FI97000B - Phase and amplitude modulation circuit - Google Patents

Abstract

The present invention relates to a circuit for phase and amplitude modulation. The modulation circuit comprises a first distribution circuit receiving the local signal, two mixers, a phase-shifting circuit, a second distribution circuit producing the output signal, these modulators and these distribution circuits incorporating one transformer each. According to the invention, all these transformers are produced by impression or etching on one or other of the faces of a same support. <IMAGE>

Description

97000

This invention relates to a phase and amplitude modulation circuit.

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Modulation circuits used in the radio frequency range, and in particular at frequencies around 900 MHz, generally include mixers and dividers. Both the dividing circuits with which the input signal can be formed into two symmetric output signals or, conversely, the sum signal from the two input signals can be formed so that the mixers are often formed around a transformer wound on a ferrite core.

15 The performance of these modulation circuits, especially in the prevention of interference radiation, depends on the phase and amplitude balance of the mixers and distribution circuits. In particular, the attenuation of the carrier is directly due to the isolation value between the local oscillator signal and the radio frequency signal of the mixers. The phase and amplitude balance of the distribution circuit modules largely depends on the symmetry of the centered transformers used. However, in the frequency range in question, it is very difficult to implement ferrite-wound transformers whose center-25 defines a faultless symmetry. In addition, such transformers are bulky elements that: interfere with miniaturization of the modulation circuit.

It is therefore an object of the present invention to provide a modulation circuit which is highly immune to interference radiation. In addition, this modulation circuit must be space-saving.

The modulation circuit according to the invention comprises a first distribution circuit 35 which receives a local signal, two mixers, a phase shift circuit, and a second distribution circuit which generates an output signal, each distribution circuit and 2 97000 mixers including a transformer. on both surfaces of the same substrate.

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In addition, the centers of the transformers of the mixers in the modulation circuit receive a DC voltage having the same value as that of the modulation signals.

The various objects and features of the invention will now be described in detail with reference to non-limiting embodiments thereof, with reference to the accompanying drawings, in which: Figure 1 shows a diagram of a known type of modulation circuit, Figure 2 shows a diagram of a known type of distribution circuit, Fig. 3 shows a circuit diagram of a mixer of a known type, Fig. 4 shows a circuit diagram of a modifier circuit transformer according to the invention, Fig. 5 shows a circuit diagram of a mixer transformer of a modulation circuit according to the invention, and Fig. 6 shows a diagram of a modulation circuit according to the invention.

The components shown in the different figures have the same reference numerals, respectively.

To better understand the invention, the structure of the modulation circuit will first be recalled with reference to Figure 1.

This modulation circuit comprises a first distribution circuit 1 which receives the local signal 2 from the local oscillator 35 and divides it symmetrically into two intermediate signals 4 and 5. The intermediate signal 5 is processed in a phase shift circuit 6 which forms a phase shifted signal 7.

3 97000 The amount of this phase shift is usually 90 °. The circuit also includes a first mixer 8 which forms a first modulated signal 9 from the intermediate signal 4 and the first modulation signal 10, and a second mixer 11 which forms a second modulated signal 12 from the phase shifted signal 7 and the second modulation signal 13. The two modulation signals 10, 13 are phased 90 ° . The circuit includes yet another distribution circuit 14 which generates an output signal by mixing two modulated signals 10 9, 12.

The distribution circuit, the electrical diagram of which is shown in Figure 2, includes a centered transformer 18, a resistor 19 connected to the terminals of the transformer ends, and a capacitor 20 connected to the center on the one hand and to the ground on the other. The reference numbers in the figure are related to the first distribution circuit 1, i.e. the local signal 2 comes to the center and the intermediate signals 4, 5 are obtained from the terminals of the transformer ends. The second distribution circuit is structurally identical to this.

A mixer, for example a first mixer 8, the electrical diagram of which is shown in Figure 3, comprises a two-winding transformer 22. The intermediate signal 4 is fed through a capacitor 25 to one end of the primary winding of the transformer 22, the other end of which is connected to ground. A secondary winding provided with a ground-connected center is connected to two diodes 24, 25 in series. The modulation signal 10 is applied to a point 30 between these diodes, and the modulated signal 9 is obtained from an intermediate point via a capacitor 26.

