FR2669787A1 - Symmetric UHF mixer - Google Patents

Symmetric UHF mixer Download PDF

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Publication number
FR2669787A1
FR2669787A1 FR9014626A FR9014626A FR2669787A1 FR 2669787 A1 FR2669787 A1 FR 2669787A1 FR 9014626 A FR9014626 A FR 9014626A FR 9014626 A FR9014626 A FR 9014626A FR 2669787 A1 FR2669787 A1 FR 2669787A1
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signal
symmetrical
coupler
characterized
phase
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French (fr)
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Sauvage Marc
Le Polozec Xavier
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Alcatel Telspace
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Alcatel Telspace
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    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03DDEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D9/00Demodulation or transference of modulation of modulated electromagnetic waves
    • H03D9/06Transference of modulation using distributed inductance and capacitance
    • H03D9/0658Transference of modulation using distributed inductance and capacitance by means of semiconductor devices having more than two electrodes
    • H03D9/0675Transference of modulation using distributed inductance and capacitance by means of semiconductor devices having more than two electrodes using field effect transistors
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03DDEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/14Balanced arrangements
    • H03D7/1408Balanced arrangements with diodes
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03DDEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/14Balanced arrangements
    • H03D7/1425Balanced arrangements with transistors
    • H03D7/1441Balanced arrangements with transistors using field-effect transistors
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03DDEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D2200/00Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
    • H03D2200/0001Circuit elements of demodulators
    • H03D2200/0005Wilkinson power dividers or combiners
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03DDEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D2200/00Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
    • H03D2200/0001Circuit elements of demodulators
    • H03D2200/0025Gain control circuits
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03DDEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D2200/00Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
    • H03D2200/0001Circuit elements of demodulators
    • H03D2200/0025Gain control circuits
    • H03D2200/0027Gain control circuits including arrangements for assuring the same gain in two paths
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03DDEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D2200/00Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
    • H03D2200/0041Functional aspects of demodulators
    • H03D2200/009Reduction of local oscillator or RF leakage
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03DDEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/12Transference of modulation from one carrier to another, e.g. frequency-changing by means of semiconductor devices having more than two electrodes
    • H03D7/125Transference of modulation from one carrier to another, e.g. frequency-changing by means of semiconductor devices having more than two electrodes with field effect transistors

Abstract

The present invention relates to a symmetric UHF mixer. This mixer comprises an input coupler (S1) receiving an input signal (FI) and addressing it to two non-linear stages (T1, T2), a UHF coupler (S2) receiving a local signal (OL) and addressing it also to these stages, an output coupler (S3) for combining the two mixed signals (M1, M2) output by the two non-linear stages (T1, T2), and also comprises a symmetric phase-shifting cell (P) so that the components at the frequency of the local signal of the two mixing signals recombine in phase opposition on the output access of the output coupler (S3). One use of this mixer, allowing strong rejection of the image signal consists in producing a device comprising a distribution coupler (SR) which distributes the input signal (FI) into two components phase-shifted by 90 DEG between two mixers (MHS1, MHS2) as above, the output signals from these mixers being summed after phase shifting by 90 DEG of one of the two of them on the output access of a combining coupler (SC). <IMAGE>

Description

Symmetrical microwave mixer
The present invention relates to a symmetrical microwave mixer.

 Symmetrical microwave mixers are used in particular in radio transmissions to modulate a local signal which is a carrier wave by a modulating signal and, conversely, to recover a modulating signal from a modulated carrier wave. They comprise at least one non-linear element for producing an output signal having a component whose frequency is the sum or the difference, or a linear combination of those of the carrier wave and the modulating signal.

 It is thus known to use a diode as a nonlinear member. In this case, the mixer provides a loss of conversion, that is to say a power of the component of interest of the output signal lower than that of the baseband signal. In addition, its operation is linear (the interesting component of the output signal and the baseband signal have powers in a constant ratio) in a relatively limited range of the power of the baseband signal.

It is now known to use a transistor as a non-linear element, for example by the article "Balanced FET up-converter for 6GHz 64-QAM radio" P. BURA and D. GELERMAN published in the review IEEE
MTT-S digest 1988 (page 941). In this case, the mixer provides a conversion gain and no longer a conversion loss. In addition, its operation is linear in a larger power range of the modulating signal.

