CN105553511B - A kind of multiband ultra-wideband system disturbance restraining method based on Sqrt Chirp pulses - Google Patents

Abstract

A multi-band positive interactive complement ultra-wideband system interference suppression method based on nonlinear Sqrt Chirp pulses. The UWB frequency band is divided at the sending end to obtain L different sub-bands. According to whether there is a narrow-band interference signal in each sub-band And setting the corresponding Chirp pulse can realize high-speed and multi-rate transmission. The present invention designs and adopts the nonlinear Sqrt Chirp pulse in the sub-frequency band where the narrow-band interference signal exists, which can pass through the frequency band where the narrow-band interference is located at the maximum instantaneous frequency, suppresses the influence of the narrow-band interference more effectively, and simultaneously realizes the suppression of multiple narrow-band interferences. Based on the good correlation characteristics of positive interactive complement code, the present invention performs spread spectrum modulation on each sub-band Chirp pulse, which can eliminate multiple access interference between users, inter-sub-band interference and multipath interference, and realize simultaneous suppression and Eliminate, effectively improve the anti-interference ability and communication performance of the system.

Description

An Interference Suppression Method for Multi-Band UWB System Based on Sqrt Chirp Pulse

technical field

The invention relates to a method for suppressing interference of a multi-band positive interactive complement ultra-wideband system based on nonlinear Sqrt Chirp pulses, and belongs to the technical field of wireless communication.

Background technique

Ultra-wideband (UWB) technology has attracted more and more attention from academia and industry because of its low transmission power, easy implementation, strong anti-interference ability and high multipath resolution. UWB technology can provide high-speed and reliable data transmission between portable electronic devices and communication devices within a relatively short distance. The above characteristics make UWB technology have broad application prospects in wireless communication, radar, precise positioning and other fields, especially in indoor short-distance high-speed wireless communication with incomparable advantages.

The extremely wide bandwidth and extremely low transmission power of UWB signals determine that it will inevitably be interfered by other narrowband communication systems. Therefore, narrowband interference (NBI) suppression technology must be used to solve the coexistence problem of ultra-wideband systems and narrowband systems. It is also one of the research hotspots of UWB technology. At present, there have been many achievements in the research on the influence of narrowband interference on UWB systems and the research on suppression methods. H.B.Shen et al. (see H.B.Shen, W.H.Zhang, and K.S.Kwak, "Modified chirp waveforms in cognitive UWB system," in Proc.ICC Workshops'08, pp.504-507, May.2008.) adopted the idea of spectrum avoidance to design non- Linear Chirp pulse to suppress narrowband interference. Based on the characteristics of the Chirp function, the above method only needs to be processed in the time domain to change the corresponding frequency domain characteristics, so as to achieve the purpose of suppressing narrowband interference, but only considers the suppression of single narrowband interference. W.Liu et al. (see W.Liu, W.X.Zou and F.M.Xu, et al, "A Novel Frequency-band Coded Orthogonal UWB Chirp Pulse Design for Cognitive NBI Suppression," Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, pp.1048- 1051,2007) Divide the UWB frequency band into many sub-bands, and use the pseudo-random (PN) sequence to encode the sub-bands, so that the Chirp pulses of the sub-bands are orthogonal, thereby avoiding interference between multiple users. The above method uses PN codes, but to make the chirp pulses of each sub-band of each user have orthogonality, the system design will be complicated and the multipath interference of the system cannot be effectively reduced. C.Wang et al. (See C.Wang, M.D.Ma, R.D.Ying and Y.H.Yang, “Narrowband Interference Mitigation in DS-UWB systems,” IEEE Signal Processing Letters, vol.17, no.5, pp.429-432, 2010.) For the first time, the code-assisted interference suppression technology was introduced into the Direct Sequence Spread Spectrum Ultra-Wideband (DS-UWB) system, and a new spread spectrum sequence for suppressing narrowband interference was proposed, but the operation process to obtain the sequence was complicated. The spreading codes used in traditional DS-UWB systems are all single codes (such as m-sequence, Walsh code, Gold sequence, etc.), and research shows that single codes cannot have ideal autocorrelation and cross-correlation characteristics at the same time, so based on single code The UWB system has limited anti-interference ability. The positive interactive complementary code used in the present invention is a composite code sequence different from single codes, which is composed of a group of element codes and has ideal correlation characteristics, that is, the sidelobe of the autocorrelation function and the cross-correlation function are all zero. Due to the ideal correlation characteristic of the orthogonal complement code, it has been widely concerned and researched in the CDMA system. H.H.Chen and others have studied the CDMA system based on positive interactive complement code (see H.H.Chen, S.W.Chua and M.Guizani, "On next generation CDMA technologies: The REAL approach for perfectorthogonal code generation," IEEE Trans.on Vehicular Technology, vol.57 , pp.2822-2833, 2007), which can completely eliminate multipath and multiple access interference, and can realize multi-rate transmission by using a stack offset (OS) modulation scheme. Existing UWB systems lack design flexibility in terms of anti-multi-narrowband interference, multipath and multiple access interference, and it is difficult to simultaneously suppress and eliminate the above-mentioned typical interference.

