An RF front-end system is formed to include tunable frequency converters within the transmit and receive sections of each channel, allowing for conventional, limited-bandwidth wireless devices to transmit and receive a broad range of frequencies. Both the transmit and receive sections use superheterodyne frequency conversion to provide the translation between the limited frequency band associated with conventional wireless devices and wide frequency band (e.g., between about 100 MHz and 7000 MHz) approved for wireless communication. By virtue of using a local oscillator that can be widely tuned over the complete available frequency spectrum, the up-converted signals used for transmission can be expanded over this wider frequency selection.

A sensor interface circuit includes: an RF switch having a control node; a bias circuit electrically connected to the control node and applying, to the control node, a voltage at a first level or a second level corresponding to a linear region of a reflection characteristic; a first variable oscillation circuit electrically connectable to a first sensor; a second variable oscillation circuit electrically connectable to a second sensor; and a difference circuit electrically connected between the first variable oscillation circuit and the bias circuit, and between the second variable oscillation circuit and the bias circuit.

An electronic device may include wireless circuitry having mixer circuitry configured to receive oscillator signals from a partial-fractional phase-locked loop (PLL). The partial-fractional PLL may include a phase frequency detector, a charge pump, a loop filter, and a frequency divider connected in a loop. To implement the partial-fractional capability of the PLL, the frequency divider may receive a bitstream from a first order sigma delta modulator and a finite impulse response filter. The first order sigma delta modulator may output a periodic non-randomized output. The finite impulse response filter may increase the frequency of toggling of the periodic non-randomized output. Configured and operated in this way, the partial-fractional PLL can exhibit reduced phase noise.

A multiplier circuit includes a partial product generation circuit, a truncation circuit, and a summation circuit. The partial product generation circuit is configured to generate a plurality of partial products for multiplying two values. The truncation circuit is coupled to the partial product generation circuit. The truncation circuit is configured to shorten at least some of the partial products by removing a least significant bit from the at least some of the partial products. The summation circuit coupled to the truncation circuit. The summation circuit is configured to sum the truncated partial products produced by the truncation circuit.

A circuit comprising a differential transmission line and eight switches provides non-reciprocal signal flow. In some embodiments, the circuit can be driven by four local oscillator signals. The circuit can be used to form a gyrator. The circuit can be used to form a circulator. The circuit can be used to form three-port circulator than can provide direction signal flow between a transmitter and an antenna and from the antenna to a receiver. The three-port circulator can be used to implement a full duplex transceiver that uses a single antenna for transmitting and receiving.

A method for down-converting an RF signal is described that optically phase modulates an RF signal onto an optical carrier then applies an RF local oscillator (LO) phase modulation which down-converts the RF signal to an intermediate frequency after appropriate optical signal processing and optical-to-electrical photo-detection. The LO phase modulator is constructed such that a common hot electrode is shared among more than one optical mode, where an optical mode can be separate waveguides or optical wavelengths. The relative phase of the LO frequency applied to each optical mode can be different between the different optical modes. The resulting down-converted photo-detected signals of different LO-phase can be processed to reduce noise. A single LO phase modulator can down-convert multiple RF signals carried by multiple optical wavelengths, and a harmonic generation stage with multi-phase-matching peaks can be used to linearize each RF signal.

According to an embodiment of the inventive concept, an up-down converter includes a first mixer configured to convert an input radio frequency (RF) signal into an intermediate frequency (IF) signal using a first local signal; an IF filter configured to filter the IF signal converted by the first mixer; a second mixer configured to convert the IF signal, which has been filtered by the IF filter, into an output RF signal using a second local signal; and a local oscillator configured to control a frequency of the first local signal and the second local signal based on a frequency of the input RF signal.

A method for down-converting an RF signal is described that optically phase modulates an RF signal onto an optical carrier then applies an RF local oscillator (LO) phase modulation which down-converts the RF signal to an intermediate frequency after appropriate optical signal processing and optical-to-electrical photo-detection. The LO phase modulator is constructed such that a common hot electrode is shared among more than one optical mode, where an optical mode can be separate waveguides or optical wavelengths. The relative phase of the LO frequency applied to each optical mode can be different between the different optical modes. The resulting down-converted photo-detected signals of different LO-phase can be processed to reduce noise. A single LO phase modulator can down-convert multiple RF signals carried by multiple optical wavelengths, and a harmonic generation stage with multi-phase-matching peaks can be used to linearize each RF signal.

A wide range differential current switching circuit can operate across a wide range of input currents and across a broad range of frequencies. A first differential current source can include a first transistor and a second transistor. The first transistor receives a switching signal and provides an output current and at output node. The second transistor receives an inverted switching signal, the first transistor and the second transistor coupled to each other at a tail node. A current source provides an input current to the tail node. A third transistor can provide a boost current to the tail node while the first transistor is off.

A wide range differential current switching circuit can operate across a wide range of input currents and across a broad range of frequencies. A first differential current source can include a first transistor and a second transistor. The first transistor receives a switching signal and provides an output current and at output node. The second transistor receives an inverted switching signal, the first transistor and the second transistor coupled to each other at a tail node. A current source provides an input current to the tail node. A third transistor can provide a boost current to the tail node while the first transistor is off.