Patent ID: 12199652

DETAILED DESCRIPTION

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.

FIG.3illustrates 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 antenna30linked to a first transmission channel or reception channel selection device K1, followed by a front-end stage31whose output is linked to a second transmission channel or reception channel selection device K2, which is itself linked to a set or group of several filters32, connected to a transmission channel or reception channel selection device K3. The third selection device K3is 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.

The antenna30comprises a transmission channel30band a reception channel30a. 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.

Considering the reception channel, a signal Sr is received on the antenna30. The signal is first of all filtered by an antenna filter310to a first frequency F1, the filtered signal S1is then amplified by an amplifier311, before transmission to the group of filters32. The group of filters comprises N filters3201. . .320N. 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 manager35which 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 F2, 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 S2is transmitted to the transceiver33. The filtered signal S2is amplified in a first amplifier331. After this amplifier, the signal S2passes through an IQ demodulator. It is then mixed, M1, M2, with a signal S90from a phase splitter and a phase locked loop350, before being transmitted to a second amplifier332,334, then filtered by a third variable frequency filter333,335, whose centre frequency F3will 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 S3is then transmitted to a digital-analog converter, DAC.

The antenna filter310is chosen to operate in a frequency band [FMin, FMax] determined by the application.

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.

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.

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).

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

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 F2selected in the group of filters is configured with a centre frequency Fc2adapted 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 F3is configured in order to eliminate the disturbing signals between +/−2 MHz and +/−8 MHz, for example with a narrow channel filter, a centre frequency Fc3fixed at 3 MHz and a 30 dB attenuation in the 1 MHz channel band.

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.

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.

The signal to be transmitted Seby the antenna30, via its transmission channel30a, is transmitted in parallel via two ADC converters (analog-digital converters) to two first filters341,342, 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 amplifiers343,344, one amplifier being connected to an output of a first filter. At the output of the amplifiers, the IQ signals are mixed M3, M4, with a signal S90from a phase splitter and a phase locked loop350, in an IQ modulator before being transmitted into one and the same amplifier345. The recombined and amplified signal is transmitted to the group of filters32of which one of the filters is selected and activated by the manager35. 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 K1, K2, set for transmission, then amplified via a first amplifier312, then filtered by a harmonic filter313before being transmitted by the transmission part30aof the antenna30.

FIG.4illustrates, 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.

The signal received on the antenna after passing through the antenna filter is filtered at +/−8 MHz in a filter Fjselected from the group of filters32in order to eliminate a first type of disturbing signals P1, then filtered in the variable filter whose centre frequency is set at 3 MHz to eliminate a second type of disturbing signals P2, closer to the centre frequency to be received, before being transmitted to the digital-analog converter DAC.

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.

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

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.