RU2001526C1 - Generator of carrier frequency of phase-shift keyed signals - Google Patents

Abstract

Use in digital signal receiving devices in phase shift keyed communication systems to isolate the carrier frequency and synchronously detect the received signals SUMMARY OF THE INVENTION: the device comprises a mixer, a frequency multiplier, an intermediate frequency amplifier, an adaptive narrow-band filter, a comparator, a frequency divider, frequency converting units , the device provides simplification by eliminating the second mixer, the second frequency multiplier and the tunable generator and improving the dynamic Sgiach characteristics of the frequency tracking of the received signal. 1 ill.

Description

The invention relates to radio engineering and can be used in devices for the reception of digital signals about speech systems with phase shift keying to isolate the carrier frequency and synchronously detect the received signals.

The goal is to simplify the device by eliminating the second mixer, the second frequency multiplier and the tunable generator, and to improve the dynamic characteristics of tracking the frequency of the received signal.

The drawing shows a structural circuit diagram of a carrier frequency regenerator of a phase-shifted signal.

The carrier frequency regenerator of the phase-shifted signal comprises a mixer 1. a frequency multiplier 2, an intermediate frequency amplifier (IFA) 3, an adaptive narrow-band filter 4, a comparator 5, a frequency divider 6, the first and second frequency converting units 7, 8, an adaptive narrow-band filter 4 , which contains a narrow-band filter 4.1, amplifier 4.2. DC, phase detector 4.3.

The carrier frequency carrier of the phase-shift keyed signal operates as follows.

A phase-shifted signal is input to the device

W (t) -Asin OJol + 0 (l). (1)

where 0 (t) K (2 / M) for LT t (L + 1) T.

Here T is the duration of one character, M is the multiplicity of manipulation, and the parameter K, depending on the value of the character transmitted in the interval LT t (L + 1) T, can take the values K O, (M - 1).

Let us designate the frequency of the signal acting at the output of the adaptive filter 4 through (О, at the output of the 1st frequency-conversion unit 7 through hell. When a signal (1) is received at the input of the device, the signal will act on the mixer output

WCM (t) A -sin (m - MI) t + 0 (t). (2)

This signal is amplified in the amplifier 3 and is fed to the input of the frequency multiplier 2 by a factor of M, the output of which is a signal with a removed manipulation

Wy (t) A (aJoan.) T + M-0 (t) A (u - ofe): (because 0 (t) - M 2 l K) (3)

This signal is harmonic; it is allocated by adaptive narrowband

ABOUT

5

0 5

0

5

0

0

filter 4. It may contain a narrow-band filter 4.1 with a controlled tuning frequency. A control signal is generated at the output of a DC amplifier 4.2 (DC), the input of which is connected to the output of a phase detector 4.3, the first input of which is connected to the input of the filter, and the second to its output. As a result of the auto-tuning circuit, the filter 4.1 always turns out to be tuned to the frequency of the signal supplied to its input. Since signals of the same frequency are fed to the input of PD 4.3 regardless of the frequency of the signal acting at the input of the device, only a constant component is allocated at its output, and there is no beat frequency. This provides capture for the useful signal at any value of frequency instability of the received signal.

The amplification factor of the CTF must be large enough so that the phase difference of the signals at the input and output of the filter 4.1 is insignificant (5), and its passband is narrow enough to provide a small noise band of the self-tuning frequency loop of this filter,

In comparator 5, this signal is clipped and converted into a meander. Such a signal is convenient for digital processing of signal (3) in a frequency divider by frequency-converting blocks 7 and 8. In block 7, rational frequency conversion of (3) is carried out in h (m / n) times, where the type is mutually simple numbers.

As a result, a signal will act at the output of this block

W2 (t) A -sin (od, sch) l. (4)

which goes to the second input of the mixer 1.

Thus, the frequency of the signal supplied to the second input of the mixer 1 is equal to

hell --- (a) o- 0) 2), i.e.

) and

From (5) and (3) it follows that at the output a narrow-band filter 4, the signal frequency is

ol M (MO- Ш2) (

n M

n + m M

) th (6)

and at the output of mixer 1, a phase-manipulated signal with a frequency

P

mz o - shg (

p h - m m

) UA (7)

The signal acting at the output of the comparator 5 and having a frequency a is fed to the input of the 2nd frequency conversion unit 8 with a conversion coefficient

n-f m M.

l2 n M

As a result, a harmonic signal with a frequency equal to Gfc is generated at its output. This signal is coherent with the phase-shifted signal supplied to the device input and can be used as a reference signal in the demodulation block of the FM signal.

In addition, the signal from the output of the comparator 5 is fed to the input of the frequency divider 6, which divides the frequency of the input signal by M times. As a result, a harmonic signal is generated at its output with a frequency ω, coherent with the FM signal acting at the output of the IF amplifier 3. This harmonic signal can be used as a reference signal for demodulation of the FM signal acting at the output of the IF amplifier 3.

It should be noted that in the proposed device, in contrast to the known one, the only source of frequency instability of the signal supplied to the input of the narrow-band filter is the frequency instability of the received signal, while in the known device the frequency instability is the frequency instability of the tunable generator, the first Of these instabilities, less than the second. This, as well as the use in the proposed device adaptive narrow-band filter allows

It allows to obtain good dynamic characteristics of tracking the carrier frequency of the received signal.

As one example of the selection of the conversion parameters n and m in (4) - (7), we consider the case when an FM signal with M 4, f0 Oo / 1 l 4 GHz is received and suppose that the intermediate frequency is chosen so that

od / 2 l 35 MHz, i.e. (| §) «Л

Oh

5

0

Moreover, from (7) follows JL. 0 n9

-,9

those. (2- 1) ..

9

n +4 m 2b

Thus, choosing rn 25 -1ip 4, it is possible, using the proposed device, to create a receiver of FM signals with an intermediate frequency equal to fnp fo / 2. Moreover, as can be seen from (6), the instability of the frequency of the Sch signal at the input of the narrow-band filter is associated with the instability of the frequency of the useful signal

1

n7

D "1 / D% - -n

n 4 m

those. House instability is more than an order of magnitude lower than the instability of the frequency of the received signal. This circumstance significantly simplifies the implementation of a narrow-band filter in the carrier regenerator, since the adjustment of its center frequency should be carried out in very small limits.

(56) Japanese application N 1961, cl. 98 (5) E O. 1968.

Claims (1)

The claims A CARRIER FREQUENCY REGENERATOR OF A PHASOMOMPLIED SIGNAL, comprising a frequency multiplier and a mixer, the first input of which is an input of the device, characterized in that, in order to simplify the device by eliminating the second mixer, the second frequency multiplier and the tunable generator and improving the dynamic characteristics of tracking the frequency of the received signal, an adaptive narrow-band filter, a comparator, a frequency divider, the first and second frequency converting blocks and an intermediate frequency amplifier are introduced, the output of which is the first output 40 the regenerator and connected to the input of the frequency multiplier, the input of which is connected to the input of the adaptive narrow-band filter, the output of which is through a 45 key comparator to the inputs of the first and second frequency converter blocks and the input of the frequency divider, while the output of the first frequency converter block is connected to the second input mix 50 l, the output of which is connected to the input of an intermediate frequency amplifier, the outputs of the second frequency converting unit and frequency divider being the second and third, respectively 55 device outputs.