Abstract: A transimpedance stage amplifier converts a current input signal at an input node to a low impedance output voltage at an output node. The amplifier includes a resistor connected between the input node and the output node. A feedback loop is connected across the resistor, the feedback loop comprising a transistor, the transistor using the current input signal as a biasing current.

Abstract: A variable attenuator comprises bipolar transistors Q1 and Q2 connected in reverse parallel between a point 1 and ground potential G. The base electrodes of the transistors Q1 and Q2 are biased independently by a control circuit 3. The collector of transistor Q1 and the emitter of transistor Q2 are commonly connected to a bias voltage provided by resistor R2 and voltage source Vr. The attenuator provides means by which the linearity, gain, power handling capabilities and noise figure of a front-end receiver can be altered. The attenuator is susceptible to integration in, for example, a radio receiver front-end.

Abstract: A high power radio frequency (RF) precision step attenuator includes a trim attenuator, a multi-step attenuator and a calibration/control circuit. The control circuit includes a memory for storing attenuator specific calibration data. The calibration data incorporates attenuator characteristics which are used by the control circuit to adjust the attenuator and compensate for manufacturing variances, temperature variations, and the like.

Abstract: The present invention is directed to a method and apparatus for linearizing the response of a PIN diode attenuator. A plurality of Zener diodes form a diode array. Each Zener diode has the same Zener voltage value. The cathode of a first Zener diode is coupled to an input of the diode array. The cathode of a second Zener diode is coupled to the anode of the first Zener diode. The cathode of each subsequent Zener diode is coupled to the anode of the preceding Zener diode. The anode of each Zener diode is coupled to a respective impedance. The respective impedances are further coupled in common to an output of the diode array. An amplifier provides gain and offset. The diode array output is coupled to the amplifier input. A driver provides output drive. The amplifier output is coupled to the driver input. The driver output is used for linearizing the response of a PIN diode attenuator.

Abstract: An electronic vernier realizes programmable gain steps with first and second impedance ladders, a plurality of activatable coupling networks and a switch network. The ladders receive and progressively process the differential input signal into a plurality of progressive differential signals. In an embodiment, the coupling networks each generate a respective one of a plurality of progressive differential output signals in response to a respective one of the progressive differential signals and the switch network activates any selected one of the coupling networks. Thus, any selected vernier step is obtained by activating the respective coupling network. The verniers can be integrated into various systems, e.g., programmable amplifiers.

Abstract: This invention discloses a balancing circuit for providing a substantially fixed level of attenuation within a given return path frequency passband, while preventing noise related harmonics from distorting signal transmissions within the return path frequency passband. The balancing circuit includes coupling capacitors which are connected in series between input and output end nodes. A series connected inductor and capacitor pair is connected between each of the input and output end nodes and ground to form end sections. Another inductor is connected between the coupling capacitors and ground. A resistor is connected in parallel with the respective capacitor of each end section. The balancing circuit is placed in series at each subscriber port, and may be mounted on a printed circuit board and enclosed within a tubular housing with mating male and female "F" connections.

Abstract: Digital control of analogue beamformers utilising PIN diodes in a shunt circuit bi-phase attenuator arrangement is difficult because of the diodes extremely non-linear control response. There is disclosed a PIN diode circuit arrangement comprising a digital to analogue converter (DAC) with a reference voltage controller arranged to vary the DACs response to digital input signals to compensate for the PIN diode's non-linear response making this look substantially linear in the digital domain. The circuit preferably incorporates a feedback arrangement from the output of the DAC to its reference voltage input.

Abstract: A frequency dependent resistor in which the length of the current path across the resistor varies as a function of the frequency of the electrical signals being passed therethrough. The resistor uses the principal known as skin effect to direct relatively higher frequency signals through a longer path through the resistor than is experienced by signals having a relatively low frequency.

Abstract: A temperature compensating voltage variable attenuator includes at least two temperature variable resistors. The temperature variable resistors have different temperature coefficients of resistance, preferably, with one temperature variable resistor having a positive temperature coefficient of resistance and the other temperature variable resistor having a negative temperature coefficient of resistance. The temperature coefficient of resistance of the temperature variable resistors being such that the attenuation of the attenuator varies with changes in temperature of the attenuator. A voltage variable heater resistor is adjacent both temperature variable resistors so that a change in the voltage applied to the heater resistor changes the temperature of the heater resistor. The heat from the heater resistor is applied to the temperature variable resistors so as to change the resistance of the temperature variable resistors. This provides a controlled change in the attenuation of the attenuator.

