System and method for measurement of parameters of radio-frequency transmission devices

A system and method for measurement of parameters of radio-frequency transmission devices is introduced. The system includes a digital signal processing (DSP) unit and RF transmitter and receiver modules. The transmitter generates Gaussian white noise and transmits it to the device under test (DUT) input. The output of the DUT is connected to the receiver. Using DSP analysis on the output response of the DUT to white noise, the DUT transfer function is estimated using iterative LMS method. From the estimated transfer function all the parameters which are used to describe the device can be calculated such as: gain, flatness, phase and group delay, phase and group delay variations, frequency response, filters rejection etc.

FIELD OF THE INVENTION

The present invention relates to systems and method for measuring parameters radio-frequency transmission devices, more particularly, to systems and method for measuring parameters of radio-frequency transmission devices using digital signal processing.

BACKGROUND OF THE INVENTION

In order to use radio-frequency (RF) devices in advanced RF networks (such as third generation (3G) and Long Term Evolution (LTE) cellular networks), the devices must undergo compliance testing to assure that the devices will function correctly within the network and will not introduce interferences into the network.

Such compliance tests are performed by using dedicated test equipment (such as the Agilent VSA and ESG) which is highly complex and incorporates a lot of high-end RF circuitry.

The dedicated test equipment is based on high quality receiver and transmitter components which receive and transmit RF transmissions across the entire scope of the different cellular standards. Therefore, each transmission configuration requires its own RF chain which is unique for this specific configuration and differs from other configurations by frequency ranges, bandwidths, amplitudes etc.

FIG. 1aof the prior art is a schematic block diagram of a transmitting path610′ of a prior art test equipment.

The Tx Data606′ is input to a Tx hardware path block600′ containing several Tx paths each of which is a full hardware RF transmitter of a specific standard such as a Tx CDMA path601′, a Tx WCDMA path602′, a Tx GSM path603′, a Tx GPRS path604′, and a Tx WiFi path605′. The Tx hardware path block600′ outputs the Tx Data606′ through the hardware path selected to be tested to a Tx RF front end607′ which in turn, transmits its output out of the prior art test equipment.

FIG. 1bof the prior art is a schematic block diagram of a receiving path610″ of a prior art test equipment.

In the receiving path610″, a Rx RF front end607″ receives a transmission from outside the prior art test equipment and inputs it to a Rx hardware path block600″ containing several Rx paths each of which is a full hardware RF receiver of a specific standard such as a Rx CDMA path601″, a Rx WCDMA path602″, a Rx GSM path603″, a Rx GPRS path604″, and a Rx WiFi path605″. The Rx hardware path block600″ outputs a Rx data606″ for analysis by the prior art test equipment.

Such dedicated test equipment is very accurate but in many case such accuracy may be excessive and lower accuracy (and much less complex) test equipment can be used.

Using a digital processing software to emulate the different RF transmission signals can help to lower the complexity of the test equipment by eliminating the multitude of RF chains in the dedicated test equipment and thereby simplifying the design of the test equipment.

Using Digital signal processing software any additional transmission configuration (i.e modulation, networking etc.) can be added without the need for multiple hardware RF chains and hardware transceivers.

None of the prior art devices comprises all of the above characteristics and functions.

There is therefore a need for a system and method for measurement of parameters of radio-frequency transmission devices by utilizing a digital signal processing techniques, which comprises a combination of all of the above characteristics and functions.

SUMMARY OF EMBODIMENTS OF THE INVENTION

The background art does not teach or suggest a system and method for measurement of parameters of radio-frequency transmission devices by utilizing a DSP.

The present invention overcomes these deficiencies of the background art by providing a system and method for measurement of parameters of radio-frequency transmission devices where instead of using multiple hardware RF chains and digital radios (one radio for each technology to be tested), a DSP is used to emulate the digital radios and different RF configurations' receive and transmit signals.

According to the teaching of the present invention there is provided a system for measurement of parameters of radio-frequency transmission devices including: a radio-frequency transmission emulator; an input power attenuator, wherein the input power attenuator is operatively connected to the radio-frequency transmission emulator; a device under test, wherein the device under test is operatively connected to the input power attenuator; and an output power attenuator, wherein the output power attenuator is operatively connected to the device under test and to the radio-frequency transmission emulator.

According to the teaching of the present invention the system for measurement of parameters of radio-frequency transmission devices further including: an input relay, wherein the input relay is operatively connected to the input power attenuator and to the device under test; an output relay, wherein the output relay is operatively connected to the device under test and to the radio-frequency transmission emulator; and a bypass connection operatively connected to the input relay and to the output relay.

