A radio frequency signal synthesizer circuit includes a digital to analog converter configured to generate an analog output signal for each clock cycle of a clock signal to provide the radio frequency signal and a controlled oscillator to generate the clock signal. The controlled oscillator is configured to vary a cycle time of the clock signal for a radio frequency signal in a first frequency range in a first operation mode or to maintain a constant cycle time for a radio frequency signal in a second frequency range in a second operation mode, the second frequency range being different than the first frequency range.

The disclosure relates to technology for an apparatus having a current conveyer comprising a first stage having a first differential input, and a second stage having a second differential input. The first and second stages are configured to operate in a push-pull mode to provide an output signal at a current conveyer output between the first stage and the second stage. The apparatus has a first frequency mixer configured to generate a first mixer signal based on an input signal and an oscillator signal having a first frequency. The first frequency mixer is configured to provide the first mixer signal to the first differential input. The apparatus has a second frequency mixer configured to generate a second mixer signal based on the input signal and a second oscillator signal having the first frequency. The second frequency mixer is configured to provide the second mixer signal to the second differential input.

A transmitter/receiver (1) up-converts, using an LO signal as a local oscillation signal, an IF signal having a predetermined frequency band, thereby generating a transmission signal RF.sub.TX. Moreover, the transmitter/receiver (1) generates a (LO+IF).sup.2 signal and a (LO−IF).sup.2 signal based on the IF signal and the LO signal. Using the LO signal obtained by adding-up of the (LO+IF).sup.2 signal and the (LO−IF).sup.2 signal, a reception signal RF.sub.RX is down-converted. Thus, a local oscillation signal generation unit of a receiving unit is not necessary.

A direct digital synthesis transmitter that uses a programmable digital circuit to generate a digital signal representing at least one radio frequency signal, the generated signal is filtered, amplified by an amplifier, and provided to a transmission antenna without upconversion. The transmitter generating the digital signal at a desired output frequency range such that a frequency upconverter is not needed to produce signals in the desired radio frequency range.

In a communication system of the LPWAN type including a server and a plurality of gateways intended to make wireless communications with terminals in said communication system, the server: obtains a description of a mobility hierarchy in which mobility types are hierarchically defined; obtains a description of a mobility tree in which mobility areas are hierarchically defined, in conformity with the mobility hierarchy; obtains terrain measurements associated with each mobility area defined in the mobility tree; establishes a frequency plan on the basis of the mobility tree and terrain measurements; and configures the gateways and the terminals according to the frequency plan established.

A method and transmission system for amplifying and providing navigation signals. The system comprises a splitter circuit configured to receive a plurality of radio frequency (RF) signals oscillating at at least two different frequencies f.sub.1 and f.sub.2. The splitter circuit is further configured to split and forward the RF signals having the f.sub.1 frequency to a first bandpass filter and the RF signals having the f.sub.2 frequency to a second bandpass filter. The system further comprises a first tunable amplifier configured to receive the RF signals from the first bandpass filter. The system further comprises a second tunable amplifier configured to receive the RF signals from the second bandpass filter at substantially the same time as the first tunable amplifier's receipt of the RF signals from the first bandpass filter. The first tunable amplifier is further configured to amplify its RF signals across a first band centered around the frequency f.sub.1. The second tunable amplifier is further configured to amplify its RF signals across a second band centered around the frequency f.sub.2. The amplified RF signals are fed substantially concurrently into a mixer circuit for transmission via an RF antenna to a navigation receiver.

A method includes producing a plurality of TX LO signals by a first LO generator comprising a first frequency doubler and a first frequency divider, the first frequency doubler configured to receive a VCO signal having a first frequency and generate a first signal fed into the first frequency divider, the first signal having a second frequency that is twice the first frequency, producing a plurality of MRX LO signals by a second LO generator comprising a second frequency doubler and a second frequency divider, the second frequency doubler configured to receive the VCO signal and generate a second signal fed into the second frequency divider, the second signal having the second frequency, configuring the TX to operate at a first LO frequency equal to the second frequency, and configuring the MRX to operate at a second LO frequency equal to the first frequency through disabling the second frequency doubler.

A transmitter/receiver (1) up-converts, using an LO signal as a local oscillation signal, an IF signal having a predetermined frequency band, thereby generating a transmission signal RF.sub.TX. Moreover, the transmitter/receiver (1) generates a (LO+IF).sup.2 signal and a (LO−IF).sup.2 signal based on the IF signal and the LO signal. Using the LO signal obtained by adding-up of the (LO+IF).sup.2 signal and the (LO−IF).sup.2 signal, a reception signal RF.sub.RX is down-converted. Thus, a local oscillation signal generation unit of a receiving unit is not necessary.

The disclosure relates to technology for an apparatus having a current conveyer comprising a first stage having a first differential input, and a second stage having a second differential input. The first and second stages are configured to operate in a push-pull mode to provide an output signal at a current conveyer output between the first stage and the second stage. The apparatus has a first frequency mixer configured to generate a first mixer signal based on an input signal and an oscillator signal having a first frequency. The first frequency mixer is configured to provide the first mixer signal to the first differential input. The apparatus has a second frequency mixer configured to generate a second mixer signal based on the input signal and a second oscillator signal having the first frequency. The second frequency mixer is configured to provide the second mixer signal to the second differential input.

A direct digital synthesis transmitter that uses a programmable digital circuit to generate a digital signal representing at least one radio frequency signal, the generated signal is filtered, amplified by an amplifier, and provided to a transmission antenna without upconversion. The transmitter generating the digital signal at a desired output frequency range such that a frequency upconverter is not needed to produce signals in the desired radio frequency range.