Bidirectional frequency mixer, radiofrequency emitter/receiver system comprising at least one such mixer

p0001The present invention relates to a bidirectional frequency mixer, and a transmitter / receiver radio frequency system comprising at least one such mixer. It is particularly applicable in the design of integrated microwave circuits, especially in the millimeter band.

p0002radio frequency communications systems generally comprise receiving and transmitting devices such as antennas, a processing unit and an interface for the exchange of signals between the transmitter / receiver devices and the processing unit.

p0003To one hand to make it usable by a processing unit a signal received by the transmitting / receiving device, and also can emit a signal generated by the processing unit, the functions of receiving and emission generally comprise amplification stages, filtering, mixing and modulation / demodulation. The mixers are, among others, used to transpose the high frequency signals to lower frequency bands to facilitate the treatment. In particular, the use of certain filters, computers or demodulators sometimes require working at lower frequencies, called intermediate frequencies.

p0004One of the problems with the communications systems is sending / receiving simultaneously, or at least the transmission / reception in half-duplex mode. In particular, a further difficulty arises with the use of mixers. It appears unwanted frequencies of signals generated upon mixing, either in phase or reception in transmission phase.

p0005To meet these problems, it is known to use a transmitter chain separated from the receiver chain signals, as shown in <figref idrefs="f0001">figure 1</figref>. Each of these two processing then comprises its own components and can operate without disturbing the concomitant chain significantly. Such a structure has particular disadvantage of increasing the cost and size of the circuit. In particular, at least two mixers 6. 7 are required, one for receiving phase which converts high frequency signals to an intermediate frequency and one for the transmission phase that converts the signals from the unit treatment to a higher frequency. In millimeter-band frequencies, these can especially be integrated on a microwave integrated circuit MMIC also known as the Anglo-Saxon term "Monolithic Microwave Integrated Circuit". However, the number and size of components to be integrated on this type of circuit is an important criterion to be considered in the design phase.

p0006The <figref idrefs="f0001">figure 1</figref> comprises a transmitter / receiver radio frequency system according to the prior art. The system 1 comprises an antenna 2, a switching device 3, a processing unit 4, a local oscillator 5 and two mixers 6 and 7.

p0007During reception, a signal S_RF RF frequency received by the antenna 2 is transmitted by the switching device 3 to a first input of the first mixer 6a 6. By combining the signal S_RF with a frequency signal F_OL provided on a second input 6b by the local oscillator 5, the first mixer 6 generates a signal S_FI 6c on an output to an intermediate frequency compatible with the operation of the processing unit 4.

p0008In transmission phase, the processing unit 4 provides a first input of the second mixer 7 7c a signal S_FI IF frequency. By combining the signal S_FI with a frequency signal F_OL supplied by the local oscillator 5 on a second input 7b, the second mixer 7 produces at an output 7a a signal S_RF RF frequency. The signal S_RF is then transmitted through switch 3 to the antenna 2 which can be issued.

p0009US Patent referenced <patcit id="pcit0001" dnum="US5590412A"><text>US5590412</text></patcit> and from an application filed for Sanyo Electric Co has a bidirectional mixer signals.

p0010An object of the invention is especially common to use a single mixer to transmit and receive chains performing a rejection of unwanted frequencies in phase reception and transmission phase. To this end, the invention relates to a bidirectional signal mixer adapted to operate in two modes:<ul><li>o a reception mode, combining a radio signal S_{RF + IM} including an RF frequency component and a frequency component image IM with a signal S_FOL frequency F_OL to produce a signal S_FI intermediate frequency FI, </li><li>o a transmit mode, combining a signal S_FI of intermediate frequency signal with an S_FOL frequency F_OL to produce a radio signal S_RF,</li></ul>the mixer comprising at least:<ul><li>o four mixing cells, each being designed to combine two signals to produce an output signal frequency-transposed with respect to the first of the two signals,</li><li>o a first phase shifting means adapted to distribute the signal S_FOL on each mixing cell,</li><li>o a second phase shift means adapted, on reception, to distribute the power of the signal S_{RF + IM} on each mixing cell,</li><li>o a third phase shift means adapted, on reception, in combining the signals from said mixing cells to produce a signal S_FI free from the frequency component IM, the combined signals including image IM frequency components of phase and frequency components FI phase,</li></ul>the third phase shifting means also being adapted, in transmission, to distribute the power of the signal S_FI each mixing cell, and the second phase shifting means also being adapted, in transmission, combining the signals from said cell mixture to produce a radio signal S_RF free from the frequency component F_OLThe combined signals including frequency components F_OL in phase opposition and RF-phase frequency components.

