EP1406349A2 - Active wide-band reception antenna with regulation of the receiving level - Google Patents

Abstract

The device has a passive part with output connections connected to amplifier stage input connections and reduced internal impedance if a defined reception level is exceeded. The amplifier input stage amplifying element's high impedance control port has a HF connection to the passive part. An electronic element reduces the reception level in a transfer network whose linearising input admittance is lower when the HF input signal is attenuated. The device consists of a passive part (1) whose output connections are connected to the input connections of an amplifier stage (21) and its internal impedance is reduced when a defined reception level is exceeded. The amplifier-input stage contains a 3-pole amplifying element (2) whose high impedance control port (15) has a high frequency connection to the first connection of the passive part. The amplifier has an electronic element (32) for reducing the reception level in a transfer network (31), whose linearising input admittance (7') is lower when the high frequency input signal is attenuated.

Description

The invention relates to an active broadband reception antenna, consisting of a passive antenna part 1 with a frequency-dependent effective length l _e , the output connections of which are connected to the input connections of an amplifier circuit 21 at a high frequency. Electrically long antennas or antennas that are in direct coupling with large electrical bodies have a frequency-dependent open circuit voltage when excited with an electrical field strength that is kept constant over frequency, which is expressed by the effective length l _e (f). In the frequency range above 30 MHz in particular, the antenna noise temperature T _A in terrestrial surroundings - coming from low frequencies - has dropped to such an extent that a source impedance near the optimum impedance Z _opt for the transistor is required for the bipolar transistors on the part of the passive antenna part, in order not to suffer any significant loss of sensitivity due to the transistor noise. The basic form of an active antenna of this type is shown in FIG. 2b and is known, for example, from DT-AS 23 10 616, DT-AS 15 91 300 and AS 1919749. With active broadband antennas, which are not channel-selective but on a frequency band , such as the VHF radio frequency range are broadband tuned, it is necessary to transform the antenna impedance Z _s (f) of a short radiator in Z _A (f) in the vicinity of Z _opt (see VHF range in the DT-AS 23 10 616) or to design the radiator itself in such a way that the antenna impedance Z _s (f) itself is close to Z _opt (see VHF range in AS 1919749 and radiator in). This leads to a frequency-dependent open circuit voltage at the transistor input, both in the case of electrically large and also electrically small antennas, which is expressed as a strongly frequency-dependent effective length l _e (f) of the passive antenna part, which, in conjunction with the frequency dependence of the voltage division factor between Z _opt and the deviating input resistance of the transistor results in the need to smooth the resulting frequency response of the received signal at the load resistor Z _L with the aid of an adaptation circuit at the output of the active circuit. This is also necessary to protect the subsequent receiving system against non-linear effects due to level overload.

With broadband receiving antennas, the high electrical field strengths near the transmitter can e.g. also by on-board transmitters, by intermodulation and limitation effects in the electronic amplifiers of the active receiving antenna cause strong reception interference, since this in terms of high sensitivity and in terms of broadband compliance the electrical properties are dimensioned. The technique used is usually very complex, the effort with increasing demands on the intermodulation strength increases rapidly. In the case of active receiving antennas that determine a signal level Use rectifier circuit with control circuit, but can use cheaper amplifiers be used because they are able to exceed a predetermined reception level to lower the internal gain of the active receiving antenna to act on it Interference and limiting effects in the amplifier and to avoid in the advanced circuit.

DE 43 23 014 describes an active broadband antenna in which the one to be measured Antenna impedance into the optimum using a low-loss transformation network Source impedance of the subsequent electronic amplifier to achieve an optimal signal-to-noise ratio is transformed. To protect the following reception system against Nonlinear effects from level overload is often a reduction in the internal gain the active antenna. In DE 43 23 014 the exceeding of a predetermined one Received level determined using a rectifier circuit and using a Control amplifier, the internal gain of the active antenna is lowered. This is done in the way that there is a passive, signal attenuating network that the active antenna part bridged, and the lowering of the internal gain of the active receiving antenna is done that the signal path through the electronic amplifier at its input, or at its Output or at its input and output separated by the electronic switch is. This shows the load occurring at the amplifier input due to the bridging signal damping network together with the switching measures to be installed there as annoying.

The basic form of active antennas with a transformation network at the amplifier input, such as those used as broadband antennas for the FM range, is shown in FIG. 2b and is known, for example, from DT-AS 23 10 616 and DT-AS DT-AS 15 91 300. Active antennas according to this state of the art are installed, for example, to a large extent above the high-frequency range with antenna arrangements in a motor vehicle window pane together with a heating field for the window heating, as for example in EP 0 396 033, EP 0 346 591 and in EP 0 269 723 described. The structures of the heating fields used as passive antenna part 1 are vehicle parts which were not originally intended for use as an antenna and which can be changed only slightly due to their function for heating. If an active antenna according to the state of the art is implemented on such an antenna element as in FIG. 2b, the impedance present at the heating field is to be transformed into the vicinity of the impedance Z _opt for noise adaptation with the aid of a primary matching circuit and the frequency response of the active antenna is to be transformed Smoothing using an output-side adaptation network. This procedure necessitates the relatively cumbersome dimensioning of two filter circuits, which for an advantageous overall behavior of the active antenna cannot take place separately for each filter due to the mutual dependence on one another. In addition, the amplifier circuit cannot be designed as a simple amplifying element as in FIG. 2b to achieve sufficient linearity properties, as a result of which the creative freedom of the two matching networks is significantly restricted. In addition, the design of two filters involves increased effort. Another notable disadvantage of an active antenna of this type is the load on the matching circuit connected to the heating field with a downstream amplifier if several active antennas are designed from the same heating field to form an antenna diversity system or a group antenna with special directional properties or other purposes. This disadvantageous situation is present in all antenna arrangements, the passive antenna parts of which are in appreciable electromagnetic radiation coupling to one another. For example, according to the prior art, in a multi-antenna scanning diversity system formed from the heating field, switching diodes are attached to the connection points for the antenna amplifiers formed on the heating field, which in each case only switch on the matching circuit with amplifier whose signal is switched through to the receiver and which the other connection points unlock. In such systems, this leads to a considerable outlay and to the additional requirement of switching the diodes precisely in synchronism with the antenna selection.

The object of the invention is therefore an active broadband receiving antenna according to the preamble of claim 1 so that with a given passive antenna part with assurance a high sensitivity to noise and a high linearity largely independent on the frequency dependence of the effective length and the impedance of the passive Freely selectable frequency dependence of the reception power is achieved and that an effective device for lowering the internal gain of the active antenna Given a given reception level to protect against non-linear effects is.

According to the invention, this object is achieved by the characterizing features of claim 1 solved.

The advantages that can be achieved with the invention are in particular the reduction of the economic Effort and simplicity to achieve a signal to noise ratio and optimal reception signal with regard to the risk of nonlinear effects. The high linearity of the three-pole achievable through the features of the main claim reinforcing element 2 allow lowering the internal reinforcement of the active Antenna at the exit of this element in connection with an increase achieved at the same time to design the linearizing negative feedback. Due to the loss of a primary matching network in connection with the high impedance of the amplifier circuit on the input side there is an extremely advantageous freedom in the design of complicated multi-antenna systems, whose passive antenna parts are radially coupled to one another. This results in the advantageous property that for multiple antenna arrangements the multiple coupling reception signals from a passive antenna arrangement with several connection points, which are in electromagnetic radiation coupling to each other through the formation of the active antennas there is no noticeable mutual influence of the received signals. In connection with the diversity arrangement, the switching diodes mentioned above can be used Activation of connection points where there is no signal for connection to the receiver is used, therefore advantageously eliminated.

Fig. 1:
Aktive Breitbandempfangsantenne nach der Erfindung mit einer direkt an den passiven Antennenteil 1 angeschlossenen Verstärkerschaltung 21 mit einem dreipoligen verstärkenden Element 2, mit in der Quellenleitung befindlicher Eingangsadmittanz 7 des Übertragungsnetzwerks 31 mit einstellbarem Übertragungsglied 34, z.B. in Form eines als einstellbares elektronisches Element 32 realisierten Längswiderstands, einer nachgeschalteten verlustarmen Filterschaltung 3 und einem ausgangsseitig wirksamen Wirkwiderstand 5 und Regelverstärker 33.

Fig. 2:

a) Elektrisches Ersatzschaltbild einer aktiven Breitbandempfangsantenne nach der Erfindung mit Serienrauschspannungsquelle u_r und in ihrer Wirkung vernachlässigbarer Parallelrauschstromquelle i_r eines Feldeffekttransistors als dreipoliges verstärkendes Element 2 mit einer außerhalb des Übertragungsbereichs eingangsseitig hochohmigen verlustarmen Filterschaltung 3.

b) Elektrisches Ersatzschaltbild einer aktiven Breitbandempfangsantenne nach dem Stand der Technik mit Rauschanpassungsnetzwerk und frequenzabhängiger effektiver Länge des passiven Antennenteils 1 am Anschlusspunkt des Transistors und ausgangsseitigem Anpassungsnetzwerk zur Glättung des Frequenzgangs.

Fig. 3:
Aktive Breitbandempfangsantenne gemäß Fig. 1 jedoch mit einem einstellbares Übertragungsglied 34 mit mehreren in Serie geschalteten Widerständen 35 mit jeweils einem dem Widerstand 35 parallel geschalteten und als Schaltdiode 36 ausgeführten einstellbaren elektronischen Element 34 zur Absenkung des Empfangspegels in Stufen.

