RADIOFREQUENCY DEVICE

Abstract

A radiofrequency device includes at least the following elements: an antenna, linked to a first transmission channel or reception channel selection device K.sub.1, followed by a front-end stage whose output is linked to a second transmission channel or reception channel selection device K.sub.2, a group of filters connected between the second selection device K.sub.2 and a third transmission channel or reception channel selection device K.sub.3, the third selection device K.sub.3 is connected to a transceiver, the transceiver comprises a converter part, wherein the group of filters comprises N filters having distinct frequency bands B.sub.N in a given bandwidth B.sub.T, the group of filters is linked to a manager selecting at least one of the filters Fj of the group of filters in order to attenuate a first type of disturbing signals P.sub.1, in the vicinity of the centre frequency of the channel to be received, the transceiver comprises a stage comprising a variable filter, the variable filter is configured in order to eliminate a second type of disturbing signals P.sub.2, the stage is connected between the group of filters and the analog-digital and digital-analog conversion set, the number N of filters of the group of filters is chosen by taking into account the operating frequency band value of the antenna, the value of a selected bandwidth Bc and a coefficient δ taking into account overlap effects.

Claims

1. A radiofrequency device comprising at least the following elements: an antenna, linked to a first transmission channel or reception channel selection device K.sub.1, followed by a front-end stage whose output is linked to a second transmission or reception channel selection device K.sub.2, a group of filters connected between the second selection device K.sub.2 and a third transmission channel or reception channel selection device K.sub.3, the third selection device K.sub.3 is connected to a transceiver, the transceiver comprising an analog-digital and digital-analog converter part wherein: the group of filters comprises N filters having distinct frequency bands B.sub.N in a given bandwidth B.sub.T, the group of filters is linked to a manager adapted for selecting at least one of the filters Fj of the group of filters in order to attenuate a first type of disturbing signals P.sub.1, in the vicinity of the centre frequency of the channel to be received, the transceiver comprises a stage comprising a variable filter, the variable filter is configured to eliminate a second type of disturbing signals P.sub.2, said stage is connected between the group of filters and the analog-digital and digital-analog conversion set, the number N of filters of the group of filters is chosen by taking into account the operating frequency band value Bt of the antenna, the value of a selected channel width Bc and a coefficient δ taking into account overlap effects.

2. The device according to claim 1, wherein the filters of the group of filters are filters configured to perform a narrow filtering function in a reduced bulk.

3. The device according to claim 2, wherein the filters of the group of filters are chosen from the following list: surface acoustic wave SAW filters or bulk acoustic wave BAW filters.

4. The device according to claim 1, wherein the filter characteristics of the group of filters are chosen in order to process signals lying within the very high frequency VHF band.

5. The device according to claim 1, wherein the characteristics of the filters of the group of filters are chosen in order to process signals lying within the ultrahigh frequency UHF band.

6. The device according to claim 1, wherein the antenna is an antenna comprising a transmission channel and a reception channel.

7. The device according to claim 1, comprising an antenna filter configured to filter a signal S.sub.r, an amplifier adapted for amplifying the filtered signal S.sub.1 before transmission to the group of filters, of which one of the filters is selected and activated in order to filter by at least 30 dB the spurious signals in transmission situated at more than 10 MHz from the frequency of the filter, a first amplifier adapted for amplifying the second filtered signal S.sub.2, a demodulator IQ of the second signal S.sub.2, a phase splitter and a phase locked loop generating a signal mixed with the second filtered signal before a third variable frequency filter, of which the centre frequency F.sub.3 is chosen in order to eliminate the disturbing signals of the order of 1 MHz to 10 MHz from the reception channel.

8. The device according to claim 1, comprising a transmission channel comprising two analog-digital converters ADC each linked to a first filter, with variable frequency configured to filter the replicas linked to the converters, two amplifiers, one amplifier being connected to an output of a first filter, a phase splitter and a phase locked loop delivering a mixed signal with the two signals from the amplifiers, a filter of the group of filters selected and activated by the manager in order to filter spurious signals from +/−8 MHz to plus or minus several hundreds of MHz before transmission to the transmission part of the antenna.

