Broadband tunable RF receiver with high dynamic range and high out-of-band rejection

Abstract

A broadband tunable radio frequency (RF) receiver with a tunable RF bandpass filter (RF BPF) and a passive mixer-first receiver (PMF-Rx) is disclosed. The tunable RF BPF and PMF-Rx cooperate to utilize the intrinsic impedance conversion characteristics of the PMF-Rx to suppress out-of-band interference sources and in-band interference sources at the front end of the receiver, thereby enhancing the signal-to-noise ratio and overall dynamic range of the receiver. In one embodiment of the invention, the tunable RF BPF and PMF-Rx are independently tunable and provide the receiver with the ability to suppress or suppress interference sources that may not be suppressed or suppressed.

Description

Background Art

[0001] A radio frequency (RF) receiver is a basic and essential component of any RF communication system. An RF receiver is responsible for recovering the information carried by the radio waves captured by its antenna and for converting the recovered information into a usable form, such as audio, video or data. Figure 1 1 is a diagram showing the major components of a conventional RF receiver 100. The conventional RF receiver 100 includes: an antenna 102; a receiver (RX) front end, the RX front end including an RF filter 104, a low-noise amplifier (LNA) 106, a mixer 108, and a local oscillator (LO) 110; an analog processing section 112; and a digital back end 114. The RF filter 104 is a bandpass filter that is configured so that the center frequency of its passband is aligned with the desired receive frequency band. The LNA 106 is designed to have a low noise figure and is responsible for amplifying the typical very weak RF signals captured by the receiver's antenna 102, and itself does not introduce significant noise into the system, which would otherwise destroy the receiver's sensitivity. The mixer 108 and the LO 110 operate together to down-convert the amplified RF signal to a lower frequency, or directly to baseband, in which case f LO =f RF , or first downconvert to some lower intermediate frequency f before the final second downconversion to baseband LO (i.e., f LO <f RF ). The analog processing portion 112 typically includes a variable gain amplifier (VGA) to amplify the down-converted signal and a low-pass filter (LPF) to filter out unwanted high-frequency byproducts generated during the down-conversion process. An analog-to-digital converter (ADC) converts the resulting filtered analog waveform into a digital signal for the digital back end 114, which provides additional filtering in the digital domain to help reject or suppress in-band and out-of-band interference sources (i.e., "blockers").

[0002] The RF filter 104 in a conventional RF receiver 100 typically includes a surface acoustic wave (SAW) filter or a bulk acoustic wave (BAW) filter. SAW and BAW filters are desirable from the viewpoint that they can provide high out-of-band (OOB) suppression. However, a significant disadvantage is that they are not tunable. The lack of tunability can be overcome to some extent by employing a set of individually selectable SAW or BAW filters, each of which is a fixed frequency SAW or BAW filter dedicated to a different receive frequency band. However, such an approach is cumbersome, lacks real agility, is not completely effective, and for most cases, is impractical for receivers that must operate at frequencies above 1 GHz.

[0003] Another problem with the conventional RF receiver 100 is that it has no ability to block in-band interferers in any given or selected frequency band at the front end, whether using only a single SAW or BAW filter or a bank of SAW or BAW filters. For example, in-band interferers are caused by nonlinearities in components of the receiver, such as in the LNA 106. They may also occur due to external influences. For example, Figure 2 As shown in , the in-band interference source can be an intrusive signal 206 that is undesirably received from an enemy jammer if the receiver is operating in a military environment, or Figure 3 As shown in , there may be one or more non-intrusive signals 204 that tend to interfere with the desired signal 202 when the receiver is operating in a crowded commercial environment, for example, due to too many communication devices operating in various channels A, B, C, D (desired signal), E within the same receive frequency band. Regardless of the source or cause of the in-band interferer, the conventional RF receiver 100 must rely exclusively on its digital back end 114 to block or attenuate the in-band interferer. This is a major limitation of the conventional RF receiver 100 because multiple in-band interferers among the desired RF signal tend to intermodulate at the front end, resulting in distortion products that increase the noise floor of the receiver 100 and reduce its dynamic range. In-band interferers of sufficient magnitude may also cause the LNA 106 of the receiver to saturate, resulting in a further reduction in the signal-to-noise ratio (SNR) at the front end and a concomitant reduction in channel capacity and data throughput due to the receiver being able to demodulate only lower order modulation formats, such as Figure 4 Conceptually shown in FIG.

[0004] Finally, although SAW and BAW filters can be manufactured to provide high out-of-band (OOB) suppression outside of a given frequency band, because they lack true agility and are inherently fixed frequency devices, OOB suppression for conventional receivers 100 is typically only moderately effective, and in some cases entirely impossible, particularly where the receiver 100 must be tuned across multiple receive bands or across multiple channels within a given receive band. Summary of the invention

[0005] A broadband tunable radio frequency (RF) receiver having a tunable RF bandpass filter (RF BPF) and a passive mixer-first receiver (PMF-Rx) is disclosed. The tunable RF BPF and PMF-Rx operate in coordination, utilizing the inherent impedance conversion characteristics of the PMF-Rx to suppress out-of-band interference sources at the front end of the receiver as well as in-band interference sources, thereby enhancing the signal-to-noise ratio and overall dynamic range of the receiver. In one embodiment of the present invention, the tunable RF BPF and PMF-Rx are independently tunable and provide the receiver with the ability to suppress or repress interference sources that may not be suppressed or repressed.

