CN1429071A

CN1429071A - Electromagnetic Interference Cancellation Circuit with Phase Shift Unit

Info

Publication number: CN1429071A
Application number: CN 01145220
Authority: CN
Inventors: 郑裕强
Original assignee: Mitac International Corp
Current assignee: Mitac International Corp
Priority date: 2001-12-26
Filing date: 2001-12-26
Publication date: 2003-07-09

Abstract

An electromagnetic interference cancellation circuit with a phase shift unit achieves the purpose of magnetic field cancellation and electric field coupling by phase shifting a signal source. The signal source is phase shifted by a phase shift unit through a routing line, and then transmitted through a microstrip antenna or a stripline antenna to emit phase-shifted electromagnetic waves, which cancel each other out with the original electromagnetic waves, thereby achieving the purpose of suppressing electromagnetic interference noise.

Description

Electromagnetic interference bucking circuit with phase-shifting unit

Technical field

The relevant electromagnetic interference bucking circuit of the present invention, particularly a kind of phase shift by signal source is to reach the bucking circuit of magnetic field cancellation and field coupled.

Background technology

The electromagnetic wave phenomenon is because the dynamically exchange or the variation of electricity, magnetic energy, exist or show with the pattern of fluctuation, along with the interact phenomenon of borne noise of variation electromagnetic wave in medium of time, then claim be electromagnetic interference (Electromagnetic Interference) (EMI).

By the electromagnetic interference (EMI) that interference source produced, it often is low level point generation induction to circuit, after amplifying, become noise output again, the mode of its induction often can be: electrostatic induction, electromagnetic induction, conduction induction etc., under the situation of majority, the reason that forms electromagnetic interference (EMI) is a kind of incessantly, also the more than place of possibility, desire effectively to prevent electromagnetic interference (EMI), then to the reason of its formation and may be the assembly of noise source or circuit is then essential fully understands.

In recent years along with information industry is flourish, the operating frequency of electronic installation is more and more higher, and the signal on the printed circuit board (PCB) also day by day improves, and the printed circuit lines on the printed circuit board (PCB) (strip) is because resistance is higher, though only a little electric current also can cause pressure drop, if the influence of Inductive component is quite big when being used in high frequency, the inductance that is had is very important in high-frequency circuit, the filter (comprising the RC filter of resistance capacitance or the LC filter of inductance capacitance) that generally is added on the signal may influence signal quality (as the rise time of signal, transmission delay and amplitude) consideration under, can't satisfy the counteracting purpose that suppresses electromagnetic interference.

Produce the electromagnetic wave of swinging to and have in addition with signal generator, can reach the effect of cancelling out each other with the electromagnetic interference (EMI) of former existence, but this mode must match with the clock pulse pin of signal generator, comparatively inconvenience on circuit design, the electromagnetic interference (EMI) that therefore how can effectively solve noise source and produced, and taking into account the convenience of circuit design, is a technical task that waits to solve.

Summary of the invention

In view of this, the objective of the invention is to propose a kind of electromagnetic interference bucking circuit with phase-shifting unit, it can be offset electromagnetic interference (EMI) and prevent that high-frequency noise is to harmful effect that electronic installation produced.

Electromagnetic interference bucking circuit according to an aspect of the present invention with phase-shifting unit, it is arranged at an electronic installation, be characterized in, this electromagnetic interference bucking circuit comprises at least: a phase-shifting unit, this phase-shifting unit and a signal acquisition end join, in order to receiving signal, and in addition produce an offseting signal after the phase shift with this signal acquisition end; And an antenna, this antenna and this phase-shifting unit join, and the electromagnetic wave that is used to receive this offseting signal and launch phase shift is to produce magnetic field cancellation and field coupled.

Electromagnetic interference bucking circuit according to a further aspect of the invention with phase-shifting unit, be to be arranged at an electronic installation, this electromagnetic interference bucking circuit includes a phase-shifting unit and an antenna at least, be characterized in: this electromagnetic interference bucking circuit and signal acquisition end with phase-shifting unit joins, in order to receive signal source with this signal acquisition end, and the electromagnetic interference harmonic wave that utilization obtains is extrapolated a fundamental frequency, and with this signal source risen rank to this electromagnetic interference harmonic match, and be sent to this phase-shifting unit and after phase shift, produce an offseting signal and be sent to this antenna, and this antenna is in order to receive this offseting signal and to launch the electromagnetic wave of phase shift, to produce magnetic field cancellation and field coupled.

Adopt such scheme, signal source be by cabling through phase-shifting unit in addition after the phase shift, again through microstrip antenna or stripline antenna,, reach the effect of cancelling out each other with the electromagnetic wave of former existence with the electromagnetic wave of emission phase shift.

For clearer understanding purpose of the present invention, characteristics and advantage, preferred embodiment of the present invention is elaborated below in conjunction with accompanying drawing.

