Zenith Electronics Corporation

Zenith Radio Corporation

Lg Electronics Inc.

Pierre Dobrovolny

James J Wolford

Dominic J Nicoletto

A tuner includes an RF input with a signal level controller such as an attenuator that is provided to attenuate a signal from the RF input. A tunable RF filter provides RF band limiting and determines simultaneously the AGC bandwidth. An amplifier with resistive feedback provides first and second outputs which, together, represent the incident power of the attenuated signal delivered by the amplifier, thus eliminating the need for a directional coupler and rendering this part of the tuner compatible with integration. A feedback circuit responds to the incident power of the attenuated signal by controlling the attenuation (AGC) provided by the signal level controller.

Attenuation control for tuners

A doubly balanced upconverter mixer includes a local oscillator balun circuit comprising juxtaposed foil elements on opposite sides of an insulated substrate with electrical interconnections between the foil elements. An IF balun circuit also comprises series tuned and parallel tuned foil elements on opposite sides of the substrate in juxtaposition to each other. A diode switching network interconnects the baluns. A local oscillator signal is connected to the foil elements of the local oscillator balun circuit, an RF signal is coupled to one foil element of the IF balun circuit and an IF signal is taken from the other foil element of the IF balun circuit. Another embodiment incorporates MESFET type switches, the gates of which are supplied directly with a symmetrical local oscillator signal. This arrangement eliminates the need for the local oscillator balun.

Printed circuit doubly balanced mixer for upconverter

A single balanced downconverter includes an insulated substrate with a primary circuit and a secondary circuit, each consisting of an open annular foil element, located on opposite sides of the substrate in juxtaposition with each other and having mutual coupling. A pair of mixing diodes is connected across the ends of the secondary element, which has its center connected to ground. A 2 local oscillator signal is applied to the primary circuit. A 1 IF signal is applied to, and a 2 IF signal is developed from, the secondary circuit.

Printed single balanced downconverter mixer

An RF A/B switch associated with a receiver has first and second inputs and an output. A first diode circuit includes a plurality of diodes and an impedance network coupled between the first input and the output. A second diode circuit includes a plurality of diodes and an impedance network coupled between the second input and the output. A controller establishes a common series biasing current through at least one of the diodes in each of the first and second diode circuits. The common series biasing current biases one of the first and second diode circuits so as to configure a respective one of the impedance networks in a low pass filter configuration that couples a signal on one of the first and second inputs to the output, and the common series biasing current biases the other of the first and second diode circuits in a blocking configuration so as to block a signal on the other of the first and second inputs from the output.

RF A/B switch with substantial isolation

A switchable filter for passing one of a plurality of frequency bands has n bandpass filter sections coupled in parallel between a filter input terminal and a filter output terminal. Each of the n bandpass filter sections is arranged to pass a different frequency band. Each of n switches is coupled to a respective one of the n bandpass filter sections, and each of the n switches is operable in either an OFF state for activating a corresponding one of the n bandpass filter sections or an ON state for deactivating the corresponding one of the n bandpass filter sections. The n switches are arranged and controlled so that, when any one of then switches is operated to its off state, the remaining n&minus;1 switches are operated to their ON states and form a series circuit for conducting a common current.

Low power switchable filter tuner

Indoor UHF antennas for HDTV and ATSC television signals each include a reflector backplate from which is supported one or more dipoles. Both passive and active antennas are disclosed. The active antennas include: single amplifier with a single dipole; push-pull amplifier with a single dipole; two amplifiers with two parallel dipoles; and two push-pull amplifiers with crossed dipoles. The dipole plates comprise printed circuit boards with the amplifiers directly deposited on the obverse sides of the dipole plates.

Dipole UHF antenna

A combined VHF/UHF active antenna, suitable for indoor use, includes a common element that serves as a reflector for UHF signals and as a director for VHF signals. The VHF element is bent upon itself to permit its packaging as a consumer product accessory.

