CN101222691B - Restraining method and circuit for double-module mobile phone channel selective disturbance - Google Patents

Abstract

The invention discloses a control method for selective interference of a dual mode mobile phone channel, including the following steps that: (1) a sampling frequency fs is set, a sampling pulse width(tau) is set based on fs, and a band rejection filter of which the rejection frequency takes fs as the center is set, wherein the sampling frequency meets the Nyquist sampling theorem and the bandwidth of the sampling frequency is more than or equal to the double bandwidth of sampled singles; the sampling pulse width(tau)=kxT1, k is a constant, T1 is a cycle of the sampling pulse; (2) when the level of the sampling pulse is the high level, a sampling switch is on; the sampling starts based on the set sampling frequency fs, the sampling data are picked up from continuous signals, and the signalaveraging of the sampling data is made by taking tau as the sampling time. A control circuit for selective interference of a dual mode mobile phone channel comprises the band rejection filter taking fs as the center, which is used to inhibit the weight of the interference mixed in a receiving end baseband frequency spectrum and a receiving end baseband demodulator circuit which is used to set thesampling frequency(fs) and the sampling pulse width(tau) and make the sampling and the signal averaging on signals outputted by the band rejection filter.

Description

Inhibition method that a kind of double-module mobile phone channel selective disturbs and inhibition circuit

Technical field

The present invention relates to the inhibition method and the inhibition circuit of the dual-mode handset radio frequency interference of wireless communication field.

Background technology

The GSM/CDMA dual-mode handset is a kind of emerging multifrequency and the mobile communication terminal of depositing, and it can support GSM, CDMA two cards standby simultaneously and even communication simultaneously.Yet the operating frequency of GSM900/1800MHz frequency range and CDMA800/1900MHz frequency range is closed on even is overlapping to some extent, can occur the situation of phase mutual interference inevitably.

Hold the frequency spectrum that is coupled into the cdma receiver front end with frequency range difference, watt level difference from GSM, the mode that worsens cdma receiver C/N is also different.High-power the transmitting of GSM transmitter has stronger blocking action to the cdma receiver front end; The out-of-band noise that the GSM transmitter produces drops on the carrier-to-noise ratio that part that CDMA receives frequency range has worsened the CDMA received signal.These all are the influence modes that common bimodulus disturbs.

Simultaneously we also find under study for action, and certain channel emission power of GSM900 can produce more significantly influence to the channel sensitivity apart from the CDMA Cellular frequency range of its fs, and this all has performance at present nearly all GSM/CDMA dual-mode handset.We are referred to as " the sampling spectral aliasing disturbs " to this problem that characteristic frequency channel is at interval had a significant effect.

The generation reason of this interference is: the transmitting power fg of GSM900 (t) is coupled to cdma receiver by antenna or other approach, because the effect of radio-frequency front-end nonlinear device, intrinsic frequency is carried out mixing in transmitting carrier frequency meeting and the cdma receiver.In zero intermediate frequency reciver, CDMA received RF local frequency fc (t) equals the receive channel centre frequency.Because the effect of frequency mixer, fg (t) and fc (t) produce the frequency content of mFg (ω)+n Fc (ω) at mixer output.m＝1，2，3，4…，n＝1，2，3，4…。

Along with the variation of GSM, CDMA Channel combination, the frequency that aliasing goes out also has nothing in common with each other, and these frequency components and CDMA baseband signal also suppress to some extent by low pass filter together.But because input-terminal disturbance signal is bigger, after filtering, still have-30～-magnitude of 50dBm (test value).The frequency component of mixing and baseband signal by low pass filter, are output as the IQ signal together, and the IQ line is promptly sampled and the A/D conversion after entering baseband processing chip.The sample frequency fs of A/D conversion is 16 frequencys multiplication of spreading rate, just 1.2288MHz * 16=19.6608MHz.

