CN113938147A

CN113938147A - Method for eliminating strong electromagnetic interference signal leaked by transmitter

Info

Publication number: CN113938147A
Application number: CN202111144835.0A
Authority: CN
Inventors: 孙玲玲; 孙文; 文进才; 李文钧
Original assignee: Hangzhou Dianzi University
Current assignee: Hangzhou Dianzi University
Priority date: 2021-09-28
Filing date: 2021-09-28
Publication date: 2022-01-14
Anticipated expiration: 2041-09-28
Also published as: CN113938147B

Abstract

The invention discloses a method for eliminating the strong electromagnetic interference signal leaked by the transmitter, by directly coupling to the reference signal from the output end of the transmitter. After the reference signal is orthogonally separated, an adjustable gain amplifier is used to adjust the delay to approximate the received signal with interference received by the receiving antenna. The received signal and the reference signal are superimposed to obtain a feedback signal, which is input into the integrator, and the integrator is used to track the correlation between the received signal and the reference signal. The output of the integrator acts on the adjustable gain amplifier to further adjust the reference signal. Until a cancellation signal with the same amplitude and opposite phase as the interfering signal is generated. After the cancellation signal is superimposed with the received signal, the interference signal can be eliminated. In the method, the front end of the low noise amplifier and the back end of the receiving antenna in the whole receiver chain can cancel the electromagnetic interference signal, which can avoid the saturation of the back end circuit.

Description

Method for eliminating strong electromagnetic interference signal leaked by transmitter

Technical Field

The invention belongs to the technical field of electromagnetic fields, relates to a method for counteracting anti-electromagnetic interference signals, and particularly relates to a method for eliminating strong electromagnetic interference signals leaked by a transmitter.

Background

In an environment of strong electromagnetic leakage, there is a leakage signal from the transmitter in addition to the signal from the target for the receiver. The electromagnetic interference signal leaks by the following mechanisms: (1) coupling through a substrate of a chip; (2) coupling caused by chip-antenna interconnects; (3) mutual coupling between the transmitting and receiving antennas. For a compact transmit receive type module: the isolation between transmitter and receiver can be reasonably set to 30dB, assuming a transmitter output power of 10dBm, then-20 dBm of signal power is received at the input of the receiver. In this case, the power of the interference signal of the electromagnetic leakage may be several orders of magnitude higher than the power of the received target signal. High power electromagnetic interference signals limit the linearity and resolution of the receiver of the ADC, resulting in increased circuit area and increased power consumption.

Therefore, it is of great significance to shield or eliminate electromagnetic interference signals between the transmitter and the receiver. Common emi cancellation circuits can be divided into passive circuits and active circuits. The passive circuit has high linearity when electromagnetic interference signals are counteracted, and the influence on the performance of the receiver is small. The main disadvantage is that the size and power consumption are too large to be integrated in a large-capacity CMOS. The active circuit has more flexibility and smaller occupied area, and can be easily integrated in batch CMOS. However, receiver performance may be degraded due to noise and distortion of the active devices. There are several different options for the location of the emi cancellation circuit in the receiver chain. Such as directly after the antenna, after a Low Noise Amplifier (LNA), after baseband down conversion. These solutions have respective advantages and disadvantages: close to the antenna can reduce the linearity requirements and thus reduce power consumption, but at the same time also increases the Noise Figure (NF), compared to a connection close to the baseband which has little effect on the NF, but before the cancellation point all modules need a high linearity to process the received signal and the overflow without compression, which means a higher power consumption. It is more challenging than the way that the vanishing point is behind the rf antenna.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for eliminating strong electromagnetic interference signals leaked by a transmitter, which is characterized in that signals on a receiving link are associated with sampling signals of the transmitted signals on the basis of the known condition of the transmitted signals at a receiving end, then the delay of the sampling signals is adjusted to match the delay of the leaked electromagnetic interference signals, then the overflow is cancelled by using the superposition result of the two signals, and the electromagnetic interference is cancelled after a receiving antenna and before a low-noise amplifier.

A method for eliminating strong electromagnetic interference signals leaked by a transmitter specifically comprises the following steps:

step one, using a receiving antenna to receive a signal transmitted by a transmitter to obtain a signal I with interference, and amplifying the signal I into an input signal I through an amplifier₁。

Step two, directly coupling the output end of the transmitter by using a coupler to obtain a sampling signal I₂Then sampling the signal I₂Are decomposed into orthogonal signals with equal amplitude and 90-degree phase difference.