Fig. 4:
Aktive Breitbandempfangsantenne wie in den Figuren 1 und 3, jedoch mit einem einstellbarem Übertragungsglied 34 aus einem Übertrager 38 mit in Stufen verfügbarem Übersetzungsverhältnis (t), Schaltdioden 36 als einstellbare elektronische Elemente 32 zur Einstellung eines großen Übersetzungsverhältnisses (t) und damit eines großen Verhältnisses der Eingangsspannung U_E zur Ausgangsspannung U_A bei großen Empfangspegeln .

Fig. 5:
Aktive Breitbandempfangsantenne wie in den Figuren 1, 3 und 4, jedoch mit einem einstellbarem einstellbaren Längselement 30 als ein frequenzabhängiger Zweipol 47 mit einer zur Eingangsadmittanz 7 der verlustarmen Filterschaltung 3 ähnlichen, jedoch im Wesentlichen mit einer um einen frequenzunabhängigen Faktor (t-1) kleineren Zweipoladmittanz 46 als die Eingangsadmittanz 7 der verlustarmen Filterschaltung 3 mit einer dem frequenzabhängigen Zweipol 47 parallel geschalteten Schaltdiode 36.

Fig. 6:
Aktive Breitbandempfangsantenne wie in Fig. 4 mit Verstärkereinheit 11 mit der Rauschzahl F_v als weiterführende Schaltung; Gestaltung des Realteils G der bei kleinen Empfangspegeln wirksamen Admittanz 7 als hinreichend groß, so dass der Rauschbeitrag der Verstärkereinheit 11 kleiner ist als der Rauschbeitrag des Feldeffekttransistors 2.

Fig. 7:
Aktive Breitbandempfangsantenne wie in Fig. 2a mit mehreren verlustarmen Filterschaltungen, welche über Schaltdioden 36 alternativ zwischen dem Eingang und dem Ausgang des Übertragungsnetzwerks 31 zur alternativen Absenkung der inneren Verstärkung der aktiven Antenne angesteuert werden.

Fig. 8:
Aktive Breitbandempfangsantenne wie in Fig. 6 jedoch mit einer Filterschaltung 3 mit fest eingestellten Blindelementen 20 und mit Blindelementen 20a, welche mit Hilfe einstellbarer elektronischer Elemente 32 zur Absenkung der inneren Verstärkung zu- und abgeschaltet werden.

Fig. 9:
Gestaltung des dreipoligen verstärkenden Elements 2 als erweitertes dreipoliges verstärkendes Element

a) aus einem Eingangs-Feldeffekttransistor 13 und einem Bipolartransistor 14 in Emitterfolgerschaltung

b) aus einem Eingangs-Bipolartransistor 49 und einem weiteren Bipolartransistor 50 in Emitterfolgerschaltung

c) aus einem Eingangstransistor und einem weiteren Transistor zur hochfrequenten Nachführung der Drain- bzw. der Kollektorelektrode des Eingangstransistors.

d) aus einer kombinierten Transistorschaltung zur elektronischen Steuerung der Ruhespannungsquelle U_D0 45 und des Ruhestroms I_S0 50 des Eingangstransistors im Zusammenhang mit der Absenkung der inneren Verstärkung der aktiven Antenne aufgrund zu hoher Empfangspegel.

Fig. 10:
Passiver Antennenteil 1 mit einer Anschlussstelle 18, deren beide Anschlüsse gegenüber dem Masseanschluss hochliegen, mit einem Feldeffekttransistor 2a und einem weiteren Feldeffekttransistor 2b und einem als Trenntransformator ausgeführten Übertrager 38 mit Schaltdioden 36 zur Einstellung des Übersetzungsverhältnisses

Fig. 11:
Gestaltung von mehreren Übertragungsfrequenzbändern über mehrere getrennte Übertragungswege für die betreffenden Frequenzbänder. Jedem der Übertragungswege ist jeweils ein einstellbares Übertragungsglied 34, 34' und ein Regelverstärker 33, 33' frequenzselektiv zugeordnet.

Fig. 12:
Anordnung wie in Fig. 11, jedoch mit im Empfänger 44 selektiv angesteuerten Regelverstärkern 33, 33' zur Ansteuerung der einstellbaren Übertragungsglieder 34, 34' in der aktiven Antenne.

Fig.13:
Gruppenantenne zur Gestaltung von Richtwirkungen mit einer passiven Antennenanordnung 27 mit elektrischer Strahlungskopplung zwischen den Anschlussstellen 18, welche jeweils mit einer Verstärkerschaltung 21 und einer Hochfrequenzleitung 10 beschaltet sind und deren Signale im Antennencombiner 22 zusammengefasst sind. Es ist ein gemeinsamer Regelverstärker 33 zur Überwachung des hochfrequenten Empfangssignals 8 am Antennenausgang vorhanden.

Fig. 14:
Scanningdiversity-Antennenanlage mit einer Anordnung wie in Fig. 13, jedoch mit elektronischen Umschaltern 25 an Stelle des Antennencombiners 22 und jeweils einem Ersatzlastwiderstand 26 zur Belastung der nicht durchgeschalteten Antennenzweige. Es ist ein gemeinsamer Regelverstärker 33 zur Überwachung des ausgewählten hochfrequenten Empfangssignals vorhanden.

Fig. 15:
Scanningdiversity-Antennenanlage gebildet aus auf die Fensterscheibe gedruckten Heizfeldern mit diversitätsmäßig geeignet positionierten Anschlussstellen 18 zur Erreichung diversitätsmäßig unabhängiger Empfangssignale 8. Es ist ein gemeinsamer Regelverstärker 33 in zur Überwachung des ausgewählten hochfrequenten Empfangssignals im elektronischen Umschalter 25 vorhanden.

Fig. 16:
Scanningdiversity-Antennenanlage wie in Fig. 15, jedoch mit gesondert ermittelten Blindleitwerten 23 zur Verbesserung der diversitätsmäßigen Unabhängigkeit der Empfangssignale der passiven Antennenteile 1. Jeder aktiven Antenne ist ein gesonderter Regelverstärker 33 zugeordnet.

Fig. 17:
Aktive Antenne nach der Erfindung, jedoch mit einem Übertrager 24 mit hinreichend hochohmiger Primärinduktivität und hinreichend großem Übersetzungsverhältnis zur breitbandigen Erhöhung der effektiven Länge l_e.

Fig. 18:

a) und b): Beispielhafte Antennenkonfigurationen möglicher passiver Antennenteile 1

c) Impedanzverläufe der Antennenstrukturen A1, A2 und A3 in der Impedanzebene im Frequenzbereich von 76 bis 108 MHz und schraffierte Bereiche für R_A< R_Amin und R_A > R_Amax

d) Realteile der Antennenimpedanzen nach c) mit zulässigem Wertebereich R_Amin < R_A < R_Amax

Fig. 19:

a) Verlauf der seriellen Blindwiderstände X₁ und X₃ sowie des parallelen Blindleitwerts B₂ der erfindungsgemäßen T-Filteranordnung in Fig. 6b über der Frequenz am Beispiel der breitbandigen Abdeckung der Rundfunkbereiche UKW-Hörrundfunk sowie VHF- und UHF-Fernsehrundfunk.

b) Elektrisches Ersatzschaltbild einer Antenne nach der Erfindung für die unter a) genannten Frequenzbereiche.

Exemplary embodiments of active broadband reception antennas and antenna systems according to the invention are shown in the drawings and are described in more detail below. In detail shows:

Fig. 1:
Active broadband reception antenna according to the invention with an amplifier circuit 21 connected directly to the passive antenna part 1 with a three-pole amplifying element 2, with input admittance 7 of the transmission network 31 located in the source line with an adjustable transmission element 34, for example in the form of a series resistance realized as an adjustable electronic element 32, a low-loss filter circuit 3 connected downstream and an effective resistor 5 and control amplifier 33 effective on the output side.

Fig. 2:

a) Electrical equivalent circuit diagram of an active broadband receiving antenna according to the invention with series noise voltage source u _r and the effect of negligible parallel noise current source i _{r of} a field effect transistor as a three-pole amplifying element 2 with a low-loss filter circuit 3 on the input side outside the transmission range.

b) Electrical equivalent circuit diagram of an active broadband reception antenna according to the prior art with noise adaptation network and frequency-dependent effective length of the passive antenna part 1 at the connection point of the transistor and output-side adaptation network for smoothing the frequency response.

Fig. 3:
Active broadband reception antenna according to FIG. 1, however, with an adjustable transmission element 34 with a plurality of resistors 35 connected in series, each with an adjustable electronic element 34 connected in parallel with the resistor 35 and designed as a switching diode 36 for lowering the reception level in stages.

Fig. 4:
Active broadband receiving antenna as in Figures 1 and 3, but with an adjustable transmission element 34 from a transformer 38 with a step-by-step ratio (t), switching diodes 36 as adjustable electronic elements 32 for setting a large ratio (t) and thus a large ratio of Input voltage U _E to output voltage U _A at high reception levels.

Fig. 5:
Active broadband reception antenna as in FIGS. 1, 3 and 4, but with an adjustable, adjustable longitudinal element 30 as a frequency-dependent two-pole 47 with a filter circuit 3 similar to the input admittance 7, but essentially with a frequency-independent factor (t-1) smaller Two-pole admittance 46 as the input admittance 7 of the low-loss filter circuit 3 with a switching diode 36 connected in parallel with the frequency-dependent two-pole 47.

