Ford Aerospace & Communications Corporation

Space Systems/loral, LLC

Michael D Rubin

Pang T Ho

Philip D Crill

A multi-port amplifier system for multi-beam communication antennas in which redundancy is achieved without using RF switches. The multi-port amplifiers are divided into sets of stages arranged in tree fashion and the amplifier stages can be turned off without degrading port-to-port isolation. In one embodiment there are thirty-two input ports 1 through 32 and thirty-two corresponding output ports 1 through 32 wherein input port 1 is functionally connected to output port 1 and so on. An input signal to each of the input ports 1 through 32 is connected to a separate one of a first group of sixteen, four stage multi-port hybrid circuits. The outputs of the first group of multi-port hybrid circuits are connected through solid-state power amplifiers to a second group of sixteen, four stage multi-port hybrid circuits which are also labeled according to the input port numbers to which they are functionally connected.

Multi-port amplifiers with switchless redundancy

An r.f. phase modulator operable at up to extremely high frequencies. A circulator (1) having input, output, and isolated ports (2, 3, 4, respectively), channels an r.f. carrier (15) in a prescribed direction. Fitting into an open end of the output port (3) is a moving reflective surface (6) coupled via a moving plunger (7) fixedly mounted at one end thereof to a housing (5) fixedly mounted with respect to the circulator (1). A modulating signal (9) is applied to the plunger (7), causing the reflective surface (6) to move linearly within the output port (3). This change in path length of the carrier (15) produces linear phase modulation thereon. The plunger (7) can comprise a magnetostrictive material (7A), a piezoelectric material (7B), a thermally expansive material (7C), or a combination thereof. The invention can be used for temperature compensation and phase stabilization as well as phase modulation.

r.f. Phase modulator

A method and apparatus for demodulating quadrature phase shift keyed (QPSK) signals in a manner which reduces crosstalk between channels. The in phase (I) data is recovered first by recovering the carrier frequency and then multiplying the carrier frequency by the QPSK signal. The I channel is contemplated to require higher power and thus the crosstalk error in the recovered I channel data is relatively small. The QPSK signal is then modulated with the recovered I channel data. The resulting signal is multiplied by a carrier in quadrature to the recovered carrier to produce a second signal in which the crosstalk component has been eliminated and which contains the quadrature (Q) channel data with the I channel modulation. The I channel modulation is removed by modulating the signal again by the I channel data to produce a signal containing only the Q channel data.

Crosstalk reduction in unbalanced QPSK detectors

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

Disclosed is a circuit for protecting a transformer from high voltages in those cases where a differential and a common mode output exist at the secondary of the transformer. The differential output is a load having a relatively small voltage thereacross; the common mode output is an output terminal connected to said load and having a relatively high voltage applied thereto. The present invention replaces the transformer with two or more smaller transformers cascaded together. A resistor is connected between the primary and the secondary of each transformer. Together the resistors form a voltage dividing network which splits the single high voltage among all of the transformers, relieving the stress on each. Optional capacitors are connected in parallel across each of the resistors in the case where the interwinding capacitances of the transformers are not equal. Each of the load and the output terminal can be either an a.c. or a d.c. component. If the load is a d.c. component, a rectifier/filter is inserted between the secondary of the last transformer in the chain and the load.

Circuit for reducing voltage stress across a transformer

This circuit compensates for phase variation introduced by the delay element in a PSK (phase shift keyed) demodulator. The signal to be demodulated is split. One portion is delayed while the other portion is fed to a variable phase shifter and then to a hybrid splitter. The delayed signal and quadrature output of the hybrid splitter are fed to a phase detector which recovers the information. The delayed signal and inphase output of the hybrid splitter are fed to a phase tracking circuit. This phase tracker controls the variable phase shifter in a manner which maximizes the detected signal by compensating for phase variations introduced by the delay element. The fixed component of difference in phase between the delayed signal and the shifted signal is either a multiple of 180.degree. or an odd multiple of 90.degree. , depending upon the coding system employed.

PSK Demodulator with automatic compensation of delay induced phase shifts

A differentially coherent signal detector capable of detecting arbitrary-even-ordered phase shift keyed signals, such as quadraphase (QSK), hex (HSK), octo (OSK), etc. In the case of QSK, the signal to be demodulated is split. One portion is delayed while the other portion is fed to a variable phase shifter and then to a hybrid splitter. The delayed signal and quadrature output of the hybrid splitter are fed to a quadraphase detector which recovers the information. The delayed signal and inphase output of the hybrid splitter are each fed to a phase tracking circuit via frequency doublers. The phase tracker controls the variable phase shifter in a manner which maximizes the detected signal by compensating for phase variations introduced by the delay element. In the case of Nth-order phase shift keyed signals, where N is even, the frequency doublers are replaced by frequency multipliers having a multiplication factor of N/2, and the quadraphase detector is replaced by a detector capable of detecting that particular order.

Differentially coherent signal detector

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

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.

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Saratoga, CA, United States of America

Michael D Rubin