[0006] Additional features and advantages of the present invention will now be described in detail with reference to the drawings, including a detailed description of the above and other exemplary embodiments of the invention, wherein like reference numerals are used to indicate identical or functionally similar elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a block diagram of a conventional radio frequency (RF) receiver;

[0008] Figure 2 is a frequency domain diagram showing how in-band and out-of-band (OOB) interferers undesirably appear in or near the receive (Rx) band of a desired RF receive signal;

[0009] Figure 3 is a frequency domain diagram illustrating how one or more non-intrusive in-band interferers in one or more channels of a desired Rx frequency band may adversely affect a signal-to-noise ratio (SNR) of a desired RF signal;

[0010] Figure 4 is a series of constellation diagrams that conceptually illustrate how the data rate capability of a receiver is degraded as the SNR in the receiver gradually decreases due to increasing interference levels;

[0011] Figure 5 is a block diagram of an RF receiver according to an embodiment of the present invention;

[0012] Figure 6 It is shown in Figure 5 A schematic diagram of the main components of a passive mixer-first receiver (PMF-Rx) employed in an RF receiver shown;

[0013] Figure 7 It is used to control Figure 6 The N non-overlapping phases of the multiphase local oscillator (LO) clock of the PMF-Rx shown in Timing diagram of

[0014] Figure 8 It is shown Figure 5 How does the impedance conversion characteristic of the PMF-Rx in the RF receiver shown in FIG. 1 cause the baseband low-pass frequency response of the PMF-Rx to be effectively converted to a baseband low-pass frequency response at f LO Frequency domain plot of the RF bandpass filter (BPF) centered at

[0015] Fig. 9 is to show the PMF-Rx itself (i.e., in the absence of Figure 5 A frequency domain diagram of how an in-band interferer falling within the same Rx frequency band as the desired signal but within a different channel) cannot be suppressed or adequately suppressed without the additional assistance of an RF BPF in the receiver as shown in FIG.

[0016] Fig.10 is a composite frequency response diagram according to one aspect of the present invention, which shows Figure 5 How the RF BPF and PMF-Rx in the receiver shown in FIG. cooperate to provide high levels of OOB suppression and in-band interferer rejection over a wide range of tuning frequencies;

[0017] Fig.11 It can be used to implement Figure 5 Schematic diagram of a tunable electrically coupled (ie, capacitively coupled) RF bandpass filter of an RF BPF in an RF receiver shown in;

[0018] Fig.12 It can be used in Figure 5 Schematic diagram of a tunable magnetically coupled (ie, inductively coupled) RF bandpass filter implementing an RF BPF in an RF receiver shown;

[0019] Fig.13 It is shown by Figure 1 A view of the signal flow path of a conventional receiver and various frequency domain spectra at various points along the signal path shown in FIG.

[0020] Fig.14 It shows the Figure 5 A view of the signal flow path of a receiver shown in FIG. 1 and various frequency domain spectra at various points along the signal path;

[0021] Fig.15 is a series of constellation diagrams that conceptually illustrate how the data rate capability of a receiver increases as the SNR of the receiver increases;

[0022] Fig.16 Is Figure 5 The frequency domain diagram of the RF passband provided by the RF BPF and PMF-Rx of the receiver shown in FIG. 1 emphasizes that in one embodiment of the present invention, the center frequency f of the passband of the RF BPF is BPF How to always match the center frequency f of the RF passband provided by the PMF-Rx LO Alignment and synchronization tuning;

[0023] Fig.17 Is Figure 5 The frequency domain diagram of the RF passband provided by the receiver's RF BPF and PMF-Rx is shown, emphasizing that when the center frequency of the RFBPF passband is f BPF and the center frequency f of the RF passband provided by PMF-Rx LO How an OOB interferer cannot be suppressed or adequately suppressed in a particular situation;

[0024] Fig.18 It is emphasized that in one embodiment of the present invention, the center frequency f of the RF BPF passband provided by PMF-Rx BPF and the center frequency f of the RF passband LO How to independently tunable frequency domain plots;

[0025] Fig.19 is a block diagram of an RF receiver according to another embodiment of the present invention;

[0026] Fig. 20 It can be used to implement Fig.19 A simplified diagram of a microcontroller including some or all of the components of the digital processing portion of an RF receiver as shown in;

[0027] Fig.21 According to one embodiment of the present invention Fig. 20 A central processing unit (CPU) of a microcontroller in the embodiment of the present invention is programmed to execute a flowchart of a method for suppressing or suppressing in-band and OOB interference sources that interfere with a desired received signal;

[0028] Fig. 22 is a graph showing the desired signal associated with the OOB jammer and the Fig.21 Frequency domain plot of the assumed initial positioning of the RF passband provided by the RFBPF and PMF-Rx at the beginning of the method shown in;

[0029] Fig.23 It is shown in Fig.21In the context of the method shown in FIG. 1 , the center frequency f of the RF BPF is BPF Tuned away from the center frequency f of the RF passband provided by the PMF-Rx LO How can OOB jammers be effectively suppressed or adequately suppressed in the frequency domain?