Fig. 6:
Active broadband reception antenna as in FIG. 4 with amplifier unit 11 with the noise figure F _v as a further circuit; Design of the real part G of the admittance 7 effective at low reception levels as sufficiently large that the noise contribution of the amplifier unit 11 is smaller than the noise contribution of the field effect transistor 2.

Fig. 7:
Active broadband receiving antenna as in FIG. 2a with a plurality of low-loss filter circuits which are alternatively controlled via switching diodes 36 between the input and the output of the transmission network 31 in order to alternatively reduce the internal gain of the active antenna.

Fig. 8:
Active broadband reception antenna as in FIG. 6, however, with a filter circuit 3 with fixed blind elements 20 and with blind elements 20a, which are switched on and off with the aid of adjustable electronic elements 32 to lower the internal gain.

Fig. 9:
Design of the three-pole reinforcing element 2 as an expanded three-pole reinforcing element

a) from an input field effect transistor 13 and a bipolar transistor 14 in an emitter follower circuit

b) an input bipolar transistor 49 and a further bipolar transistor 50 in an emitter follower circuit

c) an input transistor and a further transistor for high-frequency tracking of the drain or collector electrode of the input transistor.

d) from a combined transistor circuit for the electronic control of the quiescent voltage source U _D0 45 and the quiescent current I _S0 50 of the input transistor in connection with the reduction in the internal gain of the active antenna due to excessive reception levels.

Fig. 10:
Passive antenna part 1 with a connection point 18, the two connections of which are high with respect to the ground connection, with a field effect transistor 2a and a further field effect transistor 2b and a transformer 38, designed as an isolating transformer, with switching diodes 36 for setting the transmission ratio

Fig. 11:
Design of several transmission frequency bands over several separate transmission paths for the relevant frequency bands. An adjustable transmission element 34, 34 'and a control amplifier 33, 33' are frequency-selectively assigned to each of the transmission paths.

Fig. 12:
Arrangement as in FIG. 11, but with control amplifiers 33, 33 'selectively controlled in the receiver 44 for controlling the adjustable transmission elements 34, 34' in the active antenna.

Figure 13:
Group antenna for designing directional effects with a passive antenna arrangement 27 with electrical radiation coupling between the connection points 18, each of which is connected to an amplifier circuit 21 and a high-frequency line 10 and whose signals are combined in the antenna combiner 22. There is a common control amplifier 33 for monitoring the high-frequency received signal 8 at the antenna output.

Fig. 14:
Scanning diversity antenna system with an arrangement as in FIG. 13, but with electronic switches 25 instead of the antenna combiner 22 and in each case an equivalent load resistor 26 for loading the antenna branches which are not switched through. There is a common control amplifier 33 for monitoring the selected high-frequency received signal.

Fig. 15:
Scanning diversity antenna system formed from heating fields printed on the window pane with connection points 18 suitably positioned in terms of diversity in order to achieve reception signals 8 that are independent of diversity. A common control amplifier 33 is provided in the electronic switch 25 for monitoring the selected high-frequency reception signal.

Fig. 16:
Scanning diversity antenna system as in FIG. 15, but with separately determined blind conductance values 23 to improve the diversity-independent of the received signals of the passive antenna parts 1. Each active antenna is assigned a separate control amplifier 33.

Fig. 17:
Active antenna according to the invention, but with a transformer 24 with a sufficiently high-impedance primary inductance and a sufficiently large transmission ratio for broadband increase in the effective length l _e .

Fig. 18:

a) and b): Exemplary antenna configurations of possible passive antenna parts 1

c) Impedance profiles of the antenna structures A1, A2 and A3 in the impedance plane in the frequency range from 76 to 108 MHz and hatched areas for R _A <R _Amin and R _A > R _Amax

d) Real parts of the antenna impedances according to c) with permissible value range R _Amin <R _A <R _Amax

Fig. 19:

a) Course of the serial reactances X ₁ and X ₃ and the parallel reactive conductance B _{2 of} the T-filter arrangement according to the invention in Fig. 6b over the frequency using the example of the broadband coverage of the radio areas FM radio broadcasting and VHF and UHF television broadcasting.

b) Electrical equivalent circuit diagram of an antenna according to the invention for the frequency ranges mentioned under a).

In Fig. 1 an antenna according to the basic form of the invention is shown. Using the example of the heating field of a motor vehicle printed on a window pane, it can be seen that the passive antenna part 1 cannot be designed in such a way that it has particular desired properties with regard to its use as an antenna in the meter and decimeter wave range and thus has a shape corresponding to its geometric structure and the metallic border of the window has a random frequency dependence of both the effective length l _e and its impedance. The essence of the present invention consists in realizing an active antenna, which allows this randomness of the frequency dependency of the given passive antenna part 1 to be compensated for with the aid of an active antenna which is not complex, easy to determine and easy to implement, and with regard to self-noise, linearity and Freely design frequency response and to achieve a predetermined frequency response between the incident wave with the electric field strength E and the high-frequency received signal 8. According to the invention, the reception voltage present at a connection point 18 is fed to the amplifier circuit 21, which contains at the input a three-pole amplifying element 2, preferably an element with the character of a field effect transistor 2, which is coupled in its source line to the input admittance 7 of a low-loss filter circuit 3, which is terminated at its output with an effective resistance 5. In the case of an antenna of this type, the input admittance 7 can be designed according to the invention, for example, in such a way that the strong frequency dependency, which the received open circuit voltage, expressed by the effective length l _{e of} the passive antenna part 1 designed in this way, is largely compensated for in the high-frequency received signal 8. In order to lower the reception level in the area of reception field strengths that are too high, an adjustable longitudinal element 30 is present in the adjustable transmission element 34, which acts as a through-connection in the area of low reception levels. If the longitudinal element 30 is set to be high-resistance in the region of a reception level that is too high, on the one hand it causes the lowering of the high-frequency reception signal 8 and an increase in the impedance, which has negative feedback in the source line of the transistor, or a reduction in the admittance 7 ′ present there. The field effect transistor 2 is thus linearized by the measure and the further circuit is protected against excessive reception levels.

The mode of operation and the design principle of an antenna according to the invention are explained using the electrical equivalent circuit diagrams of FIGS. 2a and 5:
The suitability of a given passive antenna part 1 for the design of a sufficiently noise-sensitive active antenna can be estimated on the basis of the antenna temperature prevailing in the transmission frequency range. Field effect transistors have i _r usually an extremely small parallel noise current source so that their contribution i _r * Z _A at negligibly small gate-source and gate-drain capacitances C ₂ and C ₁ and the antenna impedances occurring in practice Z _A in comparison to the series noise _{voltage source} u _{r of} the field effect transistor, expressed by its equivalent noise _resistance R _{äF, is} always negligibly small. The sensitivity requirement is thus reduced to the fact that the noise voltage source u _r ² = 4kT _o BR _äF in relation to the received noise voltage source u _rA ² = 4kT _A BR _A , which is given by the antenna temperature T _A and the real part R _{A of} the antenna impedance Z _A , is smaller or at most the same size. With noise contributions of the same size, the sufficient sensitivity criterion with negligibly small capacitances C ₁ , C ₂ is therefore simply the requirement that is easy to test R A > R AEF * T 0 / T A to fulfill. Modern gallium arsenide transistors have negligible capacitances C ₁ and C ₂ in comparison to the rest of the wiring and a negligible effect of i _r with regard to the intended application as the cause of the extremely low noise temperature T _N0 when such transistors are adapted to noise. The equivalent noise resistance depends on the quiescent current and can be applied over 30 MHz broadband with 30 ohms and less. For the example of an antenna for the FM frequency range and an prevailing antenna temperature of approx. 1000 K, with regard to the noise sensitivity for the real part of the complex antenna impedance, which represents the radiation resistance in the case of low-loss field effect transistor 2, only R _A ( f)> about 10 ohms to be required as a sufficient condition.

5 shows the noise contribution of an amplifier unit 11 at the end of the high-frequency line 10 connected to the low-loss filter circuit 3 on the output side. With sufficient amplification in the amplifier circuit 21, this contribution is kept correspondingly small. To protect the downstream amplifier unit 11 from non-linear effects, it is often necessary to make this amplification largely independent of frequency within the transmission frequency range. This is achieved by appropriate, preferably lossless, transformation of the effective resistance 5 at the output of the low-loss filter circuit 3 into a suitable frequency-dependent input admittance 7. If the frequency dependency required for the input admittance 7 due to the frequency dependence of the effective length l _e (f) is known, then a circuit of reactances for the low-loss filter circuit 3 can be found which largely corresponds to this requirement.

