IE65507B1 - Receiver apparatus for radiocommunication signals - Google Patents

Abstract

The reception apparatus according to the invention comprises a receiving antenna (1), a fixed-gain preamplifying element (2), an amplifying element (8) having a series of output lines (13) with fixed amplification levels connected to a common conversion element (20) by way of a sampling element (17), the conversion element (20) being associated with a storage element (21) and with a stored signals selection means (22) for transmitting to a digital processing unit (23) those of the stored signals having the amplification level best matched to the digital processing unit (23). <IMAGE>

Description

RECEIVER APPARATUS FOR RADIOCOMMUNICATION SIGNALS The present invention relates to receiver apparatus for receiving radiocommunication signals, and more particularly, but not exclusively, to receiver apparatus for a station in a radiotelephone network.

Radioccsnmunication apparatuses are known, in particular time multiplexing radiocommunication apparatuses, in which the signals to be transmitted are organised in the form of packets that are transmitted in succession over a radio channel.

Receive apparatuses for such signals generally comprise a receive antenna, a variable-gain preamplifier member connected to the receive antenna, a filter member connected to the preamplifier member, a variable-gain amplifier member connected to the output of the filter member, an analog/digital converter member having an input connected to the amplifier member and an output connected to a member for analyzing the converted signals and to a digital processor unit, the member for analyzing the converted signals being itself connected to a gain control member having an output connected to the preamplifier member and to the amplifier member. The gain control member serves to adapt the gain of the preamplifier and amplifier members to the power of the received signal. If the received signal is amplified too little, then the converted signal has too little energy to be processed properly by the digital processor unit, while if the received signal is amplified too much, it is clipped by the converter member which is thus prevented from performing its function. In order to ensure that the control system operates properly, the transmission must include a number of bits that suffices to enable the received level to be measured and gain to be corrected automatically.

Thus, when meaningful bits reach the amplifier system, its gain is properly adapted to the power of the signal and the signal is correctly processed by the digital processor unit.

Although automatic gain control systems have very short reaction times, such control systems are not adapted to receiving signals that do not contain an adequate number of bits that may be lost during the measurement process and during automatic gain correction. In this case, gain may be wrongly adapted and data may be lost.

An.object of the present invention is to provide receiver apparatus for receiving radioccmmunication signals, which * apparatus is adapted to processing signals for which insufficient time is available to proceed with gain correction.

In order to achieve this object, the present invention provides a receive antenna, a preamplifier and filter member connected to the receive antenna, an amplifier member connected to the output from rhe preamplifer and filter member, an analog-to-digitai converter member connected to the output from the amplifier member, and a digital processor unit connected to the converter member, in which the amplifier member includes fixed gain amplifiers connected in parallel, and between the converter member and the digital processor unit the apparatus includes storage means for storing signals at different levels of gain, and means for reading these signals, for selecting a level of gain which is adapted to the digital processor unit, and for transmitting the signals stored at said level of gain.

Thus, a received signal is stored simultaneously at different amplification levels such that reading from the memory, selecting that one of the stored signals which, corresponds to the most appropriate level of amplification, then transmitting said signals to the digital processor unit all take place after recaption and with sufficient time being available for relatively large amounts of processing. It may also be observed that the signal at the most appropriate level of amplification is selected for each packet received. The apparatus of the invention thus ensures that each packet received is forwarded to the digital processor unit at a substantially constant level even if the power level of the signal received at the receive antenna varies over time, whereas automatic gain control systems can only adapt smoothly to such variations.

In an advantageous version of the invention, the receiver device includes a converter member common to a plurality of amplifiers, said common converter member being connected to the associated amplifiers via a connection member which is controlled to establish connections cyclically between the common converter member and respective ones of the amplifiers.

Thus, while using a single converter member, the received signal is sampled at different levels of amplification.

In another preferred embodiment of the invention, the amplifier member includes a plurality of amplification stages in series, each comprising amplifiers connected in parallel in a generally pyramid-shaped structure.

Thus, high quality amplification is obtained while limiting the amplifier gain of each stage.

An embodiment of the invention is described by way of example with reference to the accompanying drawing, in which: Figure 1 is a block diagram of an embodiment of apparatus of the invention; and Figure 2 is a more detailed block diagram of a portion of the Figure 1 apparatus.

With reference to the figures, the receiver apparatus for 20 receiving radiocommunication signals in accordance with the invention comprises a receive antenna 1 connected to a preamplifier and filter member 2.

As can be seen in Figure 2, the preamplifier and filter member comprises a fixed gain preamplifier 3 whose output is connected to a bandpass filter 4. The output of the bandpass filter is connected to one input of a mixer 5 having another input connected to a local oscillator 6. The output from the mixer 5 is connected to a filter 7 centered on the frequency of the local oscillator 5 and having a wide passband equal in width to the passband of the signal to be processed.

