CN101094473A - GSM / CDMA dual modes terminal for improving receiving sensitivity of CDMA, and method - Google Patents

Abstract

The dual mode terminal comprises: a frontend RF switch; a GSM main control chip; a filer connected to the frontend switch and used for receiving the signals outputted from the D/A converter and making low pass filter; a D/S converter having an input end connected to the GSM main control chip and an output end connected to the filter unit, which is used for receiving the level data outputted from GSM main control chip, and making D/A conversion, and outputting the converted data to the filer. Said level data satisfies the following requirement: in (tau-tau1)/2 time length, raising in linear up to switch control voltage from 0; keeping the burst duration time tau1; in (tau-tau1)/2 time length, dropping in linear from the switch control voltage to 0; tau >tau 1.

Description

A kind of GSM/CDMA dual-mode terminal and method of improving the CDMA receiving sensitivity

Technical field

The present invention relates to wireless communication field, relate in particular to inhibition method and a kind of GSM/CDMA dual-mode terminal of GSM/CDMA dual-mode handset radio frequency interference.

Background technology

GSM (global system for mobile communications)/CDMA (code division multiple access) 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 situation of various mutual interference mutually can appear in the GSM900/1800MHz frequency range when working together with the CDMA800/1900MHz frequency range.

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.

We also find under study for action simultaneously, sensitivity has the influence of burst to CDMA in its front radio-frequency switch switching meeting in GSM standby or the conversation, as long as CDMA is in high-power emission state, even if GSM does not launch at this moment or transmitting power is very little, this burst effect does not significantly decrease.

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 because the restriction of handset size and Antenna Design technical merit, be difficult to rise to perfect condition at the isolation between antennas of some frequency range dual-mode handset.

Summary of the invention

The technical problem to be solved in the present invention is, a kind of inhibition method of dual-mode handset GSM switch modulation influence is provided, when solving in the existing dual-mode handset CDMA high-power emission GSM standby or communication, the CDMA transmitting power is subjected to the GSM switch modulation, influences the problem of CDMA receiving sensitivity.

For solving the problems of the technologies described above, the present invention proposes a kind of GSM/CDMA dual-mode terminal of the CDMA of improvement receiving sensitivity, comprise the front radio-frequency switch, the gsm master chip also comprises,

Filter unit links to each other with the front radio-frequency switch, receives the output signal of D/A conversion unit, carries out low-pass filtering;

D/A conversion unit, its input is connected to the gsm master chip, its output is connected to filter unit, be used for before each front radio-frequency switch switches, receive the level data of gsm master chip output, carry out outputing signal to filter unit after the digital-to-analogue conversion, wherein, described level data satisfies following requirement, at (τ-τ ₁Rise to switch control voltage from 0 linearity in the time of)/2, keep the duration τ of a burst Burst ₁, then at (τ-τ ₁Drop to 0 from the switch control voltage linearity in the time of)/2, wherein τ＞τ ₁

Further, above-mentioned dual-mode terminal also can have following characteristics, described filter unit is a RC filter circuit, comprise resistance and an electric capacity, described electric capacity one end is connected to the front radio-frequency switch, one end is connected to ground, and described resistance one end is connected to the front radio-frequency switch, and an end is connected to described D/A conversion unit.

Further, above-mentioned dual-mode terminal also can have following characteristics, and described D/A conversion unit uses pulse density modulator PDM to realize that the RC time constant of described RC filter circuit is 20～40 times of PDM pulse period.

Further, above-mentioned dual-mode terminal also can have following characteristics, and described gsm master chip is according to the timer of baseband processor, (τ-τ before its reception or transmission time slot ₁)/2 time starts described D/A conversion unit.

Further, above-mentioned dual-mode terminal also can have following characteristics, described τ＞τ ₁+ 10us.