9. The device according to claim 1, wherein the variable filter and IQ modulation/demodulation stage and the converters are disposed on one and the same component.

Description

[0027] Other features and advantages of the present invention will become more apparent on reading the description of an exemplary embodiment given in an illustrative and nonlimiting manner, with attached figures which represent:

[0028] FIG. 1, a filtering plan for an RF band transceiver according to the prior art,

[0029] FIG. 2, an architecture known from the prior art,

[0030] FIG. 3, an example of a block diagram of the architecture according to the invention, and

[0031] FIG. 4, an example of a filtering plan for a UHF band receiver.

[0032] The example detailed hereinbelow is given by way of illustration in order to give a good understanding of the architecture according to the invention. The architecture according to the invention is not limited to the example detailed hereinbelow. The invention is applicable to other embodiments which can be put into practice or produced in different ways.

[0033] FIG. 3 illustrates a block diagram of an example of an architecture according to the invention for a single-channel use. The system according to the invention comprises a reception and/or transmission antenna 30 linked to a first transmission channel or reception channel selection device K.sub.1, followed by a front-end stage 31 whose output is linked to a second transmission channel or reception channel selection device K.sub.2, which is itself linked to a set or group of several filters 32, connected to a transmission channel or reception channel selection device K.sub.3. The third selection device K.sub.3 is connected to an RF transceiver, or simply “transceiver”, 33, comprising a channel for processing the reception signals and a channel for processing the transmission signals.

[0034] The antenna 30 comprises a transmission channel 30b and a reception channel 30a. It is configured to receive and transmit a radiofrequency RF radiation in a frequency band specified by the application, which at least partly overlaps the frequency bands of the group of filters and the bandwidths of the ADC and DAC converters.

[0035] Considering the reception channel, a signal Sr is received on the antenna 30. The signal is first of all filtered by an antenna filter 310 to a first frequency F.sub.1, the filtered signal S.sub.1 is then amplified by an amplifier 311, before transmission to the group of filters 32. The group of filters comprises N filters 320.sub.1 . . . 320.sub.N. Like the filters used in the intermediate frequency stages on the superheterodyne architectures, each filter performs the disturbing signal filtering function, attenuating by at least 30 dB the signals which would be located at approximately ten or so MHz to several hundreds of MHz from the useful signal. The centre frequency Fc of each of the filters, and their bandwidth B, allows all the frequency band that is wanted to be received on the antenna to be covered. An overlap in the bandwidth of the filters is necessary in order to receive or transmit in all the channels. The intermediate frequency stage then becomes unnecessary, the bank of filters performing this function for all the frequencies that are wanted to be transmitted or received. The group of filters receives a command from a manager 35 which selects a filter to be used as a function of the channel that it is wanted to be received or transmitted. With the filter being selected and activated at a centre frequency F.sub.2, all the disturbing signals in the reception or all the spurious signals in transmission which will be located more than a given frequency value a, for example 10 MHz, from the frequency of the filter will then be filtered by at least β, for example 30 dB. The filtered signal S.sub.2 is transmitted to the transceiver 33. The filtered signal S.sub.2 is amplified in a first amplifier 331. After this amplifier, the signal S.sub.2 passes through an IQ demodulator. It is then mixed, M.sub.1, M.sub.2, with a signal S.sub.90 from a phase splitter and a phase locked loop 350, before being transmitted to a second amplifier 332, 334, then filtered by a third variable frequency filter 333, 335, whose centre frequency F.sub.3 will be chosen so as to eliminate the disturbing signals very close (of the order of from 1 MHz to 10 MHz) to the channel that is wanted to be received. The filtered signal S.sub.3 is then transmitted to a digital-analog converter, DAC.

[0036] The antenna filter 310 is chosen to operate in a frequency band [F.sub.Min, F.sub.Max] determined by the application.

[0037] The number N of filters that make up the group of filters is determined, for example, by taking into account the total receiver band Br divided by the channel width Bc and by multiplying by a coefficient δ, for example equal to two in order to take account of the overlap effects, a phenomenon known to the person skilled in the art which will not be explained.

