NL8400770A - AMPLIFIER FOR A CAR AERIAL. - Google Patents

Description

- 1 -

Amplifier for a car antenna.

The invention relates to an amplifier for a car antenna for the long, middle and short wave area (LMK area) and the ultra short wave area (UK area) for connection to traditionally known passive car antennas, 5 to windscreen antennas, to antennas with a short rod and other electromagnetic radiation absorbing structures.

Electronic car antennas, in which the signals from the LMK and the UK area are amplified in separate active elements, are currently essentially designed according to the following switching principles, for which protective rights are applied for respectively. a) DE-AS 1919749 describes a device in which separate active transmission paths for the LMK and the ÜK region between the passive antenna conductor which receives the radiation and the output terminal of the electronic antenna are each formed.

b) In DE-PS 2310616, a special embodiment of the formation of separate transfer paths between the receiving antenna conductor and the output terminal is protected by means of an inductively coupled band filter for the UK area.

c) In DD-PS 139680, switching measures are protected, which enable the signals of the LMK and the UK area of the recording passive antenna conductor to be shared via a signal path while avoiding additional load capacities at the input of a field effect transistor, in which only the LMK region is amplified and acts in the UK region through a short-circuit approximation state of its drain-source path as a capacitance, which is a component of the primary circuit of a band filter for the UK area.

The signals from the LMK and the UK region are divided over separate transmission paths at the output of the field-effect transistor.

According to DE-AS 1919749 and DE-PS 2310616 as well as 35 the publications below,

Lindenmeier, H .: Wirkungsweise und Technik einer aktiven Car antenna - Funkschau 1969, Heft 17, page 569-571; Lindenmeier, H .: Wirkungsweise und Leistungs ability 840077ö ϊ ΐ - 2 - <more modern Car antennae - NTZ 1974, Heft 1, page 17-23;

Lindenmeier, H .; Meinke, H.H .: Electronic Car Antennas - Heute - Funkschau 1976, Heft 14, page 68-70; and 5 Lindenmeier, H .: Aktive Autoantennen für Standardemp- fanger und electronically abstimmbare Empfanger, Rundfunk-technical Mitteilungen 1977, Heft 6, page 253-260, the base point impedance of the passive antenna conductor is part of the primary chain of a band filter 20 for the UK area.

In DD-PS 139680, Figs. 3 and 4, the corresponding ones are shown.

replacement schemes shown- They show that the impedance of the passive conductor is active in the high jbunt of the primary chain. The usual length of the antenna rod for electronic car antennas of about 40 cm is determined by the fact that at this length of the rod the base point impedance is high-ohmic and capacitive, and with the self-inductance of the primary chain determines the resonance frequency and the quality in the 20 company determines. At approximately the same quality in the operation of the secondary chain and critical or slightly over-critical coupling, a bandwidth is created which ensures uniform signal transmission within the UK area and gives good selection values. This applies in the same way for the solution according to the invention of the DD-PS 139680. There, in Fig. 8, the switching device for a base point coupled band filter for the UK area is indicated. Naturally, this also applies to the bandwidth of a single chain, which is indicated as a frequency determining transmission element in variants with little equipment.

The base point impedance of a 40 cm bar in the UK region is approximately (10 - 150) ohms as parallel replacement circuit 2.26 kOhm parallel to llpF. This functional dependence of the bandwidth transfer ratio of the impedance connected to the high point of the primary circuit in the order of magnitude is a drawback in such cases in which the base point impedance of the passive antenna conductor is approximately real and of the order of the magnitude of the wave-40 resistance of conventional high-frequency lines is ,84007ί 0 ~ 3 ~ £ - * as is the case, for example, with known geometries of antenna conductors of windscreen antennas or with traditionally known passive car antennas. In these cases, the quality of the primary circuit of the band filter decreases and the bandwidth increases. The known measures for impedance transformation on vibration circuits are no longer applicable, since additional impedances with respect to the reference voltage adversely affect the transmission behavior in the LMK region and are therefore not permissible. As a result, the transfer characteristics of the bandpass with regard to selection, frequency dependence of the transmission attenuation and the adaptation for minimal noise cannot be dimensioned as with the given application of construction parts at the moment of practical use would be desirable.

