UA73652C2 - Device for demodulating amplitude-shift keyed voltage signals - Google Patents

Abstract

The proposed device for demodulating amplitude-shift keyed voltage signals, which are generated by the alternate switching from the high level to the low level of the signal, contains the first and the second circuits for generating charging voltages (V2, V2) and a matching circuit that is designed for switching off the first charging voltage generating circuit (C1, i1) at the specified ratio between the charging voltage (V2) at the output of thesecond charging voltage generating circuit (C2, i2) and the output voltage (UHF) of the rectifier (D1, D2). The advantage of the proposed device is a possibility to distinguishing the variations of the level of the amplitude-shift keyed signal without essential complication of the device circuit.

Description

Description of the invention

The invention relates to a circuit device for demodulation modulated by alternately changing the amplitude 2 between a low level and a high level (amplitude-manipulated) voltage according to clause 1 of the claims.

In the development of contactless chip cards and similar devices, for example, so-called contactless labels, so-called amplitude manipulation is often used. This term refers to the processing of a high-frequency signal, in which its amplitude changes in leaps between the first and second levels under the influence of a data signal in digital form. 70 Just as in the case of data in digital form, one distinguishes between "Yes" and "No" or "1" and "0" or "go" and "Yes", one distinguishes between high amplitude and low amplitude of a high-frequency signal. At the same time, according to the state of the art, both types of modulation are used - both AZK1O00 and AZK10, the first of which means the difference between the levels of 10095, and the second - 1095. However, other values of the difference between the first and second levels are also possible, so the invention described below is not is limited to only these two familiar types of modulation. 12 The problem of amplitude manipulation is that due to a change in the distance between the transmitter and the receiver of a signal modulated in this way, even with a constant amplitude of the signal at the output of the transmitter, there are changes in the amplitude of the received signal. This is also valid for the case of changes in the space between the transmitter and the receiver.

The problem is further complicated by the fact that when using signals with return to "zero", that is, between two binary "ones", the signal returns to "zero", and signals in which return to "zero" is not provided for will be modulated and transmitted "0 "-sequences and "1"-sequences of different lengths.

Therefore, the basis of the invention is the task of developing a demodulator circuit, which, with as little expense as possible, is able to reliably recognize the change in levels between two states during amplitude manipulation.

According to the invention, this problem is solved by the features given in item 7 of the claims. The advantage of the proposed scheme is that when comparing both values of the charging voltages, the change in the modulation level is easily recognized.

Below, the invention is explained in more detail using Figs. They schematically show:

Fig.1. the first example of the implementation of the corresponding inventive scheme,

Fig. 2. contour curve of the amplitude-manipulated signal,

Fig. 3. graphs of the first and second charging voltage, y

Fig. 4. the second embodiment corresponding to the invention,

Fig. 5. example of an assessment scheme, ke,

Fig. 6. diagram of the discharge curve of Mgei, co

Fig. 7. schematic implementation of the invention, 3o Fig.8. graph of the Mgei charge curve. in

In the first corresponding inventive example shown in Fig. 1, the high-frequency voltage ONE is applied to the input of the demodulator, marked by the input terminals GA and IV. Figure 2 shows the contour curve of the amplitude module of the high-frequency voltage over time. Amplitude changes occur between a high level marked "subp" and a low level marked "Im". Thus, this rectified high-frequency input voltage ONE is applied to node U. Two charging circuits are connected in parallel to node U, which are charged with a rectified high-frequency voltage.