According to Nyquist (Nyquist) sampling theorem, accomplish frequency not aliasing to be limited in fs/2 with regard to the signal spectrum that requires to be input to sampling end be in the 9.8304MHz.In the wireless environment of routine, can accomplish this point substantially.But for the GSM/CDMA dual-mode handset, each frequency component that mixing goes out in cdma receiver is compared with faint CDMA signal also can be a lot of greatly.

On the I/Q line frequency spectrum as shown in Figure 1, useful signal occupied bandwidth ω c=1.23MHz, ω s, 2 ω s, 3 ω s places are operated in the spectrum component that the particular channel mixing produces for GSM and CDMA.If sample and the A/D conversion with the ideal period impulse sequence of fs=19.6608MHz speed, aliasing will appear in the frequency spectrum after the sampling.ω s, 2 ω s, 3 ω s ... the interference signal at n ω s place drops in the CDMA base band frequency range, and the aliasing schematic diagram is seen Fig. 2.Can carry out finite impulse response FIR filtering to sampled data after the A/D sampling, because the FIR filter has the outer suppression characteristic of precipitous band, the outer spectral aliasing of CDMA base band frequency range can leach by the FIR filter.In case interference signal is blended in the CDMA base band, just can't eliminates, thereby worsen the CDMA receiving sensitivity.

At present, for reducing the phase mutual interference of GSM/CDMA dual-mode handset, designers are devoted to improve the isolation between the antenna.The raising of isolation is for ensureing that the performance that bimodulus is conversed simultaneously is necessary.But this is not that positive effect is all arranged in all cases, such as this comparatively hidden interference type of our discovery.

Summary of the invention

The technical problem to be solved in the present invention provides the inhibition method that a kind of double-module mobile phone channel selective disturbs, and has solved in the existing dual-mode handset double modely when communicating by letter simultaneously, and side's transmitting power is to the problem that influences apart from the opposing party's of its fs receive channel sensitivity.

In order to address the above problem, the present invention proposes the inhibition method that a kind of double-module mobile phone channel selective disturbs, may further comprise the steps:

(1) the sample frequency fs of sampling pulse is set, according to this fs sampling pulse width τ is set, and blanketing frequency is set is the band stop filter at center with this fs, and described sample frequency satisfies the Nyquist sampling theorem, and more than or equal to the twice that is sampled signal bandwidth; Described sampling pulse width τ=k*T ₁, k is a constant, T1 is the cycle of sampling pulse;

(2) when the sampling pulse level is high level, open sampling switch, sample according to set sample frequency fs, from the signal of the output of band stop filter, extract sampled data, and to the signal averaging that is τ of this data time of carrying out.

Further, said method also can have following characteristics, and step (2) also comprises afterwards: the signal level that carry out after the signal averaging sampled data (3) is carried out A/D conversion, digital filtering, amplification, demodulation.

Said method also can have following characteristics, described band stop filter, be used to suppress to sneak into the interference components of receiving terminal baseband frequency spectrum, its blanketing frequency is the center with fs, be input as baseband I/Q signal that the receiver front end mixing produces, I+, I-are differential pairs, and Q+, Q-are differential pairs, and signal is to receiving terminal base band demodulating chip after the output filtering.

Further, said method also can have following characteristics, and described band stop filter adopts the LC form, comprises respectively between I+, I-holding wire the inductance and the electric capacity of serial or parallel connection being set between Q+, the Q-holding wire.

A kind of double-module mobile phone channel selective codan comprises receiving terminal base band demodulating circuit, it is characterized in that, also comprises band stop filter, wherein,

Described band stop filter, be used to suppress to sneak into the interference components of receiving terminal baseband frequency spectrum, its blanketing frequency is the center with fs, be input as baseband I/Q signal that the receiver front end mixing produces, I+, I-are differential pairs, Q+, Q-are differential pairs, and signal is to receiving terminal base band demodulating circuit after the output filtering;

Receiving terminal base band demodulating circuit is used to be provided with sample frequency fs and sampling pulse width τ, the signal of described band stop filter output is sampled, and being τ to this sampled data time of carrying out, continuous signal is average; Described sample frequency satisfies the Nyquist sampling theorem, and more than or equal to the twice that is sampled signal bandwidth, described sampling pulse width τ=k*T ₁, k is a constant, T1 is the cycle of sampling pulse.