p0011According to one embodiment, the first phase shifting means comprises at least one coupler adapted to distribute the power of an input signal to two output signals, the first output signal S_FOL^{90 °} being phase shifted relative to the second output signal S_FOL^{0 °}.

p0012The first phase shifting means may include a power divider and two couplers, said divider distributing the power of signal S_FOL on an input of each coupler, each coupler distributing the power of its input signal into two output signals, the first output signal S_FOL^{90 °} being phase shifted relative to the second signal S_FOL^{0 °} Release.

p0013The second phase shifting means may include at least three couplers, a first input-output of the first coupler being connected to an input-output of the second coupler, and a second input-output of the first coupler being connected to an input-output of the third coupler , the second and third coupler being connected to the mixing cells in order:<ul><li>o to distribute, at the output of the second and third coupler, the power of signal S_{RF + IM} received by an input-output of the first coupler,</li><li>o and / or combining the signals received by the second and third coupler to generate a signal S_RF on an input-output of the first coupler.</li></ul>

p0014The third phase shifting means may include at least three couplers, a first input-output of the first coupler being connected to an input-output of the second coupler, and a second input-output of the first coupler being connected to an input-output of the third coupler , the second and third coupler being connected to the mixing cells in order<ul><li>o to distribute, at the output of the second and third coupler, the power of signal S_FI received by an input-output of the first coupler,</li><li>o and / or combine signals received by the second and third co upleur to produce a signal S_FI on an input-output of the first coupler.</li></ul>

p0015The invention also relates to a transmitter / receiver radio frequency system comprising at least one bidirectional mixer comprising the features described above.

p0016Other features and advantages will become apparent from reading the detailed description and illustrative non-limiting which follows in conjunction with the accompanying drawings which show:<ul><li>the <figref idrefs="f0001">figure 1</figref>A transmitter / receiver radio frequency system of the prior art, the figure has already been submitted,</li><li>the <figref idrefs="f0001">2</figref>, A transmitter / receiver radio frequency system comprising a bidirectional frequency mixer according to the invention,</li><li>the <figref idrefs="f0002">3</figref>, An embodiment of a mixer according to the invention with the arrow indication of the direction of propagation of signals corresponding to the reception phase,</li><li>the <figref idrefs="f0003">4</figref>, An embodiment of a mixer according to the invention with the arrow indication of the direction of propagation of signals corresponding to the transmission phase,</li><li>the <figref idrefs="f0004">5</figref> a mixer example of using the invention.</li></ul>

p0017The <figref idrefs="f0001">2</figref> comprises a transmitter / receiver system of a 9-bidirectional mixer according to the invention, for converting signals during reception and transmission phase.

p00188 system, the detailed operation is described below, operates as a half-duplex mode. The system 8 includes nine bidirectional mixer, a signal processing device 10, an antenna 11 and a local oscillator 12 providing a transposition frequency. The mixer 9 has a first input 9b, 9d a second input, an input-output 9a and 9c output. The system 8 operates for example as described below.

p0019For a period of time .DELTA.t1, the system 8 operates in receive mode, that is that the antenna captures 11 external signals. These signals are transmitted to the mixer 9, and then to the processing unit 10. When the .DELTA.t1 period is over, the antenna 11 switches to transmit mode for a period .DELTA.T2, for example. The mixer 9 does not necessarily imply switching device to switch from one mode to another. The presence or absence of signals on the input-output 9a enough, in the example, to define the mode of operation. The signals from the processing unit 10, are then transmitted to the mixer 9 and then to the antenna 11 which emits. When .DELTA.T2 period is over, the antenna 11 switches back to receive mode for a .DELTA.t1 duration and the cycle repeats.

