WO2007080383A1

WO2007080383A1 - Electronic access control device

Info

Publication number: WO2007080383A1
Application number: PCT/GB2007/000038
Authority: WO
Inventors: Simon Mcgivern
Original assignee: Locca Tech Limited
Priority date: 2006-01-09
Filing date: 2007-01-09
Publication date: 2007-07-19
Also published as: GB0600314D0

Abstract

An electronic access control device comprising a receiving circuit, the receiving circuit comprising a receiver arranged to sense an electromagnetic radio frequency signal and output an analogue signal, and a data slicer arranged to convert the analogue signal into a received digital signal by comparing the analogue signal with a reference voltage and to output the received digital signal. The electronic access control device also comprises a sensitivity adjustment unit arranged to adjust the reference voltage in response to a configuration signal and a microprocessor arranged to generate an input code in response to the received electromagnetic signal and generate an output signal if the input code matches an authorisation code. The electronic access control device is capable of receiving an electromagnetic signal containing a bit-stream access code and has a signal reception sensitivity that may be easily adjusted.

Description

ELECTRONIC ACCESS CONTROL DEVICE

The invention relates to an electronic access control device and more particularly to an electronic access control device that is remotely operated by an electromagnetic signal.

An electronic access control device, such as an electronic alarm or electronic combination lock, allows a user to operate the locking or access mechanism without the use of a conventional key. It is becoming common to operate electronic access control devices using electromagnetic signals such as radio signals, in particular containing digital signals.

Such digital signals can be pickled up a circuit including an antenna circuit and a digital radio frequency signal receiver which receives the radio signal and outputs a corresponding digital signal. Such conventional radio receivers are conventionally realised as a monolithic IC.

However, the employment of such signals has created difficulties for the use of 'master signal' systems in which more than one electronic access device will respond to a master signal.

A particular difficulty for such master signal systems is that a nearby access system may be inadvertently operated when a targeted access system is being operated by a master signal.

A known approach to solving this problem is to reduce the transmission range of the master signal. However, because the receiver sensitivity of an access control system varies due to external factors (such as nearby structural features, varying levels of external noise, and other environmental conditions) the reception range will vary for a fixed transmission signal strength according to the placement of the receiver.

As a result of the aforementioned problems, it is desirable to realise an electronic access control device that may be operated using electromagnetic signals and having a signal reception sensitivity mat may be adjusted without the need for skilled installation personnel.

According to an aspect of the invention there is provided an electronic access control device comprising: a receiving circuit comprising a receiver arranged to sense an electromagnetic radio frequency signal and output an analogue signal, and a data slicer arranged to convert the analogue signal into a received digital signal by comparing the analogue signal with a reference voltage and to output the received digital signal; a sensitivity adjustment unit arranged to adjust the reference voltage in response to a configuration signal; and a microprocessor arranged to generate an input code in response to the received digital signal and generate an output signal if the input code matches an authorisation code.

Thus, the invention provides an electronic access control device capable of receiving an electromagnetic radio frequency signal containing a bit-stream access code and having a signal reception sensitivity that may be easily adjusted.

The inventor considered the possibility of adjusting the sensitivity of a radio frequency signal receiver by conditioning or modifying the analogue input signal or digital output signals of such a receiver. For example, the input sensitivity may be adjusted by means of an input filter that can be set with a trimmer device, such as a variable capacitor or inductor which may be operated using a small screwdriver. However, because of the effect of metal tools on the receiver circuit, such an adjustment may only be completed accurately using a suitable non-metallic tool. Consequently, a skilled installation person with the necessary equipment would be required to adjust the receiver sensitivity to a required setting. Another possibility might be to adjust the antenna circuit which picks up the radio signal and supplies it to the receiver circuit. However, introduction of other components into the antenna circuit degrade its performance.

The inventor has realised that, instead of modifying the signal at the input of a radio frequency signal receiver, an analogue stage which is internal to such a receiver may be used to provide the functionality of adjustable reception sensitivity. By varying the parameters by which the analogue signal is processed and converted into a digital signal within the receiver, the sensitivity of the receiver may be easily controlled. In particular, the reception sensitivity may simply be adjusted using a digital control signal. Furthermore, because the sensitivity adjustment is realised at a later stage within the receiver, maximal input signal strength may be provided to the receiver and conditioning stages before the later sensitivity adjustment stage, thereby improving the signal to noise ratio and accuracy of the receiver. The electronic access control device may further comprise a driving unit arranged to generate a drive signal in response to the output signal. Such a drive signal may be arranged to drive any of following: a solenoid; a DC motor; an alarm; an electromechanical relay; and a solid state relay. Thus, the invention enables an access mechanism to be controlled without the use of a conventional key.