[0030] Fig.24 It is shown in Fig.21 In the context of the method shown in , if the center frequency f of the RF BPF is BPF Tuned away from the center frequency f LO and across its full tuning range F BPF,min <f BPF <f BPF,max , cannot suppress or adequately suppress the OOB jammer, then the center frequency f of the RF passband provided by the PMF-Rx LO Frequency domain diagram of how it can be tuned to different channels;

[0031] Fig.25 yes Fig. 20 A flowchart of an alternative method in which a CPU of a microcontroller is programmed to execute to suppress or suppress in-band and OOB interference sources that interfere with a desired received signal; and

[0032] Fig.26 is a diagram of an RF receiver according to another embodiment of the present invention. DETAILED DESCRIPTION

[0033] refer to Figure 5 , shows an RF receiver 500 according to one embodiment of the present invention. The RF receiver 500 (also referred to as "receiver 500" in the following detailed description) includes: an antenna 502; a front end including a tunable RF bandpass filter (RF BPF) 504 and a passive mixer-first receiver (PMF-Rx) 506 controlled by a multi-phase local oscillator (LO) clock generator 508; an analog processing section 510; and a digital processing section 512.

[0034] Antenna 502 is used to convert the modulated RF electromagnetic waves impinging thereon into RF signals. However, then, instead of using a fixed frequency SAW or BAW filter to filter the RF signal (as done in conventional receiver 100), the RF signal is filtered by both tunable RF BPF 504 and PMF-Rx 506. As will become clearer in the detailed description below, PMF-Rx 506 has a dual purpose. It not only serves as a mixer that down-converts the received RF signal to baseband, but also serves inversely as an RF BPF that cooperates with tunable RF BPF 504 to enhance the signal-to-noise ratio (SNR) of the receiver 500 at its front end.

[0035] The analog processing portion 510 of the receiver 500 includes a low pass filter (LPF) and a variable gain amplifier (VGA). The low pass filter (LPF) filters out undesirable high frequency byproducts generated during the down conversion process performed by the PMF-Rx 506.

[0036] At the interface between the analog processing section 510 and the digital processing section 512, an analog-to-digital converter (ADC) 514 samples and digitizes the filtered and amplified analog baseband signal, and then a digital demodulator 516 in the digital processing section 512 recovers the digital data modulated and encoded on the RF carrier on the transmitter side of the communication system.

[0037] Receiver 500 is not limited to operating in any particular communication network or environment or according to any particular modulation format or coding scheme. However, in a particular embodiment of the present invention, receiver 500 is designed to operate in a communication system utilizing orthogonal frequency-division multiplexing (OFDM), in which case digital demodulator 516 includes fast Fourier transform (FFT) 518, symbol demapper 520, and parallel-to-serial converter (i.e., multiplexer) 522, as shown in FIG. Figure 5 As will be appreciated by those of ordinary skill in the art, FFT 518 is used to convert the digitized time-domain OFDM symbols produced at the output of ADC 510 into a plurality of frequency-domain subcarriers; symbol demapper 520 demodulates the plurality of subcarriers to recover the digital data encoded in each subcarrier; and P / S converter 522 multiplexes the resulting demapped subcarrier digital data into a single serial data stream that replicates the original high-speed data stream introduced into the RF transmitter at the transmitter side of the communication system. Preferably, FFT 518, symbol demapper 520, and P / S converter 522 are configured in a field programmable gate array (FPGA) or encoded in software as a set of computer program instructions executed by an associated microcontroller.

[0038] Usually, if Figure 6 As shown, PMF-Rx 506 (600) includes N parallel branches (or N "paths") connected between output node 602 and ground, where N is an integer greater than or equal to 2. (In this example, N = 4, but it can be higher). Each branch includes a capacitor 604 and a switch 606, which preferably uses a capacitor with a low on-resistance R SWThe switch 606 is controlled to follow the multi-phase LO clock generated by the multi-phase LO clock generator 508 (see Figure 7 ) of N non-overlapping phases The multi-phase LO clock generator 508 is also tunable in one embodiment of the invention, like the RF BPF 504, by sequentially and one-at-a-time cycling. Switching the switches 606 in this manner allows the switches 606 to collectively function as a passive mixer that down-converts the RF spectrum of the input RF signal directly to baseband, where the input RF signal is then directly transmitted by one of the N branches (R) of the PMFR-Rx 506. ANT +R SW ) and C are low pass filtered and then ultimately processed by the analog processing portion 510 and the digital processing portion 512 of the receiver 500.

[0039] The commutating action of the switched capacitors 604 not only aids the down-conversion process but also causes each capacitor 604 to present an effective impedance of 1 / j[(ω-ω LO )C BB ](As long as(R ANT +R SW )xC>>1 / f LO ). Therefore, the low-pass filter (LPF) response of the PMF-Rx506 at baseband effectively converts the LPF at baseband to a frequency f at the LO. LO RF BPF centered on Figure 8 Thus, the PMF-Rx 600 not only acts as a passive mixer to down-convert the input RF signal to baseband, but also acts as a passive mixer to return the shaped spectrum back to its original RF center frequency f LO This impedance conversion characteristic of PMF-Rx 600 is exploited by receiver 500 to provide a higher level of in-band interference source suppression at the front end than can be achieved in conventional radio receiver 100, thereby enhancing the signal-to-noise ratio (SNR) of receiver 500 at its front end and, therefore, its overall dynamic range.

