A receiver power linearity test apparatus and method

Abstract

The application discloses a kind of receiver power linearity testing device and method, the device includes signal source, single-pole double-throw radio frequency switch S1 and S2, amplifier A1, A2 and A3, power divider, power meter, program-controlled step attenuator T1, T2, T3 and T4 and measured receiver, the signal source is connected single-pole double-throw radio frequency switch S1, the first output of single-pole double-throw radio frequency switch S1 is sequentially connected amplifier A1 and program-controlled step attenuator T1, its second output is sequentially connected amplifier A2 and program-controlled step attenuator T2, program-controlled step attenuator T1, T2 respectively connect the first input and second input of single-pole double-throw radio frequency switch S2, its output end is connected the input of power divider, the first output of power divider is connected power meter, its second output is sequentially connected amplifier A3, program-controlled step attenuator T3, program-controlled step attenuator T4 and measured receiver.The application compared with traditional testing method, test precision is high, test dynamic range is big.

Description

Technical Field

[0001] This invention relates to the field of linearity testing technology, and specifically to a receiver power linearity testing device and method. Background Technology

[0002] The power linearity of a receiver can be defined as the accuracy with which it measures other signal power levels after calibration at a certain signal power level. When calibrated at different power levels, linearity is typically a function of the power entering the receiver. Generally, at lower signal power levels, noise is the main source of error; at higher signal power levels, compression is the main source of error. Furthermore, even within the receiver's primary linear range, the linearity of key components such as mixer and AD chips, as well as the effects of port matching, can influence linearity. For example, a vector network analyzer, a specialized instrument for measuring the S-parameters of microwave devices, is often referred to as the multimeter of microwave instruments, accurately measuring the gain or attenuation of the device under test. After calibration at a certain power level, the power entering the receiver through the device under test (e.g., an amplifier) ​​will be much higher than the power at calibration, while the power entering the receiver through the device under test (e.g., an attenuator) will be much lower. If the linearity of the vector network analyzer receiver is poor in this case, it will cause measurement errors. Although receiver linearity is generally good, maintaining it is still difficult when the measurement range is large, the performance requirements are high, and the bandwidth is wide. This error is usually difficult to calibrate, so measuring the high linearity value of the receiver becomes very important and very difficult.

[0003] If the receiver's linearity requirement isn't particularly high, it can be measured directly using the signal source. This method assumes the signal source's power is absolutely linear and is typically suitable for linearity requirements around 1dB. However, this method's measurement range isn't very wide. Even with some signal sources having very low minimum power, it usually only guarantees 1dB linearity measurements within a range of about 60dB. It's often difficult to measure the 0.1dB compression point, especially when measuring power linearity over a large dynamic range. In such cases, compression may be found before reaching the 0.1dB compression point, or even multiple erroneous compression points. Therefore, this method is not feasible for measuring 0.1dB linearity.

[0004] Another more accurate method is to purchase a high-precision programmable step attenuator with a large bandwidth and wide dynamic range. These attenuators are pre-calibrated by the manufacturer, but they are often expensive and not cost-effective. Even so, the dynamic range of such high-precision attenuators is usually not large enough to meet the testing requirements of receivers with a larger dynamic range. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a receiver power linearity testing device and method, which is rationally designed, overcomes the shortcomings of existing technologies, and has excellent results.

[0006] To achieve the first objective of the invention, the following technical solution is adopted:

[0007] A receiver power linearity testing device includes a signal source, single-pole double-throw (SPDT) RF switches S1 and S2, amplifiers A1, A2 and A3, a power divider, a power meter, programmable step attenuators T1, T2, T3 and T4, and the receiver under test. The signal source is connected to the input terminal of SPDT S1. The first output terminal of SPDT S1 is sequentially connected to amplifier A1 and programmable step attenuator T1, and its second output terminal is sequentially connected to amplifier A2 and programmable step attenuator T2. Programmable step attenuators T1 and T2 are respectively connected to the first and second input terminals of SPDT S2, and their output terminals are connected to the input terminal of the power divider. The first output terminal of the power divider is connected to the power meter, and its second output terminal is sequentially connected to amplifier A3, programmable step attenuator T3, programmable step attenuator T4, and the receiver under test.

[0008] Furthermore, the attenuation range of the programmable step attenuator T4 is determined by the dynamic range of the receiver.

[0009] To achieve objective 2 of the invention, the following technical solution is adopted:

[0010] A receiver power linearity testing method, employing the receiver power linearity testing device described above, includes the following steps:

[0011] S1. Connect the entire test device. Power on the signal source, power meter, receiver, amplifier, and programmable step attenuator for more than 1 hour. The attenuation range of programmable step attenuator T4 is c dBm.

[0012] S2. Set the signal source frequency f, the receiver power off and set to frequency f, the intermediate frequency bandwidth to F Hz, and the number of scan points to h.

[0013] S3. Open the output curve B of the receiver under test and turn on the cursor;

[0014] S4. The signal source is connected to the branch containing A1 and T1 through a single-pole double-throw RF switch S1, and the attenuation value of A4 is set to 0dB.

[0015] S5. Set the signal source output to 0dBm and set the attenuation value of T1 to a dB. At this time, the power meter value is around 0dBm. Record the power meter value as P0.

[0016] S6. Set the attenuation value of T3 to a dB and the attenuation value of T4 to 0 dB. At this time, the value of the receiver curve is b dBm. The 1 dB compression point of the receiver is more than 10 dB higher than the value of b. It is considered that there is no compression at this time. Record the value of the receiver at this time as B0.

[0017] S7. Set the output of the signal source to -1dBm, and keep the attenuation values ​​of attenuators T1 to T4 unchanged. Record the value of the receiver as B1 and the value of the power meter as P1. Calculate the original linearity δ1 = B1 - B0 - (P1 - P0) and record the absolute value of the linearity as |δ1|.

[0018] S8. The signal source output is converted to -10dBm in 1dBm steps, and the receiver value is recorded as B at each step. i The power meter value is P i Calculate the original linearity δ i =B i -B0-(P i -P0), record the linearity |δ i |, where i is an integer between 2 and 10;

[0019] S9. Set the signal source output to 0dBm, and the attenuation value of T4 to -10dB. At this time, the receiver value is close to B. 10 Adjust the output of the signal source so that the receiver value equals B. 10 Record the value S of the signal source at this time. 10 ;

[0020] S10, Set the value of the signal source to (S 10 -1) dBm, record the receiver value at this time in dBm. 11 The power meter value is P 11 Calculate the original linearity δ at this point. 11 =B 11 -B 10 -(P 11 -P 10 Record the linearity by taking the absolute value |δ 11 +δ 10 |;

[0021] S11, The output of the signal source is transformed in 1dBm steps to (S 10 -10)dBm, calculate the original linearity δ for each step. 12 to δ 20 Record the absolute value of linearity |δ 12 +δ 10 |to|δ 20 +δ 10 |;

[0022] S12. Set the signal source output to 0dBm again, reduce the attenuation value of T4 to -20dBm, and adjust the signal source output so that the receiver value is B. 20 Record the value of the signal source at this time as S. 20 The signal source output is converted to (S) in 1dBm steps. 20 -10)dBm, calculate the original linearity δ for each step. 21 to δ 30 Record the absolute value of linearity |δ 21 +δ 10 +δ 20 |to|δ 30 +δ 10 +δ 20 |;

[0023] S13. Repeat this process to calculate the original linearity δ. 30 to δ c / 2 And record the corresponding absolute value of linearity |δ d+e +δ 10 +…+δ d |, d is a multiple of ten greater than 30 and less than c / 2, e is an integer between 1 and 9;

[0024] S14. When the attenuation value of T4 decreases to -(c / 2+10)dB, the signal source connects the branches containing A2 and T2 through the single-pole double-throw RF switch S1, and at the same time adjusts the output of the signal source so that the output of the receiver is equal to B. c / 2 ;

[0025] S15. Repeat this process to calculate the original linearity δ. c / 2+1 to δ c Calculate the linearity and take the absolute value |δ d’+e +δ 10 +…+δ d’ |,d' represents a multiple of ten greater than c / 2 and less than c, recorded in a table.

[0026] The beneficial effects of this invention are:

[0027] This invention employs a testing apparatus consisting of a standard-precision programmable step attenuator, a power meter, and a signal source. It involves multiple measurements in intervals, followed by mathematical summation of the initial linearity values ​​obtained from these measurements to arrive at the true, high-precision receiver power linearity with a large dynamic range. Compared to traditional testing methods, this invention offers higher accuracy and a wider dynamic range, eliminating the need to purchase a dedicated high-precision programmable step attenuator. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a receiver power linearity testing device according to the present invention; Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to specific examples:

[0030] A receiver power linearity testing device, taking a vector network analyzer receiver as an example, tests its power linearity; Figure 1 As shown, the device includes a signal source, single-pole double-throw RF switches S1 and S2, amplifiers A1, A2 and A3, a power divider, a power meter, programmable step attenuators T1, T2, T3 and T4, and a vector network analyzer. The linearity of the vector network analyzer receiver is calibrated to the linearity of the power meter. Because the power meter has high linearity, the linearity test index can reach within 0.1dB. Because the dynamic range of the vector network analyzer is very large, reaching up to 140dB or more, a 140dB programmable step attenuator T4 is required, with a step value of 1dB. If other types of receivers have a smaller dynamic range, programmable step attenuators with smaller attenuation ranges and amplifiers with smaller gains can be used. In this embodiment, the selected amplifiers are 20dB amplifier A1, 80dB amplifier A2, and 20dB amplifier A3, and the programmable step attenuators are 20dB programmable step attenuator T1, 20dB programmable step attenuator T2, 20dB programmable step attenuator T3, and 140dB programmable step attenuator T4.

[0031] Specifically, the signal source is connected to the input terminal of the single-pole double-throw RF switch S1. The first output terminal of the single-pole double-throw RF switch S1 is connected in sequence to a 20dB amplifier A1 and a 20dB programmable step attenuator T1. Its second output terminal is connected in sequence to an 80dB amplifier A2 and a 20dB programmable step attenuator T2. The 20dB programmable step attenuators T1 and T2 are connected to the first and second input terminals of the single-pole double-throw RF switch S2, respectively. Its output terminal is connected to the input terminal of the power divider. The first output terminal of the power divider is connected to a power meter. Its second output terminal is connected in sequence to a 20dB amplifier A3, a 20dB programmable step attenuator T3, a 140dB programmable step attenuator T4, and a vector network analyzer.

[0032] When the test setup is attenuated by 0-70dB with the 140dB attenuator A4, it uses paths A1 and T1. The purpose of combining A1 and T1 is to adjust the input from the signal source to the power meter. When the test setup is attenuated by 71-140dB with the 140dB attenuator, it uses paths A2 and T2. The purpose of combining A3 and T3 is to adjust the input of the receiver under test, in order to find a suitable uncompressed input power as a reference input power.

[0033] The testing method of this testing device includes the following steps:

[0034] S1. Connect the entire test device, and turn on the signal source, power meter, receiver, amplifier and programmable step attenuator for more than 1 hour to warm up.

[0035] S2. Set the signal source frequency f, the vector network analyzer power off, set the frequency f, the intermediate frequency bandwidth to 100Hz, and the number of scan points to 51.

[0036] S3. Open the output curve B of the receiver under test in the vector network analyzer and turn on the cursor;

[0037] S4. The signal source is connected to the branch containing A1 and T1 through a single-pole double-throw RF switch S1, and the attenuation value of A4 is set to 0dB.

[0038] S5. Set the signal source output to 0dBm and the attenuation value of T1 to 14dB. At this time, the power meter value is around 0dBm. Record the power meter value as P0.

[0039] S6. Set the attenuation value of T3 to 14dB and the attenuation value of T4 to 0dB. At this time, the value of the receiver curve is about 6dBm. Since the 1dB compression point of the receiver is more than 10dB higher than this value, it is considered that there is no compression at this time. Record the value of the vector network analyzer receiver at this time as B0.

[0040] S7. Set the output of the signal source to -1dBm, and keep the attenuation values ​​of attenuators T1 to T4 unchanged. Record the value of the vector network analyzer receiver as B1 and the value of the power meter as P1. Calculate the original linearity δ1 = B1 - B0 - (P1 - P0) and record the absolute value of the linearity as |δ1|.

[0041] S8. The signal source output is converted to -10dBm in 1dBm steps, and the receiver value is recorded as B at each step. i The power meter value is P i Calculate the original linearity δ i =B i -B0-(P i -P0), record the linearity |δ i |, where i is an integer from 2 to 10;

[0042] S9. After the signal source output is reduced to -10dB, the power meter output is reduced to approximately -10dBm. If this reduction continues, the linearity of the power meter will be insufficient. Therefore, the signal source output is set to 0dBm, and the attenuation value of T4 is -10dB. At this point, the value of the vector network analyzer receiver is close to B. 10 To continue the test, the output of the signal source was adjusted so that the value of the vector network analyzer receiver was equal to B. 10 Record the value S of the signal source at this time. 10 ;

[0043] S10, Set the output value of the signal source to (S 10 -1) dBm, record the value of the vector network analyzer receiver at this time as B. 11 The power meter value is P 11 Calculate the original linearity δ at this point. 11 =B 11 -B 10 -(P 11 -P 10 Record the linearity by taking the absolute value |δ 11 +δ 10 |;

[0044] S11, The output of the signal source is transformed in 1dBm steps to (S 10 -10)dBm, calculate the original linearity δ for each step. 12 to δ 20 Record the absolute value of linearity |δ 12 +δ 10 |to|δ 20 +δ 10 |;

[0045] S12. Set the signal source output to 0dBm again, reduce the attenuation value of T4 to -20dBm, and adjust the signal source output so that the value of the vector network analyzer receiver is B. 20 Record the value of the signal source at this time as S. 20 The signal source output is converted to (S) in 1dBm steps. 20 -10)dBm, calculate the original linearity δ at each step. 21 to δ 30 Record the absolute value of linearity |δ 21 +δ 10 +δ 20 |to|δ 30 +δ 10 +δ 20 |;

[0046] S13. Repeat this process to calculate the original linearity δ. 30 to δ 70 And record the corresponding absolute value of linearity;

[0047] S14. When the attenuation value of T4 decreases to -80dB, the signal source connects the branches containing A2 and T2 through the single-pole double-throw RF switch S1, and at the same time adjusts the output of the signal source so that the output of the vector network analyzer receiver is equal to B. 70 ;

[0048] S15. Repeat this process to calculate the original linearity δ. 71 to δ140 Calculate the linearity and take the absolute value, then record it in a table.

[0049] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A receiver power linearity testing device, characterized in that, The system includes a signal source, single-pole double-throw (SPDT) RF switches S1 and S2, amplifiers A1, A2 and A3, a power divider, a power meter, programmable step attenuators T1, T2, T3 and A4, and a receiver of the vector network analyzer under test. The signal source is connected to the input terminal of SPDT S1. The first output terminal of SPDT S1 is connected in sequence to amplifier A1 and programmable step attenuator T1, and its second output terminal is connected in sequence to amplifier A2 and programmable step attenuator T2. Programmable step attenuators T1 and T2 are respectively connected to the first and second input terminals of SPDT S2, and their output terminals are connected to the input terminals of the power divider. The first output terminal of the power divider is connected to the power meter, and its second output terminal is connected in sequence to amplifier A3, programmable step attenuator T3, programmable step attenuator A4, and the receiver of the vector network analyzer under test.

2. The receiver power linearity testing device according to claim 1, characterized in that, The attenuation range of the programmable step attenuator A4 is determined by the dynamic range of the receiver.

3. A method for testing the power linearity of a receiver, characterized in that, The receiver power linearity testing apparatus as described in claim 1 or 2 includes the following steps: S1. Connect the entire test device. Power on the signal source, power meter, receiver, amplifier, and programmable step attenuator for more than 1 hour. The attenuation range of programmable step attenuator A4 is c dB. S2. Set the signal source frequency f, the receiver power off and set to frequency f, the intermediate frequency bandwidth to F Hz, and the number of scan points to h. S3. Open the output curve B of the receiver under test and turn on the cursor; S4. The signal source is connected to the branch containing amplifier A1 and programmable step attenuator T1 through single-pole double-throw RF switch S1, and the attenuation value of programmable step attenuator A4 is set to 0dB. S5. Set the signal source output to 0dBm, set the attenuation value of the programmable step attenuator T1 to a dB. At this time, the power meter value is around 0dBm. Record the power meter value as P0. S6. Set the attenuation value of the programmable step attenuator T3 to a dB and the attenuation value of the programmable step attenuator A4 to 0 dB. At this time, the value of the receiver curve is b dBm. If the 1 dB compression point of the receiver is more than 10 dB higher than the value of b, it is considered that there is no compression at this time. Record the value of the receiver at this time as B0. S7. Set the output of the signal source to -1 dBm. The attenuation values ​​of the programmable step attenuators T1, T2, T3 and A4 remain unchanged. Record the value of the receiver as B1 and the value of the power meter as P1. Calculate the original linearity δ1 = B1 - B0 - (P1 - P0) and record the absolute value of the linearity as |δ1|. S8. The signal source output is transformed to -10 dBm in 1 dBm steps, and the receiver value is recorded as B for each step. i The power meter value is P i Calculate the original linearity δ i = B i - B0-(P i - P0), record the linearity |δ i |, where i is an integer between 2 and 10; S9. Set the signal source output to 0dBm, and the attenuation value of the programmable step attenuator A4 to -10dBm. At this time, the receiver value is close to B. 10 Adjust the output of the signal source so that the receiver value equals B. 10 Record the value S of the signal source at this time. 10 ; S10, Set the value of the signal source to (S 10 -1) dBm, record the receiver value at this time (in dB). 11 The power meter value is P 11 Calculate the original linearity δ at this point. 11 = B 11 - B 10 -(P 11 - P 10 ), record the absolute value of linearity |δ 11 +δ 10 |; S11, The output of the signal source is transformed in 1 dBm steps to (S 10 -10) dBm, calculate the original linearity δ for each step. 12 to δ 20 Record the absolute value of linearity |δ 12 +δ 10 |to|δ 20 +δ 10 |; S12. Set the signal source output to 0dBm again, reduce the attenuation value of the programmable step attenuator A4 to -20dBm, and adjust the signal source output so that the receiver value is B. 20 Record the value of the signal source at this time as S. 20 The signal source output is converted to (S) in 1dBm steps. 20 -10) dBm, calculate the original linearity δ for each step. 21 to δ 30 Record the absolute value of linearity |δ 21 +δ 10 +δ 20 |to|δ 30 +δ 10 +δ 20 |; S13. Repeat this process to calculate the original linearity δ. 30 to δ c / 2 And record the corresponding absolute value of linearity |δ d+e +δ 10 +…+δ d | where d is a multiple of ten greater than 30 and less than c / 2, and e is an integer between 1 and 9; S14. When the attenuation value of the programmable step attenuator A4 decreases to -(c / 2+10)dB, the signal source connects the branch containing amplifier A2 and programmable step attenuator T2 through the single-pole double-throw RF switch S1, and simultaneously adjusts the output of the signal source so that the output of the receiver is equal to B. c / 2 ; S15. Repeat this process to calculate the original linearity δ. c / 2+1 to δ c Calculate the linearity and take the absolute value |δ d’+e +δ 10 +…+δ d’ |,d' represents a multiple of ten greater than c / 2 and less than c, recorded in a table.

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