Method and system for an intermediate frequency (IF) channel select filter with an integrated alternate adjacent channel interference (AACI) filter

An alternate adjacent channel interference (AACI) filter is integrated into an intermediate frequency (IF) channel select filter to filter received RF signals. The IF channel select filter is an IF staged structure comprising successive IF stages. Each of the successive IF stages is a 2-biquad integrator. The AACI filter is integrated into the first IF stage of the IF channel select filter by re-using circuit components such as an operational amplifier, an input resistor, and a shunt capacitor of the first IF stage. The shunt capacitor is coupled between a middle point of the input resistor and ground. The AACI filter is realized via different equivalent implementations of the re-used circuit components of the first IF stage. A value of the shunt capacitor of the AACI filter becomes a fixed-value when a value the input resistor is inversely proportional to the bandwidth of the AACI filter.

Not applicable.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to communication systems. More specifically, certain embodiments of the invention relate to a method and system for an intermediate frequency (IF) channel select filter with an integrated alternate adjacent channel interference (AACI) filter.

BACKGROUND OF THE INVENTION

A wireless transmitter transmits wireless signals via a wireless medium and a wireless communication device comprising a receiver is operable to receive and recover the transmitted wireless signals from the wireless medium. The manner in which the wireless signals are communicated via the wireless medium is dependent upon, for example, the wireless communication standard, or standards, being supported by the wireless communication devices. For example, IEEE 802.11a defines an orthogonal frequency division multiplexing (OFDM) wireless transmission protocol that includes eight 20 MHz spaced channels in the lower band (e.g., 5.15 gigahertz to 5.35 gigahertz) and four 30 MHz spaced channels in the upper band (e.g., 5.725 gigahertz to 5.825 gigahertz). Typically, during a wireless transmission, data is carried over a desired channel to a target receiver. A target receiver may be operable to tune one or more intermediate frequency (IF) stages so that a desired channel is centered within the filter response of the target receiver. As such, the desired channel is received and converted to a baseband signal, which is subsequently decoded to obtain the transmitted data.

BRIEF SUMMARY OF THE INVENTION

A method and/or system for an intermediate frequency (IF) channel select filter with an integrated alternate adjacent channel interference (AACI) filter, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and system for an intermediate frequency (IF) channel select filter with an integrated alternate adjacent channel interference (AACI) filter. In accordance with various embodiments of the invention, an alternate adjacent channel interference (AACI) filter may be integrated into an intermediate frequency (IF) channel select filter. The IF channel select filter together with the integrated AACI filter may be operable to filter a received RF signal. The IF channel select filter may comprise successive IF stages. Each of the successive IF stages of the IF channel select filter may be implemented as a 2-biquad integrator. The AACI filter may be integrated into the first IF stage of the IF channel select filter. The integrated AACI filter may be operable to re-use circuit components of the first IF stage to form a first order RC filter. The circuit components that are used for AACI may comprise an operational amplifier, an input resistor, and a shunt capacitor. The AACI filter may be realized via shunting a capacitor between a middle point of the input resistor and ground. A value of the shunt capacitor of the AACI filter becomes a fixed-value when a value the input resistor is set so that it is inversely proportional to the bandwidth of the AACI filter.

FIG. 1is a block diagram of an exemplary communication device that utilizes an intermediate frequency (IF) channel select filter with an integrated AACI filter in a radio frequency (RF) receiver, in accordance with an embodiment of the invention. The communication device180may comprise an antenna182, a radio frequency (RF) transmitter and/or receiver (Tx/Rx)184, a processor188, a memory190, a DSP192, a display183, user controls185, a speaker187, and a microphone189.

The antenna182may be suitable for transmitting and/or receiving electromagnetic signals. Although a single antenna is illustrated, the invention is not so limited. In this regard, the RF Tx/Rx184may utilize a common antenna for transmission and reception of signals adhering to one or more wireless standards, may utilize different antennas for each supported wireless standard, and/or may utilize a plurality of antennas for each supported wireless standard.

The RF Tx/Rx184may comprise suitable logic circuitry and/or code that may be operable to transmit and/or receive data utilizing one or more wired, wireless, and/or optical standards. In various exemplary embodiments of the invention, the RF Tx/Rx184may be operable to communicate in adherence with cellular, WiMAX, Wi-Fi, Bluetooth, Zigbee, T1/E1, Ethernet, USB, IEEE 1394, analog audio standards, analog video standards, digital audio standards, and/or digital video standards. The RF Tx/Rx184may be operable to perform amplification, down-conversion, filtering, demodulation, and analog to digital conversion of received signals. The radio frequency transceiver184may be operable to perform amplification, up-conversion, filtering, modulation, and digital to analog conversion of signals to be transmitted.

