Programmable baseband filter for selectively coupling with at least a portion of another filter

Abstract

One embodiment includes a filtering method comprising: operating a first filter to filter a first input signal to generate a first output signal; operating a second filter to filter a second input signal to generate a second output signal; and selectively coupling at least a portion of the second filter to the first filter to filter a third input signal to generate a third output signal. Another embodiment includes a filtering method comprising: operating a switching device to configure a filter to have a first set of poles; using the filter configured to have the first set of poles to filter a first input signal to generate a first output signal; operating a switching device to configure a filter to have a second set of poles; and using the filter configured to have the second set of poles to filter a second input signal to generate a second output signal.

Description

Technical Field

[0001] This patent application claims priority and interest in pending non-provisional application No. 17 / 318,959 filed with the U.S. Patent and Trademark Office on May 12, 2021, and provisional application No. 63 / 045,813 filed on June 29, 2020.

[0002] In summary, the contents of this case pertain to fundamental frequency filters, and more specifically to programmable fundamental frequency filters for filter coupling, pole selection, noise reduction, and multi-pole configurations for improved stopband suppression. Prior Technology

[0003] Wireless communication devices typically include a receiver with a low-noise amplifier (LNA), mixer, local oscillator (LO), baseband filter, and other processing circuitry for further processing of the received signal. The receiver can be configured to receive signals in different frequency channels. The operation of such a device in the receiver can depend on which specific frequency channel is being received. Accordingly, the device should be configured to adapt to the different frequency channels in a manner that does not unduly complicate the integrated circuit (IC) on which it is formed. Summary of the Invention

[0004] The following provides a simplified overview of one or more embodiments to provide a basic understanding of such embodiments. This overview is not a general summary of all contemplated embodiments and is neither intended to identify key or essential elements of all embodiments nor to illustrate the scope of any or all embodiments. Its sole purpose is to provide, in a simplified form, some concepts relating to one or more embodiments as a prelude to the more detailed description that follows.

[0005] One aspect of the content of this case relates to an apparatus. The apparatus includes: a first filter; a second filter; and a first group of one or more switching devices configured to selectively couple the first filter to the second filter.

[0006] Another aspect of this case relates to a method for filtering a signal. The method includes: operating a first filter to filter a first input signal to generate a first output signal; operating a second filter to filter a second input signal to generate a second output signal; and selectively coupling at least a portion of the second filter to the first filter to filter a third input signal to generate a third output signal.

[0007] Another aspect of this case relates to a filter. The filter includes: a first amplifier; a first resistor and a second resistor coupled in series between a first input of the filter and a first input of the first amplifier; a first feedback capacitor coupled between a first output of the first amplifier and a first input; a capacitor coupled to a first node between the first resistor and the second resistor; a first feedback resistor coupled to a first output of the first amplifier; and a first switching device for selectively coupling the first feedback resistor to either the capacitor or the first input of the first amplifier.

[0008] Another aspect of this case relates to a method for filtering a signal. The method includes: operating one or more sets of switching devices to configure a filter to have a first set of one or more poles; filtering a first input signal using the filter configured to have the first set of one or more poles to generate a first output signal; operating one or more sets of switching devices to configure a filter to have a second set of one or more poles; and filtering a second input signal using the filter configured to have the second set of one or more poles to generate a second output signal.

[0009] Another aspect of this case relates to a filter. The filter includes: a first amplifier having a differential input and a differential output; a first feedback resistor and a second feedback resistor coupled between the differential input and the differential output, respectively; and a plurality of switching devices configured to selectively couple the first feedback resistor to the second feedback resistor.

[0010] To achieve the foregoing and related objectives, one or more embodiments include the features fully described below and specifically pointed out in the claims. The following description and accompanying drawings illustrate certain illustrative features of one or more embodiments in detail. However, such feature indications may be made in only a few of the various ways in which they adopt the principles of the various embodiments, and the embodiments described are intended to include all such features and their equivalents. Simple Explanation of the Diagram

[0011] Figure 1A shows a schematic / block diagram of an example receiver based on the content of this case.

[0012] Figure 1B shows a graph of the spectrum and frequency response of an example receiving channel and baseband filter according to another aspect of the present case.

[0013] Figure 1C shows a graph of the spectrum and frequency response of another example of a receiving channel and a baseband filter according to another aspect of the present case.

[0014] Figure 1D shows a graph of the spectrum and frequency response of a receiving channel and a baseband filter, representing another example of a different state according to the contents of this case.

[0015] Figure 2A shows a schematic diagram of a programmable fundamental frequency filter designed according to another example of the content of this case.

[0016] Figure 2B shows a schematic diagram of an example programmable fundamental frequency filter of Figure 2A in a first configuration, according to another version of the content of this case.

[0017] Figure 2C shows a schematic diagram of the example programmable fundamental frequency filter of Figure 2A in a second configuration, according to another version of the content of this case.

[0018] Figure 2D shows a schematic diagram of the example programmable fundamental frequency filter of Figure 2A in a third configuration, according to another version of the content of this case.

[0019] Figure 2E shows a schematic diagram of the example programmable fundamental frequency filter of Figure 2A in a fourth configuration, according to another version of the content of this case.

[0020] Figure 2F shows a schematic diagram of the example programmable fundamental frequency filter of Figure 2A in a fifth configuration, according to another version of the content of this case.

[0021] Figure 2G shows a schematic diagram of an example programmable fundamental frequency filter of Figure 2A in a sixth configuration, according to another version of the content of this case.

[0022] Figure 3A shows a graph of the spectrum and frequency response of an example receiving channel and a single-pole fundamental frequency filter in zero intermediate frequency (ZIF) receiving mode, according to another example of the content of this case.

[0023] Figure 3B shows a graph of the spectrum and frequency response of another example receiving channel and single-pole fundamental frequency filter in offset zero intermediate frequency (OZIF) receiving mode, according to another aspect of the present case.

[0024] Figure 3C shows a graph of the spectrum and frequency response of another example receiving channel and complex pole fundamental frequency filter in offset zero intermediate frequency (OZIF) receiving mode, according to another aspect of the present case.

[0025] Figure 4A shows a schematic diagram of another example of a programmable fundamental frequency filter in a first configuration, according to another aspect of the present case.

[0026] Figure 4B shows a schematic diagram of the example programmable fundamental frequency filter of Figure 4A in a second configuration, according to another version of the content of this case.

[0027] Figure 5 shows a flowchart of an example method for filtering a signal according to another aspect of the content of this case.

[0028] Figure 6 shows a flowchart of another example method for filtering a signal according to another aspect of the content of this case.

[0029] Figure 7 shows a block diagram of an example wireless communication device according to another aspect of the content of this case.

[0030] Figure 8 shows a schematic / block diagram of another example receiver according to another state of the case.

[0031] Figure 9 shows a schematic diagram of another example of a programmable fundamental frequency filter designed according to another aspect of the content of this case. Implementation

[0032] The specific embodiments described below with reference to the accompanying drawings are intended as a description of various configurations and are not intended to represent the only configuration in which the concepts described herein can be implemented. To provide a thorough understanding of the various concepts, the specific embodiments include particular details. However, it will be apparent to those skilled in the art that these concepts can be implemented without such particular details. In some instances, well-known structures and components are shown in block diagram form to avoid obscuring such concepts.

[0033] Figure 1A shows a schematic / block diagram of an example receiver 100 according to the present invention. In this example, receiver 100 is configured to process a set of received channels, such as channel 1 having a corresponding component identified by a "-1" suffix and channel 2 having a corresponding component identified by a "-2" suffix.

[0034] Regarding channel 1, receiver 100 includes antenna 110-1, low noise amplifier (LNA) 120-1 (which may include antenna impedance matching elements such as an antenna impedance matching element represented by a series circuit of an inductor and a capacitor coupled to ground), analog processing circuitry 130-1, I-mixer 140-1I, Q-mixer 140-1Q, local oscillator (LO) 150-1, I-fundamental frequency filter (I-BBF) 160-1I, and Q-BBF 160-1Q.

[0035] Antenna 110-1 receives, for example, wireless signals transmitted by a remote wireless communication device and outputs the received signal. LNA 120-1 amplifies the received signal. Analog processing circuit 130-1 can perform one or more analog processing operations on the received signal, including but not limited to filtering, spatial processing, conversion of the signal to a differential signal, and / or other analog processing. As mentioned, the output of analog processing circuit 130-1 can be differential and coupled to the differential inputs of I-mixer 140-1I and Q-mixer 140-1Q, respectively.

[0036] LO 150-1 provides the LO signal and the 90° phase-shifted LO signal to the I-mixer 140-1I and the Q-mixer 140-1Q, respectively. Accordingly, the I-mixer 140-1I and the Q-mixer 140-1Q downconvert the I-quadrature component and the Q-quadrature component of the received signal, respectively, to generate the I-input differential signal ViI1+ / ViI1- and the Q-input differential signal ViQ1+ / ViQ1- for the I-BBF 160-1I and the Q-BBF 160-1Q. The I-BBF 160-1I and Q-BBF 160-1Q filter the input differential signals ViI1+ / ViI1- and ViQ1+ / ViQ1- respectively to remove high-frequency conversion components and other unwanted signals (such as interference), thereby generating output differential signals VoI1+ / VoI1- and VoQ1+ / VoQ1-. Although not illustrated, the output differential signals VoI1+ / VoI1- and VoQ1+ / VoQ1- are sent downstream for further processing, such as analog-to-digital conversion (ADC), demodulation, error correction, and decoding.

[0037] Similarly, regarding channel 2, receiver 100 includes antenna 110-2, low noise amplifier (LNA) 120-2 (which may include an antenna impedance matching element represented by a series circuit of an inductor and a capacitor coupled to ground), analog processing circuitry 130-2, I-mixer 140-2I, Q-mixer 140-2Q, local oscillator (LO) 150-2, I-fundamental frequency filter (I-BBF) 160-2I, and Q-BBF 160-2Q.

[0038] Antenna 110-2 receives, for example, wireless signals transmitted by a remote wireless communication device and outputs the received signal. LNA 120-2 amplifies the received signal. Analog processing circuit 130-2 can perform one or more analog processing operations on the received signal, including but not limited to filtering, spatial processing, conversion of the signal to a differential signal, and / or other analog processing. As mentioned, the output of analog processing circuit 130-2 can be differential and coupled to the differential inputs of I-mixer 140-2I and Q-mixer 140-2Q, respectively.

[0039] LO 150-2 provides the LO signal and the 90° phase-shifted LO signal to the I-mixer 140-2I and Q-mixer 140-2Q, respectively. Correspondingly, the I-mixer 140-2I and Q-mixer 140-2Q downconvert the I-quadrature and Q-quadrature components of the received signal to generate the I-input differential signals ViI2+ / ViI2- and the Q-input differential signals ViQ2+ / ViQ2- for the I-BBF 160-2I and Q-BBF 160-2Q, respectively. The I-BBF 160-2I and Q-BBF 160-2Q filter the input differential signals ViI2+ / ViI2- and ViQ2+ / ViQ2- respectively to remove high-frequency conversion components and other unwanted signals (such as interference), thereby generating output differential signals VoI2+ / VoI2- and VoQ2+ / VoQ2-. Although not illustrated, the output differential signals VoI2+ / VoI2- and VoQ2+ / VoQ2- are sent downstream for further processing, such as analog-to-digital conversion (ADC), demodulation, error correction, and decoding.