Description of drawings

Fig. 1 is the electromagnetic interference bucking circuit schematic diagram with phase-shifting unit of a preferred embodiment of the present invention;

Fig. 2 A is the standing wave distribution schematic diagram of the antenna that utilizes of a preferred embodiment of the present invention;

Fig. 2 B is the end radiation schematic diagram of antenna that a preferred embodiment of the present invention is utilized;

Fig. 3 is that the electromagnetic field of a preferred embodiment of the present invention is offset and leakage field intensity schematic diagram; And

Fig. 4 A-4H is the pattern figure of existing phase shifter.

Embodiment

Please refer to Fig. 1, have the bucking circuit schematic diagram of the electromagnetic interference of phase-shifting unit for foundation the present invention is disclosed.

Most electronic installation all is provided with clock pulse generator, in order to produce necessary signals such as output, frequency, modulation frequency and modulation degree, and the line pattern (trace) of these clock pulses by printed circuit board (PCB) runs through whole printed circuit board (PCB), the magnetic field that clock pulse caused, electric field that electric current flows then have been full of in the whole electronic installation, and then at far field formation plane wave, therefore the present invention proposes a kind of bucking circuit with phase-shifting unit electromagnetic interference, the harmonic wave of can utilization obtaining is extrapolated fundamental frequency, and phase shift is offseted electromagnetic interference to produce the payment signal again.

At first hypothesis has the electromagnetic interference of 700MHz, then the present invention can capture a signal source by signal acquisition end F, this signal acquisition end F can be the trace (trace) of printed circuit board (PCB), crystal assembly (Crystal), integrated circuit (Integrated Circuit) and oscillator (oscillator) etc. are also risen rank (if signal source is that 10MHz then rises 70 rank to 700MHz, if signal source is that 100MHz then rises 7 rank to 700MHz, in the hope of with the frequency match of electromagnetic interference), and is a glitch (Dummy Signal) with this signal source after by phase-shifting unit 20 phase shifts, this phase-shifting unit 20 is a phase shifter (phase shifter), be resent to the electromagnetic wave of antenna 10, and reach the effect of cancelling out each other with the electromagnetic wave of former existence with the emission phase shift.

Please refer to Fig. 2, the standing wave distribution schematic diagram on the antenna that it utilizes for the embodiment of the invention.

General microstrip antenna (Microstrip antenna) is the front end open circuit with microstripline, utilize the antenna of this part to use as emission, and the below of its relative dielectric medium substrate of microstripline all is a conductor, when the conductor surface of substrate below is bigger when a lot of than this microstripline width W, then this conductor has and the unlimited identical effect of conductor of expansion.At this moment,, then remove following conductor, get two times of intervals, then have and have the equivalent characteristic of the microstripline of electric current in the other direction if there is electric current to flow on the microstripline.Therefore, microstripline is if consider the words of its fictitious current, also be considered as and the identical transmission lines of Lecher line (Lecher), it also is parallel circuit side by side, for distributing, the standing wave on the foundation Lecher line (Lecher) considers dipole antenna, when the open circuit of the two ends of microstripline, the standing wave on the microstripline distributes then shown in Fig. 2 A.

Please refer to Fig. 2 B, the end radiation schematic diagram on the antenna that it utilizes for the embodiment of the invention.

The resonance length of microstrip antenna mainly is to decide by Route Length, so it is very little that the width of circuit relies on the condition of resonance, must consider to come the radiation of part since then as the action of antenna, though and that the electromagnetic field of antenna of the present invention is enclosed in the microstripline is good, but the electric field from antenna end can spread down laterally, also promptly utilize the reverse of magnetic current each other, make the electric field of its radiation and the electric field of former existence reach the effect of cancelling out each other.

Please refer to shown in Figure 3ly, it is that the electromagnetic field of the embodiment of the invention is offset and leakage field intensity schematic diagram.

The present invention is by antenna 20, this antenna 20 can be microstrip antenna (Microstrip antenna) or stripline antenna (Stripline antenna), be used to launch the electromagnetic wave of phase shift, wherein the scope of phase difference can produce the phase shift degree different from 90 ° to 180 ° according to the design of phase shifter 10 circuits.This differential wave is under the prerequisite that does not undermine signal quality, can reach the purpose of magnetic field cancellation and field coupled according to right hand Ampere's law, wherein is the sense of current (referring to into paper) of antenna 20, ⊙ is the sense of current (pointing out paper) by the noise assembly, so under the near field, offset most electromagnetic field 30, having only a spot of leakage field intensity (stray fringingfields) 40 can be emitted to the far field becomes plane wave, can significantly reduce electromagnetic radiation like this.