 However, in the two cases envisaged above, the mixer provides a rejection of the local signal (the ratio of the power of the output signal to the frequency of the local signal on the power of the latter) which is insufficient for certain applications. One can cite, in particular, the case of radio-relay systems comprising a 256-state quadrature amplitude modulation operation. The equipment for transmitting such beams comprises mixers followed by an amplifier and if the rejection of the local signal is insufficient, it is then necessary to provide a filter between the mixers and the amplifier to increase this rejection. Such a filter, in addition to its size and price, significantly reduces the efficiency of a circuit known as the "predistor" which compensates for the distortions introduced by the amplifier and / or the mixer. If the automatic regulation of emitted power is used, it is desirable that the rejection of the local signal be as strong as possible.

 A first object of the present invention is therefore the realization of a symmetrical microwave mixer having a significantly improved local signal rejection.

 On the other hand, as has been pointed out, the output signal has a component whose frequency is the sum of that of the carrier wave and that of the baseband signal and another component whose frequency is the difference of the same two signals. One of these components is the useful signal that is used for transmission while the other, undesirable, is the image signal. The image signal is commonly attenuated by a filter arranged after the mixer, if only to avoid its amplification. However, such a filter also attenuates the useful signal. In addition, it must be set according to the local signal frequency.

 A second object of the present invention is thus the realization of a device operating as a mixer which has a significantly improved attenuation of the image signal.

 The symmetrical microwave mixer according to the invention comprises an input coupler producing a first and a second signal modulating from an input signal, a microwave coupler producing a first and a second signal of transposition from a signal local, a first nonlinear member producing a first mixing signal from the first modulated and transposing signals, a second nonlinear member producing a second mixing signal from the second modulated and transposing signals, an output coupler generating on its output port an output signal from the mixing signals, a first and a second mixer channel extending from the first respectively the second nonlinear member to the output port, and is characterized in that it comprises in addition a symmetrical phase shift cell to produce an adjustable differential phase difference between the signals at the frequency of the local signal runting the two paths so that they recombine in opposition of phase on this access of exit.

 The rejection of the local signal is thus improved because the symmetrical phase shift cell compensates for the phase shift asymmetry of these two paths.

 In a first embodiment of the symmetrical microwave mixer, the symmetrical phase shift cell is arranged between the microwave coupler and the nonlinear members to produce from the first and second transposition signals respectively a first and a second modification signal respectively to first and second non-linear organs.

 In a second embodiment of the symmetrical microwave mixer, the symmetrical phase shift cell is disposed between the non-linear members and the output coupler to provide it with two signals from the mixing signals.

 In addition, the symmetrical microwave mixer comprises, associated with at least one of the non-linear members, an adjustment assembly for modifying the gain of this element in order to reduce, in the output signal, the power at the frequency of the local signal. .

 The rejection of the local signal is further improved by means of the adjustment assembly which makes it possible to compensate for the gain dissymmetry of the two mixer channels.

 Moreover, in the symmetrical microwave mixer, the symmetrical phase shift cell is provided to be adjusted by a control signal.

 Advantageously, in the symmetrical microwave mixer, the symmetrical phase shift cell comprises two phase shifters each phase shifting one of the signals received by it, one of the phase shifters producing a phase shift adjustable by the control signal, the other producing a fixed phase shift.

 For example, in the symmetrical microwave mixer, the adjustable phase shifter comprises a coupler type "rat-race coupler 6> / 4" whose first coupled access is loaded by a first line section of length L followed by a first element to adjustable capacity, the second coupled port is loaded by a second line section length L + \ / 4 followed by a second adjustable capacity element, these adjustable capacity elements being controlled by the control signal.

 In a first configuration of the symmetrical microwave mixer, the fixed phase shifter is identical to the adjustable phase shifter except that the adjustable capacity elements receive a fixed voltage instead of the control signal.

 In a second configuration of the symmetrical microwave mixer, the fixed phase shifter is identical to the adjustable phase shifter except that the adjustable capacity elements are replaced by fixed capacity elements.

 In addition, the symmetrical microwave mixer comprises a servo cell which produces the control signal from a level signal translating the power of said output signal to the frequency of said local signal.

 In the symmetrical microwave mixer, according to a first solution, the servocontrol cell comprises a fourth coupler taking a fraction of the output signal destined for a bandpass filter centered on the frequency of the local signal followed by a detection module providing the level signal to a control circuit which produces the control signal so as to minimize this level signal.

 In the symmetrical microwave mixer, according to a second solution, the servocontrol cell comprises a fourth coupler taking a fraction of the output signal intended for a mixing and filtering circuit which also receives the local signal to produce a combination signal whose DC component is the level signal, and comprises a control circuit which produces said control signal so as to minimize this level signal.

