Abstract: A digitally temperature compensated oscillator (TCO) system is provided which is capable of memorizing in an EEPROM-based look-up table, appropriate digital values of a temperature correction for a voltage controlled oscillator (VCO). An on-board temperature sensing mechanism tracks variations in temperature in the TCO and produces an analog voltage value corresponding to the instantaneous temperature. The voltage value of the sensor output is digitized and designated to constitute an address into the EEPROM based look-up table. As the temperature changes, the digitized output of the temperature sensor and hence the address to the EEPROM changes accordingly. The EEPROM also includes a look-up table of digitized channel tuning voltage values for tuning the VCO to at least one frequency for transmitting or receiving at least one channel, for example in the FRS group of channels. One of these digitized values is selected in response to operator selection of a channel.

Abstract: A TVRO receiver for receiving frequency-modulated video signals comprises a tuner including a super-heterodyne circuit having a voltage-controlled oscillator (VCO), means for supplying a cotnrolling input voltage to the VCO, and a mixer for combining incoming 1st intermediate frequency (IF) sigals within a 1st predetermined IF frequency range with the output of the VCO to reduce the frequency of the 1st IF signals to generate 2nd IF signals within a 2nd predetermined IF frequency range, and a filter for selectively rejecting undersired interference signals. The interference filter comprises separate trap means for respectively blocking out interfering signals having selected bottom and top trap frequencies, tuning means for adjusting the bottom and top trap frequencies, means for increasing the quality factor of the trap means, and means for selectively switching the trap means into and out of the receiver based on the presence or absence of signals which interfere with the received signals.

Abstract: A TVRO receiver for the reception of frequency modulated satellite broadcast signals is provided with the capability of efficiently rejecting image frequencies generated as the received signals undergo intermediate frequency translation. A TVRO tuner, which includes a super-heterodyne circuit having a voltage-controlled oscillator (VCO), means for supplying a controlling tuning voltage to the VCO, and a mixer for combining incoming 1st IF signals with the output frequency of the VCO to reduce the frequency of the 1st IF signals to a selected 2nd IF frequency, is provided with a tracking filter which is adapted to pass only the incoming 1st IF signals and effectively reject any image frequencies generated at the received signal frequencies.

Abstract: Circuits such as balanced diode mixers require balanced transformers. For ultrahigh frequency operation, a balanced transformer is formed as part of a printed circuit on a planar substrate of insulating material. The balanced transformer has a center-tapped winding formed by a loop of a strip transmission line having first and second coextensive elongated conductors disposed on the substrate. Preferably the first and second conductors are disposed adjacent each other on respective opposite sides of the substrate. At a first end portion of the strip transmission line, the second conductor is connected to a center tap, and at a second end portion of the strip transmission line, the first conductor is also connected to the center tap. For a balun transformer, the center tap is a ground plane provided by conductive regions disposed on the substrate.

Abstract: A TVRO receiver for receiving frequency-modulated video signals, the receiver comprising a tuner including a superheterodyne circuit having a voltage-controlled oscillator (VCO), means for supplying a controlling input voltage to the VCO, and a mixer for combining incoming 1st IF signals with the output of the VCO to reduce the frequency of the 1st IF signals to a 2nd IF frequency which is sufficiently high to permit the output frequency of the VCO to be above the frequency range of the 1st IF signals, and a linear phase passband filter for passing a single video channel in the 2nd IF output from the mixer, the filter producing an output which is at least about 10 dB down from its peak at both +10 MHz and -10 MHz from the center of the passband of the filter.

Abstract: An FM receiver for the reception of digital data modulated on a Subsidiary Communication Authorization (SCA) subcarrier is provided with automatic tuning capability and a coherent demodulator for minimizing noise, distortion and interference. The FM receiver is tuned automatically to minimize the measured amplitude of noise and distortion at the high frequency end of the spectrum of the FM demodulator output, above the frequencies of the SCA signal. The SCA signal is tuned by a heterodyne circuit including a balanced modulator, a voltage-controlled oscillator (VCO), and a bandpass filter. The VCO is automatically tuned to maximize the measured amplitude of the SCA signal selected by the bandpass filter. For coherent detection of BPSK (Binary-Phase-Shift-Keying), the coherent demodulator is preferably and kind of data-aided Costas loop in which digital logic circuits perform phase shifting, phase detecting, a multiplying functions.