p0020The mixer 9 is called bidirectional in the sense that it can operate a frequency translation in both directions, ie converting signals of a frequency A to frequency B, and the frequency B to the frequency A.

p0021Reception phase, the bidirectional mixer 9 receives the input-output signal 9a S_RF RF frequency from the antenna device 11, and 9b on the first input a signal S_fol Fol frequency produced by the local oscillator 12. The role of the mixer 9 is then to convert the signal S_RF to a signal S_FI issued by 9c output, reduced intermediate frequency equal to | RF-Fol |. For example, a mixer may be used in a transmitter / receiver radio frequency, which receives a carrier wave at an RF frequency of 40 GHz and has to transpose this signal to an IF intermediate frequency equal to 5 Ghz. In this case, the local oscillator outputs a RF-frequency signal FI equal to 35 Ghz or RF + IF frequency equal to 45 GHz. In the embodiment developed in this description, the Mad transposition frequency is chosen so less RF and RF-Fol = Fl.

p0022However, the input signal S_RF can be noisy. It may contain a parasite particular frequency component at the frequency equal to IM Mad-FI, that's what the art commonly called the image frequency. As the mixer 9 is a broadband frequency spectrum, noise S_IM the IM frequency can be transposed to the frequency | IM-Fol | equal to IFs and disrupt the signal from the output 9c by being added to the useful signal. A mixer 9 according to the invention performs a rejection of the image frequency IM and the signal from the 9c output is composed of two main frequency components FI and Fol. Fol unwanted frequency can be easily filtered because it is generally much higher than FI.

p0023In transmission phase, the mixer 9 receives at the second input a signal S 9d_FIT FI frequency and at the first input a signal S 9b_FOL Fol frequency which can be produced by the same local oscillator 12 as the reception phase. The role of the mixer 9 is then convert the signal S_FIT to an outgoing higher frequency RF signal on the input-output 9a. This is then the antenna 11 which transmits the signal.

p0024The mixer 9 uses a signal S_fol generally high power to perform a frequency transposition to the transmission. As will be described later, a mixer can transmit output, part of power to input frequencies. But we must avoid forward Fol component by O 9a because Fol being relatively close to RF, and even closer to RF that FI is small, then it would be difficult to eliminate this frequency Fol filtering. By a method described later in relation to the<figref idrefs="f0002">3</figref>The mixer 9 therefore makes a rejection of the frequency Fol and the signal from the input-output 9a is then composed of the single RF frequency component.

p0025According to another mode of operation, the system 8 comprises two antennas, a first for transmission and one for reception of signals. In this case, the connection 13 can be split, for example by means of a power divider, an input of the power divider being connected to the first antenna and another input being connected to the second antenna. This embodiment is not shown in the figures.

p0026filtering means or amplifiers, not shown here, can also be placed on the lines connecting the mixer 9 to the other elements 10, 11 and 12 of the system 8.

p0027The <figref idrefs="f0002">3</figref> shows an example of embodiment of the invention with the arrow directions representing the direction of propagation of signals corresponding to the reception phase.

p0028The bidirectional mixer 9 can be achieved by the use of passive elements such as a first coupler 14, a second coupler 15, a third coupler 16, a fourth coupler 17, a fifth coupler 18, a sixth coupler 25, a seventh coupler 26 and an eighth coupler 27 but also through the active elements as a first mixing cell 19, a second mixing cell 20, a third mixing cell 21 and a fourth mixing cell 22.

p0029The fifth coupler 18 comprises a first input-output 18a, a second input-output 18b, a third input-output 18c, and a fourth input-output 18d. The input signal from the first input-output 18a is divided into power on the input-output 18b and 18c. The third input-output 18c, the signal out of phase by 90 ° while it is transmitted in direct line and therefore no phase shift to the second O 18b. The fourth input-output 18d is simply related to a resistive load 23. The other couplers 14, 15, 16, 17, 25 and 26, with the exception of the eighth coupler 27 operate in a similar manner by performing a phase shift of 90 °. The eighth coupler 27 includes four input-output, a first input-output 27a, a second input-output 27b, a third input-output 9c and a fourth O 9d. When two signals are input respectively by the first input-output 27a and the second inlet-outlet 27b, their powers are combined for output on the third input-output 9c. When a signal is received by the fourth input-output 9c, it is divided into power in the first and second input-output 27a, 27b. Then the signal from the first input-output 27a is phase shifted by 180 ° while the signal from the second input-output 27b is not shifted.

