Circuit arrangement for performance check of mobile broadcast reception systems

p0001The invention relates to a mobile reception system consisting of at least one receiving antenna, which is high-frequency connection with a superheterodyne receiver, which is provided with Spiegelfrequenzunterdrükkung and having a measuring device for determining the reception level.

p0002For mobile reception systems is often necessary to perform a functional test of the entire radio receiver system. In actual use, there is often the problem that the superheterodyne receiver, the supply line between the antenna and receiver, or the antenna system suffer as even a partial loss of quality due to aging, without having to be clearly stated in the operation can. In addition, a simple to carry out functional testing is also often required for the manufacture and assembly of the broadcast receiving system. It is therefore desirable to be able to switch the system to a test mode, thereby to check the function. In particular, even with complex receivers with multiple antennas and diversity means the examination of individual components due to the often complicated accessibility of these components is extremely complex. After the art test signals are used in the test mode, with which the components of the system or the derailleur of the components are tested for their function.

p0003The patent US 4984293 describes a circuit arrangement for testing the function of a microwave receiver. The assembly includes a heterodyne receiver wherein a test signal is generated by means of a data-modulated signal and a local oscillator signal and is coupled to the input of the receiver.

p0004The object of the invention is therefore to provide a circuit arrangement which allows for a mobile receiver in accordance with the preamble of claim 1 is a functional test of mobile reception facility to receive frequencies to which the superheterodyne receiver is set in each case and that other wireless devices are disturbed by the test signals as little as possible ,

p0005This object is achieved by the characterizing portion of claim 1.

p0006A particular advantage of an arrangement according to the invention is that only a discrete test signal is transmitted to the frequency to which the receiver is tuned. This ensures that in the test mode, the receiving frequency can be selected on a frequency gap, which does not appear audible as occupied with a reception signal in the receiver. Especially with the car radio receivers, it is necessary that the system can be checked at any reception point with any signal assignment of the frequency range by broadcasters or the like in their function. Furthermore, this ensures that the test signal is emitted by selecting a transmitter gap solely on this frequency, are not matched to the adjacent receiving systems, and thus the risk of interference to other receivers is excluded. In practice, each having a plurality of channels gaps can be found in the broadcast bands, so you can check this selective functional testing across the entire frequency band.

p0007The invention is described below with reference to figures. Show it:

p0008Fig. 1: Mobile receiving system with a superheterodyne receiver 1, with the circuit arrangement 2, which the oscillator signal 8 is of the superheterodyne receiver 1 supplied with oscillator 7 at the intermediate frequency of the receiver, a frequency converter 3 and the substantially capacitively acting coupling means 33 to the receiving antenna 5, which the RF output signal 12 (test signal) receives. The function of the system is done by displaying the intermediate frequency signal in the superheterodyne receiver.

p0009Fig. 2: Mobile receiving system as shown in Figure 1 with implemented in the receiver circuitry 1 2, but with a by self-excitation of the system with control device 17 (restrictor) generated RF output signal 12.

p0010Fig. 3: Mobile receiving system according to Figure 1 but with feed of the oscillator signal 8 to the circuit arrangement 2 via the RF connection cable (antenna cable) 14 and with a filter device 4 for suppressing the image frequency..

p0011Fig. 4: Mobile receiving system with antenna diversity means and selective auditing of the individual diversity antennas 5,5 ', 5 "by switching the switch 26 from the diversity mode in the test mode, the selective test is performed with switching signal generator 31, the Schaltsignalauswerter 27 in. the circuitry 2, which further switches the antenna switch 24 sequentially.

p0012Fig. 5: Mobile receiving system according to Figure 2, but with feeding the oscillator signal 8 and the intermediate frequency signal 11 of the superheterodyne receiver for circuit 2 via the antenna cable 14 and with signal points 16 and 18 for coupling or decoupling of these signals..

p0013Fig. 6: Mobile receiving system as shown in Figure 4, but with only one radio frequency link 14 between the seals affixed on the diversity processor circuitry and the superheterodyne receiver..