The processor188may comprise suitable logic, circuitry, and/or code that may enable processing of data and/or controlling of operations of the communication device180. In this regard, the processor188may be enabled to provide control signals to the various other portions comprising the communication device180. The processor188may also control transfers of data between various portions of the communication device180. Additionally, the processor188may enable execution of applications programs and/or code for processing data and effectuating operation of the communication device180.

The memory190may comprise suitable logic, circuitry, and/or code that may enable storage or programming of information comprising parameters and/or code that may effectuate the operation of the communication device180. Stored information may comprise received data and/or data to be presented, transmitted, and/or otherwise processed. The parameters may comprise configuration data and the code may comprise operational code such as software and/or firmware, but the information need not be limited in this regard.

The display183may be operable to provide visual presentation of information to, and/or enable interaction by, a user of the communication device180. In various embodiments of the invention, a graphical user interface may be presented via the display183. In various embodiments of the invention, a visual media content such as video, images, and text may be presented via the display183.

The user controls185may be operable to enable user interaction with the communication device180to control services and/or content handled by the communication device180. The user controls185may comprise, for example, a keypad, a keyboard, a roller ball, a multidirectional button, a scroll wheel or other navigation device, and/or a touch screen.

The speaker187may be operable to present audio information to a user. The speaker may present voice from a phone call and/or music or ringtones played back by the cellular enabled communication device.

The microphone189may be operable to convert acoustic signals into electronic signals. The microphone may enable a user to participate in a phone call and/or interact with the cellular enabled communication device via oral input.

In operation, the radio frequency transceiver184may receive data formatted according to one or more communication standards, process the data, and output digital baseband data to the processor188, the memory190, and/or the DSP192. In this regard, a noise reduction technique may be utilized to process the received data by using, for example, an integrated alternate adjacent channel interference (AACI) filter. The integrated AACI filter may be enabled to remove alternate adjacent channel signals from the received data. The digital baseband data may be processed by the processor188, the memory190, and/or the DSP192to effectuate operation of the communication device180and/or for presentation of content to a user of the communication device180.

FIG. 2is a diagram illustrating an exemplary radio frequency (RF) receiver that comprises an intermediate frequency (IF) channel select filter with an integrate AACI filter, in accordance with an embodiment of the invention. Referring toFIG. 2, there is shown a radio frequency receiver200comprising a RF front-end210, an antenna220, a baseband processor230, and a local oscillator (LO)240. The RF front-end210comprises a low noise amplifier (LNA)212, a downconversion mixer214, an IF channel-select filter216, and analog-to-digital converter (ADC)218.

The RF front-end210may comprise suitable logic, circuitry, and/or code that may be operable to process a received RF signals received via the antenna220. The RF front-end210may enable conversion of the received RF signal to a baseband frequency signal to be processed by the baseband processor130.

The LNA212may comprise suitable logic, circuitry and/or code that may be operable to amplify a received RF signals from the antenna220. The LNA212may be configured to set a fixed-gain typically used for initial amplification of the received a received RF signals. The fixed-gain may specify a limit for how low a system noise figure may reach. The LNA212may be enabled to achieve a low noise performance, which is crucial for a high performance radio frequency (RF) front-end.

The downconversion mixer214may comprise suitable logic, circuitry and/or code that may be operable to translate the resulted signals from the LNA212to a lower, intermediate frequency (IF) signals in conjunction with the local oscillator (LO)240. Contents in a passband associated with the downconversion mixer214may be translated in frequency to a fixed IF. The fixed IF may reside at the center of the IF channel-select filter216. The contents may comprise desired data as well as noises within the passband.

The IF channel-select filter216may comprise suitable logic, circuitry and/or code that may be enabled to retrieve received RF signals from the antenna220and/or remove unwanted channel signals. The IF channel-select filter216may be operable to locate a desired channel signal within an IF band of interest among the pass band of the IF channel-select filter216. For example, depending on implementation, in instances that the IF channel-select filter216may be realized via a low pass filter (LPF), the IF channel-select filter216may be enabled to locate the desired channel signal to reside at the center of corresponding lowpass band of the IF channel-select filter216. The IF channel-select filter216may be utilized to pass desired channel signals and reject unwanted channel signals. In this regard, an alternate adjacent channel interference (AACI) filter may be integrated into the IF channel-select filter216and may be used to reject larger-amplitude alternate-channel signals.

The variable-gain amplifier (VGA)217may comprise suitable logic, circuitry and/or code that may be operable to amplify signals from the IF channel-select filter216. In this regard, the VGA217may be operable to amplify of boost the desired channel signal from the IF channel-select filter216. The VGA217may be set to different gains resulting a variable signal level at the input to the ADC218.