 In a first form of the symmetrical microwave mixer, the nonlinear members are field effect transistors.

 In a second form of the symmetrical microwave mixer, the nonlinear members are formed by a two-gate field effect transistor.

 An advantageous use of the symmetrical microwave mixer consists in producing a mixing device which comprises a distribution coupler now receiving the input signal to supply two out of phase signals of 900 to the input ports of the input couplers of a first and second a second such symmetrical microwave mixer and a combination coupler producing a transmission signal as the sum of the output signal of one of the mixers and the output signal of the other mixer shifted by 900.

 Thus the attenuation of the image signal is significantly improved.

 In addition, in this use of the symmetrical microwave mixer, the mixing device also comprises a distribution coupler for supplying said local signal to these mixers.

 In addition, in the proposed use of the symmetrical microwave mixer, the output signals of the mixers each comprising, in addition to a part of the useful signal, part of an image signal, the mixing device further comprises a symmetrical auxiliary phase shift cell. to produce an adjustable differential phase shift between the signals at the frequency of the image signal from each of the mixers so that they recombine in phase opposition in the transmission signal.

 In this use of the symmetrical microwave mixer, said auxiliary phase shift symmetric cell may be arranged either between the mixers and the combination coupler, or upstream of the mixers receiving in this case the local signal to provide it to these mixers.

 The various objects and features of the present invention will now appear more precisely in the context of non-limiting exemplary embodiments, with reference to the attached figures which represent FIG. 1, a diagram of an embodiment of the invention. symmetrical microwave mixer according to the invention, - Figure 2, a diagram of an embodiment of a phase shifter used for the implementation of the invention, - Figure 3, a diagram of a symmetrical phase shift cell. 4, a diagram of an improved embodiment of the invention; FIG. 5, a diagram of a mixing device that uses the symmetrical microwave mixer of the invention; Figure 6 is a diagram of an improved mixing device.

 The invention applies regardless of the type of mixer provided it is symmetrical, that is to say it comprises two channels which are combined on an output coupler, each channel producing a mixing signal to from a baseband signal and a carrier wave. However, it will be described in connection with the mixer mentioned in the introduction of the present application for the sake of clarity of the presentation. This is not to be considered a limitation of the invention since those skilled in the art have the necessary knowledge to transpose the invention into another type of mixer.

 The symmetrical microwave mixer shown in FIG. 1 comprises the five elements of the known structure which are the input coupler S1, the microwave coupler S2, the first T1 and the second T2 field effect transistors, the output coupler S3 and also comprises a symmetrical phase shift cell P.

 The input coupler S1, which is a power divider, receives a modulating signal in order to divide it into two fractions of substantially equal amplitude on its two output ports but out of phase by 1800. We are currently talking about an intermediate frequency coupler 3dB- 1800. The two output signals are injected on two capacitors Cfl, Cf2 to produce respectively a first Il and a second I2 modulated signal.

 The microwave coupler S2 receives a carrier wave OL to distribute it on its two output ports in a first 01 and a second 02 substantially equal power transposition signals and zero relative phase shift. This is, for example, a coupler known to those skilled in the art under the name "Wilkinson coupler" (3dB-00).

 The symmetrical phase shift cell receives the two transposition signals and produces two output signals injected on two connecting capacitors CO1, CO2 to form two modification signals J1, J2. The first modification signal J1 is obtained from the first transposition signal 01 by an attenuation operation and a phase shift operation of value. 1 in a first phase shifter. The second modification signal J2 is obtained from the second transposition signal 02 by an attenuation operation and a phase shift operation of value (f2 in a second phase-shifter) The attenuations of the two transposition signals are not a characteristic of the symmetrical cell phase shift but rather a consequence of its embodiment.They will be chosen, preferably the lowest values possible and the closest possible.The symmetrical phase shift cell is instead provided to vary the difference of phase shifts T 2 introduced on the two transposition signals.

The first transistor T1 receives on its gate a bias voltage VG1 through an inductor L1, the first modulated signal Il and the first modification signal J1. Its source is connected to the ground and its drain receives a bias voltage
VD1 via an inductor L3. The first mixing signal M1 resulting from the combination of the first modulated signal and the first modification signal is collected on an electrode of a capacitor CT1 whose other electrode is connected to the drain.

The second transistor T2 receives on its gate a bias voltage VG2 through an inductor L2, the second modulated signal I2 and the second modification signal J2. Its source is connected to ground and its drain receives a bias voltage VD2 through an inductor L4. The second mixing signal
M2 which results from the combination of the second modulated signal and the second modification signal is collected on an electrode of a capacitor CT2 whose other electrode is connected to the drain.

