Abstract: Method and apparatus for displaying measures of distortion present at the outputs of a quadrature demodulator. From each of the in-phase and quadrature channels of the demodulator there are acquired n parallel bits, m of these bits being the demodulator data output of the associated channel and (n-m) bits being error bits for the channel. The n bits for each channel are converted to a signal acceptable to a plot display device and applied to orthogonal axes of the device. In addition, an absolute value of the (n-m) error bits for each channel is derived. This absolute value is filtered and displayed, as by a meter, for each channel.

Abstract: A quadrature amplitude modulation (QAM) demodulator system has in-phase and quadrature channel detectors receiving local oscillator signals which must be in precise phase quadrature relationship with each other. The in-phase and quadrature channels each have analog-to-digital converters with n output bits, where n is greater than m, the number of bits required for the data output for each channel. The n-m less significant bits in one channel are used to derive a signal indicating the deviation from a true quadrature relationship between the local oscillator signals. The error signal controls an adjustment of the phase of one of the local oscillator signals, to bring about the precise quadrature relationship required for accurate demodulation.

Abstract: A quadrature amplitude modulation (QAM) demodulator system derives a local oscillator signal which has the frequency and phase of the suppressed carrier of the QAM signal, so as to permit proper demodulation. In-phase and quadrature channels of the demodulator system each have an analog-to-digital converter with n output bits, where n is greater than m, the number of bits required for the data output for each channel. The n-m less significant bits are used to derive a signal indicating the error in phase alignment between the local oscillator signal and the QAM signal. In a phase locked loop, this error signal drives a voltage-controlled oscillator to phase lock with the suppressed carrier of the QAM signal. To acquire frequency and phase lock, a digital-to-analog converter in the loop is clocked each time the phase alignment of the VCO signal and QAM signal is close.

Abstract: A transition for coupling coplanar transmission means to slotline transmission means wherein the balanced slotline can efficiently be coupled to unbalanced signal supplying means such as coax cable. The transition comprises a terminating means for reacting or interacting with the end of a slotline. This interaction between the end of a coplanar signal transmission means and the slotline means allows transmission of signals in either direction between the slotline and the coplanar sections.