CN101453226A - Local oscillation leakage elimination apparatus and method - Google Patents
Local oscillation leakage elimination apparatus and method Download PDFInfo
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Abstract
The invention discloses a device for eliminating local oscillation leakage. During operation, the device comprises: generating an intermediate frequency auxiliary signal with adjustable amplitude and phase in a baseband digital domain and converting the intermediate frequency auxiliary signal into an analog radio-frequency modulation signal; converting the intermediate frequency auxiliary signal into a negative local oscillation signal with the frequency and amplitude identical to those of a local oscillation leakage signal and the phase opposite to that of the local oscillation leakage signal; and offsetting the negative local oscillation signal and the local oscillation leakage signal to realize the function of eliminating local oscillation leakage. The device can carry out dynamic adjustment of signal amplitude and phase in a digital domain through the adoption of a trial-and-error method according to the offset local oscillation leakage state till the local oscillation leakage signal meets requirements. Because the signal offsetting the local oscillation leakage signal is generated in the digital domain, the amplitude and phase of the signal can be adjusted accurately. The device has a simple method and can quickly realize accurate control of local oscillation leakage elimination. In addition, the device does not influence the normal operation of a transmitter during adjustment.
Description
Technical field
The present invention relates to a kind of local oscillation leakage elimination apparatus and method, specifically, relate to the device and method of eliminating the local oscillator leakage signals in the zero intermediate frequency transmitter, can eliminate local-oscillator leakage in real time, reduce the non-useful signal that frequency conversion device produces.
Background technology
At wireless communication field, traditional transmitter is made up of Base Band Unit, D/A conversion unit, converter unit, amplifying unit, filter unit etc.Wherein, transmitter is finished moving signal spectrum by frequency conversion device.In conversion process, can produce some non-useful signals inevitably, for example local-oscillator leakage, other sideband signals, harmonic signal.These non-useful signals can produce different influences in different transmitter architectures.Might have influence on the subsequent power amplifying circuit of transmitter, cause the spectral emission of transmitter not meet correlation standard.In addition, these non-useful signals also might have influence on the signal to noise ratio that transmits, and then have influence on reception, reduce the receiving sensitivity of receiver.
Therefore, in transmitter design, should add corresponding calibration circuit as required, be used for these non-useful signals are suppressed and eliminate, to satisfy the system design demand.Calibration circuit generally includes testing circuit and bucking circuit two parts.Wherein, testing circuit is mainly used in non-useful signal is detected, and detected non-useful signal is offered bucking circuit, thereby bucking circuit is controlled.Therefore, the precision of the detected value of testing circuit acquisition, precision and the accuracy that accuracy directly has influence on bucking circuit.
Existing local oscillator leakage detection circuit mainly adopts the form of analog circuit that local oscillator leakage signals is detected, and this detection method exists precision not high usually, the shortcoming that error is big.Particularly,, compare, be simple and easy to obtain extensive use with, zero intermediate frequency transmitter that cost performance is high with traditional superhet transmitter architecture along with the raising of circuit level and analogue device performance.
Fig. 1 shows the configuration block diagram of the zero intermediate frequency transmitter of prior art.As shown in Figure 1, the zero intermediate frequency transmitter mainly comprises digital baseband processing unit 101, digital to analog converter 102, low pass filter 103, local oscillation signal generator 104, quadrature modulator 105, radio frequency amplifier 106, radio frequency band filter 107, power amplifier 108, band pass filter or duplexer spring 109 and transmitting antenna 110.
In the course of work of transmitter, (wherein I, Q are used for representing the two paths of data signal of quadrature respectively to the quadrature i/q signal of 101 pairs of generations of digital baseband processing unit, I represents in-phase data signal, and Q represents the orthogonal data signal) carry out offering digital to analog converter 102 after interpolation and the Filtering Processing.Digital to analog converter 102 converts digital i/q signal to Simulation with I/Q signal, and Simulation with I/Q signal is offered simulation low-pass filter 103.Simulation with I/Q signal carries out mixing with the carrier signal of the two-way quadrature that provides from local oscillation signal generator 104 quadrature modulator 105 after simulation low-pass filter 103 filtering, superpose then, generates the analog radio frequency modulation signal.The analog radio frequency modulation signal that is generated is input to radio frequency amplifier 106 and amplifies, and then the analog radio-frequency signal through amplifying is offered radio frequency band filter 107.The analog radio frequency modulation signal of 107 pairs of amplifications of radio frequency band filter carries out filtering, obtains the radiofrequency signal that will send, and carries out power amplification through 108 pairs of radiofrequency signals of power amplifier then.To offer band pass filter 109 or duplexer 109 through the radiofrequency signal of power amplification at last, then by transmitting antenna 110 emissions.