DE-OS 211567 and its divisional DE-OS 2166898 disclose a switching device in which the different frequency regions are jointly amplified in a field-effect transistor and the distribution over different transmission paths takes place such that at the source the signals from the LMK area and the signals from the UK area are disconnected at discharge. The separation of the signals from the UK region and the LMK region over separate transmission paths at the output of a field effect transistor avoids the additional capacitive load on the control electrode of the field effect transistor and the sensitivity in the LMK region. improved. Switching devices in which the signals of the different frequency regions are amplified in common inactive elements, however, in contrast to the described switching devices with separate transmission paths, have, among other things, substantially worse properties with strong signals, due to the non-linearity. of the transmission characteristic, the signals from the UK and LMK regions interfere with one another, so that overall the disadvantages are considered. Such switching concepts have not found any partial application. See also Rundfunktechnische Mit-40 teilungen 1977, Heft 6, page 257, point 4.1 8 4 0 G 7 7 0 - 4 -

According to the characteristic part of the main claim of DE-OS 2166898, the capacitance of the passive antenna conductor is part of a vibration chain for the UK area. So far, the disadvantages mentioned above in the same context also apply here.

Due to the increasing transmitter density, the field strength in the UK area increases in almost all reception areas, thereby improving the reception quality, but also increasing the probability of the occurrence of disturbances, which are known to those skilled in the art under terms such as in-termodulation, cross-modulation , multiple reception, etc.

Car receivers in particular have been exposed to very different field strength conditions, so that they have to meet particularly high requirements with regard to resistance to strength signals. The technical further development of the car receivers has led in recent years to the fact that the sensitivity of such modern receivers in the UK area can only be improved to an insignificant extent by an electronic car antenna, while on the other hand the properties are deteriorated at strong signal . In the LMK area, the advantages of electronic car antennas eg with a short antenna rod, with rear mounting (Heck mounting) of the antenna or with a windscreen antenna design, are beyond doubt. It therefore seems advantageous in the electronic part of the antenna to amplify only signals from the LMK region and to supply the signals from the UK region without amplification to the output terminal of the electronic antenna.

In the DD-PS 139680 a switching device is indicated, in which, according to the description of the invention, only the signals of the LMK region are amplified and the signals of the UK region are amplified, eg according to Fig. 8 via a foot-point coupled band filter can be supplied to the output terminal.

In DE-OS 2932651 one wants to protect a high-frequency amplification device, in which, as is known from the DD-PS 139680, only signals from the LMK region are amplified and capacitive bridging is provided for the signals from the UK-40 region. . According to 8400770-5 - 'a number of subclaims, the base point impedance of a passive antenna conductor is part of various vibration chains or band filter configurations. In a further subclause, the condition is set that the gain of the amplifier for the LMK region is approximately 1 and the phase shift is approximately 0 °. With regard to the transmission properties in the LMK region, this switching device has considerable drawbacks, since the signal-to-noise ratio is deteriorated for a number of reasons set out below. The bridging capacitance loads the high-ohmic input of the LMK region in a known manner, the voltage amplification is noticeably smaller than 1 due to the series connection of a source and an emitter follower and the transistors make an additional contribution to the noise. In the LMK region, signals are available at the output of the amplifier which have a lower voltage and a lower signal-to-noise ratio than is the case in the passive antenna conductor. Insofar as the use of such a switching device seems questionable. Also, the low output impedance of the emitter follower compared to the high-resistance capacitive impedance of the passive antenna conductor shows no advantage in the LMK region in cooperation with the car receiver.

The object of the invention is to indicate a switching device for a car antenna amplifier, which is connected to old-fashioned car antennas to short-rod antennas, windscreen antennas or other electromagnetic radiation-absorbing constructions, which connect impedances of the large have the order of conventional conductor wave resistances. For these connection impedances, no adaptation conditions can be realized with the known switching devices of the so-called "band filter antennas" in the UK area, with which the same favorable transmission properties as with a high-impedance source, of which the impedance, frequency and quality in the operating component of the primary chain is a band filter can be achieved.