Combined UHF and VHF antenna

An indoor antenna for a UHF and higher frequency receiver has a plurality of polygon shaped conductive elements spaced apart from each other in a three dimensional arrangement. The signals from each pair of elements are combined through adjustable phase and attenuation networks and the combined signal is supplied to the input of a receiver that includes evaluation circuitry for optimizing the response of the antenna system when subjected to multipath conditions. A plurality of sets of random adjustment values are initially applied to the phase and attenuation networks and the antenna response over the signal band is monitored. The set of random values that exhibits the least deviation from the optimum antenna response over the received frequency band is used as the starting point for an optimization program for the calculation of further adjustments to the individual phase and attenuation networks to optimize the antenna response over the received signal band.

Adaptive indoor antenna system

A high definition television tuner includes a frequency compensated PI type PIN diode attenuator with the current through the series diode controlled separately from the current through the shunt diodes. A look-up table contains information that correlates the selected RF frequency and the desired AGC level with input data for two D/A converters. A microprocessor controls the D/A digital data, which is based upon information provided by a digital signal processing circuit. In one embodiment of the invention, the look-up table is connected between a D/A converter and a microprocessor and the microprocessor controls the look-up table for supplying the digital data to the D/A converters. In another embodiment, the microprocessor, after receiving the desired AGC level information, first interrogates the look-up table, then supplies the digital data to the D/A converter based.

Digital AGC control for high definition television tuner

A double conversion tuner includes a first filter that is relatively flat over a 6 MHz band at 920 MHz. A pair of series-parallel resonant circuits form notch filters that operate on the downconverted signals to economically produce a 6 MHz frequency response at 44 MHz that has excellent adjacent channel and other signal rejection.

Adjacent channel rejection in double conversion tuner

A selective RF circuit for a double conversion tuner includes three double tuned bandpass circuits, each of which is tunable over approximately one-third of the tuning range. Switching diodes are used at the input and the output of each of the bandpass sections for selectively activating one of the bandpass sections and deactivating the remaining ones in response to a bandswitching signal. Operational amplifiers or other devices supply the input and output switching diodes by providing a current sink for the active bandpass and current sources for the inactive bandpasses.

Selective RF circuit with varactor tuned bandpass switched bandpass

An oscillator operable in the gigaHertz range includes a transistor having an emitter coupled to a tank circuit and an additional feedback path coupling the tank circuit back to the base of the transistor. The inductive elements of the tank circuit are in printed foil form as is a transmission line that provides the additional feedback path. This arrangement improves the phase noise characteristics of the oscillator while extending its operating frequency range.

Oscillator for digital ATV signals having low phase noise

A high frequency partial transformer hybrid includes a first divided circular conductive element affixed to one side of an insulated substrate and a second split circular conductive element affixed to the other side of the substrate juxtaposed to the first element. Plated-through holes in the substrate interconnect pads on the first and second elements. Connection tabs on the elements are adapted to be connected to conductors on a printed circuit board when the substrate is orthogonally supported in a rectangular recess in the substrate. In a transformer hybrid embodiment, a third continuous circular conductive element is supported on an additional substrate in alignment with and insulated from the second element. The third element also includes connection tabs that are connectable to the conductors on the printed circuit board.

Printed circuit transformer hybrids for RF mixers

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.

Frequency compensated PIN diode attenuator

A selective RF circuit for a double conversion tuner includes three sections: low and mid band double tuned bandpass sections and a high band double tuned bandpass section. Each section includes tuning varactors and one or more coupling varactors. The varactors are operated in a first tuning mode for exhibiting a variable capacitance and in a second mode for presenting a substantial low impedance across their terminals. A microprocessor controlled circuit arrangement applies DC potentials to the tuning and coupling varactors and to two pairs of switching diodes simultaneously for selecting and tuning the desired bandpass section. The varactors in each bandpass section are complemented with fixed capacitors selected so that the product of the loaded Q and the coupling factor of any active double tuned bandpass filter is maintained substantially equal to unity over the entire tuning range.

Growing community of inventors

North Riverside, IL, United States of America

Pierre Dobrovolny