CN101299616A - Radio frequency receiver as well as electronic apparatus containing the same - Google Patents
Radio frequency receiver as well as electronic apparatus containing the same Download PDFInfo
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- CN101299616A CN101299616A CNA2008101378394A CN200810137839A CN101299616A CN 101299616 A CN101299616 A CN 101299616A CN A2008101378394 A CNA2008101378394 A CN A2008101378394A CN 200810137839 A CN200810137839 A CN 200810137839A CN 101299616 A CN101299616 A CN 101299616A
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Abstract
A radio frequency receiver includes a radio frequency front end lower frequency conversion unit and a direct current drift cancellation unit, wherein, the radio frequency front end lower frequency conversion unit is used to receive the radiofrequency signals of operation mode, and calibrating signals of calibration mode, and to lower-convert the radiofrequency signals and calibrating signals into baseband signals to output; the direct current drift cancellation unit receives the baseband signals after the lower frequency conversion of the calibrating signals, passing through the FFT arithmetic, generates and stores direct current calibration tables corresponding to different receiver gains, in the calibration mode; and the direct current drift cancellation unit executes direct current drift cancellation to the radiofrequency signals by looking for the stored direct current calibration tables, in the work mode. The inventive radio frequency receiver and electronic appliance with the same can be applied to various wireless receiver application occasions, and can effectively eliminate the affect of the direct current excursion produced by the radio frequency receiver to the demodulation performance of the radio frequency receiver.
Description
Technical field
The present invention relates to a kind of communication equipment, especially with a kind of radio-frequency transmitter and to have an electronic equipment of this radio-frequency transmitter relevant.
Background technology
Along with the develop rapidly of wireless communication technology, the wireless communication system product is more and more universal in recent years, becomes the important component part of mankind nowadays development of information.Radio-frequency transmitter is positioned at wireless communication system foremost, and its structure and performance directly affect whole communication system.Optimal design structure and the suitable manufacturing process of selection to improve the ratio of performance to price of system, are the pursuit directions of radio frequency design.
The most attractive part of zero intermediate frequency reciver is need not pass through intermediate frequency in the downconversion process, and image frequency promptly is radiofrequency signal itself, does not exist image frequency to disturb, and image-reject filter in the former super-heterodyne architecture and intermediate-frequency filter all can omit.Cancelled outer member so on the one hand, the monolithic that helps system is integrated, reduces cost.Required circuit module of system and the outside segments minimizing of counting has on the other hand reduced the required power consumption of receiver and has reduced the chance that radiofrequency signal is subjected to external disturbance.
Super-heterodyne architecture is considered to the most reliable receiver topological structure, because by suitably selecting intermediate frequency and filter can obtain splendid selectivity and sensitivity.Because a plurality of converter stages are arranged, DC deviation and local-oscillator leakage problem can not influence the performance of receiver.But mirror image interference suppression filter and channel selection filter are high Q value band pass filter, and they can only realize outside sheet, thereby have increased the cost and the size of receiver.At present, utilize integrated circuit fabrication process that these two filters are integrated in the very big difficulty of existence on the chip piece with other radio circuit.Therefore, the monolithic of superheterodyne receiver is integrated is difficult to realize because of the restriction that is subjected to the technology aspect.
Volume is little, cost is low and be easy to single chip integrated characteristics because zero intermediate frequency reciver has, and has become a kind of structure that has competitiveness in the radio-frequency transmitter, is subjected to paying close attention to widely in wireless communication field.But zero-if architecture exists problems such as DC deviation, local-oscillator leakage and flicker noise, wherein, dc shift disturbs the problem of the main solution that becomes zero intermediate frequency reciver, these direct current signals will be superimposed upon on the baseband signal, and, be called as DC deviation or dc shift to the interference of baseband signal formation.The DC deviation often noise than radio-frequency front-end is also big, makes the signal to noise ratio variation, and big DC deviation of while may make the amplifiers at different levels behind the frequency mixer saturated, can't amplify useful signal.Have a strong impact on the demodulation performance of receiver.
Summary of the invention
At problems of the prior art, the object of the present invention is to provide a kind of radio-frequency transmitter, can the dc shift signal that produce in the radio-frequency transmitter be calculated accurately and estimate, reduce or eliminate the influence that the dc shift signal causes to received signal, improve the performance of radio-frequency transmitter.
Another object of the present invention is to provide a kind of electronic equipment with radio-frequency transmitter of the present invention.