This drawback should eliminate the above-mentioned switching device and moreover allow the transfer path 8400770 r r - 6 - of the UK region to be passive or active and in the transfer path of the LMK region the gain and phase conditions to no particular values are bound. Due to the possibility of passively effecting the transmission path of the UK area 5, the disturbances which often occur with car antenna amplifiers or electronic car antennas are completely eliminated by strong signals. Particularly advantageous, that in this case it is not necessary to abandon the gain in the LMK region, in contrast to the DE-OS 2932651. Overall, these design options result in a substantially higher degree of freedom in optimizing the reception properties of car antennas. than is the case with the known shifting devices.

The problem of the invention is to indicate a switching arrangement for a car antenna amplifier, the input resistance of which in the UK region is low-ohmic on the order of usual line wave resistors and whose transmission characteristic in the UK region can be as high as that it approaches that of a bandpass filter crossover curve with slightly supercritical coupling and is largely independent of the source impedance, the load resistance at the amplifier output in the UK region also being low-ohmic on the order of magnitude of common line wave resistances must be.

The transmission route for the UK area must be passive with low attenuation, but also active.

30 In the LMK area transfer path, gain and phase conditions must not be tied to any particular values. This problem is solved with a car antenna amplifier for the UK and LMK area, whose input resistance in the LMK area is high impedance and which has a low input capacity, and in which the signals from the UK and LMK area of the input terminals are transferred through a capacitance and a longitudinal inductance to the gate electrode terminal of a field-effect transistor, a capacitance being connected to its output-source path parallel-40 lel, which in the LMK region transmits the transfer 8400770 - 7 - * does not affect drag in the UK region, however, the source-source path approximately short-circuits, causing the field-effect transistor to operate between capacitance electrode and drain connection as a capacitance and between the source terminal and the operating voltage terminal, which for high frequencies via a capacitance is connected to the reference voltage, a choke blocking the UK area signals is outputted and the UK area signals by r the drain connection is passed through a separation capacitance to a separate transfer path and the signals from the LMK region of the source connection are fed through a choke blocking the signals from the UK region into a separate active transfer path from the output connection, thereby solved, that the input resistance in the UK region is low-ohmic of the great order of conventional line wave resistances and that the longitudinal inductance and the capacitance operating between the control electrode terminal and the drain terminal form a series trolling circuit which is between the input terminal and the output terminal 20 or the input of a UK area amplifier is a frequency selective passive transfer element for the UK area or that the choke is replaced by a self-inductance and the series of vibrating chain operating between the input terminal and the drain terminal with a further series connected to the drain terminal vibration chain one A full T-element band pass which acts as a frequency selective passive transfer element 30 between the input terminal and the output terminal or the input of an amplifier for the UK region.

The low input resistance of the order of conventional lead wave resistances, is realized that instead of the known formation of a parallel vibration circuit or a band filter for the transmission of the signals in the UK region, a series of vibration chain in the long branch of the UK region transfer path whether a band-pass operates in the manner of full T element or half T element. It is known from the theory of such sieve circuits that they can be made for source and load resistors of the order of 84 0 0 7 7 0 9 V - 8 and for the indicated frequency range. The transition from the band filter principle to the band pass principle has significant significance for realizing the above-mentioned specifications of the invention. Band passages are more suitable for larger bandwidths than band filters. They allow greater edge slopes at the tire boundaries and exhibit lower throughput attenuation as well as better adaptation values.

According to known sizing instructions, for example, at a bandpass of the UK region, in the manner of a complete T-element with cross induction and a source or load resistor of 150 ohm, a series chain capacity of approximately 5pF is created. This value approximately corresponds to the sum of the gate electrodes source capacitance and the drain gate electrode decapacity of today's blocking layer field effect transistors / which allows the use of the field effect transistor as vibration chain capacitance. The stated rated input resistance for car receivers in the UK-20 range is 150 ohms.

