A radio frequency circuit having at least one output terminal includes a plurality of non-linear elements, each having an output electrode. Means are provided for feeding at least one input signal to each one of the non-linear elements. The feeding means includes an electrical pathlength including at least one two port phase shifting element fed by at least the input signal, for providing a plurality of signal portions, each one fed to a corresponding one of the plurality of non-linear elements. These signal portions have a successively increasing phase shift related to the electrical pathlength of the two port phase shifting elements. The output electrodes of each non-linear element are interconnected by an input coupling means including at least one, different, two port phase shifting element, for successively electrically interconnecting the output electrode of each non-linear element. With such an arrangement, by providing two port phase shift elements in the input and output coupling means, proper phasing characteristics may be provided to such circuits without the necessity of using couplers or baluns which are generally difficult to fabricate, particularly, as broadband monolithic microwave integrated circuits.
A double balanced microstrip mixer circuit for a monolithic microwave integrated circuit comprising a diode ring modulator coupled to a first balun for supplying radio frequency signals to the mixer circuit and a second balun for supplying a signal generated locally to the mixer circuit, two outputs leading from the diode ring modulator for providing an intermediate frequency signal, a first pair of circuits coupled between the first balun and the diode ring modulator and a second pair of circuits coupled between the second balun and the diode ring modulator, for enabling broadband frequencies to be applied to the diode ring modulator independent of impedances created by the first and second baluns. The circuit further includes two low pass filters each coupled to one of the two outputs for rejecting unwanted feed through and a in-phase combiner coupled to the low pass filters.
Monolithic broadband semiconductor single-pole, double-throw switches are merged into distributed monolithic amplifiers and decrease the total semiconductor chip area occupied by the devices.
A frequency converters used in communications receivers. Such frequency converters can be used for converting a signal from a Radio Frequency (RF) to a low frequency suitable for processing such as demodulation. The inventors have made the unexpected discovery that when the gates of the MESFETs of a double-balanced mixer are left open-circuited and allowed to self-bias, the drop in mixer linearity at high LO power levels is reduced thereby increasing the LO power range of operation. This invention can be used as an improved scale-down mixer as well as an upconverter mixer.
In a mixer circuit, a first gate 25a of a dual gate MESFET 1 having pulse doped structure is connected through a filter 4 to an LO signal input terminal 5, and a second gate 25b is connected through a matching circuit 6 to an RF signal input terminal 7. The drain 27 of the FET 1 is connected through a low-pass filter 10 to an output terminal 11. The gate bias point of the first gate 25a is set in the vicinity of the pinch-off point of the mutual conductance, and the gate bias point of the second gate 25b is set in the area where the mutual conductance is unvaried with increase of the gate voltage. With this arrangement, the mixer circuit can be so designed that the isolation characteristic of the RF signal and the LO signal is excellent, and a stable operational characteristic can be obtained.
In a mixer circuit, a first gate electrode of a dual gate MESFET having a pulse doped structure is connected through a filter to an LO signal input terminal, and a second gate electrode of the dual gate FET is connected through a matching circuit to an RF signal input terminal. The drain electrode of the dual gate FET is connected through a low-pass filter to an output terminal. The gate bias point of the first gate electrode 25a of the dual gate FET is set in the vicinity of the pinch-off point of the mutual conductance, and the gate bias point of the second gate electrode 25b of the dual gate FET is set in the area where the mutual conductance is unvaried with increase of the gate voltage. With this arrangement, the mixer circuit is so designed that the isolation characteristic of the RF signal and the LO signal is excellent, and a stable operational characteristic is obtained.
