Abstract: A band edge amplitude reduction system changes the filtering characteristics of a receiver based on the amplitude of signal(s) adjacent to an edge of the operating band of the receiver and/or of signals not under the power control of the receiver. For example, the receiver measures the power level over a bandwidth at the band edges of the operating band of the receiver. If the signals adjacent to the operating band are strong enough relative to the signal power within the operating band, overload protection circuitry changes the filtering characteristics of the receiver to improve the attenuation of the signal(s) from the adjacent band(s). In certain embodiments, the overload protection circuitry switches in filter(s) with a narrower bandwidth to attenuate the signal(s) from adjacent band(s) at the edge(s) of the operating band of the receiver, thereby preventing interference with or the overload of the receiver by signals from outside the operating band and/or not under the power control of the receiver.

Abstract: A tunable bandpass filter is provided that comprises a first shunt-connected ferroelectric (FE) tunable tank circuit having a first node to accept an input signal. A second shunt-connected FE tunable tank circuit has a second node to supply a bandpass filtered signal. A first capacitor is connected in series between the first and second nodes. In one aspect, the first tank circuit comprises a first resonator connected to the first node, and a fourth capacitor connected between the first resonator and a reference voltage. The fourth capacitor is a tunable FE capacitor. Typically, a fifth capacitor is connected between the first node and the reference voltage. Likewise, the second tank circuit comprises a second resonator connected to the second node, and a sixth (FE) capacitor connected between the second resonator and the reference voltage. A seventh capacitor is connected between the second node and the reference voltage.

Abstract: The band pass filter includes at least first and second band pass filters. A selector receives at least one signal, and supplies the signal to one of the first and second band pass filters. A controller controls the selector based on a frequency of the signal.

Abstract: The invention relates to a method for tuning a filter (5). The filter has at least one variable time constant, by which the location of the pass band (pc) of said at least one filter can be changed. In the method, at least one reference signal is inputted in said filter (5), and the frequency of said at least one reference signal is changed, and/or said at least one time constant of the filter (5) is changed. The method also comprises the steps of measuring the strength of the output signal of the filter (5) and determining, on the basis of the measurement on the strength of the output signal of the filter (5), the location of the pass band of said filter (5).

Abstract: The present invention is a method and apparatus for optimizing performance of a transceiver selecting and processing an intermediate frequency free of significant interference, such as noise. A frequency band may be scanned to detect interference upon which an intermediate frequency free of significant interference may be selected. This may enhance performance of the receiver by reducing the effects of noise. Additionally, perrformance may be further optimized by adjusting the passband of the filter such that the center of the passband matches the selected intermediate frequency. This may provide stability as centering of the passband may account for process, voltage and temperature variations and errors. Further, performance may be enhanced by ensuring desirable signal attributes are passed through the filter.

Abstract: The present invention is to provide a microwave filter distributed on a circuit board of a wireless communication product, which comprises an input terminal, a resonant chamber of double frequencies, and an output terminal of the microwave filter directly distributed on the circuit board of the wireless communication product as a plurality of microstrips by utilizing a manufacturing technique of printed circuit board for eliminating the harmonic spurious of double frequencies and higher frequency caused by nonlinear distortion of a power amplifier of the wireless communication product.

Abstract: A multiple-section bandpass filter for broadcast communications includes adjacent waveguide segments with a perpendicular connecting segment between them to form a U-shaped signal path. The waveguide cavities of the segments may be extruded and rectangular in cross section, and have a groundplane spacing that allows signal propagation between filter sections by evanescent coupling. Resonators in each of the adjacent segments have a separation that establishes the coupling bandwidths without the need for passive decoupling structures. A cross coupling conductor between the adjacent segments provides a capacitive or inductive coupling between them. A decoupling structure may be located in the connecting segment.

Abstract: A direct conversion satellite tuner is fully integrated on a common substrate. The integrated tuner receives an RF signal having a plurality of channels and down-converts a selected channel directly to baseband for further processing. The integrated tuner includes on-chip local oscillator generation, tunable baseband filters, and DC Offset cancellation. The integrated tuner can be implemented in a completely differential I/Q configuration for improved electrical performance. The entire direct conversion satellite tuner can be fabricated on a single semiconductor substrate using standard CMOS processing, with minimal off-chip components. The tuner configuration described herein is not limited to processing TV signals, and can be utilized to down-convert other RF signals to an IF frequency or baseband.

