Analog-digital hybrid radio frequency receiver group time delay test platform and method

Abstract

The application discloses a kind of mixed radio frequency receiver group time delay test platform and method, including first, second vector signal source, first, second power divider, excitation signal generator, combiner, mixed radio frequency receiver of analog-digital, digital switching board, logic analyzer;First vector signal source simultaneously provides for second vector signal source and mixed radio frequency receiver reference clock, and second vector signal source generates OFDM modulated signal, and excitation signal is sent to logic analyzer by one end of second power divider, and triggers logic analyzer to prepare to accept test signal, and excitation signal is sent to second vector signal source by the other end of second power divider, and is superimposed to radio frequency receiver by combiner with OFDM modulated signal, and is accessed to logic analyzer by digital switching board.It is demodulated I / Q data information of test signal after logic analyzer receives excitation signal again, and calculates group time delay result.The application solves the problem of accurate measurement of group time delay of mixed radio frequency receiver of analog-digital.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of testing, in particular to a platform and method for testing group delay of a mixed analog-digital radio frequency receiver. BACKGROUND

[0002] Radio frequency technology has a wide and irreplaceable role in the field of wireless communication. In all wireless radio frequency receivers, the signal needs to be transmitted without distortion, which requires the system to have good group delay characteristics. Group delay is a transmission characteristic parameter inherent in linear systems and networks, which is defined as the overall time delay of a signal through a linear system or network. The fluctuation of group delay within a certain signal bandwidth at a fixed frequency reflects the stability of the radio frequency receiver under test. With the widespread application and development of navigation positioning, space measurement and control, modern communication and other technologies, electronic systems are evolving towards digitization, and radio frequency receivers are becoming integrated and miniaturized. This kind of radio frequency receiver integrates analog and digital together, becoming a mixed analog-digital radio frequency receiver. For mixed analog-digital radio frequency receivers, the group delay index is as important as that of pure analog radio frequency receivers.

[0003] For radio frequency receiver group delay measurement, the effective methods that can be used at home and abroad are mainly static testing based on vector network analyzer and dynamic testing based on carrier modulation. The static testing method of vector network analyzer uses relative measurement method for measurement, which requires an effective measurement method to accurately describe the phase reciprocity of frequency conversion devices during calibration. So far, there is no recognized effective measurement method at home and abroad, so this method is very difficult. The group delay measurement based on carrier modulation is suitable for frequency conversion receivers that cannot access internal local oscillators, and is the only choice for measurement. In addition, there is a method that uses measurement time interval instead of phase measurement, which has lower measurement accuracy than the conventional modulation method. The above group delay tests are all for pure analog radio frequency receiver systems, and for mixed analog-digital radio frequency receivers, how to directly implement group delay testing is still a problem to be solved.

[0004] Therefore, how to provide a new group delay test platform and method for mixed analog-digital radio frequency receivers is a problem that needs to be solved by those skilled in the art at present. SUMMARY

[0005] The technical problem solved by the present application is to overcome the shortcomings of the prior art and provide a platform and method for testing group delay of a mixed analog-digital radio frequency receiver, which solves the problem of directly obtaining the group delay characteristic curve of a mixed analog-digital radio frequency receiver.

[0006] The technical solution of the present application is: an analog-digital hybrid radio frequency receiver group time delay test platform, comprising a first vector signal source, a second vector signal source, a first power divider, a second power divider, an excitation signal generator, a combiner, a digital adapter board, and a logic analyzer.

