Abstract: A method for correcting the phase and amplitude imbalance of a quadrature modulated RF signal requires that errors be induced in both amplitude, &rgr;, and in phase &phgr; in at least three different combinations in order to determine the appropriate correction value for amplitude and phase offsets &Dgr; and &thgr;e. According to a first embodiment the same &rgr; and &phgr; offsets applied in three different combinations to determine the necessary &Dgr; and &thgr;e corrections. According to a second embodiment, a fourth measurement is made in order to determine an unknown control scale factor for balance adjustments.

Abstract: The DC offset error of a quadrature modulated RF signal is corrected by introducing a specific trial offset correction value, D, into the DC offset correction circuits 3, 4 or 5 times, by measuring the carrier power resulting from each trial introduction, and by using the information to determine the DC offset correction components, Icor and Qcor. According to an ideal case first embodiment, specific offset D is employed in three different measurement combinations to determine the correction factors Icor and Qcor. According to an alternative embodiment, a fourth offset correction measurement, needed to estimate a single offset control scale factor, is used to account for an unknown power scale factor A. According to a second alternative embodiment, five offset correction measurements are used to account for separate offset control scale factors for the I and Q channels.

Abstract: An RF device (12), such as an amplifier, is tested by applying a digitally-modulated RF stimulus signal, having a known magnitude and phase angle, to the device to cause it to generate a response signal. The response signal of the device is down-converted and digitized prior to establishing its magnitude and phase angle. The magnitude and phase angle of the digitized, down-converted response signal are compared to the magnitude and phase angle, respectively, of the digitally-modulated stimulus signal to yield transfer functions indicative of the operation of the device.

Abstract: A method is provided for accomplishing unified testing of a digital/RF system (10'), comprised of a digital controller (14), a base-band processor (20), an RF transmitter (24) and an RF receiver (34). The digital portion of the digital/RF system (10'), including the digital controller (14) and the base-band processor (20), is tested by a digital test technique such as Boundary-Scan testing. Test patterns for the RF elements are down-loaded from the digital controller (14) to the base-band processor via a Boundary-Scan Test Access Port (TAP). Thereafter, the RF transmitter (24) and the RF receiver (34) are tested by applying the test patterns from the base-band processor to the RF transmitter for transmission thereby. The signal produced by the RF transmitter (24) in response to the applied test pattern is converted to a first digital signal stream for processing by the base-band processor (20) to determine the operability of the transmitter.

Abstract: An integrated circuit (11) is tested at a high microwave frequency through the use of a laser beam (19) having a repetition rate much lower than the test frequency. Electric fields of the test signal extend into an electro-optic material (12) that modulates part of the laser beam. Another part of the laser beam is converted to an electrical pulsed signal that is applied to a microwave mixer (33) along with part of the test frequency signal. A harmonic of the pulsed signal mixes with the test frequency to yield a difference frequency that can be used as a phase reference for analyzing the phase of the test signal. The component pulses (30) of the laser beam have a pulse width which is much shorter than the separation of the pulses, which make it inherently rich in higher harmonics of the fundamental pulse repetition rate.

Abstract: An integrated circuit device (11) is tested by directing a laser beam (19) onto an electrochromic member (17) in close proximity to a conductor (13) of the integrated circuit. Reflected laser light is directed to a detector (21) which converts it to an electrical signal for display by a lock-in amplifier (25). The display characterizes the voltage on the conductor (17) and thereby permits diagnosis of the operation of the integrated circuit (11).

Abstract: Amplitude noise is dramatically reduced in an optically pumped modelocked laser arrangement by incorporating an intra-cavity or external cavity mode selection element with a continuous-wave pump laser coupled optically to a modelocked laser. The mode selection element causes a light beam generated from the pump laser to operate nominally at a single frequency, that is, substantially a single longitudinal mode. Mode selection may be realized with an air-spaced or solid material Fabry-Perot etalon.