SU1179520A1 - Versions of device for non-recursive digital filtering - Google Patents

Abstract

1. A device for non-recursive 1-filtering, containing 11 series-connected delay elements, the input of the first and the output of each of which are connected to the input of the corresponding multiplier, and the outputs of the multipliers are connected to the corresponding inputs of the adder, the output of which is the code of the device, and the input of the device, which is different from the fact that, in order to extend the functionality by forming an additional filtering band in the high frequency region with a frequency characteristic acting as a symmetrical source, the adder is made in the form of an adder, the even component of the signal and an adder of the odd component of the signal, the outputs of which are connected to the inputs of the output adder, in addition, the device is connected in series with a sign inverter and an additional accumulator whose output is an additional output of the device , the output of the adder of the even components of the signal is connected to another input of the additional adder, and the output of the adder of the odd components of the signal is connected to the input of the sign inverter , the outputs of the even-numbered components of the signal are connected to the outputs of even-numbered multipliers, and to the inputs of the odd-numbered components of the signal are the outputs of odd-numbered multipliers. S 2. A recursive device (L digital filtering containing () connected in series with the delay elements, with the output of each

Description

At the same time, the output of the adder of the delay element is connected to the input of the inverter of the adders, and the output of the signal components is connected to the input components, and the outputs of the output and auxiliary multipliers are connected to the other components of the even components.

1179520

This invention relates to radio devices using digital signal processing.

The purpose of the invention is the expansion of functional capabilities by forming an additional filtering band in the high frequency domain with a frequency response that is symmetrical to the original,

FIG. 1 shows the first variant of the structural electrical circuit of the device; in fig. 2 - the second variant of the structural electrical circuit of the device; in fig. 3 - frequency characteristics of the device.

A device for non-recursive digital filtering (the first option) contains n elements 1,. . .,, delays, (and + 1) multipliers 2, ... ,, 2, adder 3, consisting of adder 4 even components of the signal, adder 5 odd components of the signal and output adder 6, inverter 7 characters and additional adder 8.

A device for non-recursive digital filtering (the second option) contains () elements 1,. . ., L delay, 2 multipliers 2, ..., 2 ,, adder 3, consisting of adder 4 even components of the signal and output adder 5, inverter 6 characters and additional adder 7 ..

The device for non-recursive digital filtering (FIG. 1) operates as follows.

Samples of the original digital signal AIM, which has the main frequency band from O to a certain cutoff frequency FK () and the clock frequency-. Toto F 2F, is fed to the input of series-connected elements 1, ..., delays, each of which carries a delay

counts per clock interval T 1 / F. The obtained samples from the input of the first element 1 | delays and outputs of elements 1,,. . , 1 ,, the delays are multiplied by constant coefficients b, b, b, ..., b with the help of multipliers 2,, 2у, and the product with the codes of multipliers with numbers 2i (where i; 0, 1, 2, .. ,, G 1 is summed in the adder 4 of even components of the signal, and the product of the outputs of the multipliers with numbers (where l O, 1, 2,. ,,, 2. |. Are summed in the adder 5 odd components of the signal. Signals from the outputs of the adder 4 even-numbered signal components and an adder 5 of the odd-numbered signal components are fed to an output adder 6, at the output of which a signal in the low-frequency (LF) region is received from the field axis, from O to F. From the output of the adder 4 even components of the signal directly, and from the output of the adder 5 the odd components of the signal through the inverter 7 characters go to the inputs of the additional adder 8, the output of which extracts the signal in the high-frequency (HF) region with a band from (Fg - F (i.) to Fg.

Consider the signal extraction algorithm,

Let X c denote the signal at the input of the device at the clock moment of the CG, and Woc and Y1, (.. - read the signals at the LF and HF codes of the device.

Obviously

YO bgXj, + b, X,., + B, X.2, + - 2I- "

ptOiYlK b, X ,, +, .-- ... (- i) bpx ,,,,:

where n is the number of delay elements.