 The output coupler S3 produces, as output signal R, a signal proportional to the sum of the signal applied to one of its input ports and the signal applied to its other input port, which is phase shifted by 1800. also commonly used 3dB-180 coupler. This will be, for example, a coupler identified by those skilled in the art under the English term "rat-race" or "hybrid". The output coupler S3 thus receives on its two input ports the two mixing signals Ml, M2.

 The various capacitors and inductances mentioned so far are only filtering elements provided in particular for isolating the polarization power supplies of the microwave circuits.

Their implementations are part of the standard practice of those skilled in the art and they have been cited so as to give a complete description of the invention. They play an accessory role and will eventually be omitted thereafter, it being understood that identical or similar means are provided.

The first channel of the mixer extends from the gate of the first transistor T1 to the output port of the output coupler S3, while the second channel of the mixer extends from the gate of the second transistor
T2 at this same output port. It will also be recalled that the lines connecting the output ports of the input coupler S1 to the gates of the two transistors T1, T2 have equivalent lengths. The same goes for the lines connecting the microwave coupler S2 to the symmetrical cell of the phase shift P and the lines connecting this cell to the gates of the two transistors.

 Apart from the invention, that is to say by eliminating the symmetrical phase shift cell P, the local signal undergoes a phase shift due to the microwave coupler S2 and to the first channel which has a deviation from that due to this coupler and the second path which is different from 1800. This dissymmetry is due to the manufacturing dispersion of elements such as couplers and transistors and defects in the embodiment of the interconnection circuit of these elements. It follows that the rejection of the local signal is limited.

 The symmetrical phase shift cell P is precisely designed to compensate for this asymmetry. The difference of the phase shifts introduced by its first phase shifter T 1 and its second phase shifter T 2 is adjusted to reduce the phase shift difference mentioned above to a value of 1800. Thus the two signals at the frequency of the local signal using the two paths of the mixer recombine in phase opposition in the output signal R.

 The symmetrical phase shift cell generally introduces attenuation, for this reason it has been arranged between the microwave coupler S2 and the two transistors T1, T2. In this case, the attenuation of the cell can be compensated by an increase in the power of the local signal. However, without departing from the scope of the invention, it is possible to arrange it between the two transistors T1, T2 and the output coupler S3. Its accesses which received the two transposition signals 01, 02 are now connected to the drains of the two transistors T1, T2 and its accesses which produced the two modification signals J1, J2, henceforth producing the two mixing signals M1, M2. without saying that in this case the first 01 and second 02 transposition signals are respectively equal to the first J1 and second J2 modification signals.

 Returning to the previously chosen example, it appears that further improvement can be made to the mixer. Indeed, for reasons of dissymmetry already mentioned attenuation of the local signal differs depending on whether it borrows the first or the second path. The invention proposes to add a set of adjustment in one of the channels at least so as to compensate for this attenuation difference.

Thus the two signals at the frequency of the local signal borrowing the two paths of the mixer, not only recombine in phase opposition, but also have a substantially identical level. The rejection of the local signal is thus greatly improved.

 The adjustment assembly which is not shown in the figure may consist of a simple bias circuit which varies on command the bias voltage of the gate of one of the transistors T1, T2 so as to change the gain. If such a circuit is well known to those skilled in the art, it is not used for this purpose in the symmetrical mixer but rather to balance the gains of the two transistors. It is indeed illusory to want to cancel the difference of two signals of the same frequency which have a non-zero phase shift. The adjustment assembly of the invention will therefore be provided with a sufficiently fine adjustment (generally finer than in a simple bias circuit) to compensate for the relatively small attenuation gap mentioned above.

 A particular embodiment of the symmetrical phase shift cell will now be presented by way of example. One must not see the limitation of the invention but simply one of the other means that can be used for its implementation. This cell therefore comprises two phase shifters.

