Headquarters and parameters of radio signals. You see the signals that you can use in radio communication systems

1. Classification of modulation types, basic characteristics of radio signals.

To enable the radio communication, it is necessary to change one of the parameters of the radio frequency communication, called unacceptable, according to the rank of the radio frequency communication, which is considered to be a low-frequency signal to be transmitted. Tse reach for the additional modulation of the radio frequency communication.

Vidomo, shho harmony kolyvannya

characterized by three, independent parameters: amplitude, frequency, and phase.

There are three main types of modulations that can be differentiated:

Ampl_tudna,

Frequency,

Fazova.

Amplitude modulation (AM) is the name given to such a type of flow on a bunch of noise, as a result of which the amplitude changes according to the law to the signal that is transmitted (to the module).

Vazhaєmo, the modulo signal can be seen by the harmonic signal from the frequency W

very low frequency of a non-bunch of w.

As a result of the modulation, the amplitude of the stress of the non-load bearing is responsible for the change proportionally to the stress of the modulating signal uW (Fig. 1):

UAM = U + kUWcosWt = U + DUcosWt, (1)

de U - the amplitude of the spill of a non-carrier radio-frequency kolivannya;

DU = kUW - increase in amplitude.

Rivnyannya amplitude-modular kolivan

UAM = UAM coswt = (U + DUcosWt) coswt = U (1 + cosWt) coswt. (2)

Behind this very law is the iAM strum during modulation.

The value that characterizes the change in the amplitude and the amount of DU to the maximum amplitude without modulation U is called the modulation factor (glybin)

For the third time, the maximum amplitude is Umax = U + DU = U (1 + m) and the minimum amplitude is Umin = U (1-m).

Yak nevazhko bachiti z rivnyannya (2)

UAM = U (1+ mcosWt) coswt = Ucoswt U / 2 + cos (w - W) t U / 2 + cos (w + W) t. (4)

The first dodanok is a transmission without modulation (moving mode). Others - the number of high frequencies.

If the modulation goes by the foldable low-frequency signal from the spectrum Fmin to Fmax, then the spectrum of the trimmed AM signal to the viewer, images in Fig. Zayman AM - with a signal of a smog of frequencies Δfс not to lie down from m і roads

Δfс = 2Fmax. (5)

Winning the number of low frequencies during modulation to make it necessary to expand the smog to pass the transmission circuits (and according to the reception). Vaughn is guilty of bootie

de Q - quality factor of contours,

Df - absolutely rozlad,

Dfk - smog through the circuit.

In fig. spectral warehouses, which show lower modulus frequencies (Fmin), may be less ordinate.

Tse will be explained by such a setting. In a large number of types of signals (for example, small ones), which come to the input of the transmission, the amplitude of the high-frequency storage spectrum is slightly lower than in the low and middle frequencies. If there is noise at the inputs of the detector in the receiver, then spectral power post_yna in the smuga border

priymach. As a result, the modulation efficiency and the signal-to-noise ratio at the inputs of the detector accepts the signal for high frequencies, but the module appears to be small. To improve the signal-to-noise performance of high-frequency warehouses, a modulo signal during transmission is received by a path more powerful than high-frequency warehouses more number developed at low and mid-frequency storage facilities, and when the detector is received in style, it will be relaxed. The weakening of the high-frequency warehouses to the detector is practically dependent on the high-frequency resonant lances of the receiver. It means that it is permissible for the unit to seat the upper modulatory frequencies to be done before overmodulation (m> 1).

2.1.1.Determination and Variety Signals

Determination signal- Tse signal, mittāve meaning At any given hour, you can transfer from the same unit.

By the application of a deterministic signal (Fig. 10), there can be: after-effects of pulses (shape, amplitude and position in frequent views), without interruptions in signals from given amplitude-phase characteristics.

Methods for obtaining MM signal: analytical viraz (formula), oscillogram, spectral detection.

The butt of the MM signal is determined.

s (t) = S m Sin (w 0 t + j 0)

Vip signal- a signal that would be meaningful, whether it’s any hour late, it’s unattainable, and it can be transmitted from a person who is less than one.

butt inappropriate signal(Fig. 11) you can be a spree, which will show people movement, music; the last of the radio pulses at the inputs of the radio locating receiver; light up, make noise.

2.1.2. Signals that are stuck in radioelectronics

Without interruption for the value (equal) and without interruption for the hour (without interruption or analog) signals- take the value of s (t) and see it at any moment at a given hourly interval (Fig. 12).

Without interruptions for the value and discrete for an hour signals given at discrete values ​​of the hour (at multiple points), the value of the signal s (t) at the number of points received is equal to the value at the singing interval along the ordinate axis.

The term "discrete" characterizes the way of signal acquisition on the axis of the hour (Fig. 13).

Quantized for the value and without interruption for the hour of the signal given on all clock axis, but the value s (t) can be more discrete (quantized) values ​​(Fig. 14).

Quantized by value and discrete by hour (digital) signals- the value of the signal is transmitted to the digital form (Fig. 15).

2.1.3. Pulse signals

Impulse- Kolyvannya, scho is lishe in the fringes of the endless hour. In fig. 16 and 17 represent video pulse and radio pulse.

For trapezoidal video pulse enter parameters:

A - amplitude;

t і - triviality of video pulse;

t f - triviality to the front;

t cf - triviality of vision.

S р (t) = S (t) Sin (w 0 t + j 0)

S in (t) - video impulse is a radio impulse.

Sin (w 0 t + j 0) - zapovnennya radioimpulse.

2.1.4. Special signals

Function included (one function(Fig. 18) for the Heaviside function) I will describe the process of the transition of a physical object from a "zero" to a "single" camp, and moreover, the transition is seen mittuvo.

Delta function (Diracu function)є With an impulse, the triviality of what is pragmatic is zero, at its height the impulse is not intertwined with growth. Vvazhaєtsya, that the function of the system is taken at the tsіy point.

	(2)
	(3)

Based on the principle of exchange of information, there are three types of radio communication:

simplex radio link;

duplex radio link;

for a duplex radio link.

For the type of equipment, how to play in the radio channels, you can see the radio connection:

telephone;

telegraph;

transmission of tribute;

facsimile;

television;

radio communication.

For the type of radio channels, the connection is as follows:

superficial hviley;

tropospheric;

ionosphere;

meteor;

cosmic;

radio relay.

See the documented radio link:

telegraph call;

transfer of tributes;

facsimile call.

Telegraphic call - for supervising the alphanumeric text in front of the viewer.

Transfer of tribute for the exchange of formalized information between people and EOM or between EOM.

Facsimile transmission of electrical signals for non-sound images.

1 - Telex - for the exchange of written correspondence between organizations and installations from the vicistories of Drukarsky machines with an electronic memory;

2 - Tele (video) text - for removing information from the EOM on the monitor;

3 - TB (bureau) fax - to reject vikoristovuyutsya facsimile devices (either at koristuvachiv, or at enterprises).

The radio channels have a wide range of signals in the radio link:

A1 - AT with non-extinguishing controls;

A2 - manipulation of tone-modulated dials

АЗН - А1 (В1) - ОМ with 50% non-bogeyman

AZA - A1 (B1) - OM with 10% non-bogeyman

AZU1 - A1 (Bl) - ОМ without inconsistency

3. Features of the wider range of radios.

Expansion of radiohvil of light, kilometer and hectometric ranges.

For an assessment of the nature of the widening of the radiohill of this range, it is necessary to know the electric power of the material middle-class, for those who expand the radiohville, so to speak. nobility and the atmosphere of the earth.

The law of a new struma in a differential form to bring

tobto. A change in the hour to the flow of magnetic induction will sound like a stream of conductivity and a stream of substitution.

We can write down the price of the rіvnyannya with the urahuvannya of the authorities of the material middle:

λ < 4 м - диэлектрик

4 m< λ < 400 м – полупроводник

λ> 400 m - guide

Sea water:

λ < 3 м - диэлектрик

3 cm< λ < 3 м – полупроводник

λ> 3 m - guide

For hvily mirimetrovogo (SVD):

λ = 10 ÷ 100 km f = 3 ÷ 30 kHz

that kilometer (DW):

λ = 10 ÷ 1 km f = 30 ÷ 300 kHz

the range of the surface of the earth behind its electrical parameters is close to the ideal provider, and the ionosphere is the most efficient and the least electrical penetration, so to speak. close to the guide.

RV ranges of CDV and DV practically do not penetrate near the ground and the ionosphere, which are visible from their surfaces and can be widened by natural radio paths in many places without waste of energy by surface and spacious needles.

Because Dovzhina was sick of the SDV in the range from the point of view to the lower boundary of the ionosphere, then the understanding of the simple and superficial impairment of the senses.

The process of extending the RV is seen as the ones that are seen by the spherical grower:

Inner side - earth

This side (at night - ball E, in the day - ball D)

The water-flowing process is characterized by insignificant losses of energy.

Optimal RV - 25 ÷ 30 km

Critical RV (stronger decay) - 100 km or more.

Lured appearances: - zammirannya, radio moon.

Heads of death (fedings) as a result of the RV interferences, have passed the new paths and may have risen to the point of arrival.

Yaksho protifazi in the point of reception of the surface and spaciousness, the center of fading.

It’s like a protyphase in a point of a wide open space, a long way away.

Radioecho - the process of repeating the signal as a result of the last reception of the loss, but the number of times (the near radio moon) was seen from the ionosphere or the number of times (near the radio moon) came to the point of reception without the fire of the earthly moon (beyond the radio moon).

The earth's surface has strong power, and the misconception of the minds of the ionization of the ionosphere pours little on the wider RV VLF range, then the amount of energy for the radio signal does not change much.

At the range of km there are good turns and surface and spaciousness (both day and night), especially at lengths λ> 3 km.

The upper crumblings in case of viprominuvanny may be more than 3-4 degrees, and the vastness of the vapors will rise from the great huts to the earth's surface.

Critical cut of the fall RV km. the range of the arches of malias (in the daytime for the ball D, and at night for the ball E). The promenade with kutami is near 90 ° seen from the ionosphere.

At the top of the range, diffraction harnesses can be used to avoid connections for distances up to 1000 km or more. However, from the moment of appearance of the disease, it is strongly extinguished. (For 1000 km of the surface there is a demand for the intensity of the space).

On the great backs of the ring, there is only a wide km of hviley. In the area of ​​equal intensity of the surface and spaciousness, the neighboring federation is promoted. Mind the wider km hvil may be stale during the season, the level of sleepy activity, weakly stale for an hour dib (at night, the signal is greater).

At a distance of about a kilometer, it is easy to go down through a strong atmospheric pereshkody (thunderstorm).

When moving from KM (DV) km to the hectometer range, the conductivity of the earth and the ionosphere changes. ε land and come close to ε atmosphere.

Grow to waste the earth. Chvili more penetrate the ionosphere. There are hundreds of kilometers in the country to repair the vastness of the sick, because the surface is glazed by the earth and extinguished.

In the country, there are approximately 50-200 km of surface and the vastness of the space for the intensiveness and the possibility of nearby feeding.

Zavmirannya part and glibokі.

With a change in λ glybin, the growth rate will freeze with a change in triviality.

She is especially strong at over 100 m.

The average triviality varies from several seconds (1 s) to several tens of seconds.

Mind the radio link in the hectometer range (CB) to lay down during the season and hour to finish, because the ball D is znika, and the ball E is a vische, and moreover, the ball D has a great bowel movement.

The distance of the sound at night is greater, less than the day.

A fee must be paid to the reception for a change in the electronic density of the ionosphere and to relax in the atmospheric fields. At places of origin, there are some promises.

RozpovsyujennyaRV- Decameter range (KV).

During the transition from the NE to the HF, it sinks into the ground, it will greatly increase (the ground is not well understood by the electrician), in the atmosphere (ionosphere) it will change.

On the surface of the natural radio paths, the HF range is less significant (weak diffraction, stronger clay).

Amplitude modulation (AM) є We will be most forgiven and even broadened in radio technology by means of introducing high-frequency information. With AM, the amplitude of a non-random colony is changing behind the law, which is based on the law of change of transmitted time, the frequency of the cob phase of the conversation is unimportant. Therefore, for the amplitude-modulated radio signal, the zagalny virase (3.1) can be replaced by the attacker:

The nature of the fire A (t) appears to be the type of occasion that is transmitted.

In the case of uninterrupted disturbance (Fig. 3.1, a), modulation of the swelling of the eye, shown in Fig. 3.1 b. The envelope A (t) is formed by the shape of the modulating function, that is, from the transmission of s (t). Figure 3.1 b stimuli in the pre-set, but the post-storage function s (t) downgrade to zero (in contrast, the amplitude of the non-modulated head may not be lost with the amplitude of the non-modulated head). The most significant change A (t) "down" can be more. Zmіna and "uphill" can be in principle and more.

The main parameter of the amplitude-modulated communication is the modulation efficiency.

Small. 3.1. Modulative function (a) and amplitude-modulation (b)

The designation of the understanding is especially specific for the tonal modulation, if the function is for the module, for the harmonious combination:

The original modular collector can be paid at the viglyad.

de - modulation frequency; - The cob phase is fiery; - Coefficients of proportions; - the amplitude of the fire (Fig. 3.2).

Small. 3.2. Column, modulated by amplitude harmonic function

Small. 3.3. Communication, modulated amplitude and impulse response

Shrine

be called a modulation function.

With such a rank, mittєve, the meaning of a modular colivan

When the modulation is not created, the amplitude of the amount of movement changes in the boundaries from the smallest to the maximum.

As long as the amplitude changes and the average for the period changes high frequency toughness of the modular collector. For reasons of extreme tension, (1 to 4 times more effort of non-functional kneeling. The average for the period of modulation the tension of proportions to the mean square of the amplitude A (t):

The tenseness of the toughness will change the tenseness of the non-fatty kolivannya at times. In such a rank, at 100% modulation (M = 1), there is a strong tightness to the door and an average hardness (through the designation of the hardness of an unacceptable colony). It can be seen that, due to the modulation of the modulation of the strain of the colony, as in the main and the beginning of the vision of the occasion during the reception, when the borderline modulation of the modulation does not interfere with half of the strain of the colony.

When transmitting discrete events, which is to the circuit of pulses and pauses (Fig. 3.3, a), the modulation of the display of the sequence of the radio pulses, the images in Fig. 3.3 b. At the same time, rely on respect, the phase of the high-frequency storage in the skin impulses is also the same, as in the case of "narisanny" from one uninterrupted harmonic colony.

Only for the price is shown in fig. 3.3 b the last of the radio pulses can be interpreted as a signal, modulation is not possible in terms of amplitude. As the phase changes from an impulse to an impulse, then talk about a change in amplitude-coil modulation.