From" The first charging scheme consists of capacitor C1 and a current source 11, connected to the voltage node M1 in parallel with capacitor C1. Accordingly, the second charging circuit consists of a capacitor C2 and a current source i2, connected in parallel to it at node M2. The second charging circuit is connected to node B through the charging switch 49 81. This charging switch 51 is actuated by the low-frequency voltage ШМЕ, with which the high-frequency voltage ОНЕ is modulated. In the simplest case, this can be done through a diode not shown. The principle of operation of this scheme is explained below. While the amplitude of the rectified high-frequency voltage OUNE in the node

When the voltage at the input nodes M1 and M2 of the charging circuits is greater than the voltage, and the switch 51 is closed, the capacitors C1 and C2 are charged to the value of the rectified high-frequency alternating voltage ONE. At the same time, capacitors C1 and C2 sl 20 are discharged through current sources and! and i2, respectively, and the time constants of both charging circuits are selected in such a way that they are large compared to half the period of the high-frequency input voltage of the ONE, therefore, in both inputs from nodes M1 and M2 of the charging circuits, there are no significant changes in voltages (pulsations) that significantly deviate from zero-crossing of high-frequency alternating voltage.

As can be seen from Fig. 2, the amplitude of the high-frequency input voltage ONE by the moment of time 1 should be at the 29th level "subp". At the time of the MP, there is a transition to the "Im" level. This change causes switch 51 to open

HF) and separation of the second charging circuit with input node M2 from the rest of the circuit. If the time constants of the first and second charging circuits are chosen differently, then capacitors C1 and C2 are discharged at different rates. This can be ensured, for example, by setting different current values in the current sources i1 and i2 with the same values of the capacitors C1 and C2. The resulting discharge curves are shown in Fig.3. 60 As can be seen from Fig. 3, the voltage at node M2 drops much steeper than at node M1. It can also be seen from Fig. 1 that the voltage at node M1 is transformed into the voltage MT using the voltage divider Hoo. Therefore, as can be seen from Fig. 3, there is an intersection of the discharge curves M2 and Mt. Crossing point 5 can be used to indicate a transition from a high level ("sub") to a low level ("ohm"). Such a point can be registered using the scoring scheme explained below. because Fig. 4 shows another form of implementation of the demodulator scheme according to the invention. In it, you should first point out the two voltage dividers Xo and 290, which convert the voltage at node M2 into two different voltages: the voltage

MU2", also marked as "Mvidiom/", and voltage U2", also marked as "Uvidpidn".

The scheme according to Fig. 4 basically functions in the same way as the scheme according to Fig. 1. In this case, the time constant of the second charging circuit must be significantly less than the time constant of the first charging circuit, that is, the current source i2 discharges the capacitor C2 much faster than the current source i1 - the capacitor C1. This is clearly visible in Fig. b.

Signals Mviopidy and Mvidiom/ fairly accurately repeat the change in the level of the high-frequency input signal from "sub" to "mm". As in the case of the scheme according to Fig. 1, explained with reference to Fig. 3, in this version of the scheme, the values of the Mgei signal and the signal corresponding to the Mvidnpidn signal also intersect. 70 When the voltage at the node M2 due to the discharge of the capacitor C2 by the current source i2 decreases to a value lower than the value of the high-frequency input voltage ONE, the switch 5 closes again. This means that now the current source i2 additionally discharges the capacitor C1 through the resistor CI. In Fig. b, this is reflected by a steeper section of the MGEI discharge curve from the moment of time 2. Now there is a transition of the high-frequency voltage level of the ONE from "Iom/" to "subp"; capacitors C1 and C2 are charged again and, as shown in 7/5 Fig. 8, at point 5 there is an intersection of the Mgei and Mvidiom curves.

Diode 03 provides a voltage difference between nodes M1 and M2, which corresponds to the voltage drop across it. Thanks to this, the voltages at these nodal points, even with a large modulation depth, as, for example, in the case of AZK 100, when the amplitude of the high-frequency input voltage at the "mu" level reaches almost 0 Volts, change in parallel.

Thus, even with a large modulation depth, flawless registration of the moment of intersection of the Uzvidnpidy and Mgei curves is ensured.