Step three, respectively inputting the two paths of orthogonal signals obtained in the step two into an adjustable gain amplifier to obtain A_IAnd A_QThen, the signals are superposed through an adder to obtain a reference signal I₃Wherein the reference signal I₃Amplitude of

Phase I_3p＝arctan(A_Q/A_I)。

Step four, reference signal I₃And an input signal I₁The feedback signal I is obtained by adding the adder₄. A feedback signal I₄Input into the integrator.

Step five, continuously adjusting the output of the adjustable gain amplifier so as to change the reference signal I₃Until the output of the integrator is 0, a cancellation signal I with the same amplitude and the opposite phase as the interference signal is obtained₃₀。

Step six, the cancellation signal I obtained in the step five is used₃₀And an input signal I₁And after the signals are superposed by the adder, an output signal P is obtained and is input to a low noise amplifier of the receiver, so that the elimination of the electromagnetic interference signal is completed.

The invention has the following beneficial effects:

1. the electromagnetic interference signals are offset at the front end of the low-noise amplifier and the rear end of the receiving antenna in the whole receiver link, so that the saturation of the rear end circuit can be avoided.

2. And a negative feedback closed loop is designed, the correlation between the reference signal and the interference signal is judged through the integral result of the feedback signal after superposition, the calculation is simple, the amplitude and the phase of the reference signal can be adjusted in a self-adaptive manner, and the cancellation of the interference signal is realized.

Drawings

FIG. 1 is a schematic diagram of interference signal cancellation according to the present method;

FIG. 2 is a flow chart of reference signal adjustment in the present method.

Detailed Description

The invention is further explained below with reference to the drawings;

as shown in fig. 1, a method for eliminating a strong electromagnetic interference signal leaked by a transmitter specifically includes the following steps:

Step two, directly coupling the output end of the transmitter by using a coupler to obtain a sampling signal I₂Because of the sampling signal I₂Is directly coupled from the transmitter end of the transmitter, thus sampling the signal I₂Is known as to amplitude and phase. Then sampling the signal I₂Are decomposed into orthogonal signals with equal amplitude and 90-degree phase difference.

Phase I_3p＝arctan(A_Q/A_I)。

Step five, as shown in fig. 2, continuously adjusting the output of the adjustable gain amplifier, thereby changing the reference signal I₃Until the input of the integrator is constant and does not change any more in the feedback loop, the output of the integrator is 0, the negative feedback regulation is finished, and the cancellation signal I with the same amplitude and the opposite phase as the interference signal is obtained₃₀。

Claims

1. a method for eliminating the strong electromagnetic interference signal leaked by a transmitter, is characterized in that: the method comprises the following steps:

Step 1, the receiving antenna receives the signal I with interference, and obtains the input signal I ₁ with interference after being amplified by the amplifier;

Step 2, using a coupler to directly couple the sampling signal I ₂ from the output end of the transmitter, and then decompose the sampling signal I ₂ into two quadrature signals with equal amplitude and 90° phase difference;

Step 3: Input the two orthogonal signals obtained in step 2 into the adjustable gain amplifier to obtain AI and A _Q respectively, and obtain the reference signal _I ₃ after superposition;

Step 4, superimpose the reference signal I ₃ and the input signal I ₁ to obtain the feedback signal I ₄ ; Input the feedback signal I ₄ into the integrator;

Step 5: Adjust the amplitude and phase of the reference signal _I3 , until the output of the integrator is 0, and obtain a cancellation signal _I30 that is equal in amplitude and opposite to the interference signal;

Step 6: After the cancellation signal I ₃₀ obtained in Step 5 is superimposed with the input signal I ₁ , an output signal P is obtained, and the output signal P is input to the low noise amplifier of the receiver to complete the elimination of the electromagnetic interference signal.

2. a kind of method that eliminates the strong electromagnetic interference signal that transmitter leaks as claimed in claim 1, it is characterized in that: by changing the gain multiple of adjustable gain amplifier, change the size of AI and A _Q , thereby change reference signal _I The magnitude and phase size of ₃ .

3. a kind of method for eliminating the strong electromagnetic interference signal leaked by transmitter as described in claim 1 or 2, is characterized in that: wherein the amplitude of reference signal I ₃

Phase I _3p = arctan(A _Q /A _I ).