p0014In FIG. 1, consisting of the receiving antenna 5 and the superheterodyne receiver 1 broadcasting receiving system 20 is shown. The superheterodyne receiver 1 is connected at high frequency to the receiving antenna. 5 The oscillator signal of the superheterodyne receiver 8 1, which is generated in the oscillator 9 of the receiver is, in circuit arrangements according to the invention a frequency converter 3 which is disposed in the circuit 2 is supplied. The frequency converter 3 is additionally an IF carrier signal 32 supplied, the frequency of the center frequency of the IF signal 11 of the superheterodyne receiver as closely as possible. In the frequency converter 3. Thus, an RF output signal is generated 12 (test signal) whose frequency is derived from the oscillator frequency of the superheterodyne receiver and the intermediate frequency carrier wave 32, and thus corresponds to the reception frequency to which the superheterodyne receiver is tuned, so that at least within the evaluation bandwidth the level meter 10.

p0015About the coupling device 33, the RF output signal 12 of the frequency converter 3 loosely defined amplitude, eg., Via a capacitive coupling 21, coupled to the receiving antenna 5 or directly to the receiver input. By forcibly existing in superheterodyne receiver image rejection 4 to avoid the image frequency reception, the resulting forcibly in the frequency converter 3 image frequency is suppressed. In the superheterodyne receiver, the received signal 1 13 with the aid of the oscillator signal 8 is converted in a mixer 15 to the intermediate frequency. The intermediate frequency signal 11 passes through the IF filter 19. The measuring device 10 for detecting the reception level thus enables the measurement of the reception level at the reception frequency as the intermediate frequency signal 11 is an accurate representation of the received signal as long as no limitation or regulation of the reception level in the receiver to the done measuring 10th This detection level can then be compared to the prior art, with a desired value. If the detection level in a predetermined range of the desired value, thus the functioning of the receiving equipment 20 is determined.

p0016With the circuit arrangement of the invention may advantageously have a plurality of functional tests are carried out: for example, whether the superheterodyne receiver is working correctly, if all connections, including RF interconnections or other signal lines between the receiving antenna, circuitry and receiver are closed if the supply voltage as present on the circuit arrangement or antenna amplifiers abuts whether an optionally present antenna amplifier operates, whether in multi-antenna diversity means the antenna switch is functioning properly or whether printed on the disk or inserted in the laminated glass antenna structures conductor interruptions are given.

p0017The result of the functional test may be held in a known manner, either by measurement protocol or shown on a display or audibly, or in a combination of display options. The required depending on extent of testing target values ​​for the different frequency bases can be present here in a memory of the mobile broadcast reception system or in a data storage outside the vehicle. In the latter case, a data line between the external data storage and mobile reception system in the functional check is required. The comparison of nominal and actual values ​​and the resulting decision on whether the receiving system operates as required, is then expediently likewise operated in an external, that is separated from the receiver and carried out via a data line connected test unit.

p0018The IF carrier signal 32 may be generated by means of an oscillating at the intermediate frequency of the superheterodyne receiver oscillator 7 in circuit arrangements according to the invention in a particularly simple manner. Since the amplitude of the IF-producing oscillator 7 is constant and the amplitude of the receiver Eidgen oscillator 9 is also constant or is kept constant by a limiter, 3 results at the output of the frequency converter also an amplitude constant, so defined RF output 12th

p0019The frequency converter 3 is formed in its simplest embodiment by a serial or parallel diode. Advantageously used as frequency converter 3 a transistor as additive or multiplicative mixing stage, as the 12 can be easily selectively tapped via a switched-resonant circuit by the given by the transistor isolation between input and output. Using, as a frequency converter 3 is a transistor-balanced mixer, the requirements can be significantly reduced to the amplitude constancy of the frequency converter 3 supplied oscillator level. The oscillator level respectively generated over the tuning of the oscillator frequency must always be so great that the balanced mixer operating in switching mode. If the amplitude variations of the oscillator signal 8 is above this leads to the switching operation Ozillatorpegels, this has no influence on the amplitude of the RF output signal 12, so that for example can be dispensed with a limiter amplifier for the oscillator signal. In addition, unwanted signal components are suppressed at the output of the balanced mixer, so that through the coupling device 33 is omitted unwanted radiation of unwanted elements. The suppression of unwanted signal components at the output of the frequency converter 3 is made with a "Double Balanced Mixer" s (double symmetrical running mixer) exacerbated because both the IF-carrier signal 32 and the oscillator signal 8 compensates for the output by the Gegentaktaussteuerung. Such double balanced mixers are known as "four-quadrant multiplier" in the form of integrated circuits or as a ring mixer in active or passive versions.

