WO2003061112A1

WO2003061112A1 - Transmission mode mixing device comprising rejection of intermediate, low lateral and local oscillator frequencies,

Info

Publication number: WO2003061112A1
Application number: PCT/FR2002/004243
Authority: WO
Inventors: Christian Rumelhard; Mahmoud Mehdi
Original assignee: Conservatoire National Des Arts Et Metiers
Priority date: 2001-12-28
Filing date: 2002-12-10
Publication date: 2003-07-24
Also published as: FR2834413B1; EP1472784A1; FR2834413A1; AU2002364823A1

Abstract

The invention concerns a mixer device mixing an intermediate frequency signal (IF) with a carrier signal from a local oscillator (LO) so as to produce an output signal comprising mainly a radio-frequency high lateral band component (RF), the low lateral band component and the frequency components (IF and OL) being eliminated. Therefor, the inventive device comprises two phase-shifting lines fed by the intermediate frequency signal and the carrier signal. Each phase-shifting line generates four carrier signals or four intermediate frequency signals successively phase-shifted by an angle of -90°. Said phase-shifted signals feed in pairs four mixers. The output signals of the four mixers pass through successive couplers and a 180° phase-shifter so as to eliminate the LO, IF and LB components and only delivers in output a RF frequency component. The 180° phase-shifting may take place in the phase-shifting lines.

Description

"Emission mixing device comprising rejection of the intermediate, low side and local oscillator frequencies."

The present invention relates to a device for mixing in transmission comprising a rejection of the intermediate, low lateral and local oscillator frequencies. It also relates to a method associated with this device. It finds a particularly interesting application in the field of telecommunications networks in which to transmit information in the form of an RF radio frequency signal in the high sideband, a frequency data signal called intermediate frequency IF is mixed with a microwave signal. OL frequency serving as a carrier for the data signal. Generally, the microwave carrier signal comes from a local oscillator. These telecommunications networks can be local loops in microwave or intra-building links in millimeter wave. For example, the frequencies of use are between 1 and 100 GHz.

The result of such a mixture is an output signal comprising different intermodulation products. More precisely, this output signal comprises four components respectively at frequencies RF (RF = OL + FI), OL, FI and

LB (LB = OL - FI). The component that we want to isolate for transmission is the high frequency RF sideband.

It is therefore essential to eliminate the other components.

It is difficult to remove the frequency component OL because it generally has a power greater than that of the high sideband, in addition the frequencies RF and OL are very close and relatively high.

Circuits are also known in which, to remove the components at the frequency OL, FI and LB, use a series of couplers and phase shifters acting on the microwave signal and the front data signal perform mixing operations. However, such an arrangement involves a large number of passive components.

The present invention aims to improve the current devices by proposing a new device allowing the direct elimination of the three components at the frequency OL, FI and LB.

Another object of the invention is to propose a device limiting the integration of passive components so as to limit the cost price of such a device. Another object of the invention is to improve the conversion gain of such a mixing device by reducing the losses suffered by the frequency components OL and FI.

The above objectives are achieved with a mixing device for mixing a data signal at an intermediate frequency IF with a carrier signal so as to generate an output signal comprising an RF radio frequency component in the high sideband. The device according to the invention is such that this output signal is devoid of components at the frequency of the carrier signal, at the intermediate frequency and at the frequency of the signal in the low sideband. According to the invention, the device comprises:

- first phase shifting means for generating from the data signal a series of at least four data signals successively phase shifted by an angle of 90 degrees;

- second phase shift means for generating from the carrier signal a series of at least four carrier signals successively phase shifted by an angle of 90 degrees;

- mixing means for mixing each phase shifted data signal with a corresponding phase shifted carrier signal;

- combining means for combining the signals from the mixing means so as to generate the radio frequency signal; - third phase-shifting means for introducing a 180-degree phase shift in one of the aforementioned elements of so as to keep only the radio frequency signal at the output of the combining means.

The first and second phase shifting means can be phase shift lines comprising capacitors and inductors. Preferably the combining means are couplers, and the mixing means consist of four mixers with two inputs each.

Unlike current techniques, the device according to the invention involves two phase shift lines each acting on an input signal, the couplers only intervene after the mixing operations.

More precisely, on the frequency carrier signal OL originating for example from a local oscillator, a first phase shift of 90 ° is introduced, this phase shifted signal is then introduced into a first mixer; then a phase shift of 90 ° is again introduced on the first phase-shifted signal, this second signal phase shifted by a total of 180 ° with respect to the frequency carrier signal OL is introduced into a second mixer; so on until the fourth mixer. And the same is done with the intermediate frequency data signal FI which successively supplies the same mixers. The first phase shifted signal serves as a reference for the balance of phase shifts as will be seen below, that is to say that the first signal is considered to have a zero phase shift.