The first phase shifter DP1 shown in FIG. 2 has a known structure and has in particular been described in the article "Low cost design technics for semi-conductor phase shifters" by Richard W. BURNS, Russel L. HOLDEN and Raimond TANG, published in June 22, 1974 issue of IEEE MTT (page 684). It is made from an element designated by those skilled in the art under the name of "rat-race coupler 6 h / 4", where? 'Represents the wavelength for which this coupler is provided. It comprises a succession of line sections that form a ring. The first section Al has a length of 3 while the other three A2, A3, A4 have a length of the reduced impedance of these sections being substantially 1.414.The IP input input of the phase shifter is arranged between the first Al and fourth
A4 sections while the OP exit access is placed between the second
A2 and third A3 sections, both ports being designed to be connected to reduced impedance lines of value 1. On a first coupled access of the phase shifter located between the first and the second section, is also connected a first line section A12 length
L and reduced impedance of value 1 followed by a first diode D1 connected to the ground whose junction capacity varies as a function of the voltage applied on this junction. This diode and the others of the same type will be named later "varactors", as does the skilled person. On a second coupled access of the phase shifter situated between the third and fourth sections, is also connected a second line section A34 of length L + h / 4 and reduced impedance of value 1 followed by a second varactor D2 connected to ground . Both varactors D1, D2 are biased by means of an adjustable control voltage Vc. Capacitors are provided so that this control voltage does not propagate outside the phase shifter but they are not shown in the figure. In addition, the length L is chosen to be close to / 8 so that the phase shifter is the least dispersive possible.

 The operating principle will now be exposed. The wave injected on the IP input port splits into two waves of equal amplitude. The first derivative wave borrows the first section of line A1, separates into a first transmitted wave which borrows the second line section A2 and a first reflected wave which passes through the first line section A12, is reflected on the first varactor D1 which A first phase shift T 1 D1 passes again in the first line section A12 and is again injected on the ring where it is divided into two components that recombine in phase on the output port OP.La second derivative wave borrows the fourth section of line A4, separates into a second transmitted wave which borrows the third section of line A3 and a second reflected wave which passes through the second section of line A34, is reflected on the second varactor D2 which l a second phase shift T D2 passes again in the second section of line A34 and is injected again on the ring where it is divided into two components that recombine e n phase on the OP output port.

 Since the two varactors D1, D2 are identical and polarized with the same control voltage Vc, the two phase shifts T D1 T CP # D2 that they introduce into the two reflected waves are therefore equal and will be denoted #. Thus the two reflected waves recombine in phase on the output port OP, the phase shift introduced by the first phase shifter between its input port and its output port being equal to # + # L where # L is the phase delay due to a line portion of length 2L. The two waves transmitted against, recombine in phase opposition on the output port OP.

It appears as well as the phase of the signal on the exit access
OP is that of the signal on the IP input port increased by T T + T L-
The second phase shifter DP2 differs from the first only in that the two varactors D1, D2 are replaced by two capacitors C1, C2 of the same capacity. If we note T #c the phase shift introduced by these capacitors, it follows that , as in the first phase-shifter, the phase of the signal on the output port is that of the signal on the input port increased by 9 2 = 9 c +
Thus the differential phase shift of the symmetrical phase shift cell which is the difference of the phase shifts introduced by each of the phase shifters is equal to S and can be adjusted by varying by means of the control voltage Vc.

 In an alternative embodiment of the second phase shifter, the two capacitors are replaced by a third and fourth identical varactor polarized by means of a fixed voltage. In this case the temperature variations which produce the same effects on the phase shifts produced by the four varactors are canceled in the differential phase shift. The fixed polarization voltage of the third and fourth varactors will advantageously be chosen in the middle of the range of variation of the control voltage Vc.

 The symmetrical phase shift cell P is shown diagrammatically in FIG. 3. The first transposition signal 01 is applied to the input port of the first phase shifter via a first isolation capacitor C11. The first modification signal J1 is derived from the output port of the first phase shifter via the first link capacitor CO1. The second transposition signal 02 is applied to the input port of the second phase shifter DP2 via a second isolation capacitor Ci2. The second modification signal J2 is derived from the output port of the second phase shifter via the second CO 2 bond capacitor.

The isolation and connection capacitors are designed to isolate the different DC voltages, in particular the control voltage, which are present in the mixer. Advantageously, the two isolation capacitors will be chosen from the same capacity as well as the two connecting capacitors.

 As a numerical example, the following mixer performance is presented for a local signal frequency ranging from 6.4 to 7.1 GHz.

 - center frequency: f = 6.75 GHz.

 o - Cl = C2 = 2.2pF.

 C. It Cil C01 = Col = 4.7pF.

 The differential phase shift in this case varies at the center frequency from -17 to 470 for a control voltage variation of 0 to 35V. For a determined control voltage, the differential phase difference does not vary by more than 50 in the variation range of the local signal frequency.

 Furthermore, at the center frequency, for a local signal power of 16dBm, the rejection of the local signal reaches 60dB given the precise adjustment provided by the adjustment assembly.