p0030A first mixing cell 19 includes a first port 19a, a second port 19b and a third 19c access. Its primary function to combine two respective frequencies of the input signals A and B to produce an output signal comprising the frequency components A, B, A + B | AB |. These are the frequency components A and B + | AB | which are useful because they are those which enable to transpose an input frequency to another lower frequency, for example for the reception, or higher, for example for transmission. The unwanted components may for example, be filtered out. As part of the operation described here, the first port 19a remains one input while the other two access 19b and 19c operate in opposition and become alternately input or output of the cell 19 by the mixer 9 is in receive mode or transmit . Other mixing cells 20, 21, and 22 presented thereafter operate in a similar manner.

p0031Reception phase, the input signal S_RF passes into the fifth coupler 18 which generates a signal S_RF^{90 °} The same frequency shifted by 90 ° on its third input-output 18c, while the second input-output 18b produces a signal S_RF^{0 °} of the same frequency and same phase as S_RF. Furthermore, the input signal S_RF may contain noise around the image frequency IM = Fol-FI. S noise_IM this frequency is potentially troublesome because it is transposed by a mixing cell to the intermediate frequency IF, and parasitizing the useful signal. A noisy signal S_RF+ S_IM is transmitted through the first coupler 18 and the signals S_RF^{0 °}+ S_IM^{0 °} and S_RF^{90 °}+ S_IM^{90 °} out of this coupler 18b respectively by the second and third input-output 18c. Following the same principle, the signals S_RF^{0 °}+ S_IM^{0 °} and S_RF^{90 °}+ S_IM^{90 °} pass respectively in the third and fourth couplers 16 and 17 via the first input-output 16a and 17a to undergo a 90 ° phase shift. Thus, the second and third input-output 16c, 16b, 17b and 17c of the third and fourth couplers 16 and all 17produisent a signal at the RF frequency noisy, but each with their own phase shift. The signals S_RF^{90 °}+ S_IM^{90 °} from the third input-output 16c of the third coupler 16and the second inlet-outlet 17b of the fourth coupler 17 are phase-shifted by 90 °, the signal S_RF^{0 °}+ S_IM^{0 °} 16b from the second input-output of the third coupler 16 is not phase-shifted and the signal S_RF^{180 °}+ S_IM^{180 °} based on the third input-sortie17c the fourth coupler 17 is phase shifted by 180 °.

p0032Similarly, the signal S_FOL produced by the local oscillator 12 is transmitted to the first and second couplers 14 and 15 after passing through a power splitter 24 for distributing the signal to their first two input-output 14a and 15a. Following the same principle as for the third and fourth couplers 16 and 17, the output signals of the first and second couplers 14 and 15 are of the same frequency but differing in phase Fol. The signals S_FOL90 ° from the third input-output 14c and 15c of the first and second couplers 14 and 15 are offset by 90 ° while the signals S_FOL^{0 °} from the second input-output 14b and 15b of the first and second couplers 14 and 15 are out of phase.

p0033According to another embodiment, the signals S_FOL^{0 °} and S_FOL^{90 °} produced as output from first and second couplers 14 and 15 are produced using a single coupler receiving the signal S_FOL produced by the local oscillator 12. A power divider is then placed at each of the two outputs of said coupler for distributing the power of the two signals S_FOL^{0 °} and S_FOL^{90 °} into four substantially equal power signals. These four signals are then divided into output so as to successively introduce the same phase shifts as those produced by the previous embodiment involving two couplers.