Abstract: The attenuator is applicable to the art of identification, interrogation and communication equipment. The attenuator has particular application to equipment used in conjunction with smart cards, tags and like apparatus and including, in one form, an RF based technology, which has found a use in electronic ticketing, monitoring passenger movement and the identification and sorting of airline baggage and/or other items, such as containers or mail items. The attenuator, in one form, is predicated on the principle of creating a substantially opposing field, and applying this proximate the interrogator to substantially reduce stray field emissions. The attenuator, in another form, combines the physics of conducting tubes and self-cancelling fields and applies them to a tunnel interrogator. The attenuator thus applies a conducting tube which confines the field and the property of a loop generating a self-cancelling field to an interrogator. This combination may be called a "loop tube".

Abstract: In a switching circuit, low insertion loss and enough isolation can be ensured at a desired frequency at the same time. An inductor is externally connected in parallel with the path between the drain and source of each of field-effect transistors built in a switching integrated circuit, and the inductor and the OFF capacitance of the field-effect transistor are made to generate parallel resonance. At this time, by suitably adjusting the inductance, low insertion loss and enough isolation are ensured at a desired frequency at the same time.

Abstract: An equalizing filter with an optimized frequency response and improved reliability and quality, for equalizing a reception signal so as to regain its original waveform. The equalizing filter comprises a low-pass filter and a high-frequency booster circuit. With its limited passband, the low-pass filter rejects the noise components contained in the signal being processed. The high-frequency booster circuit has such a frequency response that exhibits a stepwise gain increase at high frequencies. Those two elements, composed of reliable passive components, are coupled in series to provide a combined frequency response that is optimized for the design of highly sensitive optical receivers. As integral part of the high-frequency booster circuit, the equalizing filter employs an inductor made of a bonding wire.

Abstract: A module for radio frequency signal circuits includes an electrically conductive housing. Coax connectors are secured to the rear face of the housing. A circuit board is contained within the interior spaced between sidewalls of the housing. A ground side of the circuit board includes a layer of electrically conductive material which is electrically connected to the housing. Coax cables extend within the interior of the housing from the coax connectors and between the ground side of the circuit board and an opposing sidewall. An opposite side of the circuit board contains circuit components inner connected with one another through a plurality of circuit paths. The components include directional couplers connected in series to combine branch circuits with each branch circuit having a separate attenuator.

Abstract: An attenuated cable is formed with an in-line attenuator conducted between two cable lengths wherein the cable lengths are rigidly joined together by a rigid hollow housing which encloses the attenuator therein. The attenuator circuit is housed within the housing, and is electrically connected to the cable lengths without the use of mechanical connections therebetween. The free ends of the cable lengths farthest from the housing are provided with standard connectors for connecting the cable to additional electrical devices such as microphones, mixers or amplifiers. Since the housing and attenuator circuit are relatively small and light relative to the larger cable lengths, the attenuated cable has substantially the same weight and flexibility as a continuous length of cable.

Abstract: The ease of mounting a circuit board on a nonradiative dielectric line is improved, the degree of freedom of conductor film patterns formed on the circuit board is increased, and the degree of integration can be easily increased to fit within a small size. Dielectric strips are provided between the two conductor plates positioned in parallel to each other, and a circuit board is positioned parallel to the conductor plates. The conductor patterns on the circuit board and the transmission waves of the nonradiative dielectric line are electromagnetically coupled to each other.

Abstract: A bandwidth compensated switched bridged-tee attenuator having an attenuation state and a reference state. In order to cause the overall bit attenuation .DELTA.A to be frequency independent over a relatively wide range of frequencies, one or more additional switches are provided to cause the attenuation state to essentially track the frequency dependence of the reference state. Since the overall attenuation .DELTA.A is the difference between the attenuation in the attenuation state and the attenuation in the reference state, the overall attenuation .DELTA.A, is virtually frequency independent over a relatively wide range of frequencies.

Abstract: A splitter/combiner module for radio frequency signal circuits includes an electrically conductive housing. Coax connectors are secured to the rear face of the housing. A circuit board is contained within the interior spaced between sidewalls of the housing. A ground side of the circuit board includes a layer of electrically conductive material which is electrically connected to the housing. Components on the circuit board include splitter/combiners for splitting a signal into a plurality of branch signals each having an individual attenuator component.