According to an additional characteristic of the invention, the control voltage is automatically adjusted by means of a servocontrol cell shown in FIG. 4. This cell comprises a fourth coupler S4, for example a 10 dB coupler, which receives the signal of output R on its input port Ae, transmits a fraction on its coupled access Ac and transmits the remainder on its output port
As. The coupled access Ac is connected to a band-pass filter LP, for example with dielectric resonators, centered on the frequency of the local signal. The bandpass filter is followed by a detection module
MD which provides a signal of level N whose value is a function of the amplitude of the signal applied to its input. This module will take the known form, for example, of a diode DR followed by a capacitor CR connected to the ground. parallel to a resistor RR, the level N signal being obtained at the common point of these three elements. The servocontrol cell finally comprises a DC control circuit which produces the control voltage Vc so as to minimize the N level signal that it receives on its input.

 In an alternative embodiment of the control cell not shown in the figure, the BP bandpass filter and the detection module MD are replaced by a mixing and filtering circuit. This circuit receives the local signal OL and the signal from the coupled access of the fourth coupler S4 to perform a nonlinear combination (as does a mixer) and thus produce a combination signal. This combination signal has in particular a DC component which results from the local signal and the component of the output signal R at the frequency of the local signal. The circuit therefore further comprises a filter for isolating this DC component which is a function of the level of the component of the output signal at the frequency of the local signal and which now becomes the previously mentioned level signal.

 The advantage of this variant embodiment lies in the fact that the elements that compose it are independent of the frequency of the local signal. It is therefore not necessary to provide an adjustment of these elements following a change in this frequency.

 The symmetrical microwave mixer has been presented by adopting field effect transistors T1, T2 as mixing elements themselves. This is not a limitation of the invention that applies regardless of these elements provided that they are non-linear devices producing an output signal having at least one component at a frequency equal to the sum or unlike the signals they receive. It is thus possible to consider replacing the two transistors with a bi-gate transistor whose two gates each correspond to the gate of one of the single gate transistors.

 The symmetrical microwave mixer will find an advantageous use in the production of a mixing device having a strong attenuation of the image signal.

This device represented in FIG.
MHS1 and a second MHS2 symmetrical microwave mixers as described above, a distribution coupler SR and a combination coupler SC. The distribution coupler SR receives the input signal IF which it distributes in two out of phase signals of 900 each applied to the input port of the input coupler of one of the mixers
MHS1, MHS2. It is a 3dB-9O0 coupler, for example, working at the frequency of the baseband signal. The combination coupler
SC receives the output signals from each of the mixers MHS1, MHS2 and produces an emission signal E as the sum of one of these signals and the other phase-shifted by 900. This is, for example, a coupler 3db-900 known under the name of "Lange coupler". Moreover, the local signal is provided to the two mixers, for example by means of a distribution coupler SD such as a coupler "Wilkinson" 3dB-O0 which distributes this signal without phase shift.

 It thus appears that the useful signals from the two mixers recombine in phase on the output port of the combination coupler SC, while the image signals from the mixers recombine in phase opposition on the same output port.

The choice of the wanted signal and the image signal is made by connecting the mixers to the output ports of the SR distribution coupler and to the input ports of the combination coupler
SC.

According to an additional feature of the mixing device shown in Figure 6, it further comprises a symmetrical PD auxiliary phase shifting cell such as P described above. This cell is introduced, for example, between the mixers and the combination coupler, that is to say that its input ports each receive one of the output signals of the mixers.
MHS1, MHS2 and that its output ports are each connected to one of the input ports of the combination coupler SC. This arrangement has the same characteristics as those of the mixer provided with a symmetrical phase shift cell, namely a significant increase in attenuation of the image signal, to the detriment of a slight lowering of the rejection of the local signal.

 Indeed by taking the numerical example given above we obtain in this case a local signal rejection of 50dB and an attenuation of the image signal of 29dB.

 Another solution is to have the PD symmetrical phase shift cell not between the mixers and the combination coupler, but upstream of the mixers. In this case, this cell receives the local signal on its two input ports, its two output ports being each connected to the input port of the microwave coupler of one of the mixers.

 Furthermore, it is possible to produce a control circuit, homologous to the servo control cell of the mixer, which automatically adjusts the symmetrical cell DP of the device as a function of the level of the transmission signal E at the frequency of the image signal .