Abstract: A ferrite core antenna for use in the VHF and UHF range has a first coil on the core which is connected to a capacitance selected to resonate with the inductance of the coil at the desired frequency of operation. The ferrite core antenna also has a second coil for providing a signal to the input stage of a radio receiver. In contrast to conventional loopstick antennas for low frequencies, the operation of the ferrite core antenna in the VHF to UHF range is remarkably improved by using an input stage having a relatively high input impedance and using a greater number of turns in the second coil than the first which is tuned instead of the second. Preferably the first coil is centrally disposed and has a single turn in the form of a relatively wide band of conductive metal foil, and the second coil is offset by a certain distance from the first coil and feeds an input signal to the gate of a gallium arsenide field-effect transistor.

Abstract: A TVRO earth station having a satellite seeking system comprising at least one controllable motor for adjusting the position of an antenna for receiving signals from a satellite having multiple transponders transmitting signals at prescribed nominal center frequencies and with different polarizations, control means for energizing the motor to move said antenna along a predetermined satellite-searching path, a receiver for receiving the incoming signals from the antenna and successively tuning to the center frequencies at each of a succession of intervals along the searching path, means responsive to the signals detected by the receiver for producing a signal or value representing the quality of the detected signals at each of the successive intervals along the searching path, and means responsive to the quality-representing signal or value for identifying the locations along the searching path at which the antenna receives signals from a satellite.

Abstract: An improved TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having a tuner producing output signals corresponding to the received signals and having bandwidths which vary from channel to channel is provided with a band pass filtering arrangement receiving the output signals and having a controllably adjustable pass band, a bandwidth detection circuit for receiving the output signals passing through the filtering arrangement and being responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of the filtering arrangement, and a control circuit responsive to the control signal for adjusting the pass band of the filtering arrangement to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the bandwidth deviation of the current output signal exce

Abstract: In a TVRO earth station having an antenna for receiving incoming satellite signals and polarizing means associated with the antenna for adjusting the relative alignment of the antenna orientation and the polarization of the incoming signals, an automatic polarization control system comprising means for producing an electrical control signal for controlling the polarizing means to adjust the relative alignment, means for detecting the noise level in the satellite signals received by the antenna, and means responsive to the detected noise level for adjusting the control signal, and thereby adjusting the polarizing means, to minimize the detected noise level.

Abstract: An improved satellite receiver system is provided which automatically locates audio signals among the various audio subcarriers received by an earth station; manual scanning of transmissions received from different transponders in order to locate audio signals embedded therein is eliminated. The improved receiver system does not require any input data characterizing the frequencies or bandwidth of the incoming audio signals and locates desired audio subcarriers in response to a command signal, without need for any manual intervention after generation of the command signal.

Abstract: A method of reducing terrestrial interference is provided for a TVRO earth station receiver comprising a super-heterodyne circuit including a voltage-controlled oscillator (VCO), a mixer for combining incoming first IF signals with the output of the VCO to reduce the frequency of the first IF signals to a second IF range having a predetermined nominal center frequency, a pass band filter for filtering the second IF signals and having a pass band centered on the nominal second IF center frequency, and a microprocessor for controlling the input voltage to the VCO and for automatically setting the controlling input voltage at prescribed levels in response to a "channel select" command signal, so that the VCO produces an output frequency which centers the received signal for a selected channel on the nominal second IF center frequency.

Abstract: A digitally temperature compensated oscillator (TCO) system is provided which is capable of ascertaining and memorizing in an EEPROM-based look-up table, appropriate digital values of a temperature-compensating tuning voltage to the TCO during calibration. An on-board temperature sensing mechanism tracks variations in temperature in the TCO and produces an analog voltage value corresponding to the instantaneous temperature. The voltage value of the sensor output is digitized and designated to constitute an address into the EEPROM based look-up table. As the temperature changes, the digitized output of the temperature sensor and hence the address to the EEPROM changes accordingly.