p0034Incoming signals on the first and third connection (19a and 19c), (20a and 20c), (21a and 21c), (22a and 22c) of each mixing cell 19, 20, 21 and 22 produce the following combinations :<ul><li>S o_FOL^{90 °} with S_RF^{90 °}+ S_IM^{90 °} on the first mixing cell 19,</li><li>S o_FOL^{0 °} with S_RF^{0 °}+ S_IM^{0 °} on the second cell mixture 20,</li><li>S o_FOL^{0 °} with S_RF^{90 °}+ S_IM^{90 °} on the third mixing cell 21,</li><li>S o_FOL^{90 °} with S_RF^{180 °}+ S_IM^{180 °} on the fourth mixing cell 22.</li></ul>According to the operation of a mixing cell described above, the frequency components at the output of the cell mixture are Fol, RF, IM, RF + Fol IM + Fol, and IF = RF-Fol = Mad-IM. Fol components, RF, IM, and RF + Fol are undesirable but may subsequently be filtered readily because of the significant difference in value between these frequencies and IF. To make the idea more clear, these components, although potentially present in the frequency spectrum, will therefore be ignored in the following description. The IF frequency component is derived from both RF-Fol and Mad-IM, so the frequency spectrum output is parasitized by a signal generated by the transposition of the frequency IM. We must remove this parasite signal. A signal S_FI^{90 °} IF frequency from the second access 21b of the third mixing unit 21 is the product of the transposition of the signal S_RF^{90 °} and 90 ° phase shifted RF frequency by the signal S_FOL^{0 °} Fol frequency. The S noise_IM^{90 °} Image frequency IM is also transposed signal S_{FI / IM}^{-90 °} IF frequency. But this signal S_{FI / IM}^{-90 °} is in phase opposition with respect to the signal S_FI^{90 °} resulting from the RF component. Remember, IM = Fol-FI and therefore IM-Fol = -FI while RF-Fol = Fl. The output of the second port 21b of the third mixing cell 21, there is thus a frequency signal S FI_FI^{90 °}+ S_{FI / IM}^{-90 °}. Similarly, the fourth cell 22 processes the input signals S_FOL^{90 °} and S_RF^{180 °}+ S_IM^{180 °} mutually phase offset by 90 °, so the signal from the second access 22b of the fourth mixing cell 22 is the same as that obtained from 21b. For the first and second cells 19 and 20, the input signals S_FOL^{90 °} and SRF^{90 °}+ S_IM^{90 °} one hand, and S_FOL^{0 °} and S_RF^{0 °}+ S_IM^{0 °} on the other hand are not phase with each other. The outputs of the second ports 19b and 20b of the first and second mixing cells, thus involving non-phase signals S_FI^{0 °}+ S_{FI / IM}^{0 °}.

p0035The signals from the second 19b and 22b access the first and fourth mixing cells 19 and 22 are recombined in the sixth coupler 25 and the signals from the second 20b access and 21b of the second and third mixing cells 20 and 21 are recombined in the seventh coupler 26.

p0036Thus, the sixth coupler 25 receives the signal S_FI^{0 °}+ S_{FI / IM}^{0 °} from the second access 19b of the first mixing cell by its third input-output 25c and receives the signal S_FI^{90 °}+ S_{FI / IM}^{-90 °} 22b from the second access of the fourth mixing cell by its second input-output 25b. Similarly, the signal S_FI^{0 °}+ S_{FI / IM}0 ° from the second access 20b of the second mixing cell 20 enters the seventh coupler 26 by its third input-output 26c and the signal S_FI^{90 °}+ S_{FI / IM}^{-90 °} from the second access 21 b of the third mixing cell enters its second input-output 26b. The signals input through the third input-output 25c and 26c of the sixth and seventh couplers are phase shifted by 90 °. Thus, the following combinations are carried out:<ul><li>o for the sixth coupler 25, S_FI^{0 ° + 90 °}+ S_{FI / IM}^{0 ° + 90 °} (Third input-output 25c of phase) with S_FI^{90 °}+ S_{FI / IM}^{-90 °} (Second O not out of step 25b)</li><li>o for the seventh coupler 26, S_FI^{0 ° + 90 °}+ S_{FI / IM}^{0 ° + 90 °} (Third input-output 26c of phase) with S_FI^{90 °}+ S_{FI / IM}^{-90 °} (Second O not out of step 26b).</li></ul>The powers between the inputs being substantially evenly distributed, so the signal S_FI^{0 ° + 90 °}+ S_{FI / IM}^{0 ° + 90 °}+ S_FI^{90 °}+ IFC / IM^{-90 °}= S_FI^{90 °} coming out of the first input-output coupler 25a of the sixth with a double power output as the signal S_FI^{90 °} entered by the second input-output coupler 25b of the sixth, thanks to the combination of the two signals input from the second and third input-output 25b and 25c. The seventh coupler 26 applying the same operation as the sixth coupler 25 on identical input signals, it is also a signal S_FI^{90 °} which exits the first input-output 26a of the sixth coupler. The signals S_{FI / IM} have been eliminated through the recombination of substantially the same power signal S_{FI / IM}^{90 °} and S_{FI / IM}^{-90 °} in phase opposition. The mixer 9 therefore makes a rejection of the image frequency during the reception phase.