According to the teaching of the present invention the radio-frequency transmission emulator including: a transfer function estimator; a radio-frequency module transmit, wherein the radio-frequency module transmit is operatively connected to the transfer function estimator; a radio-frequency transmission emulator output port, wherein the radio-frequency transmission emulator output port is operatively connected to the radio-frequency module transmit; a radio-frequency transmission emulator input port; a radio-frequency module receive, wherein the radio-frequency module receive is operatively connected to the radio-frequency transmission emulator input port and to the transfer function estimator; and a main controller, wherein the main controller is operatively connected to the transfer function estimator by a transfer function estimator control line, to the radio-frequency module transmit by a radio-frequency module transmit control line, to the input relay by an input relay control line, to the output relay by an output relay control line, and to the radio-frequency module receive by a radio-frequency module receive control line.

According to the teaching of the present invention the radio-frequency module receive including: a receive radio-frequency switch; a receive gain control, wherein the receive gain control is operatively connected to the receive radio-frequency switch; a receive precision amplifier, wherein the receive precision amplifier is operatively connected to the receive gain control; a receive down converter, wherein the receive down converter is operatively connected to the receive precision amplifier; and a receive controller, wherein the receive controller is operatively connected to the receive radio-frequency switch, to the receive gain control, to the receive precision amplifier, and to the receive down converter.

According to the teaching of the present invention the radio-frequency module transmit including: a transmit up converter; a transmit gain control, wherein the transmit gain control is operatively connected to the transmit up converter; a transmit precision amplifier, wherein the transmit precision amplifier is operatively connected to the transmit gain control; a transmit voltage standing-wave ratio (VSWR) meter, wherein the transmit voltage standing-wave ratio meter is operatively connected to the transmit precision amplifier; a transmit radio-frequency switch wherein the transmit radio-frequency switch is operatively connected to the transmit voltage standing-wave ratio meter; and a transmit controller, wherein the transmit controller is operatively connected to the transmit up converter, to the transmit gain control, to the transmit precision amplifier, to the transmit voltage standing-wave ratio meter, and to the transmit radio-frequency switch.

According to the teaching of the present invention the transfer function estimator including: an analog to digital converter; a digital signals processor, wherein the digital signals processor is operatively connected to the analog to digital converter; and a digital to analog converter, wherein the digital to analog converter is operatively connected to the digital signals processor.

According to the teaching of the present invention there is provided a method for measurement of parameters of radio-frequency transmission devices including the stages of: generating a Gaussian white noise transmission signal in a signal generator; transmitting the Gaussian white noise transmission signal to a device under test; receiving the Gaussian white noise transmission signal after it had passed through the device under test; passing the Gaussian white noise transmission signal through a first filter; passing the received Gaussian white noise transmission signal after it had passed through the device under test through a second filter; subtracting the passed Gaussian white noise transmission signal through a first filter from the received Gaussian white noise transmission signal after it had passed through the device under test through a second filter; feed-backing the subtracted signal to the first filter; communicating between a main controller and the first filter and the second filter; monitoring the signals coming out of the first filter and the second filter; and changing the first filter parameters.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention is of a system and method for measurement of parameters of radio-frequency transmission devices by utilizing a DSP.

The principles and operation of a system and method for measurement of parameters of radio-frequency transmission devices by utilizing a DSP according to the present invention may be better understood with reference to the drawings and the accompanying description.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, dimensions, methods, and examples provided herein are illustrative only and are not intended to be limiting.

The following list is a legend of the numbering of the application illustrations:1measurement system10RF transmission emulator12input power attenuator14input relay16device under test (DUT)18output relay19bypass connection20output power attenuator30RF module Tx control line40RF module Rx control line50input relay control line60output relay control line70transfer function estimator control line80RF transmission emulator input port90RF transmission emulator output port100transfer function estimator102analog to digital converter (ADC)102′ ADC TI ADS5483104digital signals processor (DSP)104′ FPGA Altera Cyclone-III106digital to analog converter (DAC)106′ TI DAC 5682Z106a′ DAC TI channel1106b′ DAC TI channel2108′ voltage controller oscillator (VCXO)110′ clock distributor TI CDCE72010200RF module Tx202Tx up converter204Tx gain control206Tx precision amplifier208Tx voltage standing-wave ratio (VSWR) meter210Tx RF switch212Tx controller300main controller400RF module Rx402Rx RF switch404Rx gain control406Rx precision amplifier408Rx down converter410Rx controller500transfer function estimation algorithm502signal generator504first filter506adder508second filter600′ Tx hardware paths block601′ Tx CDMA path602′ Tx WCDMA path603′ Tx GSM path604′ Tx GPRS path605′ Tx WiFi path606′ Tx data607′ Tx RF front end610′ transmitting path600″ Rx hardware paths block601″ Rx CDMA path602″ Rx WCDMA path603″ Rx GSM path604″ Rx GPRS path605″ Rx WiFi path606″ Rx data607″ Rx RF front end610″ receiving path

Referring now to the drawings,FIG. 2is a schematic block diagram of a measurement system1according to the present invention.