Abstract: A TVRO receiver for receiving frequency-modulated video signals, the receiver comprising a tuner including a superheterodyne circuit having a voltage-controlled oscillator (VCO), means for supplying a controlling input voltage to the VCO, and a mixer for combining incoming 1st IF signals with the output of the VCO to reduce the frequency of the 1st IF signals to a 2nd IF frequency which is sufficiently high to permit the output frequency of the VCO to be above the frequency range of the 1st IF signals, and a linear phase passband filter for passing a single video channel in the 2nd IF output from the mixer, the filter producing an output which is at least about 10 dB down from its peak at both +10 MHz and -10 MHz from the center of the passband of the filter.

Abstract: A TVRO receiver utilizes an improved voltage-controlled oscillator (VCO) of the surface mounted type which has a wide bandwidth of operation extending into the microwave frequency range. The VCO comprises a dielectric substrate with a patterned-metal layer on one side and a surface mounted oscillator on the patterned-metal side of the substrate. The oscillator comprises amplifying means which produce an oscillating output by the use of regenerative feedback means including an open-circuit-stub inductance formed in the patterned metal layer, and a tunable resonant circuit coupled to the amplifying means in order to control the frequency of the oscillating output. The resonant circuit includes a short-circuit-stub capacitance formed within the patterned middle layer, at least one variable capacitance diode in series with the short-circuit stub, and means for applying a controllable tuning potential to the resonant circuit.

Abstract: A television receiver includes a tuner, IF amplifier, video and audio processing circuitry and deflection circuits. Two quadrature detectors are driven from the IF amplifier, one tuned to the sound IF carrier frequency and the other tuned to the picture IF carrier frequency. A combining circuit accepts only negative-going error voltages from the first detector and only positive-going error voltages from the second detector to produce an AFC with a response curve defined by the sound IF frequency at one end and the picture IF frequency at the other end. The output of the combining circuit supplies a voltage controllable oscillator in the tuner.

Abstract: A television receiver having a varactor diode tuned VHF tuner is operable with airborne and cable-connected signals. Bandswitch-controlled diodes change the values of inductive reactance in the tuner stages so the varactor diodes can tune to signals in the VHF Lo and Hi bands and CATV Mid and Super bands. Automatic bandswitching circuitry is included to enable reception of VHF channels 2-13 and UHF channels when operating in the air signal mode and VHF channels 2-13 and CATV Mid (A--I) and Super band (J--Z) channels when operating in the cable signal mode.

Abstract: An abrupt junction type varactor diode television tuner includes a source of DC tuning voltage supplying bias to the diodes for tuning the tuner to broadcast television signals. The varactor diode in the RF amplifier stage is connected to the source of tuning voltage through a very large resistance which provides automatic signal overload protection.

Abstract: A television tuning system has a ramp voltage source including an electrical current source and an electrical current sink coupled through selectively operable transmission gates for varying the voltage of a tuning capacitor to control a local oscillator for tuning independent of received signal. The local oscillator signal is mixed with a received signal to produce an intermediate frequency signal which is amplified in an IF amplifier. A frequency detector is coupled to the IF amplifier and produces an error signal dependent upon the frequency difference between a reference frequency and the IF signal. An additional current source and sink are coupled to the tuning capacitor through transmission gates controlled by the error signals. Differences greater than a predetermined amount selectively activate the latter transmission gates to provide substantially constant magnitude tuning voltage corrections irrespective of the amount of the difference.

Abstract: A VHF television tuner system has four tunable circuits each including an abrupt junction varactor diode having a predictable capacitance-tuning voltage characteristic. The VHF frequency spectrum is divided into Lo and Hi bands encompassing television channels 2-6 and 7-13, respectively. A pair of voltage divider networks comprising precisely trimmed resistive material on a ceramic substrate provide tuning voltage terminals corresponding to the VHF television channels. The end terminals of each divider network are coupled to adjustable potentiometers for setting the tuning voltage at each extreme of the voltage divider. A substrate mounted switch accesses the tuning voltage points, supplies bandswitching voltages and provides AFC defeat between channels.