A kind of method of improving GSM/CDMA dual-mode terminal CDMA receiving sensitivity, on the front radio-frequency switch, connect a switch controlling signal unit, before each front radio-frequency switch switches, a switch controlling signal is exported to the front radio-frequency switch in described switch controlling signal unit, described switch controlling signal satisfies following requirement, at (τ-τ ₁Rise to switch control voltage from 0 linearity in the time of)/2, keep the duration τ of a burst Burst ₁, then at (τ-τ ₁Drop to 0 from the switch control voltage linearity in the time of)/2, wherein τ＞τ ₁

Further, said method also can have following characteristics, described switch controlling signal unit connects D/A conversion unit realization by the gsm master chip of described GSM/CDMA dual-mode terminal, described gsm master chip is connected to the input of described D/A conversion unit, and the output of described D/A conversion unit is connected to described front radio-frequency switch.

Further, said method also can have following characteristics, and described switch controlling signal also will carry out filtering by a RC filter circuit, exports described front radio-frequency switch to.

Further, said method also can have following characteristics, and described D/A conversion unit uses PDM to realize that the RC time constant of described RC filter circuit is 20～40 times of described PDM pulse period.

Further, said method also can have following characteristics, and described gsm master chip is according to the timer of baseband processor, (τ-τ before its reception or transmission time slot ₁)/2 time starts described D/A conversion unit, exports described switch controlling signal.

Further, said method also can have following characteristics, described τ＞τ ₁+ 10us.

The inventive method can suppress side's sensitivity deterioration problem that dual-mode handset causes owing to isolation between antennas is on the low side effectively.

Description of drawings

Fig. 1 is that schematic diagram is switched in the GSM transmitting-receiving.

Fig. 2 is a switch mixing schematic diagram.

Fig. 3 is the improvement schematic diagram of the present invention to the prior art circuits part.

Fig. 4 is the improved switch controlling signal of the present invention.

Fig. 5 is that radio-frequency (RF) switch is improved behind the waveform inhibition design sketch to out of band spectrum.

Fig. 6 is the invention process flow chart.

Fig. 7 is the contrast schematic diagram of original switch control waveform and existing switch control waveform.

Embodiment

When CDMA high-power emission GSM standby or communication, the CDMA transmitting power is subjected to the GSM switch modulation, influences the CDMA receiving sensitivity conversely in the existing dual-mode handset.

For this bursty interference, by intensive experiment and analysis, we think that the working mechanism that the type is disturbed is: CDMA has certain power to be coupled to the GSM antenna by antenna during emission.And according to the GSM working mechanism, receiving and transmission time slot when replacing, the front radio-frequency switch can be done once to switch to the radio-frequency channel, with guarantee in correspondence reception, transmission time slot internal antenna respectively with reception, radiating circuit connection.Switch switch brought impedance saltus step as shown in Figure 1, the variation of impedance brings the variation of radio-frequency current, this variation just debugging on the frequency spectrum that its carrier wave-CDMA transmits.When the spectrum modulation of switch change was on CDMA transmits, the CDMA emission spectrum will be expanded, and increased from the noise spectrum power of the reception frequency of CDMA emission spectrum 45MHz, as shown in Figure 2.The noise power that produces at GSM radio-frequency (RF) switch place is come out by the GSM aerial radiation like this, is received by the CDMA antenna, and the receiving sensitivity under the CDMA weak signal will be influenced.

Waveform among Fig. 1 is a GSM front radio-frequency switch switching signal, and the CDMA that the meeting of switch switching fast is combined in this radio-frequency front-end with lotus root transmits and modulated by switching signal.Radio-frequency (RF) switch is equivalent to the effect of frequency mixer.

In order to address the above problem, the present invention proposes a kind of GSM/CDMA dual-mode terminal that can improve the CDMA receiving sensitivity, increases D/A (D/A) change-over circuit and RC filter circuit on the GSM radio-frequency (RF) switch switch-over control signal in the GSM/CDMA dual-mode terminal, as shown in Figure 3, wherein

The RC filter circuit comprises resistance and an electric capacity, and electric capacity one end is connected to the front radio-frequency switch, and an end is connected to ground, resistance one end is connected to the front radio-frequency switch, one end is connected to the output of D/A change-over circuit, and the RC circuit is typical low pass filter, plays filtering and level and smooth effect.