p0037Finally, the signals S_FI^{90 °} from the first input-output 25a and 26a of the sixth and seventh couplers are recombined in the eighth coupler 27. These two signals are received by the first and second input-output 27a and 27b of the eighth coupler 27 and combine to get out on the exit 9c mixer 9.

p0038In summary, the signal S_RF+ S_IM entering the input-output 9a of 9 mixer combined with the signal S_FOL entering the first input 9b of the mixer 9 produces the signal S_FI^{90 °} out on the output 9c of the mixer 9. Fol frequency components, RF and RF + Fol from mixtures of cells 19, 20, 21, 22, then transmitted 9c output can then be easily filtered because of the large gap between these frequencies Fl.

p0039The phase shifts are applied using three couplers groups. A first group consisting of the first and second coupler (14, 15) is a first means for phase shifting the signals from the local oscillator 12. A second group consisting of the third, fourth, and fifth coupler (16, 17, 18) is a second means for phase shifting the RF frequency signals. A third group consisting of the sixth, seventh and eighth couplers (25, 26, 27) is a third means for phase shifting the IF frequency signals.

p0040The <figref idrefs="f0003">4</figref> shows an example of embodiment of the invention with the arrow indication of the direction of propagation of signals corresponding to the transmission phase.

p0041During this phase, a signal S_FI addressed the mixer by its second input 9d. The eighth coupler 27 then distributes the signal S_FI on its first and second input-output 27a and 27b. The signal S_FI^{180 °} from the first input-output 27a of the eighth coupler 27 is phase shifted by 180 ° relative to the input signal S_FI, While the signal S_FI^{0 °} 27b from the second input-output of the eighth coupling 27 is not shifted. The signal S_FI^{180 °} then passes into the sixth coupler 25 via its first input-output 25a and the signal S_FI0 ° between the seventh coupler 26 by its first input-output 26a. After passing through these two couplers 25 and 26, the signals S_FI^{180 °} and S_FI^{0 °} are each further divided into two signals. The signals S_FI^{180 °} and S_FI^{0 °} from the second input-output 25b and 26b of the sixth and seventh coupler 25 and 26 are out of phase while the S signals_FI^{-90 °} and S_FI^{90 °} respectively from the third input-output 25c and 26c of the sixth and seventh coupler are phase shifted by 90 °. As described above for the reception phase, the sixth and seventh couplings 25 and 26 are associated with mixing cells 19, 20, 21, 22. The original signal S_FI 9d arriving on the second input of the mixer 9 is thus distributed on the second ports 19b, 22b, 21b, 20b of the mixing cells 19, 22, 21, 20 with a phase difference of 90 ° between each successive track:<ul><li>o on the second port 19b of the first mixing cell 19, a signal S_FI^{-90 °} phase-shifted IF frequency of -90 °,</li><li>o access the second 22b of the fourth mixing cell 22, a signal S_FI^{180 °} phase-shifted IF frequency of 180 °,</li><li>o on the second port 21b of the third mixing cell 21, a signal S_FI^{0 °} non-phase-shifted IF frequency,</li><li>o on the second access 20b of the second cell mixture 20, a signal S_FI^{90 °} FI 90 ° phase shifted frequency.</li></ul>