Abstract: A semiconductor device for demodulating a received signal in a satisfactory manner when the frequency of the received signal deviates. The semiconductor device is used in a receiver having a reference oscillator. The semiconductor device includes a local oscillator, a PLL controller, and a comparator. The local oscillator generates a local signal having a local frequency. The PLL controller controls the local frequency in accordance with a reference signal of the reference oscillator. The comparator compares the frequency of the received signal with the frequency of the reference signal or the phase of the received signal with the phase of the reference signal to generate an error signal for correcting the local frequency in accordance with the comparison.

Abstract: A transceiver system is described herein that has an antenna coupled to a filter unit which is coupled to multiple radio base stations (RBSs). Each RBS uses one TX/RX cable and if needed a RX cable to connect to the filter unit. To enable the RBSs so they can share one antenna, each RBS has a duplex filter incorporated therein. And, the filter unit has a unique combination of diplex filter(s), duplex filter(s), part-band duplex filter(s), diplex-duplex filter(s), splitter(s) and/or low noise amplifier(s). Four exemplary embodiments of the transceiver system are described herein to show how the filter unit can be configured so as to enable the RBSs to share one antenna even if the RBSs share the same frequency band and/or even if the RBSs operate with different radio standards (e.g., TDMA, CDMA, WCDMA and GSM). Also described herein in accordance with the present invention are: (1) a method for constructing the transceiver system; (2) a radio base station; and (3) an antenna.

Abstract: The use of wideband or software defined radio is attractive in terms of cost reduction since it allows re-use of base stations for different transmission modes. However, wideband radio also introduces the problem of how to deal with high level interfering signals. Presently, such signals saturate parts of the receive circuit—typically the ADC. By detecting interference and determining its frequency, it is possible to tune a bandpass or bandpass with notch filter, to take the interfering signal out of the reception band of the receiver thereby taking the ADC out of saturation whilst retaining the ability to resolve low level signals.

Abstract: First and second transmission paths P1 and P2 are disposed between a first port #1 connected to an antenna ANT and a second port #2 connected to a transceiving circuit 10. The first transmission path P1 includes receiving filters Rx1, Rx2, and Rx2?, an amplification circuit LNA, and 90° hybrid circuits 12 and 14. The second transmission path P2 includes a transmitting filter Tx1. A received signal amplified by the amplification circuit LNA is transmitted to the port #2 via the 90° hybrid circuits 12 and 14, but is not transmitted to the second transmission path P2. A transmission signal is transmitted from the port #2 to the second transmission path P2. This prevents oscillation of the received signal due to positive feedback.

Abstract: The velocity of a wireless communications device (106) is estimated. In response to this estimate, a filter bandwidth, such as a pilot filter (310) bandwidth, is adjusted so that the introduction of noise and distortion to a signal received by the device is mitigated. The filter bandwidth is adjusted by increasing it as the estimated velocity increases; and decreasing it as the estimated velocity decreases. Such adjustments may be accomplished through providing a number of predetermined bandwidths that each correspond to a particular velocity range, and setting the filter bandwidth to the predetermined bandwidth that corresponds to the estimated velocity.

Abstract: A receiver circuit that includes a direct conversion receiver that receives a modulated signal, and generates an in-phase differential signal and a quadrature-phase differential signal. The receiver circuit includes an in-phase branch that processes the in-phase differential signal, and a quadrature-phase branch that processes the quadrature-phase differential signal. Each branch includes an amplifier and a summer. The amplifier is configured to receive and amplify the respective in-phase or quadrature-phase differential signal. The summer receives the resulting amplified differential signal and sums the signals to generate a single signal. A log amplifier receives the summed in-phase and quadrature-phase signal, and generates an RSSI signal that is proportional to the log of the difference between the two summed signals. The data may then be extracted based on the amplitude of the RSSI signal.

