Method and system for testing data signal amplifier having output signal power dependent upon multiple power control parameters

A method and apparatus for testing a data signal amplifier having an output signal power dependent upon multiple signal power control parameters, e.g., signal gain control and amplifier bias current control.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods and systems for testing data signal amplifiers, and in particular, to testing data signal amplifiers capable of multiple output signal power levels for minimizing power consumption.

2. Related Art

The current generation (3G) of cellular telephones offer, among other things, faster connection speeds to the internet. These higher connection speeds are achieved by more complex modulation and stricter requirements for accurate signal power levels. At the same time, since such devices are usually powered by batteries, these devices also need to minimize their power consumption.

Accordingly, to meet these conflicting requirements of high performance while consuming the lowest possible amount of power, these devices use many techniques to minimize power consumption, including minimizing current consumption in the radio frequency (RF) circuitry. Examples include dynamically changing bias current in the output power amplifier such that the bias current scales (e.g., higher or lower) in accordance with the transmitted signal power. Alternatively, or in some instances in addition, the power supply voltage to the output power amplifier can be controlled using a switching DC-DC converter to reduce the power supply voltage when transmitting at lower output signal power levels. While these techniques do help improve battery life, they also make device behavior more difficult to calibrate, since multiple power control parameters are changing as the output transmitted signal power changes. Accordingly, a more complex calibration technique is required.

Such calibration, which is done during performance testing of the device following its manufacture, has either been an iterative process or based on simple assumptions of the behavior of the device under test (DUT). The former technique will provide for more thorough testing and calibration, but at the cost of test speed, while the latter will often provide reasonable test results, but not optimal, since the test results, based on assumptions, may not be sufficiently accurate in view of the strict performance requirements.

Referring toFIG. 1, the output power amplifier10amplifies the outgoing data signal11ato produce the amplified data signal11bto be transmitted. The amplifier10receives its power13bfrom a power source12controlled by a bias signal13a. Accordingly, as discussed above, the power level of the transmitted signal11bcan be controlled, at least, by controlling the level of the input signal11ato the power amplifier10, as well as the DC power13bprovided to the amplifier10by the power source12. As discussed above, this DC power13bcan be controlled by controlling its current or voltage in accordance with the bias control signal13a.

Referring toFIG. 2, as discussed above, the RF output power (i.e., transmitted signal power delivered to the antenna) is a function of the power of the input signal11ato the power amplifier10and the bias setting for the DC power13bprovided to the power amplifier10(FIG. 1). The two curves represent two different bias settings, with the lower curve resulting from a lower bias setting and the higher curve resulting from a higher bias setting. As can be seen, at lower power levels, output power verses input power is approximately linear. However, at higher levels, power variations differ significantly between the two bias settings.

A common test technique is to perform calibration in two or more steps. One step might be varying the power of the outgoing signal11aprovided to the amplifier10, while maintaining fixed power supply voltage and bias current. A second step could be varying the power supply voltage while maintaining fixed input signal power and bias current. A third step can then be varying the bias current while maintaining fixed input signal power and power supply voltage. As a result, amplifier performance has been characterized with respect to two or three control parameters, from which expected performance can be inferred or extrapolated, based on the observed relationships between signal power, power supply voltage and bias current. However, such expected future performance is based on one test parameter with influences based on power supply voltage or bias current assumed to be consistent from one device to another.

While this may yield acceptable results for many devices, with increasingly strict performance requirements, it is unlikely that sufficiently low failure rates during actual operations can be achieved, since the characterized performance does not accurately model actual performance.

For example, maintaining constant bias current while varying the power of the amplifier input signal11a, the operating temperature of the amplifier10may be higher than that to be expected during actual operation, since the bias setting will likely be higher than that used when battery power conservation measures are being followed. While it is possible to model the expected amplifier temperature, there will nonetheless be variations among devices. Further, since the power variances are applied quickly during testing, the internal temperature of the amplifier10may vary during these variances, while the system temperature measured at a different location within the device will not be affected significantly due to the fast testing. Accordingly, the testing operation will not accurately simulate normal operation.

SUMMARY OF THE INVENTION

In accordance with the presently claimed invention, a method and apparatus are provided for testing a data signal amplifier having an output signal power dependent upon multiple signal power control parameters, e.g., signal gain control and amplifier bias current control.