The D/A change-over circuit is by the gsm master chip controls, and the input of D/A change-over circuit is connected to the gsm master chip.Can adopt the implementation of pulse density modulator (PDM) as the D/A change-over circuit.

Storage one switch control curve in the gsm master chip, switch control curve data as shown in Figure 4.

$f=\left\{\begin{array}{cc}\frac{2E}{\mathrm{\τ}-{\mathrm{\τ}}_1}*t& [0,\frac{\mathrm{\τ}-{\mathrm{\τ}}_1}{2}]\\ E& [\frac{\mathrm{\τ}-{\mathrm{\τ}}_1}{2},\frac{\mathrm{\τ}+{\mathrm{\τ}}_1}{2}]\\ \frac{-2E}{\mathrm{\τ}-{\mathrm{\τ}}_1}*t+\frac{2\mathrm{E\τ}}{\mathrm{\τ}-{\mathrm{\τ}}_1}& [\frac{\mathrm{\τ}+{\mathrm{\τ}}_1}{2},\mathrm{\τ}]\end{array}\right.$

In the formula:

E is a switch control voltage, about general 2.3～2.8V,

τ ₁＝B*48/13us，

τ ₁Be the GSM transmitting-receiving time that burst continued, along with burst type difference, length is different.B is the bit number of this burst (burst), and Burst has: conventional Burst, insert Burst etc., and dissimilar burst comprises different bit numbers.

Be the switch control impuls rise time, the rise time is by τ ₁Determine jointly with τ.

The τ value can suppress effect adjustment according to reality, and the switching signal rise time is 1us when supposing not adopt this programme, and this programme switch rise time (τ-τ can be set ₁)/2=10us, τ=τ ₁+ 20us.And GSM radio-frequency (RF) switch pin pipe increases to low-impedance switching time from high impedance, and the speed that switching signal is switched the high-frequency current switching that causes reduces.Concrete rise time (τ-τ ₁)/2 value can be more than 10us.

Switch control curve is the improvement to former GSM radio-frequency (RF) switch control waveform, is used for suppressing the high fdrequency component of former switch frequency spectrum.Certainly there is better curve also can play the effect that suppresses high frequency.

Before switching, the GSM switch starts the D/A conversion, by the output of above-mentioned switch control curve waveform with certain lead.This waveform suppresses high fdrequency component, and the speed of current-jump in the time of can reducing the switch switching is so even the switch frequency spectrum is modulated on the CDMA emission spectrum, it has obtained bigger inhibition to influence that CDMA receives.

Determining of lead need be definite according to the timer in the GSM baseband processor.Just the GSM baseband processor can be determined to start the moment that receives, launches, and shifts to an earlier date on this basis

Get final product.

This switch control curve is not limited to by the gsm master chip by the output of D/A change-over circuit, but since in the radio communication to the requirement of signal Synchronization than higher, preferably handle by the gsm master chip.

Dotted portion is the spectrum distribution that (meets the GSM standard, do not do any improvement) in the prior art among Fig. 5, solid line (broken line) part expression be the spectrum distribution of the scheme that proposes of the present invention, from f1 frequency spectrum at a distance more inhibition is being arranged.

Prior art relies between the antenna merely isolates, and antenna isolation aspect design difficulty is bigger, has been difficult to break through.Compared with prior art, the inventive method can suppress side's sensitivity deterioration problem that dual-mode handset causes owing to isolation between antennas is on the low side effectively.

Below in conjunction with accompanying drawing and application example technical scheme of the present invention is described in detail.

In application example, RC filter circuit and D/A change-over circuit need be increased, as shown in Figure 3 on frequency range switch-over control signal line.The D/A change-over circuit can use the PDM pulse density modulator to realize.The value requirement of RC time constant T is 20～40 times PDM pulse period Δ T.

This programme is applicable to that control signal directly controls the scheme of pin pipe radio-frequency (RF) switch.

The method flow diagram of application example needs gsm module before each switching transceiver channel as shown in Figure 6, by the gsm master chip controls, implements following steps:

Step 100 is obtained GSM transmitting-receiving slot synchronization time reference point, calculates the time reference point of D/A conversion with this.