Abstract: A front end module for wireless network system is disclosed. The front end module includes a transmitting/receiving switch, a bandpass filter, a balun, a lowpass filter, and a power amplifier. The front end module is characterized in that the bandpass filter, the balun and the lowpass filter are formed inside a plurality of low-temperature-cofired-ceramic (LTCC) substrates by a patterning process while the transmitting/receiving switch, and the power amplifier are formed on a surface layer of the LTCC substrates by the surface mounting technology (SMT).

Abstract: An electronic tuner of the present invention is arranged such that between an input part of the amplifying circuit and the ground serially connected are a coil and a diode, and a capacitor is connected between the ground and a connecting part between the coil and the diode. The diode is brought into conduction when a voltage supplied from a VHF High control source is at High level, and the coil and input capacitance of the amplifying circuit makes up a gain correction circuit for improving a frequency characteristic of a received signal in a VHF High band. The diode is brought out of conduction when a voltage supplied from a VHF High control source is at Low level, and the coil and the capacitor makes up a trap circuit for improving a frequency characteristic of a received signal in a VHF Low band. This makes it possible to minimize price increase of the apparatus and to improve frequency characteristics in the VHF High band and VHF Low band.

Abstract: A low-noise filter for a wireless receiver is disclosed. The low-noise filter comprises an amplifier and a filter comprising a frequency dependent negative resistance implemented using a general impedance converter to realize a bi-quad filter. The low-noise filter is implemented such that noise generated by the filter when an in-band signal is processed is prevented from appearing at the output of the amplifier stage.

Abstract: A method and apparatus for determining the data rate of a reverse link communication of an access terminal includes receiving a reverse activity bit (RAB) from an access point in the communication system, and passing the RAB to a digital filter to produce a filtered RAB. In one embodiment, the reverse link data rate is determined based on the filtered value of the RAB. Furthermore, a processor in the access terminal may determine whether the access terminal is in an idle mode, and passing a non-busy state value of the RAB to the digital filter when the access terminal is in the idle mode. The filtered RAB may be compared to a threshold to determine a mode of reverse link data rate determination. The mode defines a set of criteria for an aggressiveness level of increasing or decreasing the reverse link communication data rate. The processor, therefore, determines the data rate based on the filtered reverse activity bit in accordance with the determined mode.

Abstract: A RF transceiver for AMPS communication includes: a baseband processor for generating a transmission intermediate frequency signal and processing a reception intermediate frequency signal; a local oscillator for generating a local oscillation signal in transmission and reception; an up-mixer for combining the transmission intermediate frequency signal with the local frequency signal; a duplexer for processing a radio frequency signal received through an antenna; and a specific frequency removing unit installed between the local oscillator and an up-mixer to remove a specific frequency signal generated from the local oscillator. A filter is installed between the local oscillator and the up-mixer to remove the 2-times frequency of the local oscillation signal of 957.66 MHz, thereby removing the self-quieting phenomenon generated in the channel 76 of AMPS.

Abstract: The thermal interference due to the self heating of transistors constituting a gilbert cell circuit is reduced, thereby largely improving the receiving sensitivity to signals. A mixer circuit composed of a gilbert cell circuit comprises transistors T1 to T6. Each of the transistors T1 to T4 is con figured so that four transistors may be connected in parallel. In a layout on a semiconductor chip, four transistors T1a to T1d and T2a to T2d respectively constituting the transistors T1 and T2 are respectively separated into two pairs, and the respective two pairs are laid out in a crisscross shape so that they are crossed with each other. Similarly, four transistors T3a to T3d and T4a to T4d respectively constituting the transistors T3 and T4 are respectively separated into two pairs, and the respective two pairs are laid out in a crisscross shape so that they are crossed with each other. Thus, the thermal influence applied on the transistors T1 to T4 is uniformed.