The criterion according to the invention for the exemplary design of a necessary and frequency-independent reception power within the transmission frequency range is explained for the terrestrial broadcast reception of an active vehicle antenna with regard to the reception power in the downstream reception arrangement with reference to FIG. 5. The largely frequency-independent reception behavior must be demanded in order not to significantly reduce the sensitivity of the overall system due to the noise contribution of the reception system downstream of the active antenna and on the other hand to avoid non-linear effects due to amplification increases as a result of the frequency-dependent reception behavior within a transmission frequency range. 5 is represented by the amplifier unit 11 with the noise figure F _v . Its noise contribution to the total noise is shown in FIG. 5 as an equivalent noise _resistance R _av at the input of the amplifier circuit 21, where: R AEV = ( F V -1) 4 · G ( f )

G (f) denotes the frequency-dependent real part of the input admittance 7 of the low-loss filter circuit 3. This noise contribution is insignificant then applies against the inevitable received sound of the rushing with T _A R _A when: G ( f ) ≻ ( F V -1)· T 0 4 · T A , 1 R A ( f )

In order to meet the sensitivity condition, in an advantageous embodiment of an active antenna according to the invention, the frequency dependence of the real part G (f) of the input admittance 7 of the low-loss filter circuit 3 is to be selected reciprocally to the frequency response of the real part R _A (f) of the complex antenna impedance. For the example of an FM radio receiver with F _V ∼ 4, approximately G (f) <1 / (3 * R _A (f)) would therefore have to be selected. To protect the receiver from reception levels that are too high, on the other hand, it is expedient not to select the power gain of the active antenna to be substantially greater than for optimum sensitivity of the overall system and thus to make G (f) approximately as large as indicated in the right part of equation (3).

The invention is associated with the great advantage that the frequency response for G (f) given from R _A (f) can be easily fulfilled because neither the source impedance of the low-loss filter circuit 3 which drives the input side, which is given with 1 / g _{m of} the field effect transistor 2 is, the effective resistance 5 at the output of the low-loss filter circuit 3 still have unavoidable essential reactive components. This results in the advantageously free design of the frequency behavior of the active antenna according to the present invention. In contrast to this, in the case of an active antenna according to the prior art in FIG. 2b, the frequency-dependent radiator impedance Z _s (f) is compulsorily and inseparably present as the source impedance of the primary-side transformation network. Their frequency behavior limits the achievable bandwidth of the impedance transformed into the vicinity of Z _opt and thus the bandwidth of the signal-to-noise ratio at the output of the active circuit.

bzw. für die Referenzantenne bei der Bezugsfrequenz:

The exemplary design of the frequency response of G (f) of an active vehicle antenna according to the invention is described below if there is a requirement that the received power P _a at the input of the receiving system connected downstream of the active antenna is greater by a factor V than with a passive reference antenna , for example a passive rod antenna on the vehicle with its resonance length. Due to the necessarily different directional diagrams, this factor is based on the azimuthal mean values at a defined constant elevation angle  of the wave incidence. Comparative azimuthal directional factor measurements with the aid of an antenna measuring section with vehicle rotation at the passive antenna part 1 and on the comparison antenna result in N angular steps for a full revolution and with the directional factor D _a ( _n , ) of the specified passive antenna part 1 and corresponding to the directional factor D _P ( _n , ) of the passive reference antenna for the nth angular step the following azimuthal mean values for the guide factors:

or for the reference antenna at the reference frequency:

The receiving system downstream of the active antenna, which is represented in FIG. 5 by the amplifier unit 11, is generally related to the line impedance Z _{L of} the high-frequency line system. The mean azimuthal received power in the load resistor 9 is obtained with a sufficiently high slope g _{m of} the input characteristic of the field effect transistor 2: P at the = 1 2 · e 2 · l em 2 ( f ) · G ( f ) where l _em ² (f) is the azimuthal mean value of the quadratic effective length of the passive antenna part 1 that occurs at each frequency, taking into account the difference between D _am (f) and Equation (2) resulting effective area of the passive antenna part 1 as follows:

The mean azimuthal reception power of the passive reference antenna with D _pm from equation (5) is: P pm = λ 2 8 × π , e 2 Z 0 , D pm

Taking into account the gain requirement P _am / P _pm = V, the frequency curve for G (f) to be required according to the invention results in: G ( f ) = 1 R A ( f ) , D pm D at the ( f ) · V

In the case of a lossy passive antenna part 1 with the efficiency η, the directional factor D _am (f) is to be replaced by D _am (f) * η in equation (8). This does not change the other dimensioning rules.

In the case of approximately the same azimuthal mean values D _pm and D _am (f), the frequency dependence of G (f) must be proportional to 1 / R _a (f). V is chosen so large that D pm D at the ( f ) · V >> ( F V -1)· T 0 4 · T A applies, then the noise contribution of the receiving system downstream of the active antenna to the total noise is negligibly small. If the condition specified in equation (1) is additionally met, then the sensitivity is dependent solely on the directivity of the passive antenna part 1 and on the prevailing interference. The minimum necessary mean azimuthal radiation density S _am for a signal-interference ratio = 1 is then: S at the ( f ) = k * T A · B D at the ( f ) · 4 × π λ 2 and increases with 1 / η if D _am (f) is to be replaced by D _am (f) * η.

Taking into account the interference radiation emanating from the vehicle itself, the selection of a passive antenna part 1 suitable for an antenna according to the invention as the structure on the vehicle in connection with the condition for R _A (f) specified in equation (1) and discussed in more detail below can therefore be unerringly thereby take place that the ratio T _A / D _on (f) is found to be sufficiently large for the transmission frequency range.

18a and 18b exemplify antenna configurations of possible passive antenna parts 1 of active antennas according to the invention. At the connection points 18, the impedance profiles Z _A (f) shown in the complex impedance plane in FIG. 18c are present as a function of the frequency. The area marked by hatching in the left margin of the diagram is one-sided by the value R _Amin = const. bounded. Impedance profiles that run outside the area identified in this way thus meet the condition of negligible noise of the field effect transistor 2 specified in accordance with equation (1) in the presence of a specific interference radiation according to T _A. The diagram shows convincingly the advantage of an active antenna according to the invention over an active antenna according to FIG. 2b according to the prior art, which lies in the fact that, without an input-side adaptation means, all antenna structures meet this condition without an input-side transformation means. 18c, the real parts of the passive antenna parts 1 shown in FIGS. 18a and b are plotted against the frequency of 76 to 108 MHz. The frequency curve of the real part of the input admittance 7 to be designed according to the invention at the input of the low-loss filter circuit 3 is therefore inverted in each case to the curve curves shown in FIG. 18d according to aspects discussed in connection with equations (3) and (8).

In the amplifier circuit 21 according to the invention there is naturally an upper limit for the size of the tolerable voltage effective at the input, which results in the reception field over the effective length l _e due to possible nonlinear effects such as intermodulation. The maximum tolerable voltage can be increased by selecting a suitable field effect transistor 2 and by selecting a suitable operating point and by other circuit measures known per se. According to the invention, equation (6) can be assigned a maximum tolerable azimuthal mean value l _em with a known azimuthal directional factor D _am (f), a maximum tolerable active component R _Amax . The range of values with R _A > R _{Amax which} is not permissible for dimensioning is also hatched in FIGS. 18c and 18d. The radiation resistances R _{A of} the impedance values of particularly favorable structures for use as a passive antenna part 1 are therefore outside the hatched value range with R _amin <R _A <R _Amax .

In a further advantageous embodiment of the invention, a predetermined antenna structure is supplemented by using a low-loss transformer with the transmission ratio ü, as indicated in FIG. 17, which forms the passive antenna part 1 together with the antenna structure, for example a heating field on the window pane. The broadband transmission ratio is advantageously chosen such that the impedance that can be measured at the output of the transmitter is placed with its real part in the value range with R _Amin <R _A <R _Amax . It is advantageous to make the primary inductance sufficiently high-resistance.

The linearity requirement is determined by a sufficiently large negative feedback, through which in the Source line located input admittance 7 fulfilled. This requires one in the transmission area comparatively low negative feedback, which according to the gain requirement e.g. is dimensioned according to equation (8), but so outside the transmission range is as large as possible. In an advantageous embodiment of the invention are used for implementation such low-loss filter circuits 3 preferably T-half filter or T-filter or chain circuits such filters used. Such filters are shown in their basic structure in the figures. The individual elements can be used to correspond to a more complicated frequency response of G (f) can be supplemented by additional blind elements. In the interest of high impedance on the input side and the blocking effect in the blocking area, it is expedient to use a series or parallel branch each form a combination of reactances in such a way that both the absolute value of a reactance in the series branch 28 as well as the absolute value of a reactance in the parallel branch 29 each sufficiently small and within a transmission frequency range outside of such is sufficiently large (Fig. 19b).

In a further advantageous application of the invention, it is proposed to store corresponding basic structures for low-loss filter circuits 3 with initially unknown values for the dummy elements in a modern digital computer for different characteristic courses of G (f) and to measure both the impedance Z _{A of} the passive antenna part 1 and the measurement technology determine the azimuthal average value D _{am of} the guide factor by measurement or calculation and also store it in the digital computer. The frequency curve of G (f) thus determined using equation (8) enables the subsequent concrete determination of the blind elements of the low-loss filter circuit 3 for a suitably selected basic filter structure with the aid of known strategies of variation calculation for the given gain V of the active antenna.

In particular in the case of antenna systems in which a plurality of antennas are formed, such as antenna diversity systems, group antenna systems or multi-range antenna systems, it is helpful in an advantageous development of the invention, as indicated in FIG. 6, to design the amplifier unit 11 as the active output stage of the amplifier circuit 21. This can be provided with an output resistance equal to the characteristic impedance Z _{L of} conventional coaxial lines. The effective resistance 5 is formed by the input impedance of the amplifier unit 11. G (f) is to be designed analogously according to the above statements with the aid of a low-loss filter circuit 3 terminated with this impedance.