Further, foregoing circuit also can have following characteristics, and receiving terminal base band demodulating circuit comprises that sampling is provided with the unit, and the unit is opened in sampling, and integral unit is extracted in sampling; Sampling is provided with the unit, is used to be provided with the sample frequency fs and the sampling pulse width τ of sampling pulse; Described sample frequency satisfies the Nyquist sampling theorem, and more than or equal to the twice that is sampled signal bandwidth, described sampling pulse width τ=k*T ₁, k is a constant, T1 is the cycle of sampling pulse; The unit is opened in sampling, is used for when sampling pulse is high level, opens sampling switch; Integral unit is extracted in sampling, is used for extracting sampled data from continuous signal, and the sampled data time of carrying out is the signal averaging of τ.

Further, foregoing circuit also can have following characteristics, receiving terminal base band demodulating circuit also comprises A/D converting unit, digital filtering unit, amplifying unit, demodulating unit, is used for the signal level that sampled data is carried out after the signal averaging is carried out A/D conversion, digital filtering, amplification, demodulation.

Further, foregoing circuit also can have following characteristics, and described band stop filter adopts the LC form, comprises respectively at I ⁺, I ^-Between the holding wire, Q ⁺, Q ^-The inductance and the electric capacity of serial or parallel connection are set between the holding wire.

Prior art increases between the antenna merely isolates, and can not eliminate the performance difference of interchannel well, and compared with prior art, the inventive method can suppress to drop into the spectral aliasing component in the base band effectively.Thereby solved in the existing dual-mode handset double modely when communicating by letter simultaneously, side's transmitting power is to the problem that influences apart from the opposing party's of its fs receive channel sensitivity.

Description of drawings

Fig. 1 is prior art dual-mode handset spectrogram on the receiver side IQ line when working simultaneously.

Fig. 2 is a prior art spectral aliasing schematic diagram.

Fig. 3 disturbs inhibition/filter circuit among the embodiment.

Fig. 4 is periodicity rectangularly-sampled pulse time domain waveform figure among the embodiment.

Fig. 5 is the frequency characteristic/inhibition effect schematic diagram of filter circuit among the embodiment.

Fig. 6 is the spectrogram that obtains among the embodiment.

Fig. 7 is a method flow diagram among the embodiment.

Fig. 8 is the periodically spectral characteristic figure of rectangularly-sampled pulse of prior art.

Fig. 9 is a periodicity rectangularly-sampled pulse frequency spectrum performance plot among the embodiment.

Embodiment

Figure 3 shows that the channel selectivity that the CDMA side is provided with in the dual-mode handset disturbs inhibition/filter circuit, comprise CDMA base band demodulating circuit and band stop filter, wherein,

Described band stop filter is used to suppress to sneak into the interference components of receiving terminal CDMA baseband frequency spectrum, and its blanketing frequency is the center with fs, is input as baseband I/Q signal that the mixing of cdma receiver front end produces, I ⁺, I ^-Be a differential pair, Q ⁺, Q ^-Be a differential pair, signal is to CDMA base band demodulating circuit after the output filtering;

Using Shi Lizhong, can on differential lines, adopt the band stop filter of LC form, the value of LC resonance frequency fs require be, at the fs Frequency point the sunken characteristic of band preferably can be arranged, less Insertion Loss is arranged near zero-frequency.Described band stop filter can be a low pass filter also, but is difficult to accomplish the outer suppression characteristic of more precipitous band.As shown in Figure 3, adopt the band stop filter of LC series connection form to be attempted by on the i/q signal line, and it is less at the fs place to connect impedance, plays near the effect of disturbing the blanketing frequency fs; Perhaps, adopt the filter of LC parallel-connection structure to be inserted on the holding wire, promptly at I ⁺, I ^-Between, Q ⁺, Q ^-Between in parallel inductance and electric capacity are set, very high in the impedance at resonance frequency fs place, equally also can near the interference of blanketing frequency fs.The circuit that adopts can effectively suppress near sample frequency fs interference components, that may sneak into the CDMA baseband frequency spectrum, suppresses effect as shown in Figure 5.