Abstract: A radio has a tunable bandpass filter that is tuned by apparatus within the radio. A reference generator generates a reference signal for use in tuning the tunable bandpass filter. The tunable bandpass filter receives the reference signal and provides a filter output signal. A digital signal processing and control processor is connected to the tunable bandpass filter to receive the filter output signal. The digital signal processing and control processor has a phase comparison function that provides a phase error metric from the filter output signal. The digital signal processing and control processor tunes the tunable bandpass filter to provide a desired phase error metric signal thereby tuning the tunable bandpass filter to the desired center frequency. The digital signal processing and control processor stores tunable filter parameters for the desired center frequency. The tuning process may be repeated for several desired center frequencies of the tunable bandpass filter.

Abstract: The cutoff frequency is set high in order to prevent suppression of low-frequency components so that high-quality reception control of a radio signal can be realized. A radio signal amplifier unit amplifies a received radio signal and results in an amplified signal. A frequency conversion unit mixes the amplified signal with a local oscillation signal to thereby convert the radio signal having a radio frequency signal into the radio signal having an intermediate frequency signal, resulting in an intermediate frequency signal. A frequency shift control unit shifts the intermediate frequency signal towards the upper part of the frequency band. A frequency inversion unit inverts a low-frequency side of the intermediate frequency signal towards the upper part of the frequency band and inverts a high-frequency side thereof towards a lower part thereof. An AC coupling unit is provided at an output side of the frequency control unit.

Abstract: When changeover switch (26) selects the output of L band filter (23), changeover switch (28) is turned off and mixer (29) is operated as an amplifier such that the oscillation frequency of local oscillator (31) is controlled based on data fed to data terminal (37) and a channel selection can be performed in mixer (32). When changeover switch (26) selects the output of V band filter (25), changeover switch (28) is turned on and a channel selection is performed based on data fed to data terminal (37) in mixer (29). With this arrangement, the need for a tuning filter is eliminated and a broadband tuner not requiring manpower for adjustments can be provided.

Abstract: A communication device includes a noise flattening filter having a filter response that dynamically adjusts based on the current noise spectrum in a wireless channel. The noise spectrum of the wireless channel is estimated and used to determine a noise classification for the channel. A noise flattening filter response is then selected based upon the noise classification for use in filtering signals received from the channel. The filtered signals are then delivered to an equalizer for further processing.

Abstract: An RF device includes a first substrate having a lower relative dielectric constant, a first RF circuit for a lower frequency band provided in the first substrate, a second substrate having a higher relative dielectric constant larger than the lower relative dielectric constant, and a second RF circuit for a higher frequency band having a part of the second RF circuit sandwiched between the first substrate and the second substrate. The first RF circuit and the second RF circuit are connected to each other and the second substrate is partially overlaid on the first substrate. A semiconductor device or passive device is provided on a region in the surface of the first substrate on which the second substrate is not overlaid, and a multilayered wiring pattern made of copper or silver is formed in the first substrate to form the first RF circuit.

Abstract: An FM signal receiver for use in receiving a burst signals as in a Bluetooth system includes a BPF and a frequency-demodulation circuit, each having, for example, a phase shifter, which is constructed from similar or related circuitry so as to enable adjustment of the frequency characteristics of the BPF and frequency-demodulation circuit through an identical control signal. A short-circuit switch is disposed linking the input and output terminals of an amplifier. A control circuit opens the switch in a receiving operation and closes the switch in an adjusting operation. Thus, adjustment is carried out without using the amplifier. Therefore, an amplifier offset does not affect the frequency-to-voltage conversion by the frequency-demodulation circuit in the adjusting of the frequency-demodulation circuit and similar adjusting of the BPF. Thus, the BPF is prevented from being incorrectly adjusted due to the offset. The BPF characteristics are suitably adjusted.

Abstract: A filter circuit (10) is formed on a semiconductor substrate (11) formed with a trench (40) that is lined with a dielectric layer (38). A conductive material (37) is disposed in the trench and coupled to a node (62) to provide a capacitance that modifies a frequency response of an input signal (VIN) to produce a filtered signal (VOUT). An electrostatic discharge device includes an inductor (74) coupled to back to back diodes (17, 18) formed in the substrate to avalanche when a voltage on the node reaches a predetermined magnitude.

