Motorola Corporation

Frank Robert Skutta

David S Peckham

Scott David Beutler

Robert M Johnson, Jr

Thomas R Klaus

Michael S Cruz

Constantine Vlahos

Lee Don Tice

Curt Hufford

David Z Ding

A multiple frequency band receiver (,) receives at least two frequency bands that are close but not adjacent. A first bandpass filter (,) passes signals in the first frequency band. A second bandpass filter (,) passes signals in the second frequency band. The first and second filters each attenuate signals between the first and second frequency band to at least a first level so as to provide selectivity in the frequency range between the first and second frequencies to prevent the signals between these frequency bands from being further processed by the communication device. A third filter (,) coupled to first and second filters passes signals in both the first and second frequency band and attenuates signals above the pass band of the higher of the first and second filters and below the lower of the first and second filters.

Multiple frequency band receiver

A unique apparatus for coupling radio frequency (RF) signals from a wireless communication device (200) to an external device by way of an I/O port (116). In particular, a connector having three adjacent contact elements (238) couples signals to an external device wherein the first and third contact elements (239, 241) are electrically coupled to a ground plane (302) and wherein the second or middle contact element (240) is electrically coupled to a conductive RF signal path (344). The ground plane and the conductive path (334) are preferably on a printed circuit (pc) board which is preferably a three layer board with the conductive path (334) located between two ground planes (302, 352). The connector is substantially covered with a shield (230) coupled by legs (248) to the ground plane (302) at apertures (332). A mating connector (400) also includes a shield (430) which is commonly grounded. The mating connector preferably includes an internally located coaxial connector (412) and cable (414) to minimize loss of RF communication signals. Components of the connectors (116, 400) are selectively grounded to eliminate RF interference and establish a reliable RF ground reference to a pc board (300) of the wireless communication device and the coaxial connector. The connectors also include latching members (405) and apertures (250) for firm coupling therebetween.

Apparatus for coupling RF signals

A multiple band mixer (204) includes at least one transistor element (313, 324, 400). A single local oscillator provides a signal to one terminal of the at least one transistor element. The communication signals for each frequency band is input to the at least one transistor element at another terminal. A third terminal of the at least one transistor element is connected to the output.

Multiple band mixer with common local oscillator

A method and apparatus enables a communication device (100) to operate in multiple bands, such as GSM 900 MHz, DCS 1800 MHz, and DCS 1900 MHz bands, by eliminating the need for a mixer for each band. In a dual band GSM/DCS 1800 radiotelephone, for example, the local oscillator (LO) injection frequencies for both GSM and DCS bands are provided to a mixer (234) through the use of combination filters (222, 246). Thus, the duplexing and matching requirements to the mixer input are simplified and the signal losses are minimized. The common output ports of the GSM RX/LO combination filter and DCS RX/LO combination filter are duplexed to the input of the mixer. Also, the input impedance matching of the mixer is designed to match the impedance for the received signals in each band, as well as provide an RF trap at the IF frequency. The match at the output of the mixer is designed to match the impedance of the IF filter and provides a low impedance to RF input frequencies. Finally, a tri-band radiotelephone is also described.

Method and apparatus for receiving communication signals

A synthesizer radio frequency (RF) signal receiver (FIG. 1) for single sideband radios is described that can eliminate interference due to internally generated spurious signals, commonly referred to as 'whistler spurs'. The unique receiver includes first and second mixers (102 and 106), which are intercoupled by a 75 mHz crystal filter (104) having a 20 kHz passband, and which are each coupled to signals from voltage controlled oscillators (120 and 140). The first IF frequency provided by the first mixer (102) varies about 75 mHz, and the second IF frequency provided by the second mixer (106) is fixed at 11.4 mHz. The second mixer (106) is coupled to 11.4 mHz stages (108) which have a 2.7 kHz passband. The 11.4 mHz stages (108) are followed by another mixer (110) and audio stages (112) for demodulating audio signals from the received RF signal, which are then applied to a speaker (114). The frequency of the VCO (120) coupled to the first mixer (102) can be varied by changing the divisor N of a programmable divider (123), and the frequency of the VCO (140) coupled to the second mixer (106) likewise can be varied by changing the divisor M of a programmable divider (133). When interference due to a whistler spur is present, activation of an IF pushbutton (160) enables a microcomputer (170), which changes divisors N and M for varying the frequencies of the two VCO's (120 and 140) by a multiple of 3.2 kHz, which in turn shifts the first IF frequency by 3.2 kHz. The frequency change also shifts the whistler spur outside of the 2.7 kHz passband of the 11.4 mHz stages (108) and greatly attenuates it. If the whistler spur is not sufficiently attenuated, the IF pushbutton (160) can be activated a second time.

Method and apparatus for eliminating interference due to spurious

Improved noise reducing circuitry for high frequency signal sideband (SSB) receivers is described that substantially eliminates interference caused by impulse noise from a noise source 160. The SSB receiver includes first and second mixers 102 and 106 intercoupled by a crystal filter 104 having a passband that is approximately the same as the noise bandwidth of the antenna circuitry 100 when the SSB receiver is tuned to the lower frequency in its frequency band. A second intermediate frequency (IF) signal from second mixer 106 is coupled to an IF amplifier 122 and a noise amplifier 126. An envelope decector 128 is coupled to the output of noise amplifier 126 and provides an output signal having a magnitude proportional to the envelope of the noise amplifier output. Automatic gain control circuitry 132 is coupled to the output of the envelope detector for generating a gain control signal that reduces the gain of noise amplifier 126 as the magnitude of the envelope detector output increases. An impulse detector 130 is also coupled to the envelope detector output for detecting the presence of impulse noise and generating mute control signal pulses when impulse noise is detected. The mute control signal pulses are coupled to an attenuator 124 which attenuates the output of IF amplifier 122 so that the impulse noise does not create audible interference in the speaker 154 of the SSB receiver.

Noise reducing circuitry for single sideband receivers

A plurality of series inductors and shunt capacitors are provided between a radio transmitter and an antenna. The inductors and capacitors are arranged in binary increments and are inserted in, or withdrawn from the circuit via provided reed relays. A microprocessor activates the relays in one of several modes until the required degree of match is provided. The status of the relays is stored in provided memory such that upon tuning of the transmitter to the same channel a proper match condition can be established without resort to the matching program.

Method for automatically matching a radio frequency transmitter to an

The improved gain control circuit is comprised of an amplifier, a semiconductor device attenuator at the amplifier input, and unique control circuitry for controlling the attenuation factor of the semiconductor device. The amplifier is designed for low phase shift to minimize the time delay of its transfer function. The control circuitry responds to both positive and negative a.c. signal transitions at the amplifier output to initiate attenuator gain reduction. As with the amplifier, the control circuitry is designed for minimum response time. The combination results in an extremely fast a.g.c. attack time.

Fast attack automatic gain control circuit

An audio derived AGC signal for controlling RF and/or IF amplifiers in the radio receiver wherein a first control signal is developed by a circuit having a relatively slow response time when the audio output signal is below a predetermined value and a second control signal is developed by a circuit having a relatively fast response time when the audio output signal is at or above the predetermined value. The control signals are developed across a storage capacitor and a circuit is connected thereto for quickly discharging the capacitor when no signal is being supplied from the audio circuit.

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Palatine, IL, United States of America

Frank Robert Skutta