The electromagnetic radio frequency signal may contain a bit-stream access code, the access code including information used to operate the access control device.

According to another aspect of the invention there is provided a method for controlling an electronic access device comprising: sensing an electromagnetic signal; outputting an analogue signal corresponding to the sensed electromagnetic signal; converting the analogue signal into a received digital signal (Rs) by comparing the analogue signal with a reference voltage (V_REF); adjusting the reference voltage (V_REF) in response to a configuration signal (CONFIG); generating an input code in response to the received digital signal (Rs); and generating an output signal (ENABLE) if the input code matches an authorisation code.

Thus, the invention provides an electronic access control device capable of receiving an electromagnetic signal containing a bit-stream access code and having a signal reception sensitivity that may be easily adjusted, hi particular, the reception sensitivity may simply be adjusted using a digital control signal.

For a better understanding of the invention, embodiments will now be described, purely by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a block diagram of an electronic access control device according to an embodiment of the invention; and

Figure 2 is a schematic of the circuitry for a receiver and a sensitivity adjustment unit of an electronic access control device according to an embodiment of the invention.

While the present invention is susceptible of embodiment in various forms, there is described and shown in the drawings presently preferred embodiments. Like reference numerals refer to like elements throughout. Referring to Figure 1, a block diagram of an electronic access control device 10 according to an embodiment of the invention is shown. The electronic access control device 10 comprises a receiver 12, a sensitivity adjustment unit 14 and a microprocessor 16. The receiver 12 comprises an antenna 18 connected to receiving circuitry 20.

The receiving circuitry 20 is arranged to receive an electromagnetic signal containing a bit-stream access code, such as a Radio Frequency (RF) signal, via the antenna 18 and condition the received electromagnetic signal so that is outputs an analogue signal corresponding to the received electromagnetic signal. In the case of a RF signal being received, the conditioning process may include any number of filtering and amplifying stages, arranged in any order and to suitably condition the signal for subsequent extraction or decoding of a bit-stream access code contained by the RF signal.

The receiver 12 also comprises a data slicer 22 which is connected to the receiving circuitry 20 and arranged such that the receiving circuitry 20 outputs the conditioned analogue signal to a first input of the data slicer 22. A second input of the data slicer 22 is connected to a reference voltage V_REF. AS a result, the data slicer 22 is arranged such that it compares the conditioned analogue signal output by the receiving circuitry 20 with the reference voltage V_REF and outputs a received digital signal Rs. When the voltage level of the conditioned analogue signal is greater than that of the reference voltage V_REF, the data slicer 22 outputs the most positive voltage it can. Conversely, when the voltage level of the conditioned analogue signal is less than that of the reference voltage V_REF, the data slicer 22 outputs most negative voltage it can. For example, with a 0 to +5V power supply, the output takes on the voltages 0 or +5, and may be interfaced to TTL logic.

The sensitivity adjustment unit 14 is arranged such that the reference voltage VREF can be adjusted in response to a configuration signal CONFIG that is supplied to the sensitivity adjustment 14. The reference voltage V_REF may therefore act as an adjustable threshold level against which the conditioned analogue signal is compared by the data slicer 22.

Through adjustment of the reference voltage V_REF, the adjustable threshold allows for a trade-off to be made between sensitivity of the receiver 12 and output noise density in the no-signal condition. Reducing the reference voltage VRE_F increases the sensitivity of the receiver 12, with a maximum sensitivity being attained when VREF is set to OV.

The data sheer 22 is connected to the microprocessor 16 so that the microprocessor 16 accepts the received digital signal Rs output by the data slicer 22. The microprocessor 16 is arranged to generate an input code in response to the received digital signal Rs and generate an output signal ENABLE if the input code matches a predetermined authorisation code.