The phase shift circuit 6 comprises, for example, a line length 35 equal to the quarter wavelength of the local signal 2, whereby a 90 ° phase shift is obtained.

4 97000 After describing the electrical operation of this modulation circuit, an embodiment of the invention will now be described.

The modulation circuit is implemented on a substrate, such as optionally a multilayer double-sided printed circuit, or on a ceramic substrate by the "thick layer" or "thin layer" technique. All transformers are implemented by printed circuit or gravure printing techniques in accordance with the above-mentioned techniques, as described in 10 FR patent application 8903607.

A centered printed transformer will now be described, by way of example, with reference to Figure 4, which shows a transformer with two turns OB and OC, each shrink thus shrinking into one turn.

This transformer corresponds to an optimal embodiment in which the flux generated by each revolution is identical to the flux formed by the other 20, because the revolutions OB and OC are circumferential and enclose the same surface, the diagram being completely symmetrical about a vertical axis passing through the center O and the intersection of the revolutions. marked with reference number D, via.

25 In this optimal embodiment, the two coils are coils with identical leakage losses.

The intersection of the rounds can be implemented using me-30 stacked openings; the presence of metallization with respect to the transformer does not affect its operation.

The intersection of the turns can also be realized with a "shell chip" mounted on a zero resistance surface.

Performance can be optimized by reducing the space between revolutions (for example to the order of 15/100 mm).

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By reducing the width of the printed line (eg to 15/100 mm), the dimensions of the transformer can be further reduced.

5 Transformers of this type are used in distribution circuits 1, 14.

Figure 5 shows the transformer used in the mixers 8, 11. It is obtained from the above by adding an additional turn EF to the circumference of the turns of the previous transformer, whereby this 10 turns EF forms the primary winding.

When the base of the modulation circuit includes an insulating inner layer, it is possible to place the transformers on both surfaces without the risk of possible interactions.

In the modulation circuit according to the invention shown in Fig. 6, the continuous component in the modulation signals 10, 13 can be removed. If these signals come from 20 circuits in which, for example, an operational amplifier is used, the DC voltage in addition to the signal is detrimental to the two diodes of the mixer. It can be removed by using an isolation capacitor, but if the frequencies used in the modulation signal are relatively low, the capacitance of the capacitor must be large, as a result of which this component becomes bulky. The solution is to bring the same DC voltage 30 as in the modulation signals to the centers of the mixer transformers. Capacitors 32, 33 isolate this DC supply 30 with respect to radio frequency signals.

The components used to assemble the modulation circuit, such as resistors or capacitors, are components of the "surface mount components" type or are formed directly serigraphically or by another method previously mentioned. This modulation circuit can advantageously also be used as a demodulation circuit. Referring to Fig. 1, instead of the 97,000 output signal 15, a signal to be demodulated is input, and demodulated signals are received for the output of the mixers instead of the modulation signals 10,13.

The invention can be applied in particular in mobile stations for radiotelephone traffic, where the baseband modulation signals in step 10 and quadrature 13 are fed to mixers 8, 11.

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Claims (3)

97000 Patents iva at imus A modulation circuit comprising a first distribution circuit (1) receiving a local signal (2), two mixers (8, li), a phase shift circuit (6), and a second distribution circuit (14) forming an output signal (15), wherein both the distribution circuits and the mixers each include a transformer, characterized in that these transformers are implemented by printed circuit or deep-head technology 11a on either surface of the same substrate, and that the transformer centers of the mixers (8, 11) receive a DC voltage (30) equal to , which the modulation signals 15 (10, 13) have. A modulation method in which a signal (1) is used for a local signal (2), a signal (8, 11), a signal (6), and a signal (14) for an external signal (15) , varvid dessa fördelningskretsar och dessa blandare 25 omfattar vardera en transformator, känneteckn & d därav, , 11) a signal at a time (30) of 30 that is equivalent to a value in the modulation signal (10, 13).