Low power receiver with intermediate frequency (IF) detection and local oscillator (LO) frequency correction

Abstract

A method, system, and apparatus for a wireless receiver with intermediate frequency (IF) detection and local oscillator (LO) frequency correction is disclosed. According to one aspect, the wireless receiver is configured to include a LO configured to generate a local oscillator signal, the LO not being phase-locked. The wireless receiver includes a mixer configured to mix the LO signal with an amplitude shift keying (ASK) modulated signal to produce an intermediate frequency (IF) signal. The wireless receiver also includes a tuning circuit configured to estimate a frequency of the IF signal and tune the LO according to the estimated intermediate frequency, and tune the LO to compensate for IF frequency drift. The IF frequency estimation is based on a correlation of the signal in a plurality of frequency bins of a fast Fourier transform (FFT) of the IF signal.

Description

Technical Field

[0001] This disclosure relates to wireless communication, and more particularly to a low-power receiver with intermediate frequency (IF) detection and local oscillator (LO) frequency correction. Background Technology

[0002] The 3rd Generation Partnership Project (3GPP) has developed and is developing standards for fourth-generation (4G) (also known as Long Term Evolution (LTE)) and fifth-generation (5G) (also known as New Radio (NR)) wireless communication systems. Among other features, such systems provide broadband communication between network nodes (e.g., base stations) and mobile wireless devices (WDs), as well as communication between network nodes and between WDs. 3GPP is also developing standards for sixth-generation (6G) wireless communication networks.

[0003] To conserve power, when there is no downlink (DL) / uplink (UL) data traffic to or from the wireless device, the wireless device (e.g., a 3GPP WD) will enter an idle / inactive mode. The WD needs to wake up during a discontinuous reception (DRX) cycle to receive paging information from the radio node. For each wake-up, before paging reception, the WD must perform frequency synchronization to correct frequency drift in its clock system, thereby tuning its local oscillator (LO) frequency to match the carrier frequency transmitted from the radio node. The radio node can be a base station, an access point (AP), or another WD.

[0004] For NR WD, upon waking from an idle / inactive state, it performs frequency synchronization using Synchronization Signal Block (SSB) signaling. The radio node transmits the SSB with a specific bandwidth (BW) (e.g., 5G mmW SSB BW = 29MHz) and repetition rate. The WD detects a reference signal, calculates the phase shift between two consecutive reference symbols or blocks to estimate the frequency error, and adjusts its local crystal oscillator (XO) frequency or phase-locked loop (PLL) divider. The frequency synchronization process incurs energy consumption overhead and time delay. In particular, for 5G mmW WD, the energy consumption overhead of frequency tracking can be very expensive.

[0005] To overcome these problems, such as Figure 1 and 2As shown in the examples, methods and low-power topologies have been proposed to reduce overall power consumption by using self-oscillators instead of PLLs. These are not without drawbacks. In transmitters, receivers, or transceivers, uncertainties about the intermediate frequency (IF) can lead to signal loss if the IF falls outside the IF filter bandwidth. In low-power receivers using self-oscillators, the oscillator frequency may drift, eventually resulting in similar signal loss. There is no way to compensate for or control this frequency drift. If the low-power receiver also uses a correlator, no peak may be observed in the correlation window if the signal frequency falls outside the IF filter passband. This means there is no possible frequency compensation. Summary of the Invention

[0006] Some embodiments advantageously provide methods and low-power receiver implementations with intermediate frequency (IF) detection and local oscillator (LO) frequency correction.

[0007] A low-power solution for detecting IF frequency drift and tuning a self-excited oscillator to compensate for the drift is disclosed. Some embodiments use the self-excited oscillator to improve low-power receiver topologies and improve spectral efficiency and power consumption at the network level.

[0008] In some embodiments, a hardware block including an analog IF detector and an LO corrector, as well as a control block, is configured to detect and correct potential IF frequency drift introduced by a self-excited oscillator of the LO, which serves as a low-power receiver.

[0009] By detecting the IF frequency and tuning the LO accordingly, the IF signal frequency can be contained within the passband of the IF filter. This eliminates signal loss that occurs in the filter when the signal falls outside the IF filter bandwidth.

[0010] In low-power receiver topologies, it's possible to keep the IF signal within the IF filter bandwidth, making baseband clock drift detectable. For low-power receivers with correlators, the LO can be tuned so that sequence correlation peaks can be observed within the correlation window. Furthermore, for low-power receivers with correlators, coarse frequency synchronization can be employed.

[0011] In some embodiments, a tuned LO can be used to transmit signals using a low-power transmitter and establish low-data-rate communication between low-power devices, potentially within a cluster of devices. Correcting LO frequency drift can potentially bring the transmission closer to the receiving frequencies of other receivers, thereby achieving energy savings at the network scale.

[0012] Low-power receivers configured according to the principles disclosed herein can be used in uncertain frequency environments, such as low-power device clusters, and can provide information about network-level interference and other causes of IF uncertainty sources.

[0013] According to one aspect, the wireless receiver includes a local oscillator (LO) configured to generate a local oscillator signal, which is not phase-locked. The wireless receiver includes a mixer configured to mix the local oscillator signal with a received amplitude shift keying (ASK) modulated signal to generate an intermediate frequency (IF) signal. The wireless receiver also includes tuning circuitry configured to estimate the frequency of the IF signal and tune the LO to compensate for IF frequency drift. The tuning circuitry includes an analog fast Fourier transform (FFT) circuitry configured to perform a fast Fourier transform (FFT) of the IF signal to obtain signals in multiple frequency bins, the IF frequency estimation being based on the correlation between the signals in the multiple frequency bins and a reference sequence.

[0014] According to this aspect, in some embodiments, the LO is tuned according to a digital control signal based at least in part on the FFT of the IF signal. In some embodiments, the wireless receiver includes an envelope detector for detecting the envelope of the FFT of the IF signal and a baseband filter for filtering the detected envelope. In some embodiments, the wireless receiver includes at least one correlator configured to correlate a sequence detected in the filtered detection envelope of the FFT of the IF signal with a reference sequence. In some embodiments, the tuning circuit is configured to tune the LO such that a correlation peak appears in a frequency bin associated with at least one correlator. In some embodiments, the FFT is disabled when no peak is observed. In some embodiments, at least one correlator (90) is configured to perform a coarse frequency estimation using a first-width FFT frequency window, followed by a fine-grained frequency estimation using a second-width FFT frequency window narrower than the first width. In some embodiments, the ASK modulation signal is an on-off keyed OOK modulation signal, wherein each of the at least one correlator is configured to search for the on-off keyed OOK modulation signal in different frequency bins of the FFT. In some embodiments, each correlator of the at least one correlator performs a correlation between a reference sequence and a sequence associated with a different frequency bin of the FFT of the IF signal. In some embodiments, the tuning circuitry is configured to determine the frequency bin of the FFT associated with the strongest correlation peak. In some embodiments, the tuning circuitry is configured to tune the LO to a frequency that, when mixed with a received signal, provides an IF signal at a frequency within the operating bandwidth of the IF filters of the receiver chain of the wireless receiver. In some embodiments, for each of a plurality of frequency bins, the wireless receiver includes an envelope detector and a baseband filter for detecting and filtering the signal envelope in the frequency bin. In some embodiments, the wireless receiver is included in a wireless device.

[0015] According to another aspect, a method is provided for compensating for frequency drift of a local oscillator (LO) in a wireless receiver configured to provide a tuning control signal to the LO. The method includes searching for a relevant peak within an FFT frequency window; and tuning the LO based on the frequency bin where the peak is found.

[0016] According to this aspect, in some embodiments, searching for a correlation peak includes: searching for a correlation peak within a first FFT frequency window of a first width; and when a correlation peak is found in the first window, searching for a correlation peak within a second FFT frequency window of a second width narrower than the first width. In some embodiments, searching for a correlation peak includes: searching for a correlation peak within a first FFT frequency window of a first width; and when no correlation peak is found in the first FFT frequency window, searching for a correlation peak within a second FFT frequency window of a second width wider than the first width. In some embodiments, tuning the LO includes, when no correlation peak is found in any FFT frequency window, tuning the LO with a step size wider than a portion of the maximum width of the FFT frequency window, said portion having a width of at least 20% of the maximum width. In some embodiments, tuning the LO includes tuning the LO to a local oscillation frequency that produces the strongest correlation peak within the correlation window. In some embodiments, searching for a correlation peak within the correlation window includes correlating a sequence detected in the envelope of the frequency components of the intermediate frequency (IF) signal with a reference sequence. In some embodiments, the method includes continuing to narrow the FFT frequency search window for each of a plurality of successive searches until a predetermined number of searches have been performed. In some embodiments, the method includes continuing to widen the FFT frequency search window for each of a plurality of successive searches until a predetermined number of searches have been performed. Attached Figure Description