The output signal ENABLE indicates that the received electromagnetic signal contains a bit-stream access code matching that of a predetermined authorisation code. The output signal ENABLE can then be used to activate an access device using any such suitable means. In an example embodiment, a driving unit (not shown) would be arranged to generate a drive signal in response to the output signal ENABLE, the drive signal being arranged to operate any of the following: a solenoid, a DC motor; an alarm; an electromechanical relay; and a solid state relay. In an alternative embodiment of the invention, the microprocessor 16 may be further arranged to generate the configuration signal CONFIG in response to the received digital signal Rs, as indicated by the dashed arrow CONFIG' in Figure 1.

Figure 2 shows a schematic diagram of the circuitry for a receiver 12 and a sensitivity adjustment unit 14 of an electronic access control device 10 according to an embodiment of the invention.

The circuitry for the receiver 12 consists of an RX5500 hybrid receiver RX (manufactured by RF Monolithics), an antenna ANTl, and resistors, capacitors and inductors connected to the hybrid receiver RX and antenna. The hybrid receiver RX comprises of internal receiving circuitry (not visible) and a data slicer(not visible). In particular, the input of the internal receiving circuitry is connected to pin twenty (RFlO) of the hybrid receiver RX, which is also connected to the antenna ANTl via a parallel and series arrangement of capacitors and inductors, and the output of the internal receiving circuitry is connected to pin five (BBOUT) of the hybrid receiver RX. Also, a first input of the internal data slicer is connected to pin six (CMPIN) of the hybrid receiver RX, which is also connected to BBOUT via a series arrangement of a capacitor and a resistor, and a second input of the internal data slicer is connected to pin thirteen (THLDl) of the hybrid receiver RX. The output of the internal data slicer is connected to pin seven (RXDATA) of the hybrid receiver to provide the received digital signal Rs output by the data slicer.

The circuitry for the sensitivity adjustment unit 14 consists of two Integrated Circuit (IC) analog switches, SWl and SW2, and three resistors, R50, R51, and Rl 9 of differing resistance values. More particularly, in this embodiment, the three resistors, R50, R51, and R19 have a resistance value of 15kΩ, 30kΩ, and 60kΩ respectively. The three resistors R50, R51, R19 are connected in parallel between pin thirteen (THLDl) and pin eleven (RREF) of the hybrid receiver RX, with resistors R50 and R51 also being connected in series with IC switches SWl and SW2 respectively. The enable pin EN of IC switch SWl is connected to a first digital configuration input signal RF_SEN1 and the enable EN of IC switch SW2 is connected to a second digital configuration signal PGD. Thus, the circuitry for the sensitivity adjustment unit 14 is arranged to adjust the value of resistance between pins eleven RREF and thirteen THLDl in response to the configuration input signals RF_SEN1 and PGD. By way of illustration, when the values of both RF_SEN1 and PGD are set to digital low, 0, both switches SWl and SW2 are disabled and no current may flow through resistors R50 and R51, thus resulting in an equivalent resistance of the sensitivity adjustment unit 14 of 60kΩ (the value of Rl 9). Alternatively, if for example, the value of RF_SEN1 is digital high, 1, and the value of PGD is set to digital low, 0, current may flow through resistor R50 but not through R51, and the equivalent resistance of the sensitivity adjustment unit 14 is 12kΩ (R50 and Rl 9 in a parallel arrangement).

In the present embodiment, an electromagnetic signal containing a bit-stream access code is an RF signal referred to as an On-Off Keying (OOK) encoded signal with a frequency set to approximately 434 Mega-Hertz (Mhz). When such an RF signal is transmitted by a suitable transmitter (transducer that sends radiated electromagnetic signals into space) to the electronic access control device 10, it is received by the hybrid receiver RX of the receiver 12, via the antenna ANTl .

Following reception, the RF signal is conditioned by the internal receiving circuitry of the hybrid receiver RX. hi the present example, this conditioning process comprises the steps of narrow-band surface-acoustic-wave (SAW) filtering, RF amplification, detection and low-pass filtering (LPF). In alternative examples, any suitable conditioning process may be undertaken by any such suitable circuitry or other means.