Contents of the invention

Aiming at the defects and deficiencies of the existing technical solutions, the present invention provides a multi-band positive interactive complement ultra-wideband system interference suppression method based on nonlinear SqrtChirp pulses. This method divides the UWB frequency band reasonably, which is beneficial to realize narrowband Interference suppression, while improving system transmission efficiency, and the OCC UWB system using parallel transmission mode can increase system transmission rate and realize multi-rate transmission while suppressing multipath and multiple access interference.

Technical scheme of the present invention is as follows:

A method for suppressing interference in an ultra-wideband system based on non-linear Sqrt Chirp pulses, wherein the ultra-wideband system includes a group of transmitting nodes and a single destination terminal, wherein the transmitting node group contains a plurality of transmitting nodes, Each transmitting node corresponds to a user, and it and the destination terminal are equipped with a single antenna, and the transmitting node sends multi-user signals to the destination terminal through a wireless multipath channel; the signal received by the destination terminal comes from the useful signal sent by the transmitting node group, other UWB user signal, and multi-narrowband interference signal, sub-band interference signal, multipath signal and Gaussian white noise signal existing in the channel environment, the specific steps of described interference suppression method are as follows:

A. The UWB communication system is ready to start working;

B. The UWB communication system uses spectrum sensing technology to obtain the frequency band (f _l(j) , f _h(j) ) and the corresponding center frequency f _(j) of the multi-narrowband interference signal in the communication environment, j∈(1,2, ..., N), f _l(j) and f _h(j) are the lower limit frequency and upper limit frequency of the jth narrowband interference signal respectively, and N is the number of narrowband interference signals in the communication environment;

C, according to the frequency band position of the narrowband interference signal, the bandwidth of the available frequency band of the UWB communication system is divided into L sub-frequency bands, each sub-frequency band is assigned an OCC code, and a corresponding Chirp pulse w _i (t) is matched and set for each sub-frequency band ), i∈(1,2,…,L), and L>N;

D. Assuming that there are K users in the UWB communication system, {C ¹ , C ² ,…, C ^K } is an orthogonal complementary sequence set, and the OCC of the kth user is M is the number of OCC metacodes of the kth user, each metacode Contains N _c chips, that is, spreads each sub-band by using an OCC code;

E. According to the number of sub-bands, the data bits are transmitted in groups of L bits, converted into L branches through serial parallel transmission and transmitted in parallel on the corresponding L sub-bands; each branch is subjected to OCC spread spectrum, and then determined with The Chirp pulses of the respective frequency bands are multiplied, and the Chirp pulses modulated by the spreading code for each bit are represented as in For the nth data bit transmitted by the kth user, is the j-th chip of the i-th element code of user k; assuming the first user is the expected user, the time delay between the last arrival path of the second to k-th users and the first arrival path of the first user is τ=ηT _c +ζ, where ζ is uniformly distributed in [0,T _c ], T _c is the duration of each chip, and the duration of each metacode is T _p =(N _c +n+1)T _c ;

F. The source sends data bits, and the data bits are represented by Chirp pulses modulated by OCC spread spectrum. The data bits are transmitted through L parallel branches, and then all the transmitted signals are superimposed together and transmitted through the antenna to enter the multi-path channel transmission. In addition to path fading, the narrowband system coexisting with the UWB system, other user UWB signals in the UWB communication system, and additive Gaussian white noise interfere with the desired user's UWB signal and appear together in the received signal;

G. At the receiving end, the Rake receiver is used to process the received signal r(t) in each sub-band. The Rake receiver includes F correlators, and the correlator compares the received signal r(t) with the template signal m(t) Integrate the product of ;