[0040] The first and second channels can be independent to receive two independent signals. Alternatively, the first and second channels can be used for spatial processing, such as multiple-input multiple-output (MIMO) processing. In the latter case, channel 1 can be used as the primary channel, and channel 2 can be used as the MIMO channel, and vice versa. Although two channels are shown for illustrative purposes, it will be understood that receiver 100 may include hardware for processing more than two channels, such as four channels (e.g., for 4x4 MIMO), five channels (e.g., for 100 MHz carrier aggregation), eight channels (e.g., for dual Subscriber Information Module (SIM) card operation), or ten channels (e.g., for 200 MHz carrier aggregation). Furthermore, although the elements for processing two channels are shown in FIG. 1 as coupled to corresponding antennas 110-1 and 110-2, in some embodiments, LNA 120-1 and LNA 120-2 are both coupled to the same antenna. In some such embodiments, duplexer or filter elements may be coupled between one or more LNA 110 and the antenna.

[0041] Due to the trend toward higher data throughput in this receiver 100, such as in the case of fifth-generation (5G) new radio (NR) developed by the 3rd Generation Partnership Project (3GPP) for mobile networks (referred to herein as "5G NR"), multiple channels for carrier aggregation (CA) can be present to achieve higher data throughput. For example, 10 channels, each with a bandwidth of 20 MHz, can provide a combined 200 MHz bandwidth for high data throughput applications.

[0042] To provide such multiple channels for high data throughput applications while simultaneously offering a relatively small integrated circuit (IC) footprint (e.g., for cost-effectiveness), new technology nodes (such as 14-nanometer (nm) FIN field-effect transistors (FINFETs) can be used in the active components (such as the I-BBF and Q-BBF 160-1I / 160-1Q and 160-2I / 160-2Q of channels 1 and 2 of receiver 100). Furthermore, for versatility, receiver 100 can be selectively reconfigured to handle channels specified by other standards, such as 4th generation broadband cellular networks (also known as Long Term Evolution (LTE)) and Global System for Mobile Communications (GSM) cellular networks developed by 3GPP.

[0043] For example, the use of new technology nodes in the active components of receiver 100 works well in filters with higher bandwidths (e.g., 5 MHz to 160 MHz) for 5G NR. However, since LTE and GSM utilize narrower bandwidths (e.g., down to 600 kHz to 1 MHz), new technology nodes may introduce flicker noise, where filter stopband (out-of-band) suppression is poor for certain levels of flicker noise. This may be the case at low frequencies, as the level of flicker noise varies inversely with frequency (1 / ƒ). To reduce flicker noise, new technology nodes may be made larger. However, making the device larger introduces additional parasitic capacitance, which may degrade performance for applications utilizing wider bandwidths, such as in the case of 5G NR, where communication bands and / or channels may be wider and / or significant carrier aggregation may be used. Furthermore, larger devices also occupy more IC coverage area, which may lead to higher product costs.

[0044] As discussed, for multi-function receivers, bandwidth can be selectively reconfigured for use in 5G NR, 4G, and / or GSM cellular networks. I-BBF and Q-BBF 160-1I / 160-1Q and 160-2I / 160-2Q can be selectively reconfigured for different bandwidths. For example, for 5G NR, I-BBF and Q-BBF 160-1I / 160-1Q and 160-2I / 160-2Q can be configured with poles in the range of approximately 100 MHz. For 4G, I-BBF and Q-BBF 160-1I / 160-1Q and 160-2I / 160-2Q can be configured with poles in the range of approximately 20 MHz. Furthermore, regarding GSM, I-BBF and Q-BBF 160-1I / 160-1Q and 160-2I / 160-2Q can be configured with poles in the range of approximately 660 kHz. This is explained in more detail with reference to the following graph.

[0045] Figure 1B shows a graph of the spectrum (shaded area) and frequency response H(ƒ) (dashed line) of an example received 5G NR channel (CHN) and baseband filter (BBF) according to another embodiment of the present case. The spectrum and frequency response H(ƒ) of the channel 5G NR CHN and BBF can be for the case where receiver 100 is configured to process signals according to 5G NR. The graph includes an x-axis or horizontal axis representing frequency (ƒ), and a y-axis or vertical axis representing the power level of the received channel 5G NR CHN signal and the frequency response H(ƒ) of the corresponding BBF. In this example, the spectrum of the received channel 5G NR CHN of interest has a bandwidth of approximately 100 MHz. Therefore, in order to filter the received channel 5G NR CHN signal to substantially eliminate unwanted signals (stopband rejection) to provide an acceptable signal-to-noise ratio (SNR), the frequency response H(ƒ) of the BBF should have poles ƒp approximately at -50 MHz and +50 MHz, respectively. The passband of the filter frequency response H(ƒ) can be a substantially flat region between the poles ƒp, and the roll-off of the filter frequency response H(ƒ) can be sloping portions below and above the poles ƒp, respectively.

[0046] Figure 1C shows a graph of the spectrum (shaded area) and frequency response H(ƒ) (dashed line) of an example received 4G channel (CHN) and baseband filter (BBF) according to another embodiment of the present invention. The spectrum and frequency response H(ƒ) of channel 4G CHN and BBF can be for the case where receiver 100 is configured to process signals according to 4G. In this example, the spectrum of the received channel 4G CHN of interest has a bandwidth of approximately 20 MHz. Therefore, in order to filter the signal of the received channel 4G CHN to substantially eliminate unwanted signals (stopband rejection) to provide an acceptable SNR, the frequency response H(ƒ) of BBF should have poles ƒp approximately at -10 MHz and +10 MHz, respectively. Similarly, the passband of the filter frequency response H(ƒ) can be a substantially flat region between the poles ƒp, and the roll-off of the filter frequency response H(ƒ) can be sloping portions below and above the poles ƒp, respectively.

[0047] Figure 1D shows a graph of the spectrum (shaded area) and frequency response H(ƒ) (dashed line) of an example received GSM channel (CHN) and baseband filter (BBF) according to another embodiment of the present invention. The spectrum and frequency response H(ƒ) of the GSM channel CHN and BBF can be for the case where receiver 100 is configured to process signals according to GSM. In this example, the spectrum of the received channel GSM CHN of interest has a bandwidth of approximately 60 kHz. Therefore, in order to filter the signal of the received channel to substantially eliminate unwanted signals to provide an acceptable SNR, the frequency response H(ƒ) of the BBF should have poles ƒp approximately at -300 kHz and +300 kHz, respectively. Similarly, the passband of the filter frequency response H(ƒ) can be a substantially flat region between the poles ƒp, and the roll-off of the filter frequency response H(ƒ) can be sloping portions below and above the poles ƒp, respectively.

[0048] Filters can include resistors and capacitor banks to frequency-shift poles when handling different applications, such as 5G NR, 4G, and GSM applications. However, resistors and capacitor banks are typically large and occupy a significant portion of the IC footprint; and therefore, may not be cost-effective. Furthermore, switching resistors and capacitor banks on and off can introduce increased parasitic capacitance, which can adversely affect filter performance (e.g., frequency selectivity and noise suppression).

[0049] Figure 2A shows a schematic diagram of an example programmable baseband filter 200 according to another aspect of the present invention. In summary, the baseband filter 200 includes a pair of baseband filters (BBFs) 210 and 250, which can be selectively coupled together in different ways to achieve improved performance for the filter 200 in different bandwidths for a particular application (e.g., specific bandwidths used in 5G NR, 4G, and GSM cellular networks).

[0050] In some bandwidth-specific applications, the BBF 210 and BBF 250 pairs can be selectively coupled to each other to (jointly) process a single received signal (e.g., a single channel). However, in other applications, the BBF 210 and BBF 250 pairs can also be completely decoupled to (independently) process separate received signals (e.g., two different channels). Selective coupling of the BBF 210 and BBF 250 pairs in different ways is possible.

[0051] For example, in applications with fairly narrow bandwidth and low noise, the first BBF 210 can utilize the active and passive components of the second BBF 250, where the active components reduce flicker noise by increasing the effective device size (e.g., doubling it), and the passive components (e.g., resistors and capacitors) result in narrower (or tighter) poles and / or increased stopband rejection (e.g., at lower frequencies). In this case, the second BBF 250 is not used to filter signals separated from signals filtered by the first BBF 210 using the components of the borrowed second BBF 250. For applications with particularly narrow bandwidth, such as in GSM, the first BBF 210 can also be selectively coupled to a capacitor bank to further narrow the pole frequency to achieve improved stopband rejection at such low frequencies.

[0052] In applications with relatively narrow bandwidth and low power, the first BBF 210 can borrow passive components (not active components) from the second BBF 250, where borrowing passive components (resistors and capacitors) results in narrower (closer) poles and / or increased stopband rejection (e.g., at lower frequencies), while disabling the active components of the second BBF 250 to save power. Again, in this case, the second BBF 250 is not used to filter signals separated from signals filtered by the first BBF 210 using the borrowed components of the second BBF 250.

[0053] In applications with fairly wide bandwidth and low noise, the first BBF 210 can borrow the active components (not passive components) of the second BBF 250, where borrowing the active components reduces flicker noise because the effective device size increases (e.g., doubles), while passive components are not needed for narrower (closer) poles. Again, in this case, the second BBF 250 is not used to filter the signal separated from the signal filtered by the first BBF 210 using the borrowed components of the second BBF 250.

[0054] As an example, the first BBF 210 can be selectively coupled to the second BBF 250 to borrow an amplifier from the second BBF 250, regardless of whether the associated resistor-capacitor (RC) feedback network is borrowed. Similarly, the first BBF 210 can be selectively coupled to the second BBF 250 to borrow a feedback network from the BBF 250, regardless of whether the feedback network is borrowed from its associated amplifier. In some embodiments, the amplifier from the BBF 250 and its associated feedback network can be independently and selectively coupled to the first BBF 210. In this embodiment, the first BBF 210 (more specifically, a group of one or more switching devices) can be configured to borrow an amplifier from the second BBF 250 but not its associated feedback network. Alternatively, the first BBF 210 (more specifically, a group of one or more switching devices) can be configured to borrow a feedback network from the second BBF 250 but not its associated amplifier. Alternatively, the first BBF 210 (more specifically, a group of one or more switching devices) can be configured to borrow an amplifier and its associated resistor-capacitor (RC) feedback network from the second BBF 250.