[0040] f LOThe -3dB bandwidth (BW) of the impedance transformation frequency response of the surrounding PMF-Rx-700 is inversely proportional to the number of branches N and the capacitance C of the switch capacitor 704. Considering this dependency and the fact that most network operators divide their Rx band into multiple channels, in one embodiment of the present invention, the number of branches N in the PMF-Rx 506 and the capacitance C of the PMF-Rx capacitor 604 are selected so that the -3dB BW of the PMF-Rx-506 (600) passband is comparable to (e.g., substantially equal to, slightly wider or slightly narrower than) the bandwidth of a single channel.

[0041] In some advanced receiver applications, the PMF-Rx-506 (700) itself may not provide sufficient suppression or rejection of in-band interferers of adjacent desired RF signals (e.g., in-band interferers 902 falling within the same Rx band 904 as the desired signal 906 but within a different receive band channel (e.g., an adjacent channel), such as Fig. 9 (Note: for the purposes of this disclosure, the term "interference source" is synonymous with the term "blocking source" and also has a meaning that includes the term "interferer"). To address this issue, the receiver 500 is also equipped with a tunable RF BPF 504. Utilizing the impedance conversion characteristics of the PMF-Rx 506, the tunable RF BPF 504 and the PMF-Rx 506 operate in coordination to suppress or repress in-band interference sources that would otherwise not be suppressed or adequately repressed if only a single filter in the filter were used. Fig.10 is a simplified composite frequency response graph illustrating this synergistic effect and how the combined frequency response of the tunable RF BPF 504 and the PMF-Rx 506 enhances the in-band interferer suppression capability of the receiver 500. Fig.10 The first circle 1002 and the second circle 1004 in FIG. 5 highlight the filtering contributions provided by the PMF-Rx 506 and the tunable RF BPF 504, respectively (according to a particular exemplary embodiment of the receiver 500), and how each filter individually shapes the spectrum of the overall RF filter response. Due to the impedance transformation characteristics of the PMF-Rx 506, it can be seen that the PMF-Rx 506 provides up to 20 dB of adjacent channel rejection with the width of a single channel, and the center frequency f of the tunable RF BPF 504 is BPF and the LO frequency f of the PMF-Rx 506 LO Aligned, it can be seen that the tunable RF BPF 504 provides 20dB-30dB of bandwidth rejection across the entire Rx band ("Band 1" in the figure).

[0042] The tunable RF BPF 504 may be implemented in various ways. In one embodiment of the present invention, the tunable RFBPF includes two or more electrically coupled (ie, capacitively coupled) LC tank circuits, similar to Fig.11 , and another embodiment includes two or more magnetically coupled (ie, inductively coupled) LC tank circuits, similar to Fig.12 In yet another embodiment of the present invention, the tunable RF BPF 504 includes a tunable high-Q coupled cavity BPF formed in a substrate-integrated waveguide (SIW), which is similar to the evanescent mode cavity filters described in "Substrate Integrated Evanescent-Mode Cavity Filter With a 3.5 to 1 Tuning Ratio" by S. Moon et al. (in IEEE Microwave and Wireless Components Letters, Vol. 20, No. 8, pp. 450-452, August 2010) and "High-Q Fully Reconfigurable Tunable Bandpass Filters" by H. Joshi et al. (in IEEE Transactions on Microwave Theory and Techniques, Vol. 57, No. 12, pp. 3525-3533, December 2009) (both of which are incorporated herein by reference). In one specific implementation of the receiver 500 utilizing the SIW coupled cavity approach, the tunable RF BPF 504 has a tuning ratio of 2.5 or greater, at f BPF,min <f BPF <f BPF.max =600MHz<f c It is continuously and dynamically tunable within a tuning range of <3.7 GHz and provides 20 dB or greater broadband interference rejection over the entire tuning range.

[0043] To further illustrate how the tunable RF BPF 504 and the PMF-Rx 506 cooperate to enhance the SNR of the receiver 500 at its front end and increase its overall dynamic range that can be achieved in a conventional RF receiver 100, the following description will now be made of the embodiment of the present invention. Fig.13 and Fig.14 Make a reference. Fig.13 Shown by Figure 1 The signal flow path of the conventional RF receiver 100 is shown, and Fig.14 Shown by Figure 51 and 10. The two figures also show the frequency spectra at different points along their respective signal paths. For the purposes of this example, it is assumed that the two receivers are co-located in the same environment, specifically a crowded urban environment, where the desired (i.e., expected) RF signal f2 arriving at the receiver antennas 102 and 502 is weaker (lower power) than both the in-band blocker f1 and the OOB blocker f3. It is further assumed that the received power of the in-band blocker f1 is 20 dB greater than the received power of the desired signal f2, the received power of the OOB blocker f3 is 50 dB greater than the received power of the desired signal f2, and the receiver 500 has a signal path similar to Fig.10 , while the conventional RF receiver 100 has a typical RF filter response of a fixed frequency SAW filter.