For achieving the above object, technical scheme of the present invention is as follows:
A kind of radio-frequency transmitter comprises radio-frequency front-end down-converter unit and dc shift elimination unit;
Described radio-frequency front-end down-converter unit is used to receive the radiofrequency signal of mode of operation and the calibrating signal of calibration mode, and described radiofrequency signal and calibrating signal are down-converted to baseband signal output;
Described dc shift is eliminated the unit, at calibration mode, receives the baseband signal after the described calibrating signal down-conversion, through the FFT computing, generates and stores the corresponding down direct current calibration chart of different receivers gain; In mode of operation, the direct current calibration chart of storing by searching carries out dc shift to radiofrequency signal and eliminates.
Electronic equipment of the present invention has radio-frequency transmitter of the present invention.
As shown from the above technical solution, the present invention has following beneficial effect: the present invention eliminates the unit by increasing dc shift at radio-frequency front-end variable gain amplifier output, dc shift and the existing method in the radio-frequency transmitter of having eliminated relatively has following advantage:
1, dc shift elimination circuit can directly be integrated in the radio-frequency transmitter chip;
2, reduced the complexity that baseband digital signal is handled;
3, suppressed the dc shift in the receiver effectively;
Below by drawings and Examples, technical scheme of the present invention is described in further detail.
Description of drawings
The modular structure figure of the radio-frequency transmitter of Fig. 1 embodiment of the invention;
The circuit diagram of the radio-frequency transmitter of Fig. 2 embodiment of the invention.
Embodiment
The invention will be further described below in conjunction with the accompanying drawings and the specific embodiments.
The radio-frequency transmitter of the embodiment of the invention comprises radio-frequency front-end down-converter unit and dc shift elimination unit;
Described radio-frequency front-end down-converter unit is used to receive the radiofrequency signal of mode of operation and the calibrating signal of calibration mode, and described radiofrequency signal and calibrating signal are down-converted to baseband signal output;
Described dc shift is eliminated the unit, at calibration mode, receive the baseband signal after the described calibrating signal down-conversion, through the FFT computing, generate and store the corresponding down direct current calibration chart of different receivers gain, described direct current calibration chart is made of the list cell of the corresponding different gains value of some; In mode of operation, the direct current calibration chart of storing by searching carries out dc shift to radiofrequency signal and eliminates.
As depicted in figs. 1 and 2, the radio-frequency transmitter of the embodiment of the invention, described radio-frequency front-end down-converter unit comprises LNA circuit, phase-locked loop, frequency mixer/quadrature demodulator, low pass filter, variable gain amplifier, AD converter; Described AD converter is converted to digital baseband signal with described baseband signal, and described dc shift is eliminated the output that the unit is connected in described AD converter.AD converter changes the analog baseband signal of variable gain amplifier output into dc shift elimination unit that digital baseband signal exports the Digital Signal Processing part to.The structure of AD converter can be traditional AD converter structure, also can be the AD converter of ∑-Δ (Sigma-Delta) structure.
As depicted in figs. 1 and 2, the radio-frequency transmitter of the embodiment of the invention, described dc shift is eliminated FFT (N-point FFT) computing module that the unit comprises that a N order, is used to store the memory of direct current calibration chart and uses the dc shift calibration chart to eliminate the cancellation module of dc shift, described FFT module at calibration mode by calculating at frequency domain under the different receivers gain that dc shift is big or small and generating described direct current calibration chart.The FFT computing module that N is ordered, its realization can be selected according to the precision compromise of complexity of hardware and computing.Memory is FLASH preferably.
The radio-frequency front-end down-converter unit, it is used to receive common radiofrequency signal in mode of operation; At calibration mode, this signal receiving unit reception and carrier wave have the single-tone calibrating signal of certain frequency deviation, the power invariability of this tone signal; And the radiofrequency signal (comprising calibrating signal) that receives down-converted to baseband signal.
The FFT computing module, this module is carried out the FFT conversion to the digital baseband of the calibration tone signal of reception, calculates calibration tone signal corresponding A D full scale scale numerical value, generates the direct current calibration chart, is stored in FLASH or other memory.
Cancellation module in the mode of operation of radio-frequency transmitter, utilizes the direct current calibration chart of storing in the memory, by the mode of tabling look-up, and cancellation receiver dc shift signal.
