Abstract: A voltage-controlled oscillator in which a tunable resonator (102) having a first port (132) and a second port (106) is disclosed. In one embodiment, the tunable resonator is a series resonating circuit having low driving and load impedances. A power gain element (108) is coupled to the first port and the second port, and an output port (110) is coupled to the power gain element and the second port. The first impedance at the first and second ports is less than approximately ten ohms. The voltage-controlled oscillator is capable of generating a signal at the output port of greater than approximately half a watt.

Abstract: A voltage-controlled oscillator in which a tunable resonator (102) having a first port (132) and a second port (106) is disclosed. In one embodiment, the tunable resonator is a series resonating circuit having low driving and load impedances. A power gain element (108) is coupled to the first port and the second port, and an output port (110) is coupled to the power gain element and the second port. The first impedance at the first and second ports is less than approximately ten ohms. The voltage-controlled oscillator is capable of generating a signal at the output port of greater than approximately half a watt.

Abstract: A low noise oscillator for use in a radio which provides an output signal with high signal-to-noise ratio. The low noise oscillator includes a voltage controlled oscillator which produces an intermediate sinusoidal voltage signal in response to a DC tuning voltage. The voltage controlled oscillator includes a varactor and junction field effect transistor. The low noise oscillator also includes a buffer amplifier which receives the intermediate sinusoidal voltage signal from a tapped microstrip of the voltage controlled oscillator and produces a highly stable output signal proportional to the DC tuning voltage applied to the input of the low noise oscillator. The buffer amplifier employs a dual gate Gallium Arsenide field effect transistor.

Abstract: An amplifier protector and method for preventing power overload of a power amplifier and destruction of transmission circuitry and printed wiring board. The protector continually monitors the peak forward and reflected voltages of the transmitter output which are proportional to the forward and reflected power. An associated processor determines whether the forward voltage is below a threshold voltage which indicates a circuit malfunction. If the circuit malfunction is detected, the processor via an automatic level control circuit turns off the power amplifier in a timely fashion to prevent damage to the transmission circuitry.

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 voltage tunable bandpass filter consisting of a plurality of parallel resonators electromagnetically coupled and having tuning diodes coupled to a first end. The resonators are DC isolated at a second or RF grounded end of each resonator. A voltage source reverse biases the tuning diodes from the second or less critical end of the resonators.

Abstract: A radio frequency amplifier includes a bipolar and a field effect transistors (FET) which are cascoded for efficient operation and simultaneous gain control. Bias circuitry is connected to the control electrode of the FET to stabilize the output bias thereof. Negative feedback circuitry is connected between the output electrode of the FET and the control electrode of the bipolar transistor to stabilize the other bias levels within the circuitry. An AGC circuit is connected to the feedback circuitry to provide an automatic gain control function.