The pattern of phase shifter of the present invention can be selected from pattern any of the existing phase shifter among Fig. 4 A-4H.Orthoscopic delay line type (Straight delay line) comprising Fig. 4 A, the dioptric type delay line type of Fig. 4 B (Meander-line delay line), the T formula of Fig. 4 C engages phase type (T-junctionphase), the serial connection phase type of Fig. 4 D (Series phase), the serial connection PIN phase type of Fig. 4 E (Series PINdiode phase), the shunting phase type of Fig. 4 F (Shunt phase), the ferroelectricity phase type patterns such as (Ferroelectric phase) of the shunting PIN phase type of Fig. 4 G (ShuntPIN diode phase) and Fig. 4 H.

Though the present invention is disclosed with aforesaid preferred embodiment; yet it is not in order to limit the present invention; any those of ordinary skill in the art are under the situation that does not break away from spirit of the present invention; also can make all equivalences and change and the equivalence replacement, so protection scope of the present invention should be with being as the criterion that accompanying claims were defined.

Claims

1. An electromagnetic interference canceling circuit with a phase-shifting unit, which is arranged on an electronic device, is characterized in that the electromagnetic interference canceling circuit at least includes:

A phase shifting unit, the phase shifting unit is connected with a signal extraction terminal, used to receive the signal of the signal extraction terminal, and generate a cancellation signal after phase shifting; and

An antenna, which is connected with the phase-shifting unit, is used to receive the cancellation signal and emit phase-shifted electromagnetic waves to generate magnetic field cancellation and electric field coupling.

2. The electromagnetic interference canceling circuit with a phase shifting unit as claimed in claim 1, wherein the canceling signal is a false signal after being phase-shifted by the phase shifter.

3. The EMI cancellation circuit with a phase shift unit as claimed in claim 1, wherein the phase shift unit is a phase shifter.

4. The electromagnetic interference canceling circuit with a phase shift unit as claimed in claim 1, wherein the signal acquisition terminal is a trace of a printed circuit board.

5. The EMI cancellation circuit with a phase shift unit as claimed in claim 1, wherein the signal acquisition terminal is an integrated circuit.

6. The EMI cancellation circuit with a phase shift unit as claimed in claim 1, wherein the signal acquisition terminal is an oscillator.

7. The EMI cancellation circuit with a phase shift unit as claimed in claim 1, wherein the signal acquisition terminal is a crystal component.

8. The EMI cancellation circuit with a phase shift unit as claimed in claim 1, wherein the antenna is a microstrip antenna.

9. The electromagnetic interference canceling circuit with a phase shift unit as claimed in claim 1, wherein the antenna is a strip line antenna.

10. The electromagnetic interference canceling circuit with phase shifting unit as claimed in claim 3, characterized in that, the type of the phase shifter can be selected from linear delay line type, zigzag delay line type, T-type junction phase type, One of series phase type, series PIN phase type, shunt phase type, shunt PIN phase type and ferroelectric phase type.

11. An electromagnetic interference canceling circuit with a phase shifting unit is arranged on an electronic device, the electromagnetic interference canceling circuit at least includes a phase shifting unit and an antenna, characterized in that:

The electromagnetic interference canceling circuit with a phase-shifting unit is connected to a signal extraction terminal for receiving a signal source of the signal extraction terminal, and uses an obtained electromagnetic interference harmonic to calculate a fundamental frequency, and the signal The source is upgraded to match the harmonics of the electromagnetic interference, and sent to the phase-shifting unit to generate a cancellation signal after phase-shifting, which is sent to the antenna, and the antenna is used to receive the cancellation signal and emit a phase-shifted electromagnetic wave to Generate magnetic field cancellation and electric field coupling.

12. The electromagnetic interference canceling circuit with a phase shifting unit as claimed in claim 11, wherein the canceling signal is a false signal after being phase-shifted by the phase shifter.

13. The EMI cancellation circuit with a phase shift unit as claimed in claim 11, wherein the phase shift unit is a phase shifter.

14. The EMI cancellation circuit with a phase shift unit as claimed in claim 11, wherein the signal acquisition terminal is a trace of a printed circuit board.

15. The electromagnetic interference canceling circuit with a phase shift unit as claimed in claim 11, wherein the signal acquisition terminal is an integrated circuit.

16. The EMI cancellation circuit with a phase shift unit as claimed in claim 11, wherein the signal acquisition terminal is an oscillator.

17. The electromagnetic interference canceling circuit with a phase shift unit as claimed in claim 11, wherein the signal acquisition terminal is a crystal component.

18. The EMI cancellation circuit with a phase shift unit as claimed in claim 11, wherein the antenna is a microstrip antenna.

19. The electromagnetic interference cancellation circuit with a phase shift unit as claimed in claim 11, wherein the antenna is a stripline antenna.

20. The electromagnetic interference cancellation circuit with phase shifting unit as claimed in claim 13, characterized in that, the type of the phase shifter can be selected from a linear delay line type, a zigzagging delay line type, a T-junction phase type, One of series phase type, series PIN phase type, shunt phase type, shunt PIN phase type and ferroelectric phase type.