CN1564470A - Electronic sightseeing tourist system using phase-locked loop - Google Patents

Abstract

The designed guiding device is suitable to tourists to gird on body. The receiver includes case, circuit boards inside case and battery and earphone. In circuit boards, connections between boards are as following: output end of mixer circuit is connected to voltage controlled oscillator; output end of voltage controlled oscillator is connected to demodulator; output of the demodulator is connected to note magnification circuit and then earphone. Disclosed device raises performance of receiver, which is compatible to common radio set.

Description

Adopt the electronic guide system of phase-locked loop

Technical field

The present invention relates to the technical equipment of travelling, refer in particular to a kind of electronic guide system that utilizes Phase Lock Technique.

Background technology

When the visitor goes sight-seeing in the scenic spot, often need guide interpreting.At present, the mode of this guide interpreting mainly contains two kinds, and a kind of is to follow the visitor by full-time guide to walk about, no matter to the visitor or to Destination Management department, the expense of being changed is all than higher.

Another kind is an electronic guide, promptly utilizes the electronics receive-transmit system, will explain content and launch, and comes the receiver related content by the visitor of hand receiver machine according to the wish of oneself.At present, the existing problem of this electronic guide is: transmitting-receiving poor stability, cost be than higher, when being leased to the visitor and using, and the management trouble.

Summary of the invention

The objective of the invention is to design a kind of electronic guide system that adopts phase-locked loop, accept performance, make things convenient for the visitor to answer,, can use as common broadcast receiver again in time spent not with raising.

According to design provided by the present invention, adopt the electronic guide system of phase-locked loop to comprise transmitter section and receiver section, it is characterized in that: in transmitter section, the output of transmitter phase-locked loop connects radio frequency amplifying circuit, after the transmitter phase-locked loop obtains high-quality radio-frequency signal source, modulated signal is amplified after antenna is externally launched by radio frequency amplifying circuit, the input at the transmitter phase-locked loop connects sound circuit again; In receiver section, the output of mixting circuit connects the receiver phase-locked loop, and the input of mixting circuit is connected with receiver antenna, is connected audio amplifier circuit between the output of receiver phase-locked loop and receiver antenna.

The output of voltage controlled oscillator connects mixting circuit, and at the output connection demodulator of mixting circuit, the output of demodulator is connected with earphone after connecting audio amplifier circuit again.The output of mixting circuit is connected with demodulator simultaneously.

Output connection at demodulator is used for the radio-frequency component of filtering error voltage Se (t) and the loop filter of noise, output at loop filter connects phase discriminator, the output of phase discriminator is connected with voltage controlled oscillator again, form the receiver phase-locked loop with this, the phase discriminator output signal removes to control the oscillator signal of voltage controlled oscillator, improve the frequency stability of oscillator signal, demodulator is exported to audio amplifier circuit after with the audio-frequency unit demodulation in the mixting circuit output signal.Utilize earphone cord as receiver antenna.

Between transmitter phase-locked loop and sound circuit, be connected voltage-controlled frequency interleaved modulation modulator, record the explanatory content at various scenic spots in the sound circuit, be transported to again in the voltage-controlled frequency interleaved modulation modulator, send with the radio frequency signal.

Radio frequency amplifying circuit by the radio frequency buffering device that is used between power amplifier and phase-locked loop, playing buffer action, be used for power amplifier that the radiofrequency signal of frequency synthesizer of phase locking able to programme output is amplified, sent by radio-frequency antenna then and coupling and filter circuit and be connected in sequence, the output of coupling and filter circuit is connected with transmitter antenna, after obtaining high-quality radio-frequency signal source, modulated signal is amplified after antenna is externally launched by wide-band radio frequency power amplifier.The transmitter phase-locked loop is the frequency synthesizer of phase locking able to programme that frequency adjustment is simple, be convenient to multilingual emission.

Advantage of the present invention is: except the advantage that general electronic guide possessed, because the receiver and the transmitter section of this system have all adopted PHASE-LOCKED LOOP PLL TECHNIQUE, oscillation signal frequency stability is improved greatly.Because oscillator signal is subjected to the control of phase discriminator output signal, when oscilator drift occurring when being subjected to the variation of temperature and external environment, control voltage on the variable capacitance diode in the voltage controlled oscillator can be revised under the effect of phase discriminator automatically, thereby makes oscillator frequency keep very high stability.

