SU942246A1 - Discrete filter - Google Patents

Description

(5) DISCRETE FILTER.

/one.

The invention relates to radio engineering and can be used in analog and digital devices for filtering walkie talkies.

A known digital filter contains a counter whose outputs are connected to decoders, a control key whose control input through a control circuit consisting of flip-flops, an AND circuit, an OR circuit, and delay lines to the decoder outputs The residual of such a filter is limited frequency range due to the presence of a line in the circuit, 5 delays that do not automatically reorganize the filter when the boundary frequencies of the passband change, since when the passband changes, it is necessary to change the parameters of the delay line elements. In addition, the presence in the scheme of decoders, including bit bits, the number of which corresponds to

the counter discharge complicates the design of the filter.

Closest to the present invention is a filter comprising a differentiating chain, a strobe driver, and a filtering device. A strobe pulse shaper for such a filter is made on a double one-stable multivibrator, and a filtering device is provided with a three-input NAND gate 12}.

The disadvantages of the known filter are low noise immunity, i.e. filter along with the main pass band and has side bands, as well as bandwidth instability. This is because the filter is built on 3JteM6HTax, in which abilities are placed and the duration of the output pulses depends on the frequency of the input signal.

The purpose of the invention is to improve the premise resistance. 3. 3 The goal is achieved by the fact that in a discrete filter containing a strobe pulse shaping device, the first input of which is the synchronizing input of the filter, the first differentiating element whose input is the input of the filter and the first filtering unit whose output is the output of the filter , two square pulse drivers, two triggers, a second filter unit, a second differentiating element, and the output of the first differentiating element are connected to the inputs of the first and second straight drivers the first impulses of the first rectangular impulse generator are connected to the first inputs of the first and sropgiro triggers, the output of the second rectangular impulse generator is connected to the first inputs of the first and second filtering units; the inverse output of the first trigger is connected to the second inputs of the first and second filtering units and the second input forming a strobe pulses, the third vlode of which is combined with the third input of the second filter unit and connected to the inverse output of the second trigger, the second input of which connected to the first output of the strobe pulse former, the second output of which is connected to the second input of the first trigger, the direct output of which is connected to the input of the second differentiating element, the output of which is connected to the fourth input of the second filtering unit, the first output of which is connected to the third input of the first filtering unit, the fourth input of which is connected to the second output of the second filter unit. I And the first filter contains three elements And a capacitor, the output of which is connected to the nepauiny input of the first element And, the second input of which is connected to the output of the second element And, the first input of which is directly to the output of the third element And, the first and second inputs of which are respectively, the first and second inputs of the first filtration filter, and the second input of the second element And the capacitor are respectively the third and fourth inputs of the first filter unit, the output of the first element And is the output of the first fil block available. 6 In addition, the second filtering block contains the element AND-NOT, the element OR-NOT, the trigger and the differentiating element, the output of which is connected to the first inputs of the trigger and the element OR-NOT, the second input of which is connected to the output of the element AND-NOT, the first and second the input of which is respectively the first and third inputs of the second filtering unit, the output of the OR element is NOT connected to the second input of the trigger, the direct and inverse outputs of which are the first and second outputs of the second filtering unit, respectively, and the input differentiating the element and the third input of the element OR-NOT are respectively the second and fourth inputs of the second filter unit. FIG. 1 shows the scheme of the proposed discrete filter; in fig. 2 - timing diagrams for filter operation. The discrete filter contains a differentiating element 1, shapers 2 and 3 sequences of rectangular pulses shifted by half a period, a shaper-pulses shaper 4 and two triggers 5 and 6, the first and second filtering blocks 7 and 8, and elements 9-11. element AND-NO 12, element OR-NOT 13 trigger k, capacitor 15 differentiating element 16, the second differentiating element 17 Filter works as follows. The input of the filter is a sequence of rectangular pulses. Element 1 is used to select the leading and trailing edges with which the formers 2 and 3 are triggered. At the output of the formers 2 and 3, two sequences of pulses are received: synchronizing (F (t)) and polling () J shifted by half a period, the frequency of which is equal to the frequency input signal. Sequence 1 (.tj is fed to the inputs of triggers 5 and, 6 for receiving shot pulses synchronous with the input pulse. Triggers 5 and 6 form strobe voltages of low and high frequencies, respectively. Formed by triggered 5 and 6 voltages control the gate shaper pulses. The beginning of the formation of both strobe pulses coincides with the origin of the first pulse of the synchronization sequence F (tj, and the end of the formation coincides with the pulse appearing at the corresponding output of the strobe pulse former. Output one pulse of the driver k and a reset 5 triggers 5 and 6 and close it. In the closed state, the driver of the strobe pulses is until the next pulse of the synchronization sequence F (t) arrives. The strobe pulses (Fig. 2q) of the lower and upper 4acfoT ( Fig. 2 defines the filter bandwidth, the low-frequency strobe pulses determine the lower cutoff edge of the filter, and the strobe 15frequency pulses the upper cutoff edge of the filter. The selectivity of the filter in a given frequency band is ensured by the fact that the synchronizing pulses F (t) 20 of the strobe pulse former and the polling pulses are shifted relative to each other by a half period. As a result, the polling pulses that lie in the passband of the filter coincide in time with the low-frequency gate-pulses (Fig. 20) and do not coincide with the high-frequency gate-pulses (Fig. 2f,). Strobe pulses of the lower frequencies are fed to the element of SO 9 and trigger1A through the TB element, and the strobe pulses of the upper frequencies to the IS-NOT element 12. The second inputs of elements 9 and 12 receive the polling sequence F, (t) .35 state element 11 of block 7 is always open, and element 10 of block 7 is closed. As soon as a signal arrives at the input of the filter, strobe pulses of the lower and upper 40 frequencies are generated. The leading edge of the low-frequency strobe pulses overturns the trigger 14, as a result of which the permitting voltage is released to the second input of the element 10, and the element 10 opens i. This voltage does not pass on the element P, since it is prohibiting. ; the input element 11 is closed by a capacitor 15. Pulse sequence) polls the elements And 9 and I. NOT 12. If the input signal lies in the passband of the filter, it coincides with the low-frequency gate and does not coincide with the high-pass gate (Fig. 20, (D,). 55 As a result, if the signal is in the passband of the filter, the output 9. A pulse sequence appears that goes to element 66 and 10, so this element 10 is open, the impulse colv sequence goes to element 11 and then to the output of the filter. There is no signal at the output of element 12. If the input signal lies beyond the passband, then the pulse interrogation sequence a) or coincides with the strobe pulses of lower and upper frequency f or coincides with it. The first case is characteristic of frequencies lying above the upper cut-off frequency of the filter. The second case is characteristic of frequencies that lie below the low cut-off frequency of the filter. In the second case, since the interrogation sequence does not match either the high or low strobe pulses, there is no signal at the output of the filter. If the pulse sequence F4.Ct) coincides with the strobe pulses of the high and low frequencies, then a signal appears at the output of the AND 9 element, since the sequence of polling pulses coincides with the low frequency strobe. At the same time, since the sequence of polling pulses coincides with the high-frequency gate, at the inverse output of element 12 a sequence of negative pulses appears, the leading edge of which resets trigger 14, previously tilted by the leading edge of low-frequency gate pulses (Fig. 27) . As a result, element 10 of block 7 is closed, prohibiting the passage of a sequence of polling pulses Fi (t) to the output of the filter. However, when polling the filtering sequence of pulses F, 2 (t), the frequency of which follows the filter bandwidth, due to the different duration of low-frequency gates and high-frequency gates, there may be cases when pulses at the output of the AND-NE element 12 appear less frequently than pulses at the output of the element AND 9- This leads to the fact that at the output of the element And 10 there are parasitic pulses. The parasitic pulses of the element And 10 interrogate the element 11, which does not transmit parasitic pulses, since at this time it is closed by negative pulses coming from the inverse output of the trigger 14 (Fig. 2k). Thus, block 7 is closed either by element 10 and element 11 (fig. 2u., K.).