Wherein, the FFT computing module carries out the FFT conversion to the digital baseband signal of the radio-frequency front-end down-converter unit output of radio-frequency transmitter, calculate the different receivers gain down, the difference power of dc shift signal and calibration tone signal, because useful calibrating signal power and AD full scale has known corresponding relation, just can extrapolate the corresponding relation of dc shift signal amplitude and AD full scale signal magnitude by above-mentioned difference power, draw the corresponding down I/Q two-way dc shift signal magnitude of different receivers gain, generate the direct current calibration chart, be stored in dc shift and eliminate in the memory of unit.
Wherein, dc shift is eliminated the unit when the receiver operate as normal, and the direct current calibration chart that utilizes the FFT computing module to extrapolate is at the receiver gain (AGC) of correspondence, by the mode of closed-loop process, in digital baseband signal, eliminate the dc shift that radio-frequency transmitter produces.
Brief description is the workflow of video receiver under calibration mode of the embodiment of the invention once, at first, at the radio-frequency transmitter calibration mode, generates and preserve the calibration chart of dc shift signal, as shown in Figure 1, may further comprise the steps:
At first, set the receiving gain sequence of radio-frequency transmitter.The radio-frequency transmitter of the embodiment of the invention, when calibrating, need be according to actual conditions, with the span segmentation of the receiving gain of radio-frequency transmitter, obtain a receiving gain sequence of radio-frequency transmitter, AGC (i) (i=1,2 ... N), in initial condition, get i=1.The segmentation method of the receiving gain of radio-frequency transmitter of the present invention, the selection of need between the projection accuracy of alignment time and dc shift, compromising.If segmentation is careful more, the projection accuracy that then obtains is just high more, has also extended simultaneously and has calibrated and search the time complexity of calibration chart.In practice, can determine the segmentation of receiving gain according to the receiving gain variation of radio-frequency transmitter and the incidence relation between the dc shift variation tendency.
Then, radio-frequency transmitter receives the radiofrequency signal that is used to calibrate, and it is down-converted to baseband signal.This radiofrequency signal power invariability, preferably one and carrier frequency have the tone signal (i.e. sine wave) of certain frequency deviation, why will certain frequency deviation be arranged with carrier signal, be for can the easier amplitude of calculating the dc shift signal more accurately in the treatment step from now on.This tone signal both can be launched by outside source, also can be launched by the built-in transmitter module of radio-frequency transmitter self, and be received by the signal receiving module of radio-frequency transmitter self.
As shown in Figure 2, the radiofrequency signal that radio-frequency transmitter receives (comprising tone signal) is after band pass filter (BPF) and low noise amplifier (LNA) amplification, with two-way local oscillation signal (LO) mixing of quadrature each other, produce homophase and quadrature two-way baseband signal respectively.Because the local oscillation signal frequency is identical with radio frequency signal frequency, so direct generation baseband signal after the mixing, and channel selection and gain are adjusted at and carry out on the base band, are finished by low pass filter on the chip (LPF) and variable gain amplifier (AGC).After above-mentioned adjustment was finished, input digital to analog converter (ADC) carried out analog-to-digital conversion and samples.
Carry out the FFT computing and generate calibration chart.FFT (Fast Fourier Transform, fast fourier transform) module, its effect are that the data of will sample transform from the time domain to frequency domain.Counting of AD sampling, i.e. the N value of the N FFT computing of ordering can be chosen according to actual needs, as gets N=256,512,1024 etc.
Baseband signal obtains the digital sampling point of its correspondence through AD sampling, and sampling point directly exports in the FFT module in the baseband processor.Can learn that from the characteristics of FFT conversion it is f that the energy of baseband signal mainly concentrates on frequency shift (FS)
CaliThe place, the concentration of energy of dc shift signal is at the zero-frequency place.After baseband signal is mapped to frequency domain, then under a certain receiver gain, can obtain the signal power of shifted signal (calibration tone signal) and the power of direct current signal (shifted signal).
In this step, digital baseband signal after the calibration tone signal process AD conversion is carried out the FFT conversion, calculate calibrating signal power and in the difference of the direct current signal power of zero-frequency, according to the known corresponding relation of calibration tone signal amplitude and AD full scale scale, extrapolate the AD full scale scale numerical value of dc shift signal correspondence.It can be refined as following steps:
At first, get the power of calibrating signal and the difference of dc shift signal power.After baseband signal is mapped to frequency domain, then in a certain receiver gain AGC (i), i=1,2,3 ... under the N, can obtain shifted signal y
BbSignal power P
Bb(i) (unit: dBm) and the power P of direct current signal
Dc(i) (unit: dBm), the size of its power and the gain A GC of receiver (i), i=1,2,3 ... N is one to one.After the FFT conversion, get the power of calibrating signal and the difference DELTA P (i) of dc shift signal power.