The operation of the solution according to the invention is explained in more detail below. The signals from the UK and LMK regions reach the control electrode of a field effect transistor jointly from the input terminal of the antenna amplifier via a separation capacitance and a longitudinal induction. For the case of signal transmission in the UK region, the field-effect transistor acts as a capacitance by the substantially complete short-circuiting of its drain-source path between the gate electrode terminal 30 and the drain electrode terminal, the value of which from the gate electrodes source capacitance and the drain gate electrode capacitance by addition and which, with the longitudinal induction, forms a series vibration chain for the UK area. In the simplest case, the drain connection is connected via separation capacity to the output connection of the car antenna amplifier. Feedbacks in the LMK area from the output terminal to the high-impedance electrode terminal cannot occur, as the drain terminals are connected via a 40 choke blocking the signals from the UK area 8400770 «- 9 - and for the signals from the LKM area practically short-circuited to the operating voltage terminal, which is identical with the reference voltage in high frequencies. If the transmission characteristic of a series vibration chain for the UK region is sufficient, then this solution is a low-equipment variant. Larger bandwidths and very small differences in the throughput attenuation within the transmission area can be realized if the series of vibration chain operating between the input connection and the drain connection with a self-inductance between the drain and the operating voltage connection and a further series of vibration chain between the drain and the output connection up to a bandpass of the type of a complete T element is combined.

Further embodiments of the transfer properties in the UK region are given by the fact that the transverse branch of the band pass is equipped except with a coil having a capacitance or a parallel vibration circuit. This makes it possible to perform the damping behavior outside the transmission area according to known principles.

If the series of vibration chain connected to the discharge connection is dispensed with, a band pass of the type with a half-T element is created. This embodiment variant has advantages over adaptation to an amplifier for the UK area.

The passive frequency-selective transmission elements for the UK region, which can be implemented in different variants, can be connected passively to the output terminal-UK transmission path 30 - or to the input of an amplifier - UK transmission path active.

The structural elements connected to the field-effect transistor and functionally related to the transfer path from the UK region are practically inactive in the IMK-35 region so that the field-effect transistor acts as a source follower in known manner.

The invention is further elucidated on the basis of exemplary embodiments. The representations shown mean: Fig. 1 shows a principle representation of the switching device 40 according to the invention with a series of vibration circuit as 8400770 *. - 10 - * frequency selective transmission element in the UK transmission path; FIG. 2 is a replacement diagram of the UK transmission path of FIG. 1; Fig. 3 shows a principle view of the switching device according to the invention with a bandpass of the type with a complete T element as a frequency-selective transmission element in the UK transmission path; FIG. 4 is a replacement diagram of the UK transfer path 10 of FIG. 3; Fig. 5 shows a principle view of the switching device according to the invention with a band-pass of the type of a half-T element as a frequency-selective transmission element in the UK transmission path; Fig. 6 is a replacement diagram of the UK transfer path of Fig. 5; FIG. 7 is a replacement diagram of the operation of the field effect transistor as capacitance; Fig. 8 shows a part of a circuit with a capacity as a transverse branch of the band passage according to Fig. 4 and Fig. 6; FIG. 9 is a partial schematic view of a parallel vibration circuit as the transverse branch of the bandpass of FIG.

4 and 6; Fig. 10 shows a replacement scheme applicable to the handover in the IMK area; and Fig. 11 shows a complete circuit of an amplifier for 'I. windscreen antennas.

