CN105429652A - Sinusoidal wave frequency modulation circuit - Google Patents

Abstract

The invention provides a sinusoidal wave frequency modulation circuit, comprising: a phase-locked loop connected to a crystal oscillator; a low pass filter connected to an output end of the phase-locked loop; a voltage controlled oscillator connected to the output end of the low pass filter, one path of the output end of the voltage controlled oscillator feeds back to the phase-locked loop through a frequency multiplier circuit, the other path outputs to an amplifier, and the output end of the amplifier is connected to a control end of a switch driver; and the frequency multiplier circuit comprises a threefold frequency multiplier and a sixfold frequency multiplier which are connected in parallel, and the threefold frequency multiplier and the sixfold frequency multiplier are connected to the phase-locked loop through a first regulating switch and a second regulating switch respectively. The sinusoidal wave frequency modulation circuit provided by the invention can realize multi-gear adjustability of output frequency under the condition that the oscillation frequency of the crystal oscillator is fixed, and a user can conveniently set the output frequency of the sinusoidal wave frequency modulation circuit through gears on the outer surface.

Description

A kind of sinusoidal wave FM circuit

Technical field

The present invention relates to electronic technology field, particularly the sinusoidal wave FM circuit of one.

Background technology

Signal generator, for generation of the electric test signal of special parameter needed for circuit-under-test.When testing, studying or adjust electronic circuit and equipment, for measuring some electric parameters of circuit, as frequency response, noise factor, for voltmeter is spent surely, all require to provide the signal of telecommunication meeting determined technical conditions, to simulate the pumping signal of the Devices to test used in real work.

When requiring the steady-state characteristic of carrying out system to measure, the sine signal source that amplitude, frequency are known need be used.When the transient response of test macro, need again the rectangular pulse source using leading edge time, pulse duration and repetition period known.And require the parameter that signal source outputs signal, as frequency, waveform, output voltage or power etc., accurate adjustment can be carried out within the specific limits, have good stability have and export instruction.

Signal source according to the difference of output waveform, can be divided into the four large classes such as sine wave signal generator, rectangular pulse signal generator, function signal generator and random signal generator.

Sinusoidal signal is most popular test signal, this is because the Measures compare producing sinusoidal signal is simple, and measures more convenient by sinusoidal signal.

Sinusoidal signal generator: sinusoidal signal is mainly used in the frequency characteristic of measuring circuit and system, nonlinear distortion, gain and sensitivity etc.Low frequency generator, high frequency signal generator and microwave signal generator is divided into by frequency coverage; Simplfied signal generator (i.e. signal source), standard signal generator (power output can decay to below-100 dBms exactly) and power signal generator (power output reaches more than tens of milliwatt) is divided into by output level adjustable extent and stability; Tuner-type signal generator, sweep-frequency Békésy audiometer signal generator, program control type signal generator and frequency synthesising type signal generator etc. are divided into by the mode of frequency shift.

Low frequency generator comprises the sine-wave generator of audio frequency (200 ~ 20000 hertz) and video (1 hertz ~ 10 megahertz) scope.Master-oscillator generally uses RC formula oscillator, also can use beat frequency oscillator.For ease of the frequency characteristic of test macro, require to export the gentle wave distortion of amplitude-frequency characteristic little.

High frequency signal generator, frequency is the high frequency of 100 kilo hertzs ~ 30 megahertzes, the very high frequency signal generator of 30 ~ 300 megahertzes.General employing LC tuned resonator, frequency can be read by the circular graduation of tuning capacitor, main application measures the technical indicator of various receiver, and output signal useable internal or additional Low Frequency Sine Signals amplitude modulation or frequency modulation, enable output carrier voltage decay to below 1 microvolt.

Microwave signal generator, from decimeter wave until the signal generator of millimeter wave band.Signal usually by ultrahigh frequency triode and the reflex klystron generation of band distributed constant resonant cavity, but has gradually by the trend of the solid state device replacements such as microwave transistor, field effect transistor and Gunn diode.Instrument generally changes frequency by mechanical tuning cavity, and about every platform can cover an octave, the signal power be coupled out by cavity generally can reach more than 10 milliwatts.Simple signal source is only required and can be added 1000 hertz of square wave amplitude modulation, and standard signal generator then can by output reference level adjustment to 1 milliwatt, then from after with the dBm value of attenuator read output signal level; Also must there be inner or additional rectangular pulse amplitude modulation, to test the receivers such as radar.