[0055] Regarding receiver 100, the first BBF 210 can be either I-BBF 160-1I or Q-BBF 160-1Q of channel 1. The second BBF 250 can be either I-BBF 160-2I or Q-BBF 160-2Q of channel 2. For example, the I-BBFs of channel 1 and channel 2 can be selectively coupled together, and / or the Q-BBFs of channel 1 and channel 2 can be selectively coupled together. If BBF 210 and BBF 250 are used to process discrete signals (such as in the case of two different channels or a main channel and a MIMO channel), then BBF 210 and BBF 250 are completely decoupled from each other. Therefore, there can be no IC area penalty, as the second BBF 250 might be needed to perform discrete channel processing. However, if the second BBF 250 is not used for separate channel processing, the first BBF 210 can be selectively coupled to the second BBF 250 to borrow active or passive components or both, in order to modify its filtering performance, for example, based on different bandwidth applications.

[0056] More specifically, the first BBF 210 includes a differential input configured to receive a differential signal Vi1+ / Vi1- that can be generated by one of the mixers 140-1I and 140-1Q of the receiver 100. The first BBF 210 also includes: a capacitor C11 coupled across the differential input, another capacitor C12+ coupled between the positive side of the differential input and ground, and another capacitor C12- coupled between the negative side of the differential input and ground. The first BBF 210 also includes a first resistor group 212+ coupled between the positive side of the differential input and the positive input of the first-stage amplifier 220. Additionally, the first BBF 210 includes a second resistor group 212- coupled between the negative side of the differential input and the negative input of the amplifier 220. The amplifier 220 can be configured as a transimpedance amplifier (TIA) (as indicated in Figures 2A-2G) and can include two or more internal amplification stages. For example, the first internal amplification stage of amplifier 220 may have an input coupled to resistor group 212 (directly or via one or more components (such as another internal amplification stage)) and an output coupled to the input of the second internal amplification stage of amplifier 220; the second internal amplification stage of amplifier 220 may have an output coupled to resistor R14 (described below) (directly or via one or more components (such as another internal amplification stage)).

[0057] The first BBF 210 also includes a first resistor-capacitor (RC) feedback network, which includes a capacitor C13+ (which may be variable) coupled in parallel with a resistor R13+ (which may be variable) between the negative output and positive input of the TIA 220. Similarly, the first BBF 210 also includes a second RC feedback network, which includes a capacitor C13- (which may be variable) coupled in parallel with a resistor R13- (which may be variable) between the positive output and negative input of the TIA 220. The TIA 220 including the RC feedback networks C13+ / R13+ and C13- / R13-, the first resistor group 212+ and the second resistor group 212-, and the capacitors C11, C12+ and C12- form the first filter stage of the first BBF 210. The resistances of resistor groups 212+ and 212-, the capacitance of feedback capacitors C13+ / C13-, and the resistance of feedback resistors R13+ / R13- can be varied to set the poles of the first filter stage.

[0058] The first BBF 210 also includes resistors R14+ and R15+ (one or both of which may be variable) coupled in series between the negative output of TIA 220 and the positive input of the second-stage amplifier 230. The first BBF 210 also includes resistors R14- and R15- (one or both of which may be variable) coupled in series between the positive output of TIA 220 and the negative input of amplifier 230. Amplifier 230 can be configured as a programmable gain amplifier (PGA) (as indicated in Figures 2A-2G) and can include two or more internal amplification stages. For example, the first internal amplification stage of amplifier 230 may have an input coupled (directly or via one or more components, such as another internal amplification stage) to resistor R15 and an output coupled to the input of the second internal amplification stage of amplifier 230; the second internal amplification stage of amplifier 230 may have an output coupled (directly or via one or more components, such as another internal amplification stage) to the output of a filter (described below).

[0059] Although not illustrated in Figures 2A-2G, a capacitor can be coupled between the first node between resistors R14+ and R15+ and the second node between resistors R14- and R15- to provide additional poles for the second filter stage, as further discussed herein with reference to another filter implementation. Alternatively, a single resistor (which may be variable) can be used instead of R14+ and R15+, and / or a single resistor (which may be variable) can be used instead of R14- and R15-.

[0060] The first BBF 210 also includes a third RC feedback network, which includes a capacitor C16+ (which may be variable) coupled in parallel with a resistor R16+ (which may be variable) between the negative output and positive input of the PGA 230. Similarly, the first BBF 210 also includes a fourth RC feedback network, which includes a capacitor C16- (which may be variable) coupled in parallel with a resistor R16- (which may be variable) between the positive output and negative input of the PGA 230.

[0061] PGA 230 includes differential outputs to generate filtered differential output signals Vo1+ / Vo1-, such as the output differential signals VoI1+ / VoI1- or VoQ1+ / VoQ1- of the I-BBF 160-1I or Q-BBF 160-1Q of receiver 100. PGA 230, including RC feedback networks C16+ / R16+ and C16- / R16-, and resistors R14+ / R15+ and R14- / R15-, forms a second filter stage of the first BBF 210. The resistances of resistors R14+ / R15+ and R14- / R15-, the capacitance of feedback capacitor C13+ / C13-, and the resistance of feedback resistor R13+ / R13- can be variable to set the poles of the second filter stage.

[0062] The second BBF 250 may be configured in the same or similar manner as the first BBF 210. Specifically, the second BBF 250 includes a differential input configured to receive differential signals Vi2+ / Vi2-, which may be generated by one of the mixers 140-2I and 140-2Q of the receiver 100. The second BBF 250 also includes: a capacitor C21 coupled across the differential input, another capacitor C22+ coupled between the positive side of the differential input and ground, and another capacitor C22- coupled between the negative side of the differential input and ground. The second BBF 250 also includes a first resistor group 252+ coupled between the positive side of the differential input and the positive input of the first-stage amplifier 260. Additionally, the second BBF 250 includes a second resistor group 252- coupled between the negative side of the differential input and the negative input of the amplifier 260. Amplifier 260 can be configured as a transimpedance amplifier (TIA) (as indicated in Figures 2A-2G) and can include two or more internal amplification stages. For example, a first internal amplification stage of amplifier 260 may have an input coupled (directly or via one or more components, such as another internal amplification stage) to resistor bank 252 and an output coupled to the input of a second internal amplification stage of amplifier 260; the second internal amplification stage of amplifier 260 may have an output coupled (directly or via one or more components, such as another internal amplification stage) to resistor R24 ​​(described below).

[0063] The TIA 260 may also include an enable input to receive a first enable signal (en1) for selectively enabling and disabling the TIA 260 (e.g., via turning on / off at least one readhead switch coupled to a DC power (Vdd) rail). Although not illustrated, the TIA 220 may also include a similar enable input.

[0064] The second BBF 250 also includes a first RC feedback network, which includes a capacitor C23+ (which may be variable) coupled in parallel with a resistor R23+ (which may be variable) between the negative output and positive input of the TIA 260. Similarly, the second BBF 250 also includes a second RC feedback network, which includes a capacitor C23- (which may be variable) coupled in parallel with a resistor R23- (which may be variable) between the positive output and negative input of the TIA 260. The TIA 260 including the RC feedback networks C23+ / R23+ and C23- / R23-, the first and second resistor groups 252+ and 252-, and the capacitors C21, C22+, and C22- form the first filter stage of the second BBF 250. The resistances of resistor groups 252+ and 252-, the capacitance of feedback capacitors C23+ / C23-, and the resistance of feedback resistors R23+ / R23- can be varied to set the poles of the first filter stage.

[0065] The second BBF 250 also includes resistors R24+ and R25+ (one or both of which may be variable) coupled in series between the negative output of TIA 260 and the positive input of the second-stage amplifier 270. The second BBF 250 also includes resistors R24- and R25- (one or both of which may be variable) coupled in series between the positive output of TIA 260 and the negative input of amplifier 270. Amplifier 270 can be configured as a programmable gain amplifier (PGA) (as indicated in Figures 2A-2G) and can include two or more internal amplification stages. For example, a first internal amplification stage of amplifier 270 may have an input coupled (directly or via one or more components, such as another internal amplification stage) to resistor R25 and an output coupled to the input of a second internal amplification stage of amplifier 270; the second internal amplification stage of amplifier 270 may have an output coupled (directly or via one or more components, such as another internal amplification stage) to the output of a filter (described below).

[0066] Although not illustrated in Figure 2, a capacitor can be coupled between the first node between resistors R24+ and R25+ and the second node between resistors R24- and R25- to provide additional poles for the second filter stage, as discussed with reference to another filter implementation. Alternatively, a single resistor (which may be variable) can be used instead of R24+ and R25+, and / or a single resistor (which may be variable) can be used instead of R24- and R25-.

[0067] The PGA 270 may also include an enable input to receive a second enable signal (en2) for selectively enabling and disabling the PGA 270 (e.g., via turning on / off at least one readhead switch coupled to the DC power supply (Vdd) rail). Although not illustrated, the PGA 230 may also include a similar enable input.

[0068] The second BBF 250 also includes a third RC feedback network, which comprises a capacitor C26+ (which may be variable) coupled in parallel with a resistor R26+ (which may be variable) between the negative output and positive input of the PGA 270. Similarly, the second BBF 250 also includes a fourth RC feedback network, which comprises a capacitor C26- (which may be variable) coupled in parallel with a resistor R26- (which may be variable) between the positive output and negative input of the PGA 270.

[0069] PGA 270 includes differential outputs to generate filtered differential output signals Vo2+ / Vo2-, such as the output differential signals VoI2+ / VoI2- or VoQ2+ / VoQ2- of receiver 100's I-BBF 160-2I or Q-BBF 160-2Q (if BBF 210 and BBF 250 are not coupled together by a set of switching devices, as further discussed herein). PGA 270, including RC feedback networks C26+ / R26+ and C26- / R26-, and resistors R24+ / R25+ and R24- / R25-, forms a second filter stage for the second BBF 250. The resistances of resistors R24+ / R25+ and R24- / R25-, the capacitance of feedback capacitors C26+ / C26-, and the resistance of feedback resistors R26+ / R26- can be varied to set the poles of the second filter stage.

[0070] The programmable BBF 200 also includes a set of switching devices for selectively coupling the individual nodes of BBF 210 and BBF 250 together to configure one filter (such as the first BBF 210) to have certain characteristics while disabling another filter (such as the second BBF 250) from filtering independent signals.

[0071] For example, BBF 200 includes switching devices SW1+ and SW1- for selectively coupling the positive and negative sides of the differential inputs of the first BBF 210 and the second BBF 250 together, respectively. BBF 200 also includes switching devices SW3+ and SW3- for selectively coupling the positive and negative inputs of TIA 220 and TIA 260 of the first BBF 210 and the second BBF 250 together, respectively. BBF 200 also includes switching devices SW7+ and SW7- for selectively coupling the negative and positive outputs of TIA 220 and TIA 260 of the first BBF 210 and the second BBF 250 together, respectively. Additionally, BBF 200 includes switching devices SW8+ and SW8- for selectively coupling the positive and negative inputs of PGA 230 and PGA 270 of the first BBF 210 and the second BBF 250 together, respectively. Furthermore, BBF 200 includes switching devices SW12+ and SW12-, which are used to selectively couple the negative and positive outputs of PGA 230 and PGA 270 of the first BBF 210 and the second BBF 250 together, respectively.

