An active device, such as a field effect transistor ("FET"), converts microwave signals between a slot transmission line ("slotline") and a coplanar waveguide ("CPW") In slotline-to-CPW conversion using one or more FETs, a gate connection is made to one or both of the slotline conductors. A drain connection is made to the center conductor on the CPW. Two FET source terminals are connected respectively to each CPW ground strip and may be coupled to a slotline conductor. The active device can be reconnected so as to reverse the input and output, providing for conversion of signals from CPW to slotline. Conversion between balanced-signal slotline and CPW further includes passive or active phase shift of one signal path.
A field-effect transistor device includes an active area on a semiconductor substrate and a gate electrode, a source electrode, and a drain electrode are disposed on the surface of the active area, so as to define an FET portion. An electrode defining a line for connection to the gate, an electrode defining a line for connection to the source, and an electrode defining a line for connection to the drain are disposed on the semiconductor substrate. The electrodes define a slot line on the input side for supplying a signal to the FET portion, and a slot line on the output side from which a signal of the FET portion is output. The gate electrode has a shape which extends along the direction that approximately perpendicular to the conduction direction of the signal through the slot line on the input side.
A hybrid 180.degree. microwave balun device is provided to convert an unbalanced RF signal at the common port into two radio frequency signals with equal amplitude and 180.degree. phase difference at two differential ports. The hybrid device includes a coplanar waveguide connecting to the common port. A power divider separates the coplanar waveguide into two symmetrical slotline waveguides to carry balanced signals. Two broadband multioctave slotline to microstrip transitions constructed in a way that the microstrip lines carry 180.degree. phase separated signals to the differential output ports.
An unbalance-to-balance converter includes an FET and a balanced output adjusting capacitor connected between the source terminal of the FET and an earth conductor. The balanced output adjusting capacitor has a capacitance value equal to a capacitance difference Cpd-Cps between a drain side parasitic capacitance Cpd and a source side parasitic capacitance Cps. This makes it possible to solve a problem involved in a conventional unbalance-to-balance converter in that when the drain side parasitic capacitance Cpd differs from the source side parasitic capacitance Cps, a pair of balanced signals output from the drain terminal and source terminal do not have the same amplitude and are not in complete opposition.
In a transmission output stage for a multifrequency mobile telephone, the transmit signal of operation at the low frequency is generated by a push-pull output stage which is operated in single-ended mode for generating the transmit signal at the higher frequency.
A transmission line substrate includes a spurious-wave suppression circuit in which a divider divides a signal line of a driving control signal connected to a semiconductor device into two signal lines of the same phase. A delay unit is connected to one of the two signal lines, and includes a signal line with a length of substantially one half of an in-substrate effective wavelength of a spurious wave. Two parallel lines that include two parallel signal lines, on which spurious waves are in opposite phases, are connected to the delay unit and the other one of the two signal lines, respectively. A resistor is arranged on the two parallel lines, and connects between the two parallel signal lines. A combiner includes a signal line that combines the two parallel signal lines, and outputs a combined signal to the outside.
