DD202358A1 - SELECTIVE SPOOL-FREE AMPLIFIER FOR MEDIUM FREQUENCIES - Google Patents

Abstract

The aim of the invention is to provide a coil-free selective amplifier for medium frequencies with respect to conventional Filterverstaerkern comparable parameters under the aspect of reducing the balancing effort and Integrationsfaehigkeit. For this purpose, the invention "selective coil-free amplifier for medium frequencies" was developed based on known solutions of passive feedback amplifier expanded the frequency range of use under consideration parasitischer influences and primarily in devices of commercial communications and instrumentation and broadcasting technology application. A signal frequency mixture passes through a Verknuepfungsnetzwerk and a first amplifier to a first phase shifter and from the output to a second Verstaerker another phase shifter and a frequency-determining network existing active Brueckensperrfilter whose output is connected to another input of the Verknuepfungsnetzwerkes. Signals deviating from the blocking frequency arrive in an inverse phase-locked manner to the input signal to the linking network and cause almost complete compensation, while signal frequencies lying in the blocking frequency range of the active return path are not affected and can be removed at the output of the first amplifier.

Description

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Title of the invention

Selective coil-free amplifier for medium frequencies

Field of application of the invention

The invention relates to a selective coil-free amplifier for medium frequencies for use in devices of commercial communications and measurement technology and in particular for devices of the dog radio technology,

Object of the invention

The aim of the invention is to provide a coil-free selective amplifier for medium frequencies with respect to amplifiers with conventional filters comparable parameters without significantly increased expenses with an increase in reliability and reduction of balancing effort under the aspect of integration capability.

Characteristic of the known technical solutions

To realize selection tasks in devices with receive frequency conversion, ceramic and crystal filters are used, taking into account the reduction of adjustment costs, the former being used primarily in consumer electronics due to low costs *

Ceramic filters show a wide tolerance of the filter parameters at bandwidths of B 1% with respect to the center frequency,

Due to their high quality, crystal filters are suitable for securing strict selection requirements, their use being restricted to special fields of application. The same applies to electromechanical filters.

For full utilization of the parameters of the said selective means the most optimal adaptation is to be realized, which can not be practically always fully realized.

Yorteilig affects a concentrated selection and a concentrated gain under the aspect of the reduction of matching points and the integration of amplifier elements, disadvantageous lifting resonances are compensated by suitable Siebmittel, usually LC filter. Also known are active RC structures that are used to solve selection tasks, especially in the MF area as LC filter equivalent,

RC structures are accessible to integration and on this basis can be produced in an intolerance-tolerant manner. Their field of application extends up to frequencies of f = 100 kHz with reasonable technical and economic effort.

The parasitic phenomena occurring at higher frequencies limit the range of application, with demands for temperature stability and tolerance accuracy becoming increasingly important.

Active blocking filters are also known whose range of application extends to a few hundred kilohertz and which permit high attenuation ("Electronics" 45 (1972) H, 18, p. 80 and rfe-Nachrichten, rfe 21 (1972) H. 24, p. 783).

Realizable filter amplifiers for frequencies around 100 kHz use high-loss passive negative feedback quadripasses, eg, T-links. However, the effort to produce bandpass filter characteristics is relatively high. The demand for optimal insertion of the four poles has economic and technical limits, which ultimately leads to compromise solutions (Ebert, Peter, An Active RC Filter, Electronic Yearbook 1976, pp. 75 ff.).

Explanation of the essence of the invention

The invention described in the application of a selective coil-free amplifier exploits the high attenuation values that can be generated with an active blocking filter arrangement at the blocking frequency in the negative feedback branch, wherein high operating qualities can be generated while ensuring system stability.

According to the invention, a frequency-independent amplifying Yorwärts branch and a

frequency-dependent active feedback branch arranged. For this purpose, a first amplifier is arranged in the forward branch, the input of which is connected to the output of a logic network and the output of which is connected to a second amplifier forming part of the feedback branch via a first phase transmitter. The output of the second amplifier is once directly and once connected via a second phase shifter with a frequency-determining RC Hetzwerk whose output is connected to an input of the logic network. Another input of the link network is connected to a source providing a signal frequency mix. At the output of the first amplifier, the selected signal is removable.

According to the invention, the frequency-dependent feedback branch is realized as an active RC network with band blocking behavior, wherein the frequency-determining Hetzwerk with the second amplifier and the second phase shifter forms a bridge network high blocking loss.

embodiment

The invention will be described with reference to an embodiment in more detail

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Figure 1 shows a selective coil-free amplifier for. medium frequencies with active feedback branch.

FIG. 2 shows an embodiment of a frequency-dependent bridge network,

A signal mixture to be selected passes via an input 1 of a logic network 2 whose output 3 is connected to a first amplifier 4 and whose output 5 is connected via a first phase shifter 6 to a second amplifier 7 forming part of the feedback branch. From the output 8 of the second amplifier 7, the amplified phase-rotated signal once phase-locked and once passed through a second second amplifier 7 downstream phase shifter 9 phase-locked to a frequency-determining RC Hetzwerk 10 whose output 11 is connected to a second input 12 of the logic network 2.

The elements of the return branch are arranged in such a way that an active bridge network with band blocking behavior is realized, wherein the blocking frequency is determined by the network 10.

Sin the feedback branch feeding outside the notch frequency signal passes to the input signal phase-locked undamped to the logic network 2 and causes an almost complete compensation of the input signal of this frequency, wherein at the output 5 of the first amplifier 4, no signal occurs.

A lying in the region of the blocking frequency of the bridge network signal acts heavily attenuated at the input 12 of the linking network 2, so that only a small dependent on the stopband attenuation of the active Rückfuhrzweiges influencing the input signal occurs and this as a selected signal at the output 5 of the amplifier 4 is removable.

FIG. 1 shows a selective coil-free amplifier for medium frequencies.

Pigur 2 shows an exemplary embodiment of a frequency-dependent bridge network with band-stop behavior, wherein the complex resistors Z 1 and Z _{2 are} passive RC IT networks.

Claims (3)

claims 1, Selective coil-free amplifier for medium frequencies, characterized in that a first amplifier (4) is arranged, the input of a linking network (2) is connected upstream and whose output (5) to a first phase shifter (6) is connected, that the phase shifter (6) following a second amplifier (7) is arranged, the output (8) once directly and once via a second phase shifter (9) with a frequency-determining network (10) is connected, the output (11) to an input (12) the linking network (2) is connected to the other input (1) a signal mixture to be selected is performed and that further at the output (5) of the first amplifier (4) the selected signal is removable. 2, Selective coil-free amplifier according to item 1, characterized in that a frequency-independent amplifying from the linking network (2) and the first amplifier (4) existing forward branch and a frequency-dependent active from a first and second phase shifter (6, 9), a second amplifier (7) and a frequency-determining network (10) existing return branch is arranged. 3, Selective coil-free amplifier according to item 1 and 2, characterized in that the frequency-dependent active feedback branch as formed from the frequency-determining network (10), the second amplifier (7) and the second phase shifter (9) bridge circuit formed with band blocking behavior. For this J2L drawings drawings