The measurement system1includes a RF transmission emulator10that is operatively connected to an input power attenuator12through a RF transmission emulator output port90. The input power attenuator12is operatively connected to an input relay14and the input relay14is operatively connected to a device under test (DUT)16. The DUT16is operatively connected to an output relay18which is operatively connected to an output power attenuator20. The output power attenuator20is operatively connected to the RF transmission emulator10through a RF transmission emulator input port80.

The transmission emulator10includes a transfer function estimator100which receives its input from a RF module Rx400and transmits its output to a RF module Tx200.

A main controller300(which is included in the RF transmission emulator10) is operatively connected to the RF module Tx200via a RF module Tx control line30, to the RF module Rx400via a RF module Rx control line40, to the transfer function estimator100via a transfer function estimator control line70, to the input relay14via an input relay control line50, and to the output relay18via an output relay control line60.

The input power attenuator12and the output power attenuator20are optional and can be omitted from the measurement system1in cases where the signals transmitted and received by the RF transmission emulator10and the DUT16have similar amplitudes and power levels. Otherwise, the attenuators are used to lower a signal's power to appropriate levels for the receiving device (either the RF transmission emulator10or the DUT16).

The input relay14and output relay18enable the measurement system1to bypass the DUT16using a bypass connection19in order to be able to calibrate itself by transmitting and receiving a signal without the DUT's16influence on the measurement system1itself.

FIG. 3is a schematic block diagram of a RF module Rx400according to the present invention.

The RF module Rx400receives a number of inputs which can vary in frequency ranges, bandwidths etc. (FIG. 3, describes an exemplary embodiment which includes two input signals IN1and IN2but any number of inputs is possible). These inputs are connected to a Rx RF switch402that controls which of the inputs is passed on to a Rx gain control404that can increase or decrease its gain, thereby increasing or decreasing the signal's amplitude and power. The Rx gain control404outputs a signal that is input to a Rx precision amplifier406that sets the signals precise amplitude and power to the desired level for the following components in the signal's flow path. A Rx down converter408then converts the signal from its radio frequency (RF) range to an intermediary frequency (IF) range which is better suited for the following components in the signal's flow path in the transfer function estimator100(not shown in the present figure, shown inFIG. 2).

All of the components in the RF module Rx400are controlled by a Rx controller410which gets its control commands from the main controller300(not shown in the present figure, shown inFIG. 2).

FIG. 4is a schematic block diagram of a RF module Tx200according to the present invention.

The RF module Tx200receives its input from the transfer function estimator100(not shown in the present figure, shown inFIG. 2). The input signal is input to a Tx up converter202in order to convert it from an intermediary frequency (IF) range to the RF range. From the Tx up converter202the signal is input to a Tx gain control204. The Tx gain control204can increase or decrease its gain, thereby increasing or decreasing the signal's amplitude and power. The Tx gain control204outputs a signal that is input to a Tx precision amplifier206that sets the signals precise amplitude and power to the desired level for the following components in the signal's flow path. From the Tx precision amplifier206the signal goes into a Tx voltage standing-wave ratio (VSWR) meter208for validation of its amplitude and power in order to be able to adjust the gain and amplification of the Tx gain control204and precision amplifier206. Following the Tx VSWR meter208is a Tx RF switch210that can switch the incoming signal out to a number of outputs (FIG. 4, describes an exemplary embodiment which includes two output signals OUT1and OUT2however any number of outputs is possible).

All of the components in the RF module Tx200are controlled by a Tx controller212, which gets its control commands from the main controller300(not shown in the present figure, shown inFIG. 2).

FIG. 5is a schematic block diagram of a transfer function estimator100according to the present invention.

The transfer function estimator100receives an input signal from the RF module Rx400(not shown in the present figure, shown inFIG. 2), which by its nature is an analog signal. In order to be able to perform calculations on the received signal, an analog to digital converter (ADC)102is used to convert the incoming analog signal into a digital representation of the analog signal. The digital signal is composed of a number of bits whose quantity is determined by the accuracy needed for the calculations.

