Ford Aerospace & Communications Corporation

Rca Inc.

Pang T Ho

Michael D Rubin

The amplifier device, which may be an FET power amplifier, is of the type having an operating parameter which exhibits thermal instability under constant electrode bias conditions, and thermal stability when bias is varied as a function of ambient temperature in accordance with an empirically determined relationship. The method involves the empirical determination of the varying bias conditions needed to cause thermal stability of the operating parameter over the required range of temperatures, and the provision of a temperature-compensating power supply which produces the necessary bias at each temperature in the range. The temperature-compensating power supply incorporates a bias monitor circuit to produce a control signal which has a nearly constant value so long as bias conditions are in accordance with the empirically determined relationship at every temperature within the range. However, if bias deviates from the predetermined relationship, the control signal also deviates, such that control signal deviations are a monotonic function of bias deviations. The power supply is provided with a feedback-control circuit which responds to the control signal deviations by adjusting the output magnitude of the supply to agree with the predetermined relationship.

Temperature compensating method and apparatus for thermally stabilizing

This device enables one to perform individual measurements, tests, and tuning of active elements in a circuit in which the active elements are combined using couplers. Typically, the active elements are amplifiers which are power combined using quadrature power dividers and combiners. The invention uses two additional quadrature couplers, one at the front and one at the back of the circuit. All the power is introduced into one input port of the first additional coupler. The action of the first two couplers results in power flowing through one of the active elements only. The action of the second pair of couplers results in the flow of power through one output port only. After testing, the additional couplers are removed. The invention enables the one step fabrication of components on the substrate followed by testing, rather than the more time consuming and complex separate assembly and testing of four substrates.

Apparatus and method for individually testing combined active elements

A field effect transistor bias circuit is presented which exhibits a low impedance for small signals and a high impedance for large signals. This circuit uses an operational amplifier to provide a temperature compensated low impedance voltage source for the gate bias which is optimal for small signal operation. In the presence of a large signal, the gate begins to draw current. This causes the operational amplifier to saturate and transforms the bias circuit into a high impedance source, which is optimal for large signal operation.

Input optimized FET bias circuit

A redundant microwave switching matrix providing equal power distribution of any of a plurality of microwave input signals among one or more of a plurality of microwave output signals. The redundant switching matrix used in a communication satellite selectively couples one or more of a plurality of input microwave signals received by receiving antennas among one or more of a plurality of output microwave signals radiated by transmitting antennas. The means for coupling the input and output microwave signals is provided by a pair of directional couplers diametrically positioned at each coordinate of the switching matrix. A controller selectively enables a pair of PIN diodes, internally positioned within each directional coupler, to perform the desired coupling. Diametrically positioned directional couplers, having a pair of PIN diodes, provide a highly reliable and flexibility microwave switching matrix.

Redundant microwave switching matrix

An impedance transforming coupler is disclosed which may be used as a power divider or power combiner at microwave frequencies. The power division or power combination ratio is arbitrary, and the impedance transformation ratio is arbitrary. These couplers may be used in a circuit to power-combine amplifiers. The insertion loss of the circuit is low and the bandwidth is improved by an order of two to one over prior art systems which had separate circuits for matching the impedance and providing power combining. The coupler is optimally a branch line coupler having four curved branches a quarter wavelength long at the center frequency. The output ports are 90.degree. out of phase. Simple formulas are given relating the desired admittances of each of the four branches to k, the desired power coupling ratio, and Y, the desired admittance transformation ratio.

Coupler having arbitrary impedance transformation ratio and arbitrary

An active microwave amplifier element is hermetically sealed on the opposite side of a dielectric substrate from the side in which input and output signals are transmitted. The active element is mounted on a ground plane and is electrically connected to coplanar waveguide elements which are coplanar with the ground plane. The coplanar waveguide elements are electrically connected to associated microwave strips through the dielectric substrate and said holes are also sealed. A cap having similar coefficient of thermal expansion to the dielectric substrate is mounted on the ground plane to enclose and hermetically seal the active element.

Hermetically sealed active microwave integrated circuit

This circuit divides power from an input source equally among N different paths, where N is an arbitrary number. These individual path powers can then be amplified separately to take advantage of the full output power ratings for the individual amplifiers, then the outputs from the amplifiers are combined. A combiner circuit, which is the reverse of the divider circuit, then combines the individual powers to a single output. In each of the combiner and divider circuits, the phase angles of the output ports vary from each other by 90 degrees sequentially down the entire chain of N-1 couplers. Each combiner and divider network utilizes N-1 series-connected couplers, preferably interdigitated ones. The interdigitated couplers utilize preselected power division ratios based upon N.

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Mountain View, CA, United States of America

Pang T Ho