H. In the l sub-band, correlate the received signal r(t) with the corresponding template signal m(t), and the output decision variable is Z _l , Z _l = S _U + S _I + S _M + S _P + S _F +S _n , where S _U is the useful signal component, S _I is the narrowband interference component, S _M is the multiple access interference component, S _P is the multipath interference component, S _F is the sub-band interference item, and S _n is the additive Gaussian white noise term;

1, according to the above steps, obtain the output decision variable Z _k1 of the Rake receiver in the 1st sub-band of user k, adopt the maximum likelihood criterion to judge, and obtain the average error probability expression of this UWB communication system as:

in F is the number of branches of the Rake receiver, the number of its correlators is the same as the number of branches of the Rake receiver, w _f is the weighting factor of the fth correlator, P(Z _kl <0|'1') refers to the transmitted symbol The probability that 1 is misjudged as 0, P(Z _kl >0|'0') refers to the probability that the transmitted symbol is 0 and is misjudged as 1;

J. When the data bits are sent, the communication ends.

Preferably according to the present invention, the method of setting a corresponding Chirp pulse w _i (t) for each sub-band matching in the step C is specifically as follows:

1) Use spectrum sensing technology to detect narrow-band interference frequency bands. A narrow-band interference signal is set. At this time, the UWB frequency band (f _l , f _h ) is divided into three segments, namely (f _l , f ₁ ), (f ₁ , f ₂ ) and (f ₂ , f _h ), f _l and f _h are the lower limit frequency and upper limit frequency of the UWB frequency band respectively, the bandwidth of each sub-frequency band is greater than 500MHZ, and the narrow-band interference signal is located in the second sub-frequency band (f ₁ , f ₂ ) Inside;

2) In the i-th (i=1,3) sub-band without narrow-band interference signals, a linear Chirp pulse w _i (t)=p(t)cos[2π(f ₀ + iB _i )t+πμt ² ], p(t) is the envelope of each sub-band and p(t)=0 when |t|>T/2, T is the signal period, μ is the frequency sweep rate, B _i is the bandwidth of the i-th sub-band;

3) In the sub-band (f ₁ , f ₂ ) where narrow-band interference signals exist, design a nonlinear Chirp pulse that can effectively suppress narrow-band interference: in this sub-band, according to the time-frequency mapping relationship of the Chirp pulse, the narrow-band interference The time point corresponding to the signal lower limit frequency f _l(1) is T _fra =T(f _l(1) -f ₁ )/B', B'=(f ₂ -f ₁ )-(f _h(1) -f _l(1) ) is the modified frequency bandwidth, and the time-frequency correspondence of Chirp pulses is as follows: (0,T _fra )→(f ₁ ,f _l(1) ), (T _fra ,T)→(f _{h(1 )} , f ₂ ); the above is equivalent to removing the narrowband interference signal frequency band to achieve narrowband interference suppression.

Preferably according to the present invention, after step 3), in order to further make the pulse pass through the sideband of the narrowband interference signal with the maximum instantaneous frequency to realize more effective interference suppression, the instantaneous frequency of the nonlinear Chirp pulse can be corrected as :

The time-domain expression of the nonlinear Sqrt Chirp pulse is obtained by integrating the instantaneous frequency:

Advantage of the present invention is as follows:

1. The present invention divides the UWB frequency band at the sending end to obtain L different sub-frequency bands. According to whether there is narrow-band interference signal matching and setting corresponding Chirp pulses in each sub-frequency band, high-speed and multi-rate transmission can be realized.

2. The present invention designs and adopts the nonlinear Sqrt Chirp pulse in the sub-band where the narrowband interference signal exists, which can pass through the frequency band where the narrowband interference is located at the maximum instantaneous frequency, more effectively suppress the influence of the narrowband interference, and realize the suppression of multiple narrowband interferences at the same time .

3. The present invention is based on the good correlation characteristics of the positive interactive complement code, and performs spread spectrum modulation on each sub-band Chirp pulse, which can eliminate multiple access interference between users, inter-sub-band interference and multipath interference, and realize multiple interferences at the same time Suppression and elimination, effectively improving the anti-interference ability and communication performance of the system.

Description of drawings

Fig. 1 is the structural representation of the ultra-wideband system involved in the present invention, wherein: 1, transmitting node group; 2, wireless multi-path channel; 3, destination terminal;

Fig. 2 is the block flow diagram of interference suppression method of the present invention: wherein A-J is each step;

Fig. 3 is a flow chart of the construction of a corresponding Chirp sub-pulse w _i (t) matched to each sub-band in step C of the interference suppression method of the present invention, wherein (1)-(3) are the respective steps.