In addition, utilize this device after, use cost is relatively low, manages more conveniently, for visitor and tourist district administrative department, all belongs to a kind of guide system cheap, stable and reliable for performance; And be convenient to develop multilingual, because frequency modulation system is adopted in transmitting-receiving, capture the anti-interference that specific characteristic can improve system so frequency modulation is distinctive.The receiver machine adopts search automatically, uses more convenient, and suitable various languages.Owing to have two frequency ranges, one is used for electronic guide, and another is used for common FM broadcasting use, and therefore, this device not only can be used as visitor's electronic guide, and can be used as common fm broadcast receiver use.

Description of drawings

Fig. 1 is the system block diagram of invention.Fig. 6 is the circuit theory diagrams of receiver.

Fig. 2 is the transmitter circuitry block diagram.

Fig. 3 is the receiver circuit block diagram.

The phase-locked loop circuit block diagram that Fig. 4 is basic.

Fig. 5 is the circuit theory diagrams of transmitter.

Embodiment

As shown in the figure: whole system comprises transmitter section and receiver section, it is characterized in that: in transmitter section, the output of transmitter phase-locked loop connects radio frequency amplifying circuit, at the input connection sound circuit of transmitter phase-locked loop; In receiver section, the output of mixting circuit connects the receiver phase-locked loop, and the input of mixting circuit is connected with receiver antenna, is connected audio amplifier circuit between the output of receiver phase-locked loop and receiver antenna.

The output of mixting circuit connects voltage controlled oscillator, and at the output connection demodulator of voltage controlled oscillator, the output of demodulator is connected with earphone after connecting audio amplifier circuit again.The output of mixting circuit is connected with demodulator simultaneously.Output linkloop filter at demodulator, output at loop filter connects phase discriminator, the output of phase discriminator is connected with voltage controlled oscillator again, the demodulator here, loop filter, phase discriminator and voltage controlled oscillator interconnect, constitute a loop, be commonly called as (receiver) phase-locked loop.

Between transmitter phase-locked loop and sound circuit, be connected voltage-controlled frequency interleaved modulation modulator.Radio frequency amplifying circuit is connected in sequence by radio frequency buffering device, power amplifier, coupling and filter circuit, and the output of coupling and filter circuit is connected with transmitter antenna.The transmitter phase-locked loop is a frequency synthesizer of phase locking able to programme.

In transmitter section, sound circuit is module I SD4004-08, and sound circuit can be recorded the explanatory content at various scenic spots, is transported in the voltage-controlled frequency interleaved modulation modulator again, sends with the radio frequency signal.

Voltage-controlled frequency interleaved modulation modulator is made up of VD1～2, Q1 and resistance R 1～3, capacitor C 1～3 on every side, and the signal of the output of sound circuit is given the voltage-controlled frequency interleaved modulation modulator in the transmitter phase-locked loop.

The transmitter phase-locked loop is a frequency synthesizer of phase locking able to programme, is made up of IC1 (model TEK2000), and the radiofrequency signal of transmitter phase-locked loop output band frequency modulation modulation is delivered to the radio frequency amplifier section.

The radio frequency buffering device is made up of Q2 and resistance R 5～6, capacitor C 6～11 on every side, is used for playing buffer action preferably between power amplifier and phase-locked loop, avoids the phase mutual interference.

Power amplifier and matched filtering circuit are made up of with capacitor C 12～16, inductance L 2 Q3 and resistance R 8 on every side, are used for the radiofrequency signal of frequency synthesizer of phase locking output able to programme is amplified, and are sent by radio-frequency antenna then.

In receiver section, mixting circuit is made up of capacitor C 12, integrated circuit I1 (model TDA7088 or CD9088CB), and the output signal of radiofrequency signal and voltage controlled oscillator produces intermediate-freuqncy signal by mixting circuit, gives the demodulator demodulation.