Abstract: A nano-electromechanical filter. The filter includes, on a substrate, at least one microtip extended by a beam-shaped nanostructure. The microtip and the nanostructure are at least superficially conductive. The nanostructure forms a resonator. At least one input electrode and at least one output electrode are formed on an insulating layer, on both sides of the axis of the microtip, in the vicinity of the apex of the microtip. The input electrode receives a signal to be filtered and the output electrode provides a filtered signal. The filter can be particularly applied to wireless communications.

Abstract: An unconditionally stable on-chip filter includes a filtering section and at least one negative resistance module. The filtering section is operably coupled to filter a signal and includes realizable integrated circuit passive components. The at least one negative resistance module is operably coupled to compensate for integrated circuit losses of the filtering section. The realizable integrated circuit passive components have values that are robust, in comparison to parasitic values, have minimal integrated circuit real estate, and provide realizable values for various integrated circuit manufacturing processes including CMOS technology.

Abstract: The invention relates to an anti-demodulator circuit which is fundamentally built up in the same way as a demodulator circuit but, instead of a bandpass filter as generally used in a demodulator, comprises a notch filter which receives an input signal comprising a useful signal and an interference signal, and generates a filtered signal. The notch filter has a center frequency which approximately corresponds to the frequency of the input signal so as to suppress at least a part of the useful signal. The anti-demodulator circuit further comprises a mixer circuit which receives the filtered signal and a phase-shifted input signal and supplies a demodulated output signal which substantially corresponds to the interference signal.

Abstract: An automatic tuning scheme for two active band-pass filters where both filters operate on the signal while simultaneously being tuned using a reference signal. To allow that the amplitude of a reference signal is made small and since both filters demonstrate a good linearity the build-up of the inter-modulation distortion does not occur. The first band-pass filter is tuned with the reference falling into its pass-band. The second band-pass filter is also tuned with the reference placed into its pass-band. The reference is practically eliminated by the virtue of the complexity of the second band-pass filter. Assuming the filter passes the signal for positive frequencies if the reference is made a negative frequency by appropriate 90 degrees phase shifting it will be attenuated by at least 55 dB, which is a sufficient signal-to-reference ratio.

Abstract: An automatic tuning scheme for two active band-pass filters where both filters operate on the signal while simultaneously being tuned using a reference signal. To allow that the amplitude of a reference signal is made small and since both filters demonstrate a good linearity the build-up of the inter-modulation distortion does not occur. The first band-pass filter is tuned with the reference falling into its pass-band. The second band-pass filter is also tuned with the reference placed into its pass-band. The reference is practically eliminated by the virtue of the complexity of the second band-pass filter. Assuming the filter passes the signal for positive frequencies if the reference is made a negative frequency by appropriate 90 degrees phase shifting it will be attenuated by at least 55 dB, which is a sufficient signal-to-reference ratio.

Abstract: Remotely controllable actuators are provided to alter the cavity size of bandpass cavity filters to alter the bandpass characteristics. In one embodiment, a stepper motor is used to provide lateral movement of a tuning plate to alter the size of the cavity. The neck of the cavity is also changed in length through the use of a tuning motor. A feedback loop is used to provide fine tuning of the length of the neck in response to changes due to temperature and vibration to offer maximum propagation of the signal to be transmitted. A coupling tuner is used to adjust to the resulting change in Q to the cavity. A tuning processor is used to receive signals from a remote location identifying the desired characteristics of the filter.

Abstract: A low pass filter (LPF) can realizes a sophisticated transmission filter usable in a dual-band application. The transmission filter features a compact size, a low cost, a lower insertion loss, and an excellent harmonics-suppression characteristic. In the LPF, a high pass filter (HPF) section working in a high frequency band or a band pass filter (BPF) section, is coupled with a first LPF section in parallel between an input terminal and an output terminal. The HPF section or the BPF section includes a switch circuit formed of one diode that switches the pass band thereof to a rejection band. When a signal supposed to pass through the first LPF section is input to the input terminal, the switch circuit is activated to change the HPF or the BPF section to the rejection band for blocking a second harmonics component from passing through the HPF or the BPF section.

Abstract: A programmable band-pass filter in a radio-frequency receiver. The band-pass filter has a bandwidth substantially covering a channel bandwidth. Once the appropriate channel in use is determined, the frequency band of the band-width filter is set to correspond to it.

