RU92584U1 - DIGITAL SIGNALS FORMER WITH MINIMUM FREQUENCY SHIFT - Google Patents

Abstract

A digital signal generator with a minimum frequency shift, containing an analog-to-digital speech converter (ADC), a Gaussian filter, a time integrator, two signal multipliers, a carrier frequency oscillator, a 90º phase shifter, a first adder, and an output is connected to one input of the first adder the first multiplier, and the output of the second signal multiplier is connected to its second input; the carrier frequency oscillation generator is connected to the high-frequency (r.h.) input of the first signal multiplier directly and to the r.h. the input of the second multiplier - through a 90º phase shifter, characterized in that it additionally introduces a time differential, a phase inverter, a second adder, two signal multipliers, two signal amplitude limiters, two coherent detectors, an auxiliary carrier frequency generator, a delay unit for time, signal level regulator, and the ADC output is connected to the low the input of the first signal multiplier through a series-connected Gaussian filter, the third signal multiplier, the first amplifier-limiter of the signal amplitude, the first coherent detector, a time delay unit, and the output of the Gaussian filter is connected to the low frequency the input of the second signal multiplier through a series-connected signal integrator in time, a second adder, a fourth signal multiplier, a second signal amplitude amplifier limiter, a second coherent detector, a signal level controller; the integrator input is connected to the second input of the second adder through series-connected signal differentiator during

Description

The utility model (PM) relates to the field of digital signal transmission.

Known digital signal shapers with a minimum frequency shift and preliminary Gaussian filtering (GMES), which are used in mobile radio communications (GSM) systems and are described in the literature, for example, in:

1. Gromakov Yu.A. Standards and systems for mobile radio communications. - M.: Eco-Trends, 1998 .-- S.115-118.

2. Makoveeva M.M., Shinakov Yu.S. Communication systems with moving objects. - M .: Radio and communications, 2002. - S.114-116.

3. Volkov A.A. Radio transmitting devices. - M .: Route, 2002. - P.283 - 284.

By technical nature, the closest to PM is the shaper described in the first source, which for this reason is taken as its prototype. Other sources describe PM analogues.

The prototype consists of an analog-to-digital converter (ADC) for speech, a Gaussian filter, a signal integrator in time, two cosine and sine blocks for their input signals, two signal multipliers, a carrier frequency oscillator, a 90-degree phase shifter, and an adder, in addition connected to one input of the adder through a series-connected Gaussian filter, integrator, block cosine formation, the first signal multiplier, and the output of the integrator is connected to its other input through in series with a single sine shaping unit and a second signal multiplier; the output of the carrier frequency oscillation generator is connected directly to the second input of the first signal multiplier and to the second input of the second signal multiplier through a 90 degree phase shifter.

This shaper is a frequency modulator with a frequency shift close to zero, which makes the frequency band of the signal at its output almost equal to the doubled frequency band of the signal from the output of the Gaussian filter, which according to C.87 [1] is 81.2 kHz, and the output of the shaper it is 200 kHz, which is more than 2 × 81.2 = 162.4 kHz. Such a frequency band is not always acceptable for practice.

The main disadvantage of the prototype is the wide frequency band of the signal at its output, i.e. its low frequency efficiency.

The technical result of PM is to reduce the frequency band of the output signal of the prototype by more than 2 times without affecting the quality of speech.

The essence of the PM is that in the prototype, which consists of an ADC for speech, a Gaussian filter, an integrator, two blocks for generating cosine and sine by their input signals, a carrier frequency oscillator, a phase shifter 90 degrees, an adder, moreover, the ADC is connected to one input the adder through a series-connected Gaussian filter, integrator, cosine formation unit, the first signal multiplier, and its integrator output connected to its other input through a series-connected sine formation unit and a second alternator ozhitel signals; the output of the carrier frequency oscillation generator is connected directly to the second input of the first signal multiplier and to the second input of the second signal multiplier through a 90 degree phase shifter, an additional time differential, a phase inverter, a second adder, a third and fourth signal multiplier, and two amplifiers that limit the signal amplitude are introduced , two coherent detectors, an auxiliary carrier frequency generator, a time delay unit, a signal level regulator, moreover, the integrator output is connected en to n.ch. the input of the second signal multiplier through the second adder, the fourth signal multiplier, the second signal amplitude limiting amplifier, the second coherent detector, the second signal multiplier, connected in series; the integrator input is connected to the second input of the second adder through a series-connected signal differentiator in time and a phase inverter, the integrator output is also connected to the second input of the first adder through a series-connected fourth signal multiplier, a second signal amplitude limiting amplifier, a second coherent detector, a signal level regulator, a second signal multiplier; the output of the Gaussian filter is also connected to the low the input of the first signal multiplier through a series-connected third signal multiplier, a first signal amplitude amplifier limiter, a first coherent detector, a time delay unit; the output of the auxiliary carrier frequency generator is connected to the RF the inputs of the third and fourth signal multipliers, as well as to the second inputs of both coherent detectors.

A significant difference between PM is the introduced elements and their relationships, because only they can reduce the frequency band of the output signal by more than 2 times without compromising speech quality.

The utility model is illustrated by drawings.

In Fig.1 shows a structural diagram of a signal conditioner with GMP, and in Fig.2 - amplitude-frequency characteristics (AFC) of the envelopes of signals that explain its operation.

In figure 1 is indicated:

1 - analog-to-digital Converter (ADC);

2 - signal differentiator in time;

3 - time signal integrator;

4 - Gaussian filter;

5 - phase inverter;

6, 20 - adders;

7, 9, 16, 19 - signal multipliers;

8 - oscillation generator auxiliary carrier frequency;

10, 11 - amplifiers - signal limiters;

12, 13 - coherent detectors;

14 - block delay time;

15 - signal level regulator;

17 - generator oscillation of the carrier frequency;

18 - phase shifter signal 90 degrees.

Entered elements are outlined with a dashed line. The operation of the circuit is as follows.

A digital signal (DS) from block 1 is fed to the first input of adder 20 through a series-connected Gaussian filter (GF) 4, a third signal multiplier 7, a first amplifier — a signal amplitude limiter 10, a first coherent detector 12, a time delay unit 14, and a first multiplier 16 signals.

A Gaussian filter 4, having a bell-shaped amplitude-frequency characteristic (AFC), eliminates the higher harmonics of the CS, starting from the second harmonic, so that a continuous oscillation takes place at its output, which is practically the first harmonic of the CS. According to the theory of the analytical signal, this oscillation can be represented in quasiharmonic form as u (t) = U (t) cosφ (t), where U (t) is the envelope and φ (t) is the phase. To simplify the notation, we assume that φ (t) = Ωt, where the circular frequency Ω = dφ / dt. The signal from the GF u ₄ (t) = U (t) · cosφ (t), which is broadband, is fed to the low-frequency (n.h.) input of the third signal multiplier 7, to the high-frequency (n.h.) input of which the auxiliary carrier oscillates frequency u ₈ (t) = U ₈ coswt from generator 8. At the output of block 7, the oscillation u ₇ (t) = u ₄ (t) * u ₈ (t) = 0.5U (t) U ₈ * [cos (w + Ω) t + cos (w-Ω) t] is balanced-modulated, narrow-band, which is fed to the input of the first amplifier-limiter 10 of its amplitude. At the output of block 10, the amplitude u ₁₀ (t) oscillation deep in amplitude consists of the first harmonic and higher (including) harmonics, which is fed to the signal input of the first coherent detector 12, to the reference input of which the auxiliary carrier frequency oscillation u ₈ ( t) from the generator 8. The coherent detector consists of a signal multiplier and a low-pass filter at its output. At the output of the multiplier of block 12, the oscillation is u ₁₂ (t) = u ₁₀ (t) * u ₈ (t) = U ₁₀ {[cos (w + Ω) t + cos (w-Ω) t] + exc. * U ₈ coswt = U ₁₀ * U ₈ cosvt + h The low-pass filter only allows low frequencies to reach its output. signal and does not pass the r.h. components. The signal u ₁₂ (t) arrives through the time delay unit 14 on the low input of the first multiplier of 16 signals, including the input of which is supplied from the generator 17, the oscillation of the carrier frequency u17 (t) coswt directly. At the output of block 16, the oscillation is u ₁₆ (t) = u ₁₄ (t) * u ₁₇ (t) = U ₁₄ cosΩt * U ₁₇ cosw ₀ t = 0.5U ₁₄ * U ₁₇ [cos (w ₀ + Ω) t + cos (w ₀ -Ω) t], which is fed to the first input of the first adder 20.

The signal from GF 4 is also fed to the second input of the first adder 20 through sequentially connected integrator 3, the second adder 6, the fourth signal multiplier 9, the second amplifier-limiter 11, the second coherent detector 13, the signal level regulator 15, the second signal multiplier 19. The integrator input 3 is connected to the second input of the second adder 6 through a series-connected differentiator 2 and a phase inverter 5. At the output of the integrator 3 oscillation , and at the output of differentiator 2, the oscillation u ₂ (t) = du ₄ (t) / dt = -ΩU (t) sinΩt = -ΩU (t) cos (Ωt-90 °), which through phase inverter 5 changes sign from the minus plus, it goes to the second input of the second adder 6. During integration and differentiation, the envelope U (t) is assumed to be constant, since it changes in time many times more slowly than cosΩt. It can be seen that the oscillations at the inputs of the second adder 6 are 90 degrees out of phase with respect to the signal from GF 4, having a different law of amplitude change from frequency: at one input it is directly proportional to the frequency Ω, and the other is inversely proportional to Ω, as shown in FIG. 2. At the output of the adder 6 oscillation u ₆ (t) = u ₃ (t) + u ₅ (t) = (1 / Ω + Ω) U (t ) cos (Ωt- 90) is also shifted phase by 90 degrees with respect to u ₄ (t), has an envelope (1 / Ω + Ω) U (t) that is not equal to zero at any frequency Ω, although its level depends on this frequency (Fig. 2). This means that the 90-degree phase shifter, consisting of blocks 2, 3, 5, 6, does not limit the frequency band either from below or from above. Only such a phase shifter provides a 90 degree phase shift with an error of less than 1 degree to a digital signal that has passed through GF 4 and has a frequency bandwidth of 0 to 81.2 kHz at its output. To equalize the amplitude of the signal u ₆ (t) at all frequencies, it is amplified and deeply limited in level. In order to avoid nonlinear distortions from this due to the harmonics of its n.h. entering the frequency band of the signal u ₆ (t) making up this broadband signal is converted to narrowband by balanced modulation. For this, the signal u ₆ (t) is supplied to the N.H. input of the third signal multiplier 9, on vh the input of which is the oscillation of the auxiliary carrier frequency u ₈ (t) from the generator 8. At the output of block 9, the oscillation is u ₉ (t) = u ₆ (t) * u ₈ (t) = 0.5 (1 / Ω + Ω) U (t) U ₈ {cos [(w + Ω) t-90] + cos [(w-Ω) t + 90]}. Next, the narrow-band oscillation u ₉ (t) is amplified and deeply limited in amplitude in block 11, which is why the first harmonic of the input signal of a constant level and higher (including) harmonics occur at its output. From the output of block 11, the oscillation u ₁₁ (t) is fed to one input of the second coherent detector 13, the other input of which is supplied to the oscillation of the auxiliary carrier frequency from the generator 8. The coherent detector consists of a multiplier and a low-pass filter at its output. At the output of the multiplier of block 13, the oscillation u ₁₃ (t) = u ₁₁ (t) * u ₈ (t) = U ₁₁ {cos [(w ₀ + Ω) t-90] + cos [(w ₀ + Ω) t + 90] + v.ch.} * U ₈ cos w ₀ t = U * U _{11 8} cos (Ωt-90) + v.ch. The low-pass filter of block 13 allows only low frequencies to pass to its output. component, and v.ch - does not pass. The signal from block 13 enters through the level regulator 15 at t.h. the input of the second signal multiplier 19, to the high-frequency input of which the carrier frequency oscillates from the generator 17 through the phase shifter by 90 degrees 18. At the output of block 19, the oscillation is u ₁₉ (t) = u ₁₅ (t) * u ₁₈ (t) = U ₁₅ cos (Ωt-90) * U ₁₈ cos (w ₀ t + 90) = 0.5U ₁₅ U ₁₈ [cos (w ₀ + Ω) t-cos (w ₀ -Ω) t], which is fed to the second input the adder 20. With the help of the regulator 15 levels are aligned N.H. signals at the inputs of the multipliers, which is why 0.5U ₁₅ U ₁₈ = 0.5U ₁₄ U ₁₇ with U ₁₇ = U ₁₈ . Therefore, at the output of adder 20, the oscillation is u ₂₀ (t) = u ₁₆ (t) + u ₁₉ (t) = U ₂₀ cos (w ₀ + Ω) t. This is an oscillation of one side frequency band (OBP), in this case, the upper one (VBP), the frequency band of which is equal to the signal bandwidth at the output of GF 4, equal to 81.2 kHz. To obtain the lower sideband (NBP) u ₂₀ (t) = U ₂₀ cos (w ₀ -Ω) t, it is necessary to interchange blocks 2 and 3 or introduce an additional phase inverter between blocks 19 and 20.

The technical and economic effect of the utility model is to reduce the frequency band of the signal at the output of the shaper compared to the prototype 200 / 81.2 = 2.46 times without compromising the quality of the restored speech. This means that in a given frequency band of a radio channel, instead of one, two such digital channels can be arranged.

Claims (1)

A digital signal generator with a minimum frequency shift, containing an analog-to-digital speech converter (ADC), a Gaussian filter, a time integrator, two signal multipliers, a carrier frequency oscillator, a 90º phase shifter, a first adder, and an output is connected to one input of the first adder the first multiplier, and the output of the second signal multiplier is connected to its second input; the carrier frequency oscillation generator is connected to the high-frequency (r.h.) input of the first signal multiplier directly and to the r.h. the input of the second multiplier - through a 90º phase shifter, characterized in that a time differential, a phase inverter, a second adder, two signal multipliers, two signal amplitude limiting amplifiers, two coherent detectors, an auxiliary carrier frequency generator, a delay unit for time, signal level regulator, and the ADC output is connected to the low the input of the first signal multiplier through a series-connected Gaussian filter, the third signal multiplier, the first amplifier-limiter of the signal amplitude, the first coherent detector, a time delay unit, and the output of the Gaussian filter is connected to the low frequency the input of the second signal multiplier through a series-connected time signal integrator, a second adder, a fourth signal multiplier, a second signal amplitude amplifier limiter, a second coherent detector, a signal level regulator; the integrator input is connected to the second input of the second adder through sequentially connected signal differentiator in time and phase inverter; the output of the auxiliary carrier frequency generator is connected to the RF the inputs of the third and fourth signal multipliers, as well as to the second inputs of both coherent detectors.