We introduce the dimensionless frequency F / Fg. The complex transfer factor 3 at frequency d between the input of the device and the output of the adder 6 GO (b) 11 Lp - P - 0 and between the input of the device and the output of the additional adder .8 q, (d) .iHlXe - ". Ib .. Thus , G1 (С5) WITH (d + 1). However, with digital filtering, G (d) G (2 -d) takes place, where is the sign of complex conjugation, and therefore G1 (() GO (1 -d). The frequency response modules GO and G1 have the form shown in FIG. 3. From Fig. 3 it can be seen that if GO is a characteristic of the type of LF with a transition region, having a center at the point Fj, / Fg, then G1 is a characteristic of the type of HF with a center in the band 1 - (Fe - Fc) / Ff In digital filtering, the transition from a low-pass filter to an high-pass filter with the same width of the transition region reduces only to a change in the signs of the filter coefficients b, b J, ... with odd numbers, which is easy The device is greatly simplified in the particular case when the extracted low and high frequency signals have the same frequency bandwidth, i.e. FC Pb / 2, and (J, (Fig. 3), and A symmetrical digital filter with an absolute 04 but a linear phase response is used. In this case, all the filter coefficients b, b, b, ... with odd numbers are turned to 0. The second variant of the proposed device (Fig. 2) works in a similar way. At the output of the adder 5, which is the output of the low-frequency signal, the general expression of the output signal 4t-2, b, X, .p is simplified for two reasons: firstly, bp b, due to symmetry, secondly, all bjo, O due to the choice of the center of the transition region (Nyquist point) at b :, 1/2 (Fig. 3). So, not counting a constant delay of 2m-1 cycles t m (; - X) + Cf (X C2p + 0: p. O -up-n b (p 1, p gm-c 2p., T) Similarly, at the output of the additional adder 7 there is a count of the output signal hp 2 K (, Rc) - V- (2p- (). The frequency characteristics at the outputs of the adder 5 and the additional adder 8 are equal respectively to m. GO (and) 1 + 2 Cpcos f (j (2p-t), G1 () 1 - 2 C..cos7d (2p1 1) Both characteristics are real, like G0 (e) + G1 (d) 2, which corresponds to the appearance of the graphs on games 3.

Claims (2)

1. A device for non-recursive digital filtering, containing AND series-connected delay elements, the input of the first and the output of each of which is connected to the input of the corresponding multiplier, and the outputs of the multipliers are connected to the corresponding inputs of the adder, the output of which is the output of the device, and the input of the first delay element is the input device, characterized in that, in order to expand functionality by forming an additional filtering band in the high frequency region with a frequency characteristic With a symmetric source, the adder is made in the form of an adder of even signal components and an adder of odd signal components, the outputs of which are connected to the inputs of the output adder, in addition, a sign inverter and an additional adder are connected in series, the output of which is an additional output devices, while the output of the adder of the even signal components is connected to another input of the additional adder, and the output of the adder of the odd signal components is connected to the input of the sign inverter, and to the input am adder even components of the signal outputs of the multipliers are connected to the even-numbered and odd adder inputs to the signal component - the multipliers outputs with odd numbers. 2. A device for recursive digital filtering, containing (4π2) series-connected delay elements, the output of each (2k) -th delay element (where k-0 1, 2, ..., 2m-0 and the input of the first delay element are connected through the corresponding multiplier, and the output of the (2sch-1) -th delay element is directly connected to the inputs of the adder, the output of which is the output of the device, characterized in that, in order to expand the functionality by forming an additional filtering band in the high-frequency region with frequencies nd characteristic symmetrical initial adder is designed as a series-connected component of the even adder signal and the output of the adder, in addition, a device connected in series incorporated sign inverter and an additional adder, the output of which is an additional outlet Device for. In this case, the output of the even adder of the signal component is connected to the input of the sign inverter, and the output of the (2 / n-1) -th delay element is connected to the other inputs of the output and additional adders, and the outputs of the multipliers are connected to the inputs of the adder of the even components of the signal.