Hewlett-Packard Company

Agilent Technologies, Inc.

Melvin D Humpherys

Matthew Johnson

Richard P Ryan

David L Platt

Kerwin D Kanago

James B Summers

An RF test set having a concurrent measurement architecture is provided. The RF test set is adapted for testing an RF communications device such as a cellular phone according to a set of RF tests. An RF source and an RF receiver are used to communicate with the cellular phone in order to perform the call processing operations to control the cellular phone while performing parametric measurements according to the RF tests. Concurrent measurements allow operation of concurrent measurement processes and call processing operations to take place in the RF test set in order to decrease the time required for each RF test and to increase measurement throughput of the RF test set.

RF test set with concurrent measurement architecture

A wide band (20 MHz to 2 GHz) four way RF power splitter/combiner is fabricated from four lengths of hard line mounted on a printed circuit board. Slots in the board allow for ferrite sleeves, and allow the hard line to be mounted right next to the surface(s) of the board. The pieces of hard line do not cross each other, and do not pass from one side of the board to the other. Two of the pieces are on one side of the board, while the other two are on the other. Within one pair the two pieces of hard line lie essentially along a straight line. Within the other pair the two pieces are offset, parallel and overlap slightly. All four pieces are parallel. Of the four pieces, one pair may be preformed to be two identical parts; the other pair may be also, although one pair may have a longer portion of center conductor extending beyond a 90.degree. bend. All four pieces of hard line are straight (i.e., their outer shields are straight, and are not bent).

Four way RF power splitter/combiner

The effects of differential heating inside the calorimetric bridge are reduced by first heating the bridge externally and controlling the resulting temperature. The bridge is also heated internally by an amount that varies according to the applied power to be measured. This acts to eliminate the principal source of thermal gradients in the first instance. By applying this heat as a common mode input signal to the two terminating loads of the calorimetric bridge the bridge itself does not become unbalanced, and therefore does not attempt to measure that common power. Actual input power to be measured does initially unbalance the bridge, and is still measured as usual. A constant power circuit is response to the indication of measured power and acts to keep the sum of measured power (plus the equal amount of feedback power that balances the bridge) and the common mode power at a constant value corresponding to a full scale measurement. This eliminates internal thermal transients within the bridge that lengthen response time. The feedback signal to balance the calorimetric bridge is produced by an integrator. To allow operation of the integrator output closer to zero for measurement of small applied signals, the applied input to be measured is periodically removed and a suitable slight offset from the true balance condition is introduced into the servo loop. The bridge is then exactly balanced with a separate sample and hold control loop. 'Periodically' can mean once a second, ten times a second, or as is preferred, at the start of each measurement.

Calorimetric RF power meter with dynamic zeroing and constant

An economical, wide range and accurate power measurement technique switches an RF detector between an applied RF IN to be measured and a COMPARISON RF IN, to thus develop a difference signal. The difference signal is filtered, amplified by a logarithmic amplifier, and then converted into a DC error signal by a synchronous detector operating in step with the switching of the RF detector. The DC error signal is applied to an integrator whose output is a loop control signal. Assuming a square law detector, the square of the loop control signal is linearly proportional to the applied RF IN once a servo loop is hulled by making COMPARISON RF IN equal to RF IN. The desired power measurement is performed by digitizing the loop control signal and performing the appropriate arithmetic operations thereon. The loop control signal is also applied to an analog multiplier, where it combines with an internal RF reference signal to produce, at the output of an attenuator following the multiplier, the COMPARISON RF SIGNAL. The entire loop servos to minimize the difference between the applied RF IN and the COMPARISON RF SIGNAL. When RF IN gets small an increase in attenuation allows the multiplier to continue to operate within an optimum dynamic range by reducing the COMPARISON RF SIGNAL to the same general level as RF IN.

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Spokane, WA, United States of America

Melvin D Humpherys