[0044] Regarding the conventional RF receiver 100 ( Fig.13 ), the fixed frequency SAW filter 104 operates to suppress the OOB blocker f3 by 40 dB. Next, the LNA 106 amplifies all RF signals f1, f2, and f3 by 20 dB. Once down-converted to baseband, the analog processing section 112 amplifies the in-band baseband signals (i.e., the desired down-converted signal f2' and the down-converted in-band blocker f1') by 30 dB, and low-pass filters the amplified results to further suppress the down-converted OOB blocker f3' by -40 dB. Finally, at the digital back end 114, digital filtering is employed to further suppress the baseband in-band blocker f1' relative to both the desired baseband signal f2' and the baseband OOB blocker f3' (both are -60 dB). Fig.13 The final RF spectrum in the upper right corner reveals a final SNR of 40dB.

[0045] Now, regarding the receiver 500 ( Fig.14), the tunable RF BPF 504 operates to suppress the OOB blocking source f3 by 20dB. Next, the frequency conversion BPF provided by the PMF-Rx 506 filters the filtering result again. In doing so, the receiver 500 utilizes the impedance conversion characteristics of the PMF-Rx 506 to improve the SNR of the desired signal f2 relative to the in-band blocking source f1 by 20dB. Therefore, after being down-converted by the PMF-Rx 506 and amplified and low-pass filtered in the analog processing section 510, the in-band blocking source f1' and the desired baseband signal f2' at the baseband have substantially the same power level. Finally, after digital processing in the digital processing section 512, the final SNR is considered to be 60dB, which is +20dB higher than the 40dB SNR achieved by the conventional RF receiver 100. Thus, not only is the desired signal f2' relative to the noise floor in the receiver 500 of the present invention 100 times greater than what can be achieved at the output of a conventional RF receiver 100, but the receiver 500 also provides comparable OOB suppression performance over its entire tuning range. The high SNR provides the receiver 500 with the ability to demodulate higher order modulation formats (e.g., 64-QAM, 256-QAM, 1024QAM, 4096-QAM) (see Fig.15 ) and increases the achievable data rate by 64 times or more over the achievable data rate achievable by the conventional RF receiver 100.

[0046] In most cases, when the center frequency f of the tunable RF BPF 504 is BPF is tuned to the center frequency f of the RF frequency response provided by the PMF-Rx 506 LO and is aligned with it (i.e., when f BPF =f LO When ( ), sufficient in-band interference source suppression and sufficient OOB interference source suppression can be achieved, such as Fig.16 However, alignment of the two center frequencies does not always ensure optimal interference source suppression or the level of suppression or suppression that is required or may be desired. For example, if an unusually strong interferer (e.g., a high power jammer) happens to fall substantially within the passband of either filter, the combined filtering effect provided by the tunable RF BPF 504 and PMF-Rx 506 may simply not suppress the in-band interferer to the required or desired degree. Or, as Fig.17 As shown in , if the desired signal 1702 is in a channel 1706 at or near the Rx band edge 1708 and an unusually strong interferer (e.g., a high power jammer 1704 in this example) happens to be in close proximity to the band edge 1708 and also falls substantially within the passband of the tunable RF BPF 504, then if the center frequencies are aligned (i.e., if f BPF =f LO), then the suppression or full suppression of the OOB jammer 1704 may not be fully effective. In either case, if the two center frequencies are tuned to different frequencies (i.e., misaligned (f BPF ≠f LO )), then the interference suppression device 1704 can be better implemented. To facilitate this operational capability, in one embodiment of the present invention, the tunable RF BPF 504 and PMF-Rx 506 are designed so that they are independently tunable, or more specifically, so that the center frequencies f of their respective RF passbands are BPF and f LO are independently tunable, such as Fig.18 shown.

[0047] Fig.19 It is shown Figure 5 The receiver 500 shown in FIG. 5 can be modified to provide a view of one way to detect and suppress an abnormally strong interferer (e.g., a high power jammer) when the tunable RF BPF 504 and PMF-Rx 506 cannot suppress or sufficiently suppress the abnormally strong interferer when their passbands are aligned. In addition to including Figure 5 In addition to all the components of receiver 500 shown in FIG. 1 , receiver 1900 also includes a signal analyzer 1908, an RF input power (P in ) Monitor 1910, Rx channel selector 1912, f BPF adjuster 1914 and Δf counter 1916. Signal analyzer 1908 operates to measure the signal quality (e.g., its error vector magnitude (EVM), bit error rate (BER), or other signal quality figure) of the Rx signal generated at the output of demodulator 1904. in Monitor 1910 monitors the RF input power P of the received RF signal. in , preferably before being amplified by a VGA in the analog processing section 510. As explained in more detail below, the measured EVM (or measured BER or other measured signal quality figure of merit) and the monitored RF input power P in is used to detect and determine whether an abnormally strong interference source (e.g., a high-power jammer) may be present and interfering with a desired Rx signal (such as, Fig.17 The OOB jammer 1704 in the receiving. BPF The adjuster 1914 is used to adjust the center frequency f of the tunable RF BPF 504. BPF Adjust to move away from f LO, incrementally adjusting some small changes in frequency Δf in an attempt to suppress harmful high power interferers. And Δf counter 1916 is used to adjust the frequency Δf that the tunable RF BPF 504 has changed from the Rx channel frequency f LO The number of tune-offs is counted and a determination is made as to whether the tunable RF BPF 504 has been tuned (ie, swept) through its entire tuning range f in an attempt to suppress harmful high power interferers. BPF，min <f BPF <f BPF，max .

