Abstract: A receiver for frequency modulated signals, having down-conversion to a baseband, zero intermediate frequency for selectivity, followed by up-conversion to a non-zero IF for amplification, limiting, and demodulation.A phase-lock loop locks the frequency of the down-conversion source to the center frequency of the signal coupled to the baseband IF, converting the signal to precisely zero frequency. This avoids the beat note often found in direct conversion systems. The phase-lock loop additionally provides inherent demodulation of the FM signal.The received FM signal is coupled to the baseband IF through a radio frequency amplifier for improved sensitivity and local oscillator isolation, or through a first IF comprising a mixer, local oscillator, filter, and amplifier.

Abstract: This invention is a case designed to contain a miniature battery of a particular design in connection with a radio transmitter wherein the case provides for quick access through a friction fitting cover and specially designed battery holding elements which permit removal and replacement of the special battery without the need of any tools or special training. The holding portion for the battery consists of two especially designed spring loaded case elements, one of which has a partial shelf to retain the battery.

Abstract: "Dispatch overdialing" permits radio transceivers already communicating via a repeater with other transceivers in a trunked radio communications system to call additional radio transceivers onto the communications channel in use. A radio transceiver in a first group may "dispatch overdial" another radio transceiver in a different group by transmitting a dispatch overdial begin signal to the repeater. The repeater mutes all audio communications on the channel, and the radio transceiver then transmits a sequence of identifying signals which are identical to those used to establish communications initially. The radio transceiver then transmits a further sequence of identifying signals which identify a further radio transceiver (or group of transceivers) to be called onto the channel. If the first sequence of identifying signals matches the signals which were used to establish communications initially, the repeater initiates handshake signalling to call the further transceiver(s) onto the channel.

Abstract: A unique housing (104 and 600) of a portable radio transceiver (100) is described that takes advantage of the heat sinking, electrical shielding and structural characteristics of a battery. The unique electronic circuitry housing (104 and 600) includes a battery as an integral structural element thereof. In one illustrated housing (104), a stick battery (210) is attached to the side of a transmitter printed circuit panel (213). A logic printed circuit panel (212) and a receiver printed circuit panel (214) are positioned above and below the transmitter printed circuit panel (213), respectively, and are held together by interlocking side rails (206,207). In a second illustrated housing (600), a flat battery (602) is attached to the sides of a first U-shaped printed circuit panel (604). A second U-shaped printed circuit panel (606) is positioned between the battery and the first panel (604). Heat dissipated by the electrical components on the second panel (606) is conducted away by the flat battery (602).

Abstract: A power limiter circuit for a radio frequency transceiver of the type having a single input-output antenna port is comprised of an isolator, first and second three port circulators and a pair of PIN diodes. One port of the first circulator is connected to the antenna port and one port of the second circulator is coupled to a transmit/receive antenna. The second ports of the two circulators are connected together through the isolator for passing signal from the transceiver to the antenna and the third ports of the two circulators are connected together for passing signal from the antenna to the transceiver. The PIN diodes, arranged in inverse parallel relationship, are connected between the third ports and circuit ground and operate in connunction with the isolator to limit to a safe value the signal passed from the antenna to the transceiver.

Abstract: A radio-frequency mixer and a local oscillator integrated into a single housing, and including a Gunn-type oscillator coupled to the mixer by a section of microstrip transmission line and a section of suspended stripline. A broadside coupler in the suspended stripline provides dc and intermediate-frequency isolation for the mixer, and a block of dielectric material on the microstrip provides improved temperature compensation for the diode oscillator. The entire compact assembly has good conversion loss performance over a relatively wide frequency band, and is relatively insensitive to temperature changes.

Abstract: A noise blanking signal generator for an AM radio receiver includes a product detector adapted to receive an IF signal modulated by an AF signal and synchronously detect the AF signal, a first low pass filter adapted to derive from the product detector a filtered voltage indicating the average IF signal strength, a second low pass filter adapted to derive from the product detector an AF signal voltage and a reference voltage generating circuit ratiometrically related to the product detector through a common DC power supply and effective to generate a reference voltage substantially equal to the filtered voltage in the absence of an IF signal.

Abstract: The present invention relates to a bootstrapping cross-polarization canceler which includes a noise-blanking limiter in the path before a correlation detector, and a processor which uses the output from the correlation detector to provide cross-polarization cancellation continuously or just during an outage condition where orthogonally received signals from a communication path include error rates which exceed a predetermined threshold. Alternatively, the processor can use the output of a pseudo error detection, which detects the error rate of the orthogonally received signals, when the error rates in the received signals are below the predetermined threshold in order to achieve convergence and cross-polarization cancellation in the canceler during a non-outage period.

