104 results about "If amplifier" patented technology

A tunable receiver is disclosed including a plurality of select filters to perform an initial band selection, a variable-gain low noise amplifier (LNA) whose gain is controlled to prevent its output power level to exceed a predetermined power threshold, a plurality of digitally-tunable tracking filters to pass signals within a selected channel and to reject signals in a corresponding image band, a second LNA to further amplify the received RF signal and to generate differential signal outputs, a down converting stage which converts the received RF signal to an IF signal while rejecting signals in the image band, an IF trap to further reject undesired signals present at the output of the down converting stage, an IF amplifier to amplify the IF signal to compensate for losses, an IF filter to provide channel select and reject undesirable signals, and a variable-gain IF amplifier to amplify the IF signal and maintain its power level within specification.

A tunable receiver is disclosed including a plurality of select filters to perform an initial band selection, a variable-gain low noise amplifier (LNA) whose gain is controlled to prevent its output power level to exceed a pre-determined power threshold, a plurality of digitally-tunable tracking filters to pass signals within a selected channel and to reject signals in a corresponding image band, a second LNA to further amplify the received RF signal and to generate differential signal outputs, a down converting stage which converts the received RF signal to an IF signal while rejecting signals in the image band, an IF trap to further reject undesired signals present at the output of the down converting stage, an IF amplifier to amplify the IF signal to compensate for losses, an IF filter to provide channel select and reject undesirable signals, and a variable-gain IF amplifier to amplify the IF signal and maintain its power level within specification.

A Class-E power amplifier includes a choke and a switch connected in series between a source of a supply voltage and circuit ground and connected to an inductively coupled coil. An output node of the amplifier is formed between choke and the switch and connected to a transmitter antenna. A shunt capacitor couples the amplifier's output node to the circuit ground. A feedback signal, indicating an intensity if the signal at the amplifier output node is used to vary the input signal to the Class-E power amplifier and thereby control operation of the switch.

An automatic gain controller (AGC) and method for use in a digital TV receiver having an IF amplifier, an RF amplifier, an analog to digital converter (ADC) connected to the IF amplifier, and a demodulator connected to the ADC, the AGC comprising: an input selector for selecting as feedback signal one of a digitized IF signal output of the ADC and a demodulated signal output of the demodulator; a signal detection unit for detecting the conditions of the feedback signal and outputting status signals; and a traffic controller for receiving the status signals and outputting control signals based on the status signals to an IF gain controller and an RF gain controller for independent gain control of the RF amplifier and the IF amplifier. The AGC and method further including hysteresis-curve-based switching for alternatively halting adjustments to IF gain while adjusting RF gain or halting adjustments to RF gain while adjusting IF gain.

AM receiver 20 is provided with antenna 1, RF amplifier 2, I / Q mixer 3, VCO 4, impulse noise detector 5, interpolator 6, BPF 7, IF amplifier 8 and AM detector 9. I / Q mixer 3 is composed of I mixer 11a as an in-phase mixer and Q mixer 11b as an orthogonal mixer. Impulse noise detector 5 generates an interpolation signal from in-phase and orthogonal output signals from I / Q mixer 3. Interpolator 6 carries out shaping of waveforms of the output signals from I / Q mixer 3 in response to the interpolation signal and eliminates impulse noises from the output signals from I / Q mixer 3.

In a radar, a frequency-modulated transmission signal whose frequency varies in time is generated. The gain-frequency characteristics of an IF signal which represents a beat signal between the transmission signal and a reception signal has its peak at or below one half of the sampling frequency of an AD converter. The gain-frequency characteristics of an IF amplifier circuit is determined so that the gain increases as the frequency increases at or below the frequency corresponding to the peak, the ratio of change in the gain relative to change in the frequency becomes smaller at short distances for which a saturation of a mixer is caused, and the gain is reduced at DC and in the vicinity of DC.

A chopper-stabilized amplifier (20A) includes an amplifier (3), an input chopper (2A) having a first input (4) receiving an input signal (VIN+), an output (5) coupled to a first input of the amplifier, and a feedback resistor (9) coupled to an output (6) of the amplifier to couple a feedback signal (VFB+) to a second input of the amplifier (3). The input chopper operates in response to a chopping clock (CHOP_CLK). If the amplifier (3) is unacceptably close to a saturation condition, the chopping clock (CHOP_CLK) is disabled to reduce input leakage current (ILEAKAGE) of the chopper-stabilized amplifier.

The RSSI circuit of the present invention includes: an IF amplifier section, which includes multiple stages of serially connected differential amplifiers for amplifying, with use of a current source IA provided as a power source for amplification, an IF signal corresponding to a received signal; an RSSI amplifier section for converting into current a voltage amplitude of an absolute value signal outputted from the differential amplifiers of the IF amplifier section, using a current source IB provided as a power source for conversion, and adding and outputting the converted current; and a current voltage conversion circuit for converting into voltage the output current from the RSSI amplifier section, and outputting the converted voltage as a measurement voltage value. The RSSI amplifier section is set so that a current value of the RSSI amplifier section is inversely proportional to absolute temperature. With the configuration, it is possible to realize an RSSI circuit, a received signal strength detection circuit and a wireless receiver, which are able to stabilize a strength measurement of a received signal relative to a change in temperature and to increase communication characteristics.

A television broadcast receiving apparatus has a demodulating unit including a PLL part synchronizing a phase of an IF signal with a phase of an internally generated carrier signal and outputting an out-of-synchronization flag signal when the IF signal and the carrier signal are in an unsynchronized state, and a muting part muting a sound intermediate frequency signal and outputting a noise signal of a predetermined level when the out-of-synchronization flag signal is outputted from the PLL part. Therefore, even when an IF amplifier of a tuning unit amplifies a noise at the maximum gain when there is no signal, an abnormal sound can be prevented from being outputted from a speaker of a decode and output unit.

Provided is an automatic gain controller for obtaining a high a signal-to-noise ratio (SNR), and for reducing power loss by controlling a gain until the gain reaches a maximum value, and a transmitting apparatus and method for use with a mobile communication terminal having the automatic gain controller. The automatic gain controller causes a variation of a gain at a radio frequency (RF) amplifier with respect to the variation of a control voltage to have a larger gradient than a variation of gain at an intermediate frequency (IF) amplifier with respect to the variation of the control voltage, and causes a total gain to have a decreasing gradient in accordance with the control voltage until the total gain reaches its maximum. Therefore, a high SNR can be obtained by adjusting the gain at the IF amplifier to be larger than the gain at the RF amplifier at a power of, for example, −13 dBm, to obtain improved adjacent channel power rejection (ACPR) characteristics at a high power, and to reduce power loss by controlling gain so that the total gain has a decreasing gradient in accordance with the control voltage until the total gain reaches its maximum.

In an embodiment, a receiver for processing a RF input signal having a variable signal strength includes an RF amplifier, an IF amplifier, and a controller. The RF amplifier is configured to receive and amplify the RF input signal. The IF amplifier is coupled to an output of the RF amplifier. The controller controls gains of the RF amplifier and the IF amplifier during times of falling signal strength. A gain of the IF amplifier is increased as the signal strength falls until a first amplitude threshold is reached for the falling signal strength. If the signal strength falls beyond the first threshold, a gain of the RF amplifier is increased until a second amplitude threshold is reached. The second amplitude threshold is lower than the first amplitude threshold. If the signal strength falls below the second amplitude threshold, the gain of the IF amplifier is further increased.