Variable lc-band-pass filter

FIELD: physics.

SUBSTANCE: variable LC-band pass filter consists of n cascaded L-shaped half sections of high-pass filters, each having capacitors in a series circuit. The first lead of the capacitor is the first input of the half section and the second lead is the output which is connected to an inductor coil whose second output is connected to another capacitor. The input of the first half section is connected to the input potential terminal of the filter. The second leads of the capacitors which are connected in parallel circuits of the half sections are connected to a common bus. The output of the last half section is cascaded with m L-shaped half sections of low-pass filters, each consisting of an inductor coil and in a series circuit and a capacitor connected in parallel. The first leads of this inductor coil and the capacitor are the input of the half section and their second leads are the output which is connected to another capacitor. The output of the last half section is connected to the output potential terminal of the filter and the second leads of capacitors in the parallel circuit of the last ℓ half sections low-pass filters are connected to the common bus. k<n and ℓ<m are any integers. The invention is distinguished by that the filter has four groups of switches. The first group consists of n-k switches whose first leads are connected to input leads of half sections of the low-pass filter, starting with the k+1-th to the n-th half section respectively. Second leads of these switches are connected to the output of the high-pass filter. The second group consists of n-k switches whose first leads are connected to second leads of n-k capacitors connected in the parallel circuits of high-pass filters starting with the k+1-th half section to the n-th half section respectively. The second leads of these switches are connected to the common bus. The third group has m-ℓ switches whose first leads are connected to inputs of half sections of low-pass filters starting with the ℓ+1-th to the m-th, respectively. The first leads of these switches are connected to the output of the m-th half section. The fourth group consists of m-ℓ switches whose first leads are connected to second leads of m-ℓ capacitors connected in the parallel circuits of low-pass filters starting with the ℓ+1-th half section to the m-th half section, respectively. The second leads of these switches are connected to the common bus.

EFFECT: simplification.

1 dwg

 

The invention relates to electronics and can be used as preselect professional receiving device.

In modern radio receiving devices use different types of bandpass tunable filter LC-elements. Most filters can be divided into two groups. The first consists of filters, performed on LC-circuits, which have to rebuild the average frequency of the filter are tunable inductance, and often the so-called discrete capacitors [1].

This type of filter provides a relatively high demands on selectivity, however, is quite complicated to manufacture.

The second group includes the filters was performed on LC-elements and representing a set of bandpass filters connected serially or several pieces using switching devices. In particular, such a filter can be made in the form of cascading multiple units filters high-pass and low-pass filters [2]. At the same time to implement the necessary bandwidth at the specified operating frequency range requires appropriate filter sets the upper and lower frequencies, from which you select the right pair and with the help of the switching elements is connected between a cascade and connected between the input and output ol the selector.

This type of filter is more adaptable to production in comparison with the traditional band usually provides the best gain and we have chosen as a prototype.

The disadvantage of this device is that when a large number of tunable discrete bandwidths, it will be quite difficult.

Object of the invention is the simplification of the device.

The problem is solved in that the device consists of n cascaded included l-shaped polozenie high-pass filters, each of which contains a capacitor in a series branch, the first output capacitor is the input polozona, a second output that is connected to the inductor, the second terminal of which is connected to another capacitor, and the input of the first polozona connected to the input potential terminal of the filter, and the second terminals of the capacitors, which are in parallel branches of the first k polozenie connected to the shared bus, the output of the last polozona connected cascade m D-shaped polozenie low-pass filters, each of which contains a serial branch of the inductor and in parallel with it connected to the capacitor, the first conclusions of this coil and capacitor are the input polozona, and their second conclusions output that is connected to the other con is ensator, out of the last polozona connected to the output terminal of the device, and the second terminals of the capacitors of the parallel branches of the last l polozenie low-pass filters connected to a common bus, where m, n, l and k are any integers, with k<n and l<m, we have introduced four key groups, the first group consists of n-l keys, the first conclusions of which is connected to the input terminals of polozenie high-pass filters, since k+l-th and n-th, respectively, and the latter findings the keys are connected with the output of the high-pass filter, the second group consisting of n-k keys, connected to the first conclusions to the second conclusions n-k capacitors, which are in parallel branches of the filter upper frequencies starting with k+1-th polozona and to the n-th, respectively, the second, the findings of these keys are connected with a common bus, the third group contains m-l keys, the first conclusions are connected to the inputs of polozenie low-pass filters since l+1 and to m-th, respectively, the second, the findings of these keys are connected with the output m on polozona, the fourth group, consisting of m-l keys, connected to the first conclusions to the second conclusions m-l capacitors, which are in parallel branches of the low-pass filters since l+1-th polozona and to m-th, respectively, the second, the findings of these keys are connected to a common bus.

Comparative analysis shows that awseme technical solution differs from the prototype in that in the device additionally introduced four key groups, the first group contains n-k keys, the first conclusions which are connected with input terminals of polozenie HPF starting with k+1-th polozona and to the n-th, respectively, the second terminals of the keys connected to the output of the HPF, the second group consists of n-k keys, which the first pins connected to the second conclusions n-k capacitors, which are in parallel branches HPF starting with k+1-th polozona and to the n-th, respectively, the second, the findings of these keys are connected with a common bus, the third the group contains m-l keys, the first conclusions which are connected to the inputs of polozenie LPF starting with l+1-th polozona and to m-th, respectively, the second, the findings of these keys are connected with access to m-th polozona, the fourth group consists of m-l keys, the first conclusions which are connected with the second conclusions m-l capacitors, which are in parallel branches LPF starting with l+1-th polozona and to m-th, respectively, the second, the findings of these keys are connected to a common bus.