According to a first variant of the invention, the third phase shift means are integrated into one of the first or second phase shift means so as to constitute a phase shift line generating four data signals successively phase shifted by an angle of -90 degrees . In practice, this amounts to having a first delay line with successive phase shifts of + 90 ° and a second advance line with successive phase shifts of -90 °.

This variant makes it possible to obtain at the inputs of the second, third and fourth mixers, two signals (a phase-shifted OL signal and a phase-shifted IF signal) in phase opposition. In this which concerns the first mixer, their zero phase shift is considered since they are taken as references. Advantageously, the combining means can consist of a single coupler provided with four inputs to receive the signals from the four mixers.

According to another variant of the invention, the third phase-shifting means are integrated at the output of the first and third mixers, or else at the output of the second and fourth mixers, the mixing means comprising at least four mixers corresponding to the four signals of output of the first and second phase shift means. In this variant, while the first and second phase shifting means introduce successive 90 ° phase shifts, the 180 ° phase shift is introduced here in the output signals of two mixers. Those skilled in the art will readily understand that this 180 ° phase shift can come from a mixer intrinsically carrying out a 180 ° phase shift, from an independent phase shifter placed at the outlet of a mixer not carrying out phase shift, or even from a coupler whose input intended to receive the signal to be subjected to the phase shift immediately introduces a phase shift of 180 °.

According to yet another advantageous variant of the invention, it is possible to place oneself in the conditions where the mixing means comprise at least four mixers corresponding to the four output signals of the first and second phase shifting means, and the combination means eompr-enant -r

a first combining means (Cl) for combining the signals leaving the first and third mixing means,

- a second combining means (C2) for combining the signals leaving the second and fourth mixing means; and

a third combining means (C3) for combining the signals from the first two combining means, in this case, the third phase-shifting means can be integrated at the output of the first or second combination means.

In the last two variants, the two input signals from the same mixer have the same degree of phase shift relative to the reference signals: the first phase-shifted OL signal and the first phase-shifted IF signal. Four signals are therefore obtained from the four mixers. Each of these four signals includes: - a frequency component IF phase shifted according to the input signals, i.e. 0 ° for the first mixer, 90 ° for the second mixer, 180 ° for the third mixer and 270 ° for the fourth mixer; - a phase component OL phase shifted in accordance with the input signals; a high frequency RF sideband component phase shifted by an angle resulting from the sum of the frequencies OL and FI; and a low sideband component of frequency LB phase shifted by an angle resulting from the difference of the frequencies OL and FI;

In the last variant, the combining means can comprise three couplers. Two couplers for coupling each two signals leaving two mixers, these two mixers being such that their input signals have, from one mixing means to another, a phase shift of an angle of 180 °. A third coupler for coupling the output signals of the first two couplers after one of the two signals has undergone a phase shift of an angle of 180 ° by the third phase shift means.

In other words, the signal leaving the first mixer is coupled with the signal leaving the third mixer, these signals being phase shifted relative to each other by an angle equal to 180 °. The result of this coupling is a first coupled signal. In the same way, the signals leaving the second and fourth mixers are coupled. The result of this coupling is a second coupled signal into which, for example, a phase shift of an angle of 180 ° is introduced. At the output of the two couplings, there is a first coupled signal and a second coupled and phase-shifted signal. It is then that a third coupler couples these two signals so as to obtain a high frequency sideband signal of RF frequency. Successive mixes and couplings have helped to remove the frequency components OL, FI and LB.

According to an advantageous characteristic of the invention, the mixing means are mixers comprising two transistors mounted in cascode.

In general, the device according to the invention can comprise bipolar heterojunction transistors and / or field effect transistors.

Furthermore, each transistor used can be biased by means of a current on the base and of a voltage on the collector-emitter junction. Other advantages and characteristics of the invention will appear on examining the detailed description of a mode of implementation in no way limiting, and the appended drawings in which: FIG. 1 is a simplified electronic diagram of the device according to a variant of the invention; FIG. 2 is a graph illustrating the power spectrum of the microwave frequency signal OL at the input OL of the device according to the invention; FIG. 3 is a graph illustrating the power spectrum of the high frequency sideband RF at the output of the device according to the invention; Figure 4 is a simplified electronic diagram of the device according to another variant of the invention; and FIG. 5 is a simplified electronic diagram of the device according to yet another variant of

1 invention. Referring to FIG. 1, a mixer device according to the invention will now be described in which it is desired to mix a microwave signal of frequency OL coming from a local oscillator not shown with a data signal of intermediate frequency FI. The frequency data signal FI is intended to modulate the microwave signal frequency OL in order to obtain an output signal at the frequency RF. An object of the present invention is to obtain an output signal only at the RF frequency for this it is necessary to suppress or at least minimize the other components present in the output signal and frequencies IF, OL, and LB. The RF frequency component (FI + OL) is called the high sideband. The LB frequency component (OL-FI) is called the low sideband. The present invention is remarkable by the fact that the mixing device according to the invention allows the elimination of the OL, FI and LB components by applying microwave and data signals to transistors through phase shift lines rather than through a series of couplers as in the prior art. This characteristic makes it possible to reduce the number of passive components required and to increase the conversion gain.