Because of the ineffectiveness of the adjustable transmission element 34 in the case of low reception levels this sensitivity analysis is not affected. The voltage drop after the first reinforcing element of the active antenna, it is particularly advantageous, because they have an optimal effect with regard to the frequency dependence of the expected Allows intermodulation disorder. The influence on the sensitivity of the entire receiving system is thus only increased by the influence of the voltage drop Noise figure of the subsequent circuit determined.

Below are different forms of lowering the internal gain of the active Faced antenna. In Figures 1, 2a and 3, the voltage drop takes place via a longitudinal element 30, which is designed independent of frequency. As a result, reception signals become at frequencies at which low-impedance real parts of the antenna impedances are present and accordingly large values of the input admittance G (f) are designed according to the invention, attenuated more than received signals at frequencies with a high-impedance real part of the antenna impedances. When using a frequency-independent longitudinal element 30 must for the reduction at high reception levels therefore a medium resistance value should be selected, which for intermodulating received signals at frequencies with a large real part of the Antenna impedances too small and at frequencies with a small real part of the antenna impedances is too big. This involves the risk of intermodulating receive signals at frequencies with a large real part of the antenna impedances due to the smaller negative feedback effect there cause excessive intermodulation disturbances and, on the other hand, the remaining Gain at frequencies with a small real part of the antenna impedances is too small and the arrangement is too insensitive at these frequencies.

In an advantageous embodiment of the invention, such forms are therefore adjustable Proposed transmission elements 34, which are set at low reception levels Reduce admittances 7 by a suitable factor regardless of frequency. With those available today Amplifier components are e.g. for the FM area and an application in the motor vehicle a level reduction between 20 * log (t) = 10 dB and 20 * log (t) = 20dB is practicable. This makes the internal gain of the active antenna frequency-independent by a desired one Reduced factor and the above-mentioned frequency-dependent intermodulation effect does not occur. According to the invention, this is achieved, for example, by a transformer arrangement as in Fig. 4 and in Fig. 6 reached. The frequency-independent gear ratio of the Transformer with the help of divided windings and the switching diodes 36 shown as adjustable electronic elements 32 designed adjustable in stages. With the right choice of gear ratios the suitable values for the conductance G (f) in the admittance 7 or 7 'can be selected for the range of small or large reception levels. To increase the Linearity and the current modulation range of the three-pole reinforcing element 2 is in FIG. 6 provided the quiescent current in this element along with the lowering of the internal gain the active antenna.

Another method for achieving frequency-independent negative feedback is given by the arrangement in FIG. 5. Here, the adjustable longitudinal element 30 is designed as a frequency-dependent two-pole 47 for frequency-independent lowering of the high-frequency received signals 8. This is achieved with a two-pole admittance 46 similar to the input admittance 7 of the low-loss filter circuit 3, but essentially with a frequency-independent factor t-1 smaller than the input admittance 7 of the transmission network 31 at low reception levels. By connecting a switching diode 36 in parallel to the frequency-dependent two-pole 47, by setting the two-pole admittance 46 in the blocked state and bridging the two-pole admittance 46 when it is in the on state, the high-frequency received signals 8 are lowered by a substantially frequency-independent factor t when the switching diode 36 is blocked = U _E / U _A.

In a further advantageous embodiment of the invention, the transmission network 31 is included 8 as a low-loss filter circuit 3 with fixed blind elements 20 designed. Switchable blind elements 20a are used here, which with the help adjustable electronic elements 32 are switched on and off in such a way that when they fall below a desired reception level the desired frequency dependence of the larger Active conductance G (f) of the input admittance 7 effective at the source connection 24 for higher ones internal gain of the active antenna is given on the one hand. On the other hand, if exceeded a desired reception level, the desired frequency dependency accordingly the reduced conductance G '(f) with the same frequency dependence of the am Source connection 24 effective input admittance 7 'for reduced internal amplification of the active antenna.

In the transmission network 31 in the advantageous arrangement in FIG. 7 there are several low-loss Filter circuits 3, 3a are present, which alternatively between the input via switching diodes 36 and the output of the transmission network 31 are connected. Your entrance admittances 7, 7b for small reception levels and 7 ', 7b' for large reception levels are fixed Blind elements 20 are each formed such that the switching diodes 36 drop below them a desired reception level, the desired frequency dependence of the conductance G (f) the input admittance 7 effective at the source connection 24 for higher internal ones Gain of the active antenna and when a given reception level is exceeded the desired frequency dependence of the active conductance G '(f) of the effective ones at the source connection 24 Input admittance 7 'for reduced internal gain of the active antenna is given.

In the embodiment of an active antenna according to the invention shown in FIG the passive antenna part 1 is configured with a connection point 18, the two connections of which lie high against the mass. Each of the two connections has a control connection 15a and 15b of a three-pole reinforcing element 2 connected. The source terminals 24a and 24b are connected to the primary side of a transformer 38 designed as an isolating transformer, whose secondary side has different outputs to design different gear ratios t owns. The adjustable transmission element 34 thus becomes the transmitter and the switching diodes 36 are formed. The drain terminals 53a and 53b of the three-pole reinforcing Elements 2a and 2b are connected to ground 0.

In a further advantageous embodiment of the invention, the three-pole reinforcing element 2, as in Fig. 9a, designed as an expanded three-pole reinforcing element. To increase The effective steepness of the transmission characteristic is the extended element from an input field effect transistor 13, from the source of which the bipolar transistor 14 in emitter follower circuit is controlled and through the emitter terminal 12, the source electrode of the extended three-pole reinforcing element 2 is formed, combined.

In a further advantageous embodiment, the three-pole reinforcing element is 2 in Fig. 9b as an expanded three-pole amplifying element from an input bipolar transistor 49 and a further bipolar transistor 50 combined in an emitter follower circuit. The emitter connection 12 of the bipolar transistor 50 forms the source terminal 24 of the three-pole amplifying Elements 2. With a sufficiently low quiescent current in the input bipolar transistor 49 the required high impedance with small input capacitance and sufficiently small Parallel noise current reached. A significantly higher quiescent current in the further bipolar transistor 50 causes the transmission characteristic curve to be sufficiently steep for the whole Element.

9c, the three-pole reinforcing element 2 is an expanded three-pole reinforcing element Element made from an input bipolar transistor 49 or input field-effect transistor 13, whose collector connection or drain connection with the source or. Emitter connection of a additional transistor 51 is connected and its base or gate connection to the Emitter or source connection of the input bipolar transistor 49 or input field effect transistor 13 is connected. Through this connection, the source connection 24 of the three-pole reinforcing element 2 formed. An expanded three-pin reinforcing element of this Shape is prevented by voltage tracking at the drain or collector connection of the input transistor the disruptive influence of a voltage-dependent capacitance between the control electrode and the drain or collector electrode.

In FIG. 9d, the three-pole reinforcing element 2 is designed as an expanded three-pole reinforcing element, in which an electronically controllable quiescent current source I _S0 or / and an electronically controllable quiescent voltage source U _{D0 is} present. As a result, the quiescent current I _S0 and / or the quiescent voltage U _D0 in the input bipolar transistor 49 or input field-effect transistor 13 are increased when large reception levels occur in connection with the reduction in the internal gain of the active antenna according to the invention due to the reception level being too high.

11 are a plurality of bipolar transistors for designing a plurality of transmission frequency bands 14, 14 'for the expansion of the three-pole reinforcing element 2 and for the combined Formation of several three-pole reinforcing elements 2,2 'present. The base electrodes are to the source electrode of a common input transistor 13 or to the source connection an extended three-pole reinforcing element according to Figures 9a to 9d connected. The bipolar transistors 14, 14 'are each in the emitter follower circuit with the Input of a low-loss filter circuit 3, 3 'to form separate transmission paths for the relevant frequency bands connected. There are in each of the transmission paths an adjustable transmission element 34, 34 'and a control amplifier 33, 33', each of which only the frequency band assigned to the relevant transmission path via filter measures is supplied from the high-frequency received signal 8. The control signal 42, 42 'is in each case the assigned adjustable transmission element 34, 34 '. In contrast to this 12, the control signals 42, 42 'by selection means and control amplifiers 33, 33' in Receiver 44 derived from the output signal of the active antenna and the active antenna supplied via control lines 41.

In a particularly advantageous embodiment of the invention, the present active antenna is used several times in an antenna system, the passive antenna parts 1 of which have frequency-dependent and with respect to incident waves according to the amount and or only in phase, different directional diagrams of the effective lengths l _e , which, however, are electromagnetic Radiation coupling to each other and together form a passive antenna arrangement 27 with a plurality of connection points 18a, b, c. According to the invention, each is connected to an amplifier circuit 21 according to the invention and supplemented to form an active antenna according to the invention. Due to the high impedance of the amplifier inputs, there is no noticeable mutual influence of the received voltages due to the decoupling of the high-frequency received signals 8 at the passive antenna parts 1. Such an antenna arrangement is shown in general in FIG. 13. The received signals 8 present at the output of the amplifier circuit 21 are superimposed weighted in terms of magnitude and phase in an antenna combiner 22 provided for this purpose in order to design a group antenna arrangement with predetermined reception properties with regard to directivity and antenna gain without having an effect on the high-frequency received signals applied to the passive antenna parts 1. There, a common control amplifier 33, whose control signals 42a, b, c are fed to the transmission networks 31a, b, c in the active antennas for lowering the summed high-frequency received signal 8, can advantageously carry out level monitoring. In a further advantageous embodiment of a group antenna arrangement of this type, the level monitoring and attenuation takes place separately in each active antenna with the aid of a control amplifier 33 which is accommodated there in each case.