Detailed ways:

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but is not limited thereto.

As shown in Figure 1-3.

Embodiment 1,

A method for suppressing interference in a multi-band positive interactive complement ultra-wideband system based on nonlinear Sqrt Chirp pulses, wherein the ultra-wideband system includes a group of transmitting nodes and a single destination terminal 3, wherein the transmitting node group 1 contains multiple transmitting Node, each transmitting node corresponds to a user, and a single antenna is set up between it and the destination terminal, and the transmitting node sends multi-user signals to the destination terminal through the wireless multipath channel 2; the signal received by the destination terminal comes from the useful signal sent by the transmitting node group signal, other UWB user signals, and multi-narrowband interference signals, sub-band interference signals, multipath signals and Gaussian white noise signals that exist in the channel environment, the specific steps of the interference suppression method are as follows:

A. The UWB communication system is ready to start working;

B. The UWB communication system uses spectrum sensing technology to obtain the frequency band (f _l(j) , f _h(j) ) and the corresponding center frequency f _(j) of the multi-narrowband interference signal in the communication environment, j∈(1,2, ..., N), f _l(j) and f _h(j) are the lower limit frequency and upper limit frequency of the jth narrowband interference signal respectively, and N is the number of narrowband interference signals in the communication environment;

C, according to the frequency band position of the narrowband interference signal, the bandwidth of the available frequency band of the UWB communication system is divided into L sub-frequency bands, each sub-frequency band is assigned an OCC code, and a corresponding Chirp pulse w _i (t) is matched and set for each sub-frequency band ), i∈(1,2,…,L), and L>N;

D. Assuming that there are K users in the UWB communication system, {C ¹ , C ² ,…, C ^K } is an orthogonal complementary sequence set, and the OCC of the kth user is M is the number of OCC meta-codes of the kth user, and each meta-code C _m ^k contains N _c chips, that is, the OCC code is used to spread each sub-band;

E. According to the number of sub-bands, the data bits are transmitted in groups of L bits, converted into L branches through serial parallel transmission and transmitted in parallel on the corresponding L sub-bands; each branch is subjected to OCC spread spectrum, and then determined with The Chirp pulses of the respective frequency bands are multiplied, and the Chirp pulses modulated by the spreading code for each bit are represented as in For the nth data bit transmitted by the kth user, is the j-th chip of the i-th element code of user k; assuming the first user is the expected user, the time delay between the last arrival path of the second to k-th users and the first arrival path of the first user is τ=ηT _c +ζ, where ζ is uniformly distributed in [0,T _c ], T _c is the duration of each chip, and the duration of each metacode is T _p =(N _c +n+1)T _c ;

F. The source sends data bits, and the data bits are represented by Chirp pulses modulated by OCC spread spectrum. The data bits are transmitted through L parallel branches, and then all the transmitted signals are superimposed together and transmitted through the antenna to enter the multi-path channel transmission. In addition to path fading, the narrowband system coexisting with the UWB system, other user UWB signals in the UWB communication system, and additive Gaussian white noise interfere with the desired user's UWB signal and appear together in the received signal;

G. At the receiving end, the Rake receiver is used to process the received signal r(t) in each sub-band. The Rake receiver includes F correlators, and the correlator compares the received signal r(t) with the template signal m(t) Integrate the product of ;

H. In the l sub-band, correlate the received signal r(t) with the corresponding template signal m(t), and the output decision variable is Z _l , Z _l = S _U + S _I + S _M + S _P + S _F +S _n , where S _U is the useful signal component, S _I is the narrowband interference component, S _M is the multiple access interference component, S _P is the multipath interference component, S _F is the sub-band interference item, and S _n is the additive Gaussian white noise term;

1, according to the above steps, obtain the output decision variable Z _k1 of the Rake receiver in the 1st sub-band of user k, adopt the maximum likelihood criterion to judge, and obtain the average error probability expression of this UWB communication system as:

in F is the number of branches of the Rake receiver, the number of its correlators is the same as the number of branches of the Rake receiver, w _f is the weighting factor of the fth correlator, P(Z _kl <0|'1') refers to the transmitted symbol The probability that 1 is misjudged as 0, P(Z _kl >0|'0') refers to the probability that the transmitted symbol is 0 and is misjudged as 1;