[0048] According to one embodiment of the present invention, the signal analyzer 1908, P in Monitor 1910, Rx channel selector 1912, f BPF Some or all of the adjuster 1914 and the Δf counter 1916 (ie, Fig.19 Some or all of the various components in the dashed box 1906 in FIG. 1 ) (which may be alternatively or collectively referred to as a "controller") and optionally the demodulator 1904 are implemented in an FPGA. In another embodiment of the invention, the controller (and possibly the demodulator 1904) are formed entirely in hardware as an application specific integrated circuit (ASIC). In yet another embodiment, the controller (and possibly the demodulator 1904) are encoded in software (computer program instructions) and stored as firmware in the program memory 2006 of the microcontroller 2002, such as Fig. 20 According to the latter method, the CPU 2004 of the microcontroller retrieves computer program instructions from the program memory 2006 and executes the computer program instructions accordingly using the random access memory (RAM) 2008 of the microcontroller. The computer program instructions are instructions that direct the following processing: how the CPU 2004 calculates the EVM (or other signal quality figure of merit) of the demodulated baseband signal generated by the demodulator 1904; how the CPU 2004 adjusts the RF input power P in Converted to digital form and determined whether it exceeds a predetermined maximum RF input power P indicating the possible presence of an abnormally strong interference source max ; How does CPU 2004 generate settings and independently control f BPF and f LO and how the CPU 2004 counts to determine whether the tunable RF BPF 504 has been tuned within its entire tuning range f BPF，min <f BPF <f BPF，max to suppress or repress sources of harmful interference.

[0049] Fig.212 is a flow chart showing a method 2100 performed by the CPU 2004 when it performs these various operations to suppress or suppress an abnormally strong interferer. The method 2100 is applicable whether the abnormally strong interferer is an in-band interferer that falls within the Rx band of the receiver or an OOB interferer that falls outside the Rx band but near the edge of the Rx band, such as the above referenced Fig.17 For illustrative purposes, the latter case is assumed in the following description of method 2100. It is further assumed that the abnormally strong interference source is an intrusive signal, specifically a high-power jammer 2204, but method 2100 is equally applicable to other types of interference sources, regardless of whether they are intrusive or non-intrusive. Finally, it is assumed that before method 2100 begins, the center frequency f of the tunable RF BPF 504 is BPF，1 Initially with the center frequency f of the RF passband provided by the PMF-Rx506 LO，1 Alignment. The initial condition f LO，1 =f BPF exist Fig. 22 Indicated in.

[0050] During the first step 2102 of the method 2100, the CPU 2004 continuously monitors the RF input power P of the RF signal received by the receiver 1900. in (Preferably, after it has been filtered by the tunable RF BPF 504 and PMF-Rx 506 but before it is amplified by the VGA in the analog processing section 510). Note that the RF input power P in The RF power of not only the desired signal 2202 is included, but also the RF power of all other undesired signals that are not suppressed by the combined filtering effect of the tunable RF BPF 504 and the PMF-Rx 506, including the RF power of the jammer 2204 that is also present and within the passband of the tunable RF BPF 504. Next, at decision 2104, the CPU 2004 determines the RF input power P of the received signal. in Is it greater than the predetermined maximum RF input power P max If CPU 2004 determines that P in >P max (Yes ("Y") at decision 2104), then the determination is that a jammer may be present and interfering with the desired Rx signal (e.g., OOB jammer 2004 is interfering with the desired Rx signal 2202, such as Fig. 22 In order to determine the high P inWhether attributable to the interferer or, alternatively, to the desired Rx signal 2202 itself (such as might be the case if the source transmitter happens to be very close to the receiver 1900), at step 2104, the CPU 2004 measures and calculates the EVM (or BER or other signal quality figure of merit) of the demodulated signal produced at the output of the demodulator 1904. If the measured / calculated EVM is not greater than a predetermined error vector magnitude minimum value EVM min In other words, if a no ("N") is produced at decision 2108, then the CPU 2004 concludes that a jammer is unlikely to exist, and the method 2100 ends or returns to step 2102. On the other hand, if the CPU 2004 determines at decision 2108 that the EVM <EVM min ("Y" at decision 2108), then CPU 2004 concludes that an interference source (in this example, jammer 2204) may be present and interfering with desired signal 2202. In order to suppress or at least adequately suppress harmful jammer 2204, at step 2110, CPU 2004 directs tunable RF BPF 504 to move its center frequency away from the center frequency f of the PMF-Rx 506 RF passband. LO Then, at step 2112, CPU 2004 again measures and calculates the EVM of the demodulated signal produced at the output of demodulator 1904. If the tuning of tunable RF BPF 504 away from the center frequency f of the PMF-Rx 506 RF passband performed at step 2110 is LO.1 Successfully reduced the EVM to below EVM min In other words, if at decision 2116 the CPU 2004 determines that EVM < EVM min ("Y" at decision 2114), CPU 2004 concludes that jammer 2204 has been suppressed or at least sufficiently neutralized, and method 2100 branches back to step 2102, where CPU 2004 again monitors the RF input power P in For the purpose of detecting the possible occurrence of new jammers. On the other hand, if at decision 2114, CPU 2004 determines that EVM is still greater than EVM min ("N" at decision 2114), the CPU 2004 directs the tunable RF BPF 504 to adjust its center frequency even further away from the center frequency f of the PMF-Rx 506 RF passband response. LO，1 An additional frequency increment Δf is added to additionally suppress or at least sufficiently overwhelm the harmful interferer 2204. This process (step 2112, decision 2114, and step 2118) is repeated until: 1) the EVM calculated and measured by the CPU 2004 becomes less than the EVM min(The jammer 2204 is successfully suppressed or sufficiently suppressed, e.g. Fig.23 ); or 2) the tunable RF BPF 504 has been tuned (swept) throughout its tuning range, but the jammer 2204 cannot be successfully suppressed or adequately suppressed ("Y" at decision 2116). If the latter occurs ("Y" at decision 2116), the amount of adjustment of the tunable RF BPF 504 will not cause the jammer 2204 to be suppressed or adequately suppressed, so at step 2120, the CPU 2004 directs the PMF-Rx 506 to tune to the new LO frequency f LO，2 centered at different channels 2406 and directing the tunable RF BPF 504 to adjust to different center frequencies f BPB，3 ,like Fig.24 As shown in , the new desired signal 2302 is then sufficiently far away from the jammer 2204 so that the jammer 2204 can no longer substantially interfere. After step 2120 is completed, the method 2100 ends or returns to the first step 2102, where the CPU 2004 again monitors the RF input power P in To detect the possible occurrence of new interference sources.

