outdoor unit 2 where it is demodulated and converted into an audible sound in an audio reproduction device such as a headset. FM modulation could be used.
[0034] The above system is used as follows. Firstly, the indoor reception unit 3 is set the pointing mode as shown in Figure 1. The operator can connect the indoor audio signal generator module 7 and the outdoor audio module 8 to the cable 54.
[0035] The antenna 1 is equipped with fixing means to secure the antenna 1 in a given position. An antenna adjusting device 32 is provided that secures the antenna 1 and has a means for adjusting the position of the antenna in azimuth and in elevation. The operator positions the antenna 1 and can adjust its position using the antenna adjusting device 32.
[0036] The operator begins the operation by setting the position of the antenna roughly towards the satellite. In one aspect of the present invention, an indication for antenna positioning is based on a quality property of the signal received from the satellite, e.g. a received signal strength, until receiver lock on the forward signal. After this step, the indication is based on signal to noise ratio. The processing engine 20 controls the indoor reception unit 3 to receive a channel of the satellite (e.g. as known in advance). The received signal, e.g. the demodulated received signal is measured periodically, to measure the quality property of the received signal, e.g. the received signal strength. For each measurement, the processing engine 20 creates either the first or second signal as disclosed above. The indoor audio signal generator module 7 receives the first or second signal and generates a first or second tone, respectively, e.g. either continuous or bursty, i.e. with a frequency and amplitude dependent on the value of the first and/or second signal from the processing engine. This audio signal is supplied to the indoor transmission unit 11 for transmission along the return path as an AM modulation of a carrier. FM modulation could also be used. For example, the stronger the received signal strength, the higher the frequency of the first tone signal generated and the greater its amplitude. The AM (or FM) modulated carrier is received at the outdoor audio module 8 and demodulated into audible sound, and reproduced e.g. in a headset. The operator moves the antenna continuously trying to obtain an audio signal in the head set indicative of a better quality, e.g. the loudest and/or most high-pitched or low-pitched sound. Every time the signal changes from the first tone to the second tone, the operator knows that the antenna has passed through a local or global maximum of signal quality. Once the operator has confirmed that the antenna position is close to a quality maximum, the operator fixes the antenna.
[0037] Next the operator does the fine antenna positioning. The operator gives the antenna a small movement, e.g. a nudge or an elastic displacement or a small movement of the adjusting screws. If the tone changes from the first to the second tone, the operator knows that this movement makes the signal worse. The operator pushes or adjusts the antenna direction sequentially in a plurality of different directions in azimuth and elevation starting from the initial fixed position. If a directional change is found that improves the first tone the operator may make a change in the direction of the antenna. When the movement has been made, the storage of the quality signal, e.g. the received signal strength with this new position, is done in the indoor reception unit 3 automatically. There is no need for the operator to press a button once the movement has been made in order to store the latest best value of received signal strength.
an indoor unit equipped with a reception unit and means for measuring a quality property of a received signal,
an outdoor unit linked to the indoor unit by a communication path, the outdoor unit, an adjustable antenna,
adjustment means for adjusting the positioning of the antenna, and
an first audio module for providing an operator with a signal representative of the quality property of a received signal, the reception unit having a memory for storing a last best value of the quality property of a received signal, means for comparing the last best value with a current value, and
a second audio module for generating at least two tones, the second audio module being adapted to generate a first tone when the quality signal is better than the last best value and a second tone when the quality signal is worse than the last best value or when the quality signal is below a certain threshold underneath the last best value, wherein the first tone is provided as a continuous audio tone and the second tone is provided as discontinuous or bursty audio tone, and
a transmission unit for transmitting the first or second tones along the communication path to the first audio module in the outdoor unit.
generating a first tone having a property giving an indication of a signal quality of a signal received by the reception system, wherein the first tone is provided as a continuous audio tone, storing at each moment of time a value of the last best signal quality, comparing a current signal quality with the stored last best value, generating a second tone when the current signal quality is worse than the last stored best value, or when the quality signal is below a certain threshold underneath the last stored best value, wherein the second tone is provided as a discontinuous or bursty audio tone and making a rough adjustment in accordance with at least the first tone.