By the calculating of previous step, obtain the corresponding relation of calibrating signal power and AD full scale scale again.Obtain the power P of single-tone calibrating signal
BbWith a corresponding relation of the full scale scale of receiver AD, this corresponding relation can obtain accurately by manual or automatic mode.In concrete receiver was realized, this corresponding relation was to determine with known.
Above-mentioned corresponding relation is arranged, can push away obtaining the numerical value of direct current signal with respect to AD full scale scale.In order to obtain the amplitude of direct current signal, according to two corresponding relations that first two steps obtain, can obtain under different receiver gain AGC (i), direct current signal is with respect to the numerical value of AD full scale scale, and is as shown in table 1:
In table 1, α
iDBFS and β
iDBFS is respectively the amplitude size of I road and Q road direct current signal corresponding A D full scale scale.In above-mentioned step,, all can generate a list cell of described direct current calibration chart with respect to each receiving gain value of determining; For obtaining whole direct current calibration chart, need carry out a circulation.In initial condition, in the receiving gain sequence, get its first value, i.e. AGC (1), behind the list cell that obtains corresponding to AGC (1), whether the value of promptly judging i+1 in this way, then illustrates each list cell of direct current calibration chart all generate greater than N, can withdraw from circulation.If the value of i+1 is not more than N, then make i=i+1, AGC=AGC (i+1) returns then, proceeds circulation, obtains the list cell of next receiving gain value correspondence.Up to all list cells that obtain the direct current calibration chart.Obtain to generate dc shift signal calibration table behind all list cells and with its storage, its form is as shown in table 1.
Table 1
After calibration mode generated the direct current calibration chart, radio-frequency transmitter just can carry out the dc shift signal in mode of operation to be eliminated, and the direct current signal full scale scale numerical value that the FFT computing is extrapolated before this step utilization is eliminated direct current signal in digital baseband signal.
As shown in Figure 2, the radio-frequency transmitter of the embodiment of the invention, described dc shift signal removal process utilizes the dc shift signal calibration table that reckoning draws in the FFT computing module, adopts the mode of closed-loop process, eliminates dc shift in digital baseband signal.At first according to the receiving gain value of the radio-frequency transmitter of determining, search dc shift signal calibration table, the size of current according to the calibration chart indication generates a calibration current, input summer offsets with dc shift signal in the baseband signal of another input of adder input.
The radio-frequency transmitter of the embodiment of the invention has overcome the defective that existing receiver can not accurately be eliminated the dc shift signal that radio-frequency transmitter produces, and has improved the performance of receiver.
The electronic equipment of the embodiment of the invention, the radio-frequency transmitter with embodiment of the invention.Electronic equipment of the present invention can be mobile phone, Digital Television etc.The present invention can be applicable to the application scenario of various wireless receivers, comprises enhancement mode 3G (Third Generation) Moblie LTE TDD/FDD, digital television broadcasting DVB, WLAN (wireless local area network) WLAN.By using this radio-frequency transmitter, can eliminate the influence that dc shift signal that radio-frequency transmitter produces causes the receiver demodulation performance effectively.
Above-described only is preferable possible embodiments of the present invention; described embodiment is not in order to limit scope of patent protection of the present invention; therefore the equivalent structure done of every utilization specification of the present invention and accompanying drawing content changes, and in like manner all should be included in the protection model of the present invention.
Claims (10)
1. a radio-frequency transmitter comprises radio-frequency front-end down-converter unit and dc shift elimination unit;
Described radio-frequency front-end down-converter unit is used to receive the radiofrequency signal of mode of operation and the calibrating signal of calibration mode, and described radiofrequency signal and calibrating signal are down-converted to baseband signal output;
Described dc shift is eliminated the unit, at calibration mode, receives the baseband signal after the described calibrating signal down-conversion, through the FFT computing, generates and stores the corresponding down direct current calibration chart of different receivers gain; In mode of operation, the direct current calibration chart of storing by searching carries out dc shift to radiofrequency signal and eliminates.
2. radio-frequency transmitter as claimed in claim 1, it is characterized in that, described radio-frequency front-end down-converter unit comprises the LNA circuit, phase-locked loop, frequency mixer/quadrature demodulator, low pass filter, variable gain amplifier, AD converter, described dc shift is eliminated the digital baseband signal output that the unit is connected in described AD converter.