In accordance with one embodiment of the presently claimed invention, a method for testing a data signal amplifier having an output signal power dependent upon a plurality of signal power control parameters includes:

providing a first control signal corresponding to a first control parameter and having a first one of a first plurality of values;

providing a second control signal corresponding to a second control parameter and having a first sequential subset of a second plurality of values;

providing, to an amplifier, a power supply voltage and a bias current with at least one of which having a magnitude related to one of the first and second control signals;

providing, to the amplifier, an input data signal having a plurality of sequential magnitudes related to another of the first and second control signals;

providing, with the amplifier, an output data signal having a plurality of sequential magnitudes related to the one of the first and second control signals and the input data signal; and

measuring each one of the plurality of sequential output data signal magnitudes, followed byproviding the first control signal corresponding to the first control parameter and having a second one of the first plurality of values,providing the second control signal corresponding to the second control parameter and having a second sequential subset of the second plurality of values, andrepeating the providing of the power supply voltage, the bias current, the input data signal and the output data signal, and the measuring of each one of the plurality of sequential output data signal magnitudes.

In accordance with another embodiment of the presently claimed invention, a system for testing a data signal amplifier having an output signal power dependent upon a plurality of signal power control parameters includes:

controller means for controllingas part of a first test sequence, conveyance ofa first control signal corresponding to a first control parameter and having a first one of a first plurality of values,a second control signal corresponding to a second control parameter and having a first sequential subset of a second plurality of values,a power supply voltage and a bias current to an amplifier with at least one of which having a magnitude related to one of the first and second control signals, andan input data signal to the amplifier having a plurality of sequential magnitudes related to another of the first and second control signals, andas part of a second test sequence, conveyance ofthe first control signal corresponding to the first control parameter and having a second one of the first plurality of values,the second control signal corresponding to the second control parameter and having a second sequential subset of the second plurality of values,the power supply voltage and the bias current to the amplifier with said at least one of which having a magnitude related to the one of the first and second control signals, andthe input data signal to the amplifier having a plurality of sequential magnitudes related to the another of the first and second control signals; and

receiver means foras part of the first test sequence,receiving an output data signal from the amplifier and having a plurality of sequential magnitudes related to the one of the first and second control signals and the input data signal, andmeasuring each one of the plurality of sequential output data signal magnitudes, andas part of the second test sequence,receiving the output data signal from the amplifier and having a plurality of sequential magnitudes related to the first control signal and the input data signal, andmeasuring each one of the plurality of sequential output data signal magnitudes.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of example embodiments of the presently claimed invention with references to the accompanying drawings. Such description is intended to be illustrative and not limiting with respect to the scope of the present invention. Such embodiments are described in sufficient detail to enable one of ordinary skill in the art to practice the subject invention, and it will be understood that other embodiments may be practiced with some variations without departing from the spirit or scope of the subject invention.

Throughout the present disclosure, absent a clear indication to the contrary from the context, it will be understood that individual circuit elements as described may be singular or plural in number. For example, the terms “circuit” and “circuitry” may include either a single component or a plurality of components, which are either active and/or passive and are connected or otherwise coupled together (e.g., as one or more integrated circuit chips) to provide the described function. Additionally, the term “signal” may refer to one or more currents, one or more voltages, or a data signal. Within the drawings, like or related elements will have like or related alpha, numeric or alphanumeric designators. Further, while the present invention has been discussed in the context of implementations using discrete electronic circuitry (preferably in the form of one or more integrated circuit chips), the functions of any part of such circuitry may alternatively be implemented using one or more appropriately programmed processors, depending upon the signal frequencies or data rates to be processed.

Referring toFIG. 3, in accordance with one embodiment of the presently claimed invention, a testing apparatus100is coupled as appropriate to a DUT200. In this example, the testing apparatus100includes a computer102, control/interface circuitry104and a RF receiver106. The DUT200includes baseband circuitry202, RF circuitry206(e.g., in the form of an application specific integrated circuit, or ASIC), output power amplifiers210, signal combining or routing circuitry212(e.g., signal summing circuitry or a diplexer), and an antenna214. Also included are digital-to-analog converters (DACs)204,208providing signal conversion between the baseband circuitry202and the RF circuitry206and power amplifiers210(discussed in more detail below).

The baseband circuitry202includes a transmit signal generator to provide the transmit data signal203t, e.g., in the form of quadrature signals203i,203q. Also included is RF power control circuitry to provide voltage gain control (VGC) data for the RF circuitry206. The VGC data are stored in a register202a, with selected data203aconverted by the VGC DAC204to provide an analog control signal205for controlling the power levels of the transmit data signals provided as the input signals207to the power amplifiers210. The baseband circuitry202also includes power amplifier bias control circuitry to provide bias control data. These bias control data are stored in a bias register202b, with the selected bias control data203bconverted by the bias DAC208to provide an analog bias control signal209for the power amplifiers210.