[0072] BBF 200 also includes switching devices SW4+, SW4-, SW5+, and SW5- for selectively coupling the RC feedback networks of TIA 220 and TIA 260 of the first BBF 210 and the second BBF 250 to the respective inputs / outputs of TIA 220 and TIA 260. Furthermore, switches SW4+, SW4-, SW5+, and SW5- can be configured, for example, to selectively couple the RC feedback networks of TIA 220 and TIA 260 of the first BBF 210 and the second BBF 250 together when switches SW3+, SW3-, SW7+, and SW7- are properly operated. BBF 200 also includes switching devices SW9+, SW9-, SW10+, and SW10- for selectively coupling the RC feedback networks of PGA 230 and PGA 270 of the first BBF 210 and the second BBF 250 to the respective inputs / outputs of PGA 230 and PGA 270. Furthermore, switches SW9+, SW9-, SW10+, and SW10- can be configured, for example, to selectively couple the RC feedback networks of PGA 230 and PGA 270 of the first BBF 210 and the second BBF 250 together when switches SW8+, SW8-, SW12+, and SW12- are properly operated. BBF 200 also includes switching devices SW6+ and SW6- for selectively coupling the differential output of the first internal stage of TIA 220 to the differential output of the first internal stage of TIA 260. Similarly, BBF 200 also includes switching devices SW11+ and SW11-, which are used to selectively couple the differential output of the first internal stage of PGA 230 to the differential output of the first internal stage of PGA 270.

[0073] BBF 200 also includes switching devices SW2+ and SW2- for selectively coupling resistor groups 252+ and 252- of the second BBF 250 to the positive and negative inputs of TIA 260, respectively. Although not explicitly shown, BBF 200 may include switching devices for selectively coupling / decoupling the variable resistors R24+, R24-, R25+, and R25- of the second BBF 250 to / from the first BBF 210.

[0074] Figure 2B shows a schematic diagram of a programmable fundamental frequency filter 200 according to another aspect of the present invention in a first configuration. In the first configuration, the first BBF 210 and the second BBF 250 operate independently of each other and filter the separate input signals Vi1+ / Vi1- and Vi2+ / Vi2- (e.g., simultaneously) to produce separate output signals Vo1+ / Vo1- and Vo2+ / Vo2-. Accordingly, in the first configuration, the switching devices SW1+ / SW1-, SW3+ / SW3-, SW6+ / SW6-, SW7+ / SW7-, SW8+ / SW8-, SW11+ / SW11-, and SW12+ / SW12- are configured to be in an off state. The switching devices in the off state decouple the first BBF 210 from the second BBF 250.

[0075] Furthermore, in the first configuration, switching devices SW2+ / SW2-, SW4+ / SW4-, SW5+ / SW5-, SW9+ / SW9-, and SW10+ / SW10- are configured to be in a closed state. Switching device SW2+ / SW2- in the closed state couples the differential input of the second BBF 250 to the differential input of the TIA 260. Switching devices SW4+ / SW4- and SW5+ / SW5- in the closed state couple the RC feedback networks C23+ / R23+ and C23- / R23- to the input and output of the TIA 260, respectively. Switching devices SW9+ / SW9- and SW10+ / SW10- in the closed state couple the RC feedback networks C26+ / R26+ and C26- / R26- to the input and output of the PGA 270, respectively. The first enable signal en1 and the second enable signal en1 are asserted to enable TIA 260 and PGA 270, respectively.

[0076] Figure 2C shows a schematic diagram of an example programmable fundamental frequency filter 200 in a second configuration according to another aspect of the present invention. In the second configuration, the first BBF 210 is selectively coupled to the second BBF 250 to borrow some of the passive components (resistors / capacitors) and active components (amplifiers) of the second BBF 250. This can result in narrower (closer) poles and higher stopband rejection, thereby achieving lower flicker noise. In the second configuration, the first BBF 210 filters the input differential signals Vi1+ / Vi1- to produce output differential signals for Vo1+ / Vo1-, while the second BBF 250 does not filter the separate signals because it is only used to provide additional components to the first BBF 210 for filtering operations.

[0077] Accordingly, in the second configuration, the switching devices SW1+ / SW1- and SW2+ / SW2- are configured to be in the off state to decouple the differential input of the second BBF 250, capacitors C21, C22+ / C22-, and resistor group 252+ / 252- from the first BBF 210. Although not explicitly shown, in the second configuration, switching devices may also be present to decouple the variable resistors R24+ / R24- and R25+ / R25- of the second BBF 250 from the first BBF 210.

[0078] Furthermore, in the second configuration, switching devices SW3+ / SW3-, SW4+ / SW4-, SW5+ / SW5-, SW6+ / SW6-, SW7+ / SW7-, SW8+ / SW8-, SW9+ / SW9-, SW10+ / SW10-, SW11+ / SW11-, and SW12+ / SW12- are configured to be in a closed state. The closed-state switching device SW3+ / SW3- couples the differential input of TIA 220 of the first BBF 210 to the differential input of TIA 260 of the second BBF 250. The closed-state switching devices SW4+ / SW4- and SW5+ / SW5- couple the RC feedback network C23+ / R23+ and C23- / R23- to the input and output of TIA 260, respectively. The closed-loop switching device SW6+ / SW6- couples the differential output of the first internal stage of TIA 220 to the differential output of the first internal stage of TIA 260. The closed-loop switching device SW7+ / SW7- couples the differential output of the first BBF 210 of TIA 220 to the differential output of the second BBF 250 of TIA 260. The first enable signal en1 is asserted to enable TIA 260.

[0079] Furthermore, in the second configuration, the closed-state switching devices SW8+ / SW8- couple the differential input of the PGA 230 of the first BBF 210 to the differential input of the PGA 270 of the second BBF 250. The closed-state switching devices SW9+ / SW9- and SW10+ / SW10- couple the RC feedback network C26+ / R26+ and C26- / R26- to the input and output of the PGA 270, respectively. The closed-state switching device SW11+ / SW11- couples the differential output of the first internal stage of the PGA 230 to the differential output of the first internal stage of the PGA 270. And the closed-state switching device SW12+ / SW12- couples the differential output of the PGA 230 of the first BBF 210 to the differential output of the PGA 270 of the second BBF 250. The second enable signal en2 is asserted to enable the PGA 270.

[0080] Figure 2D shows a schematic diagram of an example programmable fundamental frequency filter 200 in a third configuration, representing another aspect of the present invention. In the third configuration, the first BBF 210 is selectively coupled to the second BBF 250 to borrow some of the passive (resistor / capacitor) components of the second BBF 250, but not the active (amplifier) ​​components. Borrowing passive components from the first BBF 210 may result in narrower (closer) poles and higher stopband rejection, and not borrowing active components improves power savings because the TIA 260 and PGA 270 of the second BBF 250 can be disabled. In the third configuration, the first BBF 210 filters the input differential signals Vi1+ / Vi1- to produce output differential signals for Vo1+ / Vo1-, while the second BBF 250 does not filter the separated signals because it is only used to provide additional components to the first BBF 210 for filtering operations.

[0081] Accordingly, in the third configuration, switching devices SW1+ / SW1- and SW2+ / SW2- are configured to be in the off state to decouple the differential input of the second BBF 250, capacitors C21, C22+ / C22-, and resistor group 252+ / 252- from the first BBF 210. Switching devices SW6+ / SW6- and SW11+ / SW11- are also configured to be in the off state to decouple the differential outputs of the first internal stages of TIA 220 and PGA 230 from the differential outputs of the first internal stages of TIA 260 and PGA 270, respectively. The first enable signal en1 and the second enable signal en2 are not asserted, and therefore disable TIA 260 and PGA 270, respectively. Although not explicitly shown, in the third configuration, a switching device may also be present to decouple the variable resistors R24+ / R24- and R25+ / R25- of the second BBF 250 from the first BBF 210.

[0082] Furthermore, in the third configuration, the switching devices SW3+ / SW3-, SW4+ / SW4-, SW5+ / SW5-, SW7+ / SW7-, SW8+ / SW8-, SW9+ / SW9-, SW10+ / SW10-, and SW12+ / SW12- are configured to be in a closed state. The closed switching devices SW3+ / SW3-, SW4+ / SW4-, SW5+ / SW5-, and SW7+ / SW7- couple the RC feedback networks C23+ / R23+ and C23- / R23- of the second BBF 250 in parallel with the RC feedback networks C13+ / R13+ and C13- / R13- of the first BBF 210, respectively. Furthermore, the closed-state switching devices SW8+ / SW8-, SW9+ / SW9-, SW10+ / SW10-, and SW12+ / SW12- couple the RC feedback networks C26+ / R26+ and C26- / R26- of the second BBF 250 in parallel with the RC feedback networks C16+ / R16+ and C16- / R16- of the first BBF 210, respectively.

[0083] Figure 2E shows a schematic diagram of an example programmable fundamental frequency filter 200 in a fourth configuration according to another aspect of the present invention. In the fourth configuration, the first BBF 210 is selectively coupled to the second BBF 250 to borrow the active (amplifier) ​​components of the second BBF 250 without borrowing the passive (resistor / capacitor) components of the second BBF 250. This may result in lower flicker noise because the effective device size increases (e.g., doubles). Furthermore, it may not be necessary to borrow the passive components because the filter poles do not need to be narrow (tight) in frequency and a single-pole configuration may be sufficient to achieve the necessary stopband rejection. In the fourth configuration, the first BBF 210 filters the input differential signals Vi1+ / Vi1- to produce output differential signals for Vo1+ / Vo1-, while the second BBF 250 does not filter the separated signals because it is only used to provide additional components to the first BBF 210 for filtering operations.

[0084] Accordingly, in the fourth configuration, switching devices SW1+ / SW1- and SW2+ / SW2- are configured to be in the off state to decouple the differential input of the second BBF 250, capacitors C21, C22+ / C22-, and resistor group 252+ / 252- from the first BBF 210. Switching devices SW4+ / SW4- and SW5+ / SW5 are configured to be in the off state to decouple the RC feedback network C23+ / R23+ and C23- / R23- of the second BBF 250 from the first BBF 210. Similarly, switching devices SW9+ / SW9- and SW10+ / SW10- are configured to be in the off state to decouple the RC feedback network C26+ / R26+ and C26- / R26- of the second BBF 250 from the first BBF 210. Although not explicitly shown, in the fourth configuration, a switching device may also be present to decouple the variable resistors R24+ / R24- and R25+ / R25- of the second BBF 250 from the first BBF 210.

