A system for thermally protecting an amplifier driving a capacitive load may include a low-pass filter configured to filter, with a variable cutoff frequency, an input signal to generate a filtered input signal, wherein the amplifier is configured to receive the filtered input signal and amplify the filtered input signal to generate a driving signal to the capacitive load and a controller configured to receive a real-time estimate of a temperature associated with the amplifier and vary the variable cutoff frequency as a function of the temperature.

Provided is an impedance matching device for matching an impedance between a high-frequency power source and a load. The impedance matching device pertaining to the present invention is provided with: a matching circuit having variable capacitors, a capacitance of which is adjusted by an ON/OFF operation of a plurality of switches; a switch control unit for performing control for causing states of the switches of the variable capacitors to coincide with a target state in order to adjust the capacitance of the variable capacitors; and a switch state evaluation unit for evaluating whether a switch is in a state requiring suppression of a temperature increase. The switch control unit is configured so that when the switch state evaluation unit evaluates that a switch of the variable capacitors is in a state requiring suppression of a temperature increase, control is performed for suspending changing of a switch state of the switch for a set period and suppressing a temperature increase in the switch.

Various embodiments of the invention relate to a high accuracy phase shift apparatus. The phase shift apparatus comprises a voltage controlled analog phase shifter, a microcontroller unit (MCU) and a digital-to-analog converter (DAC). The MCU generates a digital control signal, which is converted into an analog control signal by the DAC to control the voltage controlled analog phase shifter to achieve desired phase shift angle. The phase shift apparatus may further incorporate a temperature sensor for temperature compensation. The output from the temperature sensor may be used to modify the reference voltage of the DAC, or alternatively be used to modify the digital control signal from the MCU. By incorporation digitalized control and temperature compensation to an analog phase shifter, the disclosed phase shift apparatus achieves high accuracy digitalized control, a flat phase shift over a wide bandwidth, and a stable phase shift over temperature variation.

A frequency equalizer is provided. The frequency equalizer includes a coupler including a main segment extending between a first port and a second port and a coupled segment disposed in a coupling relationship with the main segment and extending between a third port and a fourth port. The frequency equalizer further includes a first thermistor electrically coupled in series between the first port and an input line, a second thermistor electrically coupled in series between the second port and an output line, and a first shunt resistor coupled across the third port. The frequency equalizer simultaneously provides frequency equalization and temperature compensation for signals transmitted through the frequency equalizer.

A frequency equalizer is provided. The frequency equalizer includes a coupler including a main segment extending between a first port and a second port and a coupled segment disposed in a coupling relationship with the main segment and extending between a third port and a fourth port. The frequency equalizer further includes a first thermistor electrically coupled in series between the first port and an input line, a second thermistor electrically coupled in series between the second port and an output line, and a first shunt resistor coupled across the third port. The frequency equalizer simultaneously provides frequency equalization and temperature compensation for signals transmitted through the frequency equalizer.

Aspects of this disclosure relate to a surface acoustic wave resonator having a multi-layer substrate with heat dissipation. The multi-layer substrate includes a support substrate, a piezoelectric layer, and a thermally conductive layer configured to dissipate heat associated with the surface acoustic wave resonator. The thermally conductive layer is disposed between the support substrate and the piezoelectric layer. Related surface acoustic wave filters, radio frequency modules, and wireless communication devices are also disclosed.

Aspects of this disclosure relate to a surface acoustic wave resonator having a multi-layer substrate with heat dissipation. The multi-layer substrate includes a support substrate, a piezoelectric layer, and a thermally conductive layer configured to dissipate heat associated with the surface acoustic wave resonator. The thermally conductive layer is disposed between the support substrate and the piezoelectric layer. Related surface acoustic wave filters, radio frequency modules, and wireless communication devices are also disclosed.

A filter assembly is disclosed that includes a monolithic filter having a surface and a heat sink coupled to the surface of the monolithic filter. The heat sink includes a layer of thermally conductive material that can have a thickness greater than about 0.02 mm. The heat sink may provide electrical shielding for the monolithic filter. In some embodiments, the filter assembly may include an organic dielectric material, such as liquid crystalline polymer or polyphenyl ether. In some embodiments, the filter assembly may include an additional monolithic filter.

Aspects of this disclosure relate to a filter that includes an acoustic wave device with a multi-layer substrate with heat dissipation. The multi-layer substrate includes a support substrate (e.g., a quartz substrate), a piezoelectric layer, an interdigital transducer electrode on the piezoelectric layer, and a thermally conductive layer configured to dissipate heat associated with the acoustic wave device. The thermally conductive layer is disposed between the support substrate and the piezoelectric layer. The thermally conductive layer has a thickness that is greater than 10 nanometers and less than a thickness of the piezoelectric layer.

A method of constructing an RF filter comprises designing an RF filter that includes a plurality of resonant elements disposed, a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and a sub-band between the transmission zeroes. The non-resonant elements comprise a variable non-resonant element for selectively introducing a reflection zero within the stop band to create a pass band in the sub-band. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create a plurality of filter solutions, computing a performance parameter for each of the filter solutions, comparing the performance parameters to each other, selecting one of the filter solutions based on the comparison of the computed performance parameters, and constructing the RF filter using the selected filter solution.