Be in the situation of normal operating conditions when the zero intermediate frequency transmitter, because user's useful signal and local oscillator leakage signals are in the same frequency range, can't calibrate local-oscillator leakage in real time, can only when start or under the state that does not have useful subscriber signal to exist, calibrate.
In addition, because manufacturing variation, technology, temperature and the quadrature modulator etc. of peripheral component itself are easy to produce in the course of the work I, Q branch road imbalance, cause local-oscillator leakage.Method in common is to adopt the direct current biasing of adjusting I, Q branch road to reduce local-oscillator leakage.But this method exists algorithm complexity, speed is slow, cost is high problem.
Summary of the invention
The objective of the invention is provides a kind of local oscillation leakage elimination apparatus and method at the problems referred to above, by generating and local oscillator leakage signals has same frequency and amplitude but the opposite negative local oscillation signal of phase place, the negative local oscillation signal that generated and local oscillator leakage signals are offset eliminated local-oscillator leakage.
According to an aspect of the present invention, provide a kind of local oscillation leakage elimination apparatus, comprising: the baseband digital domain part is used for the adjustable digital intermediate frequency auxiliary signal of generation amplitude and phase place, and digital intermediate frequency auxiliary signal and base band data is closed the road; Digital to analog converter, the conversion of signals that is used for closing the road becomes analog signal; Low pass filter is used for the higher harmonic components of filtering analog signal, obtains the analog intermediate frequency auxiliary signal; The local oscillation signal generator is used for providing the local oscillator input signal to quadrature modulator; Quadrature modulator is used for analog intermediate frequency auxiliary signal and the local oscillation signal mixing that provides from described local oscillation signal generator are superposeed then, generates the analog radio frequency modulation signal; First coupler is used for the analog radio frequency modulation signal is coupled to secondary branch road; Frequency mixer is used for carrying out mixing with being coupled to the modulation signal of secondary branch road and frequency that the frequency maker provides, with the frequency down conversion of the auxiliary signal that will comprise in the modulation signal frequency to local oscillation signal; Band pass filter, be used for to through the auxiliary signal filtering of down-conversion to obtain pure negative local oscillation signal; With second coupler, be used for negative local oscillation signal is coupled to main branch road, make the local oscillator leakage signals of negative local oscillation signal and main branch road offset.
According to another aspect of the present invention, provide a kind of local-oscillator leakage removing method, comprise step: the digital intermediate frequency auxiliary signal that generation amplitude and phase place are adjustable, and digital intermediate frequency auxiliary signal and base band data closed the road; The conversion of signals of closing the road is become analog signal; Higher harmonic components in the filtering analog signal obtains the analog intermediate frequency auxiliary signal; The local oscillator input signal is provided; With analog intermediate frequency auxiliary signal and the mixing of local oscillator input signal, superpose then, generate the analog radio frequency modulation signal; The analog radio frequency modulation signal is coupled to main branch road and secondary branch road respectively; The modulation signal that is coupled to secondary branch road is carried out mixing, with the frequency down conversion of the auxiliary signal that will comprise in the modulation signal frequency to local oscillation signal; To through the auxiliary signal filtering of down-conversion to obtain pure negative local oscillation signal; With will bear local oscillation signal and be coupled to main branch road, make negative local oscillation signal and the counteracting of main branch road local oscillator leakage signals.
According to local oscillation leakage elimination apparatus of the present invention, the single frequency point signal that generation amplitude and phase place are adjustable, process is transformed into the negative local oscillation signal that frequency, amplitude are identical, phase place is opposite with local oscillator leakage signals, offsets local oscillator leakage signals, thereby realizes the local-oscillator leakage elimination.
In addition, according to local oscillation leakage elimination apparatus of the present invention, the signal that the same local oscillator leakage signals of generation offsets produces at numeric field, can accurately adjust its amplitude and phase place, realizes the accurately function of control local-oscillator leakage elimination.And the present invention only need adjust the amplitude and the phase place of negative local oscillation signal, and needn't adjust the imbalance of I branch road and Q branch road two-way respectively, thereby it is simple, quick to reach method, saves cost.