The conditioned analogue signal is then output from the receiving circuitry to the internal data slicer of the hybrid receiver via pins 5 (BBOUT) and 6 CMPIN) and compared with the voltage level that is present at the other data slicer input. As explained above, the data slicer outputs a received digital signal Rs via pin seven (RXDATA) depending on the voltage levels of the signal applied to its inputs. This received digital signal Rs may then be passed to a suitable processing unit for decoding and comparison with a predetermined code such as an authorisation code. By controlling the values of the digital configuration signals RF_SEN1 and

PGD, the equivalent resistance of the sensitivity adjustment unit 14 may be adjusted as detailed above. Thus, the reference voltage level applied to the data slicer via pin 13 (THLDl) of the hybrid receiver may be adjusted to one of four differing values, thereby adjusting the threshold level against which the conditioned signal is arranged to be compared by the comparator.

It will be apparent to the reader that any number of reference voltage levels may be provided for through simple modification of the sensitivity adjustment unit 14 circuitry so that it provides for switching between a suitable number of resistors. Simple extension of the parallel arrangement using digital switching signal as detailed above and illustrated in Figure 2 would provide for 2^N reference voltage levels digital where N is the number of digital configuration signals used.

Thus, the invention provides an electronic access control device capable of receiving an electromagnetic signal containing a bit-stream access code and having a signal reception sensitivity that may be easily adjusted. In particular, the reception sensitivity may simply be adjusted using a digital control signal.

The present invention utilises the presence of an analogue stage within the hybrid receiver to provide a method of adjusting signal reception sensitivity that does not need a skilled installation person or additional circuit tools.

In an alternative embodiment of the invention, additional circuitry may be implemented and arranged to act as a wake-up circuit for the receiver, hi this way the receiver circuit may remain in a low-power sleep mode while the wake-up circuit periodically senses for an electromagnetic signal containing a bit-stream access code. Upon detection of a relevant electromagnetic signal containing a bit-stream access code by the wake-up circuit, the wake-up circuit sends a signal to the receiver circuit to enable it. The receiver circuit then receives the electromagnetic signal containing a bit- stream access code as previously described.

Claims

1. An electronic access control device comprising: a receiving circuit (12) comprising a receiver (20) arranged to sense an electromagnetic radio frequency signal and output an analogue signal, and a data slicer (22) arranged to convert the analogue signal into a received digital signal (Rs) by comparing the analogue signal with a reference voltage (V_REF) and to output the received digital signal (Rs); a sensitivity adjustment unit (14) arranged to adjust the reference voltage (V_REF) in response to a configuration signal (CONFIG); and a microprocessor (16) arranged to generate an input code in response to the received digital signal (Rs) and generate an output signal (ENABLE) if the input code matches an authorisation code.

2. The device according to claim 1, wherein the receiver circuit (12) also comprises an antenna (18).

3. The device according to claim 1 or 2, further comprising a driving unit arranged to generate a drive signal in response to the output signal.

4. The device according to claim 3, further comprising any of the following arranged to respond to the drive signal: a solenoid; a DC motor; an alarm; an electromechanical relay; and a solid state relay.

5. The device according to any preceding claim, wherein the sensitivity adjustment unit comprises: a plurality of resistances; and at least one switch, the at least one switch being arranged to enable a least one of the plurality of resistances in response to the configuration signal (CONFIG).

6. The device according to claim 7, wherein the plurality of resistances are arranged in a parallel arrangement and a least one of the resistances is arranged in series with the at least one switch.

7. The device according to any preceding claim, wherein the processor is further arranged to generate the configuration signal (CONFIG) in response to the received digital signal (Rs).

8. The device according to any preceding claim, wherein the analogue signal output by the receiver (20) is a low-frequency analogue signal.

9. A method for controlling an electronic access device comprising: sensing an electromagnetic signal; outputting an analogue signal corresponding to the sensed electromagnetic signal; converting the analogue signal into a received digital signal (Rs) by comparing the analogue signal with a reference voltage (V_R£F); adjusting the reference voltage (V_REF) in response to a configuration signal (CONFIG); generating an input code in response to the received digital signal (Rs); and generating an output signal (ENABLE) if the input code matches an authorisation code.

10 The method of claim 9 further comprising the step of generating a drive signal in response to the output signal (ENABLE).

11. The method of claim 9 or 10 wherein the electromagnetic signal is within a radio frequency.

12. The method of claim 9, 10 or 11 wherein the configuration signal (CONFIG) is generated in response to the signal (Rs) corresponding to the comparison.