[0085] Furthermore, in the fourth configuration, switching devices SW3+ / SW3-, SW6+ / SW6-, SW7+ / SW7-, SW8+ / SW8-, SW11+ / SW11-, and SW12+ / SW12- are configured to be in a closed state. Switching device SW3+ / SW3- in the closed state couples the differential input of TIA 220 of the first BBF 210 to the differential input of TIA 260 of the second BBF 250. Switching device SW6+ / SW6- in the closed state couples the differential output of the first internal stage of TIA 220 to the differential output of the first internal stage of TIA 260. Switching device SW7+ / SW7- in the closed state couples the differential output of TIA 220 of the first BBF 210 to the differential output of TIA 260 of the second BBF 250. In the closed state, switching devices SW8+ / SW8- couple the differential input of PGA 230 of the first BBF 210 to the differential input of PGA 270 of the second BBF 250. Switching devices SW11+ / SW11- in the closed state couple the differential output of the first internal stage of PGA 230 to the differential output of the first internal stage of PGA 270. And switching devices SW12+ / SW12- in the closed state couple the differential output of PGA 230 of the first BBF 210 to the differential output of PGA 270 of the second BBF 250. First enable signal en1 and second enable signal en2 are asserted to enable TIA 260 and PGA 270, respectively.

[0086] Figure 2F illustrates a schematic diagram of another example of a programmable fundamental frequency filter 200 according to the contents of this case in a fifth configuration. The fifth configuration is similar to the second configuration discussed in detail earlier, wherein the first BBF 210 is selectively coupled to the second BBF 250 to borrow certain passive components (resistors / capacitors) and active components (amplifiers) of the second BBF 250, for example, to configure its performance to obtain narrower (closer) poles and higher stopband rejection as well as lower flicker noise.

[0087] To achieve narrower (closer) poles and higher stopband rejection performance, for example, in the case of processing GSM signals, the baseband filter 200 is selectively coupled to the capacitor bank 290. Specifically, when the switching devices SW13+ / SW17+ and SW13- / SW17- are configured to be in the closed state, the RC feedback networks C13+ / R13+ and C13- / R13- of the first BBF 210 and the RC feedback networks C23+ / R23+ and C23- / R23- of the second BBF 250 are coupled in parallel with the capacitors C+ and C- of the capacitor bank 290 via these switching devices. The capacitors C+ / C- lower the frequency of the poles of the baseband filter 200. The capacitors C+ / C- can represent a single capacitor or multiple capacitors. In some embodiments, the capacitors C+ / C- are variable and / or include multiple switchable components.

[0088] Figure 2G shows a schematic diagram of an example programmable fundamental frequency filter 200 in a sixth configuration, according to another aspect of the present invention. The sixth configuration is also similar to the second configuration discussed in detail earlier, wherein the first BBF 210 is selectively coupled to the second BBF 250 to utilize certain passive components (resistors / capacitors) and active components (amplifiers) of the second BBF 250, for example, to configure its performance to obtain narrower (closer) poles and higher stopband rejection as well as lower flicker noise.

[0089] To achieve higher stopband rejection performance at lower frequencies, the first BBF 210 can also be selectively coupled to the second BBF 250 to utilize the input passive components of the second BBF 250. In this case, the switching devices SW1+ / SW1- and SW2+ / SW2- are configured to be in a closed state to couple the capacitors C21, C22+ / C22- and the resistor group 252+ / 252- of the second BBF 250 to the first BBF 210. Although in this example, the variable resistors R24+ / R24- and R25+ / R25- of the second BBF 250 are shown as decoupled from the first BBF 210, it should be understood that these resistors can be coupled to the first BBF 210 via the corresponding switching devices.

[0090] It should be understood that not all configurations of BBF 200 are described and shown. For example, the switching device can be configured such that BBF 210 can be selectively coupled to the second BBF 250 to utilize resistor group 252+ / 252- without utilizing TIA 260 and / or the feedback network of TIA 260. As another example, the switching device can be configured such that BBF 210 can be selectively coupled to the second BBF 250 to utilize resistors R24+ / R24- and R25+ / R25- and other components of BBF 250, or without utilizing other components of BBF 250.

[0091] It should be further understood that not all described configurations must be provided via the implementation of the baseband filter 200, and therefore one or more of the connections and / or switching devices shown as coupling BBF 210 to BBF 250 may be omitted. For example, in some embodiments, the switching device (e.g., SW6+ / SW6-) that selectively couples the intermediate stage of TIA 220 to TIA 260 may be omitted; in other embodiments, the connection between these stages is omitted entirely, and therefore the intermediate stage of TIA 220 will not be selectively coupled to the intermediate stage of TIA 260. As another example, in some embodiments, the switching device that selectively couples the input of PGA 230 to the input of PGA 270 is not required, or in some embodiments, the switching device that couples the feedback network of TIA 220 to the feedback network of TIA 260 is not required. Accordingly, in some embodiments, any one or more switching devices described in BBF 200 may be omitted, such that the configuration implemented therein need not be available in all embodiments. This omission of the switching device may be caused by the permanent coupling or permanent decoupling of individual active / passive components of the second BBF 250 from the first BBF 210.

[0092] Figure 3A shows a graph of the spectrum (shaded area) and frequency response H(ƒ) (dashed line) of an example received channel CHN 1 and a single-pole fundamental frequency filter in zero intermediate frequency (ZIF) reception mode, according to another embodiment of the present case. In ZIF reception mode, the frequency of the LO is substantially the same as the carrier frequency of the channel of interest (such as CHN 1). Accordingly, when the associated mixer mixes the channel of interest CHN 1 with the LO, the resulting lower frequency component of the mixing operation is centered at zero hertz (0 Hz) or DC, as shown via the shaded area representing CHN 1. The passband of the filter frequency response H(ƒ) can be a substantially flat region between the poles ƒp, and the roll-off of the filter frequency response H(ƒ) can be sloping portions below and above the poles ƒp, respectively.

[0093] The transmit channel associated with the received CHN 1 may include a transmit signal that may leak into the received CHN 1 via antenna-to-antenna coupling or transmitter-to-receiver coupling and may be considered an interference signal relative to the received CHN 1. As shown, the transmit (Tx) interference is separated from the spectrum of CHN 1 by a certain frequency offset. A baseband filter (BBF) configured to filter CHN 1 to remove high-frequency components and other unwanted signals (such as CHN 1 Tx interference) can be configured as a single-pole ƒp frequency response H(ƒ) (represented by a dashed line around the spectrum of CHN 1) because its stopband rejection at the frequency of CHN 1 Tx interference is sufficient to reduce its power level so that the interference does not significantly affect the SNR of CHN 1.

[0094] Figure 3B shows a graph of the spectrum (shaded area) and frequency response H(ƒ) (dashed line) of another example of a received channel and a single-pole fundamental frequency filter in Offset Zero Intermediate Frequency (OZIF) receive mode, according to another aspect of the present invention. In OZIF receive mode, both channels (e.g., CHN 1-2) are down-converted and filtered by the same mixer and fundamental frequency filter. Since both channels are processed by the same hardware, the OZIF mode of the received channel saves significant IC area and power. In OZIF mode, the frequency of the LO is set between (e.g., in the middle) the spectrum of the first and second channels CHN 1-2. Accordingly, when the associated mixer uses the LO to mix the channel of interest, the resulting lower frequency component of the mixing operation is centered at 0 Hz or DC, as shown via the shaded areas representing CHN 1 and CHN 2.

[0095] The transmit channel associated with the received CHN 1 generates a signal that is considered an interference signal relative to the received CHN 1. As shown, the CHN 1 transmit (Tx) interference is separated from the spectrum of CHN 1 by a certain frequency offset. The baseband filter (BBF), which was previously configured as a single pole to filter CHN 1 to remove high-frequency components and other unwanted signals (such as CHN 1 Tx interference), must now also filter CHN 2 to remove such unwanted signals from the frequency band of CHN 2. Note that the CHN 1 Tx interference may be close in frequency to the frequency band of CHN 2, and the single-pole ƒp BBF (which has a frequency response H(ƒ) sufficient to suppress CHN 1 Tx interference in ZIF mode) may not be sufficient to suppress the interference relative to CHN 2.

[0096] Figure 3C shows a graph of the spectrum (shaded area) and frequency response H(ƒ) (dashed line) of another example of a channel and a complex pole ƒp fundamental frequency filter received according to another aspect of the present case in Offset Zero Intermediate Frequency (OZIF) receiving mode. As shown in this figure, a solution for suppressing CHN 1 Tx interference to prevent SNR degradation of channel 2 can be achieved by using a higher pole filter. A higher pole filter can have a steeper roll-off outside the pole frequency ƒp compared to a single pole filter. This is shown in Figure 3B, where the frequency response H(ƒ) of a single pole filter has a roll-off on the negative frequency side that, for example, reduces the intensity of CHN 1 Tx interference by half; however, as shown in Figure 3C, the frequency response H(ƒ) of a complex pole filter has a roll-off on the negative frequency side that significantly reduces the intensity of CHN 1 Tx interference by more than half.

[0097] One approach is to use a dual second-order filter with two poles. However, using a dual second-order filter has drawbacks. Such a filter typically requires two additional operational amplifiers and RC poles to achieve the desired stopband rejection. This can lead to a significant increase in the IC coverage area to be achieved, which is not considered a cost-effective approach. Furthermore, a dual second-order filter implemented for each OZIF receiver may require lengthy calibration to reduce residual sidebands (RSBs) resulting from down-conversion of the image of the desired channel, as well as mismatches in the amplitude and phase of the LOs applied to the I-mixer and Q-mixer.

[0098] Figure 4A shows a schematic diagram of another form of programmable fundamental frequency filter (BBF) 400 according to the present invention. In summary, the programmable BBF 400 includes switching devices to configure the filter to have a single pole, two poles, or complex poles. When the programmable BBF 400 is filtering a signal in ZIF mode, a single-pole configuration can be used because a single-pole filter may be sufficient to provide the required interference suppression. When the programmable BBF 400 is filtering a signal in OZIF mode, a complex-pole configuration can be programmed (or configured) because a complex pole may be required to provide the required interference suppression.

[0099] Specifically, the programmable BBF 400 includes a differential input configured to receive input differential signals Vi1+ / Vi1- from a corresponding mixer of, for example, receiver 100. The BBF 400 is configured to filter the input differential signals Vi1+ / Vi1- to generate output differential signals Vo1+ / Vo1- at the differential output. The programmable BBF 400 includes a capacitor C11 coupled across the positive and negative sides of the differential input. The BBF 400 also includes a capacitor C12+ coupled between the positive side of the differential input and ground, and another capacitor C12- coupled between the negative side of the differential input and ground. Additionally, the programmable BBF 400 includes a first resistor group 412+ coupled between the positive side of the differential input and the positive input of a first-stage amplifier 420, which can be configured as a transimpedance amplifier (TIA). Additionally, the programmable BBF 400 includes a second resistor group 412- coupled between the negative side of the differential input and the negative input of the TIA 420.