At the same time, negative blocking pulses on the element 11 are supplied through the capacitor 15. If the capacitor 15 removes the filter output, it will always be closed.

In the operation of the filter, it is possible that the leading edge of the low-frequency strobe pulses and the trigger flush pulses coincide, which leads to the appearance of pulses at both trigger inputs. This leads to unstable operation of the trigger I. For stable operation of the control trigger regardless of the input signal frequency and to ensure analysis of the input signal over the entire duration of the lower strobe, the three-input element OR NOT 13 is put into the exclusion mode of trigger pulses when they coincide with the front and back edges of strobe pulses of lower frequencies.

At the output of the OR-NOT 13 element, a single pulse of pulses appears, resetting the trigger only when all three inputs have a zero level, in all other cases the output of the OR-NOT element is 13. The first input of the OR-NOT 13 element receives a sequence of negative pulses from the inverting output of the element 12. To the second input of the OR-NOT 13 element through the differentiating element, the leading edge of the low-frequency strobe-pulse falls, to the third input - the rear of this pulse also through the differentiating element.

In the initial state, when the input signal is in the passband of the filter, the output level of the AND-NOT 12 unit is one level, and the output of the OR-NOT 13 element is zero. If the frequency of the input signal is higher than the upper cutoff frequency of the filter, then the state of the NAND 12 element changes, and at its output appears a sequence of pulses (zero level), which goes to the first input of the OR OR NOT 13 element and, in the case of the absence at the other two inputs of positive pulses (zero level) is inverted and passed to the output. The pulses arrive at the reset of trigger k and reset it. In cases when a negative pulse acts on the third input of the element OR NOT 13, and on one of the remaining inputs a positive pulse coincides with the front or rear

front of the lower frequencies, which corresponds to a single level at this input, the element ISH-HE 13 does not open and the trigger does not reset. Thus, failures in the operation of trigger I are eliminated and the filter is operated in a given bandwidth.