Fig. 5 shows a possible evaluation scheme for signals: the Mgei voltage corresponding to the MT voltage, the voltage

M2", corresponding to the voltage Mvidopchy, and voltage M2", corresponding to the voltage Mvidiom. At the same time, voltage MT is applied to the inverting inputs of both differential amplifiers, and voltages Mvidpdy and Mvidiom/ - to their non-inverting inputs. The outputs of the differential amplifiers are connected to the inputs of the K5 flip-flop. At the output of the K5-trigger, a signal corresponding to a high level of "subp" or a low level of "Im" is formed. Other rating schemes may also be offered. and)

Figure 7 shows the schematic implementation of the invention using the traditional KMON technology. The input alternating voltage is applied to the input terminals GO and GO. Diodes 01-03 of the previous embodiment in this technology are made in the form of MA, M5 and M11 transistors. с зо At the output of the rectifier, a low-pass filter is provided to suppress the carrier frequency.

In contrast to the charging scheme of the previous example, a current mirror scheme is provided for the p-channel transistors RI and RO. This current mirror charges capacitors C1 and C2, to which Ge discharge circuits on p-channel transistors M8 and M10 are connected. The ratio between the charging current supplied by the current mirror and the discharge current determines the time constant for charging capacitors C1 and C2. Resistors KA, me)

K5 and K7 implement the voltage dividers already explained in connection with the previous examples, which form the signals of imgei det, mvidnidn and mvidiom.

The diodes M24 and M25 mentioned above resolve the voltages M1 and M2 as soon as the input voltage becomes lower than M1 or

M.

The M11 diode has the same function as the OZ diode described above. "

In addition to the examples of implementation described above, in this example, upon recognition of a high value in s of the modulation coefficient in the output signal, the corresponding control signal detodeph is applied to the logic element MAE. This signal controls two parallel drains M1 and MO, connected in series with ;" current mirror Ri. Current mirror RA, in turn, is connected in parallel to current mirrors RI Her

RO, thanks to which the charge current of the capacitors increases many times. This provides an undiminished detection bandwidth, as the steady state is quickly restored even with significant modulation depth. -I The evaluation of the signals of data, video and video/ is carried out similarly to the examples of the implementation of the invention described above. o The parameters of the scheme elements are given directly on the scheme. However, the invention is not limited to this example

Ge" parameters of the elements.

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From MU2 Second input node

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Claims (7)

The formula of the invention 1. A circuit device for demodulation modulated by alternately changing the amplitude between a low level and a high level (amplitude-manipulated) voltage, which contains a rectifier (01, 02; M4, M5) connected after the high-frequency input 65 (18, GA), the first charging circuit (SI, i1; C1, RI) and the second charging circuit (C2, C2, i2, i2, PO), which are connected in parallel to the output (U) of the rectifier (01, 02; M4, M5) and each of which forms the charging voltage (M1, M2), the resolving device (51; M24, M25), which resolves the charging voltages (M1, M2) at a certain ratio between the current values of the charging voltages (M1, M2) and the voltage (NO ) at the input of the rectifier (01, 02; M4, M5), as well as an evaluation circuit made with the ability to determine the modulation level by the ratio between the charging voltages (M1, M2). 2. Circuit device according to claim 1, in which the charging circuit contains a current mirror circuit (RO, P1). 3. Circuit device according to claim 1, in which the charging voltage (M1) of at least one charging circuit (C1, i1; C2, i2) is changed by a voltage converter (Hob). 4. A circuit device according to claim 1 or 2, in which the first and second charging circuits (C1, i1; C2, i2) with a pre-set ratio between the values of the charging voltages (M1, M2) are connected by a diode (03, M11) . 5. The circuit device according to one of the preceding points, in which the voltage of the second charging circuit is converted into two different voltages. b. The circuit device according to one of the preceding clauses, in which the first and second charging circuits have different discharge time constants. 7. The circuit device according to one of the previous points, which contains a switching device (MAb), which, at a predetermined value of the modulation depth, turns on the circuit (P4, MI, MO, M2, Rg) for increasing the charging current. Official bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated circuits", 2005, M 8, 15.08.2005. State Department of Intellectual Property of the Ministry of Education and Science of Ukraine. s (8) s yu (Se) so m. shi s ;" -I (95) (22) c 50 Ko) F) ime) 60 b5