Existing sinusoidal signal generator can only a kind of signal of single output, and as low frequency signal, high-frequency signal or microwave signal, the sinusoidal signal generator how providing one kind of multiple signals to export is current problem demanding prompt solution.

Summary of the invention

In order to address the deficiencies of the prior art, the present invention proposes a kind of sinusoidal wave FM circuit, sine wave output signal.

Technical scheme of the present invention is achieved in that

A kind of sinusoidal wave FM circuit, comprising:

Comprise phase-locked loop, it is connected to crystal oscillator, and described phase-locked loop is digital phase-locked loop, comprises that phase reference extracts circuit, crystal oscillator, frequency divider, phase comparator, pulse are mended and to be smeared composition; Signal frequency and the required frequency of frequency divider output are very close, itself and the phase reference signal that extracts from signal are sent into phase comparator simultaneously, just smear door to erase the pulse of an input frequency divider by mending when comparative result illustrates that local frequency is high, be equivalent to local oscillating frequency and reduce; On the contrary, if just insert a pulse between two input pulses of fraction frequency device input end when illustrating that local frequency is low, be equivalent to local oscillating frequency and rise, thus reach synchronous;

Low pass filter, is connected to the output of phase-locked loop, and described low pass filter is Chebyshev filter;

Voltage controlled oscillator, is connected to low pass filter output, and its output is leaded up to frequency multiplier circuit and fed back to phase-locked loop, and another road exports amplifier to, and the output of amplifier is connected to the control end of described switch driver;

Described voltage controlled oscillator is that carat sprinkles type LC voltage controlled oscillator, comprising: transistor T, loop inductance L, tank capacitance C1, C2, Cv, the capacity presented when Cv is variable capacitance diode reverse bias; C1, C2 are more much bigger than Cv;

Described frequency multiplier circuit comprises 3 frequency multipliers, 6 frequency multipliers that are connected in parallel, and described 3 frequency multipliers, 6 frequency multipliers are connected to described phase-locked loop respectively by the first by-pass cock, the second by-pass cock;

The button that described first by-pass cock, the second by-pass cock touch with hand is connected.

Alternatively, described low pass filter is second order Chebyshev filter.

The invention has the beneficial effects as follows:

Under the frequency of oscillation fixing situation of crystal oscillator, many grades that can realize output frequency adjustable, and user can set the output frequency of sinusoidal wave FM circuit, for various application scenario provides suitable reference frequency signal easily by the gear of outer surface.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

Fig. 1 is the control block diagram of the sinusoidal wave FM circuit of the present invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

As shown in Figure 1, sinusoidal wave FM circuit 40 of the present invention, comprise phase-locked loop 41, it is connected to crystal oscillator 100; Low pass filter 42, is connected to the output of phase-locked loop 41; Voltage controlled oscillator 43, its output is leaded up to frequency multiplier circuit and is fed back to phase-locked loop, and another road exports amplifier 44 to, and the output of amplifier 44 exports first frequency signal f and is connected to the control end of described switch driver 13.Preferably, the frequency of oscillation of described crystal oscillator 100 is 100MHz.

Described frequency multiplier circuit comprises 3 frequency multiplier 45,6 frequency multiplier 46,3 frequency multipliers, 6 frequency multipliers that are connected in parallel and is connected to phase-locked loop 41 respectively by the first by-pass cock 51, second by-pass cock 52; Described first by-pass cock 51, second by-pass cock 52 is connected with the button on outer surface, on button, mark has frequency values, such as 1,2 grade, by operating the turn-on and turn-off of the corresponding by-pass cock of button control of outer surface, control first frequency signal f, realize the adjustment of frequency.

Preferably, described low pass filter is Chebyshev filter.

Chebyshev filter is faster than the decay of Butterworth filter in transition band, but the amplitude-frequency characteristic of frequency response is smooth not as the latter.Error between Chebyshev filter and the frequency response curve of ideal filter is minimum, but there is amplitude fluctuation in passband.

Preferably, described low pass filter is second order Chebyshev filter.

Preferably, described voltage controlled oscillator is LC oscillator.

In any one LC oscillator, voltage-controlled variable reactance component is inserted oscillation circuit and just can form LC voltage controlled oscillator.Early stage voltage-controlled variable reactance component is reactance-tube, mostly uses variable capacitance diode afterwards.

Preferably, LC oscillator of the present invention is that carat sprinkles type LC voltage controlled oscillator, comprising: transistor T, loop inductance L, tank capacitance C1, C2, Cv, the capacity presented when Cv is variable capacitance diode reverse bias; C1, C2 are usually much bigger than Cv.When input control voltage uc changes, Cv changes thereupon, thus changes frequency of oscillation.Pass between the output frequency of this voltage controlled oscillator and input control voltage is:

${\mathrm{\ω}}_0\≈\frac{1}{\sqrt{{\mathrm{LC}}_0}}{(1+\frac{u_c}{\mathrm{\φ}})}^{\mathrm{\γ}/2}$

C in formula ₀the capacitance of variable capacitance diode when being zero reverse biased; φ is the junction voltage of variable capacitance diode; γ is junction capacitance variability index.In order to obtain Linear Control characteristic, various indemnifying measure can be taked.

Preferably, described phase-locked loop is digital phase-locked loop.

Digital phase-locked loop extracts circuit primarily of phase reference, compositions such as smearing is mended in crystal oscillator, frequency divider, phase comparator, pulse.Signal frequency and the required frequency of frequency divider output are very close, phase comparator is sent in it and the phase reference signal that extracts from signal simultaneously, just smear door to erase the pulse of an input frequency divider by mending when comparative result illustrates that local frequency is high, be equivalent to local oscillating frequency and reduce; On the contrary, if just insert a pulse between two input pulses of fraction frequency device input end when illustrating that local frequency is low, be equivalent to local oscillating frequency and rise, thus reach synchronous.

Sinusoidal wave FM circuit of the present invention, under the frequency of oscillation fixing situation of crystal oscillator, many grades that can realize output frequency adjustable, and user can set the output frequency of sinusoidal wave FM circuit, for various application scenario provides suitable reference frequency signal easily by the gear of outer surface.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (2)

1. a sinusoidal wave FM circuit, is characterized in that, comprising:

Comprise phase-locked loop, it is connected to crystal oscillator, and described phase-locked loop is digital phase-locked loop, comprises that phase reference extracts circuit, crystal oscillator, frequency divider, phase comparator, pulse are mended and to be smeared composition; Signal frequency and the required frequency of frequency divider output are very close, itself and the phase reference signal that extracts from signal are sent into phase comparator simultaneously, just smear door to erase the pulse of an input frequency divider by mending when comparative result illustrates that local frequency is high, be equivalent to local oscillating frequency and reduce; On the contrary, if just insert a pulse between two input pulses of fraction frequency device input end when illustrating that local frequency is low, be equivalent to local oscillating frequency and rise, thus reach synchronous;

Low pass filter, is connected to the output of phase-locked loop, and described low pass filter is Chebyshev filter;

Voltage controlled oscillator, is connected to low pass filter output, and its output is leaded up to frequency multiplier circuit and fed back to phase-locked loop, and another road exports amplifier to, and the output of amplifier is connected to the control end of described switch driver;

Described voltage controlled oscillator is that carat sprinkles type LC voltage controlled oscillator, comprising: transistor T, loop inductance L, tank capacitance C1, C2, Cv, the capacity presented when Cv is variable capacitance diode reverse bias; C1, C2 are more much bigger than Cv;

Described frequency multiplier circuit comprises 3 frequency multipliers, 6 frequency multipliers that are connected in parallel, and described 3 frequency multipliers, 6 frequency multipliers are connected to described phase-locked loop respectively by the first by-pass cock, the second by-pass cock;

The button that described first by-pass cock, the second by-pass cock touch with hand is connected.

2. sinusoidal wave FM circuit as claimed in claim 1, is characterized in that, described low pass filter is second order Chebyshev filter.