[0100] The programmable BBF 400 includes a first RC feedback network comprising a capacitor C13+ (which may be variable) coupled in parallel with a resistor R13+ (which may be variable) between the negative output and positive input of the TIA 420. Similarly, the BBF 400 also includes a second RC feedback network comprising a capacitor C13- (which may be variable) coupled in parallel with a resistor R13- (which may be variable) between the positive output and negative input of the TIA 420. The TIA 420, including the RC feedback networks C13+ / R13+ and C13- / R13-, the first resistor group 412+ and the second resistor group 412-, and the capacitors C11, C12+, and C12- form the first filter stage of the programmable BBF 400. The resistances of resistor groups 412+ and 412-, the capacitance of feedback capacitors C13+ / C13-, and the resistance of feedback resistors R13+ / R13- can be varied to set the poles of the first filter stage.

[0101] The programmable BBF 400 also includes variable resistors R14+ and R15+ coupled in series between the negative output of TIA 420 and the positive input of a second amplification stage 430, which can be configured as a programmable gain amplifier (PGA). The programmable BBF 400 also includes variable resistors R14- and R15- coupled in series between the positive output of TIA 420 and the negative input of PGA 430. The programmable BBF 400 also includes a capacitor C14, which includes a first terminal coupled to a first node between resistors R14+ and R15+ and a second terminal coupled to a second node between resistors R14- and R15-, for configuring the BBF 400 with complex poles, as further described herein. In the case of a single-ended filter, the second terminal of capacitor C14 can be coupled to ground.

[0102] The programmable BBF 400 also includes a third RC feedback network, which comprises a capacitor C16+ (which may be variable) coupled in parallel with a resistor R16+ (which may be variable) to the negative output of the PGA 430. Similarly, the programmable BBF 400 also includes a fourth RC feedback network, which comprises a capacitor C16- (which may be variable) coupled in parallel with a resistor R16- (which may be variable) to the positive output of the PGA 430. Capacitors C16+ and C16- are also connected to the positive and negative inputs of the PGA 430, respectively.

[0103] The PGA 430 includes differential outputs to generate filtered differential output signals Vo1+ / Vo1-, such as the output differential signals VoI1+ / VoI1- or VoQ1+ / VoQ1- of the I-BBF 160-1I or Q-BBF 160-1Q of receiver 100. The PGA 430, including RC feedback networks C16+ / R16+ and C16- / R16-, resistors R14+ / R15+ and R14- / R15-, and capacitor C14, form a second filter stage of the BBF 400. The resistances of resistors R14+ / R15+ and R14- / R15-, the capacitance of feedback capacitor C16+ / R16+, and the resistance of feedback resistor R16+ / R16- can be variable to set the poles of the second filter stage.

[0104] To program the programmable BBF 400 between single-pole and complex-pole terminals, the BBF 400 includes switching devices SW14+ / SW14-, SW15+ / SW15-, and optionally SW16+ / SW16-. Switching device SW14+ is connected between resistor R16+ and the positive input of PGA 430. Switching device SW15+ is connected between resistor R16+ and a first node between variable resistors R14+ and R15+. Similarly, switching device SW14- is connected between resistor R16- and the negative input of PGA 430. Switching device SW15- is connected between resistor R16- and a second node between variable resistors R14- and R15-. Although the switching devices SW14+, SW14-, SW15+, and SW15- are shown as separate devices in Figures 4A-4G, the switching devices SW14+ and SW15+ can be configured as switches with multiple throws, and / or the switching devices SW14- and SW15- can be configured as switches with multiple throws.

[0105] As illustrated in Figure 4A, the programmable BBF 400 is in a single-pole configuration, for example, to process signals according to the ZIF receive operation mode. In the single-pole configuration, switching devices SW14+ / SW14- are configured to be closed, switching devices SW15+ / SW15- are open, and switching devices SW16+ / SW16- (if present) can be configured to be open. Accordingly, in this configuration, the PGA 430 includes an RC feedback network R16+ / C16+ connected between the negative output and positive input of the PGA 430, and an RC feedback network R16- / C16- connected between the positive output and negative input of the PGA 430. This is a single-pole configuration because the RC feedback network provides a single pole.

[0106] If the switching device SW16+ / SW16- is not present, capacitor C14 is effective because it is coupled across the first node between resistors R14+ and R15+ and the second node between R14- and R15-. However, in this configuration, the pole formed by capacitor C14 can be far in frequency from the dominant pole formed by the RC feedback network so as not to have a significant impact on the frequency response and roll-off of the BBF 400.

[0107] Figure 4B shows a schematic diagram of another programmable design of the BBF 400 in a complex pole configuration according to the present invention. In the complex pole (multiple pole) configuration, switching devices SW14+ / SW14- are configured to be open, switching devices SW15+ / SW15- are configured to be closed, and switching devices SW16+ / SW16- (if present) are configured to be closed. Accordingly, in this configuration, the PGA 430 includes a capacitor C16+ connected to the RC feedback network between the negative output and the positive input of the PGA 430, and a resistor R16+ connected to the negative output and the first node between resistors R14+ and R15+ in the RC feedback network. Similarly, in this configuration, the PGA 430 includes a capacitor C16- connected to the RC feedback network between the positive output and the negative input of the PGA 430, and a resistor R16- connected to the RC feedback network between the positive output and a second node between resistors R14- and R15-.

[0108] In this configuration, regardless of the presence of the switching devices SW16+ / SW16-, capacitor C14 is connected between the first node (between resistors R14+ and R15+) and the second node (between R14- and R15-). In this configuration, the second filter stage of the programmable BBF 400 is configured as a Rauch filter, which includes complex poles to provide improved stopband rejection, for example, to suppress transmit (Tx) interference associated with the first channel near the second channel in OZIF receive operation mode. The additional switching devices do not add a significantly larger IC coverage area; therefore, single-pole or complex-pole filtering is provided without a significant cost increase.

[0109] Although the filters have been described as differential filters in the preceding examples, it should be understood that techniques for selectively coupling filters together or selectively reconfiguring filters between single-pole and multi-pole configurations are applicable to single-ended filters. Furthermore, although the filters have been described as having two stages in the preceding examples, it should be understood that techniques for selectively coupling filters together or selectively reconfiguring filters between single-pole and multi-pole configurations are applicable to filters with one or more stages. Additionally, although not explicitly shown, a controller may be provided to configure the states of the switching devices and the resistance and capacitance of the variable resistors and capacitors to set the filter in any of the configurations described above.

[0110] Figure 5 shows a flowchart of an example method 500 for filtering a signal according to another aspect of the present invention. Method 500 includes: operating a first filter to filter a first input signal to generate a first output signal (block 510). An example unit for operating the first filter to filter the first input signal to generate the first output signal includes a switching device of a first BBF 210, a resistor / capacitor, and / or an amplifier.

[0111] Method 500 also includes: operating a second filter to filter the second input signal to generate a second output signal (block 520). Example units for operating the second filter to filter the second input signal to generate the second output signal include a switching device of the second BBF 250, a resistor / capacitor, and / or an amplifier. This could be a case where the first BBF 210 and the second BBF 250 independently filter separate signals (such as separate channels or a main channel and a MIMO channel).

[0112] Method 500 further includes selectively coupling (e.g., merging) at least a portion of the second filter to the first filter to filter the third input signal to produce a third output signal (block 530). An example unit switching device for selectively coupling at least a portion of the second filter to the first filter to filter the third input signal to produce a third output signal includes any switching device that selectively couples the first BBF 210 and the second BBF 250 together, wherein the resulting selectively coupled filter filters the third input signal to produce the third output signal.

[0113] Figure 6 shows a flowchart of another example method 600 for filtering a signal according to another aspect of the present invention. Method 600 includes: operating a set of one or more switching devices to configure the filter to have a first set of one or more poles (block 610). An example unit for operating a set of one or more switching devices to configure the filter to have the first set of one or more poles includes a controller configuring the states of the switching devices SW14+ / SW14- and SW15+ / SW15- of BBF 400.

[0114] Method 600 also includes filtering the first input signal using a filter configured to have one or more poles in a first set to generate a first output signal (block 620). An example unit for filtering the first input signal using a filter configured to have one or more poles in a first set to generate a first output signal includes BBF 400 (or a portion thereof), wherein the switching devices SW14+ / SW14- and SW15+ / SW15- of BBF 400 are configured to be in a closed and open state, respectively.

[0115] Method 600 also includes: operating one or more sets of switching devices to configure the filter to have a second set of one or more poles (block 630). An example unit for operating one or more sets of switching devices to configure the filter to have a second set of one or more poles includes a controller that configures the states of the switching devices SW14+ / SW14- and SW15+ / SW15- of BBF 400.

[0116] Additionally, method 600 includes filtering the second input signal using a filter configured to have one or more poles in a second set to generate a second output signal (block 640). An example unit for filtering the second input signal using a filter configured to have one or more poles in a second set to generate a second output signal includes BBF 400 (or a portion thereof), wherein the switching devices SW14+ / SW14- and SW15+ / SW15- of BBF 400 are configured to be in an open and closed state, respectively.

[0117] Figure 7 shows a block diagram of an example wireless communication device 700 according to another aspect of the present invention. The wireless communication device 700 includes one or more antennas 710 and a receiver (or transceiver) 720, at least a portion of which is configured according to a receiver 100 having any of the BBFs described herein. The wireless communication device 700 also includes baseband processing circuitry 730 configured to process signals from the receiver 720.

[0118] Figure 8 shows a schematic / block diagram of another example receiver 800 according to another aspect of the present invention. Receiver 800 is an example of a receiver including a first programmable fundamental frequency filter (such as the previously discussed programmable filter 200) and a second programmable fundamental frequency filter (such as the previously discussed programmable filter 400). Depending on the fundamental frequency filter's requirements for passband ripple and stopband suppression, either the first or second programmable filter can be selected, and the selected filter can be programmed according to the passband ripple and stopband suppression requirements.

[0119] More specifically, receiver 800 includes at least one antenna 805, a low-noise amplifier (LNA) 810, a mixer 815, a local-end oscillator (LO) 820, and a baseband filter, which includes a programmable filter 830 that is the same as or similar to the programmable filter 200 discussed in detail above, and a programmable single-pole / complex-pole filter 840 that is similar to the programmable baseband filter 400 discussed in detail above. Receiver 800 also includes a controller 850 for selecting which filter 830 or 840 will filter the signal output from mixer 815 and for programming the selected filter, as further discussed herein.

[0120] At least one antenna 805 is coupled to the input of LNA 810. LNA 810 includes an output coupled to a first input of mixer 815. LO 820 includes an output coupled to a second input of mixer 815. Mixer 815 includes an output coupled to a first input of programmable filter 830 via switching device SW1 and to the input of programmable single-pole / complex-pole filter 840 via another switching device SWM.

[0121] The programmable filter 830 includes a second input that can be coupled to another receiver (Rx) chain, such as another quadrature (I- or Q) receiver chain, a spatial receiver chain, or another channel receiver chain. The programmable filter 830 includes a first single-pole fundamental frequency filter 832 (which can be configured similarly to the previously discussed BBF 210) and a second single-pole filter 834 (which can be configured identically or similarly to the previously discussed BBF 250). The first single-pole filter 832 includes an input coupled to the other receiver (Rx) chain via a switching device SW2. The second single-pole filter 834 includes an input that serves as the first input to the programmable filter 830.