The output from the preamplifier and filter member 2 is connected to an amplifier member 8 comprising a first amplifier stage having two fixed-gain amplifiers connected in parallel (see Figure 2). In the embodiment shown, one of the amplifiers 9 has a gain of g adapted to the most powerful signal that the installation is expected to receive, whereas the other amplifier 9 has a gain of g + 40 dB. The amplifiers 9 are followed by mixers 10 each having a first input connected to a respective one of the amplifiers 9 and a second input connected to a local oscillator 11 whose function is to perform frequency transposition in order to center the signal on a frequency Fb/2 where Fb is the bit frequency of the signal. Each of the mixers 10 is followed by a filter 12 for eliminating residues. The output from each filter 12 is connected in parallel to four output lines 13. In each group of output lines 13, one of the lines has no amplifier, a second line includes an amplifier 14 having a gain of 10 dB, a third line includes an amplifier 15 having a gain of 20 dB, and a fourth line includes an amplifier 16 having a gain of 30 dB, which amplifiers constitute a second amplification stage in the amplifier member 8. As a result, the output lines 13 provide levels of amplification spread over 0 dB to 70 dB of amplification relative to the input signal to the amplifier member 8.

The output lines 13 of the amplifier member 8 are connected to respective inputs of a sampler 17 including a series of connection means 18 connected in parallel and controlled by a control member 19 in order to establish connections cyclically between a common analog-to-digital converter member 20 and one of the lines 13 at a time. In the embodiment described, where the converter member is common to all levels of amplification, the sampling frequency is 2.Fb for each line 13, i.e. 16.Fb for the sampler so as to obtain meaningful sampling of the received signals.

The output from the converter member 20 is connected to an input of storage means 21 having another input connected to the control member 19 so that each sample received from the converter member 20 is given an address which corresponds to the line 13 associated with the stored sample. The storage means 21 are connected to stored signal selection means 22 which read all of the samples of a packet as stored at each level of amplification, and which select the most suitable level of amplification as a function of criteria given to the selection means, e.g. mean energy level or number of occasions on which clipping occurs.

In addition, the storage means 21 and the stored signal selection means 22 are connected to a digital processor unit 23 such that after determining the most appropriate level of amplification for the packet which has just been received, the stored signal selection means transmit information on this level of amplification to the digital processor unit and simultaneously causes the set of samples obtained at this level of amplification to be transferred from the storage means 21 to the digital processor means 23.

It may be observed that for each packet, amplification level is selected after all of the bits in a packet have been stored. Selection is thus performed not only on the nonmeaningful bits of a packet, but also on the meaningful bits, thereby ensuring that very high quality selection is obtained. Further, since selection is performed on each received packet, it is particularly well adapted even when the received signal level varies greatly from one packet to another.

Naturally the invention is not limited to the embodiment described and variants may be applied thereto without going beyond the scope of the invention. In particular, although the invention is described in association with an amplifier member 8 having eight output lines staggered over 10 dB intervals, the number of amplification levels should be adapted in each installation to the range of levels over which a signal is to be received.

Although the receiver apparatus of the invention is described with a common converter member associated with a sampling member, it would also be possible to fit each amplification level with its own converter, or to combine a plurality of converters, each associated with a plurality of amplification lines.

In addition, although the entire signal as amplified in the amplifier member 8 is centered on Fb/2, it would also be possible to decompose the received signal into I and Q components by means of a phase shifter, in which case the number of amplifiers in the second amplification stage would be doubled while the sampling frequency on each line 13 would be halved compared with the embodiment shown.

Claims (4)

1./ Receiver apparatus for receiving radiocommunication signals, the apparatus comprising a receive antenna (1), a preamplifier and filter member (2) connected to the receive antenna, an amplifier member (8) connected to the output from the preamplifer and filter member, an analog-to-digital converter member (8) connected to the output from the amplifier member, and a digital processor unit (23) connected to the converter member (20), the apparatus being characterized in that the amplifier member (8) includes fixed gain amplifiers (9; 14, 15, 16) connected in parallel, and in that, between the converter member (20) and the digital processor unit (23) the apparatus includes storage means (21) for storing digitalized signals at different levels of gain, and means (22) for reading these signals, for selecting a level of gain which is adapted to the digital processor unit (23), and for transmitting the signals stored at said level of gain.

2. / Receiver apparatus for radiocommunication signals according to claim 1, characterized in that it includes a converter member (20) common to a plurality of amplifiers, said common converter member being connected to the associated amplifiers via a connection member (17) which is controlled to establish connections cyclically between the common converter member (20) and respective ones of the amplifiers.

3. / Receiver apparatus for radiocommunication signals according to claim 1 or claim 2, characterized in that the amplifier member (8) includes a plurality of amplification stages in series, each comprising amplifiers (9; 13, 14, 15) connected in parallel in a generally pyramid-shaped structure .

4. Receiver apparatus for receiving radiotelecommunication signals according to Claim 1 and substantiallv as described herein with reference to, and as shown in, the accompanying drawings.