SU1584079A1 - Follow-up filter for discrete frequency-manipulated signals with uninterrupted phase - Google Patents

Abstract

The invention relates to radio engineering and can be used in specific radar systems and radio navigation. The aim of the invention is to increase the selectivity and accuracy of symbol frequency estimates. The following filter contains frequency doubler 1, mixers 2, 3, 6, and 7, narrow-band filters 4 and 5, band-pass filters 8 and 9, dividers 10, 11, and 12 frequencies into two. Switching on the outputs of mixers 2 and 3 of narrowband filters 4 and 5 improves the frequency selectivity and threshold properties by passing only δ-bursts from the entire spectrum of the signal located at symbol frequencies "1" and "0". As heterodyning voltages, the mixers 2 and 6 of the symbol frequency channel "1" are supplied from the output of the bandpass filter 9 of the channel of the symbol frequency "0", and the mixers 3 and 7 channels of the symbol frequency "0" are supplied from the output of the bandpass filter 8. Twice frequency conversion with signal filtering by narrowband filters 4 and 5 at a clock frequency in each channel during cross-linking, and also using the properties of mixers 6 and 7 in combination with output filters 8 and 9 allows to form Nij module their difference and permits to increase the selectivity and accuracy of the symbol frequency estimate. 2 Il.

Description

1

The invention relates to radio engineering and can be used in coherent radar systems, radio navigation, communications for the selection of the symbol frequencies 1 and O of discrete frequency-manipulated signals with a continuous phase (DFMNF).

The purpose of the invention is to increase the selectivity and accuracy of the estimation of arbitrary frequencies.

FIG. 1 shows a flowchart of the next filter; 1 in FIG. 2 - spectrum of a discrete frequency-manipulated signal with a continuous phase passing through a frequency doubler.

The following filter contains frequency doubler 1, the first 2, the second 3 mixers, the first 4 and second 5 narrow-band filters, the third 6, the fourth 7 mixers, the first 8, the second 9 band filters, the first 10, the second 11 and the third 12 frequency dividers by two.

The following filter works as follows.

The input FMNF signal with a manipulation index, 5, is fed to the doubler 1 frequency input, which converts the spectrum of the signal. As a result, two spikes are produced in the spectrum (Fig. 2):

2,

G (2o /) GM (2uJ) + | - dkw- w,) 2 + JV- we) "

where C (21))) - 2 (;) 2 + cos2 (aM -) (c3b7

The first mixer 2, the first band-pass filter 4, the third mixer 6, the first band-pass filter 8 and the first, divider 10 form a channel 1 for estimating the symbol frequency Ј1 (Fig. 2), and the second mixer 3, the second narrow-band filter 5, the fourth mixer 7 , the second band-pass filter 9 and the second divider 11 form the channel O of the symbol frequency estimate Ј7, with F.,. Ј, -Ј „, the first 4 and second 5 narrow-band filters are tuned to frequency 2, the first band-pass filter 8 is tuned to frequency 2Fr, and second polo

Q

five

0

five

0

five

0

five

Jq

Owl filter 9 is tuned to frequency 2f,.

From the output of doubler 1, the signal simultaneously arrives at the inputs of the first 2 and second 3 mixers, the output of which includes the first 4 and second 5 narrowband filters 4 and 5, which improve the frequency selectivity and threshold properties due to passing only a signal from the whole spectrum located on the symbolic frequencies 1 and O (figure 2).

From the outputs of the narrow-band filters, the noise components selected from the noise spectrum at the clock frequency (FT) are fed to the inputs of the third 6 and fourth 7 mixers. They restore the symbol frequency of the signal, which is supplied to the inputs of the first mixers.

From the outputs of the third 6 and fourth 7 mixers, the signals arrive at the first 8 and second 9 bandpass filters with a passband of df, (+

+ Fa in channel 1 and 4f v 2l fe +

(KC „nl, V9 ° °

+ F-) in the channel O. max

As heterodyning voltages, the first 2 and third 6 mixers of channel 1 are supplied with voltage from the output of the second bandpass filter 9 of channel O, and the second 3 and fourth 7 mixers of channel O are supplied with voltage from the output of bandpass filter 8 of channel 1.

In the tracking mode for varying the frequency of the input signal, the symbol and clock frequencies with varying increments (due to the Doppler shift) are doubled in the input doubler. In the first mixer 2 of channel 1, the symbol frequency is converted

2Јf / 1 + F5, (t) - fe + Fao (2 (Fr + + uFd (t)}, where 4Fg (t) F5 (t) -Fae (t) Fr + F3 (t).

In the third mixer 6, the symbol frequency 1 of the filtered signal is restored:

2 FlT-fdF3 (t) + fe + F3 (t) +

+ F

h, (t)).

, with the signal-to-noise ratio increasing

AG

LЈ

h / lr

again .. then in the first

divider 10 frequency is divided in two to obtain an estimated value. As a result, a continuous oscillation with a frequency of Ј, + Gd (t) is formed at the output of channel 1.

In the second mixer 3 channels O, the signal frequency of the symbols is converted.

2ff1 + Fai (t) - fe + Fje t) J} -2 $ FT + (t)).

In the fourth mixer 7 of channel O, the frequency doubled

2 {Ј1 + F, i (t) - FT + 4F $ (t) +

+ F, (t) j. ° t

with a signal / noise ratio, as in channel 1.

The second divider 11 forms an estimate of the current value of the symbol frequency O, i.e. ).

The third divider 12 from the doubled value of the filtered clock signal forms an estimate of the current value of the clock frequency Fr + 4F (t) also with a gain in the signal-to-noise ratio, as in channel 1.

Thus, the introduction of a double frequency conversion with filtering the signal with UE band filters at the clock frequency in each channel during cross-linking and also using the properties of the mixer in combination with the output filter to form the difference between two oscillations

five

0

50

effectiveness and accuracy of symbol frequency estimation.

Claims (1)

So, at frequencies of about 340 ° Hz, the gain in the signal-to-noise ratio reaches 30-40 dB, the theoretical limit is about 46 dB. Invention Formula A continuous filter of discrete frequency-manipulated signals with a continuous phase containing a frequency doubler, the output of which is connected to the channel inputs of the symbol frequencies O and 1, made in the form of serially connected filter and frequency divider into two, the outputs of which are respectively the frequency O and the output of the symbol frequency 1, and the frequency doubler input is the input of the tracking filter of discrete frequency-manipulated signals with a continuous phase, characterized in that, in order to increase the beat performance and accuracy of the evaluation of symbolic frequencies, introduced the third frequency divider into two, and the filters are made in the form of serially connected first mixer, narrowband filter, second mixer and first bandpass filter, the input of the third frequency divider is connected to the output of the narrowband filter channel symbol O, and its output is a clock frequency output, and the second inputs of the first and second mixers of each of the channels of symbol frequencies O and 1 are connected to the output of a bandpass filter of the other channel. t 6 (2fc # (2Ji) 2Jo 2icp 2G FIG. 2 Editor M. Bpanar Compiled 10. Chernyshev Tehred L. Serdyukova Proofreader A. Osaulenko Order 2263 Circulation 6b VNIIPI of the State Committee on Inventions and Discoveries at the State Committee on Science and Technology CC.SR 113035, Moscow, Zh-35, 4/5 Raushsk Nab. Subscription