A kind of ultra broadband low-power radio frequency signal generator and method thereof
Technical field
The present invention relates to radar driver technical field, particularly a kind of synthetic-aperture radar (Synthetic Aperture Radar-SAR) ultra broadband low-power radio frequency signal generator and method thereof.
Background technology
Driver is an important component part of synthetic-aperture radar.It is used for producing the needed low-power radio frequency signal of polarization sensitive synthetic aperture radar system work.In polarization sensitive synthetic aperture radar system, range resolution is determined by the bandwidth transmitting.Along with the development of technology, the resolution of user's Technologies Against Synthetic Aperture Radar system has proposed the requirement of centimetre magnitude, brings the signal bandwidth of radar system to reach several GHz for this reason.
The development of large scale integrated circuit technology causes high-speed figure analog converter (Digital to Analog Convertor-DAC) and the fast development of Direct Digital Frequency Synthesizers (Direct Digital Frequency Synthesis-DDS) technology, but for practical application, an always poor order of magnitude in performance.To this, the generation scheme of traditional low-power radio frequency signal is frequency multiplication, and it realizes theory diagram as shown in Figure 1.First by the DAC of a high-precision high-speed, produced the intermediate-freuqncy signal of an arrowband, then, by after several times frequency multiplication, bandpass filtering and amplification, obtain the low-power radio frequency signal of required bandwidth.
Frequency multiplication scheme is the main flow scheme that produces at present ultra-wideband radar signal.It simple in structure, the signal Out-of-band rejection degree of generation is higher, and flatness in signal band is good.But its shortcoming is: volume is large, and power consumption is high; The number of times of frequency multiplication is more, introducing spuious many, the poor linearity of signal.
Summary of the invention
In order to overcome the not high enough and bulky shortcoming of frequency multiplication scheme of current DAC sampling rate, the invention provides a kind of ultra broadband low-power radio frequency signal generator.
Ultra broadband low-power radio frequency signal generator disclosed by the invention, it comprises:
Base band sources, it is for generation of continuous baseband signal;
Switch, it is divided into a plurality of parts by described baseband signal from time domain for controlling;
Quadrature modulator, it uses different radio-frequency (RF) local oscillator that the baseband signal of be divided into a plurality of parts is modulated into a plurality of radiofrequency signals;
Compositor, it for synthesizing described a plurality of radiofrequency signals one road ultra broadband low-power radio frequency signal in time domain.
Wherein, this signal generator is for radar driver.
Wherein, it obtains ultra broadband low-power radio frequency signal by time domain multi channel signals synthetic method.
Wherein, described base band sources adopts waveform synthetic method to produce baseband signal.
Wherein, described baseband signal is formed by connecting by the linear FM signal of a plurality of identical characteristics.
Wherein, described a plurality of radiofrequency signal is the radiofrequency signal with different center frequency same band.
What wherein, described base band sources produced is I and the Q signal of two-way quadrature.
The invention also discloses a kind of ultra broadband low-power radio frequency signal production method, it comprises:
Step 1, base band sources produce baseband signal;
Step 2, described baseband signal is divided into a plurality of parts from time domain, forms a plurality of zero intermediate frequency linear FM signals;
Step 3, use different radio-frequency (RF) local oscillator that described a plurality of zero intermediate frequency linear FM signals are carried out to orthogonal modulation, form a plurality of radiofrequency signals;
Step 4, described a plurality of radiofrequency signals are synthesized to a ultra broadband low-power radio frequency signal.
Wherein, by time domain multi channel signals synthetic method, obtain ultra broadband low-power radio frequency signal.
Wherein, described base band sources adopts waveform synthetic method to produce baseband signal.
Ultra broadband low-power radio frequency signal generator provided by the invention has advantages of following:
1) it need not improve under the prerequisite of high-speed DAC conversion ratio, and the method synthetic by multi-channel wide band signal produces ultra broadband low-power radio frequency signal;
2) signal quality producing than frequency multiplication scheme is high;
3) volume is little, low in energy consumption.
Accompanying drawing explanation
Fig. 1 shows traditional ULTRA-WIDEBAND RADAR low-power radio frequency signal generator theory diagram;
Fig. 2 shows the composition frame chart of ultra broadband low-power radio frequency signal generator in the present invention;
Fig. 3 shows the workflow diagram of ultra broadband low-power radio frequency signal generator in the present invention;
Fig. 4 shows the principle of work block diagram of base band sources in the present invention;
Fig. 5 (a)-(c) shows time domain waveform and the spectrogram of the baseband signal that in the present invention, base band sources produces;
Fig. 6 shows the spectrogram of ultra-wide band radio-frequency signal in the present invention.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, the specific embodiment testing the speed below in conjunction with traffic, and with reference to accompanying drawing, the present invention is described in more detail.