The RF circuitry206typically includes frequency synthesis circuitry, filters and mixers for frequency up-conversion of the transmit data signal203t, and amplifier circuitry controlled by the VGC signal205to provide the transmit data signals207to the power amplifiers210.

The respective transmit data signals207a,207b, . . . ,207nare provided to corresponding respective power amplifiers210a,210b, . . . ,210n, with each signal207and amplifier210operating within a different predetermined frequency range. The resulting amplified signals211are conveyed to the antenna214for transmission215via the signal combiner or router212in accordance with well known principles.

The control/interface circuitry104communicates with the baseband circuitry202and RF circuitry206via one or more control or interface signals105a,105b, e.g., to control access to and selection of the stored VGC202aand bias202bcontrol data during testing. The receiver106receives the transmit signal213during testing. The computer102, via one or more control and data signals103acommunicates with and controls the control/interface circuitry104. The computer102, via one or more additional control and data signals103b, controls the receiver106and accesses transmitter data as received via the output transmit signal213. The receiver106also includes circuitry for measuring power levels of the transmit signal213, with the resulting power level data being made available for analysis by the computer102.

Referring toFIG. 4, in accordance with the presently claimed invention, the control/interface circuitry104, via its control and interface signals105a,105b, causes a transmit data signal203tto be generated, and frequency converted, filtered and amplified to be made available as the input signals207to the power amplifiers210. The power level of each input signal207a,207b, . . . ,207nis established in accordance with the VGC control signal205, while the bias for each power amplifier210a,210b, . . . ,210n(e.g., bias current or power supply voltage) is controlled by the bias control signal209. In accordance with the presently claimed invention, selected subsets of the VGC and bias control data are used during testing. For example, assuming that the VGC control register202aincludes values within the range of 0-255 and the bias control register202bincludes values in the range of 0-127, the bias control may be defined such that a bias setting of 52 corresponds to a power level of −20 dBm, with the range from −20 dBm through 0 dBm being linearly interpolated such that bias control value of 72 corresponds to 0 dBm. Similarly, bias control data values of 82, 97 and 117 can be defined to correspond to power levels of 5, 10 and 15 dBm, respectively (with appropriate linear interpolations of the bias control data within such ranges).

As shown in the Figure, each column includes a “center” value, which is the VGC control register value corresponding to the target power (dBm) for that column, with each register control data value being variable up or down by one or more values of Δ (with Δ being configurable as desired in terms of DAC settings per dB), with lower “i” and higher “j” limits (also configurable as desired). These variables (“center”, Δ, “i”, “j”) will have different values from one column to another.

In accordance with one embodiment of the presently claimed invention, the VGC control data202ais accessed and selected in subsets, or sub-ranges, with each subset of VGC control data being used with one specific bias control level. For example, at a bias control setting of 32, the VGC control data can be swept through a range of values from 10 through 50 in steps of 10, followed by resetting the bias control data to a value of 52 and sweeping the VGC control data from 40 through 80 in steps of 10, followed by resetting the bias control data to 72 and sweeping the VGC control data from 70 through 120, followed by resetting the bias control data to 82 and sweeping the VGC control data from 100 through 170, followed by resetting the bias control data to 97 and sweeping the VGC control data from 140 through 200, followed by resetting the bias control data to 117 and sweeping the VGC control data from 160 through 240.

Based upon the results of such measurements, it will be possible to interpolate the correct point for a given bias level and matching power level. For example, it will be possible to identify the VGC control register202asetting producing −40 dBm of power at a bias control setting of 32, the VGC control register202avalue producing a power of −20 dBm at a bias setting of 52, and so on. Further, as shown inFIG. 4, the VGC control ranges in adjoining target power columns are overlapping, thereby allowing for interpolation between measurements corresponding to the data in the adjoining columns. For example, a VGC control register value of 150 will have three different measured powers for three different bias settings (82, 97, 117), thereby enabling interpolation of how different bias settings affect the transmitted power. As a result, a two-dimensional mesh structure of test data can be created, thereby allowing calibration values to be extrapolated to provide a more accurate representation of DUT performance.

As will be readily understood by one of ordinary skill in the art, it may be necessary to insert “dummy” data packets into the outgoing data signals207to ensure that the power amplifiers210operate for a sufficiently long time interval to reach the correct operating temperature for each bias and VGC control data setting before measurements are performed. As will be readily appreciated, this can be achieved by sending multiple such “dummy” data packets at the particular bias and VGC control data setting before the sequence of test data is transmitted.

In accordance with the presently claimed invention, it is possible to extend this testing technique to provide two variable control parameters affecting the resulting signal transmit power. Preferably, the testing would be defined to have two parameters varying while a third parameter is maintained at a constant predetermined value.