Abstract:
A measuring device or test device is provided which includes several functional units that are interconnected. The functional units are interchangeable or can be added or omitted in a variable manner. The measuring or test device can be configured with functional units whose functional characteristics differ in terms of precision and/or quality and/or functional scope.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to a measuring or testing device with several replaceable functional units.  
       BACKGROUND OF THE INVENTION  
       [0002]     A measuring or testing device in the form of a signal generator with several functional units, which can be connected to one another in a variable manner is described, for example, in published German Patent Application No. DE 101 24 371 A1.  
         [0003]     Conventionally, measuring or testing devices of a given type (for example, signal generators, spectrum analyzers, network channel analyzers etc.) have been characterized by a different performance dependent upon their equipment package, wherein all of the measuring properties are almost always designed to be of a corresponding, relatively high quality or relatively basic quality at the same time. However, in many cases, only one or a few high-quality properties are required for a given application, wherein other properties can be designed to be considerably more basic. Hitherto, the user has been obliged to purchase a measuring or testing device with a high overall performance, even if the high performance of only a few special measuring properties has been exploited. This has been relatively uneconomical for the user.  
       SUMMARY OF THE INVENTION  
       [0004]     Therefore, in accordance with one aspect of the present invention, in one embodiment, a measuring or testing device is provided which guarantees an individual design of the performance of different measuring or testing properties.  
         [0005]     In accordance with one aspect of the present invention, in one embodiment, the functional units are replaceable and/or can be added or omitted, wherein the measuring or testing device is configurable with functional units, of which the functional properties provide a different accuracy and/or a different quality and/or a different functional scope.  
         [0006]     Examples of the different functional properties are the frequency range, display variants, noise-to-signal ratio, dynamic range, measuring rate, measurement resolution, measuring accuracy and input sensitivity of the individual functional units.  
         [0007]     For example, for a research and development application, the functional properties can be characterized by a high dynamic response and high accuracy but with a relatively slow measuring rate, because, in research and development, accuracy plays a considerably greater role than the rate of measurement.  
         [0008]     Conversely, for a production application, the functional properties may be characterized by a limited dynamic response, moderate accuracy but with a fast measuring rate, because the rate of measurement plays an extremely important role in production.  
         [0009]     For a service application in repair workshops, only a limited dynamic response and limited accuracy is generally needed for almost all functional properties, that is to say, for almost all functional units. However, for certain special measurements, some of the functional units can be designed, for example, with greater accuracy.  
         [0010]     Conversely, the measuring device can also be designed with the high-performance for only some or a few special measurements, while other measuring options, which are not needed for the measuring task, can be dispensed with.  
         [0011]     Some advantages of certain aspects of the invention are based upon a maximally-optimized design of the measuring or testing device for the respective application, wherein the user can optimize the design of a measuring or testing device purchased at the time of purchasing the measuring or testing device. In this context, cost-intensive measuring functions with a high level of performance, which the user does not require at all, can be avoided.  
         [0012]     Accordingly, a testing device can be offered as a platform, wherein the decisive functional units and/or measuring modules are available in at least two, but generally in a plurality of embodiments with different performance, so that the user can configure the measuring or testing device with the optimum suitability for the measuring tasks needed. Moreover, at a later time, the measuring or testing device can be adapted for a different application with different needs by “retrofitting” one or more functional units within a modular system. Functional units can be retrofitted even if these become available only at a later time.  
         [0013]     Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the present invention. The present invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Exemplary embodiments of the invention are described in greater detail below with reference to the drawings. The drawings are as follows:  
         [0015]      FIG. 1  shows a general exemplary embodiment of a measuring or testing device consistent with the invention;  
         [0016]      FIG. 2  shows a first concrete exemplary embodiment of a measuring or testing device consistent with the invention as a spectrum analyzer;  
         [0017]      FIG. 3  shows a second concrete exemplary embodiment of a measuring or testing device consistent with the invention as a signal generator; and  
         [0018]      FIG. 4  shows a third concrete exemplary embodiment of a measuring or testing device consistent with the invention as a network channel analyzer. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]      FIG. 1  shows an abstract presentation of a measuring or testing device  1  consistent with the invention. The illustrated measuring or testing device  1  includes several interconnected functional units  2   1 ,  2   2 ,  2   3  and  2   4 , which, in the example presented, are connected in series along a signal path  3 . However, as shown clearly in the subsequent, concrete exemplary embodiments, a parallel or independent interconnection of the functional units is also possible.  
