Abstract: A receiver which converts the RF carrier to a very low frequency and incorporates a PLL demodulator which allows the IF to be AC coupled. This PLL demodulator does not include the IF filters. The bandwidth of the PLL demodulator is wide enough to demodulate FM. Also, components of the receiver can be switched to a transmission mode capable of FM or PSK modulation with a simple circuit. Finally, the receiver includes an AM or PSK coherent amplitude detector which is modified into an imageless spectrum analyzer.

Abstract: A radio receiver circuit which suppresses an interfering signal exhibiting an amplitude significantly greater than that of a desired signal and a frequency nearly the same as that of the desired signal is disclosed. A received signal is applied to a gain controlled amplifier and a limiter. The limiter provides a limited signal which reduces amplitude and power of the desired signal relative to the interfering signal. The gain controlled amplifier provides a constant amplitude signal at an amplitude where the interfering signal portion of the constant amplitude signal equals an amplitude of the interfering signal portion of the limited signal. The constant amplitude and limited signals combine through a subtraction operation resulting in a significant attenuation of the interfering signal while causing only a small attenuation of the desired signal. Switching and decision circuitry are provided to selectively utilize the interference suppression.

Abstract: A demodulator for shaped BPSK signals that utilizes switches which have switching control means designed to eliminate unwanted Q channel signal power and unwanted carrier phase error signal power by opening the switches during the phase transition portions of the shaped BPSK signals. The switching control means close the switches during non-transitional portions of the shaped BPSK signals.

Abstract: A tracking phase locked loop circuit in which the frequency of an oscillator portion thereof is varied over a range of frequencies in search of an incoming carrier is disclosed. The varying frequency occurs at two different sweep rates. A faster rate is used until the frequency of the phase locked loop's oscillator nears the frequency of the incoming carrier, and a slower rate is used until the circuit locks onto the carrier. A filter couples between mixer and sweep control circuit portions of the phase locked loop to provide information concerning the difference between oscillator frequency and incoming carrier frequency. The sweep control circuit distinguishes between the carrier and noise and switches rates accordingly.

Abstract: The present invention consists of an apparatus comprising a phase locked loop and a frequency loop having a discriminator and a disable. The disable is used to electrically disconnect the frequency loop from the phase locked loop when the phase of the output from the voltage controlled oscillator is within a preset range of the incoming signal. The disable acts to provide an adjusting voltage signal, set by the discriminator, to the phase locked loop when the output and input signal phases are out of the preset range. When they are within the preset range the disable outputs a zero voltage regardless of the input from the discriminator.

Abstract: Generating apparatus providing a preferred pulse envelope which is compared to the envelope of output pulses from a nonlinear power amplifier, the error between the two being used, along with a stored predistorted pulse, to generate an updated predistorted pulse that is utilized to modulate the input signal to the nonlinear amplifier to produce a pulse at the output thereof having the preferred envelope and to update the stored predistorted pulse.