WO2007045669A1 - Radio module and circuit arrangement with a radio module - Google Patents

Abstract

The invention relates to a radio module (1) with a circuit arrangement connected to a power line for an operational voltage (VCC) and to an electrical signal line (2). According to the invention, the radio module may be improved with a circuit arrangement in the form of a power supply provided with a primary transistor (T1), the emitter of which is connected to a supply line at the operational voltage (VCC) and the collector of which is connected to the electrical signal line (2), a secondary transistor (T2), the emitter of which is connected to a supply line at the operational voltage (VCC) the collector of which is connected to the base electrode of the primary transistor (T1) and the base electrode of which is connected to a point on the connection between the collector of the secondary transistor (T2) and the base electrode of the primary transistor (T1) and a resistance (Rb), connected to the collector of the secondary transistor (T2) and to the other supply line at the operational voltage (VCC). The invention further relates to an arrangement with a radio module (1), a smart card (3) and a circuit arrangement connected to a power supply at an operational voltage (VCC) with an electrical signal line (2) connected between the radio module (1) and the smart card (3).

Description

description

Radio module and circuit arrangement with a radio module

In a radio module is generally an electronic component, which is used to establish a communication connection via a mobile network in a variety of areas. For example, radio modules are used for applications in the so-called machine-to-machine (M2M) environment or to support applications in the field of telematics. In addition, radio modules are used in particular in the retail business, i. H. for the transmission of voice and data by users of mobile communication terminals. Mobile communication terminals are electronic arrangements which, in addition to other components such as a display and a keyboard, also contain a radio module.

The invention relates to a radio module with a circuit arrangement, which is connected on the one hand to a potential terminal of an operating voltage and on the other hand to an electrical signal line.

Such a radio module is known, for example, in the form of the radio module TC35 from Siemens. The TC35 radio module can be used in accordance with the ETSI TS 102 221 V7.2.0 (2005-08) "Smart cards; UICC terminal interface; Physical and logical characteristics (Release 7) "are connected via a serial interface to a smart card in the form of a so-called SIM (Subsciber Identity Module) card SIM cards are used in particular within the framework of the GSM standard (Global System for Mobile Communication) are used for the personalization of mobile devices and usually have a com- complete microprocessor system including a so-called flash data memory on.

The communication between the radio module and the SIM card via the serial interface, which in addition to other lines, for example for a reset signal (Reset) o for a clock signal (Clock), in particular an electrical signal line for transmitting data and / or control signals from the radio module to the SIM card or from the SIM card to the radio module. Since the electrical signal line, also referred to as input / output or I / O line, is bidirectionally designed, the line drivers are not designed as so-called push / pull drivers to avoid possible collisions, but rather as so-called open-collector devices. or so-called open-drain driver.

Open-drain (in the case of the use of field effect transistors) or open-collector (in the case of the use of conventional bipolar transistors) circuits or drivers are generally characterized in that they can be represented in an equivalent circuit by a switch which in closed state a connection to the lower potential (LOW level), d. H. for example, produces to the mass. In the open state of the switch, however, the potential lying on it is initially undetermined and is determined only by the external circuitry.

In the known radio module, a circuit consisting of a resistor ("drain resistor" or "collector resistor") is used as the external circuit. Of the

Resistance, which is also referred to as a "pull-up" resistor due to its function, is connected, on the one hand, to a potential terminal of an operating voltage and, on the other hand, to the electrical signal line is open, ie no connection is made to the lower potential, the drain resistor ensures that the electrical signal line is pulled to the higher potential (HIGH level).

When dimensioning the drain resistance, it should be noted that a larger resistance reduces the current flowing, but increases the rise time of the voltage signal to HIGH level. Due to the specification requirement that the maximum output current on the electrical signal line must not exceed 500 μA, the drain resistance at the operating voltage of +3 V common for SIM cards must not fall below 6 kΩ. Furthermore, due to a corresponding specification, a maximum rise time to HIGH level of 1 μs must be observed.

For larger capacitive loads of the electrical signal line - z. As with longer electrical signal lines or other capacitive loads - it comes now to the prob- learning that the maximum rise time of 1 microseconds despite the use of the minimum resistance of 6 kΩ can not be met. In addition, the use of the open-drain or open-collector driver continues to cause the problem that the electrical signal line at HIGH levels is sensitive to signal crosstalk. This leads, for example in the case that the clock line is guided parallel to the electrical signal line, to a clearly visible so-called "ripple" on the electrical signal line, which has the consequence that standardized devices for testing the SIM interface errors on the electrical signal line Report .

The invention has for its object to provide a radio module with a simple circuit arrangement, the a wide Going trouble-free signal transmission via the electrical signal line allows.