J. When the data bits are sent, the communication ends.

Embodiment 2,

A kind of non-linear Sqrt Chirp pulse-based multi-band positive interactive complement ultra-wideband system interference suppression method as described in Embodiment 1, the difference is that in the step C, each sub-band matching sets a corresponding Chirp pulse w The method of _i (t) is as follows:

1) Use spectrum sensing technology to detect narrow-band interference frequency bands. A narrow-band interference signal is set. At this time, the UWB frequency band (f _l , f _h ) is divided into three segments, namely (f _l , f ₁ ), (f ₁ , f ₂ ) and (f ₂ , f _h ), f _l and f _h are the lower limit frequency and upper limit frequency of the UWB frequency band respectively, the bandwidth of each sub-frequency band is greater than 500MHZ, and the narrow-band interference signal is located in the second sub-frequency band (f ₁ , f ₂ ) Inside;

2) In the i-th (i=1,3) sub-band without narrow-band interference signals, a linear Chirp pulse w _i (t)=p(t)cos[2π(f ₀ + iB _i )t+πμt ² ], p(t) is the envelope of each sub-band and p(t)=0 when |t|>T/2, T is the signal period, μ is the frequency sweep rate, B _i is the bandwidth of the i-th sub-band;

3) In the sub-band (f ₁ , f ₂ ) where narrow-band interference signals exist, design a nonlinear Chirp pulse that can effectively suppress narrow-band interference: in this sub-band, according to the time-frequency mapping relationship of the Chirp pulse, the narrow-band interference The time point corresponding to the signal lower limit frequency f _l(1) is T _fra =T(f _l(1) -f ₁ )/B', B'=(f ₂ -f ₁ )-(f _h(1) -f _l(1) ) is the modified frequency bandwidth, and the time-frequency correspondence of Chirp pulses is as follows: (0,T _fra )→(f ₁ ,f _l(1) ), (T _fra ,T)→(f _{h(1 )} , f ₂ ); the above is equivalent to removing the narrowband interference signal frequency band to achieve narrowband interference suppression.

Embodiment 3,

A kind of non-linear Sqrt Chirp pulse-based method for suppressing interference in a multi-band positive interactive complement ultra-wideband system as described in Embodiment 2, the difference is that after step 3), in order to further make the pulse pass through the narrowband with the maximum instantaneous frequency At the sideband of the interference signal, to achieve more effective interference suppression, the Sqrt operation can be used to correct the instantaneous frequency of the nonlinear Chirp pulse as:

The time-domain expression of the nonlinear Sqrt Chirp pulse is obtained by integrating the instantaneous frequency:

Claims (2)

1. a multi-band orthogonal complementary code ultra-wideband system interference suppression method based on nonlinear Sqrt Chirp pulses is characterized by comprising the following steps:

A. the UWB communication system is ready to begin operation;

B. the UWB communication system obtains frequency bands (f) where multiple narrow-band interference signals are located in the communication environment _l(j) ,f _h(j) ) And corresponding center frequency f _(j) ，j∈(1,2,…,N)，f _l(j) And f _h(j) Lower limit of jth narrow-band interference signal respectivelyFrequency and upper limit frequency, N is the number of narrow-band interference signals in the communication environment;

C. the bandwidth of an available frequency band of the UWB communication system is divided into L sub-bands according to the frequency band position of the narrow-band interference signal, each sub-band is allocated with an OCC code, and each sub-band is matched and provided with a corresponding Chirp pulse w _i (t), i ∈ (1, 2, \8230;, L), and L>N；

D. Let UWB communication system have K users altogether, { C ¹ ,C ² ,…,C ^K Is an orthogonal complementary sequence set, the OCC of the kth user isM is the number of element codes of OCC of the kth user, and each element codeContaining N _c Spreading each sub-band by using OCC codes;

E. according to the number of the sub-frequency bands, data bits are transmitted in groups of L bits, converted into L branches in a serial-parallel mode and transmitted in parallel on the corresponding L sub-frequency bands; OCC (orthogonal code division multiplexing) is carried out on each branch, and then each branch is multiplied by a Chirp pulse determining respective frequency band, and the Chirp pulse modulated by each bit through a spreading code is characterized by beingWhereinThe nth data bit sent for the kth user,is the jth code chip of the ith element code of the user k; let 1 st user be the desired user, and the time delay between the last arrival path of 2 nd to kth users and the first arrival path of 1 st user be τ = η T _c + ζ of whichZeta is uniformly distributed over 0, T _c ]，T _c Is the duration of each chip, and the duration of each element code is T _p ＝(N _c +η+1)T _c ；