Description of drawings
By below in conjunction with description of drawings the preferred embodiments of the present invention, will make above-mentioned and other purpose of the present invention, feature and advantage clearer, wherein:
Fig. 1 is the configuration block diagram that shows the zero intermediate frequency transmitter of prior art;
Fig. 2 shows the configuration block diagram have according to the zero intermediate frequency transmitter of the local oscillation leakage elimination apparatus of the embodiment of the invention;
Fig. 3 is the signal spectrum schematic diagram that shows through after the low pass filter in the transmitter;
Fig. 4 is the signal spectrum schematic diagram that shows through after the quadrature modulator in the transmitter;
Fig. 5 is the signal spectrum schematic diagram that shows through after the band pass filter in the transmitter; With
Fig. 6 is the signal spectrum schematic diagram that shows through after second coupler in the transmitter.
Embodiment
Embodiments of the present invention is described in detail with reference to the accompanying drawings, and having omitted in the description process is unnecessary details and function for the present invention, obscures to prevent that the understanding of the present invention from causing.
Dispose the transmitter of local oscillation leakage elimination apparatus according to an embodiment of the invention below with reference to Fig. 2 description.
Fig. 2 shows the configuration block diagram have according to the zero intermediate frequency transmitter of the local oscillation leakage elimination apparatus of the embodiment of the invention.As shown in Figure 2, according to present embodiment, the transmitter with local oscillation leakage elimination apparatus comprises baseband digital domain part 206, digital to analog converter 207, low pass filter 208, quadrature modulator 209, local oscillation signal generator 210, the first couplers 211, radio frequency amplifier 212, second coupler 213, frequency mixer 214, band pass filter 215, frequency maker 216, radio frequency band filter 217, power amplifier 218, band pass filter or duplexer spring 219, transmitting antenna 220.
Baseband digital domain part 206 produces the digital intermediate frequency auxiliary signal that is used to offset the local oscillator leakage signal.Baseband digital domain part 206 generation amplitudes and the adjustable auxiliary signal of phase place produce the local oscillator that is used to offset the local oscillator leakage signal and reveal offseting signal by according to the local oscillator leakage signal auxiliary signal that produces being carried out amplitude and phase place adjustment.
Specifically, as shown in Figure 2, baseband digital domain part 206 comprises digital intermediate frequency auxiliary signal generation unit 201, amplitude adjustment unit 202, phasing unit 203, base band data generation unit 204 and combiner unit 205.
Local oscillator is described below reveals the operation of canceller.At first, digital intermediate frequency auxiliary signal generation unit 201 is in the intermediate frequency auxiliary signal of a single-frequency point of numeric field structure, as auxiliary signal.The centre frequency of the auxiliary signal of being constructed can be ω
1, the normalized amplitude of I/Q branch road can be G
1, phase place is φ
0Can be illustrated in the single-frequency point intermediate frequency auxiliary signal that numeric field generates with following expression (1).
I
1(t)＝cos(ω
1t) (1)
Q
1(t)＝sin(ω
1t)
The centre frequency of this intermediate frequency auxiliary signal is F1, and the precision that the figure place of data is adjusted by needs is decided, and its frequency spectrum is shown in the F1 signal 302 among Fig. 3.
I
1(t)＝G
1cos(ω
1t) (2)
Q
1(t)＝sin(ω
1t)
Intermediate frequency auxiliary signal through the amplitude adjustment is imported into phasing unit 203.Phasing unit 203 is adjusted the phase of this intermediate frequency auxiliary signal
0, make the true local oscillator leakage signals of the initial phase of intermediate frequency auxiliary signal and Design Theory anti-phase.The intermediate frequency auxiliary signal that the process phase place is adjusted is shown in following expression (3).
I
1(t)＝G
1cos(ω
1t+φ
1) (3)
Q
1(t)＝sin(ω
1t)
In addition, base band data generation unit 204 produces base band data according to normal mode.The centre frequency of base band data is ω
0, I/Q branch road normalization amplitude is G
0, phase place is φ
0, shown in the signal among Fig. 3 301.The base band data that can use following expression (4) expression to produce according to normal mode.
