A radio frequency system, a method for controlling antenna switching, and related products are provided. The radio frequency system supports a simultaneous downlink reception with four antennas and includes m antennas, a radio frequency processing circuit, and a radio frequency transceiver coupled with the radio frequency processing circuit. The m antennas are divided into at least two antenna groups, where m is greater than or equal to 4 and less than or equal to 8. The radio frequency processing circuit is coupled with the at least two antenna groups and includes modules which are the same in number as the at least two antenna groups. Each module is coupled with one antenna group and is disposed adjacent to the antenna group with which the module is coupled. The modules include at least one transmitting module, or at least one transmitting module and at least one receiving module.

Circuits and methods for improving the noise figure (NF) of an amplifier, particularly an LNA, in high-gain modes while improving the IIP3 of the amplifier in low-gain modes. The source of an amplifier common-source FET is coupled to circuit ground thorough a degeneration circuit comprising a two-port inductor and a bypass switch coupled in parallel with the inductor. A switched feedback circuit is coupled between the gate of the common-source FET and a feedback node in the amplifier output signal path. During a low gain mode, the inductor is entirely bypassed and the enabled feedback circuit lowers the input impedance of the common-source FET and reduces the gain of the amplifier circuit, essentially eliminating the need for a degeneration inductor. During a high gain mode, the source of the common-source FET is coupled to circuit ground through the inductor and the feedback circuit is disabled. Other gain modes are supported.

A front end module (FEM) for a 5.6/6.6 GHz Wi-Fi acoustic wave resonator RF filter circuit. The device can include a power amplifier (PA), a 5.6/6.6 GHz resonator, and a diversity switch. The device can further include a low noise amplifier (LNA). The PA is electrically coupled to an input node and can be configured to a DC power detector or an RF power detector. The resonator can be configured between the PA and the diversity switch, or between the diversity switch and an antenna. The LNA may be configured to the diversity switch or be electrically isolated from the switch. Another 5.6/6.6 GHZ resonator may be configured between the diversity switch and the LNA. In a specific example, this device integrates a 5.6/6.6 GHz PA, a 5.6/6.6 GHZ bulk acoustic wave (BAW) RF filter, a single pole two throw (SP2T) switch, and a bypassable LNA into a single device.

A variable gain low noise amplifier (LNA) and a method for controlling a gain of the variable gain LNA are provided. The variable gain LNA may include a first transistor, a first degeneration inductor, a second transistor and a second degeneration inductor, wherein the first degeneration inductor is coupled to a source terminal of the first transistor, and the second degeneration inductor is coupled to a source terminal of the second transistor. Gate terminals of the first transistor and the second transistor are configured to receive an input signal. The first transistor and the first degeneration inductor belong to a first branch of the variable gain LNA, and the second transistor and the second degeneration inductor belong to a second branch of the variable gain LNA. More particularly, a gain of the variable gain LNA is determined by controlling whether to turn off the second branch.

A high-frequency circuit includes an amplifier, a power distributor disposed on an output route of the amplifier, a first by-pass route that bypasses the amplifier, a second by-pass route that bypasses the power distributor, a first switch and a second switch disposed in series on the first by-pass route, and a third switch disposed in series on the second by-pass route. The first by-pass route is connected to a first node on a route connecting a signal input terminal and the amplifier and a second node on a route connecting the amplifier and the power distributor. The second by-pass route is connected to a third node between the first switch and the second switch and a fourth node on an output route of the power distributor.

Methods and devices to minimize or reduce phase discontinuity between different gain modes (including bypass, active and passive modes) with reduced increase in circuit size (footprint or number of components) and complexity, without impacting other performance parameters, are disclosed. Phase shifter elements that can be disposed in both the active and passive bypass paths are also described. Moreover, devices using the same reconfigurable phase shifter elements in both active and bypass modes are described. Components of the phase shifters can also perform output matching when the phase shifters are implemented as part of an RF receiver front-end.

Disclosed is an apparatus comprising means for transmitting a first signal via at least a first switch, a first amplifier, a second switch and a power amplifier, wherein an output of the second switch is connected to a power amplifier path comprising at least the power amplifier, while transmitting the first signal. An input of the first switch and the output of the second switch are switched to switch between transmitting and receiving. A second signal is received via at least the first switch, the first amplifier and the second switch, wherein the output of the second switch is disconnected from the power amplifier path while receiving the second signal.

A radio frequency (RF) summer circuit having a characteristic impedance Z.sub.0 comprises first and second ports coupled by first and second resistances, respectively, to a junction. The circuit further comprises a series combination of a third resistance and a switch movable between open and closed positions and an amplifier having input and output terminals and operable in an off state and an on state wherein the series combination is coupled across the input and output terminals of the amplifier between the junction and a third port. The first resistance, second resistance, and the third resistance are all substantially equal to Z.sub.0/3. Further, when the switch is moved to the closed position and the amplifier is switched to the off state a passive mode of operation is implemented and when the switch is moved to the open position and the amplifier is switched to the on state an active mode of operation is implemented. The RF summer circuit develops a summed signal at the third port equal to a sum of signals at the first and second ports modified by one of first and second gain values.

A bias circuit for a low noise amplifier of a front end interface of a radio frequency communication device including a bias generator providing a bias voltage on a bias node for the low noise amplifier, a first resistive device coupled between the bias node and an input of the low noise amplifier, a first switch coupled in parallel with the first resistive device, and mode control circuitry receiving a mode signal indicative of a mode change, in which the mode control circuitry, in response to a mode change, momentarily activates the first switch to bypass the first resistive device and momentarily increases current capacity of the bias generator. The mode control circuitry may also momentarily activate a second switch to bypass a second resistive device of the bias circuit. The mode control circuitry may increase a sink current of the bias generator in response to the mode change.

A clamping circuit that may be used to provide efficient and effective voltage clamping in an RF front end. The clamping circuit comprises two series coupled signal path switches and a bypass switch coupled in parallel with the series coupled signal path switches. A diode is coupled from a point between the series coupled signal path switches to a reference potential. In addition, an output selection switch within an RF front end has integrated voltage clamping to more effectively clamp the output voltage from the RF front end. Additional output clamping circuits can be used at various places along a direct gain signal path, along an attenuated gain path and along a bypass path.