F. The method comprises the steps that an information source sends data bits, the data bits are represented through Chirp pulses modulated by OCC spread spectrum, the data bits are transmitted through L parallel branches, then all sending signals are superposed together and transmitted into a multi-path channel through an antenna, and except for multi-path fading, other user UWB signals and additive white Gaussian noise in a narrow-band system and a UWB communication system which coexist with a UWB system generate interference on UWB signals of an expected user and commonly appear in a receiving signal;

G. at a receiving end, processing a received signal r (t) in each sub-frequency band by adopting a Rake receiver, wherein the Rake receiver comprises F correlators, and the correlators integrate the product of the received signal r (t) and a template signal m (t);

H. in the first sub-band, the received signal r (t) is correlated with the corresponding template signal m (t), and the output decision variable is Z _l ，Z _l ＝S _U +S _I +S _M +S _P +S _F +S _n In which S is _U Is a useful signal component, S _I As narrow-band interference components, S _M For multiple access interference components, S _P As a multipath interference component, S _F For the sub-band interference term, S _n Is an additive white gaussian noise term;

I. according to the steps, the output decision variable Z of the Rake receiver in the ith sub-band of the user k is obtained _kl And judging by adopting a maximum likelihood criterion to obtain an average error probability expression of the UWB communication system, wherein the average error probability expression is as follows:

whereinF is Rake receptionThe number of branches of the machine, the number of correlators of which is the same as the number of branches of the Rake receiver, w _f As a weighting factor for the f-th correlator, P (Z) _kl &lt 0| '1') refers to the probability that a transmitted symbol is 1 and is misjudged to be 0, P (Z) _kl &gt 0| '0') refers to the probability that a transmission symbol is 0 and is misjudged as 1;

J. when the data bit is sent, the communication is finished;

and C, setting a corresponding Chirp pulse w for each sub-band in the step C in a matching manner _i The method (t) is specifically as follows:

1) Detecting a narrow-band interference band, providing a narrow-band interference signal, in which case the UWB band (f) is detected _l ,f _h ) Divided into three sections, i.e. (f) _l ,f ₁ )、(f ₁ ,f ₂ ) And (f) ₂ ,f _h )，f _l And f _h Respectively the lower limit frequency and the upper limit frequency of the UWB band, each sub-band bandwidth is more than 500MHZ, and a narrow-band interference signal is arranged in the 2 nd sub-band (f) ₁ ,f ₂ ) Internal;

2) In the ith (i =1, 3) sub-band without narrow-band interference signal, a linear Chirp pulse w with the waveform center at t =0 is adopted _i (t)＝p(t)cos[2π(f ₀ +iB _i )t+πμt ² ]P (t) is the envelope of each sub-band and when | t & gtis not charging&T/2, p (T) =0, T is signal period, mu is sweep frequency rate, B _i Is the bandwidth of the ith sub-band;

3) In a sub-band (f) where a narrow-band interfering signal is present ₁ ,f ₂ ) In the method, a nonlinear Chirp pulse for effectively inhibiting narrow-band interference is designed: in the sub-frequency band, the lower limit frequency f of the narrow-band interference signal is obtained according to the time-frequency mapping relation of Chirp pulse _l(1) Corresponding time point is T _fra ＝T(f _l(1) -f ₁ )/B’，B’＝(f ₂ -f ₁ )-(f _h(1) -f _l(1) ) For the corrected frequency bandwidth, the time-frequency corresponding relation of the Chirp pulse is as follows: (0,T) _fra )→(f ₁ ,f _l(1) )，(T _fra ,T)→(f _h(1) ,f ₂ ) (ii) a And 3) removing the narrow-band interference signal frequency band to realize narrow-band interference suppression.

2. The interference suppression method for the multiband orthogonal complementary code ultra-wideband system based on the nonlinear Sqrt Chirp pulse as claimed in claim 1, wherein after the step 3), the instantaneous frequency of the nonlinear Chirp pulse is corrected by using Sqrt operation as follows:

and integrating the instantaneous frequency to obtain a time domain expression of the nonlinear Sqrt Chirp pulse: