Abstract: The invention proposes a filtering device having a frequency response which is symmetrical, using asymmetrical filters coupled by transposition means. The advantageous characteristics of the asymmetrical filters are retained and the faults associated with the asymmetry are eliminated. The asymmetrical filters are, for example, quartz filters. The invention also proposes an external transmission and reception unit, using the filtering device with the application of the filtering method.

Abstract: The present invention concerns a system of receiving signals comprising a retransmission base to amplify signals captured at a point in a domestic environment and retransmit them at the same frequency to digital receivers of the said domestic environment. According to the invention, the retransmission base amplifies and retransmits up to N DVB-T channels the positions of which can be anywhere in the receive band and are chosen dynamically by the system users. Means are provided in the system to share the system's amplification resources between the system's various digital receivers.

Abstract: The antenna, particularly for portable televisions, comprises two ports coupled to a radiating element (11), the two ports being placed on the radiating element at 90° to each other and at 45° relative to a horizontal plane. The two ports are linked to a broadband switching and phase shifting circuit controlled in order to supply a polarization diversity signal as output.

Abstract: The invention relates to a transmitting device limiting the out-of-band interferences. The modulation is done with or without inversion of the spectrum (FIG. 4A or 4B). Next, frequency transposition is done in supradyne or infradyne fashion (FIG. 4C or 4D) such that the parasitic effects originating from the modulation are always situated in the frequency band allocated for transmission. The invention relates to the transmission method, on the one hand, and to the transmission device, on the other hand.

Abstract: The invention proposes a transmission system using a reference subcarrier to synchronize a local oscillator 104. The reference subcarrier can be placed at various locations of the band allotted to an operator. The external unit 1 of the reception device comprises frequency-wise selection means 107 which make it possible to select the synchronization subcarrier.