CN210490902U - Single-port differential test equipment for S parameter - Google Patents
Single-port differential test equipment for S parameter Download PDFInfo
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- CN210490902U CN210490902U CN201922302690.7U CN201922302690U CN210490902U CN 210490902 U CN210490902 U CN 210490902U CN 201922302690 U CN201922302690 U CN 201922302690U CN 210490902 U CN210490902 U CN 210490902U
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Abstract
The utility model discloses a single port differential test device of S parameter, wherein, the single port differential test device of S parameter comprises a single port test instrument; the single-port testing instrument comprises a pair of signal ports, the pair of signal ports are respectively connected with impedance matchers, and the output end of each impedance matcher is connected with a testing port group used for connecting a differential device; the test port group is connected with a switchable compensation circuit. The utility model discloses utilize the impedance matcher to realize low-cost single port difference test, introduce compensating circuit compensation error simultaneously for the test of S parameter can realize large batch production.
Description
Technical Field
The utility model belongs to the measurement field of differential circuit characteristic, concretely relates to single port difference test equipment of S parameter.
Background
Differential circuit structures are increasingly being used because of their excellent gain, second-order linearity, outstanding resistance to stray strains, and noise immunity. To characterize balanced circuit characteristics by direct measurement, it is often necessary to use an expensive four-port vector network analyzer.
An article named 'characterization of differential circuit by using two-port S parameters' is disclosed in IEEE Microwave Magazine, a balun structure is provided in the article, the function of converting a balanced structure into an unbalanced structure can be realized, and a radio frequency engineer realizes measurement of the characteristics of the differential circuit by using a single-port vector network analyzer to match the balun structure.
However, the single-port analyzer with balun structure still has high balun structure cost and larger error, and is difficult to be suitable for the batch production requirement of factories or workshops.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a: aiming at the problems of higher cost and larger error of a single-port vector network analyzer adopting a balun structure in the prior art, the single-port vector network analyzer with another structure is provided, and particularly, the single-port vector network analyzer is single-port differential test equipment of S parameters, and an impedance matcher consisting of resistors is adopted to complete the test of the S parameters of differential signals by using an unbalanced radio frequency port; meanwhile, a compensation circuit is arranged, and forward compensation is introduced during calibration so as to compensate errors during measurement.
In order to realize the purpose, the utility model discloses a technical scheme be:
a single-port differential test device of S parameters comprises a single-port test instrument;
the single-port testing instrument comprises a pair of signal ports, the pair of signal ports are respectively connected with impedance matchers, and the output end of each impedance matcher is connected with a testing port group used for connecting a differential device;
the test port group is connected with a switchable compensation circuit.
Optionally, the compensation circuit is an LC compensation circuit.
Optionally, the test port group includes a pair of through test port groups, an inductance device is connected between anodes and between cathodes of the pair of through test port groups, and a capacitance device is connected between an anode and a cathode of each through test port group.
Optionally, the compensation circuit is a capacitive device.
Optionally, the test port group includes a load test port group, and a load resistor and the capacitor device are connected between a positive electrode and a negative electrode of each load test port group.
Optionally, the test port group includes a pair of through test port groups, the positive electrodes of the pair of through test port groups are connected, and the negative electrodes of the pair of through test port groups are respectively connected, and the capacitor device is connected between the positive electrode and the negative electrode of each through test port group.
Optionally, the impedance matcher is 50 Ω: 100 omega.
Optionally, the impedance matcher includes a first resistor and a second resistor, the first resistor is connected in parallel between a signal line connected to the signal port and a power connection line, and the signal line of the second resistor is connected in series to the signal line.
Since the technical scheme is used, the beneficial effects of the utility model are that:
the utility model discloses a single port differential test equipment of S parameter adopts single port test instrument (being single port vector network analyzer promptly), dispose the impedance matcher at the signal port, make the unbalance of single port still be applicable to the differential test to the device that awaits measuring, the impedance matcher adopts the lower resistance of cost to constitute, compare in the balun structure of prior art, the cost is lower, and the frequency characteristic of resistance reaches 1000MHz very easily, thereby more be fit for the measurement of the popular 5G/10G network device at present, the low batch test that also realizes more easily of cost simultaneously;
and simultaneously, the utility model discloses compensating circuit has been introduced when the calibration to can be before the test, carry out the calibration earlier, introduce certain loss during the calibration, the calibration is accomplished, removes this compensating circuit again when measuring the product, makes the product test result obtain the forward compensation, thereby eliminates measuring error.
Drawings
Fig. 1 is a schematic circuit diagram of the S-parameter single-port differential testing apparatus of the present invention;
fig. 2 is a schematic circuit diagram of the test port set of the present invention.
Reference numerals: 110-single-port test instrument, 120-signal port, 130-impedance matcher, 131-first resistor, 132-second resistor, 140-test port group, 141-direct-connection test port group, 142-open-circuit test port group, 143-short-circuit test port group, 144-load test port group, 201-LC compensation circuit and 202-capacitor device.
Detailed Description
Name interpretation:
s-parameters, i.e. scattering parameters. Is an important parameter in microwave transmission. S12 is the reverse transmission coefficient. S21 is the forward transmission coefficient, i.e., the gain. S11 is the input reflection coefficient, i.e., the input return loss, and S22 is the output reflection coefficient, i.e., the output return loss. The S-parameter describes the frequency domain characteristics of the transmission channel, from which we can see almost all the characteristics of the transmission channel. Most of the issues of signal integrity concern, such as signal reflections, crosstalk, and loss, can be found from the S-parameters to find useful information.
The vector network analyzer is a kind of electromagnetic wave energy testing equipment. The method can measure various parameter amplitudes and phases of a single-port network or a two-port network, and a vector network analyzer can also display test data by using a Smith chart.
Single port testing: when the required frequency range is not higher than 100MHz, the result of the single-port test can also meet the requirements of network users, when the signal frequency in high-frequency network communication reaches the frequency requirements of 100-500 MHz or even higher, because the method is an unbalanced measurement method, the signal is differentially balanced when the signal is used by an actual customer, a loop through which the signal passes after the matcher is added is also longer, errors on a test fixture cannot be completely offset, the error is equivalent to parasitic capacitance, the deviation of the test result is larger, the actual parameter level of a device cannot be reflected, and the requirements of the corresponding network customer cannot be met.
The technical problem to be solved by the application is to realize the test of the S parameter by using a single port so as to achieve the effect of multi-port test.
The technical scheme of the utility model is elaborated in detail by combining the specific implementation mode as follows:
referring to fig. 1, the S-parameter single-port differential test apparatus of this embodiment includes a single-port test instrument 110, where the single-port test instrument 110 is a vector network analyzer with a conventional single-port structure, the vector network analyzer has a pair of signal ports 120, and each of the signal ports 120 has a signal terminal connected to a signal line and a ground terminal connected to a ground line. The signal port 120 is generally a coaxial cable connection terminal, the outer circumference is a ground terminal, the middle is a signal terminal, the coaxial cable is generally used for connecting the signal port 120, the middle is a signal line for connecting the signal terminal, and the outer circumference is a ground line for connecting the ground terminal.
The signal ports 120 of the single-port test instrument 110 are respectively connected with impedance matchers 130, and the output end of each impedance matcher 130 is connected with a test port group 140 for connecting a differential device.
Specifically, the impedance matcher 130 includes a first resistor 131 and a second resistor 132, the first resistor 131 being connected in parallel between a signal line connecting the signal port 120 and a power line, and the second resistor 132 having a signal line connected in series to the signal line. In this embodiment, the first resistor 131 and the second resistor 132 both adopt patch resistors, and the resistance values are both 69.8 Ω, so that the impedance of 50 Ω can reach 100 Ω at the output side of the impedance matcher 130, so as to adapt to the test of the differential network device. The chip resistor is simple in structure and low in cost, so that the cost of the whole testing equipment can be effectively reduced, batch configuration can be realized, and the testing efficiency of the differential network device is improved.
Referring to fig. 2, the test port group 140 includes a through test port group 141, an open test port group 142, a short test port group 143, and a load test port group 144, and in the S parameter test process of the differential network device, it is generally found that errors occur during the through test of the through test port group 141 and during the load test of the load test port group 144, and for the differential network device, there is substantially no measurement error in the open test port group 142 and the short test port group 143, so the present embodiment connects a switchable compensation circuit only for the through test port group 141 and the load test port group 144, the compensation circuit may be an LC compensation circuit 201 or a capacitance device 202, the compensation circuit and the corresponding test port group 140 may be provided with a switch, the test port group 140 and the compensation circuit are closed during calibration, and the test port group 140 and the compensation circuit are cut off during test, the switch can be implemented by using a switch in the prior art, and this embodiment is not described in detail.
Further, for the through test, in the present embodiment, an inductance device is connected between the positive electrodes and the negative electrodes of the pair of through test port groups 141, and a capacitance device is connected between the positive electrodes and the negative electrodes of each through test port group 141. When the single-port testing instrument 110 is used for testing the frequency of 100-500 MHz, the single-port testing has linear reduction of-0.1 to-1.5 dB compared with the S21 of the multi-port differential testing.
TABLE 1 measurement results of existing multi-port differential and single-port measurements
As shown in Table 1, in the existing S21 test, the difference between single-port measurement and multi-port differential measurement is small and meets the requirement only when the frequency is 100MHz, and the difference is large and cannot meet the requirement when the frequency is 300MHz-500 MHz.