Described CDMA base band demodulating circuit, be used to be provided with the sample frequency and the sampling pulse width of sampling pulse, the signal of described band stop filter output is sampled, and it is average that this sampled data is carried out continuous signal, comprising that sampling is provided with the unit, and the unit is opened in sampling, integral unit, A/D converting unit, digital filtering unit, amplifying unit, demodulating unit, wherein

Sampling is provided with the unit, is used to be provided with the sample frequency fs and the sampling pulse width τ of sampling pulse; Described sample frequency fs satisfies the Nyquist sampling theorem, and more than or equal to the twice that is sampled signal bandwidth, described sampling pulse width τ=k*T ₁, wherein, T1 is the cycle of sampling pulse, T1=1/fs; K is a constant;

The unit is opened in sampling, is used for when sampling pulse is high level, opens sampling switch;

If the sampling pulse level is a low level, then wait until to become till the high level always.

Integral unit is extracted in sampling, be used for extracting sampled data from continuous signal, and to the sampled data time of carrying out be the signal averaging of τ, promptly carrying out with 0 to sampled data is the next time, time τ is the integral operation in the upper bound, and described sampled data is the function of time τ;

From the realization of engineering, during the periodic sampling pulse high level, be exactly to being sampled the integration of signal to the average reality that is sampled signal.

A/D converting unit, digital filtering unit, amplifying unit, demodulating unit are used for the signal level of integral unit output is carried out A/D conversion, digital filtering, amplification, demodulation.

Method flow diagram among the embodiment may further comprise the steps as shown in Figure 7:

Step 100 is provided with the sample frequency fs of sampling pulse, and this sample frequency satisfies Nyquist (Nyquist) sampling theorem, and more than or equal to the twice that is sampled signal bandwidth;

The general value of sample frequency was between 4～16 or higher during engineering was used.Comprise the fs spectrum component in the signal if be sampled, will inevitably fall into baseband signal by spectral aliasing and form interference, the spectral aliasing situation shown in the accompanying drawing 2 may occur.Therefore, be band-limited signal if be sampled signal, sample frequency fs should be set at more than or equal to the twice that is sampled signal bandwidth, to guarantee undistorted sampling.

Should sample frequency fs=19.6608MHz be set with in the example; For bandwidth BW is the CDMA baseband signal of 1.2288MHz, and sample frequency fs 〉=2*BW just can accomplish complete undistorted sampling.

Step 110, it is the band stop filter at center with fs that blanketing frequency is set;

Described band stop filter can suppress to sneak into the interference components of receiving terminal CDMA baseband frequency spectrum.

Step 120 is provided with sampling pulse width τ=k*T ₁, k is a constant;

T1 is the cycle of sampling pulse, T1=1/fs; τ and T ₁Proportionality coefficient value principle be in order to suppress the gross power that low-order harmonic falls within the CDMA baseband signal to greatest extent.

Reduce or eliminate the interference of spectral aliasing the CDMA baseband signal, will suppress mixer output GSM 900MHz band transmit frequency spectrum and CDMA local oscillator mixed product ω s, 2 ω s, 3 ω s, n ω s enters the amplitude before the A/D sampling, perhaps suppresses in sampling.

Frequency-domain expression by the pulse of periodicity rectangularly-sampled can calculate, the F shown in Fig. 8 ₀, F _nCan express by following formula:

${\mathrm{<figure-callout\; id="0"\; label="F"\; filenames="S07100312220070116E000022.png,S07100312220070116E000032.png"\; state="\{\{state\}\}">F</figure-callout>}}_0=\frac{\mathrm{E\&tau;}}{T_1};$

$F_n=\frac{\mathrm{E\&tau;}}{T_1}\mathrm{Sa}\left(\frac{\mathrm{n\&pi;\&tau;}}{T_1}\right);$

Above-mentioned two expression formulas are the general formula of periodicity rectangularly-sampled pulse train.τ and T in the formula ₁Can be arbitrary value, n be a constant.