A digital signals processor (DSP)104is used to calculate various parameters of the received signal according to commands coming from the main controller300(not shown in the present figure, shown inFIG. 2). The calculations results are sent to the main controller300(not shown in the present figure, shown inFIG. 2) which can decide whether the DUT16(not shown in the present figure, shown inFIG. 2) passed or failed the test.

The DSP104can also be used to stimulate the DUT16by creating various signals that can be input to the DUT16. Such signals are output from the DSP104as a digital signal with a certain number of bits determined by the accuracy needed. The digital signal is input to a digital to analog (DAC)106where it is converted to an analog signal and output to the RF module Tx200(not shown in the present figure, shown inFIG. 2).

FIG. 6is a schematic block diagram of one specific implementation of a transfer function estimator100using existing, commercially available components according to the present invention.

In the present figure, the ADC102is implemented with an ADC TI ADS5483102′ device, the DSP104is implemented with an FPGA Altera Cyclone-III104′ device and the DAC106is implemented with a TI DAC 5682Z106′ device.

Additionally, this implementation requires the use of a voltage controller oscillator (VCXO)108′ and a clock distributor TI CDCE72010110′ to supply the same clock signal to the various components within the transfer function estimator100.

The TI DAC 5682Z106′ contains two DAC channels; the DAC TI channel1106a′ and DAC TI channel2106b′ either of which can be used as the DAC106.

It should be noted that this specific implementation is only one possible implementation of the present invention and is not intended to limit the present invention.

FIG. 7is a schematic block diagram of the RF transmission estimation algorithm500according to the present invention.

The RF transmission estimation algorithm500starts by generating a Gaussian white noise (GWN) transmission signal in a signal generator502which is transmitted via the output port90, input relay14, DUT16, output relay18and received in the input port80. Optionally, the input relay14and output relay18can bypass the DUT16.

The WGN transmission signal goes through a first filter504into an adder506. The signal coming in through the input port80goes through a second filter508into the adder506. The adder506subtracts the two signals and input the resultant signal back to the first filter504.

The main controller300communicates with both the first filter504and the second filter508to control the first filter504parameters and monitor the signals coming out of the two filters. By changing the first filter504parameters, the main controller300can decrease the RMS error between the two signals coming out of the two filters. Once minimal RMS error is achieved, the first filter504parameters represent the DUT's16estimated transfer function.

This algorithm is sometimes known as Least Mean Square (LMS) algorithm. The LMS algorithm can estimate a DUT's16transfer function in its linear sections. For the non-linear sections of the transfer functions, the well known 2-tone IMD level and an input power\output power (Pi\Po) curve algorithm can be used to estimate the DUT's16non linear transfer function.

Once the transfer function is estimated, the main controller300can run off-line simulations using a digital signal processing software (such as MATLAB by MathWorks). The offline simulation software has an Rx part (transmitter) and a Tx part (receiver). It simulates various communication protocols to generate (simulated) analog signals. Then these signals are passed (digitally) through the estimated transfer function to obtain the Rx signals. The Rx signals are analyzed to obtain test results.

Comparing the simulation results with the standards' requirements show whether the DUT is compliant with the standard or not.

It should be noted that using the estimated transfer function estimator100other parameters of the DUT16can be obtained such as: gain, flatness, phase and group delay, phase and group delay variations, frequency response, filters rejection etc.

The signal generator502, first filter504, adder506, and second filter508are normally implemented within the transfer function estimator100(not shown in the present figure, shown inFIG. 2), usually in the DSP104(not shown in the present figure, shown inFIG. 5).

The present figure omits certain components described in previous figures for clarity purposes only and does not intend to omit them from the present invention.

The RF transmission estimation algorithm500is used as a basis of a method for measurement of parameters of radio-frequency transmission devices which includes the following steps:

(i) generating a Gaussian white noise transmission signal in a signal generator;

(ii) transmitting the Gaussian white noise transmission signal to the device under test;

(iii) receiving the Gaussian white noise transmission signal after it had passed through the device under test;

(iv) passing the Gaussian white noise transmission signal through the first filter;

(v) passing the received Gaussian white noise transmission signal after it had passed through the device under test through the second filter;

(vi) subtracting the passed Gaussian white noise transmission signal through the first filter from the received Gaussian white noise transmission signal after it had passed through the device under test through the second filter;

(vii) feed-backing the subtracted signal to the first filter;

(viii) communicating between the main controller and the first filter and the second filter;

(ix) monitoring the signals coming out of the first filter and the second filter; and

(x) changing the first filter parameters.