I
0(t)＝G
0cos(ω
0t+φ
0) (4)
Q
0(t)＝sin(ω
0t)
Being noted that the base band data that is produced is not limited to single-carrier signal, also can be multi-carrier signal.If multi-carrier signal, can get one of them carrier wave is example.
Be input to combiner unit 205 from phasing unit 203 and base band data generation unit 204 respectively through the intermediate frequency auxiliary signal of amplitude and phase place adjustment and the base band data that produces according to normal mode.Combiner unit 205 closes the road with the intermediate frequency auxiliary signal and the base band data of input.The signal that closes behind the road is sent to digital to analog converter 207.Intermediate frequency auxiliary signal and base band data that digital to analog converter 207 will close behind the road convert analog signal to.Be noted that digital to analog converter 207 comprises first digital to analog converter and second digital to analog converter, be respectively applied for the signal of conversion I branch road and Q branch road.For simplicity, first digital to analog converter and second digital to analog converter are combined description, and can not influence its operation principle and the misunderstanding that causes operating process.The analog signal that converts to is input to low pass filter 208 according to I branch road and Q branch road, by the higher harmonic components in the low pass filter 208 filtering analog signals, generates analog intermediate frequency auxiliary signal 302 as shown in Figure 3.The centre frequency that the cut-off frequency of low pass filter need be higher than the base band generation is the frequency of the digital intermediate frequency auxiliary signal of F1, so that the intermediate frequency auxiliary signal is passed through.Should be noted that, low pass filter 208 comprises first low pass filter and second low pass filter that respectively signal of I branch road and Q branch road is carried out low-pass filtering, and for simplicity first low pass filter and second low pass filter is combined description.
Be noted that because the data in the auxiliary signal keep the problems such as I/Q branch road imbalance of precision and digital to analog converter, can in auxiliary signal, add DC deviation D
1, in base-band data signal, add DC deviation D
0Therefore, through the composite signal that the road signal has constituted following expression (5) expression that closes after digital-to-analogue conversion and the low-pass filtering.
I(t)＝I
0(t)+I
1(t)＝G
0cos(ω
0t+φ
0)+D
0+G
1cos(ω
1t+φ
1)+D
1 (5)
Q(t)＝Q
0(t)+Q
1(t)＝sin(ω
0t)+sin(ω
1t)
Next, will offer quadrature modulator 209 through the road signal that closes of low-pass filtering.In addition, provide the local oscillator input signal from local oscillation signal generator 210 to quadrature modulator 209.The signal that is input to local oscillation signal generator 104 generations of quadrature modulator 209 is F
LO, its centre frequency is ω
LO, after the phse conversion in the quadrature modulator 209, form orthogonal signalling F
LO_IAnd F
LO_Q, the normalization amplitude is G
LO, phase place is φ
LO, DC deviation is D
LOTherefore, can use the local oscillation signal of following expression (6) expression through the quadrature phase conversion.
F
LO_I＝G
LOcos(ω
LOt+φ
LO)+D
LO (6)
F
LO_Q＝sin(ω
LOt)
Local oscillation signal through above-mentioned quadrature phase conversion is imported into quadrature modulator 209.209 pairs of inputs of quadrature modulator carry out the quadrature modulation conversion by the composite signal of expression formula (5) expression with by the local oscillation signal of expression formula (6) expression, to realize frequency translation.Specifically, at first the signal to input carries out the quadrature variation, promptly, to first and second frequency mixers of quadrature modulator 209, carry out mixing with the carrier signal of the two-way quadrature that provides from local oscillation signal generator 210 through the analog signal of low-pass filtering, superpose then, generate the analog radio frequency modulation signal.Shown in following expression (7).
F
RF＝I(t)×F
LO_I-Q(t)×F
LO_Q
＝[I
0(t)+I
1(t)]×F
LO_I-[Q
0(t)+Q
1(t)]×F
LO_Q (7)
＝[G
0cos(ω
0t+φ
0)+D
0+G
1cos(ω
1t+φ
1)+D
1]×[G
LOcos(ω
LOt+φ
LO)+D
LO]
-[sin(ω
0t)+sin(ω
1t)]×sin(ω
LOt)
Then, to the signal that changes through quadrature, be example with the system of getting upper sideband, after flow component is propped up in filtering through block isolating circuit, can obtain its frequency spectrum local oscillator leakage signals as shown in Figure 4, shown in the label among Fig. 4 401, its centre frequency is F_lo.Can represent this local oscillator leakage signals with following expression (8).
F
LO_leakage＝(D
0+D
1)G
LOcos(ω
LOt+φ
LO) (8)
The frequency of the auxiliary signal of quadrature modulator 209 outputs equals local frequency and adds intermediate frequency.Auxiliary signal F_aux is shown in the label among Fig. 4 403, and the centre frequency that its centre frequency equals local oscillator leakage signals adds the centre frequency of auxiliary signal, that is, and and F_lo+F1.Can use following expression (9) expression auxiliary signal.
Signal through quadrature modulator 209 quadrature modulation is provided for coupler 211.Coupler 211 will comprise that auxiliary signal and local oscillator leakage signal offer by the radio frequency amplifier 212 and second coupler 213, radio frequency band filter 217, power amplifier 218, band pass filter or duplexer spring 219, the main branch road that transmitting antenna 220 constitutes.Simultaneously, coupler 211 will comprise that auxiliary signal and local oscillator leakage signal offer by frequency mixer 214, the secondary branch road that frequency generator 216 and band pass filter 215 constitute.The frequency that frequency mixer 214 will provide by the modulation signal and the frequency maker 216 of coupler 211 inputs is carried out mixing, thereby the frequency of auxiliary signal is carried out down conversion.Specifically, local frequency is set to the centre frequency that the frequency translation of auxiliary signal will be arrived.Set in advance the local oscillation signal that frequency maker 216 produces this frequency, it is identical with the centre frequency of local oscillator leakage signal promptly can the centre frequency of auxiliary signal to be transformed to by mixing.Frequency maker 216 offers frequency mixer 214 with the local oscillation signal that is produced.Frequency mixer 214 carries out the frequency mixing with the local oscillation signal that auxiliary signal and frequency maker 216 provide, and the frequency of auxiliary signal is carried out down-conversion, thereby with the frequency translation of the auxiliary signal position to the frequency of local oscillation signal.Then, will offer centre frequency through the auxiliary signal of down-conversion is F
LOBand pass filter 215.Obtain pure negative local oscillation signal through after the filtering of auxiliary signal by band pass filter 215 of down-conversion.The negative local oscillation signal that is obtained can be used following expression (10) expression.
(10)
For expression formula (10), can be provided with
, wherein C is a constant, ξ (φ
1) and
Be φ
1Function.Owing in said process, signal amplitude has been done normalized, has made auxiliary signal have variable amplitude
A (t)Therefore, can represent this auxiliary signal with following expression (11), its signal spectrum is as the F_aux among Fig. 5 " shown in the signal 501.As can see from Figure 5, through after the filtering of band pass filter 215, obtained pure negative local oscillation signal.
The actual signal that system can be coupled by the feedback loop (not shown) at emission port detects the intensity of local-oscillator leakage and adjusts variation tendency and adjust negative local oscillation signal.During adjustment, can adjust φ
1Value, also can adjust the amplitude of the digital intermediate frequency auxiliary signal of generation
A (t)Thereby, reach the function of offsetting local-oscillator leakage.After this, the negative local oscillation signal that is obtained is coupled to main branch road by second coupler 213, thus with main branch road in the main tributary signal of radio frequency amplifier 212 output in local oscillator leakage signals offset.Can represent this processing procedure with following expression (12).
The signal that second coupler 213 has been offset local oscillator leakage signals offers radio frequency band filter 217.After this, radio frequency band filter 217, power amplifier 218, band pass filter or duplexer spring 219, the operation of transmitting antenna 220 and the radio frequency band filter shown in Fig. 1 107, power amplifier 108, band pass filter or duplexer spring 109 are identical with the operation of transmitting antenna 110.For simplicity, in the description of this omission to it.
According to the present invention, can not cause damage after local oscillator leakage signals is cancelled, and obtain the signal spectrum shown in 601 among Fig. 6 part in the band of useful signal.In addition,, therefore can eliminate, can not produce very big spurious signal by band pass filter because auxiliary signal and useful signal have the distance of one times of IF-FRE.