When comparing the proposed solutions not only prototype, but also with other known solutions in science and technology not found solutions with similar characteristics.

The drawing shows an electric diagram of the proposed device. The device contains n G-shaped polozenie HPF 1, each of which contains a capacitor in the longitudinal branch 2, to the exit of each polozona connected inductor 3, second, the conclusions of which is connected capacitors 4, main conclusions of the k first capacitors 4 are directly connected to a shared bus. To the output of the HPF 1 connected m polozenie LPF 5, each of the l-shaped low-pass filter consists of a parallel circuit in the longitudinal branches 6 and capacitors in the transverse branches 7, the first l capacitors directly connected to the shared bus. The device also includes a first group of keys 8, connecting inputs polozenie HPF with k+l-th to n-th to the output of the HPF, the second group of keys 9, providing a capacitor 4 to a common bus, a third group of keys 10 for connecting the inputs of polozenie LPF starting with l+1-th to m-th to the output of the LPF, the fourth group of keys 11, which provides connection of the capacitors 7 polozenie LPF starting with l+1-th to m-th to the common bus in the desired time sequence.

The device operates as follows.

The high-pass filter 1 consists of n polozenie, with the first k polozenie have a cutoff frequency fH1following it, polozeno (or more polozenie) have a cutoff frequency fH2>fH1following polozeno k+2 is the cutoff frequency fH3>f2and so, therefore, when the first key group 8 is closed, and the key group 9 are open, the HPF has a cutoff frequency fH1when closed the second key group 8 zamknutom first key group 9 HPF have a cutoff frequency f H2as to the first k polozeniem connected k+1-th level HPF with cutoff frequency fH2when open key group 8 and closed key group 9 HPF has the highest cutoff frequency fTM.

The lowpass filter 5 consists of m polozenie, the first l polozenie have a cutoff frequency fB1subsequent l+1-St polozeno has a cutoff frequency fB2<fB1the following l+2-e polozeno has a cutoff frequency fB3<fB2etc. so that the connection to the first l polozeniem LPF each subsequent polozona reduces accordingly the cutoff frequency of this low-pass filter.

Connect the required number of subsequent polozenie is ensured by appropriate choice of the position of the key groups 10 and 11. For example, when the switch is closed the second key group 10, the closed the first key and no other key group 11 the cutoff frequency of LPF is equal to fB2. When otkrytyj key group 10 and closed key group 11 LPF has the lowest cutoff frequency equal to the cutoff frequency of the last of his polozona.

Thus, by selecting the position of the key groups 8-11, you can specify the cutoff frequency of HPF-fbiand the cutoff frequency of LPF-fbiand receive bandpass filter with a bandwidth of fbi-f* in a given frequency range from fnto fin.

Sources of info the information

1. Sign A.E., Popov Y.S. Tunable electrical filter. M., "Communication", 1979, p.46-59.

2. Barefoot N Electric filters. Kiev, Gostekhizdat USSR, 1957, p.123, 144.

Bandpass tunable LC filter consisting of n cascaded included l-shaped polozenie high-pass filters, each of which contains a capacitor in a series branch, the first output capacitor is the input polozona, and a second output that is connected to the inductor, the second output of which is connected to another capacitor, and the input of the first polozona connected to the input potential terminal of the filter, and the second terminals of the capacitors, which are in parallel branches of the first k polozenie connected to the shared bus, the output of the last polozona connected cascade m D-shaped polozenie low-pass filters, each of which contains a serial branch of the inductor and in parallel with it connected to the capacitor, the first conclusions of this coil and capacitor are the input polozona, and their second conclusions output that is connected to another capacitor, and the output of the last polozona connected with the output potential terminal of the filter, and the second terminals of the capacitors of the parallel branches of the last l polozenie low-pass filters connected to a common bus, where k<n and l<m Liu the s integers, characterized in that the filter introduced four key groups, the first group contains n-k keys, the first conclusions of which is connected to the input terminals of polozenie high-pass filter, starting with k+1-th and n-th, respectively, and the second the findings of these keys is connected to the output of the high-pass filter, the second group consisting of n-k keys, connected to the first conclusions to the second conclusions n-k capacitors, which are in parallel branches filters, high-pass, starting with k+1-th polozona and to the n-th accordingly, the second the findings of these keys are connected with a common bus, the third group contains m-l keys, the first conclusions which are connected to the inputs of polozenie low-pass filters starting with l+1 and to m-th, respectively, the second, the findings of these keys is connected to the output of the m-th polozona, the fourth group, consisting of m-l keys, the first conclusions of which is connected to the second conclusions m-l capacitors, which are in parallel branches of the low-pass filters, since l+1-th polozona and to m-th, respectively second, the findings of these keys are connected to a common bus.



 

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