p0042In parallel, the local oscillator outputs, as the reception phase, a signal S_FOL Fol frequency which is transmitted and phase shifted by the first and second couplers 14 and 15. Each mixing cell receives two frequency signals IF and Fol, but each with a different combination of phases. Indeed,<ul><li>o the first cell mixture combines 19 S_FI^{-90 °} 19b on the second access with S_FOL^{90 °} the first port 19a,</li><li>o the second cell mixture combines 20 S_FI^{90 °} 20b on the second access with S_FOL^{0 °} the first port 20a,</li><li>o the third cell mixture combines 21 S_FI^{0 °} on the second port 21b with S_FOL^{0 °} the first port 21a,</li><li>o the fourth cell mixture combines 22 S_FI^{180 °} 22b on the second access with S_FOL^{90 °} the first port 22a.</li></ul> According to the operation of a mixing cell described above, the frequency components at the output of the cell mixture are FI Fol, IM = Fol-LAN, and RF = FI + Fol. FI components Fol and IM are undesirable. The FI component can later be easily filtered because of the large gap between IF and RF, it will be ignored in the following description. For cons, the Fol and IM components are potentially quite close to RF for especially hinder a bandpass filtering around RF. We must remove them. Thus, the output of the cell mixture, one obtains:<ul><li>o 19c on the third access of the first mixing cell 19, S_{FI + Fol}^{-90 ° + 90 °}+ S_Mad-FI^{90 ° - (- 90) °}+ S_fol^{90 °} = S_RF^{0 °}+ S_IM^{180 °}+ S_fol^{90 °},</li><li>o 20c on the third access of the second cell mixture 20, S_{FI + Fol}^{90 ° + 0 °}+ S_Mad-FI^{0 ° -90 °}+ S_fol^{0 °} = S_RF^{90 °}SM +^{-90 °}+ S_fol^{0 °},</li><li>o the third port 21 c of the third mixing cell 21, S_{FI + Fol}^{0 ° 0 ° +}+ S_Mad-FI^{0 ° -0 °}+ S_folS = 0 °_RF^{0 °}+ S_IM^{0 °}+ S_fol^{0 °}</li><li>o 22c on the third access of the fourth mixing cell 22, S_{FI + Fol}^{180 ° + 90 °}+ S_Mad-FI^{90 ° -180 °}+ S_fol^{90 °}= S_RF-^{90 °}+ S_IM^{-90 °}+ S_fol^{90 °}</li></ul>

p0043Following the same principle that the reception phase, the signals are recombined in the third, fourth and fifth couplers 16, 17 and 18. The signal S_RF^{0 °}+ S_IM^{180 °}+ S_fol^{90 °} leaving the third access 19c of the first mixing cell 19, is transmitted to the third coupler 16 via its third input-sortie16c and is phase shifted by 90 °. The signal S_RF^{90 °}+ S_IM^{-90 °}+ S_fol^{0 °} leaving the third access 20c of the second mixing cell 20 is not shifted. The third coupler 16 thus operates the following combination: (S_RF^{0 ° + 90 °}+ S_IM^{180 ° + 90 °}+ S_fol^{90 ° + 90 °}) + (S_RF^{90 °}+ S_IM^{-90 °}+ S_fol^{0 °}) And the signal from the first input-output 16a of the third coupler 16 is S_RF^{90 °}+ S_IM^{-90 °}With a power substantially equal to the sum of the input powers. Fol the component was removed by the combination of anti-phase signal approximately equal powers S_fol^{180 °} and S_fol^{0 °}. The same principle operates in the fourth coupler 17 with the following combination: (S_RF^{0 °}+ S_IM^{0 °}+ S_fol^{0 °}) + (S_RF^{-90 + 90}+ S °_IM^{-90 ° + 90 °}+ S_fol^{90 ° + 90 °}). The signal from the first input-output 17a of the third coupler 17 is S_RF^{0 °}+ S_IM^{0 °}With a power substantially equal to the sum of the input powers. Again, the combination of the input signals results in a rejection of the frequency Fol output.