3. radio-frequency transmitter as claimed in claim 1, it is characterized in that, described dc shift is eliminated FFT computing module that the unit comprises that a N order, is used to store the memory of direct current calibration chart and uses the dc shift calibration chart to eliminate the cancellation module of dc shift, described FFT module at calibration mode by calculating at frequency domain under the different receivers gain that dc shift is big or small and generating described direct current calibration chart.
4. radio-frequency transmitter as claimed in claim 3 is characterized in that, described calibrating signal is a tone signal, the frequency-offset carriers certain frequency of described tone signal.
5. radio-frequency transmitter as claimed in claim 4 is characterized in that, described dc shift is eliminated the unit, by closed-loop process, in digital baseband signal dc shift is eliminated.
6. radio-frequency transmitter as claimed in claim 2 is characterized in that, described memory is FLASH.
7. radio-frequency transmitter as claimed in claim 3 is characterized in that, described AD converter is the AD converter of ∑=Δ structure.
8. radio-frequency transmitter as claimed in claim 4, it is characterized in that, at described calibration mode, under the receiving gain of the radio-frequency transmitter of setting, receive calibrating signal and it is down-converted to baseband signal, and carry out the FFT computing and generate the direct current calibration chart by the FFT computing module, described direct current calibration chart is made of the list cell of the corresponding different gains value of some.
9. radio-frequency transmitter as claimed in claim 8, it is characterized in that, the calibrating signal power that utilization obtains and the difference of shifted signal power obtain the corresponding relation of calibrating signal power and AD full scale scale, are scaled the numerical value of direct current signal with respect to AD full scale scale; And, generate each list cell of direct current calibration chart by circulation to the different values of receiving gain sequence.
10. an electronic equipment is characterized in that, has the arbitrary described radio-frequency transmitter of claim 1-9.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104682994A (en) * | 2015-03-10 | 2015-06-03 | 灵芯微电子科技（苏州）有限公司 | Radio frequency chip and system for wireless local area network and broadcast integrated transmission |
| CN105959067A (en) * | 2016-04-22 | 2016-09-21 | 北京联盛德微电子有限责任公司 | Calibration method and device for transmitter chip |
| CN109361417A (en) * | 2018-11-29 | 2019-02-19 | 中电科仪器仪表有限公司 | A kind of signal processing method and system for zero intermediate frequency receiver direct current offset |
| CN110161440A (en) * | 2019-04-29 | 2019-08-23 | 上海东软医疗科技有限公司 | A kind of receiver, signal acceptance method and MR imaging apparatus |
| CN110191080A (en) * | 2011-11-09 | 2019-08-30 | 高通股份有限公司 | Dynamic receiver switching |
| CN113406527A (en) * | 2021-05-13 | 2021-09-17 | 北京北方华创微电子装备有限公司 | Radio frequency power supply control system, calibration method and device thereof, and semiconductor equipment |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6735422B1 (en) * | 2000-10-02 | 2004-05-11 | Baldwin Keith R | Calibrated DC compensation system for a wireless communication device configured in a zero intermediate frequency architecture |
| US7881681B2 (en) * | 2006-08-28 | 2011-02-01 | Mediatek Inc. | Self-calibrating direct conversion transmitter with converting/steering device |
| CN101183877B (en) * | 2007-12-17 | 2013-03-27 | 中兴通讯股份有限公司 | DC offset calibration method and apparatus |
-
2008
- 2008-07-08 CN CN2008101378394A patent/CN101299616B/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110191080A (en) * | 2011-11-09 | 2019-08-30 | 高通股份有限公司 | Dynamic receiver switching |
| CN104682994A (en) * | 2015-03-10 | 2015-06-03 | 灵芯微电子科技（苏州）有限公司 | Radio frequency chip and system for wireless local area network and broadcast integrated transmission |
| CN105959067A (en) * | 2016-04-22 | 2016-09-21 | 北京联盛德微电子有限责任公司 | Calibration method and device for transmitter chip |
| CN109361417A (en) * | 2018-11-29 | 2019-02-19 | 中电科仪器仪表有限公司 | A kind of signal processing method and system for zero intermediate frequency receiver direct current offset |
| CN110161440A (en) * | 2019-04-29 | 2019-08-23 | 上海东软医疗科技有限公司 | A kind of receiver, signal acceptance method and MR imaging apparatus |
| CN113406527A (en) * | 2021-05-13 | 2021-09-17 | 北京北方华创微电子装备有限公司 | Radio frequency power supply control system, calibration method and device thereof, and semiconductor equipment |
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| CN101299616B (en) | 2011-08-17 |
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