Abstract: A drain and a source of a field-effect transistor are connected to first and second signal terminals, respectively. A first control terminal is connected to a gate. A first resistor is interposed between the gate and the first control terminal. Capacitors are interposed between the source/drain and the first and second signal terminals, respectively. A control terminal is connected to at least one of the source/drain via a second resistor. High frequency signals supplied through the first signal terminal is sent through the field-effect transistor and outputted through the second signal terminal, and a quantity of the transmitted high frequency signals is controlled by a control voltage signal applied across the first and second control terminals. This structure provides a high frequency semiconductor integrated circuits which reduces a power consumption and an occupied area, increases a switchable power, suppresses output distortion, and simplifies a peripheral circuit.

Abstract: A control circuit is provided that can be used to compensate for pinch off voltage sensitive circuits. The control circuit comprises a control FET (26) having a gate (27), a drain (29), and a source (28). The control FET source (28) is connected to a tracking potential (23) through control FET source resistor (31) in series with a constant voltage drop element (32). A control voltage input (22) is applied to the control FET drain (29). A current flow through the control FET (26) results in a transfer function that is substantially linear for linear changes in control voltage input below a voltage pinch off value of the control FET (26). As the voltage control output (23) approaches the pinch off voltage value of the control FET (26), smaller changes in control voltage output (23) are realized for the same change in control voltage input (22).

Abstract: The present invention relates to a device for attenuating unwanted waves appearing in an electron tube which includes at least two coaxial cylindrical electrodes (2, 3). The electrodes (2, 3) contribute to forming the walls of a coaxial resonator. The unwanted waves to be attentuated generate surface currents in the walls of the coaxial resonator. The attenuation device includes several electrically conducting resistive elements (10) inserted into at least one wall of the resonator and arranged so as to cut the surface currents.

Abstract: A variable attenuator is provided with a plurality of amplifiers each comprising an emitter grounded or common source amplifier circuit. The amplifiers have different emitter degeneration impedances. One of the amplifiers is selected in accordance with a gain control signal under control of a current switch controller. The selected amplifier is connected to a current source and supplied with an operating current, and thus the selected amplifier is set in an operating state. The other amplifiers are not supplied with an operating current and thus do not operate. The gain of the variable attenuator is determined by a ratio between the emitter degeneration impedance of the selected amplifier and a load impedance.

Abstract: The microwave frequency chip resistor assembly is used as a terminating device for a video jack. Such an assembly minimizes inductance variation and eliminate soldering associated with conventional metal film resistors.

Abstract: It is an object of the present invention to provide a variable attenuator which can be produced at a low cost and can suppress production of unnecessary resonance and propagation. When the radio frequency resistance values of PIN diodes 13 and 14 are higher than a characteristic resistance value of a signal line interconnecting radio frequency signal input terminal 1 and radio frequency signal output terminal 2, the sum of voltages applied to PIN diode 11 and PIN diode 13 and the sum of voltages applied to PIN diode 12 and PIN diode 14, that is, V3, are controlled so as to be fixed.

Abstract: A discrete increment attenuator for processing an input signal by effecting discrete attenuation increments of the input signal to create corresponding attenuation states for the output signal resulting from the input signal, comprising a parallel branched attenuator network providing at least three attenuation states defining corresponding attenuation increments, coupled to receive the input signal and provide the output signal. A separate attenuation branch circuit having an input end and an output end corresponding to a particular plural parallel branch is selectively activated by an attenuation control signal for effecting a discrete incremental attenuation of the input signal.

Abstract: Solderless RF power film resistor and termination assemblies which include a flat film resistor or termination pressed by a nonmetallic clamping plate into thermal contact with a base plate functioning as a heat sink. A substrate such as a BeO ceramic substrate provides an RF power film resistor or termination, and has a flat mounting surface positioned against a flat mounting surface of the base plate. A clamping plate clamps the ceramic substrate securely against the base plate, thereby eliminating a soldered interface connection between the flat mounting surfaces of the ceramic substrate and the base plate. The clamping plate includes at least one lug, and the base plate includes at least one lug hole. The lug is larger than, and is plastically deformed into and through the hole to clamp the flat surface of the ceramic substrate securely against the flat surface of the base plate. The hole in the base plate preferably includes an undercut shoulder through and around which the lug is plastically deformed.