[0007] The first vector signal source provides the same reference clock to the second vector signal source and the analog-digital hybrid radio frequency receiver through the first power divider, the second vector signal source generates an OFDM modulated signal, the center frequency of the OFDM modulated signal is consistent with the center frequency of the analog-digital hybrid radio frequency receiver, and the bandwidth of the OFDM modulated signal is set within the range supported by the radio frequency receiver; the excitation signal generator generates a pulse signal, the output end of the excitation signal generator is connected with the second power divider, the pulse signal is sent to the logic analyzer through one end of the second power divider to trigger the logic analyzer to prepare to receive a test signal, the pulse signal is input to the second vector signal source through the other end of the second power divider, the pulse signal is converted from a digital signal to an analog signal output after passing through the second vector signal source, the output of the second vector signal source is connected with the combiner, the combiner superimposes the OFDM modulated signal and the pulse signal to obtain a test signal A; the test signal A is input to the analog-digital hybrid radio frequency receiver through a connecting line and is led out by the digital adapter board to output a test signal B, the digital adapter board inputs the test signal B to the logic analyzer, the logic analyzer is triggered by the test signal B, demodulates the I / Q path data of the test signal B, and calculates the phase and frequency information at different frequencies within a fixed bandwidth to directly display the group delay curve corresponding to each frequency within the fixed bandwidth of the test signal B under the input center frequency of the analog-digital hybrid radio frequency receiver.

[0008] Further, the reference clock provided by the first vector signal source in the present application is a sine wave within the range of 10-80 MHz, and is usually 40 MHz.

[0009] Further, the test signal A is a signal synthesized by time domain superposition of the pulse signal and the OFDM modulated signal through the combiner, and the test signal A is an analog signal; the test signal B is a signal with 0 MHz as the center frequency and the same bandwidth as the test bandwidth of the OFDM modulated signal, and the test signal B is a digital signal, and the phase is changed compared with the test signal A.

[0010] Further, the pulse signal generated by the excitation signal generator in the present application is a positive pulse signal, and the rising edge triggers the logic analyzer.

[0011] Further, the digital adapter board in the present application is a circuit board for transmitting the test signal B to the logic analyzer through the connecting line to realize the digital signal adapter function.

[0012] Further, the digital adapter board and the radio frequency receiver are connected through a wire, and the digital adapter board and the logic analyzer are connected through a Dupont wire.

[0013] Further, the logic analyzer needs to be set as follows: the clock and the pod voltage are selected as LVCMOS 3.3V, and the sampling clock is set as greater than or equal to 2 times the bandwidth of the measured signal.

[0014] Further, the logic analyzer needs to be installed with VSA vector signal analysis software, and the VSA vector signal analysis software is used to directly solve the phase and frequency information at different frequencies in the fixed bandwidth of the test signal B and the group delay test curve.

[0015] The method for measuring the group delay of the analog-digital hybrid radio frequency receiver by using the analog-digital hybrid radio frequency receiver group delay test platform comprises the following steps:

[0016] The first vector signal provides the same reference clock for the second vector signal source and the analog-digital hybrid radio frequency receiver;

[0017] The second vector signal source generates an OFDM modulated signal, and the signal generator generates a pulse signal, which is sent to the logic analyzer and the second vector signal source, respectively; the output of the second vector signal source is connected to the combiner, and the combiner superimposes the OFDM modulated signal and the pulse signal to obtain the test signal A;

[0018] The logic analyzer is triggered after receiving the pulse signal, and starts to prepare to receive the test signal B; the test signal A is input to the analog-digital hybrid radio frequency receiver through the connecting wire;

[0019] The test signal A is converted into the test signal B through the analog-to-digital ADC link in the radio frequency receiver, and the test signal B is transferred to the logic analyzer through the digital adapter board;

[0020] When the logic analyzer receives the test signal B, the I / Q data of the test signal B is demodulated, and the group delay characteristic curve of the test signal B at each signal frequency in the set bandwidth is directly obtained through the VSA vector signal analysis software.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] 1. The present application breaks through the traditional network analyzer test method for measuring the group delay of an analog radio frequency receiver, and adopts the combination of a logic analyzer and vector signal analysis software to test the group delay system index of a complete radio frequency-to-digital link through a digital test scheme.

[0023] 2. This invention can test the group delay fluctuation curve of modulated signals under different carrier frequencies and bandwidths, i.e., the group delay fluctuation situation; from a testing perspective, it is convenient and easy to operate, and can meet the testing needs of all communication and radar radio frequency receivers.

[0024] 3. Since the excitation signal is used as the trigger signal, the group delay information is calculated based on the phase of the OFDM signal at each frequency after the excitation signal is triggered. Therefore, the group delay characteristics of other devices in the system, except for the RF receiver, do not affect the test accuracy. It has the advantages of high test accuracy and no need to consider external errors of the system under test. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the analog-to-digital hybrid RF receiver group delay test platform of the present invention.

[0026] Figure 2 This is a schematic diagram of signal demodulation in a logic analyzer in an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram illustrating the group delay calculation principle in an embodiment of the present invention. Detailed Implementation

[0028] like Figure 1 As shown, to address the limitation of existing testing methods and instruments in directly testing the delay of mixed-signal RF receiver groups, this invention provides a mixed-signal RF receiver group delay testing platform, including a first vector signal source, a second vector signal source, a first power divider, a second power divider, an excitation signal generator, a combiner, a digital adapter board, and a logic analyzer. In this embodiment, the two power dividers are of the same model. The first vector signal source provides the same reference clock to both the second vector signal source and the mixed-signal RF receiver through the first power divider, ensuring that the reference clocks of the second vector signal source and the mixed-signal RF receiver are from the same source and avoiding clock errors. In this embodiment, the reference clock is a 40MHz sine wave. The second vector signal source generates an OFDM modulated signal, the center frequency of which is consistent with the center frequency of the RF receiver. The bandwidth of the OFDM modulated signal is set according to the bandwidth to be tested, and the test bandwidth must be within the bandwidth range supported by the RF receiver.

[0029] The excitation signal generator generates an excitation signal, and the excitation signal generated in the embodiment is a positive pulse signal. The excitation signal generated by the pulse signal generator is sent to the logic analyzer through one end of the second power divider, so as to trigger the logic analyzer to prepare to receive the test signal; the pulse signal is input to the second vector signal source through the other end of the second power divider, and after the pulse signal passes through the second vector signal source, the signal form is converted from a digital signal to an analog signal. The output signal of the second vector signal source includes an OFDM modulated signal and a pulse signal, and the output of the second vector signal source is connected to the combiner. The combiner superimposes the OFDM modulated signal and the pulse signal to obtain a test signal A, and the test signal A is an analog signal. The carrier frequency of the test signal A is WMHz, and the bandwidth is BMHz. The test signal A is output from the combiner to the analog-digital hybrid radio frequency receiver through the connecting line, and after the test signal A passes through the ADC link integrated in the radio frequency receiver for analog-digital conversion, a test signal B is obtained, and the test signal B is a digital signal. Compared with the test signal A, the phase is changed.

[0030] Since the digital signal part of the analog-digital hybrid radio frequency receiver cannot be directly led out, in order to make the logic analyzer receive the test signal B, the digital adapter board is used as a bridge for digital signal switching in the embodiment. The digital adapter board is connected with the radio frequency receiver through the flat cable, and the pins of the digital adapter board and the logic analyzer are connected through the Dupont wire.

[0031] The logic analyzer is installed with the VSA vector signal analysis software. In the embodiment, before the experiment, the settings of the logic analyzer are as follows: the clock and the pod voltage are both selected as LVCMOS 3.3V, and the sampling clock is set as 61.44 MHz.

[0032] The method for measuring the group delay by using the application includes the following steps:

[0033] The first vector signal source provides the same reference clock to the second vector signal source and the analog-digital hybrid radio frequency receiver through the first power divider;

[0034] The second vector signal source generates an OFDM modulated signal, the excitation signal generator generates a pulse signal, the pulse signal is sent to the logic analyzer through one end of the second power divider, the pulse signal is sent to the second vector signal source through the other end of the second power divider, and the output of the second vector signal source is connected to the combiner. The combiner superimposes the OFDM modulated signal and the pulse signal to obtain a test signal A.

[0035] The logic analyzer is triggered after receiving the pulse signal generated by the excitation signal generator, and starts to prepare to receive the test signal B; the test signal A is input to the analog-digital hybrid radio frequency receiver through the connecting line.

[0036] Test signal A is converted into test signal B by the ADC link in the radio frequency receiver, and test signal B is transferred to the logic analyzer by the digital adapter board.

[0037] When the logic analyzer receives test signal B, it starts to demodulate the I / Q channel data of test signal B, and directly obtains the group delay characteristic curve of test signal B at each signal frequency within the set bandwidth by the VSA vector signal analysis software.

[0038] Figure 2 The signal demodulation schematic diagram for the logic analyzer can receive and process digital signals. In this embodiment, the local oscillator of the analog-digital hybrid radio frequency receiver is W, the value range of W is 70MHz-6GHz, the center frequency of the analog-digital hybrid radio frequency receiver is 2400MHz, and the bandwidth of the OFDM modulated signal is set to 20MHz according to the test requirement. After test signal A passes through the analog-to-digital ADC link of the radio frequency receiver, test signal B is obtained, test signal B is a wideband signal with 0MHz as the center frequency and 20MHz as the bandwidth after frequency mixing and down-conversion, and test signal B is the wideband signal with group delay and excitation information that the logic analyzer needs to analyze; test signal B is transferred to the logic analyzer by the digital adapter board.

[0039] After the logic analyzer receives the trigger of the excitation information in test signal B, the I / Q channel data of test signal B is demodulated. At this time, the signal frequency obtained is:

[0040] w1=I1+j*Q1

[0041] w2=I2+j*Q2

[0042] …

[0043] w N =I N +j*Q N

[0044] In the above formula, w1, …, w N are complex representations of each signal frequency, I1, …, I N are 1-N channel data of the I channel, Q1, …, Q N are 1-N channel data of the Q channel.

[0045] Then, the phase of the above different frequency signals is obtained by the VSA vector signal analysis software as follows:

[0046] Frequency 1 phase:

[0047] Frequency 2 phase:

[0048] …

[0049] Frequency N phase:

[0050] Figure 3 The group delay calculation principle diagram is shown. In the VSA vector signal analysis software, the group delay characteristic principle of the signal frequency at w1 is calculated as follows:

[0051]

[0052] In the above formula, τ e is the group delay characteristic parameter, and alpha is the frequency change; through the calculation of the above formula, the group delay information of the signal frequency at w1 can be obtained. N w2,..., w n are substituted into the above formula in turn, the group delay information of the analog-digital mixed radio frequency receiver system at different frequencies when the modulation signal bandwidth is 20MHz under the fixed receiving local oscillator frequency is obtained. According to the obtained group delay parameters at each frequency, the group delay fluctuation curve is drawn, and the group delay fluctuation condition can be obtained. Using the VSA vector signal analysis software, the group delay characteristic curve of the test signal B at each signal frequency in the set bandwidth can be directly displayed.

[0053] In the test, when setting the parameters of the analog-digital mixed radio frequency receiver, attention should be paid to the following: the group delay will change with the change of the digital filter bandwidth of the radio frequency receiver, so under the condition that the receiving channel characteristics do not change, if the analog and digital filter bandwidths do not change, the group delay of the radio frequency receiver receiving channel also does not change, that is, it has nothing to do with the bandwidth of the signal transmitted.

[0054] The contents not described in detail in the specification of the present application are the known technologies of those skilled in the art.

[0055] The described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

Claims

1. An analog-digital hybrid group delay test platform for radio frequency receivers, characterized by: The first vector signal source, the second vector signal source, the first power divider, the second power divider, the excitation signal generator, the combiner, the digital adapter board and the logic analyzer; The first vector signal source provides the same reference clock for the second vector signal source and the analog-digital mixed radio frequency receiver through the first power divider, the second vector signal source generates an OFDM modulated signal, the center frequency of the OFDM modulated signal is consistent with the center frequency of the analog-digital mixed radio frequency receiver, and the bandwidth of the OFDM modulated signal is set within the range supported by the radio frequency receiver; the excitation signal generator generates a pulse signal, the output end of the excitation signal generator is connected with the second power divider, the pulse signal is sent to the logic analyzer through one end of the second power divider to trigger the logic analyzer to prepare to receive a test signal, the pulse signal is input to the second vector signal source through the other end of the second power divider, the pulse signal is converted from a digital signal to an analog signal by the second vector signal source, the output of the second vector signal source is connected with the combiner, the combiner superimposes the OFDM modulated signal and the pulse signal to obtain a test signal A; the test signal A is input to the analog-digital mixed radio frequency receiver through a connecting line and is led out by the digital adapter board to output a test signal B, the digital adapter board inputs the test signal B to the logic analyzer, the logic analyzer is triggered by the test signal B, demodulates the I / Q data of the test signal B, and calculates the phase and frequency information at different frequencies within a fixed bandwidth to directly display the group delay curve corresponding to each frequency within the fixed bandwidth of the test signal B at the center frequency of the input band of the analog-digital mixed radio frequency receiver.

2. The platform for group delay testing of a mixed analog-digital radio frequency receiver according to claim 1, characterized in that: The reference clock provided by the first vector signal source is a sine wave within the range of 10-80 MHz.

3. The platform for testing group delay of a mixed-signal radio frequency receiver of claim 1, wherein: The test signal A is a signal synthesized by time domain superposition of the pulse signal and the OFDM modulated signal through the combiner, the test signal A is an analog signal; the test signal B is a signal with the center frequency of 0 MHz and the same bandwidth as the test bandwidth of the OFDM modulated signal after frequency mixing and down-conversion, the test signal B is a digital signal.

4. The platform for testing group delay of a mixed-signal radio frequency receiver of claim 1, wherein: The pulse signal generated by the excitation signal generator is a positive pulse signal, and the rising edge triggers the logic analyzer.

5. The mixed-signal group delay test platform for radio frequency receivers of claim 1, wherein: The digital adapter board is a circuit board for transmitting the test signal B to the logic analyzer through a connecting line to realize the function of digital signal switching.

6. The mixed-signal group delay test platform of claim 5, wherein: The digital adapter board is connected with the analog-digital mixed radio frequency receiver through an FMC interface, and is connected with the logic analyzer through a special adapter line for the logic analyzer.

7. The mixed-signal group delay test platform of claim 1, wherein: The settings required by the logic analyzer are as follows: the clock and the pod voltage are selected as LVCMOS 3.3V, and the sampling clock is set to be greater than or equal to 2 times the bandwidth of the measured signal.

8. The mixed-signal group delay test platform of claim 1, wherein: The logic analyzer needs to be installed with VSA vector signal analysis software, and the VSA vector signal analysis software is used to directly calculate the phase and frequency information at different frequencies within the fixed bandwidth of the test signal B and the group delay test curve.

9. A method of group delay measurement of a mixed-signal radio frequency receiver based on the test platform of claim 1, characterized in that The first vector signal simultaneously provides the same reference clock for the second vector signal source and the analog-digital mixed radio frequency receiver. ​ The second vector signal source generates an OFDM modulated signal, and the signal generator generates a pulse signal, which is respectively sent to the logic analyzer and the second vector signal source, and the output of the second vector signal source is connected to the combiner, and the combiner superimposes the OFDM modulated signal and the pulse signal to obtain a test signal A; The logic analyzer is triggered after receiving the pulse signal, and starts to prepare to receive a test signal B; the test signal A is input to the mixed radio frequency receiver through a connecting line; The test signal A is converted into the test signal B through the analog-to-digital ADC link in the radio frequency receiver, and the test signal B is switched to the logic analyzer through the digital switching board; When the logic analyzer receives the test signal B, the I / Q data of the test signal B is demodulated, and the group delay characteristic curve of the test signal B at each signal frequency within the set bandwidth is directly obtained through the VSA vector signal analysis software.

Images