         [0020]     One difference by comparison with conventional measuring or testing devices is that, with the measuring or testing device  1  described herein, the functional units  2   1 ,  2   2 ,  2   3 ,  2   4  are replaceable and/or the functional units  2   1 ,  2   2 ,  2   3 ,  2   4  can be added or omitted. In this context, the measuring or testing device  1  may be configurable with different functional units, of which the functional properties, indicated in  FIG. 1  by the reference numbers FE 1 , FE 2 , FE 3 , FE 4 , provide a different accuracy and/or a different quality and/or a different functional scope.  
         [0021]     As a result, the measuring or testing device  1  is differently configurable for different tasks, for example, in research and development applications, in production applications or in service applications, as appropriate for the different needs of the different tasks.  
         [0022]     By way of further explanation, three examples are described, namely, a spectrum analyzer as illustrated in  FIG. 2 , a signal generator, as illustrated in  FIG. 3 , and a network analyzer, as illustrated in  FIG. 4 .  
         [0023]      FIG. 2  shows the measuring or testing device  1  as a spectrum analyzer  20 .  FIG. 2  only refers to the primarily-relevant signal range below the intermediate-frequency level.  
         [0024]     The intermediate-frequency signal, indicated with the reference ZF, is filtered in a bandpass filter  21 . This bandpass filter  21  can be a first replaceable functional unit, wherein the functional properties in this context can be the bandwidth and/or the noise-to-signal ratio of the signal and/or the linear dynamic range and/or the input sensitivity. The bandpass filter  21  is connected to an analog-digital converter  22 . This analog-digital converter  22  is another replaceable functional unit with functional properties characterized by the dynamic range and/or the converter rate and/or the resolution and/or the accuracy.  
         [0025]     This is followed by the I/Q mixing  23  in an I/Q demodulator  24 , which conventionally includes a local oscillator  25  with two outputs with a  90 ° phase displacement, which together with the filtered and analog-digital-converted intermediate-frequency signals are supplied respectively to a mixer  27  of the I branch and a mixer  26  of the Q branch. This I/Q demodulator  24  represents a further replaceable functional unit, which is available with different bandwidth and/or different linear dynamic range and/or different I/Q imbalance etc., and can be incorporated with a different quality dependent upon the requirements for the quality of signal processing.  
         [0026]     This is followed by the digital IF filtering  28  with two low-pass filters  29 ,  30 , which can also be designed as replaceable, variable functional units, wherein the edge steepness of the low-pass filter and the aliasing-free, useful frequency range can characterize the functional properties in this context.  
         [0027]     The envelope-curve rectification  31  takes place after this in an envelope-curve rectifier  32 , which represents a further replaceable functional unit. The logarithm formation  33  takes place in a log module  34 , which represents another replaceable functional unit with different functional properties. The log module  34  is followed by a video filter  36 , in which the video filtering  35  takes place. The video filter  36  represents the next replaceable functional unit.  
         [0028]     Finally, different detectors  38  to  41 , for example, a peak detector  38 , an auto-peak detector  39 , a sample detector  40  and an RMS (Route Mean Square) detector are provided for the detection  37 . Dependent upon needs, either all four detectors are incorporated with a high-performance spectrum analyzer  20 , or only certain detectors, for example, with specialized measuring tasks, only a single detector, may be incorporated, thereby creating a spectrum analyzer for a special application.  
         [0029]     Evaluation and control are implemented via a microprocessor  42 , which can also be formed as a replaceable functional unit, wherein different processors with different computational rates, different cache memories etc. can be used dependent upon the performance of the spectrum analyzer  20 .  
         [0030]      FIG. 3  shows another exemplary embodiment, wherein the measuring and testing device in this context is provided in the form of a signal generator  100 .  
         [0031]     The signal generator  100  in the exemplary embodiment shown comprises a first baseband unit  102   a  and a second baseband unit  102   b.  Its structure is described in DE 101 24 371 A1.  
         [0032]     At their I and Q outputs, the baseband units  102   a  and  102   b  generate baseband signals according to specified standards, which can be selected by the user, for example according to the GSM standard, the GSM EDGE standard or a wideband CDMA standard. The baseband units  102   a,    102   b  can be supplied respectively with clock signals at ports  103   a  or  103   b,  with trigger signals at ports  104   a  or  104   b  and with modulation data at ports  105   a  and/or  105   b.  A digital baseband generator unit  106 , which generates the I and Q components of a further baseband signal from the digital I/Q values supplied to a port  107 , is additionally provided in the exemplary embodiment shown. The output signal of the digital baseband generator  106  can be multiplied in a multiplier unit  108 , to which the constant frequency of an adjustable local oscillator  109  is supplied.  