Abstract: An attenuator for signals in the frequency band of 50 to 800 MHz is subject to a range of AGC signal attenuating potentials. The attenuator includes a first attenuating PIN diode connected in series between an input and an output. The opposite ends of the first PIN diode are AC coupled via second and third impedance matching PIN diodes to an AC ground. The first PIN diode exhibits a frequency dependent slope over the wide signal frequency band and the range of AGC potentials. First and second inductors, in the form of metallic foil strips, are connected between the second and third PIN diodes and the AC ground. The foil strips are positioned in close proximity to each other and arranged such that signal currents flow therein in opposite directions to establish a negative mutual coupling coefficient for compensating for the frequency dependent slope of the first PIN diode.

Abstract: In a switching circuit, low insertion loss and enough isolation can be ensured at a desired frequency at the same time. An inductor is externally connected in parallel with the path between the drain and source of each of field-effect transistors built in a switching integrated circuit, and the inductor and the OFF capacitance of the field-effect transistor are made to generate parallel resonance. At this time, by suitably adjusting the inductance, low insertion loss and enough isolation are ensured at a desired frequency at the same time.

Abstract: A device provides, with passive circuits only, an output voltage in which ch spectral component is phase-shifted and attenuated by programmable values in relation to the spectral component of same frequency of an input signal. An adapter circuit (CA) applies the input signal V.sub.E onto two transfer channels (VT1 and VT2) which generate two signals with quadrature spectral components and with amplitudes multiplied by a coefficient of -1-+1. These signals are added in an adder circuit (CAD) which provides the output signal. The driver circuit (CC) receives the required phase-shifting and attenuation commands and corrects, if need be, the defects of the assembly through the control signals of the transfer channels (VT1 and VT2).

Abstract: A first bypass capacitor and a second bypass capacitor are connected in series between an input terminal and an output terminal for high frequency signals. A quart-wave line and a diode are connected between the connecting point of the first and second bypass capacitors and the ground, and a choke coil is connected between the connecting point and a D.C. voltage input terminal. When input signals are not to be attenuated, a D.C. voltage is fed from the D.C. voltage input terminal, and no D.C. voltage is fed when the signals are to be attenuated.

Abstract: The ease of mounting a circuit board on a nonradiative dielectric line is improved, the degree of freedom of conductor film patterns formed on the circuit board is increased, and the degree of integration can be easily increased to fit within a small size. Dielectric strips are provided between the two conductor plates positioned in parallel to each other, and a circuit board is positioned parallel to the conductor plates. The conductor patterns on the circuit board and the transmission waves of the nonradiative dielectric line are electromagnetically coupled to each other.

Abstract: A digitally controlled programmable attenuator maintains tight phase matching between attenuated signals over wide ranges of frequencies and power levels regardless of the selected attenuation level. This is achieved with a multi-tap ladder network that sets a desired tap-to-tap dB step-size, a plurality of unity gain digitally switched voltage-to-voltage buffers that are connected between the respective taps and a common output, and a fixed gain stage that sets the attenuator's overall gain/attenuation. The buffers maintain a high and substantially constant impedance whether turned on or turned off. Phase matching within 0.2.degree. at frequencies up to 300 MHz for 30 dB of gain variation has been realized.

Abstract: A switching circuit further decreasing the insertion loss. The first capacitor is connected between the drain terminal of the field effect transistor and the ground and/or the second capacitor is connected between the source terminal of the field effect transistor and the ground, and the capacitances of the first and/or second capacitors are set to optimum values. Accordingly, the switching circuit can be easily obtained which is low in insertion loss at a desired frequency. Besides, since a bias circuit for generating bias voltage from control voltage which is applied to the two control terminals of a switching circuit using a field effect transistor is provided, a switching circuit which does not need exclusive bias terminals and is superior in isolation property can be realized.

Abstract: An r.f. radiation absorbing material able to hold off a 30 to 40 kV voltage difference is described as formed by a silicon rubber loaded with ferrite particles. The material is used to reduce self-oscillation in amplifiers.

Abstract: In the present invention a monolithic step attenuator has internal frequency compensation provided by a field effect transistor, or FET, fabricated to have a well defined drain-to-source capacitance. The drain-to-source capacitance of the FET cancels the effect of parasitic impedances, providing a constant frequency response for the monolithic step attenuator within a defined frequency range. In a first embodiment of the present invention, internal frequency compensation is provided by a FET connected in a shunt arm of a Tee resistor network forming the monolithic step attenuator. In a second embodiment of the present invention, internal frequency compensation is provided by a pair of FETs, each FET connected in one of two shunt arms of a Pi resistor network forming the monolithic step attenuator. In a third embodiment of the present invention, a multicell step attenuator is formed by connecting multiple monolithic step attenuators having internal frequency compensation in series.