[0051] It should be mentioned that, depending on the application in which the 1900 is used, the RF input power P in Monitoring step 2102 and decision 2104 may not be necessary or may not be used as a 100% reliable indicator of the possible presence of 2204. For example, if the interference source is not particularly strong to exceed P max , but with sufficient RF power relative to the RF power of the desired Rx signal 2202, it may occur that significant distortion still occurs despite the combined filtering of the tunable RF BPF 504 and PMF-Rx 506. In such an application, detecting the presence of a possible interferer may be better achieved without step 2102 and decision 2104. In other words, P will not be required in the receiver 1900. in Monitor 910, and steps 2102 and decision 2104 in method 2100 may be omitted, such as Fig.25 As illustrated in the modified method 2500 shown in FIG. 2500 , by using this modification, the EVM of the demodulated signal is simply continuously compared with the reference threshold EVM. min To fully serve the detection of the possible existence of interference source 2204.

[0052] It should also be emphasized that receiver 500 and receiver 1900 are not limited to any particular application and may be applicable to substantially any RF communication in which sources of interference, whether intentional or unintentional, are of concern. For example, receiver 500 or 1900 may be suitable for use as an RF receiver in a Wi-Fi router or wireless access point, as an RF receiver in a Bluetooth device in a personal area network, or as an RF receiver in a cellular handset or telecommunications base station. Fig.26 1900 is shown as one way in which, for example, the receiver 1900 may be adapted for use in a telecommunications base station. According to this exemplary embodiment of the invention, the controller of the receiver 2600 includes a base station master controller 2602 (e.g., a computer or additional microcontroller configured to act as a master device) and a local microcontroller 2604 configured to act as a slave device, rather than just a single local microcontroller 2002. The local microcontroller 2604 tunes the tunable RF BPF 504 and adjusts the frequency f of the multi-phase LO clock generator 508 of the PMF-Rx 506. LO , but unlike the local microcontroller 2002 in the receiver 1900, the tuning and adjustment are initiated and controlled under the command and control of the base station main controller 2602. In addition, when the microcontroller 2002 is in the receiver 1900, the base station main controller 2602 is programmed to perform those tasks instead of monitoring the RF input power P in And the signal quality of the demodulated signal is calculated locally.

[0053] Although various embodiments of the present invention have been described, they have been presented by way of example and not limitation. It will be apparent to those skilled in the relevant art that various changes in form and detail may be made to the exemplary embodiments without departing from the true spirit and scope of the present invention. Therefore, the scope of the present invention should not be limited by the details of the exemplary embodiments, but should be determined by the appended claims, including the full range of equivalents granted by these claims.

Claims

1. A radio frequency (RF) receiver, comprising: antenna; A baseband processing part, wherein the baseband processing part includes an analog processing part and a digital processing part; as well as a receiver front end, the receiver front end being coupled between the antenna and the baseband processing section, the receiver front end comprising a tunable RF bandpass filter RF BPF coupled to the antenna and a passive mixer priority receiver PMF-Rx coupled between an output of the tunable RF BPF and an input of the baseband processing section, The PMF-Rx is configured to function both as a mixer for down-converting the received RF signal to baseband and as a second RF BPF that operates in conjunction with the tunable RF BPF to enhance the signal-to-noise ratio of the receiver front end.

2. The RF receiver according to claim 1, wherein: The tunable RF BPF has a center frequency of f BPF The second RF BPF provided by the PMF-Rx has a center frequency of f LO The passband, the f BPF and f LO Can be tuned independently.

3. The RF receiver according to claim 1, wherein: The PMF-Rx is capable of tuning on multiple channels within a given Rx frequency band, and the PMF-Rx and the tunable RF BPF are operable to reject or suppress out-of-band interference sources that fall outside the given Rx frequency band.

4. The RF receiver according to claim 3, wherein: The bandwidth of the passband of the second RF BPF provided by the PMF-Rx is comparable to the width of a single channel, and the bandwidth of the passband provided by the tunable RF BPF is wider than the bandwidth of the passband of the second RF BPF provided by the PMF-Rx.