Voltage controlled oscillator is made up of L1, D1, C5, C6 and I1, the phase discriminator output signal removes to control the oscillator signal of voltage controlled oscillator, improve the frequency stability of oscillator signal, demodulator is exported to audio amplifier circuit after with the audio-frequency unit demodulation in the mixting circuit output signal.Voltage controlled oscillator is a vitals in the phase-locked loop, it directly affects characteristics such as the frequency stability of loop and fm demodulation, so require it that good frequency stability is arranged, voltage---frequency characteristic should be linear, voltage controlled oscillator can be regarded as by two parts and form: one is oscillator itself, the controlled stage that another is made up of variable capacitance diode.After Sd (t) signal was added to the voltage controlled oscillator controlled stage, system forced the output signal Sv (t) of voltage controlled oscillator and reference-input signal Si (t) synchronous, and promptly frequency is identical.

When loop is in synchronously in (stable state) scope, frequency input signal equals pressuring controlling oscillator frequency, be that system does not have frequency error, at this moment just there is a residual phase difference in system, and the existence that is exactly this residual phase difference has guaranteed that just the frequency of voltage controlled oscillator and reference signal is consistent.

Loop filter is made up of C7, I1, and loop filter is mainly used in the filtering high-frequency signal, in order to avoid AC signal is brought in the oscillator.Loop filter plays an important role to the stable of loop, is like this to be used for radio-frequency component and noise among the filtering error voltage Se (t), improves interference suppressioning characteristic.If when system jumped out lock-out state because of the noise transient phenomena, loop filter can provide short-term storage, guarantee very fast recovery locking.Use different loop filters can form different phase-locked loops such as second order, three rank.

Audio amplifier circuit is made up of Q1～2, R4～6, C18～20, and the audio signal of demodulator output is exported to earphone by the audio frequency amplification.

Principle of PLL is as follows:

Phase-locked loop is the same with automatic frequency control system, be a kind of frequency feedback system, its difference is: being compared by the frequency of controlled oscillator and parameter (benchmark) frequency of automatic frequency control system, in order to make this system works, it is one little but need be certain frequency error that it requires output frequency to have.And phase-locked loop does not just have this fixing (frequency) error, and it has only the error of frequency integrator, i.e. the error of phase difference.

Phase-locked loop the most basic is (to claim phase discriminator again by phase comparator, usually contract with English and decide PD and represent), voltage-controlled oscillator (is called for short voltage controlled oscillator, usually contract with English and decide VCO and represent) and low pass filter (claim loop filter again, usually contract with English and decide LPF and represent) form, phase discriminator compares the phase place of the output signal Sv (t) of input signal Si (t) (reference signal) and voltage controlled oscillator, produces the error voltage Se (t) of two signal phase differences.

Loop filter has been stablized the difference important function to loop, mainly is to be used for radio-frequency component and noise among the filtering error voltage Se (t), improves interference suppressioning characteristic.If when system jumped out lock-out state because of the noise transient phenomena, loop filter can provide short-term storage, guarantee very fast recovery locking.Use different loop filters can form different phase-locked loops such as second order, three rank.

Voltage controlled oscillator is the vitals in the phase-locked loop, and it directly affects characteristics such as the frequency stability of loop and fm demodulation, so require it that good frequency stability is arranged, voltage----frequency characteristic should be linear.Voltage controlled oscillator can be regarded as by two parts and form: one is oscillator itself, the controlled stage that another is made up of variable capacitance diode; After Sd (t) signal was added to the voltage controlled oscillator controlled stage, system forced the output signal Sv (t) and reference-input signal Si (t) synchronous (being that frequency is identical) of voltage controlled oscillator.

In the time of in loop is in locking range (stable state), frequency input signal equals pressuring controlling oscillator frequency, and promptly not have frequency plot poor in system.At this moment just there is a residual phase difference in system, and the existence side that is exactly this residual phase difference has guaranteed that the frequency of voltage controlled oscillator and reference signal is consistent.

Phase-locked loop is the phase error automatic control system, carries out the phase bit comparison by phase discriminator, and input signal and voltage controlled oscillator output signal are produced the frequency that error control voltage is adjusted voltage controlled oscillator by phase discriminator, makes and input signal frequency together.When loop is started working, if the different frequencies of input signal with voltage controlled oscillator, then the phase difference between them is changing always, the error voltage of phase discriminator output as a result just changes within the specific limits, and the cosine of phase difference is directly proportional between the direct current output of phase discriminator and two signals, and promptly phase difference was by 90 o'clock, phase discriminator is output as 0, when phase difference departs from 90 and when changing, the then output of phase discriminator or plus or minus, its positive and negative direction that depends on that phase difference changes.Difference on the frequency between its oscillator output signal is zero, and error voltage is a fixed value, and loop is " locked ", the roughly course of work of Here it is phase-locked loop.