[0122] For filter coupling purposes, the programmable filter 830 includes a set of switching devices SW3 to SWK. For example, switching device SW3 selectively couples the inputs of single-pole filters 832 and 834 together, switching device SWK selectively couples the outputs of single-pole filters 832 and 834 together, and switching devices SW4 to SWK-1 (not explicitly referenced) selectively couple the internal nodes of single-pole filters 832 and 834 together. The outputs of single-pole filters 832 and 834 are coupled to downstream processing via switching devices SWK+1 and SWK+2, respectively. As previously discussed, downstream processing may include analog-to-digital conversion (ADC), demodulation, error correction decoding, etc.

[0123] As discussed in detail regarding the fundamental frequency filter 200, single-pole filters 832 and 834 can operate independently of each other, such as when single-pole filter 832 filters the signal output from another receiver (Rx) chain and single-pole filter 834 filters the signal output from mixer 815. In this case, the set of switching devices SW3 to SWK are in the off state. Furthermore, one or more of single-pole filters 832 and 834 can be made inoperable or disabled independently. For example, single-pole filter 832 can be made inoperable or disabled by configuring switching devices SW2 to SWK+1 to be in the off state, and single-pole filter 834 can be made inoperable or disabled by configuring switching devices SW1, SW3 to SWK and SWK+2 to be in the off state.

[0124] Similarly, as discussed in detail with respect to fundamental frequency filter 200, single-pole filters 832 and 834 can be selectively coupled. As discussed, one filter (832 or 834) can be selectively coupled to another filter (834 or 832) to borrow the active, passive, or both active and passive components of the other filter (834 or 832).

[0125] For example, if the signal output from another receiver (Rx) chain is to be filtered by selectively coupled single-pole filters 832 and 834, then one or more of switches SW2, SW3 through SWK, and switch SWK+1 are configured to be in a closed state, and switches SW1 and SWK+2 are configured to be in an open state. In this example, the upstream and downstream sides of switches SW2 and SWK+1 act as the input and output of the programmable filter 830, respectively.

[0126] Similarly, if the signal output from mixer 815 is to be filtered by selectively coupled single-pole filters 832 and 834, then one or more of switches SW1, SW3 through SWK, and switch SWK+2 are configured to be in a closed state, and switches SW2 and SWK+1 are configured to be in an open state. In this example, the upstream and downstream sides of switches SW2 and SWK+2 serve as the input and output of programmable filter 830, respectively.

[0127] As discussed, the programmable single-pole / complex-pole filter 840 can be configured in the same or similar manner as the BBF 400. Accordingly, the programmable single-pole / complex-pole filter 840 includes a set of internal switching devices SWM+1 to SWN-1 (not explicitly shown) to configure the filter as a single-pole or complex-pole filter. The programmable single-pole / complex-pole filter 840 includes an output coupled to downstream processing via the switching device SWN.

[0128] Controller 850 generates control signals for a set of switching devices SW1 to SWN based on passband ripple and stopband rejection requirements to provide the desired filter response at the output of mixer 814 and / or the output of another receiver (Rx) chain. For example, if a programmable filter 830 is selected to filter the signal output from mixer 815, controller 850 configures switching device SW1 to be closed and at least switching device SWM to be open. Furthermore, controller 850 configures a set of switching devices SW2 to SWK+2 to program filter 830 as previously discussed (e.g., operating single-pole filters 832 and 834 independently or in a selectively coupled configuration).

[0129] If a programmable single-pole / complex-pole filter 840 is selected to filter the signal output from mixer 815, controller 850 will at least configure switch SW1 to the open state and switches SWM and SWN to the closed state. Furthermore, controller 850 configures a set of switches SWM+1 to SWN-1 to program (or configure) filter 840 as previously discussed (e.g., to operate it as a single-pole or complex-pole filter).

[0130] Figure 9 illustrates a schematic diagram of another example of a programmable fundamental frequency (BBF) filter 900 according to another aspect of the present invention. The programmable BBF 900 includes a first BBF 910 and a second BBF 950. Each of BBFs 910 and 950 can be configured in the same or similar manner as BBF 400. That is, each of BBFs 910 and 950 can be configured as a single-pole filter or a complex-pole filter as discussed in detail with respect to BBF 400. Furthermore, similar to the filter element borrowing or filter coupling scheme of the programmable BBF 200, the programmable BBF 900 includes a set of switching devices such that one of BBFs 910 or 950 can borrow one or more active and / or passive components from the other BBF 950 or 910.

[0131] Therefore, BBF 910 can be operated independently of BBF 950 to perform single-pole or complex-pole filtering of the input signals Vi1+ / Vi1- to produce filtered outputs Vo1+ / Vo1-. In this configuration, the switching device for selectively coupling BBF 910 to BBF 950 can be configured to be open. Similarly, BBF 950 can be operated independently of BBF 910 to perform single-pole or complex-pole filtering of the input signals Vi2+ / Vi2- to produce filtered outputs Vo2+ / Vo2-. In this configuration, the switching device for selectively coupling BBF 950 to BBF 910 can be open. In some configurations, the operation of one or both of BBF 910 and 950 filtering signals that are separate from the components or operation of the other BBF is described as a first operating mode.

[0132] As discussed in detail with respect to BBF 200, one of BBF 910 or 950 can be selectively coupled to another BBF 950 or 910 to utilize one or more active and / or passive components of the other BBF 950 or 910. For example, BBF 910 can be operated to filter the input signals Vi1+ / Vi1- to produce filtered outputs Vo1+ / Vo1- by selectively coupling BBF 910 to one or more active and / or passive components of BBF 950. In this configuration, one or more switching devices in the switching apparatus for selectively coupling BBF 910 to BBF 950 can be configured to be in a closed state, and the remaining switching devices (if any) can be configured to be in an open state. In some configurations, this operation can be described as a second operating mode.

[0133] Similarly, BBF 950 can be operated to filter the input signal Vi2+ / Vi2- to produce a filtered output Vo2+ / Vo2- by selectively coupling BBF 950 to one or more active and / or passive components of BBF 910. In this configuration, one or more switching devices in the switching apparatus for selectively coupling BBF 950 to BBF 910 can be configured to be in a closed state, and the remaining switching devices (if any) can be configured to be in an open state. In some configurations, this operation can be described as a third operating mode. In some embodiments, when filter 900 operates in a second or third mode, neither BBF 910 nor BBF 950 is controlled to perform complex pole filtering (e.g., switching devices SW14+ / SW14- are configured to be in a closed state, and switching devices SW15+ / SW15- are configured to be in an open state).

[0134] The following provides an overview of the various aspects of this case:

[0135] Example 1: An apparatus comprising: a first filter; a second filter; and a first group of one or more switching devices configured to selectively couple the first filter to the second filter.

[0136] State 2: The apparatus according to State 1, wherein: the first filter includes a first amplifier; the second filter includes a second amplifier; and a first group of one or more switching devices are configured to selectively couple the inputs and outputs of the first amplifier and the second amplifier together.

[0137] State 3: The apparatus according to State 2, wherein: the first amplifier includes a first resistor-capacitor (RC) feedback network coupled between the input and output of the first amplifier; and the second amplifier includes a second RC feedback network selectively coupled between the input and output of the second amplifier.

[0138] State 4: The device according to State 2 or 3, wherein: the first amplifier includes a first internal amplification stage and a second internal amplification stage, the output of the first internal amplification stage being coupled to the input of the second internal amplification stage; the second amplifier includes a third internal amplification stage and a fourth internal amplification stage, the output of the third internal amplification stage being coupled to the input of the fourth internal amplification stage; and the device also includes a second set of one or more switching devices configured to selectively couple the outputs of the first internal amplification stage and the third internal amplification stage together.

[0139] State 5: The apparatus according to any one of States 2-4, wherein: the first filter also includes a first resistor coupled between a first input of the first filter and an input of the first amplifier; the second filter also includes a second resistor coupled between a second input of the second filter and an input of the second amplifier; and the apparatus also includes a second set of one or more switching devices configured to selectively couple the first input and the second input together.

[0140] State 6: The apparatus according to any one of States 2-5, wherein: the first amplifier and the second amplifier are configured as amplifiers of a first type; the apparatus also includes: a third amplifier coupled between the output of the first amplifier and the first filter, and a fourth amplifier coupled between the output of the second amplifier and the second filter, the third amplifier and the fourth amplifier being configured as amplifiers of a second type; and the apparatus also includes a second set of one or more switching devices configured to selectively couple the inputs and outputs of the third amplifier and the fourth amplifier together.

[0141] State 7: The apparatus according to any one of States 2-6, wherein the first filter includes: a first RC feedback network selectively or persistently coupled between the input and output of the first amplifier; a first second-stage amplifier coupled to the output of the first amplifier; and a second RC feedback network selectively or persistently coupled between the input and output of the first second-stage amplifier; and the second filter includes: a third RC feedback network selectively coupled between the input and output of the second-stage amplifier; a second second-stage amplifier coupled to the output of the second amplifier; and a fourth RC feedback network selectively coupled between the input and output of the second second-stage amplifier.

[0142] State 8: The apparatus according to any one of States 3-7 also includes: a second group of one or more switching devices configured to selectively couple the first RC feedback network and the second RC feedback network to the capacitors of the capacitor bank. In some embodiments, at least one of the first group of one or more switching devices is configured to be in a closed state, and at least one of the second group of one or more switching devices is configured to be in a closed state.

[0143] State 9: The apparatus according to any one of States 2-8 also includes: a third group of one or more switching devices configured to selectively couple a direct current (DC) power supply to a second amplifier. In some embodiments, at least one of the first group of one or more switching devices is configured to be in a closed state, at least one of the second group of one or more switching devices is configured to be in a closed state, and at least one of the third group of one or more switching devices is configured to be in a closed state.

[0144] State 10: The apparatus according to any one of States 6-9 also includes: a third group of one or more switching devices configured to selectively couple a direct current (DC) power supply to a fourth amplifier. In some embodiments, at least one of the first group of one or more switching devices is configured to be in a closed state, and at least one of the second group of one or more switching devices is configured to be in a closed state, and at least one of the third group of one or more switching devices is configured to be in a closed state.

[0145] State 11: The apparatus according to any one of states 6-9, wherein: the first filter includes a first resistor coupled between a first input of the first filter and a first amplifier; the second filter includes a second resistor coupled between a second input of the second filter and a second amplifier; and the apparatus also includes a third group of one or more switching devices configured to selectively couple the first input and the second input together.

[0146] State 12: The device according to state 11 also includes: a fourth group of one or more switching devices for selectively coupling the second resistor to the second amplifier.

[0147] State 13: The apparatus according to any one of states 6-12, wherein the amplifier of the first type includes a transimpedance amplifier (TIA).