In FIG. 1, signals from the UK and LMK regions 30 are applied in common through a separation capacitance C1 and a longitudinal inductance L1 to the control electrode of a field effect transistor VI, the drain-source path of which is connected in parallel to a capacitance C4, which is UK region of FIG. 7 creates a short circuit, so that the field effect transistor VI between its control electrode and its drain terminal acts as a capacitance C7. The series vibration circuit LI, C7 is connected via C3 to the output terminal 3 on the input of an amplifier V2 for the UK area. Fig. 2 shows the replacement 40 scheme as it operates for signal transmission in the 8400770-11-1% UK region. The drain terminal is connected to the operating voltage terminal 2 via the choke coil L4r which blocks the signals in the üK region. The operating voltage terminal, which concerns high frequencies, is connected to the reference voltage via C5. For the operation of the field effect transistor VI as a source follower in the IMK region, the replacement scheme shown in FIG. 10 applies. The LMK region signals are applied to the output terminal 3 via the LMK region amplifier V3 and a choke K6 blocking the UK region signals.

In Fig. 3, with the series vibration circuit L1, C7 and a cross induction L2 and a further series vibration circuit C2, L3, a band pass of the type with a complete T-element is formed.

Fig. 4 shows the replacement schedule in place for the transfer of the UK territory. Instead of the cross inductance L2, a capacitance C8 and a parallel vibration chain L7, C9 can also be connected. Switching technical realization options are shown in Fig. 8 and Fig. 9.

In Fig. 5, with the series vibration circuit L1, C7 and a cross inductance L2, a band pass of the type with a half T element is formed.

Fig. 6 shows the replacement schedule effective for the transfer of the UK area 25. Here too, instead of the cross inductance L2, a capacitance C8 or a parallel vibratory circuit L7, C9 can be connected.

Fig. 10 shows a complete switching arrangement of a windshield antenna amplifier.

30 The UK transfer path is passive with a band pass of the type with a full T element with cross induction. For better visualization, reference numbers from the principle representation of Figures 1 to 9 have been used.

Conclusions 35 --- 8400770

Claims (3)

1. Car antenna amplifier for the UK and LMK area / whose input resistance in the LMK area is high-resistance and has a low input capacitance and in which the signals of the UK and LMK area from the 5 input connection (1) are separation capacitance (C1) and a longitudinal inductance (LI) on the control electrode terminal of a field-effect transistor (VI) are transferred, a capacitance (C4) being connected in parallel to its drain-source path, which capacitance in the LMK-10 region does not transfer behavior , but in the UK area the drain-source path approximately short-circuits, causing the field-effect transistor (VI) between the control electrode and the drain terminal to act as a capacitance (C7) and between the drain terminal and the operating voltage terminal (2 ), which is connected to the reference voltage via a capacitor (C5) with regard to high frequencies, a choke (4) is included, which blocks the signals from the UK area and the signal UK area from the drain connection through a cutoff capacitance (C3) to a separate transfer path and the LMK area signals from the source connection through a choke (L5), which is the UK signal region, are fed in a separate active transmission path to the output terminal (3), characterized in that the input resistance in the UK region is low-ohmic on the order of usual line wave resistances and the longitudinal inductance (LI) and the capacitance operating between the control electrode terminal and the drain terminal form a series vibration circuit, which forms a frequency selective passive transfer element between the input terminal (1) and the output terminal (3) across the input of an amplifier (V2) for the UK area. for the UK area is whether the choke (L4) has been replaced by an inductance (L2) and the series vibration circuit operating between the input connection (1) and the discharge connection ( L1, C4) with a further series vibration circuit (C2, 8400770 - 13 - L3) connected to the discharge connection, forms a band pass of the type with a complete T element, which is located between the input connection (1) and the output connection (3) or the input of an amplifier (V2) for the UK region when frequency selective passive transfer element is operating. Auto antenna amplifier according to claim 1, characterized in that the self-inductance (L2) is replaced by a capacitance (C8) or a parallel vibration circuit (L7, C9). Car antenna amplifier according to claim 1, characterized in that the series of vibration circuit 15 (L1, C7) acting between the input connection (1) and the drain connection with the inductance (L2) or capacitance (C8) connected between the drain and the operating voltage connection ) or parallel vibration circuit (17, C9) forms a band pass of the half T element type passing between the input terminal (1) and the output terminal (3) or the input 20 of an amplifier (V2) for the UK region acts as a frequency selective passive transfer element. 8400770