Abstract:
An analog to digital signal converting amplifier with automatic gain control. Input analog signal levels are converted to digital form after passing through a variable gain amplifier device. The digital signals are reconverted to analog form and compared to the input analog levels to produce an error signal which is averaged and used to control the gain of the amplifier device. The analog to digital converted produces a maximum output data indication even through the input level may be excessive. A nonzero difference signal is generated even if the digital output is zero.
Abstract:
A data signal communication system including an analog signal transmitter and a receiver for converting the analog signal levels to digital form. The receiver employs an automatic gain control loop including means for generating an error signal related to the difference between the analog input and the analog equivalent of a digital output. The error signal is used to control both loop gain and the quantity of a quadrature component which is combined with the data signal within the automatic gain control loop.
Abstract:
A system for equalizing the phase distortion of a data transmission channel is disclosed wherein the equalizer comprises a fixed delay network and a plurality of selectable delay networks. The fixed delay network exhibits an envelope delay similar to the difference between the characteristic envelope delay for the channel and a desired delay for the channel and the selectable delay networks may be connected therewith in any combination to produce the desired envelope delay. Control means are provided for successively connecting the selectable delay networks to form a successive plurality of test channels. The phase distortion produced by each channel is measured and compared with that produced by each other test channel. The control means includes means for reconnecting the combination of selectable delay networks which produce the smallest value of phase distortion to provide equalization of the channel for data transmission.
Abstract:
Digital or analog data to be transmitted is employed to amplitude modulate a carrier to generate a single-side-band signal which is provided to a receiver over a communication channel. At the receiver a signal having the frequency of the carrier component of the received signal and a constant phase with respect to the carrier component is derived by multiplying the incoming signal by both the output of a local oscillator and the oscillator output phase shifted by 90* and then comparing the two products to derive a feedback signal for adjusting the phase of the local oscillator. The oscillator output and the 90*shifted oscillator signal are each phase shifted by 45* and separately multiplied by the received signal and the output of the 90* multiplication is differentiated and summed with the other product to derive the original transmitted signal. In an alternate embodiment of the invention a double-side-band signal is detected by a pair of product multipliers having inputs which respectively lead and lag the carrier component of the received signal by 45* . The output of the product multiplier which has the 45* leading input is then differentiated and summed in a weighted manner with the output of the other multiplier to derive the original transmitted signal.
Abstract:
An asynchronous data communication system wherein the transmitted signal represents two bit types, it being necessary to segregate the bit types at the receiver. To accomplish the segregation in the proper phase, a selected randomly occurring bit group is combined with a sync signal and converted to a special analog level which uniquely represents the simultaneous selected bit group and sync signal occurrence. The receiver decodes the special analog level back into the bit group and the sync signal and ensures that the bit type segregating unit is in the phase determined to be proper by the original bit type organization established in the transmitter.