As an example, the local oscillator leakage signal cancellation element according to present embodiment can be applied to the WCDMA system.Below this is described.For example, in WCDMA four carrier systems, can suppose that in numeric field structure frequency be the intermediate frequency auxiliary signal of the single-frequency point of 140MHz, its frequency spectrum is shown in the digital intermediate frequency auxiliary signal frequency spectrum 302 among Fig. 3.Simultaneously, a carrier wave of getting in four carrier systems according to base band data is an example, and centre frequency is 2.5MHz, shown in the numeral of four carrier waves among Fig. 3 base-band signal spectrum 301.The local oscillator input signal F of quadrature modulator
LOCentre frequency is 2140MHz.Through after the orthogonal transform and frequency spectrum shift of quadrature modulator, getting upper sideband with output signal is example, and after flow component was propped up in filtering through block isolating circuit, the frequency of local oscillator leakage signals was 2140MHz, shown in the local oscillator leakage signals frequency spectrum 401 among Fig. 4.The frequency that the auxiliary signal frequency of modulator output equals local oscillation signal adds the intermediate frequency of auxiliary signal, and therefore the frequency of the auxiliary signal F_aux after the modulation is 2280MHz, shown in the auxiliary signal frequency spectrum 403 among Fig. 4.
By coupler 211, after the signal coupling with modulator output, detecting the local frequency that produces with frequency maker 216 is 140MHz.Signal after the modulation carries out down-conversion after by the local oscillation signal mixing that provides with frequency maker 216, so that the auxiliary signal frequency is shifted to 2280MHz ± 140MHz.After this by band pass filter the allochthonous auxiliary signal of frequency is carried out bandpass filtering, producing clean spectrum is the negative local oscillation signal of 2140MHz, as the F_aux among Fig. 5 " bear shown in the local oscillation signal 501.
This negative local oscillation signal is coupled to main branch road, and the local-oscillator leakage identical with the frequency in the main tributary signal, that phase place is opposite offsets, signal spectrum that obtains such as the transmission signal 601 among Fig. 6.
After this, the WCDMA system can adopt trial-and-error method dynamically to adjust the amplitude and the phase place of intermediate frequency auxiliary signal at numeric field according to the local-oscillator leakage situation after offsetting, till the signal of local-oscillator leakage can satisfy system requirements.In this adjustment process, do not influence normal business.
The flow process of examining the method for eliminating local oscillator leakage signals according to the present invention is described below.Baseband digital domain part 206 is put digital intermediate frequency auxiliary signal in numeric field generation amplitude and the adjustable single-frequency of phase place, closes the road through the auxiliary signal of amplitude and phase place adjustment and the base band data that produces according to normal mode.Signal behind the involutory road carries out digital-to-analogue conversion, thereby makes the conversion of signals of closing the road become analog signal.After this, resulting analog signal is carried out low-pass filtering,, generate the analog intermediate frequency auxiliary signal with the higher harmonic components in the filtering analog signal.The local oscillation signal of the analog signal of 209 pairs of inputs of quadrature modulator and 210 inputs of local oscillation signal generator carries out quadrature modulation, to obtain radiofrequency signal and to realize frequency translation.The frequency that the auxiliary signal frequency of modulator output equals local oscillation signal adds the intermediate frequency of auxiliary signal,
By first coupler 211 radiofrequency signal is shunted to main tributary signal and secondary tributary signal.It is the signal at center that the frequency that frequency mixer 214 utilizes frequency maker 216 to provide is downconverted into secondary tributary signal with the local oscillation signal.After this by band pass filter the allochthonous auxiliary signal of frequency is carried out bandpass filtering, produce pure negative local oscillation signal.This negative local oscillation signal is coupled to main branch road, offsets with the local-oscillator leakage that the amplitude in the main tributary signal is identical with frequency, phase place is opposite.At last, the signal that will eliminate the local oscillator leakage signal by transmitting antenna is launched.
According to the present invention, the signal that offsets with local oscillator leakage signals produces at numeric field, can accurately adjust its amplitude and phase place, realizes that accurately the control local-oscillator leakage is eliminated function.In addition, invention only needs to adjust the amplitude and the phase place of this signal, and needn't adjust the imbalance of I branch road and Q branch road two-way respectively, so method is simple, quick, saves cost.