[0038] The group of wide channel filters (bank of SAW filters) allows protection from the near and far interfering signals (˜10 MHz to 100 MHz): these are the strongest disturbing signals which require a filtering before passing into the RF transceiver.

[0039] The narrow band filtering is performed by the variable filter of the RF transceiver: the latter contains a tunable analog filtering allowing a narrow filter to be produced for the very near disturbance signals (˜2 MHz to 10 MHz).

[0040] To illustrate the architecture according to the invention, a numbered example will be given for operation in reception.

[0041] Considering a total band Bt at the receiver of [225 MHz-400 MHz]. The characteristics of the first antenna filter (centre frequency, for example) are determined so as to eliminate the disturbing signals present outside of the [225 MHz-400 MHz] band. Considering also that the signal to be received is located at a frequency Fs of 260 MHz with a bandwidth of 2.5 MHz, the second filter F.sub.2 selected in the group of filters is configured with a centre frequency F.sub.c2 adapted for allowing the 260 MHz+/−1.25 MHz channel while offering an attenuation of 30 dB at +/−8 MHZ from 260 MHz in order to eliminate the disturbing signals located between +/−8 MHz and plus or minus several hundreds of MHz. The third variable filter F.sub.3 is configured in order to eliminate the disturbing signals between +/−2 MHz and +/−8 MHz, for example with a narrow channel filter, a centre frequency F.sub.c3 fixed at 3 MHz and a 30 dB attenuation in the 1 MHz channel band.

[0042] The filters of the group of filters are for example “SAW” filters, or “BAW” (bulk acoustic wave) filters, or any other technology allowing a narrow filtering function to be produced in a reduced bulk.

[0043] When the architecture operates in transmission, the configurations of the filters are chosen in a way similar to that described for the reception mode operation of the architecture.

[0044] The signal to be transmitted S.sub.e by the antenna 30, via its transmission channel 30a, is transmitted in parallel via two ADC converters (analog-digital converters) to two first filters 341, 342, with variable frequencies situated in parallel allowing, among other things, the replicas linked to the use of the ADC to be filtered. The signal is then amplified via two amplifiers 343, 344, one amplifier being connected to an output of a first filter. At the output of the amplifiers, the IQ signals are mixed M.sub.3, M.sub.4, with a signal S.sub.90 from a phase splitter and a phase locked loop 350, in an IQ modulator before being transmitted into one and the same amplifier 345. The recombined and amplified signal is transmitted to the group of filters 32 of which one of the filters is selected and activated by the manager 35. The signal filtered of the spurious signals from +/−8 MHz to plus or minus several hundreds of MHz is then transmitted to the transmission chain of the antenna, via the switches K.sub.1, K.sub.2, set for transmission, then amplified via a first amplifier 312, then filtered by a harmonic filter 313 before being transmitted by the transmission part 30a of the antenna 30.

[0045] FIG. 4 illustrates, in its top part, an example of a filtering plan for a UHF band receiver and, in its lower part, for a UHF band transmitter.

[0046] The signal received on the antenna after passing through the antenna filter is filtered at +/−8 MHz in a filter F.sub.j selected from the group of filters 32 in order to eliminate a first type of disturbing signals P.sub.1, then filtered in the variable filter whose centre frequency is set at 3 MHz to eliminate a second type of disturbing signals P.sub.2, closer to the centre frequency to be received, before being transmitted to the digital-analog converter DAC.

[0047] The architecture of the radiofrequency device according to the invention can be used in the field of communications for the UHF and VHF bands, band S, etc.

[0048] The transceiver (transmitter-receiver) part can be produced on one and the same component of small size.

[0049] The architecture according to the invention uses a bank of wide channel filters and an RF “transceiver”. The architecture no longer requires the use of PLL, of intermediate frequency stages, of “front end” filtering for the reciprocal mixings/recombinations at the mixer. That results in a very significant gain in terms of consumption/bulk. The architecture then becomes simpler and the implementation (and therefore the development cost) is then easier.