         [0033]     The optionally upwardly-mixed baseband signal of the digital baseband generator unit  106  is supplied via a switching unit  110   a  or respectively a second switching unit  110   b  to a digital adder  111   a  or respectively a digital adder  111   b.    
         [0034]     The output signal of the baseband units  102   a  and  102   b  or respectively of the adders  111   a  and  111   b  is supplied via a switching unit  112   a  or respectively  112   b  to a fading unit  113   a  or respectively  113   b,  which provides the baseband signal with a fading (variable fading). The functions of the fading units  113   a  and  113   b,  for example, the number, the time delay and the attenuation of the signal delay paths implemented in the fading unit, can be set by the user. The fading units  113   a  and  113   b  are connected respectively via an adder  114   a  or respectively  114   b  to a noise unit  115   a  or respectively  115   b.  The noise units  115   a,    115   b  provide the baseband signal with a noise signal which can be specified by the user, wherein, for example, the noise type and the level of the noise signal generated by the noise unit  115   a,    115   b  can be selected by the user. The output signals of the fading units  113   a,    113   b  can also be added, via a switching unit  116  connecting the adders  114   a  and  114   b,  instead of via a separate connection of the respective fading unit  113   a  or respectively  113   b,  to the assigned noise unit  115   a  or respectively  115   b,  and supplied to one of the two noise units  115   a  or respectively  115   b.  The I/Q output signals at the output of the noise units  115   a  or respectively  115   b  can be de-coupled at the ports  117   a  and  118   a  or respectively  117   b  and  118   b.    
         [0035]     The output signals of the noise units  117   a  and  117   b  can be supplied to I/Q modulators  120   a  or respectively  120   b  via addition and switching units  119   a  and  119   b.  Here also, the output signals of the noise units  115   a  and  115   b  can be added via a switching unit  121  and supplied to one of the two I/Q modulators  120   a  or respectively  120   b.  Several user-specific selection options are also available with regard to the function of the I/Q modulator  120   a,    120   b.  For example, the I/Q modulator  120   a,    120   b  can be operated in such a manner that it generates a burst sequence and the active bursts or the level of the active bursts can be selected by the user.  
         [0036]     The I/Q modulators  120   a  and  120   b  are each connected to a high-frequency unit  122   a  or respectively  122   b,  and the high-frequency signal can be picked up at a port  123   a  and/or  123   b.  For example, the output frequency or several output frequencies initiated in the sudden-frequency change process of the high-frequency units  122   a  and  122   b  can be selected by the user.  
         [0037]     A signal display  124 , which, in the exemplary embodiment shown, can be connected via the switching units  125   a  or respectively  125   b  to the output of the noise unit  115   a  or the noise unit  115   b,  is additionally provided. Alternatively, a connection of the display device  124  directly to the outputs of the baseband units  102   a  and  102   b  is also conceivable. The signal display  124  allows, for example, a presentation of the configuration diagram, so that the user can check the method of operation of the connected signal path.  
         [0038]     Furthermore, a bit-error rate tester (BERT=Bit Error Rate Tester)  126  is provided, at the input port  127  of which a signal of the device under test (DUT) can be supplied, wherein the bit-error rate of the signal can be picked up at the output port  128 .  
         [0039]     Additional functional units can also be present, and further combination variants of the functional units, which are not presented here for reasons of logical presentation, may also be possible. All of the functional units  102   a,    102   b,    106 ,  108 ,  109 ,  110   a,    110   b,    111   a,    111   b,    112   a,    112   b,    113   a,    113   b,    114   a,    114   b,    115   a,    115   b,    116 ,  119   a,    119   b,    120   a,    120   b,    121 ,  122   a,    122   b,    124  and  126  are connected to a control device  128   a,  for example, a CPU, via a control bus  129 , of which the connection to the functional units is marked with the symbol (*). The control unit  128   a  controls the interconnection and function of the individual functional units required by the user. The current interconnection of the functional units is displayed on a display device (display)  129   a,  which can be disposed, together with the control elements  130 , on the front panel of the signal generator  100 . For this purpose, a graphic functional block is assigned to each of the functional units, and the connection of the functional units is displayed on the display device  129  by means of corresponding connecting elements, which connect the functional blocks to one another. The connections of the functional blocks and the functions of the functional blocks are selected either by means of a rotary knob  131  and/or corresponding operating keys  132  or via a movable positioning element  133  (mouse).  
         [0040]     With the signal generator  100  described above, advantageously, the functional units are replaceable and/or can be added and omitted in a variable manner, so that the signal generator  100  is configurable with a different performance, the performance being dependent upon the functional properties of the functional units.  
         [0041]     For example, the functional properties of the baseband units  102   a,    102   b  are characterized by the number of codable standards, e.g. GSM, EDGE, W-CDMA, COFDM for wireless LAN etc. The functional properties of the fading units  113   a,    113   b  can be characterized by the number of delay channels, wherein each delay channel creates an additional memory requirement and therefore causes additional costs. Dependent upon the performance needed, a fading unit with a different number of delay channels can be used in the signal generator  100 .  
         [0042]     The functional property of the noise units  117   a,    117   b  can be characterized by the number of emulatable noise types (thermal noise, white noise, 1/f noise etc.).  
         [0043]     The functional properties of the I/Q modulators  120   a,    120   b  can be characterized by the bandwidth and/or the linear dynamic range and/or the I/Q imbalance and other parameters characterizing the quality of the I/Q modulators.  
         [0044]     The functional properties of the high-frequency units  122   a,    122   b  can be characterized by the bandwidth and/or the linear dynamic range and/or the output power.  
         [0045]      FIG. 4  shows a further exemplary embodiment of a measuring device  1  according to the invention. In the exemplary embodiment illustrated, the measuring device  1  is a vector network analyzer  200 . The exemplary embodiment illustrated is a 2-port-network channel analyzer. In the context of vectorial network channel analyzers, the concept as discussed herein is not limited to 2-port-network channel analyzers; on the contrary, it is particularly suitable for multi-port network channel analyzers with more than two measurement ports.  
         [0046]     A separate excitation/receiver unit  202 , and respectively  2022  is provided at each port T 1 , T 2  of the network channel analyzer. Each excitation/receiver unit  202 , and/or  2022  has at its disposal a signal generator SO 1  and/or SO 2 , with which the device under test DUT can be supplied with an excitation signal. Only one of the two signal generators SO 1  or SO 2  may be active, or both of the signal generators SO 1  and respectively SO 2  can produce an excitation signal.  
         [0047]     In the application presented, the device under test is a 2-port device, for example, a bandpass filter, an amplifier, an attenuation circuit or similar. Each of the two ports of the device under test DUT is connected via a measuring line  203 , and/or  2032  to one of the two ports T 1  or T 2  of the network channel analyzer  200 .  
         [0048]     The signal generators SO 1  and SO 2  are each connected via a variable attenuation element  203   1  and  203   2  and respective amplifier  204   1  and  204   2  to a signal distributor (signal splitter)  205   1  and respectively  205   2 . One signal branch  206   1  or respectively  206   2  is connected via a respective bridge (directional coupler)  207   1  or respectively  207   2  to the assigned port T 1  or T 2 . The other branch  208   1  or respectively  208   2  is connected to a mixer  210   1  or respectively  210   2  of a first receiver device  209   1  or respectively  209   2  of the respective excitation/receiver unit  202   1  or respectively  202   2 . The first receiver device  209   1  or respectively  209   2  therefore receives the excitation signal, whenever the associated signal generator SO 1  or SO 2  is active. Furthermore, an oscillator signal, which is generated by an internal oscillator LO 1  or respectively LO 2  of the respective excitation/receiver unit  202   1  or respectively  202   2  and supplied to the mixer  210   1  or respectively  210   2  via a signal distributor (signal splitter)  211   1  or  211   2  and an amplifier  212   1  or respectively  212   2 , is supplied to the mixer  210   1  or respectively  210   2 .  
         [0049]     Via the other signal branch of the signal splitters  211   1  and/or  211   2  and a corresponding amplifier  213   1 , or respectively  213   2 , the same oscillator LO 1  or LO 2  supplies a mixer  214   1  and/or  214   2  of a second receiver device  215   1  or respectively  215   2  of the respective excitation/receiver unit  202   1  or respectively  202   2 . The mixer  214   1  or respectively  214   2  is connected via an isolation amplifier  216   1  or respectively  216   2  and the bridge  207   1  and/or  207   2  to the assigned port T 1  and/or T 2 . Accordingly, the second receiver device  215   1  receives the signal received from the associated port T 1 , reflected from the device under test to the port T 1  or transmitted by the device under test DUT from the port T 1  to the port T 2 . The second receiver device  215   2  of the excitation/receiver unit  202   2  receives the signal reflected from the device under test DUT to the port T 2  or transmitted via the device under test DUT from the port T 1  to the port T 2 . The mixers  210   1  and  214   1  of the first excitation/receiver unit  202   1  convert the received signal into a first intermediate-frequency position with the intermediate frequency f IF1 , while the mixers  210   2  and  214   2  of the excitation/receiver device  202   2  convert the received signal into a second intermediate-frequency position with the intermediate frequency f IF2 . In this context, the intermediate frequencies f IF1  and f IF2  are not necessarily identical.  
         [0050]     The intermediate-frequency reference signal IF Ref  1  or respectively IF Ref  2  generated by the mixers  210   1  or respectively  210   2  and the intermediate frequency measured signal IF Meas  1  or respectively IF Meas  2  generated by the mixers  214   1  or respectively  214   2  is supplied to an analog-digital converter  217 , which is connected to a signal evaluation and control unit  218 , in which an evaluation of the reference signals and the measured signals is carried out. Furthermore, via the control lines  219 ,  220 ,  221  and  222 , the signal evaluation and control unit  218  controls the signal generators SO 1  and SO 2  and the oscillators LO 0  and LO 2  in such a manner that these generate a signal with predetermined frequency f SO1 , f LO1 , f SO2  and/or f LO2  and with predetermined phase φ SO1 , φ LO1 , φ SO2  and φ LO2 .  
         [0051]     The evaluation and control unit  218  is connected via further control lines  223  and  224  to the adjustable attenuation elements  203   1  and  203   2 , so that the signal amplitude of the excitation signal generated by the signal generators SO 1  and SO 2  is controllable. Since the actual amplitudes of the excitation signals are registered via the intermediate-frequency reference signal IF Ref  1  and IF Ref  2 , a control loop can be formed in this manner for the accurate control of the excitation amplitude.  
         [0052]     The control lines  219  to  223  can be combined to form a bus system  225 , in particular, a LAN bus system.  
         [0053]     In the case of the measuring device presented in  FIG. 4  in the form of a network channel analyzer  200 , the individual functional units are replaceable or can be added or omitted, wherein the network channel analyzer  200  is configurable with the functional units, of which the functional properties provide a different accuracy and/or a different quality and/or a different functional scope.  
         [0054]     In the example of the network channel analyzer  200 , the functional units consist of the different excitation/receiver units  202   1  and/or  202   2 . The number of fitted excitation/receiver units, which is determined by the number of ports of the network channel analyzer  200 , is initially flexible. If only 2-port devices under test are to be tested, (for example, amplifiers, attenuation elements, lines etc.), a 2-port network analyzer is sufficient. If this network channel analyzer were to be used, for example, in production, and always the same 2-port devices under test were to be tested, it would be pointless to equip the network analyzer with more than two excitation/receiver units. However, with a different measuring task, it is entirely possible that multi-port devices under test, for example, crossover networks, directional couplers etc. may have to be measured. Only then would it be meaningful to fit the network channel analyzer with additional excitation/receiver units. In the case of a device, which is to be used in the research and development sector, it may be meaningful to fit the network channel analyzer from the start with as many excitation/receiver units as possible, so that multi-port devices under test can also be measured.  
         [0055]     Another exemplary freedom of variation is provided by the sweep bandwidth, the linear dynamic range and/or the input sensitivity of the excitation/receiver units, that is to say, different excitation/receiver units can be offered, which provide a different performance, and, dependent upon the measurement task, several excitation/receiver units with different levels of performance can be combined. For example, if an amplifier is to be constantly excited with the same input signal at the same level, it would be pointless, to use an excitation/receiver unit with high dynamic response of the output level for this purpose. However, if the output of the same amplifier is to be measured, and if the amplification factor provides a significant frequency response, then it is important for the excitation/receiver unit, which is connected to the output of the amplifier to be measured, to provide a high input dynamic response and optionally a high input sensitivity.  
         [0056]     The invention is not limited to the exemplary embodiments described above. On the contrary, these are provided merely in order to explain the invention. The invention can be used with a plurality of measuring and testing devices for different measurement tasks.  
         [0057]     While the present invention has been described in connection with a number of embodiments and implementations, the present invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims.