CN113783637B - Radio astronomical signal receiving device with separated sidebands - Google Patents

Abstract

The invention relates to a radio astronomical signal receiving device with a sideband separation framework, which comprises a feed source, an amplifier, an electric bridge, a first intermediate frequency mixer, a second intermediate frequency mixer, a first intermediate frequency amplifier, a second intermediate frequency amplifier, a first intermediate frequency filter, a local oscillator, a first intermediate frequency analog-to-digital converter, a second intermediate frequency analog-to-digital converter and a digital signal processing unit based on an FPGA, wherein radio astronomical signals are converged to the feed source through the radio astronomical telescope and are divided into two orthogonal signals through the amplifier and the electric bridge, and the two orthogonal signals are respectively output into an upper sideband signal and a lower sideband signal through the intermediate frequency mixer, the intermediate frequency amplifier and the intermediate frequency filter, and then through the analog-to-digital converter and the signal processing unit based on the FPGA. The device compensates unbalance of the phase and amplitude of the analog circuit part through the calibration of the signal processing unit based on the FPGA, improves the sideband suppression rate of the signal receiving device, and optimizes the performance of the receiving device. The method can solve the defects of low sideband suppression rate, complexity and huge faced by the traditional receiver system of the analog sideband separation architecture.

Description

A radio astronomy signal receiving device with sideband separation

technical field

The invention relates to a radio astronomy signal receiving device with sideband separation, which is specially used in the field of radio astronomy.

Background technique

Improving the sensitivity of radio telescopes has always been a research focus and hotspot in the field of radio astronomy. The signal receiving device is an important part of the radio telescope, and its performance is an important factor affecting its sensitivity. Compared with single-sideband and double-sideband configurations, the preferred structure of a radio astronomy heterodyne receiver is a sideband split architecture. In a wide frequency range, sideband separation receivers are very suitable for complex astronomical observations, so they are widely used in the field of radio astronomy observations. Their main advantages over double sideband receivers are the avoidance of spectral aliasing and the ability to reduce system temperature. With the development of related technologies, the noise temperature index of low-temperature heterodyne receivers is rapidly approaching the basic limit, but one of the important indexes - sideband suppression rate still has room for improvement. Since it is extremely difficult to maintain low amplitude and phase imbalance in a large radio frequency and intermediate frequency bandwidth, traditional simulation methods can only achieve a low sideband suppression rate, which is far from meeting the needs of astronomical observations.

In addition, broadband and ultra-wideband receivers need to undergo multiple frequency mixing and tuning to obtain the signal of the desired observation frequency. Each frequency conversion must be filtered and amplified to eliminate signal aliasing and level compensation, making the receiver very large and complex. The receiver device of the sideband separation architecture implemented in the traditional analog method needs to be connected to a bridge after frequency mixing to realize the separation of the upper and lower sideband signals. A radio astronomy signal receiving device with sideband separation designed in the present invention compensates and calibrates the phase and amplitude imbalance generated by the front-end analog circuit in the digital domain, thereby realizing the separation of the upper and lower sideband signals. This method greatly improves the The sideband suppression ratio of the receiver. At the same time, this design reduces the use of hardware components in the front-end analog circuit of the device by realizing the separation of upper and lower sidebands in the digital domain, which is of great significance for reducing the volume of multi-beam and phased array feed receivers.

Contents of the invention

The object of the present invention is to provide a radio astronomy signal receiving device with sideband separation, which device is composed of feed source, amplifier, electric bridge, first and second intermediate frequency mixer, first and second intermediate frequency amplifier, the first The first and second intermediate frequency filters, the local oscillator, the first and second intermediate frequency analog-to-digital converters, and the digital signal processing unit based on FPGA, the radio astronomy signal is converged to the feed source through the radio astronomy telescope, and then divided by the amplifier and the bridge. It is two orthogonal signals. The two signals are mixed, amplified, and filtered, and then passed through an analog-to-digital converter and an FPGA-based digital signal processing unit to output signals with separated upper and lower sidebands. The device calibrates and compensates the phase and amplitude imbalance of the analog circuit part through FPGA-based signal processing unit calibration, improves the sideband suppression rate of the signal receiving device, and optimizes the performance of the receiving device. It can solve the shortcomings of low sideband suppression rate and complex and huge system faced by the receiver system of the traditional analog sideband separation architecture.

A radio astronomy signal receiving device with sideband separation according to the present invention is composed of a feed source, a radio frequency filter, a radio frequency amplifier, an electric bridge, a first and a second intermediate frequency mixer, a first and a second intermediate frequency Amplifier, first and second intermediate frequency filter, local oscillator, power splitter, first and second analog-to-digital converter and digital signal processing unit based on FPGA, feed source (1), radio frequency filter (2), The radio frequency amplifier (3) and the electric bridge (4) are connected in series successively, the first output end of the electric bridge (4) is connected with the input end of the first intermediate frequency mixer (5), and the second output end of the electric bridge (4) is connected with the first intermediate frequency mixer (5). The input terminals of the two intermediate frequency mixers (51) are connected; the output terminals of the first intermediate frequency mixer (5) are successively connected with the first intermediate frequency amplifier (6), the first intermediate frequency filter (7) and the first analog-to-digital converter The input terminal of (8) is connected in series with the signal processing unit (9) based on FPGA; the output terminal of the second intermediate frequency mixer (51) is connected with the second intermediate frequency amplifier (61), the second intermediate frequency filter (71) successively ) and the second analog-to-digital converter (81) input end are connected in series, and are connected with the signal processing unit (9) based on FPGA; The input end of the harmonic suppression power splitter (10) is connected with the local oscillator (11), and the harmonic The first output end of the suppression power divider (10) is connected to the comparison signal input end of the first intermediate frequency mixer (5), and the second output end of the harmonic suppression power divider (10) is connected to the second intermediate frequency mixer (51 ) is connected to the comparison signal input terminal; FPGA-based signal processing unit (9) includes the first multinomial filtering module (12), the second multinomial filtering module (121), internal memory (13) and calibration processing module (14), The first polynomial filter module (12) and the second polynomial filter module (121) are made up of FIR filter and FFT transform respectively; Concrete operation is carried out according to the following steps:

a. The radio astronomy signal enters the feed source (1) after being converged by the telescope, and then is divided into two orthogonal signals after passing through the radio frequency filter (2), the radio frequency amplifier (3) and the electric bridge (4);

B. The two-way orthogonal signals in step a are down-converted into two-way orthogonal intermediate frequency signals through the first mixer (5) and the second mixer (51) respectively;

c. After passing the two-way orthogonal intermediate frequency signals in step b respectively through the first intermediate frequency amplifier (6), the second intermediate frequency amplifier (61), the first intermediate frequency filter (7) and the second intermediate frequency filter (71), Enter the first analog-to-digital converter (8) and the second analog-to-digital converter (81) to convert into two orthogonal digital signals;

D, the two-way orthogonal digital signal in the step c is processed through the signal processing unit (9) based on FPGA, based on the first polyphase filter module (12) and the second polyphase filtering module (12) in the signal processing unit (9) based on FPGA The phase filter module (121) divides the two-way orthogonal digital signals into n frequency channel signals respectively, and performs fast Fourier transformation, and the calibration processing module (14) performs fast Fourier transformation on the multi-channel signals Calibration processing of amplitude and phase calculates the upper sideband signal and the lower sideband signal of the output sideband separation respectively.

The calibration processing module (14) described in step d reads the calibration coefficients of each frequency channel in the memory module (13), and performs calibration calculations on corresponding channel signals respectively to obtain calibrated multi-channel signals;

The calibration coefficients are pre-injected into the test signals of n frequency channels at the input end of the radio frequency filter (2) in advance, after being processed by the first polynomial filtering module (12) and the second polynomial filtering module (121), Obtain the signal complex values of the two orthogonal signals in each frequency channel, and then calculate the calibration coefficient of each frequency channel, and generate the calibration coefficient file.

A radio astronomy signal receiving device with sideband separation according to the present invention, said FPGA-based signal processing unit (9) in the device includes a first polyphase filter module (12), a second polyphase filter module (121 ), memory module (13) and calibration processing module (14), its processing steps:

The first polyphase filtering module (12) and the second polyphase filtering module (121) respectively divide the two-way quadrature signals from the first analog-to-digital converter (8) and the second analog-to-digital converter (81) into n frequency channel signals, and through fast Fourier transform, output complex numbers X ₁ (i) and X ₂ (i), wherein i=0, 1, 2, ..., n-1;

The calibration processing module (14) reads the calibration coefficients C ₁ (i), C ₂ (i), C ₃ (i) and C ₄ (i) of n frequency channels from the memory (13), and calculates and calibrates them respectively Output the separated upper and lower sideband signal data: upper sideband signal data=X ₁ (i)c ₁ (i)+X ₂ (i)C ₂ (i), lower sideband signal data=X ₁ (i)C ₃ (i)+ _X2 (i) _C4 (i);

The acquisition of the calibration coefficients: at the input end of the radio frequency filter (2) of the radio astronomy signal receiving device of the sideband separation architecture, sequentially inject test signals of n frequency channels; in the first polynomial filter (12 ) and the output terminals of the second polynomial filter (121) will obtain the signal complex value X ₁ (i)=A ₁ (i)+jB ₁ (i) and X of the two-way quadrature signal in each frequency channel respectively ₂ (i)=A ₂ (i)+jB ₂ (i), where i=0, 1, 2, ..., n-1, calculated by the following formula,

C₁(i)＝C₄(i)＝1+0j，即得到每个频率通道的校准系数C₁(i)，C₂(i)，C₃(i)和C₄(i)。

C ₁ (i)=C ₄ (i)=1+0j, that is, the calibration coefficients C ₁ (i), C ₂ (i), C ₃ (i) and C ₄ (i) of each frequency channel are obtained.

Compared with the prior art, the present invention has the remarkable advantages that: by calibrating and compensating the amplitude and phase imbalance generated by the front-end analog circuit part in the digital domain, the sideband suppression ratio of the signal receiving device is greatly improved, and at the same time, due to the reduction of the front-end The use of analog parts can reduce the design size of the receiving device.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention;

FIG. 2 is a schematic structural diagram of an FPGA-based signal processing unit of the present invention.

Detailed ways

A radio astronomy signal receiving device with sideband separation according to the present invention is composed of a feed source, a radio frequency filter, a radio frequency amplifier, an electric bridge, a first and a second intermediate frequency mixer, a first and a second intermediate frequency Amplifier, first and second intermediate frequency filter, local oscillator, power divider, first and second analog-to-digital converter and digital signal processing unit based on FPGA, feed source 1, radio frequency filter 2, radio frequency amplifier 3 and The electric bridge 4 is connected in series successively, the first output end of the electric bridge 4 is connected with the input end of the first intermediate frequency mixer 5, the second output end of the electric bridge 4 is connected with the input end of the second intermediate frequency mixer 51; the first intermediate frequency The output terminal of the mixer 5 is connected in series with the input terminals of the first intermediate frequency amplifier 6, the first intermediate frequency filter 7 and the first analog-to-digital converter 8 in turn, and is connected with the signal processing unit 9 based on FPGA; the second intermediate frequency mixer The output end of the frequency converter 51 is connected in series with the second intermediate frequency amplifier 61, the second intermediate frequency filter 71 and the input end of the second analog-to-digital converter 81 successively, and is connected with the signal processing unit 9 based on FPGA; Harmonic suppression power divider 10 The input end of the harmonic suppression power divider 10 is connected to the local oscillator 11, the first output end of the harmonic suppression power divider 10 is connected to the comparison signal input end of the first intermediate frequency mixer 5, and the second output end of the harmonic suppression power divider 10 is connected to the second intermediate frequency The comparison signal input terminal of mixer 51 is connected; Signal processing unit 9 based on FPGA comprises the first multinomial filtering module 12, the second multinomial filtering module 121, memory 13 and calibration processing module 14, the first multinomial filtering module 12 And the second polynomial filtering module 121 is made up of FIR filter and FFT transformation respectively; Concrete operation is carried out according to the following steps:

a. The radio astronomy signal enters the feed source 1 after being converged by the telescope, and then is divided into two orthogonal signals after passing through the radio frequency filter 2, the radio frequency amplifier 3 and the electric bridge 4;

b. The two-way orthogonal signals in step a are down-converted into two-way orthogonal intermediate frequency signals through the first mixer 5 and the second mixer 51 respectively;

c. After passing the two-way orthogonal intermediate frequency signals in step b respectively through the first intermediate frequency amplifier 6, the second intermediate frequency amplifier 61, the first intermediate frequency filter 7 and the second intermediate frequency filter 71, enter the first analog-to-digital converter 8 and the second analog-to-digital converter 81 into two orthogonal digital signals;

D, the two-way orthogonal digital signals in step c are processed through the signal processing unit 9 based on FPGA, and the first polyphase filtering module 12 and the second polyphase filtering module 121 in the signal processing unit 9 based on FPGA respectively The two-way orthogonal signals from the first analog-to-digital converter 8 and the second analog-to-digital converter 81 are respectively divided into n frequency channel signals, and are subjected to fast Fourier transformation, and the calibration processing module 14 pairs are subjected to fast Fourier transformation. The final multi-channel signal is subjected to amplitude and phase calibration processing, and is calculated and calibrated to output the upper sideband signal and the lower sideband signal with sideband separation;

The calibration processing module 14 described in step d reads the calibration coefficients of each frequency channel in the memory module 13, and performs calibration calculations on the corresponding channel signals respectively to obtain calibrated multi-channel signals;

The calibration coefficients are pre-injected into the test signals of n frequency channels at the input end of the radio frequency filter 2 in advance, and after being processed by the first polynomial filter module 12 and the second polynomial filter module 121, two orthogonal channels are obtained. The signal complex value of each signal in each frequency channel is calculated to obtain the calibration coefficient of each frequency channel;

As shown in Figure 1, the radio astronomy signal enters the feed source 1 after being converged by the telescope, and is divided into two orthogonal signals after passing through the radio frequency filter 2, the radio frequency amplifier 3 and the electric bridge 4;

Two paths of orthogonal signals are respectively down-converted by the first intermediate frequency mixer 5 and the second intermediate frequency mixer 51 into two paths of orthogonal intermediate frequency signals;

Two paths of orthogonal intermediate frequency signals respectively pass through the first intermediate frequency amplifier 6 and the second intermediate frequency amplifier 61, the first intermediate frequency filter 7 and the second intermediate frequency amplifier 71, and then enter the first analog-to-digital converter 8 and the second analog-to-digital converter 81 Converted into two orthogonal digital signals;

The two-way orthogonal digital signals are processed by the signal processing unit 9 based on the FPGA, and the first polyphase filtering module 12 and the second polyphase filtering module 121 in the signal processing unit 9 based on the FPGA respectively receive the 8 and the two-way orthogonal signals of the second analog-to-digital converter 81 are respectively divided into n frequency channel signals, and fast Fourier transform is performed, and the calibration processing module 14 performs amplitude analysis on the multi-channel signals after fast Fourier transform and phase calibration processing, and respectively calculate and calibrate the upper sideband signal and the lower sideband signal of the sideband separation;

Referring to Fig. 2, the signal processing unit 9 based on FPGA comprises the first polyphase filter module 12, the second polyphase filter module 121, memory module 13 and calibration processing module 14; The first polyphase filter module 12 and the second polyphase filter The module 121 is composed of FIR filter and FFT transform respectively, and the FIR filter divides the two-way orthogonal signals from the analog-to-digital converter into n channels respectively; each channel signal of the two-way orthogonal signals is transformed by FFT. The signals are respectively represented by X ₁ (i) and X ₂ (i), wherein i=0, 1, 2, . . . , n-1; the calibration processing module 14 reads the calibration coefficients of each frequency channel in the memory 13, Calculation and calibration processing is performed on the complex signals X ₁ (i) and X ₂ (i), and the calculation formulas are as formulas (1) and (2):

Each channel signal of the upper sideband = X ₁ (i)×C ₁ (i)+X ₂ (i)×C ₂ (i) (1)

Signals of each channel in the lower sideband = X ₁ (i)×C ₃ (i)+X ₂ (i)×C ₄ (i) (2)

The acquisition of the calibration coefficient needs to inject the test signals of n frequency channels into the input end of the radio frequency filter 2 shown in FIG. Signal complex values X ₁ (i)=A ₁ ( _{i)+jB 1 (i) and X 2 (i)=A 2 ( i} )+jB ₂ (i ), i=0, 1, 2, ..., n-1; the calibration coefficients C ₁ (i), C ₂ (i), C ₃ (i) and C are calculated by formulas (3) and (4) ₄ (i):

当接收装置本振11的频率和功率发生变化时，需要重新获取新的校准系数。Wherein, C ₁ (i)=C ₄ (i)=1+0j,

When the frequency and power of the local oscillator 11 of the receiving device change, new calibration coefficients need to be acquired again.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (3)

1. A radio astronomy signal receiving device with sideband separation, characterized in that the device is composed of a feed source, a radio frequency filter, a radio frequency amplifier, an electric bridge, the first and the second intermediate frequency mixer, the first and the second IF amplifier, first and second IF filter, local oscillator, power divider, first and second analog-to-digital converter and FPGA-based digital signal processing unit, feed source (1), radio frequency filter (2) , the RF amplifier (3) and the electric bridge (4) are connected in series in sequence, the first output end of the electric bridge (4) is connected to the input end of the first intermediate frequency mixer (5), and the second output end of the electric bridge (4) is connected to the The input terminal of the second intermediate frequency mixer (51) is connected; the output terminal of the first intermediate frequency mixer (5) is sequentially connected with the first intermediate frequency amplifier (6), the first intermediate frequency filter (7) and the first analog-to-digital conversion The input terminal of the device (8) is connected in series with the signal processing unit (9) based on FPGA; the output terminal of the second intermediate frequency mixer (51) is sequentially connected with the second intermediate frequency amplifier (61), the second intermediate frequency filter ( 71) is connected in series with the input end of the second analog-to-digital converter (81), and is connected with the FPGA-based signal processing unit (9); the input end of the harmonic suppression power divider (10) is connected with the local oscillator (11), and the harmonic The first output terminal of the harmonic suppression power divider (10) is connected to the comparison signal input terminal of the first intermediate frequency mixer (5), and the second output terminal of the harmonic suppression power divider (10) is connected to the second intermediate frequency mixer ( 51) is connected to the comparison signal input terminal; the FPGA-based signal processing unit (9) includes a first polynomial filtering module (12), a second polynomial filtering module (121), a memory (13) and a calibration processing module (14) , the first polynomial filtering module (12) and the second polynomial filtering module (121) are composed of FIR filter and FFT transformation respectively; the specific operation is carried out according to the following steps: a. The radio astronomy signal enters the feed source (1) after being converged by the telescope, and then is divided into two orthogonal signals after passing through the radio frequency filter (2), radio frequency amplifier (3) and electric bridge (4); b. Down-converting the two orthogonal signals in step a into two orthogonal intermediate frequency signals through the first mixer (5) and the second mixer (51); c. After passing the two orthogonal intermediate frequency signals in step b through the first intermediate frequency amplifier (6), the second intermediate frequency amplifier (61), the first intermediate frequency filter (7) and the second intermediate frequency filter (71), Enter the first analog-to-digital converter (8) and the second analog-to-digital converter (81) to convert into two orthogonal digital signals; d. The two-way orthogonal digital signals in step c are processed by an FPGA-based signal processing unit (9), and the first polyphase filtering module (12) and the second polyphase filtering module (12) in the FPGA-based signal processing unit (9) The phase filtering module (121) divides the two orthogonal digital signals into n frequency channel signals respectively, and performs fast Fourier transformation, and the calibration processing module (14) performs fast Fourier transformation on the multi-channel signals Calibration processing of amplitude and phase calculates the upper sideband signal and the lower sideband signal of the output sideband separation respectively. 2. The radio astronomy signal receiving device according to claim 1, characterized in that the calibration processing module (14) in step d reads the calibration coefficients of each frequency channel in the memory module (13) and corresponds to The channel signals are calibrated and calculated to obtain calibrated multi-channel signals. 3. The radio astronomy signal receiving device according to claim 2, characterized in that, the calibration coefficients are pre-injected into the test signals of n frequency channels at the input end of the radio frequency filter (2), and the first multinomial After processing by the filtering module (12) and the second polynomial filtering module (121), the signal complex values of the two orthogonal signals in each frequency channel are obtained, and then the calibration coefficient of each frequency channel is obtained through calculation, and the calibration coefficient is generated. coefficient file.

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