Described datum mark is meant that GSM receives, the accurate starting point of emission timeslot (time slot), be to produce by the analytical calculation that GSM baseband signal processor in the mobile phone passes through to received signal, generally in software, obtain, but different GSM software and hardware scheme specific implementation details may have difference.

The starting point of D/A output shifts to an earlier date (τ-τ than GSM reception, transmission time slot ₁)/2.The switch control waveform of its output and the contrast of existing switch control waveform are as shown in Figure 7.

Step 110, the initial point of setting dateout.

Array length is made as n, and starting point is 0;

Step 120 reads the level data of corresponding sequential successively.

Step 130 is carried out D/A output according to default level data.

Step 140 judges whether that all level data outputs finish, if output does not finish, then forwards the output that step 120 is carried out next level to, and having exported finishes then enters step 150.

Step 150 finishes this output.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (11)

1, a kind of GSM/CDMA dual-mode terminal that improves the CDMA receiving sensitivity comprises the front radio-frequency switch, and the gsm master chip is characterized in that, also comprise,

Filter unit links to each other with the front radio-frequency switch, receives the output signal of D/A conversion unit, carries out low-pass filtering;

D/A conversion unit, its input is connected to the gsm master chip, its output is connected to filter unit, be used for before each front radio-frequency switch switches, receive the level data of gsm master chip output, carry out outputing signal to filter unit after the digital-to-analogue conversion, wherein, described level data satisfies following requirement, at (τ-τ ₁Rise to switch control voltage from 0 linearity in the time of)/2, keep the duration τ of a burst Burst ₁, then at (τ-τ ₁Drop to 0 from the switch control voltage linearity in the time of)/2, wherein τ＞τ ₁

2, dual-mode terminal as claimed in claim 1, it is characterized in that, described filter unit is a RC filter circuit, comprise resistance and an electric capacity, described electric capacity one end is connected to the front radio-frequency switch, one end is connected to ground, and described resistance one end is connected to the front radio-frequency switch, and an end is connected to described D/A conversion unit.

3, dual-mode terminal as claimed in claim 2 is characterized in that, described D/A conversion unit uses pulse density modulator PDM to realize that the RC time constant of described RC filter circuit is 20～40 times of PDM pulse period.

4, dual-mode terminal as claimed in claim 1 is characterized in that, described gsm master chip is according to the timer of baseband processor, (τ-τ before its reception or transmission time slot ₁)/2 time starts described D/A conversion unit.

5, dual-mode terminal as claimed in claim 1 is characterized in that, described τ＞τ ₁+ 10us.

6, a kind of method of improving GSM/CDMA dual-mode terminal CDMA receiving sensitivity, on the front radio-frequency switch, connect a switch controlling signal unit, before each front radio-frequency switch switches, a switch controlling signal is exported to the front radio-frequency switch in described switch controlling signal unit, described switch controlling signal satisfies following requirement, at (τ-τ ₁Rise to switch control voltage from 0 linearity in the time of)/2, keep the duration τ of a burst Burst ₁, then at (τ-τ ₁Drop to 0 from the switch control voltage linearity in the time of)/2, wherein τ＞τ ₁

7, method as claimed in claim 6, it is characterized in that, described switch controlling signal unit connects D/A conversion unit realization by the gsm master chip of described GSM/CDMA dual-mode terminal, described gsm master chip is connected to the input of described D/A conversion unit, and the output of described D/A conversion unit is connected to described front radio-frequency switch.

As claim 6 or 7 described methods, it is characterized in that 8, described switch controlling signal also will carry out filtering by a RC filter circuit, exports described front radio-frequency switch to.

9, method as claimed in claim 8 is characterized in that, described D/A conversion unit uses PDM to realize that the RC time constant of described RC filter circuit is 20～40 times of described PDM pulse period.

10, method as claimed in claim 7 is characterized in that, described gsm master chip is according to the timer of baseband processor, (τ-τ before its reception or transmission time slot ₁)/2 time starts described D/A conversion unit, exports described switch controlling signal.

11, method as claimed in claim 6 is characterized in that, described τ＞τ ₁+ 10us.

Images