This object is achieved according to the invention in that the circuit arrangement is a current source having a primary transistor whose emitter is connected to the one potential terminal of the operating voltage and whose collector is connected to the electrical signal line, a secondary transistor whose emitter with the one potential connection the operating voltage is connected, whose collector is connected to the base of the primary transistor and whose base is connected to a point of connection between the collector of the secondary transistor and the base of the primary transistor, and with a resistor connected to the collector of the secondary transistor and connected to the other potential terminal of the operating voltage.

The transistors used are preferably bipolar transistors. It should be noted that in the case of a positive operating voltage pnp transistors are used, while at a negative operating voltage npn transistors are used.

The radio module can, as already described above, be connected via the electrical signal line, for example with a SIM card. The electrical signal line is preferably designed as a so-called open-drain or open-collector line, ie, the electrical signal line can be connected at both ends with a lower potential terminal, preferably ground. Alternatively, the two ends of the electrical signal line can assume a high-impedance state, in which case the output current on the electrical signal line is determined by the circuit arrangement in the form of the current source. This generates a stream, which due to the capacitive loads leads to a voltage corresponding to the specified HIGH level. This allows data and / or signal transmission from or to the radio module via the electrical signal line.

The radio module according to the invention is preferred because it enables a robust and insensitive signal transmission between the radio module and the SIM card via the electrical signal line. In particular, the problems mentioned above in connection with the crosstalk of signals of the clock line to the electrical signal line and with respect to the achievement of the required rise time are avoided. At the same time, the circuit arrangement of the radio module according to the invention is simple and inexpensive to implement.

Compared with the use of known standard current sources, the solution according to the invention is distinguished by the fact that it avoids the fundamental disadvantage of such current sources that they have a voltage drop within the current source of approximately 0.7 V at a temperature of 25.degree , Since the SIM cards commonly used in conjunction with wireless modules operate with an operating voltage of 3 V or 1.8 V, thus results in the use of a standard power source at an operating voltage of 3 V or 1.8 V, a maximum HIGH Level of 2.3 V or 1.1 V. At the same time corresponds to the minimum permissible HIGH level according to a definition in the specification mentioned above at least 70% of the operating voltage, ie 2.1 V and 1.26 V. Thus, at an operating voltage of 3 V, the so-called Storabstand, ie the difference between the maximum and the minimum HIGH level at 25 ° C only 0.2 V amount. This value worsened further as the temperature increased, since the standard current sources have the temperature dependence of the base-emitter voltage of ty- typically -2 mV / K is not compensated. At an operating voltage of 1.8 V, even at an ambient temperature of 25 ° C, the specified minimum HIGH level of 1.26 V could not be maintained.

Furthermore, the solution according to the invention is also advantageous over other current sources with a low voltage drop (so-called "low-drop current sources") Such a current source could be realized, for example, by replacing the secondary transistor with a further resistor in comparison to the radio module according to the invention The voltage at the base of the primary transistor set by means of this voltage divider, in addition to the base-emitter voltage of the primary transistor, results in the voltage at an additional resistor connected upstream of the emitter of the primary transistor If the SIM interface of the radio module is constant, the voltage at the additional resistor connected upstream of the emitter of the primary transistor is also constant, and thus also the emitter current, which is deducted from the (low) base current, the output current of the current source e corresponds to the electrical signal line. Due to the optional adjustability of the voltage at the base of the primary transistor, in contrast to the standard current sources described above

Power source with low saturation voltage (ie a low-drop power source) realized. The disadvantage of this circuit arrangement, however, is the massive dependence of the output current in the electrical signal line on the temperature drift of the base-emitter voltage of the primary transistor, which amounts to approximately -2 mV / K. For example, at a voltage of 100 mV at the emitter of the primary transistor upstream resistance and a temperature change of +50 ° C results in a current change of + 100%. This means that this circuitry is only useful in low temperature environment environments.

In a particularly preferred embodiment, the radio module according to the invention has a further resistor which is connected, on the one hand, to a point of connection between the one potential terminal of the operating voltage and the emitter of the primary transistor and, on the other hand, to the emitter of the secondary transistor. This embodiment is preferred because it provides a current relationship between the current through the secondary transistor ("cross current") and the output current through the primary transistor, where the output current of the primary transistor is greater than the cross current through the secondary transistor This is particularly advantageous in the case of battery-operated radio modules, since this limits the crossflow flowing through the resistor, which generates a corresponding power loss the transistors used, for example, be determined empirically or by simulation.

In a further preferred embodiment of the inventive radio module, the primary transistor corresponds in its electrical properties to the secondary transistor. This embodiment is preferred because this scattering of the output current of the primary transistor are kept small in the electrical signal line due to different data of the two transistors. In addition, the current source is temperature-compensated, as the temperature dependence of the base voltages of the two transistors of -2 mV / K alternately cancel each other out. Same electrical properties of the two transistors, for example, in a simple Way can be realized by the use of double transistors in a housing. If the operating voltage is constant, then the two currents described are constant.

The invention further relates to an arrangement with a radio module, a smart card and a circuit arrangement which is connected on the one hand to a potential terminal of an operating voltage and on the other hand to an electrical signal line between the radio module and the smart card.

Such an arrangement is known for example in the form of a radio module TC 35 from Siemens, which is connected to a SIM card.

With regard to the arrangement, the present invention is based on the object of specifying an arrangement with a radio module with a simple circuit arrangement which permits a largely interference-free signal transmission via the electrical signal line.

This object is achieved according to the invention in that the circuit arrangement is a current source having a primary transistor whose emitter is connected to the one potential terminal of the operating voltage and whose collector is connected to the electrical signal line, a secondary transistor whose emitter with the one potential terminal of the operating voltage is connected, whose collector is connected to the base of the primary transistor and whose base is connected to a point of connection between the collector of the secondary transistor and the base of the primary transistor, and with a resistor, the is connected to the collector of the secondary transistor and to the other potential terminal of the operating voltage.

A smart card (often referred to as a smart card) is typically a plastic card, which may include, for example, a microprocessor, hardware logic and / or memory device, and is used for a variety of applications.

The inventive arrangement is preferred because it allows a robust and insensitive signal transmission between the radio module and the smart card via the electrical signal line. In this case, as already mentioned, in particular the problems mentioned above in connection with the overshoot of signals of the clock line to the electrical signal line and with regard to the achievement of the required rise time are avoided. At the same time, the circuit arrangement of the inventive arrangement is simple and inexpensive to implement.

In a preferred embodiment, the inventive arrangement has a further resistance, on the one hand to a point of connection between the one potential terminal of the operating voltage and the emitter of the primary transistor and on the other hand to the emitter of the secondary

Transistor is connected. This embodiment is advantageous since, as already explained in connection with the radio module according to the invention, it reduces the transverse current through the secondary transistor in comparison to the output current of the primary transistor, which correspondingly reduces the energy consumption of the arrangement according to the invention. Preferably, the inventive arrangement is designed so that the primary transistor corresponds in its electrical properties to the secondary transistor. This offers the advantage that scattering of the output current of the primary transistor in the electrical signal line due to different data of the two transistors are largely avoided.

The inventive arrangement can also be designed so that the electrical signal line connects a microprocessor of the radio module and a microprocessor of the smart card. This embodiment is preferred because a smart card usually has a microprocessor and thus the microprocessor of the radio module and the microprocessor of the smart card via the electrical signal line data and / or signaling messages can exchange with each other.

In a further preferred embodiment of the arrangement according to the invention, the smart card is a SIM (Subscriber

Identity Module) card. This is advantageous because SIM cards are the type of smart cards commonly used in conjunction with radio modules.

To further illustrate the invention shows

1 shows a schematic sketch of an exemplary embodiment of the arrangement according to the invention with an exemplary embodiment of the radio module according to the invention and FIG

Figure 2 in a schematic sketch another

Exemplary embodiment of the invention Order with a further exemplary embodiment of the inventive radio module.

FIG. 1 shows a radio module 1, which is connected via an electrical signal line 2 to a smart card 3 in the form of a SIM card. Further connections designated as SIM clock, SIM reset, SIM operating voltage and SIM ground are not shown in FIG. On the side of the radio module 1 is located at the end of the electrical signal line 2, a switch 4, which establishes a connection of the electrical signal line 2 with ground potential in the closed state. Equally located at the other end of the electrical signal line 2, d. H. on the side of the smart card 3, a switch 5, which also establishes a connection of the electrical signal line 2 to the ground potential in the closed state. The switches 4 and 5 can be realized in different forms. For example, these may be bipolar transistors, field-effect transistors, for example in the form of so-called MOSFETs, electronic switches or relays.

To the electrical signal line 2 of the SIM interface of the radio module 1, the collector of a primary transistor Tl is connected. The emitter of this transistor Tl is connected to a positive operating voltage VCC of the radio module 1. In this case, the operating voltage VCC in a smart card 3 in the form of a SIM card usually has a value of +3 V or +1.8 V. Parallel to the primary transistor Tl is the one potential terminal of the operating voltage VCC with the emitter of a secondary Transistor T2 connected. The collector of the secondary transistor T2 is connected to the base of the primary transistor Tl. Furthermore, the base of the secondary transistor T2 is connected to a point of connection between the collector of the secondary transistor T2 and the Base of the primary transistor Tl and also connected via a resistor Rb to the other potential terminal of the operating voltage VCC.

Now, if both switches 4 and 5 are opened, the generated

Circuit arrangement in the form of a current source, an output current which flows from the collector of the primary transistor Tl to the electrical signal line 2. Due to a capacitive load given inter alia by the electrical signal line 2, a voltage signal is generated which, with suitable dimensioning of the two transistors T1 and T2 and of the resistor Rb and depending on further potential capacitive loads to be taken into account, generates a voltage signal which corresponds to the voltage for the e- lectric signal line 2 of the SIM interface specified HIGH level corresponds. If one potential connection of the operating voltage VCC has a value of +3 V, a HIGH level in the range between +2.1 and +3 V must be observed in accordance with the specification mentioned at the outset.

Due to the realization of the electrical signal line 2 in the form of a so-called "open-drain driver" possible collisions are avoided when using conventional push / pull drivers, since both the radio module 1 and the smart card 3 by means of the switch 4th or the switch 5, the electrical lectric signal line 2 each active only in the direction of the LOW level, ie in the considered case in the direction of mass, can pull.

Through the use of double transistors in a housing can be achieved in a simple manner that the primary transistor Tl corresponds in its electrical properties of the secondary transistor T2. This has the consequence that the output current of the primary transistor Tl in the electrical Signal line 2 is identical to the current determined by the resistor Rb current through the secondary transistor T2.

FIG. 2 shows, in a schematic sketch, another exemplary embodiment of the arrangement according to the invention. In this case, the arrangement of the exemplary embodiment of Figure 2 differs from that of Figure 1 by the before the emitter of the secondary transistor T2 inserted further resistor Re. Compared to the arrangement of Figure 1, this arrangement offers the advantage that a relationship between the

Cross-current through T2, which flows through the resistor Rb, and the output current through the primary transistor Tl results in the e- lectric signal line 2. In this case, the output current through the primary transistor Tl is greater than the cross-flow through the secondary transistor T2. This makes it possible to realize a high output current with simultaneously low crossflow, which reduces the power consumption of the arrangement shown in Figure 2 compared to the arrangement shown in Figure 1.

Claims

claims 1. radio module (1) with a circuit arrangement, which is connected on the one hand to a potential terminal of an operating voltage (VCC) and on the other hand to an electrical signal line (2), d a d u r c h e c e n e s in that the circuit arrangement is a current source - A primary transistor (Tl), - whose emitter is connected to the one potential terminal of the operating voltage (VCC) and - whose collector is connected to the electrical signal line (2), a secondary transistor (T2) whose emitter is connected to the one potential terminal of the operating voltage (VCC), - whose collector is connected to the base of the primary transistor (Tl) and the base of which is connected to a point of connection between the collector of the secondary transistor (T2) and the Base of the primary transistor (Tl) is connected, as well as with a resistor (Rb), - Which is connected to the collector of the secondary transistor (T2) and to the other potential terminal of the operating voltage (VCC). 2. Radio module according to claim 1, characterized by a further resistor (Re), on the one hand to a point of connection between the one potential terminal of the operating voltage (VCC) and the emitter of the primary transistor (Tl) and on the other hand to the emitter of the secondary transistor (T2 ) connected. 3. The radio module according to claim 1 or 2, characterized in that the primary transistor (T 1) corresponds in its electrical properties to the secondary transistor (T 2). 4. Arrangement with a radio module (1), a smart card (3) and with a circuit arrangement, on the one hand at a potential terminal of an operating voltage (VCC) and on the other hand to an electrical signal line (2) between the radio module (1) and the Smart Card (3) is connected, characterized in that the circuit arrangement is a power source with a primary transistor (Tl), - whose emitter is connected to the one potential terminal of the operating voltage (VCC) and - whose collector is connected to the electrical signal line (2), a secondary transistor (T2), whose emitter is connected to the one potential terminal of the operating voltage (VCC), - whose collector is connected to the base of the primary transistor (Tl) and - whose base is connected to a point of connection between the collector of the secondary transistor (T2) and the base of the primary transistor (Tl), and with a resistor (Rb), - Which is connected to the collector of the secondary transistor (T2) and to the other potential terminal of the operating voltage (VCC). 5. Arrangement according to claim 4, characterized a further resistor (Re) which is connected on the one hand to a point of connection between the one potential terminal of the operating voltage (VCC) and the emitter of the primary transistor (Tl) and on the other hand to the emitter of the secondary transistor (T2). 6. Arrangement according to claim 4 or 5, characterized in that the primary transistor (T1) corresponds in its electrical properties to the secondary transistor (T2). 7. Arrangement according to one of claims 4 to 6, d a d e r c h e c e n e c e in that the electrical signal line (2) connects a microprocessor of the radio module (1) and a microprocessor of the smart card (3). 8. Arrangement according to one of claims 4 to 7, the smart card (3) is a SIM (Subscriber Identity Module) - card.