The ADC218may comprise suitable logic, circuitry and/or code that may be operable to convert received analog signals from the VGA217to digital data (e.g., bytes) comprising values that are representative of the signal amplitude. The digital data may be communicated with the baseband processor230for further baseband processing.

The baseband processor230may comprise suitable logic, circuitry, interfaces and/or code that may be operable to process digitized baseband signals from the ADC218. The baseband processor230may be enabled to extract information conveyed in a received RF signal. The baseband processor230may be enabled to perform such operations as demodulation, decorrelation, decoding, and error correction.

The LO240may comprise suitable logic, circuitry, and/or code that may enable generating a stable reference frequency to be used for achieving channel tuning.

In an exemplary operation, the received RF signals from the antenna220may be amplified by the LNA212. The amplified RF signals may be translated to lower, intermediate frequency (IF) signals in conjunction with the local oscillator (LO)240. The IF channel-select filter216may be enabled to convert the IF signals from the LNA214to reside at the center of the IF channel-select filter216. In this regard, the IF channel-select filter216may be enabled to pass signals within a desired band and reject adjacent channel signals as well as alternate adjacent channel signals. Moreover, the IF channel select filter216may be coupled with an AACI filter for removing alternate adjacent channel signals. Following the IF channel-select filter216, the desired channel signals are boosted by the variable-gain amplifier (VGA)217to the baseband processor230via the ADC218for further signal processing.

FIG. 3is a diagram illustrating an exemplary graphical representation of an a received radio frequency signal received by a radio frequency (RF) receiver, in accordance with an embodiment of the invention. Referring toFIG. 3, there is shown a signal300A, a signal300B, and a signal300C. The signal300A is a channel signal response of a received RF signal received by the antenna220. The signal300B is a channel signal response of an output of the LNA212. The signal300C is a channel signal response of an output of the IF channel-select filter216. The signal300A comprises channel signal component302ain a desired channel, channel signal component304ain an adjacent channel, and channel signal component306ain an alternate adjacent channel, respectively. The signal300A transverses the LNA212following the signal path to the output of the LNA212.

The output of the LNA212is a linear amplified version of the received RF signal. Accordingly, the signal300B is the amplified version of the signal300A. The signal components302b,304b, and306brepresent amplified versions of the signal component302a,304a, and306a, respectively. Following the LNA212, the signal300btransverses the downconversion mixer214and the IF channel select filter216to the output of the IF channel select filter216. The signal300C represent the channel signal response of the output of the IF channel select filter216. The radio frequency receiver200may be enabled to tune the IF channel select filter216via the LO240such that the desired channel signal component such as the signal302cmay be received for processing by the baseband processor230to retrieve transmitted data. In this regard, the IF channel select filter216may be enabled to pass signal components such as the signal302cin the desired channel and filter out signal components such as the signal304band306bin an alternate adjacent channel and an adjacent channel, respectively. The signal components in the alternate adjacent channel, for example, the signal306c, may be removed by using an AACI filter integrated into the IF channel select filter216.

FIG. 4is a diagram illustrating an exemplary intermediate frequency (IF) channel select filter that comprising a plurality of IF stages, in accordance with an embodiment of the invention. Referring toFIG. 4, there is shown an IF channel select filter400comprising a plurality of intermediate frequency (IF) stages, of which IF stage_0410˜IF stage_n450, are displayed, where n is a positive integer number.

Each of the plurality of IF stages such as the IF stage_i440may comprise suitable logic, circuitry, and/or code that may be enabled to capture IF signal components within a desired channel to produce a selected channel signal. The IF stage_i440may be operable to remove interferences and noise from the received IF signal components. The IF stage_i440may be frequency selective to filter out signal components within unwanted channels. The IF stage_i440may be implemented as a 2-biquad integrator440a. The 2-biquad integrator440amay be adopted to implement various filtering functions such as the Butterworth function or the Chebyshev function. The 2-biquad integrator440amay comprise resistors R0i,R1i,R2i, and R3i, capacitors C1iand C2i, an inverter342, and Operational amplifiers A1i, and A2i. The resistances of the resistors R0i,R1i,R2i, and R3imay be configured to improve a desired amplitude stability of the 2-biquad integrator440a. The capacitors C1iand C2imay be realized utilizing any known techniques for on-chip capacitors. The capacitance of the capacitors C1iand C2imay be determined based on a desired frequency response and/or noise requirement of the IF stage_i440. Each IF stage of the IF channel select filter400may be concatenated so that they are operable to remove unwanted channel components outside the desired channel. In this regard, the first IF stage, the IF stage_0410, may be coupled to an AACI filter to remove unwanted channel components within an alternate adjacent channel.

