Rfstream Corporation

Ukom, Inc.

Takatsugu Kamata

Kimitake Utsunomiya

Kazunori Okui

Hiroshi Ogasawara

Keiichi Fujii

Christopher Li

A filter circuit topology for filtering a radio frequency input signal includes one or more inductor devices, such as, for example, discrete chip or air coils. The inductor devices are center tapped into a capacitor coupled to the ground. The center-tapped inductor configuration splits the output voltage across the inductor devices into two equal voltages of predetermined amplitude determined by the quality factor of the filter circuit. The filter circuit further includes an input capacitor to receive the RF input signal and an output capacitor coupled respectively to the inductor devices, the output capacitor having a variable capacitance, the inductor devices and the variable capacitor forming an inductive-capacitive (LC) filter capable of filtering the RF input signal and generating an output filtered signal for further transmission to a television tuner.

Radio frequency inductive-capacitive filter circuit topology

A tuner module comprising a tuner and a tuner enclosure. The tuner includes a substrate containing filter coils and the tuner enclosure includes at least one partition plate placed between filter coils of the tuner to improve the isolation between the filter coils. The substrate may also contain plated through holes placed beneath a partition plate which further improves isolation between the filter coils. In some embodiments, the substrate is comprised of a coil layer having a planar coil, a shield layer, and a dielectric layer. The dielectric layer is placed between the coil and shield layers and provides a distance between the two layers to achieve a particular quality factor level of the planar coil. In some embodiments, the tuner enclosure further includes a shielding case that extends to the base of the substrate, is comprised of a metal material, and is mechanically connected with the substrate.

Enclosure and substrate structure for a tuner module

A current source generates a constant current using metal oxide semiconductor (MOS) transistors. A biasing circuit generates a biasing current based on the transconductance of the MOS transistors. A load circuit, comprising a resistor coupled in parallel with a MOS transistor, generates a constant load current from the biasing current. The load current comprises the sum of a resistor current, which flows through the resistor, and a MOS current that flows through the transistor. The load current is constant because variations of the resistor current offset variations of the MOS current across temperature or process variations. A current mirror circuit generates an output current for the current source equal to a sum of the resistor current and the MOS current, the output current being approximately constant in value across temperature or process variations.

MOSFET temperature compensation current source

A television tuner is fully implemented on a monolithic integrated circuit. The television tuner includes a baseband SAWF function fully integrated in silicon. The SAWF function includes trap and bandpass filters. A video demodulation circuit includes an I, Q demodulation and a post Nyquist filter.

Quadratic video demodulation with baseband nyquist filter

A monolithic integrated circuit includes a tuner and a SAW filter function. The tuner receives a radio frequency (RF) television signal that has a range of fundamental frequencies from 55 mega hertz (Mhz) to 880 Mhz. The tuner down converts the RF television signal to an intermediate frequency (IF) television signal that has a low fundamental frequency. In one embodiment, the SAWF filter performs the SAW filter function on the IF television signal. In another embodiment, the SAWF filter performs the SAW filter function at baseband. An IF processor for processing the IF television signal to generate a video television signal and an audio television signal is disclosed.

Methods and apparatus for implementing a receiver on a monolithic integrated circuit

A television demodulator circuit, for use in a television receiver, generates baseband video and audio outputs from a television signal, such as an intermediate frequency television signal. The I, Q demodulator circuit mixes the television signal with an in-phase ('I') local oscillator signal and a quadrature phase ('Q') local oscillator signal at the tuned frequency to generate baseband I and Q signals. The baseband I and Q signals are input to low pass filters and a Nyquist slope filter. The Nyquist slope filter generates, for the baseband I and Q signals, a Nyquist slope response and attenuates channels adjacent to the tuned television channel. The Nyquist slope filter comprises a transfer function with at least two zero crossings, so as to provide a notch filter response for attenuation of a television channel adjacent to the tuned television channel. For example, the transfer function may have three zero crossings to attenuate a sound carrier frequency, a color carrier frequency, and a picture frequency for the television channel adjacent to the tuned television channel. The transfer function, expressed in the S domain, comprises an all-pass fractional transfer function with a real number in the numerator and a complex number in the denominator. A television receiver that incorporates the I, Q demodulator circuit is disclosed.

Quadratic nyquist slope filter

A discrete inductive-capacitive (LC) filter selects between at least two inductor banks to tune the LC filter. The filter receives an input signal that includes one or more bands of frequencies. A control signal selects a band of frequencies for processing. A first inductor bank is selected to filter a first band of frequencies, and a second inductor bank is selected to filter a second band of frequencies. A switch circuit couples the input signal to either the first inductor bank or the second inductor bank. The switch circuit selects the first inductor bank if the first band of frequencies is selected, and selects the second inductor bank if the second band of frequencies is selected. The switch circuit electrically isolates the switching of the input signal to the first and the second inductor banks, so as to enhance the Q factor of the LC filter. Circuit and techniques are disclosed to reduce parasitic capacitance in a capacitive bank that employs MOS transistors. Furthermore, circuits and techniques are disclosed to tune a coupling factor on an inductive bank based on the frequency of the input signal.

Discrete inductor bank and LC filter

An image rejection quadratic filter is tunable to filter image frequencies over a wide band. In one embodiment, the image rejection filter includes in-phase and quadrature phase mixers. The image rejection has a fractional transfer function. The image rejection filter has two sub-circuits, wherein the first sub-circuit produces the imaginary component of the transfer function, and the second sub-circuit produces the real component of the transfer function. The first sub-circuit receives the Q signal, and the second sub-circuit receives the I signal. In one embodiment, to create the fractional transfer function, a multi-feedback looped integrator is used.

Image rejection quadratic filter

An inductive ('L')-capacitive ('C') filter bank has application for use in a television receiver. The LC filter includes inductors configured in at least one inductive (&#x201c;L&#x201d;) bank, and capacitors configured in at least one capacitive (&#x201c;C&#x201d;) bank. The inductors and capacitors are selectively enabled so as to configure an LC filter with at least one inductor from the L bank and at least one capacitor from the C bank. A combination of inductors and capacitors are selected through the semiconductor switches so as to maximize a Q factor for the LC filter.

Frequency discrete LC filter bank

Methods and apparatus for an improved discrete LC filter

A receiver, such as a television receiver, tunes an inductive (&ldquo;L&rdquo;) and capacitive (&ldquo;C&rdquo;) filter based on a desired frequency. The LC filter includes a plurality of inductors, configured in at least one inductive (&ldquo;L&rdquo;) bank, and a plurality of capacitors configured in at least one capacitive (&ldquo;C&rdquo;) bank. The inductors are selectively enabled for the LC filter by an N code, and the capacitors are selectively enabled for the LC filter by an M code. The receiver uses a functional comparator to compare offset, capacitive, inductive and frequency values to tune the LC filter. Techniques for tuning the LC filter for operation in the VHF and UHF bands are disclosed.

Growing community of inventors

Santa Clara, CA, United States of America

Takatsugu Kamata