Fig. 2 shows the structural drawing of a kind of ultra broadband low-power radio frequency signal generator disclosed by the invention.As shown in Figure 2, this generator comprises the parts such as base band sources, switch, quadrature modulator and broadband signal compositor.First base band sources produces N connected two-way quadrature I and Q signal, then in first linear FM signal valid period, switch is communicated with the baseband signal of output with first quadrature modulator, the orthogonal modulation of realization and first radio-frequency (RF) local oscillator, obtains first radiofrequency signal; Second linear FM signal valid period, switch is communicated with the baseband signal of output with second quadrature modulator, and the orthogonal modulation of realization and second radio-frequency (RF) local oscillator, obtains second radiofrequency signal; The like, N linear FM signal valid period, switch is communicated with the linear FM signal of output with N quadrature modulator, and the orthogonal modulation of realization and N radio-frequency (RF) local oscillator, obtains N radiofrequency signal.Be equivalent under the control of switch, baseband signal is divided into N connected part of front and back from time domain, then uses different radio-frequency (RF) local oscillator f
l1~f
lN(bandwidth that the difference on the frequency between radio-frequency (RF) local oscillator is baseband signal), is directly modulated into the radiofrequency signal with different center frequency same band by N baseband signal, finally by compositor, N radiofrequency signal is concerned with and synthesizes a road ULTRA-WIDEBAND RADAR radiofrequency signal.This signal generator is mainly used in radar driver, and described base band sources adopts waveform synthetic method to produce baseband signal, and described baseband signal is formed by connecting by the linear FM signal of N identical characteristics.
The technical solution adopted for the present invention to solve the technical problems is: time domain multi-channel wide band signal is synthetic.In synthetic-aperture radar, generally adopt linear FM signal as transmitting, the frequency of this signal is linear change in time.First, producing N bandwidth is B, the zero intermediate frequency linear FM signal that pulsewidth is τ; Then, with the radio-frequency (RF) local oscillator signal of N the B bandwidth of being separated by, baseband signal is modulated into radiofrequency signal; Finally this N radiofrequency signal is synthesized to a signal, just obtained the ultra broadband low-power radio frequency signal of NB bandwidth.
Fig. 3 shows the ultra broadband low-power radio frequency signal method for generation process flow diagram that the present invention proposes.As shown in Figure 3, concrete implementation step is as follows:
The first step: by base band sources, produce two baseband signals, their bandwidth identical (800MHz), pulsewidth is 8 microseconds, the form of signal is linear FM signal;
Second step: with switch, these two baseband signals are separated from time domain, obtain the baseband signal that two-way staggered on the time;
The 3rd step: by the radio-frequency (RF) local oscillator (15.2GHz and 16GHz) of two 800MHz of being separated by, two baseband signals are carried out respectively to orthogonal modulation, obtain two radiofrequency signals, its frequency range is respectively: 14.8GHz-15.6GHz, 15.6GHz-16.4GHz;
The 4th step: two radiofrequency signals are synthesized in time domain, obtain last low-power radio frequency signal, its frequency range is: 14.8GHz-16.4GHz.
Fig. 4 shows the principle of work block diagram of base band sources generation baseband signal in the present invention.What in the present invention, adopt as shown in Figure 4, is waveform synthetic method.First use Matlab software to produce digital waveform data file; Then by data file in FPGA programming procedure, be embedded in the built-in RAM of FPGA, with FPGA program, be together cured in configuring chip.After powering on, under the control of pulse repetition rate (Pu l se Repeative Frequency-PRF), FPGA is reading number base band data from embedded RAM, then given fast two-way DAC chip, by DAC chip, under high-frequency clock effect, convert quadrature I and the Q signal of simulation to.Make great advantage in this way be: can carry out predistortion to Wave data, with the Amplitude phase distortion existing in this bucking-out system passage.
Fig. 5 shows time domain waveform and its spectrogram of the baseband signal that in the present invention, base band sources produces.Wherein (a) represents the time domain waveform of I signal; (b) represent the time domain waveform of Q signal; (c) represent the frequency spectrum of baseband signal.The present invention only uses a base band sources, main cause: 1) single base band sources is low in energy consumption, volume is little; 2) synchro control between a plurality of base band sources is more difficult; 3) a plurality of baseband signal high conformities that produced by a base band sources.
Fig. 6 shows the spectrogram of low-power radio frequency signal in the present invention.Its centre frequency is 15.6GHz, and bandwidth is 1.6GHz, and inband flatness is 2dB, and Out-of-band rejection degree is > 40dB, can meet well the requirement of polarization sensitive synthetic aperture radar system.
Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of making, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.