In order to compensate such errors, when the single-ended measurement calibrator S21 (direct-through calibrator) is used, a LC compensation circuit 201, which is composed of an inductance device and a capacitance device, is added, so that a certain loss is intentionally introduced, and when the calibrator finishes measuring a product, the compensation circuit is removed, so that a product test result is compensated in a forward direction, as shown in table 2, a test result can almost reach a multi-end differential test result, and a sample sent to a client can also meet a client requirement.
TABLE 2 measurement results of the existing multi-port differential measurement and the single-port measurement of the present application
As shown in table 2, the error of the single-port measurement and the multi-port differential measurement is within an acceptable range by introducing the compensation circuit.
The positive electrodes and the negative electrodes of the through test port groups 141 may be connected with an inductance device, or may be directly and respectively connected without being connected with an inductance device, and a capacitance device is connected between the positive electrode and the negative electrode of each through test port group 141, so that errors can be compensated.
For the load test, a load resistor and a capacitor device 202 are connected between the positive electrode and the negative electrode of each load test port group 144, the capacitor device 202 is introduced as a compensation circuit by using the same principle, so that forward compensation is introduced during calibration, and the compensation circuit is removed after calibration is completed to compensate errors generated during the test.
The utility model discloses a test method of single port difference test equipment, including following step:
calibration: the test port group 140 of the single-port test instrument 110 is connected with a standard device tested by engineering, and is connected with a compensation circuit for calibration; the standard device subjected to engineering test can be a standard device which is measured by a multi-port differential instrument, and the characteristics meet the requirements.
And (3) testing: the test port group 140 of the single-port test instrument 110 is connected to a device to be tested, the compensation circuit is removed, and S parameter test is performed, wherein the device to be tested is a product to be measured.
In the actual production process, after one-time calibration, the single-port test instrument 110 can be used for performing S parameter test on the devices to be tested in batches, and multiple sets of single-port differential test equipment can be configured to realize batch production.
The impedance matcher 130 formed by the chip resistor used in the present embodiment has a lower cost than the balun structure of the prior art. Because the balun structure is not adopted, the test waveform pulse caused by back-and-forth reflection of impedance mismatching and parasitic inductance can not be generated. The frequency characteristic of the chip resistor adopted in the embodiment can easily reach 1000MHz, and the balun structure which can reach 1000MHz at present has the advantages of small supply quantity, high price, long delivery time and inconvenient use, can be generally used in a laboratory, and is difficult to implement during batch testing.
Claims (8)
1. A single-port differential test device of S parameters comprises a single-port test instrument; the method is characterized in that:
the single-port testing instrument comprises a pair of signal ports, the pair of signal ports are respectively connected with impedance matchers, and the output end of each impedance matcher is connected with a testing port group used for connecting a differential device;
the test port group is connected with a switchable compensation circuit.
2. The apparatus for S-parametric single-port differential testing according to claim 1, wherein the compensation circuit is an LC compensation circuit.
3. The S-parameter single-port differential testing device according to claim 2, wherein the testing port groups include a through testing port group, an inductance device is connected between positive electrodes and between negative electrodes of a pair of the through testing port groups, and a capacitance device is connected between positive electrodes and negative electrodes of each through testing port group.
4. The apparatus for S-parametric single port differential test as recited in claim 1, wherein the compensation circuit is a capacitive device.
5. The apparatus according to claim 4, wherein the test port sets comprise load test port sets, and a load resistor and the capacitor device are connected between a positive electrode and a negative electrode of each load test port set.
6. The single-port differential testing device for the S-parameters according to claim 4, wherein the testing port groups comprise through testing port groups, the positive electrodes of a pair of through testing port groups are connected and the negative electrodes of the through testing port groups are communicated, and the capacitor device is connected between the positive electrode and the negative electrode of each through testing port group.
7. The S-parameter single-port differential test device according to claim 1, wherein the impedance matcher is 50 Ω: 100 omega.
8. The apparatus for single-port differential test of S-parameters according to claim 1, wherein the impedance matcher comprises a first resistor and a second resistor, the first resistor is connected in parallel between a signal line connecting the signal ports and a power line, and the signal line of the second resistor is connected in series on the signal line.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110995544A (en) * | 2019-12-19 | 2020-04-10 | 四川经纬达科技集团有限公司 | S parameter single-port differential test equipment and test method thereof |
| CN111624410A (en) * | 2020-06-29 | 2020-09-04 | 普联技术有限公司 | Method and device for acquiring scattering parameter model |
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2019
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110995544A (en) * | 2019-12-19 | 2020-04-10 | 四川经纬达科技集团有限公司 | S parameter single-port differential test equipment and test method thereof |
| CN111624410A (en) * | 2020-06-29 | 2020-09-04 | 普联技术有限公司 | Method and device for acquiring scattering parameter model |
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