The types of couplers mentioned in the present description are purely indicative and can be modified without departing from the scope of the invention. Thus, in a symmetrical microwave mixer, it is possible, for example, to invert the phase shifts of the microwave coupler S2 and the output coupler.
S3. Any combination of the 3 couplers S1, S2, S3 of the mixer which produce an in-phase combination on the output port of the output coupler S3 of the components of the mixing signals M1, M2 at the frequency of the wanted signal and a combination in opposition of phase of the components of these signals at the local signal frequency may be suitable.

 It will be noted that the mixer and the mixing device are well suited to an embodiment in integrated form, such as the monolithic microwave integrated circuit (MMIC).

Claims (19)

1 / symmetrical microwave mixer comprising an input coupler (S1) producing a first (I1) and a second (I2) signal modulated from a modulating signal, a microwave coupler (S2) producing a first (01) and a second (02) transposition signal from a local signal (OL), a first non-linear element (T1) producing a first mixing signal (M1) from said first modulated signals (I1) and transpositions (01) a second nonlinear member (T2) producing a second mixing signal (M2) from said second modulated (I2) and transposing (02) signals, an output coupler (S3) producing on its output port a signal of output (R) from said mixing signals, a first and a second channel of said mixer extending from said first (T1) respectively said second (T2) non-linear member to said output port, characterized in that it further comprises a symmetrical cell of phase shift (P) for p producing an adjustable differential phase difference between the signals at the frequency of said local signal (OL) borrowing said channels so that they recombine in phase opposition on said output port.
2 / symmetrical microwave mixer according to claim 1, characterized in that said symmetrical phase shift cell is disposed between said microwave coupler (S2) and said non-linear members to produce from said first (01) and second (02) transposition signals respectively a first (J1) and a second (J2) modification signal respectively to said first (T1) and said second (T2) non-linear organ.
3 / symmetrical microwave mixer according to claim 1, characterized in that said symmetrical phase shift cell is disposed between said non-linear members (T1, T2) and said output coupler (S3) to provide it with two signals from said mixing signals (M1, M2).
4 / symmetrical microwave mixer according to any one of claims 1 to 3, characterized in that it comprises, associated with at least one of said non-linear members (T1, T2), a set of adjustment for changing the gain of this member for reducing, in said output signal (R), the power at the frequency of said local signal (OL).
5 / symmetrical microwave mixer according to any one of claims 1 to 4, characterized in that said symmetrical phase shift cell (P) is provided to be adjusted by a control signal (Vc).
6 / symmetrical microwave mixer according to claim 5, characterized in that said symmetrical phase shift cell comprises two phase shifters (DP1, DP2) each phase shifting one of the received signals (01, 02) by said cell, one of said phase shifters ( DP1) producing an adjustable phase shift by said control signal (Vc), the other (DP2) producing a fixed phase shift.
7 / symmetrical microwave mixer according to claim 6, characterized in that said adjustable phase shifter (DP1) comprises a coupler type "rat-race coupler 6/4" whose first coupled access is loaded by a first line section (A12) length
L followed by a first adjustable capacity element (D1), whose second coupled access is loaded by a second line section (A34) of length L + / 4 followed by a second adjustable capacity element (D2), said elements with adjustable capacity being controlled by said control signal (Vc).
8 / symmetrical microwave mixer according to claim 7, characterized in that said fixed phase shifter (DP2) is identical to said adjustable phase shifter (DP1) except that said adjustable capacity elements receive a fixed voltage instead of said control signal.
9 / symmetrical microwave mixer according to claim 7, characterized in that said fixed phase shifter (DP2) is identical to said adjustable phase shifter (DP1) except that said adjustable capacity elements are replaced by fixed capacity elements (C1, C2).
10 / symmetrical microwave mixer according to any one of claims 5 to 9, characterized in that it comprises a servocontrol cell which produces said control signal (Vc) from a level signal (N) reflecting the power of said output signal (R) at the frequency of said local signal (OL).
11 / symmetrical microwave mixer according to claim 10, characterized in that said servocontrol cell comprises a fourth coupler (S4) taking a fraction of said output signal (R) to a band-pass filter (BP) centered on the frequency of said local signal (OL) followed by a detection module (MD) supplying said level signal (N) to a control circuit (CC) which produces said control signal (Vc) so as to minimize said signal of level (N).
12 / symmetrical microwave mixer according to claim 10, characterized in that said servocontrol cell comprises a fourth coupler (S4) taking a fraction of said output signal (R) to a mixing and filtering circuit which also receives said local signal for producing a combination signal whose DC component is said level signal (N), and comprises a control circuit which produces said control signal (Vc) so as to minimize said level signal (N).
13 / symmetrical microwave mixer according to any one of the preceding claims, characterized in that said non-linear members are field effect transistors (T1, T2).
14 / symmetrical microwave mixer according to any one of claims 1 to 12, characterized in that said non-linear members are formed by a field effect transistor with two gates.
15 / Use of the symmetrical microwave mixer according to any one of the preceding claims for the production of a mixing device, characterized in that it comprises a distribution coupler (SR) now receiving said input signal (IF) for providing two out of phase signals of 90C to the input ports of the input couplers of a first (MHS1) and a second (MHS2) such symmetrical microwave mixers and a combination coupler (SC) producing a transmission signal ( E) as the sum of the output signal of one of said mixers and the output signal of the other mixer shifted by 900.
 16 / Use of the symmetrical microwave mixer according to claim 15, characterized in that said mixing device also comprises a distribution coupler (SD) for supplying said local signal (OL) to said mixers (MHS1, MHS2).
17 / Use of the symmetrical microwave mixer according to claim 15 or 16, characterized in that the output signals of said mixers each comprising, in addition to a portion of the useful signal, a portion of an image signal, said mixing device further comprises a symmetrical auxiliary phase shift (PD) cell for producing an adjustable differential phase shift between the signals at the frequency of said image signal from each of said mixers (MHS1, MHS2) so that they recombine in phase opposition in said transmission signal ( E).
 18 / Use of the symmetrical microwave mixer according to claim 17, characterized in that said auxiliary ancillary balancing cell (PD) is disposed between said mixers and said combination coupler (SC).
19 / Use of the symmetrical microwave mixer according to claim 17, characterized in that said auxiliary auxiliary phase shift (PD) cell arranged upstream of said mixers (MHS1, MHS2) receives said local signal (OL) to supply it to these mixers.
FR9014626A 1990-11-23 1990-11-23 Symmetric UHF mixer Withdrawn FR2669787A1 (en)