Should use in the example k=0.5, i.e. τ=0.5*T ₁The time, at this moment, F ₂=0, can eliminate sampling rate 2 frequency multiplication spectrum energy aliasings fully and enter the CDMA base band, the frequency spectrum of sampling pulse is seen Fig. 9.

Simultaneously, ${\mathrm{<figure-callout\; id="0"\; label="F"\; filenames="S07100312220070116E000022.png,S07100312220070116E000032.png"\; state="\{\{state\}\}">F</figure-callout>}}_0=\frac{\mathrm{E\&tau;}}{T_1}=\frac{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="S07100312220070116E000011.png,S07100312220070116E000012.png"\; state="\{\{state\}\}">E</figure-callout>}}{2},$ $F_1=\frac{\mathrm{E\&tau;}}{T_1}\mathrm{Sa}\left(\frac{\mathrm{\&pi;\&tau;}}{T_1}\right)=\frac{E}{\mathrm{\&pi;}},$ ${\mathrm{<figure-callout\; id="3"\; label="F"\; filenames="S07100312220070116E000022.png"\; state="\{\{state\}\}">F</figure-callout>}}_3=\frac{\mathrm{E\&tau;}}{T_1}\mathrm{Sa}\left(\frac{3\mathrm{\&pi;\&tau;}}{T_1}\right)=-\frac{\mathrm{<figure-callout\; id="3"\; label="E"\; filenames="S07100312220070116E000022.png"\; state="\{\{state\}\}">E</figure-callout>}}{3\mathrm{\&pi;}},$

$10\lg \left|\frac{F_0}{F_1}\right|=10\lg (\mathrm{\&pi;}/2)=1.96\mathrm{dB},$ $10\lg \left|\frac{F_0}{{\mathrm{<figure-callout\; id="3"\; label="F"\; filenames="S07100312220070116E000022.png"\; state="\{\{state\}\}">F</figure-callout>}}_3}\right|=10\lg (3\mathrm{\&pi;}/2)=6.7\mathrm{dB}$

Because during by low pass filter, the power of 3 ω s than ω s have more inhibition (actual measurement＞10dB), add and adopt this A/D method of sampling that 3 ω s place energy are decayed, make that the aliasing spectrum energy that falls in the CDMA 1.2288MHz bandwidth is little a lot.With τ=0.5*T ₁The frequency spectrum that obtains behind the periodic samples pulse sampling of parameter can suppress 6.7dB to 3 sampling spectrum energies as shown in Figure 6.

Step 130 when the sampling pulse level is high level, is opened sampling switch;

If the sampling pulse level is a low level, then wait until to become till the high level always.

Step 140 is sampled according to set sample frequency fs, extracts sampled data from continuous signal, and to the signal averaging that is τ of this data time of carrying out, and obtains a level value, the unit volt after average;

The time of carrying out is that the signal averaging of τ is the important step that suppresses spectral aliasing, and its effect can embody by the expression formula and the accompanying drawing of step 120, the way of realization of its expression formula that also to be the periodic sampling pulse sample to the continuous signal of limited bandwidth.Traditional impulse sampling is to use periodicity rectangle burst pulse to replace ideal period impulse sequence that continuous signal is sampled, because the sampling time is extremely short, therefore can reach the effect similar with desirable sample sequence.And sample mean is extended to time τ, but obtaining step 120 described effects.

Keeping CDMA baseband sampling speed constant, make sampling pulse high level lasting time τ=0.5*T with in the example ₁When carrying out the A/D sampling, be between high period at the sampling rectangular pulse, sampled data is got the average of this time period continuous signal, average length of time is the τ (see figure 4).