When using an antenna according to the invention as an active window antenna it is advantageously possible for the amplifier circuit 21 in the very narrow edge area the vehicle window invisible. Therefore it is desirable to use the one at the junction 18 parts to be miniaturized and only functional there install necessary parts of the amplifier circuit 21. The other parts of the low loss Filter circuit 3 are placed separately and switched on via the high-frequency line 10.

In a further advantageous embodiment of the invention, the active antenna is designed as a multi-range antenna for several frequency ranges. For this purpose, the basic frequency characteristics of reactive resistors X ₁ , X ₃ and the reactive conductance B _{2 of} a T-filter arrangement of the low-loss filter circuit 3 shown in FIG. 19 b are given as examples for the frequency ranges VHF radio broadcasting and VHF and UHF television broadcasting , The T-filter configuration ensures the high-impedance of the low-loss filter circuit 3 on the input side in order to achieve a sufficiently large negative feedback of the field effect transistor 2 in the blocking regions. The low-loss filter circuit 3 is designed as a T-half filter or T-filter or as a chain connection of such filters, the series or parallel branch of which is formed in each case from a combination of reactances in such a way that both the absolute value of a reactance in the series branch 28 and also the absolute value of a reactive conductance in the parallel branch 29 is sufficiently small within a transmission frequency range and sufficiently large outside such and the high-frequency received signal 8 is fed to the control amplifier 33 at the output and the adjustable transmission element 34 is controlled by the control signal 42 thereof.

To compensate for effects of the non-linearity of even order and the resulting Interband frequency conversions in the amplifier circuit 21 is in another advantageous embodiment of the invention in addition to the field effect transistor 2, a further field effect transistor 2 used with the same electrical properties. Here, the input connections the amplifier circuit 21 through the two control connections of the field effect transistors 15a and 15b formed and the input of the low-loss filter circuit 3 with the Source connections 19a and 19b connected. A balun in the low loss filter circuit 3 is used to resymmetrize the high-frequency received signals 8. Such. Circuit can also advantageously be connected to a connection point 18 with two against ground voltage leading connections can be connected.

The efficiency of antenna diversity systems is shaped by the number of available, mutually independent antenna signals. This independence is expressed in the correlation factor between the received voltages occurring in a Rayleigh wave field while driving. In a particularly advantageous development of the invention, a plurality of active reception antennas according to the invention are used in an antenna diversity system for vehicles, the passive antenna parts 1 being selected such that their reception signals E * l _e present in idle mode at the connection points 18 in a Rayleigh reception field are as independent as possible. Systems of this type, in which the connection points 18 are selected from this point of view and taking into account vehicle-technical aspects, are shown by way of example in FIGS. 15 and 16. Because of the electromagnetic radiation coupling existing between the connection points 18, this independence then only applies to the connection points 18 operated in idle mode. By connecting the connection points 18 with the amplifier circuits 21 according to the invention, due to their negligibly small capacitive input conductance, the high-frequency received signals 8 are tapped without feedback at the antenna outputs. The diversity-independent independence of the received signals at the connection points 18 is thus advantageously not influenced by this measure, and this independence consequently exists in the same way for the received signals 8 at the antenna outputs. Thus, independent reception signals 8 are available at the antenna outputs for selection in a scanning diversity system or for further processing in one of the other known diversity methods.

In contrast, the connection of the connection point 18 with a transformation circuit according to the prior art according to Fig. 2b on the flowing at the junction 18 Currents cause a dependence of the antenna signals on the antenna output. This The following is the relationship for a passive antenna part 1 with two connection points 18 explained in more detail:

Are U01 and U02 the open circuit voltage amplitudes at the connection points 18 of a passive antenna arrangement 27 in FIG. 14 in the reception field and Z11, Z22 the antenna impedances measured there and Z12 is also the interaction impedance due to the coupling of the connection point 18 and are Y1 and Y2 the input admittances of the amplifiers, with which the connection point 18 is loaded, the following relationship results for the voltage amplitudes occurring under this load at the connection points 18:

The correlation factor between the voltage amplitudes U1 and U2 and thus also between the antenna output voltages results from the mean values of the voltages U1 and U2 over time: ρ = U 1· U 2 U 1 2 · U 2 2

For the case assumed here, no-load received voltage amplitudes U10 and U20 result from one another when traveling in the Rayleigh reception field. This is expressed by a vanishing correlation factor, ie: ρ = U 10 · U 20 U 10 2 · U 20 2 = 0

If the input admittances of the amplifiers with which the connection points 18 are loaded are negligibly small according to the invention, ie Y1 = 0 and Y2 = 0, then the voltages U1 and U2 result from equation (11) as follows:

The interactions with the number 0 in the unit matrix in equation (13) show that the vanishing decorrelation in voltages U1 and U2 described in equation (13) is retained in an amplifier circuit 21 according to the invention. The evaluation of equation (11), on the other hand, shows a link between the two open circuit voltages via the interaction parameters Z12 * Y2 and Z12 * Y1 with the respective voltages under load, because the following then applies:

It is obvious that if the connection points 18, i.e. not disappearing Z12, the correlation factor only disappears if Y1 = Y2 = 0 is.

On the other hand, the previous considerations show that if the open-circuit voltages U10 and U20 are mutually dependent, special values for Y1 and Y2 can be found which, via the transformation described in equation 15, reduce or make the mutual dependency in the amplifier input voltages U1 and U2 disappear. In an advantageous development of the invention, it is therefore provided, as indicated in FIG. 16, to connect the passive antenna arrangement 27 at its connection points 18 by means of suitable conductance values - preferably blind conductance values 23 for reasons of sensitivity to noise - such that the correlation between the voltages at the connection points 18 becomes smaller in the interest of greater diversity efficiency. Active antennas according to the invention have the decisive advantage that the definition of such suitable dummy elements can be made largely independently of sensitivity considerations. For the radiation resistances R _A (f) that arise at the various connection points 18 do not require any precise adjustment, but only require that they belong to the permissible value range described in FIG. 18. To reduce reception levels that are too high, as in FIG. 15, the level of the selected signal can be fed to a common control amplifier 33 in the electronic changeover switch 25, in which a control signal 42 is formed and to the transmission networks 31 in the amplifier circuits 21 of the active reception antennas for lowering the selected high-frequency reception signal 8 is supplied. In a further embodiment, as in FIG. 16, the amplifier circuits 21 of the active antennas can each be assigned a separate control amplifier 33 for monitoring the high-frequency received signal 8 at the relevant antenna output.

List of names Active broadband reception antenna with reception level control

Mass 0

Passive antenna part 1

three-pole reinforcing element 2

Low loss filter circuit 3

Exit 4

Effective impedance 5 of the advanced circuit

Entrance 6

Entry admittance 7

High-frequency received signal 8

Load resistance 9

Radio frequency line 10

Amplifier unit 11

Emitter connection 12

Input field effect transistor 13

Bipolar transistor 14

Control connection 15

Junction 18

fixed blind element 20

switchable blind element 20a

Amplifier circuit 21

Antenna combiner 22

Reactive conductance 23

Source connection 24

Electronic switch 25

passive antenna arrangement 27

Series branch 28

Parallel branch 29

adjustable longitudinal element 30

Transmission network 31

adjustable electronic element 32

Control amplifier 33

Adjustable transmission link 34

Resistor 35

Switching diode 36

Adjustable resistance 37

Transformer 38

Controllable DC power source 40

Control line 41

Control signal 42

Receiver 44

Controllable DC voltage source 45

Bipolar 46

frequency-dependent two-pole 47

Two-pole filter circuit 48

Input bipolar transistor 49

Another bipolar transistor (50th

additional transistor 51

Drain connection 53

Input impedance Z

Noise figure F _v

Active conductance G

effective length le

Wavelength λ

Boltzmann constant k

Wave resistance of free space Z ₀

Measuring bandwidth B

Gear ratio t

Input voltage U _E

Output voltage U _A

Gate-source capacitance C2

Gate-drain capacitance C1

Noise temperature TNO

Ambient temperature T0

Claims (39)

Active broadband reception antenna, in which the internal gain of the active antenna is reduced when a predetermined reception level is exceeded, consisting of a passive antenna part (1), the output connections of which are connected to the input connections of an amplifier circuit (21),
characterized in that
the input circuit of the amplifier circuit (21) contains a three-pole amplifying element (2), the high-impedance control connection (15) of which is connected to the first connection (18) of the passive antenna part (1) at a high frequency, the high-frequency connection between the source connection (24 ) of the three-pole amplifying element (2) and the second connection (1 ') of the passive antenna part (1), the input admittance (7) of a low-loss transmission network (31) with filter character designed in the case of small high-frequency received signals (8) is negative feedback and linearizing and the transmission network (31) is loaded with the further circuit at its output (4) and at least one adjustable electronic element (32) for the adjustable lowering of the reception level in the transmission network (31) is present in such a way that the linearizing input admittance (7 ') of the Transmission network (31) is smaller if e lowering of the high-frequency received signal (8) is set (Fig. 1). Active broadband receiving antenna according to claim 1
characterized in that
the transmission network (31) with a filter character when the electronic element (32) or the electronic elements (32) is set for small high-frequency reception levels is formed as a low-loss filter circuit, which with the effective impedance (5) at its output (4) of the further Circuit is loaded and the blind elements of the low-loss transmission network (31) are selected such that the frequency dependence of the active conductance G (f) of the input admittance (7) effective at the input of the transmission network (31) is set such that with a given internal gain of the active antenna the frequency response in the high-frequency received signal (8), which is caused by the frequency-dependent effective length l _{e of} the passive antenna part (1), is designed within a broad frequency band according to freely chosen criteria. Active broadband receiving antenna according to one of Claims 1 to 2,
characterized in that
the transmission network (31) with filter character consists of a derailleur circuit consisting of an adjustable transmission link (34) and a low-loss filter circuit (3) with fixed blind elements, which is loaded with the impedance (5) of the further circuit effective at its output (4) and the adjustable transmission element (34) is designed to fall below a predetermined reception level for frequency-independent and low-loss signal transmission and the blind elements of the low-loss filter circuit (3) are selected such that the frequency dependence of the active conductance G (f) of the input admittance (7) effective at the source connection (24) ) is set in such a way that with a given internal gain of the active antenna, the frequency response in the high-frequency received signal (8) caused by the frequency-dependent effective length l _{e of} the passive antenna part (1) is designed within a broad frequency band according to freely chosen criteria tet (Fig. 1). Active broadband receiving antenna according to one of Claims 1 to 3
characterized in that
the transmission network (31) with filter character is formed as a low-loss filter circuit with fixed blind elements (20) and at least one switchable blind element (20a) is present, which is switched on and off with the aid of an adjustable electronic element (32) such that when the value falls below a desired reception level, the desired frequency dependency of the conductance G (f) of the input admittance (7) effective at the source connection (24) for higher internal amplification of the active antenna and, if a predetermined reception level is exceeded, the desired frequency dependence of the conductance G '(f) of the source connection ( 24) effective input admittance (7 ') for reduced internal gain of the active antenna is given (Fig. 8). Active broadband receiving antenna according to one of Claims 1 to 4,
characterized in that
the transmission network (31), which is filter-like, has a sufficiently small reactive component B (f) in the input conductance (7) in the input conductance (7) in the case of falling below a predetermined reception level and given transmission behavior to avoid non-linear effects (FIG. 1). Active broadband receiving antenna according to one of Claims 1 to 5,
characterized in that
for all settings of the at least one adjustable electronic element (32), the amount of the effective negative feedback admittance (7,7 ') outside the useful frequency band in the blocking frequency range of the transmission network (31) connected to the source connection (24) with filter character to avoid non-linear effects in all settings of the adjustable electronic element (32) or the adjustable electronic elements (32) is sufficiently small. Active broadband receiving antenna according to one of Claims 1 to 6,
characterized in that
the transmission network (31) is formed from the chain circuit of an adjustable transmission element (34) designed as a transmission block and a low-loss filter circuit (3) and the ratio (t: 1) of the input voltage (U _E ) to the output voltage (U _A ) of the adjustable transmission element ( 34) is set sufficiently large with the aid of an adjustable longitudinal element (30) contained therein when a predetermined reception level is exceeded (FIGS. 1, 2a, 3, 4, 5, 6, 10, 11, 12). Active broadband receiving antenna according to claim 7
characterized in that
the adjustable longitudinal element (30) is implemented by an electronically adjustable resistor (37), such as a diode with the character of a PIN diode (FIG. 1). Active broadband receiving antenna according to claim 5
characterized in that
the adjustable longitudinal element (30) is formed by a resistor (35) or by a plurality of resistors (35) connected in series, each with an adjustable electronic element (32) connected in parallel with the resistor (35) and designed as a switching diode (36) whose setting in the blocking state the associated resistor is fully effective and when it is set in the on state of the switching diode (36) the resistance is bridged, so that when the switching diode (36) or the switching diodes (36) are actuated accordingly, the reception level is reduced in stages is (Fig. 2a, 3). Active broadband receiving antenna according to claim 7
characterized in that
For frequency-independent lowering of the high-frequency reception signals (8), the adjustable longitudinal element (30) is designed as a frequency-dependent two-pole (47) with a filter similar to the input admittance of the low-loss filter circuit (3), but essentially with a frequency-independent factor (t-1) Smaller two-pole admittance (46) than the input admittance of the low-loss filter circuit (3) with a switching diode (36) connected in parallel with the frequency-dependent two-pole (47), the two-pole admittance (46) being effective in the blocking state and the two-pole admittance ( 46) is bridged, so that when the switching diode (36) is blocked, the high-frequency received signals (8) are reduced by an essentially frequency-independent factor (t) (FIG. 5). Active broadband receiving antenna according to claim 10
characterized in that
the frequency-dependent two-pole (47) is formed by the input admittance of a two-pole filter circuit (48), which is designed at least in the essential dummy elements according to the structure of the low-loss filter circuit (3) and whose dummy elements are chosen to be higher impedance by the frequency-independent factor (t-1) than the corresponding dummy elements of the low-loss filter circuit (3) and the two-pole filter circuit (48) are terminated with an impedance chosen by the same factor of higher impedance than the effective impedance (5) of the further circuit (FIG. 8). Active broadband receiving antenna according to one of Claims 1 to 6,
characterized in that
in the adjustable transmission element (34) there is a transformer (38) with a step-up transmission ratio (t) and as adjustable electronic elements (32) there are switching diodes (36) which are controlled in such a way that the transmission ratio (t) at high reception levels and thus the ratio of the input voltage U _E to the output voltage U _{A of} the adjustable transmission element (34) is set correspondingly large (FIGS. 4, 6). Active broadband receiving antenna according to one of Claims 1, 2, 4 to 6,
characterized in that
In the transmission network (31) with filter character, there are several low-loss filter circuits (3) which are alternatively connected via switching diodes (36) between the input and the output of the transmission network (31) and whose input admittance (7, 7 ') with fixed blind elements ( 20) is formed in such a way that, with the aid of the switching diodes (36), the desired frequency dependence of the active conductance G (f) of the input admittance (7) effective at the source connection (24) for higher internal gain of the active antenna and if it is exceeded is exceeded when the reception level falls below a predetermined level a predetermined reception level, the desired frequency dependency of the active conductance G '(f) of the input admittance (7') effective at the source connection (24) for reduced internal amplification of the active antenna is given (FIG. 7). Active broadband receiving antenna according to one of claims 1 to 13
characterized in that
the three-pole amplifying element (2) is designed as a field effect transistor, the high-resistance control connection (15) of which is formed by the gate, the source connection (24) of which is the source and the drain connection (53) of which is formed by the drain connection. Active broadband receiving antenna for use above 30 MHz according to claim 14
characterized in that
the field-effect transistor (2) has a negligible parallel noise _current source i _r , a very small gate-drain capacitance C ₁ and a very small gate-source capacitance C ₂ and negligible 1 / f noise and its minimum noise temperature T _N0 in the case of noise adaptation is significantly lower than the ambient temperature T ₀ (FIG. 2a). Active broadband receiving antenna according to one of Claims 1 to 13,
characterized in that
the three-pole amplifying element (2) is designed as an extended three-pole amplifying element, consisting of an input field-effect transistor (13), from the source of which the bipolar transistor (14) is driven in an emitter-follower circuit and through whose emitter connection (12) the source electrode of the extended field-effect transistor ( 2) is formed (Fig. 9a). Active broadband receiving antenna according to one of claims 1 to 13
characterized in that
the three-pole amplifying element (2) is designed as an expanded three-pole reinforcing element, consisting of an input bipolar transistor (49), from whose emitter a further bipolar transistor (50) is driven in an emitter follower circuit and through whose emitter connection (12) the source connection (24) of the three-pole amplifying element (2) is formed and the quiescent current in the input bipolar transistor (49) is set lower than in the further bipolar transistor (50) (FIG. 9b). Active broadband receiving antenna according to one of Claims 1 to 13,
characterized in that
the three-pole reinforcing element (2) is designed as an extended three-pole reinforcing element, consisting of an input bipolar transistor (49) or input field-effect transistor (13), the collector or drain connection of which is connected to the source or emitter connection of an additional transistor (51 ) is connected and its base or gate connection is connected to the emitter or source connection of the input bipolar transistor (49) or input field-effect transistor (13) and through this connection the source connection (24) of the three-pole amplifying Elements (2) is formed (Fig. 9c). Active broadband receiving antenna according to one of Claims 1 to 13,
characterized in that
the three-pole reinforcing element (2) is designed as an expanded three-pole reinforcing element, in which an electronically controllable quiescent current source (Iso) and / or an electronically controllable quiescent voltage source (U _D0 ) is present, by means of which the active gain is reduced in connection with the reduction according to the invention Antenna due to excessive reception level, the quiescent current (Iso) and / or the quiescent voltage (U _D0 ) in the input bipolar transistor (49) or input field-effect transistor (13) is increased (Fig. 9d, 6). Active broadband receiving antenna according to one of Claims 1 to 13,
characterized in that
the passive antenna part (1) is designed with a connection point (18), the two connections of which are high relative to the ground (0), each of which is connected to a control connection (15, 16) of a three-pole amplifying element (2), the source connections ( 24a, b) are connected to the primary side of a transformer (38) designed as an isolating transformer, the secondary side of which has different outputs for designing different transmission ratios (t) and from which - together with switching diodes (36) - the adjustable transmission element (34) is formed and the drain connections (53) are connected to the ground (0) (Fig.10). Active broadband receiving antenna according to one of Claims 1 to 13,
characterized in that
for the design of a plurality of transmission frequency bands, a plurality of bipolar transistors (14, 14 ') for expanding the three-pole amplifying element (2) and for combining a plurality of three-pole amplifying elements (2,2') are present, the base electrodes of which are connected to the source electrode of a common input Transistors (13,49) or to the source connection of an extended three-pole amplifying element according to claims 16, 17, 18, 19 and which are each in emitter follower circuit with the input of a low-loss filter circuit (3, 3 ') to form separate Transmission paths for the relevant frequency bands are connected and in each of the transmission paths an adjustable transmission element (34, 34 ') and a control amplifier (33, 33'), which each use filter measures to assign only the frequency band assigned to the transmission path concerned from the high-frequency received signal (8) is fed, is present and the Re gel signal (42, 42 ') is supplied to the associated adjustable transmission element (34, 34') (Fig. 11). Active broadband receiving antenna according to claim 21
characterized in that
the control signals (42, 42 ') are derived from the output signal of the active antenna by selection means and control amplifiers (33, 33') in the receiver (44) and are supplied to the active antenna via control lines (41) (FIG. 12). Active broadband receiving antenna according to one of claims 1 to 22
characterized in that
there are a number of passive antenna parts (1) with frequency-dependent directional diagrams of the effective lengths l _e which differ in terms of magnitude and phase with respect to incident waves, which are in electromagnetic radiation coupling to one another and together form a passive antenna arrangement (27) with a plurality of connection points (18a, b, c), each of which is connected to an amplifier circuit (21a, b, c) and supplemented to form an active antenna according to the invention, so that the amplifier circuits (21a, b, c) are connected to the passive antenna parts (1 ) there is no noticeable mutual influence of the received voltages and the high-frequency received signals (8a, b, c) are combined in a weighted manner in an antenna combiner (22) and in the active receiving antennas a control amplifier (33) for monitoring the high-frequency received signal (8) at the antenna output is available. Active broadband receiving antenna according to one of claims 1 to 22,
characterized in that
there are a number of passive antenna parts (1) with frequency-dependent directional diagrams of the effective lengths l _e which differ in terms of magnitude and phase with respect to incident waves, which are in electromagnetic radiation coupling to one another and together form a passive antenna arrangement (27) with a plurality of connection points (18a, b, c), each of which is connected to an amplifier circuit (21a, b, c) and supplemented to form an active antenna according to the invention, so that the amplifier circuits (21a, b, c) are connected to the passive antenna parts (1 ) there is no noticeable mutual influence of the received voltages and the high-frequency received signals (8a, b, c) are weighted together in an antenna combiner (22) and a common control amplifier (33) is present, the control signal (42a, b, c) of the transmission networks (31a, b, c) in the active antennas for lowering the summed high-frequency reception signal Is (8) is fed (Fig. 13). Active broadband receiving antenna according to claim 24,
characterized in that
the active receiving antennas are used in an antenna diversity system for vehicles and the passive antenna parts (1) are selected in such a way that their received signals in a Rayleigh reception field are as independent as possible in terms of diversity and the high-frequency received signals (8) are non-reactive, i.e. without the diversity of independence Influencing received signals are available for selection in a scanning diversity system or for further processing in one of the other known diversity methods (FIG. 14). Active broadband receiving antenna according to claim 25,
characterized in that
the active receiving antennas are used in an antenna diversity system for vehicles and the passive antenna parts (1) are selected in such a way that their received signals in a Rayleigh reception field are as independent as possible in terms of diversity and the high-frequency received signals (8) are non-reactive, i.e. without the diversity of independence To influence received signals, for selection in a scanning diversity system or for further processing in one of the other known diversity methods, and the level of the selected signal is fed to a common control amplifier (33) in which a control signal (42) is formed and the Transmission networks (31) in the active receiving antennas for lowering the selected high-frequency received signal (8) is supplied (Fig. 14, 15). Active broadband receiving antenna according to claim 25
characterized in that
A control amplifier (33) for monitoring the high-frequency received signal (8) at the antenna output is present in the active receiving antennas (21) (FIG. 16). Active broadband receiving antenna according to claims 25 and 26
characterized in that
To improve the diversity-independent of the received signals of the passive antenna parts (1) whose connection points (18) are loaded with separately determined reactive conductance values (23) parallel to the input of the amplifier circuit (21) (Fig. 16). Active broadband receiving antenna according to Claims 1 to 28,
characterized in that
When setting the transmission network (31) for small high-frequency reception signals (8), the active conductance (5) effective at the output (4) of the low-loss filter circuit (3) is designed by the input resistance of a high-frequency line (10) loaded at its end with the load resistor (9) is and the load resistance (9) by the input impedance of a continuative. Amplifier unit (11) is formed with the noise figure F _v and the real part G of the effective admittance (7) is chosen to be sufficiently large that the noise contribution of the amplifier unit (11) is smaller than the noise contribution of the field effect transistor (2) (Fig. 5). Active broadband receiving antenna according to one of claims 1 to 29
characterized in that
for the broadband creation of favorable transmission conditions in the filter circuit (3) there is a transformer (24) with a suitable transmission ratio ü. Active broadband receiving antenna according to one of Claims 1 to 19,
characterized in that
frequency-selective transmission paths for frequency-selective decoupling of high-frequency received signals (8) for different transmission frequency bands at several outputs are designed in the low-loss filter circuit (3) on the basis of signal branches. Active broadband receiving antenna according to one of Claims 1 to 31,
characterized in that
the passive antenna arrangement (27) is present as conductor structures on a plastic carrier inserted in the recess of a conductive vehicle body or on the window pane of a vehicle, for example in the form of one or more heating fields and / or conductor structures separate from the heater, and a plurality of connection points (18 ) for the formation of passive antenna parts (1) for connecting amplifier circuits (21) are present (FIGS. 15, 16). Active broadband receiving antenna according to one of Claims 1 to 31,
characterized in that
the passive antenna arrangement (27) is designed as an essentially coherent conductive surface applied to suppress radiation transmission in the infrared range with a sufficiently small surface resistance on the window pane of a car and suitably positioned for decoupling received signals at the edge of the conductive surface that is not connected to the conductive body Connection points (18) with amplifier circuits (21) are formed, the high-frequency received signals (8) via high-frequency lines (10) for designing a directional antenna, an antenna combiner (22) or for designing a scanning diversity system, an electronic switch (25), or are supplied to design a diversity arrangement operating according to any other method. Active broadband receiving antenna according to one of Claims 1 to 31,
characterized in that
the passive antenna part is derived from a vehicle part that was not originally intended for use as an antenna and its design can be changed only slightly, and a connection point (18) for forming a passive antenna part (1) is formed on this element and for the polarization applicable in the useful frequency range and elevation of an incident wave, a certain azimuthal mean value D _{m of} the directional factor is determined and the real part R _{A of} the impedance Z _{A of} the passive antenna part (1) is given in the transmission frequency range in the range between R _amine and a maximum value R _amax (FIGS. 18a, b , c, d). Active broadband receiving antenna according to one of Claims 1 to 34,
characterized in that
A modern digital computer is available and both the impedance Z _{A of} the passive antenna part (1) is measured or calculated and the azimuthal average value D _{m of} the directional factor determined by the measurement or calculation is stored in the digital computer and in which suitable for various characteristic possible frequency profiles of antenna impedances are stored Basic structures for low-loss filter circuits (3) are stored in the digital computer and the blind elements of the low-loss filter circuit (3) are determined for a predetermined average gain of the active antenna using known strategies of variation calculation. Active broadband receiving antenna according to one of Claims 1 to 35,
characterized in that
the low-loss filter circuit (3) is designed as a T-half filter or T-filter or as a chain circuit of such filters, the series or parallel branch of which is formed in each case from a combination of reactances in such a way that both the absolute value of a reactance in the series branch (28) as well as the absolute value of a reactive conductance in the parallel branch (29) is sufficiently small within a transmission frequency range and sufficiently large outside such and the high-frequency received signal (8) is fed to the control amplifier (33) at the output and from whose control signal (42) the adjustable transmission member (34) is controlled (Fig. 19a, b). Active broadband receiving antenna according to one of Claims 1 to 36,
characterized in that
for the purpose of spatial separation of a miniaturized front end of the active antenna, the low-loss filter circuit (3) contains a high-frequency line (10) as an element that transforms the effective admittance (7) in a frequency-dependent manner (FIG. 5). Active broadband reception antenna for FM radio reception in the car according to one of Claims 1 to 32,
characterized in that
the passive antenna part (1) is designed by a conductor structure printed on a dielectric carrier, such as a window pane or a plastic carrier, and the low-loss filter circuit (3) is designed as a bandpass filter with a pass in the VHF frequency range and high-impedance input impedance outside the VHF frequency range ( Fig. 1). Active broadband receiving antenna according to one of Claims 1 to 38,
characterized in that
to increase the effective length l _{e of} the passive antenna part (1) between its connection point (18) and the input of the amplifier circuit (21), there is a transformer (24) with a sufficiently high-impedance primary inductance and a suitably chosen transmission ratio (Fig. 17).

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