In operation, desired frequency responses for each IF stage of the IF channel select filter400may be configured. The IF stage parameters such as resistances, capacitances, and amplify gains may be determined based on a desired frequency response of corresponding IF stage. In instances that the first IP stage_0410may receive RF signals from the downconversion mixer214. The first IF stage_0410may be enabled to pass channel signal components within a desired channel and remove unwanted channel signal components within adjacent channels and alternate adjacent channels. In this regard, the first IF stage_0410may be enabled to utilize an integrated AACI filter for removing channel signal components within the alternate adjacent channels. Following the first IF stage_0410, the received RF signals from the downconversion mixer214may be further filtered via successive IF stages of the IF channel select filter400. The IF stage_0410˜the IF stage_n450are operable to suppress interferences to the desired channel signal components from the adjacent channels as well as the alternate adjacent channels.

FIG. 5is a circuit diagram illustrating an alternate adjacent channel interference (AACI) filter integrated into an intermediate frequency (IF) channel select filter within a radio frequency (RF) receiver, in accordance with an embodiment of the invention. Referring toFIG. 5, there is shown an AACI filter500implemented via a single stage active RC filter.

The AACI filter500may comprise resistors R1and R2, capacitors C1, and an operational amplifier A3. The resistances of the resistors R1and R2may be configured to set the gain of the single stage active RC filter. The capacitance of the capacitors C1may be determined based on desired alternate adjacent frequencies for corresponding filtering. The AACI filter500may be enabled to remove channel components within the alternate adjacent channels based on a manner in which it is coupled to the first IF stage320of the IF channel select filter400. Due to the low noise requirement, the capacitors C1and the operational amplifier A3may occupy large chip area and consume large power. In this regard, the capacitor C00and the operational amplifier A10of the first IF stage_0410may be re-used for the AACI filter500. In this regard, the total chip area and power consumption for the AACI filter500may be reduced.

FIG. 6is a diagram illustrating an exemplary alternate adjacent channel interference (AACI) filter integrated into an IF stage of a radio frequency (RF) receiver circuit, in accordance with an embodiment of the invention. Referring to theFIG. 6, the AACI filter500may be coupled to the first IF stage_0410. The input resistor R00, the operational amplifier A10, and the capacitor C10in the first IF stage_0410may be re-utilized to integrate functions of the AACI filter500.

In an exemplary implementation as presented in602, the input resistor R00and the capacitor C10may be implemented serially to form a first order RC circuit coupled to the first IF stage_0410. In602, the input resistor R00may be split into two input resistors of R00/2. A shunt capacitor of 2 C10may be placed in the middle of the two input resistors of R00/2. For more general implementation, R00may be split into two resistors with un-equal values. With a shunting capacitor connecting between the middle node of the two resistors and ground, it may form a general form of AACI filter.

In another exemplary implementation as presented in604, the input resistor R00and the capacitor C10may be implemented differentially to form a first order RC circuit coupled to the first IF stage_0410. In604, the first order RC filter may be realized by splitting the input resistor R00into four input resistors of R00/2 together with a shunt capacitor of C10.

The input resistor R00may be chosen to be approximately inversely proportional to the bandwidth of the IF channel select filter400such that the shunt capacitor for AACI filter500may be fixed, for example, around 2 pF.

Aspects of a method and system for an intermediate frequency (IF) channel select filter with an integrated alternate adjacent channel interference (AACI) filter are provided. In accordance with various embodiments of the invention, the AACI filter500may be integrated into the IF channel select filter216. The IF channel select filter216with the integrated AACI filter500may be operable to filter a received RF signal that may be received by the antenna220. The IF channel select filter216may comprise a plurality of IF stages as presented inFIG. 4. The IF channel select filter400may comprise successive IF stages such as the IF stages410through450. Each of the IF stages410through450may be implemented as the 2-biquad integrator440a. The AACI filter500may be integrated into the first IF stage such as the IF stage_0410of the IF channel select filter400. The integrated AACI filter500may re-use circuit components of the first IF stage_0410to form a first order RC filter. The circuit components re-used in the IF stage_0410may comprise the operational amplifier A10, the input resistor R00, and the shunt capacitor C10. As shown with respect toFIG. 6, the shunt capacitor C10is placed between the middle of the split input resistor R00and ground. The AACI filter500may be realized via different equivalent implementations such as602or604of the input resistor R00and the shunt capacitor C10. A value of the shunt capacitor C10for the AACI filter500is a fixed-value when a value of the input resistor R00is set so that it is inversely proportional to the bandwidth of the AACI filter500.

Another embodiment of the invention may provide a machine and/or computer readable storage and/or medium, having stored thereon, a machine code and/or a computer program having at least one code section executable by a machine and/or a computer, thereby causing the machine and/or computer to perform the steps as described herein for an intermediate frequency (IF) channel select filter with an integrated alternate adjacent channel interference (AACI) filter.