Abstract: A multi-band antenna switch circuit including a diplexer connected to an antenna terminal for demultiplexing signals of different passing bands, a first and a second switch circuit for switching a high frequency signal and a low frequency signal demultiplexed by the diplexer to a plurality of transmission/reception terminals, a first and a second low pass filter connected to a transmission path between the diplexer and the transmission terminal or between the first and the second switch circuit and the transmission terminal, and a notch filter provided between the diplexer and the first switch circuit or between the diplexer and the second switch circuit.

Abstract: A filter arrangement includes one first resonator circuit connected between a first node and a second node. A second resonator circuit is connected between a third node and a fourth node. The first resonator circuit and the second resonator circuit are intercoupled. Further, an inductive device is provided, connected between the first node and the third node.

Abstract: A switchable high frequency bandpass filter includes an input node and an output node, a switchable LC resonator, and a switch signal input interface circuit. The switchable LC resonator is coupled between the input node and the output node for providing a plurality of high frequency signals having different frequencies with a plurality of switchable filter transfer functions. The switch signal input interface circuit is coupled to the switchable LC resonator. A switch signal is supplied to the switchable LC resonator through the switch signal input interface circuit for controlling the switchable LC resonator to provide the plurality of high frequency signals having different frequencies with a suitable one of the plurality of switchable filter transfer functions, respectively.

Abstract: A system and method are provided for reducing the current consumption of receivers such as direct conversion receivers associated with modem receiver systems as well as low IF receiver systems, among others. The system and method dramatically reduce the current consumption in receivers due to three factors. 1) Since the filter 302 also performs the VGA function, the current consumption of the VGA 304 is eliminated; 2) Since the gain partitioning of the structure 200 depicted in FIG. 2 is superior, the noise performance of the filter 302 is greatly reduced; and the base band LNA 304 can be eliminated, also eliminating the current consumption of the base band LNA 304; and 3) The folded gm structure 500 depicted in FIG. 5 can be used, cutting the current consumption of the base band filter 302 by a factor of two. The structure 200 notably does require control circuitry to set the gm values of the forward and feedback paths independently.

Abstract: A wireless receiver for receiving a specific wireless signal. The wireless receiver comprises an antenna, a bandpass filter, a offset device, and a control device. The antenna receives a first wireless signal. The bandpass filter has a resonance frequency, for retrieving the specific wireless signal from the first wireless signal. The specific wireless signal cannot be retrieved if the resonance frequency deviates. The offset device is coupled to the bandpass filter, for offsetting a deviation of the resonance frequency. The control device drives the offset device when the specific wireless signal is not detected by the bandpass filter. A transmission system utilizing the wireless receiver is also disclosed.

Abstract: A radio frequency switching apparatus wherein a filter for a transmitter module passes a transmission frequency to an antenna in a transmission mode and isolates the antenna and the transmitter module from each other in a reception mode. The radio frequency switching apparatus comprises a filter connected between the transmitter module and the antenna for passing a transmitted signal from the transmitter module to the antenna in the transmission mode. The filter also acts to cut off a reception frequency in the reception mode. The switching apparatus further comprises a first switching device for isolating the transmitter module and the antenna from each other in the reception mode, and a second switching device for isolating the antenna and a receiver module from each other in the transmission mode. No separate 1/4 wavelength strip line is required, making the circuitry of the switching apparatus simpler and, thus, the size thereof smaller.

Abstract: The present invention pertains to a frequency-lock filtering receiver and the method for the same. The receiver enters a tuning mode before receiving signals. A frequency synthesizer then generates the radio frequency (RF) to be received and adjusts the central frequency of a tunable filter through feedback control so as to lock in the RF to be received. Afterwards, the receiver enters a receiving mode to receive RF signals using an antenna and uses the central frequency of the tunable filter locked in the tuning mode to filter the RF signals and to receive signals.