Abstract: An interference wave detection circuit is designed so as to detect whether a beat due to the difference between two carrier wave frequencies is included or not in a received signal for a radio receiver. The detection circuit comprises circuitry for deriving a first binary signal corresponding to a level of a signal of voice frequency band obtained by demodulating the received signal and for deriving a second binary signal corresponding to a level of an envelope signal of an intermediate frequency signal from the received signal to provide a predetermined time difference between the first and second binary signals.

Abstract: In a radio communication system, a transmitting section of a substation comprises a controlling circuit (21) for controlling a carrier frequency of a local oscillator (24) in response to a frequency deviation signal. A burst generating circuit (26) generates a burst in response to the input signal, a burst control signal, and a local oscillation signal of the carrier frequency. The transmitting section further comprises a holding circuit (34) responsive to a frequency control signal and the burst control signal. During presence of the burst control signal, the holding circuit holds the frequency control signal received before a beginning of the burst control signal to keep the carrier frequency of the local oscillation signal invariable until an end of the burst control signal. Otherwise, the frequency control signal passes through the holding circuit as it stands.

Abstract: A headset for communication with both FM and AM circuit signals comprising a first earphone for receiving only FM signals and a second earphone for receiving only AM signals and first and second switches associated with the headset and coupled to the FM and AM circuits for selectively transmitting a response to either of the received signals on a corresponding one of the FM and AM circuits.

Abstract: A compact police radar warning receiver is provided having an antenna in which all of the mixer and oscillator components are mounted to one side of the antenna enabling the exterior wall of the side opposite thereto to be constructed substantially flat and thereby function as one of the exterior walls of the housing. The antenna is further provided with an improved microwave oscillator, an impedance transformer and non-adjustably positioned tuning pins.

Abstract: A FM wireless headphone transmitter which uses a novel technique of varying the transmitted frequency. Instead of the traditional methods of using a variably meshing multi-plate capacitor, the invention uses a printed circuit inductance with a tuning plate attached permanently to the inside of the case so that frequencies are changes by changing cases. An alternative embodiment uses interchangeable tuning plates attached to the inside of the case by hook and loop pile type fastener material. The printed circuit inductance also serves as a transmitting antenna.

Abstract: The invention concerns a frequency modulation broadcasting transmitter in which the output oscillator at the transmission frequency is modulated not directly by the audiofrequency signal but through the intermediary of a phase locking loop comprising a phase comparator supplied, on the one hand, by the output signal filtered from a picture or image frequency rejection mixer. This mixer receives, on the one hand, a modulated intermediary frequency signal from a modulator and, on the other hand, the output signal of the oscillator at the transmitting frequency F.sub.S, the reference frequency F.sub.o1 being determined as a function of the central transmitting frequency and of the intermediary frequency F.sub.o1 =F.sub.S -F.sub.1.

Abstract: A demodulator of the type employed in a "zero-IF" system uses a local oscillator for providing quadrature output signals at the center frequency of a received signal to be demodulated. The demodulator has first and second mixers for separately mixing the received signal with the quadrature signals to provide a first and second output signal each in quadrature at the outputs of said mixers. These signals are low pass filtered. The demodulator includes third and fourth mixers with each mixer respectively receiving at an input one of the first and second low pass signals. At another input the mixers receive third and fourth signals. The third and fourth signals are derived from mixing a variable controlled oscillator (VCO) signal with local oscillator quadrature signals the frequency of said is independent of the center frequency of the received signal.

Abstract: A very stable master clock for satellites is disclosed. Time division multiple access techniques are used to permit individual earth stations to be received by the satellite in separate non-overlapping time slots. The satellite switched time division multiple access systems are compatible with the onboard satellite clock by providing a comparator control logic loop to produce a signal representing the phase difference between the onboard oscillator clock and the earth station. Control signals are generated to correct the voltage controlled oscillator onboard the satellite.

Abstract: A device for aligning the phase and amplitude of a quadrature-detected coent two-channel receiver utilizing a mixer in each channel comprising a circuit for providing a sweep frequency signal to each receiver channel; a circuit for detecting the envelopes of the receiver channels at the outputs of the mixers and determining the voltage difference between the envelopes; and a circuit for controlling the amplitude level in one of the receiver channels in accordance with this voltage difference. Simultaneously, the output signals from the two mixers are added with the resulting sum signal being envelope-detected, and also subtracted from each other with the resulting difference signal being envelope-detected. The sum envelope and the difference envelope are subtracted from each other to generate a control signal for controlling the phase of one of the mixer local oscillator signals to ensure that the mixer local oscillator signals are in phase quadrature.

Abstract: A radio receiver capable of receiving signals on at least two different frequencies at the same time is described. A hetrodyne frequency is selected midway between the frequencies and an intermediate frequency is selected at a frequency equal to one half of the difference of the frequencies to be received.