5. The RF receiver according to claim 4, wherein: The tunable RF BPF is bandwidth tunable and is also operable to reject or suppress in-band interferers that fall within the given Rx frequency band but outside the passband of the second RF BPF provided by the PMF-Rx.

6. The RF receiver according to claim 5, wherein: The tunable RF BPF passband has a center frequency f BPF , the passband of the second RF BPF provided by the PMF-Rx has a center frequency f LO , and f BPF and f LO Can be tuned independently.

7. The RF receiver according to claim 1, wherein: The tunable RF BPF is continuously and dynamically tunable.

8. The RF receiver of claim 2, further comprising a controller configured to detect and determine whether an interference source is present and interfering with reception of the received RF signal.

9. The RF receiver according to claim 8, wherein: The controller includes a signal analyzer and a BPF The signal analyzer is configured to measure the signal quality of the demodulated digital baseband signal generated by the digital processing part, and when the controller determines that the signal quality of the demodulated digital baseband signal has crossed a predetermined signal quality threshold, the f BPF The adjuster adjusts the tunable RF BPF to different center frequencies.

10. The RF receiver according to claim 8, wherein: The controller further comprises: An RF input power monitor configured to monitor the RF input power P of the received RF signal in And the RF input power P in With the predetermined maximum RF input power P max Make comparisons; a signal analyzer configured to measure a signal quality of a demodulated digital baseband signal generated by the digital processing portion; and f BPF regulator, in which the controller determines P in >P max and the signal quality of the demodulated digital baseband signal has crossed a predetermined signal quality threshold, the f BPF The adjuster adjusts the tunable RF BPF to different center frequencies.

11. The RF receiver of claim 1, wherein: The tunable RF BPF does not include an acoustic wave type filter or an acoustic wave type filter bank.

12. A method of suppressing or suppressing an interference source received by a radio frequency (RF) receiver, the method comprising: RF filtering of the RF input signal by a tunable RF band pass filter RF BPF; utilizing the impedance conversion characteristics of a passive mixer priority receiver PMF-Rx and using the PMF-Rx to enhance the RF filtering; and The resulting RF filtered RF signal is down-converted to baseband using the PMF-Rx.

13. The method according to claim 12, wherein: The tunable RF BPF has a center frequency of f BPF The RF passband provided by the PMF-Rx has a center frequency f LO , and f BPF and f LO Can be tuned independently.

14. The method according to claim 13, further comprising: measuring the signal quality of a baseband signal produced by down-converting the filtered RF signal to baseband; as well as The tunable RF BPF f BPF Tuning to different center frequencies to suppress or overwhelm interfering sources that distort the desired RF Rx signal contained within the RF input signal.

15. The method according to claim 14, wherein: Measuring the signal quality of the baseband signal includes: measuring and calculating the error vector magnitude (EVM) of the baseband signal.

16. The method according to claim 14, wherein: The PMF-Rx is capable of being tuned across multiple channels within a given Rx frequency band, and the tunable RF BPF is continuously and independently tunable relative to the tuning of the PMF-Rx.

17. The method according to claim 16, further comprising: If the f of the tunable RF BPF is BPF If tuning to a different center frequency does not result in the interference source being suppressed or sufficiently overwhelmed, the PMF-Rx is tuned to a different channel.

18. The method according to claim 13, further comprising: After the RF input signal has been filtered by the tunable RF BPF and the PMF-Rx, the RF input power P of the RF input signal is monitored. in ; The RF input power P in With the maximum RF power reference P max Make comparisons; measuring a signal quality of a baseband signal obtained by down-converting the filtered RF signal to baseband; comparing the measured signal quality to a predetermined signal quality threshold; as well as If P in >P max and the measured signal quality crosses the predetermined signal quality threshold, the f of the tunable RFBPF is set to BPF Tuning to different center frequencies to suppress or overwhelm interfering sources that distort the desired RF Rx signal contained within the RF input signal.

19. The method according to claim 18, wherein: The RF passband provided by the PMF-Rx is tunable across multiple channels within a given Rx frequency band, and the tunable RF BPF is continuously and independently tunable relative to the tuning of the PMF-Rx.

20. The method according to claim 19, further comprising: If the f of the tunable RF BPF is BPF If tuning to a different center frequency does not result in the interference source being suppressed or sufficiently overwhelmed, the PMF-Rx is tuned to a different channel.

21. The method according to claim 12, wherein: The RF passband provided by the PMF-Rx is tunable across multiple channels within a given Rx frequency band, and the tunable RF BPF is continuously and independently tunable relative to the tuning of the PMF-Rx.

22. The method according to claim 21, wherein: The bandwidth of the RF passband provided by the PMF-Rx is comparable to the width of a single channel, and the bandwidth of the passband of the tunable RF BPF is wider than the RF passband provided by the PMF-Rx.

23. The method according to claim 22, wherein: The tunable RF BPF is bandwidth tunable and is operable to reject or suppress in-band interferers that fall within the given Rx frequency band but outside the RF passband provided by the PMF-Rx.

24. The method according to claim 12, wherein: The tunable RF BPF does not include an acoustic wave type filter or an acoustic wave type filter bank.

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