Thus, the introduction of two filtering blocks, the first of which contains three AND elements in series, and the second, AND – IE, OR – NE elements and a trigger and the introduction of two formers of square pulses and two triggers ensure the formation of strobe pulses , synchronous with the input signal and analysis of the input signal over the entire duration of the strobe, which allows only the signals in the passband to pass to the output of the filter and prohibit the appearance of spurious signals at the output, tvie thereby improving noise immunity of the filter.

Invention Formula

1. A discrete filter containing a strobe pulse shaper, the first input of which is the synchronizing input of the filter, the first differentiating element, the input of which is the input of the filter, and the first filtering unit whose output is the output of the filter, characterized in that increase of noise immunity; two Rectangular Pulse Formers, two triggers, a second filter unit, a second differentiating element, the output of the first differentiating element connected to the inputs of the first and the second square pulse shaper, the output of the first square pulse shaper is connected to the first inputs of the first and second flip-flops, the output of the second square pulse shaper is connected to the first inputs of the first and second filtering blocks; the inverse output of the first trigger is connected to the second inputs of the first and second filter blocks blocks and the second input of the strobe pulse generator, the third input of which is combined with the third input of the second filtering unit and connected to the inverse output v a second trigger, the second input of which is connected to the first output of the strobe pulse former, the second output of which is connected to the second input of the first trigger, the direct output of the KOTOpo is connected to the second input of the second differentiating element, the output of which is connected to the fourth input of the second filter unit, the first output which is connected to the third input of the first filtering unit, the fourth input of which is connected to the second output of the second filtering unit. 2. The filter according to claim 1, wherein the first filter unit contains three elements And a capacitor, the output of which is connected to the first input of the first element And, the second input of which is connected to the output of the second element And the first input of which is connected to the output of the third element AND, the first and second inputs of which are respectively the first and second inputs of the first filter unit, and the second input of the second element AND and the capacitor are respectively the third and fourth inputs of the first filter unit, the output of the first email And 10 is the output of the first filtering block. Distinguish 3- The filter of claim 1, about the fact that the second fi-blocking unit contains an AND-NES element, an OR-NOT element. trigger and differentiating element, the output of which is connected to the first inputs of the trigger and the OR-NOT element, the second input of which is connected to the output of the AND-NOT element, the first and second inputs of which are respectively the first and third inputs of the second filtering block output of the OR-NOT element to the second input of the trigger, the direct and inverse outputs of which are respectively the first and second outputs of the second filter unit, and the input of the differentiating element and the third input of the OR element are NOT respectively the second and The Fourth inputs of the second filtering unit. Sources of information taken into account during the examination 1. USSR author's certificate H- 365799, cl. H 03 H 7/02, 1973. 2. Digital variable bandwidth filter on two integrated circuits. Electronics, No. A, T. W, 1973 (prototype).

"V

N

B

Claims (3)

Claim 1. A discrete filter containing a strobe driver, the first input of which is the clock input of the filter, the first differentiating element, the input of which is the input of the filter, and the first filter unit, the output of which is the output of the filter, characterized in that, in order to increase the noise immunity , it introduced two formers of rectangular pulses, two triggers, a second filter unit, a second differentiating element, and the output of the first differentiating element is connected to the inputs of the first and W of the second shaper of rectangular pulses, the output of the first shaper of rectangular pulses is connected to the first inputs of the first and second triggers, the output of the second shaper of rectangular pulses is connected to the first inputs of the first and second filter blocks, the inverse output of the first trigger is connected to the second inputs of the first and second filter blocks and the second input pulse gate driver, the third input of which is combined with the third input of the second filter unit and is connected to the inverse 9 to the output of the second trigger, the second input of which is connected to the first output of the strobe generator, the second output of which is connected to the second input of the first trigger, the direct output of which is connected to the input of the second differentiating element, the output of which is connected to the fourth input of the second filter unit, the first output of which is connected to the third input of the first filter unit, the fourth input of which is connected to the second output of the second filter unit, I 2. Filter pop. 1, with the fact that the first filtering unit contains three elements And and a capacitor, the output of which is connected to the first input of the first element And, the second input of which is connected to the output of the second element And, the first input of which is connected to the output of the third AND element, the first and second inputs of which are the first and second inputs of the first filtering unit, respectively, and the second input of the second And element and the capacitor are the third and • fourth inputs of the first filtering unit, the output of the first And element IS 942246 10 is the output of the first filter unit. 3. Filter pop. 1, with the fact that the second filtering unit contains an AND-NOT element, an OR-NOT element, a trigger and a differentiating element, the output of which is connected to the first inputs of the trigger and an OR-NOT element, the second input which is connected to the output of the AND-HE element, the first and second inputs of which are the first and third inputs of the second filter unit _, respectively; the output of the OR-HE element is connected to the second input of the trigger, the direct and inverse * outputs of which are the first and second outputs of the second filter unit, respectively , and the input diff tsiruyuschego ren-element and the third element input NOR are respectively the second and fourth inputs of the second filtering unit.