Abstract: An array of termination resistors has symmetrical geometry producing essentially no net magnetic field and a resultant low inductance is fabricated on a substrate as disk resistors. Conductive through vias are formed in the substrate in an array pattern defining what will be resistor first and second contacts. Each disk resistor has one first contact located at the resistor disk center, and preferably four second contacts located symmetrically about the resistor disk and shared by four adjacent disk resistors. For each resistor, a annular-shaped disk of resistive material is fabricated on a first surface of the substrate, such that a central opening in the disk overlies at least the upper surface of a first contact via. The disk geometry and material determines its resistance. Next, a layer of conductive material is formed over the first surface of the substrate to cover at least the periphery of each disk, and to fill the central opening in each disk.

Abstract: A beam electronically steers, in real time, a multielement sensor array at radio frequencies. A sensor array is configured in one embodiment with orthogonal loops and orthogonal dipole elements. Each loop and dipole combination generates a polarized output signal which is routed, via a connection matrix, to an equal number of signal splitters. The resulting modal patterns are then routed to networks having quad hybrids and digitally user-controllable vector modulators. The signals outputted from the quad hybrids and the vector modulators of each of the networks are inputted to separate combiners. The signals outputted from the separate combiners of the networks are then recombined in combiners. The signals outputted from these combiners define the azimuth around the Z-axis, the elevation around the Y-axis, and the elevation around the X-axis, respectively.

Abstract: A bridge T attenuator which includes PIN diodes in both the bridge arm and in the shunt arm, and in which the current through the shunt arm is controlled with respect to the current through the bridge arm, so that the product of these two currents equals a constant. This is accomplished by a feedback loop. Thus a relatively simple, inexpensive, and entirely analog solution is provided for a bridge T attenuator to be used with a radio frequency signal, so that a prescribed level of attenuation set by a user may be maintained while the impedance is maintained at a fixed value over the entire attenuation range.

Abstract: An electronic circuit incorporating an operational amplifier and a feedback network consisting substantially of a plurality, N+M, of substantially identical non-linear elements connected in parallel in two groups of N and M elements each to provide a linear feedback stabilized gain or attenuation.

Abstract: In an electron beam tube, such as an IOT, ferrite loaded silicone rubber or some other ferrite loaded dielectric material, is carried by a wall of an input cavity. The material absorbs r.f. energy, reducing coupling between different parts of the tube which could otherwise result in undesirable oscillation. Furthermore, its provision on part of the input cavity wall enables easy access to be made for replacement and servicing requirements.

Abstract: A distortion generating circuit of the present invention comprises a linear attenuator which has an input impedance substantially coincident with an impedance of a transmission path of input signal and an output impedance substantially coincident with an impedance of a transmission path of output signal; and at least one diode which is connected in an alternating current manner in parallel with the linear attenuator with respect to the input signal into the linear attenuator and which generates nonlinear distortion for a component in the input signal input thereinto; which outputs an AC sum of an output from the linear attenuator and an output from the diode. By this arrangement, desired distortion can be well given in a simple circuit arrangement while suppressing generation of unnecessary intermodulation distortion. An optical transmitter, an optical receiver or an amplifier can be constructed using the distortion generating circuit of the present invention, obtaining a signal with reduced distortion.

Abstract: A temperature variable phase-shifter formed of passive components. The phase-shifter includes a power divider which is adapted to receive a signal and divide the signal into two components which are 90.degree. out of phase with each other. The outputs of the power divider are connected to positive and negative temperature variable attenuators which attenuated the components of the signal. The temperature variable attenuators are connected to a combiner which sums the attenuated signals from the temperature variable attenuators.

Abstract: Spurious frequencies are suppressed in a transmitter by an RF pulse fall time controller circuit comprising a quadrature hybrid matched attenuator located between a predriver and the first stage of class "C" driver amplifiers. The circuit linearly attenuates RF pulses and slows pulse fall time. Operation of the circuit is initiated when the rising edge of a pretrigger starts a pretrigger generator which then triggers the application of current bias to the attenuator circuit. After a controlled period of time, the circuit decreases the forward current bias of PIN diodes in the attenuator thereby increasing the diodes' series resistance and increasing the attenuation of the RF pulses. This creates a slow pulse fall time thereby suppressing spurious emissions caused by parasitic ringing of the cascaded Class C common base transistor amplifiers in the transmitter.

