Abstract: A transistor biasing circuit is shown that utilizes a negative feedback loop control circuit to set the gate bias voltage in the output transistors of a power amplifier. This control circuit has a current sensor in series with the drain of the transistor, the current sensor output in turn feeding a dc signal into a dc amplifier, and the output of the dc amplifier driving a gate bias integrator which forms a dc control loop for maintaining the bias point. The output transistor is protected from excessive temperature and/or excessive power dissipation.

Abstract: A protection circuit for Darlington amplifiers prevents destructive voltage overshoot conditions from occurring. The Darlington amplifier has a pair of transistors connected in a Darlington configuration. A biasing network is coupled to the transistors for supplying a bias voltage to the transistors. A pair of de-coupling capacitors is coupled to the transistors. One of the de-coupling capacitors is coupled to the input of the Darlington amplifier and the other is coupled to the output. The output capacitor has a larger capacitance than the input capacitor such that excessive voltage is prevented from developing on the transistors.

Abstract: A test apparatus and method of measuring pulling of the frequency of an oscillator. The apparatus includes a bias tee, a power supply, a spectrum analyzer, a second power supply, a symmetrical resistive power splitter, a power meter and a synthesized signal generator. The method includes sweeping the synthesized signal generator frequency from the nominal frequency down to a first frequency. The first frequency is recorded when the oscillator goes out of frequency lock as a first pulling frequency. The synthesized signal generator frequency is then sweet from the nominal frequency up to a second frequency and the second pulling frequency is recorded when the oscillator goes out of frequency lock. The difference between the first and second pulling frequencies is the peak to peak pulling value.

Abstract: A band pass hairpin filter that has improved pass band performance and low loss. The filter has a dielectric substrate. The dielectric substrate has a top and bottom surface. A hairpin resonator is mounted to the top surface. The resonator has an open end and a closed end. An input coupling element is located adjacent to and is communicated with the resonator. An output coupling element is located adjacent to and is communicated with the resonator. A first inductive element is connected to the resonator. A second inductive element is connected to the input coupling element. A third inductive element is connected to the output coupling element.

Abstract: A protection circuit for Darlington amplifiers prevents destructive voltage overshoot conditions from occurring. The Darlington amplifier has a pair of transistors connected in a Darlington configuration. A biasing network is coupled to the transistors for supplying a bias voltage to the transistors. A pair of de-coupling capacitors is coupled to the transistors. One of the de-coupling capacitors is coupled to the input of the Darlington amplifier and the other is coupled to the output. The output capacitor has a larger capacitance than the input capacitor such that excessive voltage is prevented from developing on the transistors.

Abstract: A test apparatus and method of measuring pulling of the frequency of an oscillator. The test apparatus includes a bias tee, a power supply, a spectrum analyzer, a second power supply, a symmetrical resistive power splitter, a power meter and a synthesized signal generator. The method includes setting the power supply voltages and measuring the RF power at the power meter. Next, the synthesized signal generator power level is set to a first level and the frequency is set to the nominal oscillator frequency under test. The spectrum analyzer frequency range is set to a first range. Then the synthesized signal generator frequency is swept from the nominal frequency down to a first frequency. When a signal above a pre-determined noise level is detected, it is indicative of the oscillator under test going out of frequency lock. The frequency of the synthesized signal generator is recorded as a first pulling frequency.

Abstract: A band pass hairpin filter that has improved pass band performance and low loss. The filter has a dielectric substrate. The dielectric substrate has a top and bottom surface. A hairpin resonator is mounted to the top surface. The resonator has an open end and a closed end. An input coupling element is located adjacent to and is communicated with the resonator. An output coupling element is located adjacent to and is communicated with the resonator. A first inductive element is connected to the resonator. A second inductive element is connected to the input coupling element. A third inductive element is connected to the output coupling element.

Abstract: A variable frequency oscillator which exhibits low phase noise by increasing the quality factor of the resonator in the oscillator circuit. This is achieved by employing multiple means of decoupling the resonator from all elements and circuits to which the resonator is connected. For example, the resonator is decoupled from the whole oscillator circuitry by connecting the oscillator to a tap on the resonator which reflects the oscillator as a lighter load across the entire resonator. The resonator is further decoupled from the emitter to the base junction circuitry by placing a impedance network between the base of the transistor and the ground. Additional decoupling circuitry is employed to reduce the loading of the resonator due to the external oscillator load.

Abstract: A load pull circuit with a monitoring port which provides a constant VSWR throughout a phase variation in excess of 360°. The fundamental circuit comprises a fixed resistor of fifty ohms placed in series with an external fifty ohm load monitoring port resistor to ground. In parallel with the two series resistors, which total 100 ohms, is placed a 33.3 ohm resistor that is connected to ground through a series L-C circuit. The capacitance in the L-C circuit is adjustable and can be varied to cause the L-C circuit to change in net value from being inductive, to being resonant, and finally being capacitive. This causes the 33.3 ohm resistor to be connected to ground through an inductor, then through a short, and finally through a capacitor, making the load pull circuit present a load that vary through 360 degree in phase, while still remaining at a VSWR of 2:1. The inductor in the L-C circuit is a varactor, making the sweep through all 360° totally electronically controllable and simple to automate.

Abstract: A fine tuning system for adjusting the frequency of voltage controlled oscillators with fine resolution by mechanical tuning. A resonator is located on the dielectric substrate resonant frequency. The tuning system has metal strip located on a dielectric substrate. The metal strip has a pair of edges and a primary cut extending into the metal strip. The primary cut has a pair of ends. Several cavities in the metal strip are located adjacent an end of the primary cut. An elongated slot is cut into the metal strip. The slot is located between the cavities and an edge. The slot reduces the coupling of the tuning elements such as shorts, formed by cavities, to the resonator, and therefore allows fine tuning of the resonant frequency. Location of the slot closer to the cavities results in more fine tuning. Location of the slot further away from the cavities results in coarse tuning. An alternative embodiment is shown.

Abstract: A fine tuning system for adjusting the frequency of voltage controlled oscillators with fine resolution by mechanical tuning. A resonator is located on the dielectric substrate resonant frequency. The tuning system has metal strip located on a dielectric substrate. The metal strip has a pair of edges and a primary cut extending into the metal strip. The primary cut has a pair of ends. Several cavities in the metal strip are located adjacent an end of the primary cut. An elongated slot is cut into the metal strip. The slot is located between the cavities and an edge. The slot reduces the coupling of the tuning elements such as shorts, formed by cavities, to the resonator, and therefore allows fine tuning of the resonant frequency. Location of the slot closer to the cavities results in more fine tuning. Location of the slot further away from the cavities results in coarse tuning. An alternative embodiment is shown.

Abstract: A variable frequency oscillator which exhibits low phase noise by increasing the quality factor of the resonator in the oscillator circuit. This is achieved by employing multiple means of decoupling the resonator from all elements and circuits to which the resonator is connected. For example, the resonator is decoupled from the whole oscillator circuitry by connecting the oscillator to a tap on the resonator which reflects the oscillator as a lighter load across the entire resonator. The resonator is further decoupled from the emitter to the base junction circuitry by placing a impedance network between the base of the transistor and the ground. Additional decoupling circuitry is employed to reduce the loading of the resonator due to the external oscillator load.