Step 150 is carried out the A/D conversion to the signal level of obtaining; And the signal that sampling is obtained carried out digital filtering, amplification, demodulation, the same prior art of this step is so repeat no more.

Claims (7)

1. the inhibition method disturbed of a double-module mobile phone channel selective may further comprise the steps:

(1) the sample frequency fs of sampling pulse is set, according to this fs sampling pulse width τ is set, and blanketing frequency is set is the band stop filter at center with this fs, and described sample frequency satisfies the Nyquist sampling theorem, and more than or equal to the twice that is sampled signal bandwidth; Described sampling pulse width τ=k*T ₁, k is a constant, and T1 is the cycle of sampling pulse, and described band stop filter is used to suppress to sneak into the interference components of receiving terminal baseband frequency spectrum, and its blanketing frequency is the center with fs, is input as baseband I/Q signal that the receiver front end mixing produces, I ⁺, I ^-Be a differential pair, Q ⁺, Q ^-Be a differential pair, signal is to receiving terminal base band demodulating circuit after the output filtering;

(2) when the sampling pulse level is high level, open sampling switch, sample according to set sample frequency fs, from the signal of the output of band stop filter, extract sampled data, and to the signal averaging that is τ of this data time of carrying out.

2. method according to claim 1 is characterized in that step (2) also comprises afterwards:

(3) signal level that sampled data is carried out after the signal averaging is carried out A/D conversion, digital filtering, amplification, demodulation.

3. method according to claim 1 is characterized in that:

Described band stop filter adopts the LC form, comprises respectively at I ⁺, I ^-Between the holding wire, Q ⁺, Q ^-The inductance and the electric capacity of serial or parallel connection are set between the holding wire.

4. a double-module mobile phone channel selective codan comprises receiving terminal base band demodulating circuit, it is characterized in that, also comprises band stop filter, wherein,

Described band stop filter is used to suppress to sneak into the interference components of receiving terminal baseband frequency spectrum, and its blanketing frequency is the center with fs, is input as baseband I/Q signal that the receiver front end mixing produces, I ⁺, I ^-Be a differential pair, Q ⁺, Q ^-Be a differential pair, signal is to receiving terminal base band demodulating circuit after the output filtering;

Receiving terminal base band demodulating circuit is used to be provided with sample frequency fs and sampling pulse width τ, the signal of described band stop filter output is sampled, and being τ to this sampled data time of carrying out, continuous signal is average; Described sample frequency satisfies the Nyquist sampling theorem, and more than or equal to the twice that is sampled signal bandwidth, described sampling pulse width τ=k*T ₁, k is a constant, T1 is the cycle of sampling pulse.

5. as circuit as described in the claim 4, it is characterized in that,

Receiving terminal base band demodulating circuit comprises that sampling is provided with the unit, and the unit is opened in sampling, and integral unit is extracted in sampling,

Sampling is provided with the unit, is used to be provided with the sample frequency fs and the sampling pulse width τ of sampling pulse; Described sample frequency satisfies the Nyquist sampling theorem, and more than or equal to the twice that is sampled signal bandwidth, described sampling pulse width τ=k*T ₁, k is a constant, T1 is the cycle of sampling pulse;

The unit is opened in sampling, is used for when sampling pulse is high level, opens sampling switch;

Integral unit is extracted in sampling, is used for extracting sampled data from continuous signal, and the sampled data time of carrying out is the signal averaging of τ.

6. as circuit as described in the claim 5, it is characterized in that described receiving terminal base band demodulating circuit also comprises:

A/D converting unit, digital filtering unit, amplifying unit, demodulating unit are used for the signal level that sampled data is carried out after the signal averaging is carried out A/D conversion, digital filtering, amplification, demodulation.

7. as circuit as described in the claim 4, it is characterized in that,

Described band stop filter adopts the LC form, comprises respectively at I ⁺, I ^-Between the holding wire, Q ⁺, Q ^-The inductance and the electric capacity of series connection/parallel connection are set between the holding wire.

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