p0020Particularly advantageously, use of the invention can be made when different broadcast signals to be received. A simple switch of the IF carrier signal 32 determining components of the oscillator 7 in the circuit 2 different IF carrier oscillations can be generated. If for example a mobile radio receiver system 20 checks for receiving the amplitude modulated long, medium and short-wave range in their function, is chosen as the IF carrier wave 32, the intermediate frequency of the AM receiver, which is typically 455 kHz. In case of receiving frequency-modulated broadcast signals of the VHF range to choose typical 10.7 MHz as IF carrier oscillation 32. For functional testing of mobile receivers for receiving television signals to Choose the picture carrier intermediate frequency (typically 38.9 MHz) or phonogram intermediate frequency (33.4MHz) or the color subcarrier.

p0021The IF carrier signal 32 may also be produced in that an amplifier with extremely high amplifier is used, which is not driven at its input with a signal and at the output of a resonant circuit is connected as an output filter whose resonant frequency of the IF center frequency of the superheterodyne receiver close as possible to, and that the filtered out from the background noise of the amplifier signal the IF carrier wave 32 forms.

p0022Circuitry 2, coupling means 33 and superheterodyne receiver may be arranged in close spatial proximity, whereby the required connection costs between the individual components is extremely small. Such an arrangement, however, requires correspondingly large installation spaces that are rarely available in modern automobile available.

p0023If these large required installation space is not available, one advantageously integrated, the circuit arrangement 2 in the heterodyne receiver 1 and performs the 12 of the frequency converter 3 via a high frequency line to the coupling means 33, as Fig. 2 shows.

p0024The ZF-carrier wave 32 generating module in the form of the IF oscillator 7 can be omitted when using the circuit arrangement 2 according to the invention a self-excitation of the receiving system 20 is effected as shown in FIG. 2 shows. Assuming that during the functional check, first an unoccupied reception channel is selected as the test frequency, a noise signal is received. When switching the mobile reception system on the operation of the functional test, remove the existing in the intermediate frequency amplifier section of the superheterodyne receiver intermediate frequency signal 11 is supplied with noise character of a control device in the form of an amplitude limiter 17, which is as limited in its amplitude IF signal 22 to the frequency converter 3 is supplied. This amplitude 17 for example is in the frequency-modulated received signals always in superheterodyne receiver 1 in the form of an integrated circuit usually available. If the loop gain of the entire receiver system 20 is chosen sufficiently large, then there is the condition of self-excitation, because the phase condition for self-excitation by the band-limiting effect of the IF selection for signals with noise character of even one 'is. The measuring device 10 for detecting the reception level should cover the RMS (root mean square) value in this case.

p0025Fig. 3 shows a receiving system according to the invention, wherein the heterodyne receiver 1 is connected to the circuit arrangement 2 only via the antenna line 14. This RF connection line - typically performed as a coaxial line - passes the reception signal 13 received by the receiving antenna 5 to the heterodyne receiver 1 further and at the same time carries the oscillator signal 8 of the superheterodyne receiver 1 to the circuit arrangement 2. It is assumed that the input impedance of the filter 4 for image rejection not excessively attenuate the oscillator signal by suitable dimensioning, on the other hand, the oscillator signal 8 is at the output of the filter sufficiently suppressed for image rejection. Either is possible in a simple way by suitable dimensioning of the prior art.

p0026In an advantageous adjustment of the level ratios, the oscillator signal 8 is selected dominant, so that it exceeds the reception signal 13 by at least one order of magnitude. This is achieved by that the required level ratios are adjusted by suitable dimensioning of the conversion gain or the conversion loss of the frequency converter 3 and by determining the coupling loss in the coupling device 33rd Thus also the RF output signal 12 is determined in its amplitude alone by the dominant oscillator signal 8 and by the amplitude of the IF carrier oscillation 32nd

p0027The coupling device 33 is in the present invention from the receiving antenna 5, to which the RF output signal 12 of the frequency converter is coupled via an electromagnetic wave-less 3 eg. The RF output signal 12 is fed to a transmitting antenna, for example, 6th This transmission antenna 6 can be mounted at a suitable location of the vehicle and radiates the RF output 12th Is the receiving antenna 5 designed as a glass antenna, it is particularly advantageous to produce the transmit antenna 6 and the receiving antenna in a single operation in the screen printing method at ESG panes or as inlaid wires in laminated safety glass. The coupling attenuation of the coupling device 33 depends here essentially by the spatial distance of the transmitting and receiving antenna and to whose principle. Capacitive antennas are preferably capacitively excite, magnetically operating antenna preferably inductively to dock.

p0028A coupling device according to the invention 33 may also be that the RF Aüsgangssignal 12 through a small coupling capacitance (eg a few pF in the VHF range) is supplied to the terminal of the receiving antenna.

p0029The RF output signal 12 can be fed at particular designed as a disc antennas receive antennas on a printed onto the disc RF line. Lying eg several receiving antenna connectors on one side of the plate boundary, as may be the case for multi-antenna diversity systems, the RF line is also printed eg in the form of an asymmetrical coplanar line on this disc boundary and as means of branching over short distances along the antenna structures performed so that the RF output signal is capacitively coupled mainly to the receiving antenna structures. The RF printed line is appropriately finished at their end with their characteristic impedance in order to obtain approximately constant current and voltage lining along the printed RF line.

p0030At multi-antenna scanning diversity systems, for example according to Fig. 4, the receiving antennas 5,5 'and 5' 'via an antenna switch 24, which is controlled by a fault indicator, is connected via the RF connection line 14 to the heterodyne receiver first According to the invention the intermediate frequency signal 11 of the receiver 1 is the fault indicator 25 is supplied via the associated via the second RF switch 26 connecting line 23 in the diversity operation. Fault indicator 25 and the antenna switch 24 constitute the diversity processor 30. If the current bridged reception signal 13 disturbed, generates the fault indicator 25 a Antennenumschaltsignal, which is the antenna switch 24 is supplied via a further switch 26 in the circuit arrangement. 2 In functional testing operation, a switching signal generator 31 is activated in the receiver, which generates a switching signal 29th This switching signal 29 is formed in the simplest case by a dc voltage which for example is connected to the inner conductor of the second RF connection line 23 via a high impedance for high frequency choke.

p0031In the circuit arrangement 2, a Schaltsignalauswerter is 27 which is carried out in a particularly simple embodiment as a comparator. This provides in the circuit arrangement 2, the switching signal 29 for switching from the diversity operation in the function check mode is available. In the latter case, the oscillator signal 8 now is switched to the second RF connection line in the receiver-side changeover switch 26 instead of the IF signal eleventh In circuit arrangement side switch 26 the connection is broken to malfunction indicator 25 and a connection to the frequency converter 3 is produced. To be able to perform the functional test with different receiving antennas, for example, is in the switching signal generator 31, caused by coding of a specific switching signal, a sequential stepping of the antenna switch 24, wherein the decoding of the switching signal in Schaltsignalauswerter 27 takes place. This affects this particular switching signal only on the further switch 26 in the circuit arrangement 2, which is shown on the left in Fig. 4 from Schaltsignalauswerter 27 ..

p0032The receiver-side switch 26 can be replaced by a simple on / off switch is switched to the IF signal on the oscillator signal in only the function check mode. This can always be the case when the oscillator signal level is significantly greater than the IF level.

p0033In Fig. 5 and Fig. 6 embodiments of the inventive concept for single or multi-antenna diversity reception systems are presented, in which only a single RF connection line 14 exists. By using only a single RF cable to connect the functional reliability of the overall receiving system is increased because fewer RF connector contacts are required. Moreover, such Ausführungsforin is much cheaper because of the overhead of the second RF link line is omitted. Now, since a plurality of RF signals via the RF connection line need to be performed, both the receiver side as well as circuitry side signal switches 16 and 18 are necessary to avoid mutual interference of the signals.

p0034For multi-antenna scanning diversity systems such signal switches are known. In the prior art, the IF signal is additionally performed for the reception signal using only one RF connector passageway in the diversity operation. Furthermore, in addition be performed via the RF connection line a switching signal which switches from diversity operation on single antenna reception.

p0035When applying the inventive concept this signal points is transmitted an additional function so that a functional check of the entire system can be carried out.

p0036In both figures, the function check by self-excitation, as described in the discussion of Figure 2, performed. Accordingly, the reception signal, the oscillator signal and the IF signal must be in the case of the single antenna reception are performed on the account of good shielding properties usually coaxially executed RF connection line 14, wherein the multi-antenna diversity reception additionally a switching signal 29, as explained above, transmitted. The receiver-side signal splitter 16 couples in the case of a functional test, the oscillator signal 8 and the IF signal 11 to the coaxial cable 14, while the RF receive signal 13 is looped through to the receiver. At the circuit arrangement side signal splitter 18, the IF signal 11 and the oscillator signal are extracted and supplied to the frequency converter third The RF reception signal is looped through from the receiving antenna to the coax. The signal splitters are designed directionally selective or frequency-selective. To improve the selection properties of the signal splitters directionally selective Signalw can oaks are additional in frequency-selective manner in the form of directional couplers.

p0037When using signal points according to the prior art in connection with FM-Multi-antenna scanning diversity systems, the coupling or decoupling of the oscillator signal in a particularly simple manner by means of a series resonant circuit can occur. About the already required for inputting and outputting selection agent for the IF signal are no further required when the Oscillator level on the RF connection line dominated all other signals.

<u>Circuitry for functional testing of a mobile broadcast reception system</u>

LIST OF REFERENCE NUMBERS

p0038<dl id="dl0001" compact="compact"><dt>1</dt><dd>Heterodyne receiver</dd><dt>2</dt><dd>circuitry</dd><dt>3</dt><dd>The frequency converter circuitry</dd><dt>4</dt><dd>Image rejection</dd><dt>5</dt><dd>Receiving antenna, receiving antennas</dd><dt>6</dt><dd>transmitting antenna</dd><dt>7</dt><dd>IF oscillator</dd><dt>8th</dt><dd>Oscillator signal of the receiver</dd><dt>9</dt><dd>Oscillator of the receiver</dd><dt>10</dt><dd>level meter</dd><dt>11</dt><dd>IF signal of the receiver (not limited)</dd><dt>12</dt><dd>RF output signal of the frequency converter 3 of the circuit arrangement 2</dd><dt>13</dt><dd>RF reception signal</dd><dt>14</dt><dd>Connecting line receiver circuitry or receiving antenna</dd><dt>15</dt><dd>receiver mixer</dd><dt>16</dt><dd>receiver-side signal splitter</dd><dt>17</dt><dd>IF limiter</dd><dt>18</dt><dd>circuit arrangement side signal splitter</dd><dt>19</dt><dd>IF filter</dd><dt>20</dt><dd>Receiving system completely from antenna and receiver</dd><dt>21</dt><dd>capacitive coupling transceiver antenna</dd><dt>22</dt><dd>IF amplitude limited signal</dd><dt>23</dt><dd>2. coaxial connecting line</dd><dt>24</dt><dd>Antennenumschlter</dd><dt>25</dt><dd>interference detector</dd><dt>26</dt><dd>switch</dd><dt>27</dt><dd>Schaltsignalauswerter</dd><dt>28a, b</dt><dd>Switching signals for switches</dd><dt>29</dt><dd>switching signal</dd><dt>30</dt><dd>Diversity processor</dd><dt>31</dt><dd>Switching signal generator</dd><dt>32</dt><dd>IF carrier wave</dd><dt>33</dt><dd>coupling device</dd></dl>