Above-mentioned analysis is the input term signal to frequency and phase invariant, if the frequency of input signal and phase place then can make the frequency of voltage controlled oscillator and phase place constantly follow the tracks of the variation of incoming frequency by the effect of loop constantly changing.Phase-locked loop has good performance for tracking.If during the input FM signal, make loop enough wide usually, so that the modulation spectrum of signal is all within the loop passband, at this moment if phase-locked loop is locked on the FM signal, then voltage controlled oscillator is followed the tracks of the instantaneous frequency of input, and the communication voltage controlled oscillator keeps the error voltage Sd (t) of the filtering of lock-out state to be equivalent to demodulated output signal with input signal.In this case, demodulated input signal only depends on the voltage of voltage controlled oscillator----frequency transmission characteristic, and phase-locked loop can be used to FM signal is carried out demodulation.

The phase-locked link demodulation principle is summarized as follows:

Think that at first simply the tracking error between pressuring controlling oscillator frequency and the input FM signal frequency can ignore, simultaneously, any moment, the frequency Wv of voltage controlled oscillator (t) equates with the instantaneous frequency Wi (t) that imports FM signal.The momentary angular frequency of input FM signal can be expressed as:

Wi(t)＝Wo+KFf(t)..................(1)

Suppose that voltage controlled oscillator (VCO) has the Linear Control characteristic, its slope K v (voltage-controlled sensitivity) is with radian per second. volt expression) and during t=0, the frequency of oscillation of voltage controlled oscillator is Wo ', then when control voltage, the instantaneous angular frequency of voltage controlled oscillator is:

Wv(t)＝Wo’+KvSd(t)................(2)

Make (1) (2) formula equate, can get:

$\mathrm{Sd}\left(t\right)=\frac{\mathrm{Wo}-\mathrm{Wo}\text{'}}{\mathrm{Kv}}+\frac{\mathrm{Kf}}{\mathrm{Kv}}f\left(t\right)...\left(3\right)$

(3) Wo is the carrier frequency of input FM signal in, and Wo ' is the natural mode shape of voltage controlled oscillator, and both are all constant.Therefore, first of (3) formula is DC terms, and available stopping direct current element is eliminated, that is:

Sd(t)＝Kf/kv*f(t).................(4)

As seen phase-locked loop output except odd number Kf/Kv, is approximately equal to former modulation waveform f (t), thereby reaches the purpose of frequency demodulation.

Phase-locked loop also can be used to do the amplitude-modulated signal demodulation, and signal is carried out amplitude limit, can carry out frequency inverted, can carry out frequency modulation of the phase locking or the like.Because the design does not relate to this type of application, so do not explain one by one.

Phase-locked loop not only can obtain high frequency stability, and can be by reasonably selecting loop parameter (mainly being the parameter of loop filter), can be under the condition that satisfies the demodulation requirement closed-loop bandwidth on cyclization road narrow as far as possible so that suppress noise, have good signal-to-noise.Faint when the receiver signal level, when noise becomes major consideration, adopt phase-locked link demodulation can improve performance.Because phase locked looped function is many, performance is good, so be used widely in fields such as radio communication, radar, microwave relay, space technology and TV, remote measurements.The design has adopted PHASE-LOCKED LOOP PLL TECHNIQUE, has promoted the performance of electronic guide product, has reduced product cost again relatively simultaneously, satisfies various language guides in the period that tourist industry will soon develop on a large scale, and this Products Development will be added wing to Tourism development and be added the wing.

In design, receiver should adopt the demodulation of phase locking technology, accomplishes that again the receiver of design cost and phase-locked loop can be compared.The employing of TDA7088 integrated circuit has solved this problem, TDA7088 is the fm broadcast receiver circuit of Dutch Philips company exploitation, this circuit adopts PHASE-LOCKED LOOP PLL TECHNIQUE can realize searching for automatically the radio station, is the integrated circuit of a unique competitively priced quality in the IC circuit.

In the design, utilize frequency range switch (SWIA among the receiver principle figure) and capacitor C 4 to reach the purpose of designing requirement.Use the frequency range of 84MHz by frequency range conversion when the electronic guide, can be used as the fm broadcast receiver use of 88MHz at ordinary times to 108MHz to 87MHz.Reach predetermined purpose of design, realized frequency stabilization, the signal to noise ratio height uses search automatically to transfer platform convenient, and is anti-interference strong, is convenient to multilingual electronic guide etc.

The transmitter section of present design adopts the indirect type synthesis method of the frequency, and promptly utilizing phase-locked loop to make frequency synthesizer is that programmable lock in the transmitter principle block diagram is harmonious and grows up to be a useful person.Frequency synthesizer of phase locking successfully collects the advantage of crystal oscillator and LC oscillator, its special performance can make output signal frequency precision and the stability of voltage controlled oscillator in quite wide frequency coverage reach the crystal oscillator level, and its spectral characteristic will surmount most oscillating circuits far away, and device is simple.This transmitter can be set the transmitter frequency with the step value of 0.1MHz continuously at 80MHz in the 120MHz scope, frequency error is less than 0.002MHz, the frequency drift amount can realize by changing the peripheral parameter of voltage controlled oscillator when being applied to other frequencies simply less than 0.001MHz.After obtaining high-quality radio-frequency signal source, modulated signal is amplified after antenna is externally launched by wide-band radio frequency power amplifier.This machine adopts the man-machine interface of 8 low-power consumption single chip microcomputer regulating frequencies and the data of frequency synthesizer of phase locking able to programme to generate, and frequency adjustment is oversimplified, and is convenient to multilingual emission.Simultaneously, decide memory under program, make the system hardware and software upgrading very convenient owing to adopt to wipe.

Claims (8)

1, adopts the electronic guide system of phase-locked loop, comprise transmitter section and receiver section, it is characterized in that: in transmitter section, the output of transmitter phase-locked loop connects radio frequency amplifying circuit, after the transmitter phase-locked loop obtains high-quality radio-frequency signal source, modulated signal is amplified after antenna is externally launched by radio frequency amplifying circuit, the input at the transmitter phase-locked loop connects sound circuit again; In receiver section, the output of mixting circuit connects the receiver phase-locked loop, and the input of mixting circuit is connected with receiver antenna, is connected audio amplifier circuit between the output of receiver phase-locked loop and receiver antenna.

2, electronic guide system according to claim 1 is characterized in that: the output of voltage controlled oscillator connects mixting circuit, and at the output connection demodulator of mixting circuit, the output of demodulator is connected with earphone after connecting audio amplifier circuit again.

3, electronic guide system according to claim 1 is characterized in that: the output of mixting circuit is connected with demodulator simultaneously.

4, electronic guide system according to claim 1 and 2, it is characterized in that: the output connection at demodulator is used for the radio-frequency component of filtering error voltage Se (t) and the loop filter of noise, output at loop filter connects phase discriminator, the output of phase discriminator is connected with voltage controlled oscillator again, form the receiver phase-locked loop with this, the phase discriminator output signal removes to control the oscillator signal of voltage controlled oscillator, improve the frequency stability of oscillator signal, demodulator is exported to audio amplifier circuit after with the audio-frequency unit demodulation in the mixting circuit output signal.

5, electronic guide system according to claim 1 is characterized in that: utilize earphone cord as receiver antenna.

6, electronic guide system according to claim 1, it is characterized in that: between transmitter phase-locked loop and sound circuit, be connected voltage-controlled frequency interleaved modulation modulator, record the explanatory content at various scenic spots in the sound circuit, be transported to again in the voltage-controlled frequency interleaved modulation modulator, send with the radio frequency signal.

7, electronic guide system according to claim 1, it is characterized in that: radio frequency amplifying circuit by the radio frequency buffering device that is used between power amplifier and phase-locked loop, playing buffer action, be used for power amplifier that the radiofrequency signal of frequency synthesizer of phase locking able to programme output is amplified, sent by radio-frequency antenna then and coupling and filter circuit and be connected in sequence, the output of coupling and filter circuit is connected with transmitter antenna, after obtaining high-quality radio-frequency signal source, modulated signal is amplified after antenna is externally launched by wide-band radio frequency power amplifier.

8, electronic guide system according to claim 1 is characterized in that: the transmitter phase-locked loop is the frequency synthesizer of phase locking able to programme that frequency adjustment is simple, be convenient to multilingual emission.

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