Abstract: A frequency down-converter (18) for a receiver (10) in a wireless telecommunications system. The down-converter (18) is capable of simultaneously processing a plurality of signal channels without increased signal distortion over a relatively wide bandwidth. The frequency down-converter (18) employs a suitable mixer (28), bandpass filter (32), attenuator (34) and transformer (36) that are tuned to provide the desired frequency down-conversion and amplitude control over the desired wideband width. In one embodiment, the bandpass filter passes a frequency band at 25 MHz or above. The frequency down-converter (18) generates the IF signal in a single step down-conversion process, or generates the IF signal and then a baseband signal in a two step down-conversion process.

Abstract: An electronic circuit includes a frequency conversion device (4), an oscillator (6), a band-pass filter (8), and a controller (14). The oscillator (6) is connected to the frequency conversion device (4), and the frequency conversion device (4) is connected to the band-pass filter (8). The frequency conversion device (4) is arranged to receive a first signal (S1) at a frequency (ft), and to transform the first signal (S1) into an intermediate frequency signal (S2) at an intermediate frequency (fi) by applying a selection frequency (floc) from the oscillator (6). The band-pass filter (8) is arranged to receive the intermediate signal (S2) and to perform a band-pass filtering at a centre frequency (fbpf) and with a bandwidth (fw), the centre frequency (fbpf) being equal to the intermediate frequency (fi) at a predetermined working temperature of the band-pass filter (8).

Abstract: A ladder SAW (surface acoustic wave) filter which includes a first SAW resonator disposed in a parallel arm and a second SAW resonator disposed in a series arm, has an inductor connected parallel to at least one of the first SAW resonator and the second SAW resonator. The frequency of a resonance point or an anti-resonance point of the at least one of the first SAW resonator and the second SAW resonator is adjusted by changing the inductance value of the inductor.

Abstract: An RF receiver includes first and second RF filter stages and an amplifier stage. An output terminal of the first RF filter stage is coupled to an input terminal of the amplifier stage, and an output terminal of the amplifier stage is coupled to an input terminal of the second RF filter stage. The first and second RF filter stages are not identical, inasmuch as, for instance, the first and second RF filter stages may provide different selectivities. The first RF filter stage may include a low loss RF filter to establish a low noise figure for the RF receiver. The isolation provided by the amplifier stage permits the first and second RF filter stages to include high-order RF filters or, alternatively, multiple low order RF filters.

Abstract: An electronic tuner of the present invention is arranged such that between an input part of the amplifying circuit and the ground serially connected are a coil and a diode, and a capacitor is connected between the ground and a connecting part between the coil and the diode. The diode is brought into conduction when a voltage supplied from a VHF High control source is at High level, and the coil and input capacitance of the amplifying circuit makes up a gain correction circuit for improving a frequency characteristic of a received signal in a VHF High band. The diode is brought out of conduction when a voltage supplied from a VHF High control source is at Low level, and the coil and the capacitor makes up a trap circuit for improving a frequency characteristic of a received signal in a VHF Low band. This makes it possible to minimize price increase of the apparatus and to improve frequency characteristics in the VHF High band and VHF Low band.

Abstract: Electronic circuit including a frequency conversion device (4), an oscillator (6), a band-pass filter (8), and a controller (14), the oscillator (6) connected to the frequency conversion device (4), the frequency conversion device (4) connected to the band-pass filter (8),

Abstract: A pass band flatness correction circuit for improving flatness of a ripple occurring within a pass band in a band pass filter and a mobile telecommunication repeater system is provided. The pass band flatness correction circuit includes a complementary band pass filter having a pass band transfer characteristic producing a counter-ripple of a reverse shape to a ripple in a pass band of a main band pass filter, for flattening a total of pass band transfer characteristics of a filtering system, an amplifier circuit for enhancing an increase in a filter insertion loss, and an attenuator circuit for enhancing a reflection loss characteristic of the whole circuit. The flatness and a stop band attenuation characteristic of the band pass filter whose pass band flatness is distorted and a repeater system employing the band pass filter is enhanced, to thereby improve performance and speech quality of a mobile telecommunication service.

Abstract: The band pass filter includes at least first and second band pass filters. A selector receives at least one signal, and supplies the signal to one of the first and second band pass filters. A controller controls the selector based on a frequency of the signal.