Abstract: A fully integrator RF attenuator performs gain control upon a received RF signal without the use of an off-silicon PIN diode. The attenuator includes a T-configuration pad in conjunction with a current source. A direct current signal biases a shunt element in the T-pad. Preferably, a voltage control signal which controls the direct current is generated as a negative feedback signal in proportion to the magnitude of the RF detected at the attenuator output.

Abstract: The attenuator device comprises a unit step attenuator 4 (having a switch FET 5, an attenuation resistor 6 connected in parallel to the switch FET 5, and two shutdown resistors 7 and 8); three current source circuits 20.sub.1, 20.sub.2 and 20.sub.3 (having three transfer gates 22.sub.1, 22.sub.2 and 22.sub.3 and three current source FETs 23.sub.1, 23.sub.2 and 23.sub.3 for controlling a gate current of the switch FET 5). The signal transmission loss and the layout area can be reduced as much as possible, even if various attenuation rates are required.

Abstract: A digitally controlled variable gain circuit which receives an analog input voltage and produces an analog output voltage. The digitally controlled variable gain circuit includes a first resistor string having first and second ends and a plurality of resistors connected in series between the first and second ends, the second end of the first resistor string being grounded and the analog input voltage being applied across the first and second ends of the first resistor string. A first selection mechanism, coupled to the first resistor string and responsive to a first digital control signal, provides a selectively determinable voltage divided output from the first resistor string.

Abstract: An attenuator for use with a current transformer. The attenuator includes an input voltage terminal, an input ground terminal, an output voltage terminal, an output ground terminal, an input resistive arm, a shunt resistive arm, an output resistive arm, and a compensation circuit. The input and output ground terminals are coupled together. The input resistive arm has a first end coupled to the input voltage terminal and a second end. The output resistive arm has a first end coupled to the output voltage terminal and a second end coupled to the second end of the input resistive arm. The shunt resistive arm has a first end coupled to the input and output ground terminals and a second end coupled to the second ends of the input and output resistive arms. The shunt resistive arm has a shunt resistance and an intrinsic inductance effectively in series with the resistance.

Abstract: A multifunction microwave modulator circuit has an input signal splitter to provide two equal amplitude signal components. A phase quadrature relationship between the two signal components is obtained by constructing the splitter as a Lange coupler. There is pair of circuit cells, each of which operates separately on one of the two signal components to electronically adjust a vector representation of the signal to provide a vector having a desired amplitude, ranging over both positive and negative values of amplitude, including zero amplitude. The signal vectors of the two cells are combined by means of a Wilkinson combiner to provide an output signal represented by a resultant vector which may have any direction within 360 degrees, and an amplitude scale factor which varies from unity to zero.

Abstract: A variable attenuation microwave attenuator includes input and output terminals, a high-pass filter having an electrical length of 90.degree. and transmitting signals with frequencies higher than a cut-off frequency, a first variable resistor connected between the input terminal and an input end of the high-pass filter, and a second variable resistor connected between an output end of the high-pass filter and the output terminal, wherein input signals applied to the input terminal are attenuated by the first and second variable resistors before and after the high-pass filter. Therefore, the variable attenuator can be a lumped parameter circuit, i.e., the high-pass filter including two inductors and a capacitor, without using a transmission line as in the prior art device, so that the size of the device is significantly reduced.

Abstract: A current bias-type variable attenuator. Two PIN diodes are disposed in series to each other and in the forward direction on a bias current path. When a bias voltage is applied to a bias terminal, d.c. current flows in the order of a combination output port, an in-phase output port, a first PIN diode, an input port, a 900.degree.--delayed phase output port, and a second PIN diode, or in the order of the combination output port, the in-phase output port, the first PIN diode, the second PIN diode, the 900.degree.--delayed phase output port, and the input port. Since d.c. current flowing through the first PIN diode and d.c. current flowing through the second PIN diode have an equal value, an RF resistance of the first PIN diode and that of the second PIN diode are balanced.

Abstract: An electrical circuit (200) having an input terminal (201), an output terminal (202), and a signal common (203) is preferably used to attenuate an electrical signal. The electrical circuit (200) comprises four impedance elements (205-208) and an impedance transformer (210). A first impedance element (205) is coupled between the input terminal (201) and a first node (212), while a second impedance element (206) is coupled between the first node (212) and the output terminal (202). A third impedance element (207) is coupled between the input terminal (201) and the output terminal (202), while a fourth impedance element (208) is coupled between a second node (213) and the signal common (203). The impedance transformer (210) is coupled between the first node (212) and the second node (213) to complete the electrical circuit (200).