[0148] State 14: The apparatus according to State 13, wherein the amplifier of the second type includes a programmable gain amplifier (PGA).

[0149] Version 15: The apparatus according to any one of versions 6-14 also includes: a first resistor and a second resistor coupled in series between the inputs of a first amplifier and a third amplifier; a first capacitor coupled to a first node between the first resistor and the second resistor; a second capacitor connected between the output and the input of the third amplifier; a third resistor connected to the output of the third amplifier; and a switch configured to selectively connect the third resistor to the input of the third amplifier.

[0150] State 16: The device according to State 15 also includes: another switch configured to selectively connect the third resistor to the first node.

[0151] State 17: According to the apparatus of State 1, the second filter includes an amplifier and a feedback network coupled between the input and output of the amplifier, wherein a first set of one or more switches is configured such that the amplifier and the feedback network can be independently and selectively coupled to the first filter.

[0152] State 18: The apparatus according to any one of states 1-17, wherein the first filter and the second filter include a fundamental frequency filter.

[0153] State 19: The apparatus according to any one of states 1-18, wherein a first filter is coupled to a first antenna and a second filter is coupled to a second antenna.

[0154] State 20: The apparatus according to any one of states 1-19, wherein the first filter and the second filter are both configured as single-pole filters, and the apparatus also includes: a third filter configured as a programmable single-pole / complex-pole filter; and a second set of one or more switching devices configured to selectively route an input signal to the second filter or the third filter.

[0155] State 21: The apparatus according to any one of states 1-20, wherein both the first filter and the second filter are configured as programmable single-pole filters / complex-pole filters.

[0156] Sample 22: A method comprising: operating a first filter to filter a first input signal to generate a first output signal; operating a second filter to filter a second input signal to generate a second output signal; and selectively coupling at least a portion of the second filter to the first filter to filter a third input signal to generate a third output signal.

[0157] State 23: According to the method of State 22, at least a portion of which includes a passive component and an active component.

[0158] State 24: According to the method of State 22, at least a portion of it includes a passive component, but excludes an active component.

[0159] State 25: According to the method of State 22, at least a portion of it includes an active component, but excludes a passive component.

[0160] State 26: The method according to any one of states 22-25, wherein both the first filter and the second filter are configured as single-pole filters, the method also includes: selectively routing the second input signal to a third filter configured as a programmable single-pole / complex-pole filter to generate a fourth output signal.

[0161] State 27: The method described according to any one of states 22-25, wherein both the first filter and the second filter are configured as programmable single-pole / complex-pole filters.

[0162] State 28: The method according to any one of states 22-25, wherein operating the first filter to filter the first input signal to generate the first output signal includes: operating the first filter in a single-pole or complex-pole configuration, wherein operating the second filter to filter the second input signal to generate the second output signal includes: operating the second filter in a single-pole or complex-pole configuration; and wherein selectively coupling at least a portion of the second filter to the first filter to filter the third input signal to generate the third output signal includes: operating the first filter in a single-pole configuration.

[0163] The prior description of the content of this application is provided to enable any person skilled in the art to implement or use it. Various modifications to the content of this application will be apparent to those skilled in the art, and the overall principles defined herein can be applied to other variations without departing from the spirit or scope of the content of this application. Therefore, the content of this application is not intended to be limited to the examples described herein, but is to be given the broadest scope consistent with the principles and novel features disclosed herein.

[0164] 100: Receiver 110-1: Antenna 110-2: Antenna 120-1: Low-noise amplifier 120-2: Low-noise amplifier 130-1: Analog Processing Circuit 130-2: Analog Processing Circuit 140-1I:I-Mixer 140-1Q:Q Mixer 140-2I:I-Mixer 140-2Q:Q-Mixer 150-1: Local Oscillator (LO) 150-2: Local Oscillator 160-1I: I-Fundamental Frequency Filter (I-BBF) 160-1Q:Q-BBF 160-2I: I-Fundamental Frequency Filter (I-BBF) 160-2Q:Q-BBF 200: Programmable Fundamental Frequency Filter 210: Fundamental Frequency Filter (BBF) 212-: Second resistor group 212+: First resistor group 220: Amplifier 230: Second-stage amplifier 250: Baseband Filter (BBF) 252-: Second resistor group 252+: First resistor group 260:TIA 270: Second-stage amplifier 400:TIA 412-: Second resistor group 412+: First resistor group 420: First-stage amplifier 430: Second magnification stage 500: Methods 510: Steps 520: Steps 530: Steps 600: Method 610: Steps 620: Steps 630: Steps 640: Steps 700: Wireless communication equipment 710: Antenna 720: Receiver (or transceiver) 730: Baseband Processing Circuit 800: Receiver 805: Antenna 810: Low-noise amplifier 815: Mixer 820: Local Oscillator 830: Programmable Filter 832: First Single-Pole Fundamental Frequency Filter 834: Second Single-Pole Filter 840: Filter 850: Controller 900: Programmable Baseband (BBF) Filter 910: First BBF 950: Second BBF

[0165] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. An apparatus for filtering a signal, comprising: A first filter includes a first amplifier including a first resistor-capacitor (RC) feedback network coupled between an input and an output of the first amplifier; a second filter includes a second amplifier including a second RC feedback network selectively coupled between an input and an output of the second amplifier; a first group of one or more switching devices configured to selectively couple the first filter to the second filter, wherein the first group of one or more switching devices is configured to selectively couple the inputs and outputs of the first amplifier and the second amplifier together; and a second group of one or more switching devices configured to selectively couple the first RC feedback network and the second RC feedback network to capacitors of a capacitor bank.

2. The apparatus according to claim 1, wherein: The first amplifier includes a first internal amplification stage and a second internal amplification stage, with an output of the first internal amplification stage coupled to an input of the second internal amplification stage; the second amplifier includes a third internal amplification stage and a fourth internal amplification stage, with an output of the third internal amplification stage coupled to an input of the fourth internal amplification stage; and the device also includes a third group of one or more switching devices configured to selectively couple an output of the first internal amplification stage and an output of the third internal amplification stage together.

3. An apparatus for filtering signals, comprising: A first filter, including a first amplifier; A second filter includes a second amplifier; and a first group of one or more switching devices configured to selectively couple the first filter to the second filter, wherein the first group of one or more switching devices is configured to selectively couple the inputs and outputs of the first amplifier and the second amplifier together, wherein: the first filter also includes a first resistor coupled between a first input of the first filter and an input of the first amplifier; the second filter also includes a second resistor coupled between a second input of the second filter and an input of the second amplifier; and the device also includes a second group of one or more switching devices configured to selectively couple the first input and the second input together.

4. An apparatus for filtering signals, comprising: A first filter, including a first amplifier; A second filter includes a second amplifier; and a first group of one or more switching devices configured to selectively couple the first filter to the second filter, wherein the first group of one or more switching devices is configured to selectively couple the inputs and outputs of the first amplifier and the second amplifier together, wherein: the first amplifier and the second amplifier are configured as amplifiers of a first type; the device also includes: a third amplifier coupled between the first amplifier and an output of the first filter, and a fourth amplifier coupled between the second amplifier and the output of the second filter, the third amplifier and the fourth amplifier being configured as amplifiers of a second type; and the device also includes a second group of one or more switching devices configured to selectively couple an input and an output of the third amplifier and an input and an output of the fourth amplifier together.

5. The apparatus according to claim 1, wherein the first filter comprises: A first and second stage amplifier, which is coupled to the output of the first amplifier; and a third RC feedback network, which is selectively or persistently coupled between an input and an output of the first and second stage amplifiers; and the second filter includes: a second second stage amplifier coupled to the output of the second amplifier; And a fourth RC feedback network, which is selectively coupled between an input and an output of the second stage amplifier.

6. The apparatus according to claim 3 also includes a third group of one or more switching devices configured to selectively couple a direct current (DC) power supply to the second amplifier.

7. The apparatus according to claim 4 also includes a third group of one or more switching devices configured to selectively couple a direct current (DC) power supply to the fourth amplifier.

8. The apparatus according to claim 4, wherein: The first filter includes a first resistor coupled between a first input of the first filter and the first amplifier; the second filter includes a second resistor coupled between a second input of the second filter and the second amplifier; and the device also includes a third group of one or more switching devices configured to selectively couple the first input and the second input together.

9. The apparatus according to claim 8 also includes: A fourth group of one or more switching devices to selectively couple the second resistor to the second amplifier.

10. The apparatus according to claim 4, wherein the amplifier of the first type includes a transimpedance amplifier (TIA).

11. The apparatus according to claim 10, wherein the amplifier of the second type includes a programmable gain amplifier (PGA).

12. The apparatus according to claim 4 also includes: A first resistor and a second resistor are coupled in series between an input of the first amplifier and an input of the third amplifier; A first capacitor coupled to a first node between the first resistor and the second resistor; a second capacitor connected between an output and an input of the third amplifier; a third resistor connected to an output of the third amplifier; and a switch configured to selectively connect the third resistor to the input of the third amplifier.

13. The apparatus according to claim 12 also includes another switch configured to selectively connect the third resistor to the first node.

14. The apparatus according to claim 1 also includes a third group of one or more switches configured such that the second amplifier and the second RC feedback network can be independently and selectively coupled to the first filter.

15. The apparatus according to claim 1, wherein the first filter and the second filter include a fundamental frequency filter.

16. The apparatus according to claim 1, wherein the first filter is coupled to a first antenna and the second filter is coupled to a second antenna.

17. The apparatus of claim 1, wherein both the first filter and the second filter are configured as single-pole filters, the apparatus also comprising: A third filter, configured as a programmable single-pole or complex-pole filter; and a second group of one or more switching devices configured to selectively route an input signal to the second filter or the third filter.

18. The apparatus according to claim 1, wherein both the first filter and the second filter are configured as a programmable single-pole filter or a complex-pole filter.

19. A method for filtering a signal, comprising: Operate a first filter to filter a first input signal to generate a first output signal; The method involves operating a second filter to filter a second input signal to generate a second output signal; and selectively coupling at least a portion of the second filter to the first filter to filter a third input signal to generate a third output signal, wherein the at least a portion includes passive components but does not include active components, or wherein the at least a portion includes active components but does not include passive components.

20. The method of claim 19, wherein both the first filter and the second filter are configured as single-pole filters, the method also comprising: The second input signal is selectively routed to a third filter configured as a programmable single-pole or complex-pole filter to produce a fourth output signal.

21. The method of claim 19, wherein both the first filter and the second filter are configured as programmable single-pole or complex-pole filters.

22. The method of claim 21, wherein operating the first filter to filter the first input signal to generate the first output signal comprises: Operating the first filter in a single-pole or complex-pole configuration, wherein operating the second filter to filter the second input signal to generate the second output signal includes: operating the second filter in a single-pole or complex-pole configuration; and wherein selectively coupling at least a portion of the second filter to the first filter to filter the third input signal to generate the third output signal includes: operating the first filter in a single-pole configuration.

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