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US6694128B1 (en) 1998-08-18 2004-02-17 Parkervision, Inc. Frequency synthesizer using universal frequency translation technology
US8160534B2 (en) 1998-10-21 2012-04-17 Parkervision, Inc. Applications of universal frequency translation
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US8233855B2 (en) 1998-10-21 2012-07-31 Parkervision, Inc. Up-conversion based on gated information signal
US6560301B1 (en) 1998-10-21 2003-05-06 Parkervision, Inc. Integrated frequency translation and selectivity with a variety of filter embodiments
US6647250B1 (en) 1998-10-21 2003-11-11 Parkervision, Inc. Method and system for ensuring reception of a communications signal
US6687493B1 (en) 1998-10-21 2004-02-03 Parkervision, Inc. Method and circuit for down-converting a signal using a complementary FET structure for improved dynamic range
US8340618B2 (en) 1998-10-21 2012-12-25 Parkervision, Inc. Method and system for down-converting an electromagnetic signal, and transforms for same, and aperture relationships
US8190116B2 (en) 1998-10-21 2012-05-29 Parker Vision, Inc. Methods and systems for down-converting a signal using a complementary transistor structure
US7936022B2 (en) 1998-10-21 2011-05-03 Parkervision, Inc. Method and circuit for down-converting a signal
US6798351B1 (en) 1998-10-21 2004-09-28 Parkervision, Inc. Automated meter reader applications of universal frequency translation
US6813485B2 (en) 1998-10-21 2004-11-02 Parkervision, Inc. Method and system for down-converting and up-converting an electromagnetic signal, and transforms for same
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US8190108B2 (en) 1998-10-21 2012-05-29 Parkervision, Inc. Method and system for frequency up-conversion
US7826817B2 (en) 1998-10-21 2010-11-02 Parker Vision, Inc. Applications of universal frequency translation
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US7697916B2 (en) 1998-10-21 2010-04-13 Parkervision, Inc. Applications of universal frequency translation
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US6704549B1 (en) 1999-03-03 2004-03-09 Parkvision, Inc. Multi-mode, multi-band communication system
US8077797B2 (en) 1999-04-16 2011-12-13 Parkervision, Inc. Method, system, and apparatus for balanced frequency up-conversion of a baseband signal
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US7724845B2 (en) 1999-04-16 2010-05-25 Parkervision, Inc. Method and system for down-converting and electromagnetic signal, and transforms for same
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US8295800B2 (en) 2000-04-14 2012-10-23 Parkervision, Inc. Apparatus and method for down-converting electromagnetic signals by controlled charging and discharging of a capacitor
US6748220B1 (en) 2000-05-05 2004-06-08 Nortel Networks Limited Resource allocation in wireless networks
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