So far invention has been described in conjunction with the preferred embodiments.It should be appreciated by those skilled in the art that under the situation that does not break away from the spirit and scope of the present invention, can carry out various other change, replacement and interpolations.Therefore, scope of the present invention should not be understood that to be limited to above-mentioned specific embodiment, and should be limited by claims.
Claims (8)
1. local oscillation leakage elimination apparatus comprises:
Baseband digital domain part (206) is used for the adjustable digital intermediate frequency auxiliary signal of generation amplitude and phase place, and digital intermediate frequency auxiliary signal and base band data is closed the road;
Digital to analog converter (207), the conversion of signals that is used for closing the road becomes analog signal;
Low pass filter (208) is used for the higher harmonic components of filtering analog signal, obtains the analog intermediate frequency auxiliary signal;
Local oscillation signal generator (210) is used for providing the local oscillator input signal to quadrature modulator (209);
Quadrature modulator (209) is used for analog intermediate frequency auxiliary signal and the local oscillation signal mixing that provides from described local oscillation signal generator are superposeed then, generates the analog radio frequency modulation signal;
First coupler (211) is used for the analog radio frequency modulation signal secondary branch road that is coupled;
Frequency mixer (214) is used for carrying out mixing with being coupled to the modulation signal of secondary branch road and signal that frequency maker (216) provides, with the frequency down conversion of the auxiliary signal that will comprise in the modulation signal frequency to local oscillation signal;
Band pass filter (215), be used for to through the auxiliary signal filtering of down-conversion to obtain pure negative local oscillation signal; With
Second coupler (213) is used for negative local oscillation signal is coupled to main branch road, makes negative local oscillation signal and main branch road local oscillator leakage signals offset.
2. local oscillation leakage elimination apparatus according to claim 1, wherein said baseband digital domain partly comprises:
Amplitude adjustment unit (202) is used to adjust the amplitude of intermediate frequency auxiliary signal, makes the amplitude normalization of the intermediate frequency auxiliary signal of homophase and quadrature branch; With
Phasing unit (203) is used to adjust the phase place of intermediate frequency auxiliary signal, so that the true local oscillator leakage signals of the initial phase of intermediate frequency auxiliary signal and Design Theory is anti-phase.
3. local oscillation leakage elimination apparatus according to claim 1, wherein said baseband digital domain partly comprise digital intermediate frequency auxiliary signal generation unit (201), are used to produce the intermediate frequency auxiliary signal of single-frequency point.
4. local oscillation leakage elimination apparatus according to claim 1, the cut-off frequency of wherein said low pass filter (208) are higher than the frequency of the digital intermediate frequency auxiliary signal of base band generation, so that the intermediate frequency auxiliary signal is passed through.
5. local oscillation leakage elimination apparatus according to claim 1 is wherein adjusted phase place and the normalized range value of bearing local oscillation signal, makes negative local oscillation signal can offset local-oscillator leakage.
6. local-oscillator leakage removing method comprises step:
The digital intermediate frequency auxiliary signal that generation amplitude and phase place are adjustable, and digital intermediate frequency auxiliary signal and base band data closed the road;
The conversion of signals of closing the road is become analog signal;
Higher harmonic components in the filtering analog signal obtains the analog intermediate frequency auxiliary signal;
The local oscillator input signal is provided;
With analog intermediate frequency auxiliary signal and the mixing of local oscillator input signal, superpose then, generate the analog radio frequency modulation signal;
The analog radio frequency modulation signal is coupled to main and secondary branch road respectively;
The modulation signal that is coupled to secondary branch road is carried out mixing, with the frequency down conversion of the auxiliary signal that will comprise in the modulation signal frequency to local oscillation signal;
To through the auxiliary signal filtering of down-conversion to obtain pure negative local oscillation signal; With
To bear local oscillation signal and be coupled to main branch road, and make negative local oscillation signal and main branch road local oscillator leakage signals offset.
7. method according to claim 6 further comprises:
Adjust the amplitude of intermediate frequency auxiliary signal, make the step of amplitude normalization of the intermediate frequency auxiliary signal of homophase and quadrature branch; With
Adjust the phase place of intermediate frequency auxiliary signal, so that the anti-phase step of true local oscillator leakage signals of the initial phase of intermediate frequency auxiliary signal and Design Theory.
8. method according to claim 6 further comprises phase place and the normalized range value of adjusting negative local oscillation signal, makes negative local oscillation signal can offset the step of local oscillator leakage signals.
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