CN1046422A - The pressure zone system of frequency-modulated wave passband - Google Patents

Abstract

The present invention relates in the radio transmission field, a kind of system and device of relevant compression frequency-modulated wave passband, this system is divided into: amplification, frequency division, three parts of filtering, frequency-modulated wave is by amplifying circuit and several grades of frequency-halving circuits, high-frequency signal is advanced frequency division and obtains the narrow-band FM signal, native system is added in the specific fm transmitter system, and in can offering, shortwave is FM broadcasting frequently.

Description

The pressure zone system of frequency-modulated wave passband

FM broadcasting is strong with its antijamming capability, and the characteristics that tonequality is good have the trend that replaces amplitude modulation broadcasting greatly.But FM broadcasting is because need the passband of broad, and fails to use in 535 kilo hertzs of sesame to 1605 kilo hertz sesames of medium wave band always.For above-mentioned reasons, native system is started with from the method that solves passband, makes the broad passband be compressed into the arrowband and sets up.Use native system can offer the medium wave band FM broadcasting, improve present medium wave band because the amplitude modulation mode causes, noise is big, the defective of lower tone.

Native system mainly is divided into: amplification, frequency division, three parts of filtering, native system are again parts of whole transmitter, and it is 9 megahertz high frequencies that oscillator produces frequency, the ripple of constant amplitude.With changing the FM signal that to obtain one 9 megahertz frequency deviation be 150 kilo hertzs of sesames of parameter in the resonant tank, amplify behind the input native system, preceding two-stage amplified signal voltage magnitude just should reach and make back two-stage amplification enter on off state.The output of amplifier inserts the frequency dividing circuit that is made of d type flip flop, carries out the level Four two divided-frequency.Output emitter follower of termination carries out power amplification again and is penetrated by the outside width of cloth of antenna after filter leaches the electric switch circuit and causes high order harmonic component.

Receiver just can receive with general medium wave amplitude modulation machine, utilizes passband both sides part to carry out slope detection mode to come the audio detection signal so the amplitude modulation machine can receive frequency-modulated wave.Utilize the amplitude modulation machine to receive FM signal a distorted spots is all arranged in the scope that can receive signal.Find this distorted spots just can prove that the signal that is received is a FM signal.And this puts the choice of optimal frequency point of receiver just concerning amplitude-modulated wave.

The realization of native system pressure zone mainly is that high-frequency signal passes through due to the frequency dividing circuit, the frequency-modulated wave of the positive and negative 75 kilo hertzs of sesames of 9 megahertz frequency deviations has just become the FM signal of the positive and negative 37.5 kilo hertzs of sesames of 4.5 megahertz frequency deviations behind two divided-frequency, through behind four two divided-frequencies, just become the frequency-modulated wave of 562.5 kilo hertzs of positive and negative 4.7 kilo hertzs of sesames of sesame frequency deviation.The frequency deviation region of positive 4.7 kilo hertzs of sesames of negative frequency deviation is less than the scope of 10 kilo hertzs of sesames of medium wave band, thereby can realize the mode of frequency regulation of arrowband.

Frequency divider can compress passband, and there is no question about, and crucial problem is that can the side wave composition of frequency-modulated wave all or remaining more than 90 percent.It will be argued that: in order in the process of frequency division, to keep original effective information side wave composition by each composition of modulating generation.Keep more than 99 percent, the amplitude of the sine wave of describing at the input voltage of input before the frequency divider should be that of pressing of frequency divider input gate gives more than the fixed multiple and could satisfy to the degree of giving thinking.

Theoretical as follows:

1, the current amplitude of frequency-modulated wave full detail side wave composition, in circuit, all show as with the vector of carrier current and.

2, carrier wave all can not be desirable sine wave when modulated signals is modulated.

3, because carrier wave all is a non-sinusoidal waveform when modulated, keep whole compositions of original information side wave, the frequency divider input switch constantly just should just become very necessary ad infinitum near the zero point of carrier current.The input frequency divider is described the sinusoidal voltage amplitude and has just been become the problem that must be illustrated with the ratio that the switch door of frequency divider is pressed.It is impossible will keeping hundred-percent side frequency deal in practice, therefore only gets 99 percent here and discusses.

At first set up a rectangular coordinate system, if Y-axis is the amplitude of carrier voltage is 100%, when if carrier voltage is up to zero, be 100% also with regard to the initial point of the X-axis time when voltage is zero, keep 99 percent of side wave, close so the time drive trigger (frequency divider) can only be limited to the X-axis time 99 percent to the moment of one of percentage 101 zero one, this constantly carrier wave amplitude that can reach must be greater than or equal to frequency divider switch door pressure.So, this amplitude has just become the trigonometric function relation with the relation of carrier wave maximum voltage, just the time 99% that square deducts of the maximum amplitude of carrier wave square after the number of extraction of square root

That is: $\sqrt{1^2\mathrm{-\; (\; 0.99\; )}{}^2}\mathrm{=\; 1.414\%}$

Just to have only maximum carrier amplitude be that the 1 ÷ 0.01414=70.7 that frequency divider switch door is pressed doubly could satisfy above-mentioned condition with interior just to have only the input gate of frequency divider to press to be 99%-101% that 1.414% time that just can keep the switch frequency divider of carrier wave maximum amplitude is controlled at 1/4 cycle time of whole carrier wave.

In fm transmitter system, maximum frequency deviation is limited in positive and negative 75 kilo hertzs of sesames modulation degree at this moment as 100%, if the frequency that the amplitude of an audio signal can make carrier wave produce positive and negative 30 kilo hertzs of sesame frequency deviation audio signals is the amplitude of 2 kilo hertzs of sesame first side wave numbers is 20.5% of carrier amplitude, 20.5% * 1.414% ≈ 0.0029 is so just arranged

344 times of 1 ÷, 0.0029 ≈

So the voltage described of carrier wave should be that 344 times of ability that the frequency divider door is pressed keep 99% of original information side wave under these conditions.The switching surge of the input of logical gate in system, as long as the door greater than frequency divider is pressed, the peak value that frequency divider is imported with regard to working is higher than the above part of frequency divider operation voltage and can prescinds fully, that is to say that the edge of logical gate must be consistent also just passable with the curve corresponding points that the multiple of setting is described.Why a part is operated on off state in Here it is the high-frequency amplifier circuit, and a part is operated in the reason of magnifying state.

As above theory is to sum up reasoning in person to come out also to need further to improve and confirm.

Use native system, can offer the medium wave band FM broadcasting, can increase the utilance of radio broadcasting and communication channel.Might make television broadcasting use mode of frequency regulation to make over the horizon in short-wave band by pressure zone transmits.Can expand the topped area of TV station and radio station like this.Might replace the effect of live telecast satellite in the future.

Fig. 1 is the schematic diagram that rectangular coordinate system is used for illustrating carrier voltage and frequency dividing circuit relation.Dotted line A is the high level of divider gate circuit conducting among the figure, B is the low level that divider gate circuit is ended, and input switch voltage is exactly carrier wave sinusoidal voltage peak value after the amplification of describing as the C among the 5.4V-3.6V figure when using integrated circuit block LC4013 operating voltage as 9V.Solid line D square wave basically is the magnitude of voltage of the actual input of gate circuit among the figure.

Empty right side part is the high-frequency amplifier that five transistors are formed among Fig. 2, crystalline substance is 3DG8CB β value all more than 60, back two-stage collector voltage is not all selected two LC4013 double D triggers for use at 4.5 volts of frequency dividing circuits when having the signal input, so because the LC4013 maximum operating voltage is that 10 megahertz operating voltages can only be selected 9V for the 10V maximum operating frequency, the high-frequency signal of input can not be greater than 9 megahertzs.C among the figure ₆Value can not be too big, in order to avoid influence the prime vibration, frequency divider output connects the one-level emitter follower, and effect is to prevent the influence of back level to prime.

Claims (7)

1, be added in the radio checking station, before the emission system power-amplifier stage, compress the system and device of passband, this device is made up of: amplification, frequency division, three parts of filtering, it is characterized in that:

The voltage magnitude that a, amplification output are described by sine curve, be that of pressing of frequency divider switch door gives and decides multiple, computational methods: 70.7 times of percentages (this value can be looked into the Bessel function table) divided by the relative voltage amplitude of the highest number number side wave in the incoming wave passband

B, this system have: amplification, frequency division, three parts of filtering, amplifier section has several grades of amplifiers, high-frequency fm signal is amplified, and the part of waveform is amplified, frequency division partly by being made up of several grades of two-dividers of two divided-frequency ability, be made up of the resonant tank that the LC element constitutes by filter circuit.

2, according to claim 1 described system and device, it is characterized in that output frequency value than incoming frequency value low one be N the octave at the end with 2.

3, according to claim 1 described system and device, it is characterized in that amplifying, the frequency division element can be vacuum tube, transistor, or integrated circuit, also can load in mixture.

4, according to claim 1 described system and device and claim 3 described contents, it is characterized in that every grade of amplifying circuit can be the cascode level, also can be the grounded base form.

5,, it is characterized in that every grade of frequency divider can select bistable circuit, d type flip flop, JK flip-flop for use and have the circuit of same function to form according to claim 1 described system and device and claim 3 described contents.

6,, it is characterized in that when the high order harmonic component that the later power amplifier LC loop of this device produces frequency division has enough inhibition abilities, can casting out the filtering part according to claim 1 described system and device.

7, according to b in the claim 1, described content is characterized in that the progression of amplifier section, frequency division part can be determined according to actual conditions and needs.

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