In Figure 1, we see a series of mixers ML1, ML2, ML3 and ML4 supplied by two phase shift lines LDI and LD2 and generating signals to a set of couplers C1, C2 and C3. Each phase shift line LDI or LD2 comprises conventional phase shift cells made up of inductance Li and capacitance Ci. These phase shift lines are adapted to an impedance of 50Ω. They each include a termination impedance Z ₀ with a value of 50Ω.

The microwave frequency signal OL is injected into the first phase shift line LDI, then distributed over this line with phase shifts of -90 °. Four microwave signals OL1, OL2, OL3 and OL4 are then successively phase-shifted by - 90 °. Taking as reference, the first phase shifted microwave signal OL1, we can then write: OL2 = OLl (-90 °), 0L3 = OL2 (-90 °), and 0L4 = 0L3 (-90 °).

Similarly, the intermediate frequency data signal FI is injected at the input of the second phase shift line LD2, then distributed on this line with phase shifts of -90 °. The data signals FIi, FI ₂ , FI ₃ and FI _{4 are} thus obtained.

By taking as phase shift reference the frequency signals OLi and FIχ, the mixer MLl is supplied by these frequency signals OLl and FIi with phase shift 0 °, the mixer ML2 by the frequency signals OL ₂ is FI ₂ characterized by a phase shift of - 90 ° to the reference; the mixer ML3 is supplied by the frequency signals OL ₃ and FI ₃ characterized by a phase shift of - 180 ° relative to the reference; and the mixer ML4 is supplied by the frequency signals 0L ₄ and FI characterized by a phase shift of -270 ° relative to the reference.

At the output of each mixer, a signal is therefore obtained comprising four components at frequencies OL, FI, RF, LB, each frequency being characterized by a particular phase shift:

- at point A: OL (0 °), FI (0 °), RF (0 °) = OL + FI, and LB (0 °) = OL-FI;

- at point B: OL (-90 °), FI (-90 °), RF (-180 °), and LB (0 °);

- at point C: OL (-180 °), FI (-180 °), RF (0 °), and LB (0 °);

- at point D: OL (-270 °), FI (-270 °), RF (-180 °), and LB (0 °) Cleverly, by combining in the coupler Cl the signals of outputs A and C we obtain a signal at output E characterized in that the signals of frequencies OL and FI are eliminated while the signals of frequencies RF and LB are added. An RF frequency signal (0 °) and an LB frequency signal (0 °) are therefore obtained.

In the same way by combining the output signals B and D in the coupler C2, one obtains at the output of this coupler C2 a signal characterized by the fact that the frequency signals OL and FI are eliminated while the frequency signals RF and LB are added. We therefore obtain an RF frequency signal (-180 °) and an LB frequency signal (0 °). Having thus eliminated the signals of frequencies OL and FI it remains to eliminate the signal of frequency LB. To do this, a phase shift of 180 ° is introduced into the output signal of the coupler C2 so as to obtain at point F a signal comprising a component at the frequency RF (0 °) and a component at the frequency LB (180 °).

Finally, the combination in the coupler C3 of the signals at point E and F ensures the rejection of the component at the frequency LB and the sum of the components at the frequency RF. This gives a mixing spectrum free of the frequencies OL, LB and FI.

A simulation of the device according to the invention with the HP / MDS and HP / ADS software clearly shows the difference between the input spectrum represented in FIG. 2 and the output spectrum represented in FIG. 3. In FIG. sees the power spectrum of the microwave frequency signal OL at the input of the first phase shift line LDI. The power value of this signal is -10dBm. By analyzing the spectrum at the output of the mixer (see figure 3), the power of the RF frequency signal is -33dBm. The signal strengths of frequencies OL (-43dBm), LB (-46dBm) and FI (-160dBm) are strongly attenuated at the output despite the number of transistors employed in the device thus described, these transistors normally bringing a significant gain to these powers. This therefore highlights the rejection of the frequencies OL, LB and FI. As a result, the strength of the RF frequency signal is enhanced compared to other frequencies.