p0044The two signals from the first input-output 16a and 17a of the third and fourth couplers 16 and 17 are then recombined in the fifth coupler 18 via the second and third input-output 18b and 18c respectively. The following combination is used: (S_RF^{90 °}+ S_IM^{-90 °}) + (S_RF^{0 ° + 90 °}+ S_IM^{0 ° + 90 °}). The powers of the second and third input-output 18b and 18c of the fifth coupler 18 being substantially equivalent, the fifth coupler 18 operates a rejection of the image frequency by combining the two components S_IM^{-90 °} and S_im^{90 °} in phase opposition. The signal from its first input is S-sortie18a_RF^{90 °}_.

p0045In summary, the signal S_IF entering the second input 9d 9 mixer combined with the signal S_FOL entering the first input 9b of the mixer 9 produces the signal S_RF^{90 °}out on the input-output 9a of the mixer 9. The frequency components Fol and IM from mixtures of cells are eliminated by judicious combinations of phase signals. IF frequency after mixing cells and transmitted O 9a can then be easily filtered because of the large gap between RF and IF.

p0046According to another embodiment, the local oscillator 12 may issue a frequency Fol equal to RF + IF. In this case, the transposition frequencies operated by the mixer allows, again, to obtain a frequency signal IF output, but the frame rate to eliminate equals Fol + FI rather than to Mad-FI. The architecture of the mixer remains valid in this variant. Indeed, simply adjust the frequency Fol couplers and swap the connections to the first and fourth input-output 18a and 18d of the fifth coupler to pass the RF signal by the fourth O 18d. Preferably, a frequency equal to RF Fol-FI is chosen because it is generally easier to manage smaller frequencies.

p0047An advantage of the invention is to directly operate the image rejection directly into the mixer. This avoids adding a filter, always penalizing in size of a circuit and sometimes impossible to integrate on a MMIC.

p0048Another advantage of the invention is to give the blender more power linearity. Indeed, each mixing cell is subject to the phenomenon of saturation of the output power when the input power becomes too much and loses its linear characteristic. Each mixing cell is particularly characterized by its output power at 1dB compression point. To recap, the 1dB compression point is on a curve showing the output power depending on input power, the point at which the difference between the output power and linear extrapolation of 1dB. A mixer having four mixing cells 19, 20, 21 and 22 of same compression point at 1 dB in parallel, has a compression point at 1 dB higher than that of each of the cells in isolation, through the recombination of the powers in the output couplers 25, 26 and 27 in reception and in the couplers 16,17 and 18 in transmission.

p0049The <figref idrefs="f0004">5</figref> schematically shows an example of a circuit incorporating a single mixer for a communication application in millimeter range.

p0050The circuit 50 includes a mixer 9 bidirectional frequencies, a frequency multiplier 51, a low noise amplifier 52, a first amplifier 53 controlled by voltage, a coupling component 54, and a second amplifier 55 controlled by voltage.

p0051The circuit 50 is composed of two main parts. The first part 50a gathering the mixer 9, the low noise amplifier 52, the first amplifier 53 controlled by voltage, and the frequency multiplier 51. The second portion 50b comprises the coupling component 54 and the second amplifier 55 controlled by voltage.

p0052The first section 50a has elements that operate at frequencies in the millimeter band, which allows integrating this part of the circuit in an MMIC. The mixer 9 is connected to the multiplier 51 receiving frequencies of a signal produced by a local oscillator, connected to the low noise amplifier 52 receiving an antenna signal, connected to the first 53 voltage-controlled amplifier for amplifying signals to be transmitted and connected to the coupling component 54. Furthermore, the coupling component 54 receives signals at the intermediate frequency through the second amplifier 55 controlled by voltage, and it also transmits signals to the IF frequency.

p0053The coupling component 54 comprises the sixth, seventh, and eighth couplers 25, 26, 27 operating at the intermediate frequency IF. In the example described, the IF frequency is 5 GHz. This frequency is too low to be able to place the second largest part 50b integrated circuit, so the elements of the second portion 50b are for example made from discrete components or lines spread over PCB.