An active limiting system that is suitable to protect a low noise amplifier against the high power signals received from a signal input includes, at least one first switch, source of which is connected to a gate voltage; at least first resistor which is connected between the gate and source of the first switch; at least one second resistor, which is connected between a drain voltage and drain of the first switch; at least one second switch, source of which is connected to said drain voltage and drain of which is connected to a signal input; at least one third resistor which is connected between the drain of the first switch and gate of the second switch; at least one first filtering element, which blocks DC currents/voltages and which is connected between the source of the second switch and ground.

A radio frequency (RF) limiter, and systems and methods thereof, to limit power of received high-power RF signals over a very broad bandwidth (e.g., approximately 17 octaves) using a single-channel solution. The limiter can be comprised of a coarse section and a fine section. The coarse section can include a first capacitor configured to receive a first RF signal; the rectifier, which is coupled to an output of the first capacitor; a transmission medium coupled to the output of the first capacitor and the rectifier; a plurality of PIN diodes each having a relatively thick I-region coupled between a second capacitor and the transmission medium; and a coupling mechanism configured to provide electrical coupling between the transmission medium and the rectifier. The rectifier can include a first inductor and a second inductor connected in series, and a Schottky diode coupled to the second inductor and the coupling mechanism.

A radio frequency (RF) limiter, and systems and methods thereof, to limit power of received high-power RF signals over a very broad bandwidth (e.g., approximately 17 octaves) using a single-channel solution. The limiter can be comprised of a coarse section and a fine section. The coarse section can include a first capacitor configured to receive a first RF signal; the rectifier, which is coupled to an output of the first capacitor; a transmission medium coupled to the output of the first capacitor and the rectifier; a plurality of PIN diodes each having a relatively thick I-region coupled between a second capacitor and the transmission medium; and a coupling mechanism configured to provide electrical coupling between the transmission medium and the rectifier. The rectifier can include a first inductor and a second inductor connected in series, and a Schottky diode coupled to the second inductor and the coupling mechanism.

A semiconductor device capable of measuring a minute current is provided. The semiconductor device includes an operational amplifier and a diode element. An inverting input terminal of the operational amplifier and an input terminal of the diode element are electrically connected to a first terminal to which current is input, and an output terminal of the operational amplifier and an output terminal of the diode element are electrically connected to a second terminal from which voltage is output. A diode-connected transistor that includes a metal oxide in a channel formation region is used as the diode element. Since the off-state current of the transistor is extremely low, a minute current can flow between the first terminal and the second terminal. Thus, when voltage is output from the second terminal, a minute current that flows through the first terminal can be estimated from the voltage.

A distributed amplifier system constituted of: an input transmission line exhibit a plurality of sections; an output transmission line; an amplifier stage, an output of the amplifier stage coupled to the output transmission line and an input of the amplifier stage coupled to the input transmission line between a respective pair of the plurality of sections; a PIN diode coupled between a first end of the input transmission line and a common potential; and a circuitry coupled between a second end of the input transmission line and the common potential, the second end opposing the first end, such that there is a direct current (DC) flow through the first unidirectional electronic valve, the input transmission line and the circuitry.

Methods and devices for limiting the power level of low noise amplifiers (LNA) implemented in radio frequency (RF) receiver front-ends. The described methods are applicable to bypass, low and high gain modes of the LNA. According to the described methods, the decoder allows the signal to be clamped before or after being attenuated. The benefit of such methods is to improve large signal performances (e.g. IIP3, P1dB) of the RF receiver front-end, while still meeting the clamping requirements, or improve (lower) clamped output power, while still meeting large signal performances (e.g. IIP3, P1dB).

A fast response time, self-activating, adjustable threshold limiter including a limiting element LE, a first coupling element CE.sub.1 electrically connected from a signal node of LE to a control input of LE, and a second coupling element CE.sub.2 electrically connected from the control input of LE to a nominal node of LE. An initial bias (control) voltage is also supplied to the control input of LE to dynamically control the limiting threshold for the limiter. Embodiments include usage of self-activating adjustable power limiters in combination with series switch components in a switch circuit in lieu of conventional shunt switches.

A two-stage high-power RF limiter circuit for an RF signal receiver incorporates a heavy limiting stage to limit high energy pulses of a received RF signal to a desired power threshold over a sustained time period, while a light limiting stage reacts quickly to high energy pulses to reduce spike leakage associated with the slower reaction time of the heavy limiting stage. Both heavy and light limiting stages incorporate PIN diodes biased to a voltage just below the desired power threshold (the light limiter biased to a slightly higher voltage than the heavy limiter) so the PIN diodes do not activate until power levels are high enough to warrant limiting. The holdoff voltage across the PIN diodes is maintained by Zener diodes biased to a voltage corresponding to the power threshold, allowing the PIN diodes to self-bias once the power threshold is reached.

A two-stage high-power RF limiter circuit for an RF signal receiver incorporates a heavy limiting stage to limit high energy pulses of a received RF signal to a desired power threshold over a sustained time period, while a light limiting stage reacts quickly to high energy pulses to reduce spike leakage associated with the slower reaction time of the heavy limiting stage. Both heavy and light limiting stages incorporate PIN diodes biased to a voltage just below the desired power threshold (the light limiter biased to a slightly higher voltage than the heavy limiter) so the PIN diodes do not activate until power levels are high enough to warrant limiting. The holdoff voltage across the PIN diodes is maintained by Zener diodes biased to a voltage corresponding to the power threshold, allowing the PIN diodes to self-bias once the power threshold is reached.

In a portable radio transceiver, a power amplifier system includes a saturation detector that detects power amplifier saturation in response to duty cycle of the amplifier transistor collector voltage waveform. The saturation detection output signal can be used by a power control circuit to back off or reduce the amplification level of the power amplifier to avoid power amplifier control loop saturation.