The device according to the invention is therefore capable of producing a rejection of the high and very close frequencies. In Figure 4, we find the same elements as in Figure 1, except that the phase shifter LD3 is deleted and replaced by two identical 180 ° phase shifters LD4 and LD5 arranged respectively on the branches B and D.

We can also consider using branches A, C and E rather than branches B, D and F respectively to arrange the phase shifters LD4, LD5 and LD3. Figure 5 illustrates a diagram in which most of the elements of Figures 1 and 4 are present. In order to avoid the use of one or more phase shifters as in FIGS. 1 and 4, opposite phase shifts are carried out on the lines LDI and LD2, that is to say that a series of phase shifts of -90 ° is carried out. for the injected OL signal and + 90 ° this time for the injected FI signal. We therefore introduced a new phase shift line LD6 in place of LD2. Hence the new phase assessment:

OLi = OL Z 0 ° FIi = FI Z 0 °

OL ₂ = OL Z -90 ° FI ₂ = FI z + 90 °

OL ₃ = OL Z-180 ° FI ₃ = FI z +180 ^<

OL ₄ = OL Z -270 ° FI ₄ = FI z +270 ^c

B D 25

FI Z + 90 ° FI Z + 270 °

OL Z -90 ° OL Z -270 °

RF Z 0 ° RF Z 0 °

IM Z -180 ° IM Z -180 ° 30

LD3, LD4 and LD5 phase shifters are therefore not used. The three couplers C1, C2 and C3 can also be replaced by a single coupler with four inputs.

Of course, the invention is not limited to the examples which have just been described and numerous modifications can be made to these examples without departing from the scope of

1 invention.

Claims

1. Mixing device for mixing a data signal at an intermediate frequency with a carrier signal so as to generate a radio-frequency signal, characterized in that it comprises:

- first phase shift means (LD2) for generating from the data signal (FI) a series of at least four data signals (FIι- ₄ ) successively phase shifted by an angle of 90 degrees;

- second phase shift means (LDI) for generating from the carrier signal (OL) a series of at least four carrier signals (0Lι_) successively phase shifted by an angle of 90 degrees; - mixing means (Ml _i- ) for mixing each phase-shifted data signal with a corresponding phase-shifted carrier signal;

- combining means (Cι- ₃ ) for combining the signals from the mixing means so as to generate the radio frequency (RF) signal;

- third phase-shifting means (LD ₃ - ₅ ) to introduce a 180-degree phase shift in one of the aforementioned elements so as to keep only the radio-frequency signal at the output of the combining means.

2. Device according to claim 1, characterized in that the third phase-shifting means (LD ₃ -s) are integrated in the first phase-shifting means (LD2) so as to constitute a phase shift line generating four successively phase-shifted data signals d '' an angle of -90 degrees.

3. Device according to claim 1, characterized in that the third phase-shifting means (LD ₃ _ ₅ ) are integrated in the second phase-shifting means (LDI) so as to constitute a phase shift line generating four successively phase-shifted data signals d '' an angle of -90 degrees.

4. Device according to claim 1, characterized in that the mixing means comprising at least four mixers corresponding to the four output signals of the first and second phase shifting means, the third phase shifting means are integrated at the output of the first and third mixers (MLl, ML3).

5. Device according to claim 1, characterized in that the mixing means comprising at least four mixers corresponding to the four output signals of the first and second phase shifting means, the third phase shifting means are integrated at the output of the second and fourth mixers (ML2, ML4).

6. Device according to claim 1, characterized in that the mixing means comprising at least four mixers corresponding to the four output signals of the first and second phase shifting means, and the combining means comprising:

- a third combining means (C3) for combining the signals coming from the first two combining means, the third phase-shifting means are integrated at the output of the first combining means.

7. Device according to claim 1, characterized in that the mixing means comprising at least four mixers corresponding to the four output signals of the first and second phase shifting means, and the combining means comprising: a first combining means (Cl) for combining the signals leaving the first and third mixing means,

- a third combination means (C3) for combining the signals from the first two combination means, the third phase shift means are integrated at the output of the second combination means.

8. Device according to claims 1 to 3, characterized in that the combination means (Cι_ ₃ ) consist of a multi-input coupler.

9. Device according to any one of the preceding claims, characterized in that the first and second phase-shifting means consist of phase-shift lines comprising capacitors and inductors.

10. Device according to any one of the preceding claims, characterized in that the mixing means are mixers comprising two transistors mounted in cascode.

11. Device according to any one of the preceding claims, characterized in that it comprises bipolar heterojunction transistors.

12. Device according to any one of the preceding claims, characterized in that it comprises field effect transistors.

13. Device according to any one of the preceding claims, characterized in that each transistor used is biased by means of a current on the base and of a voltage on the collector-emitter junction.