[0017] A more complete understanding of this embodiment and its accompanying advantages and features will be more readily understood when considered in conjunction with the accompanying drawings, by referring to the following detailed description, wherein: Figure 1 This is a schematic diagram of a known low-power receiver; Figure 2 This is a more detailed schematic diagram of a known low-power receiver; Figure 3 This is a schematic diagram illustrating an example network architecture of a communication system based on the principles disclosed herein; Figure 4 This is a block diagram of a network node communicating with a wireless device via a wireless connection according to some embodiments of the present disclosure; Figure 5 This is a flowchart of an example process for tuning a self-excited LO in a wireless device according to some embodiments of the present disclosure; Figure 6 This is a block diagram of an example low-power receiver configured according to the principles disclosed herein; Figure 7 This is a block diagram of another example low-power receiver configured according to the principles disclosed herein; Figure 8 The peak search and related windows are displayed; Figure 9 A low-power receiver and a low-power transmitter are shown; Figure 10 This is a block diagram of yet another example of a low-power receiver configured according to the principles disclosed herein; Figure 11 This is a block diagram of another example low-power receiver configured according to the principles disclosed herein; Figure 12 This is a flowchart of an example process in a wireless device for adjusting the correlation window when searching for correlation peaks; and Figure 13 This is a block diagram of an example low-power receiver with a digital processor for tuning a self-excited local oscillator. Detailed Implementation

[0018] Before describing the exemplary embodiments in detail, it is noted that the embodiments primarily exist in a combination of device components and processing steps associated with a low-power receiver having intermediate frequency (IF) detection and local oscillator (LO) correction. Therefore, in the accompanying drawings, components are indicated by conventional symbols where appropriate, and only those specific details relevant to understanding the embodiments are shown so as not to obscure this disclosure with details that would be obvious to those of ordinary skill in the art who benefit from the description herein.

[0019] As used herein, relational terms such as “first” and “second,” “top” and “bottom” may be used only to distinguish one entity or element from another, and do not necessarily require or imply any physical or logical relationship or order between such entities or elements. The terminology used herein is merely for describing particular embodiments and is not intended to limit the concepts described herein. As used herein, the singular forms “a,” “an,” and “the” are intended to also include the plural forms unless the context clearly indicates otherwise. It will also be understood that the terms “comprises,” “comprising,” “includes,” and “including”, as used herein, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0020] In the embodiments described herein, the conjunction terms "communicating with" and the like can be used to refer to electrical or data communication, which can be achieved, for example, through physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling, or optical signaling. Those skilled in the art will appreciate that multiple components can interoperate, and modifications and variations are possible to achieve electrical and data communication.

[0021] In some embodiments described herein, the terms “coupled,” “connected,” etc., may be used herein to indicate a connection, although not necessarily a direct connection, and may include wired and / or wireless connections.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the concepts described herein. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the terms “comprises,” “comprising,” “includes,” and “including”, as used herein, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0023] As used herein, the term "network node" can refer to any type of network node included in a radio network, which may also include base stations (BS), radio base stations, base transceiver stations (BTS), base station controllers (BSC), radio network controllers (RNC), gNodeBs (gNBs), evolved Node Bs (eNBs or eNodeBs), Node Bs, multi-standard radio (MSR) radio nodes such as MSR BSs, multi-cell / multicast coordination entities (MCEs), relay nodes, donor nodes of control relays, radio access points (APs), transmission points, transmission nodes, remote radio units (RRUs), remote radio heads (RRHs), core network nodes (e.g., mobility management entities (MMEs), ad hoc network (SON) nodes, coordination nodes, location nodes, MDT nodes, etc.), external nodes (e.g., third-party nodes, nodes outside the current network), nodes in distributed antenna systems (DASs), spectrum access system (SAS) nodes, element management systems (EMSs), etc. Network nodes may also include test equipment. The term "radio node" as used herein may also refer to a radio device (WD), such as a radio device (WD) or a radio network node.

[0024] In some embodiments, the non-limiting terms wireless device (WD) and user equipment (UE) are used interchangeably. A WD as used herein can be any type of wireless device capable of communicating with a network node or another WD via radio signals, such as a wireless device (WD). A WD can also be a radio communication device, a target device, a device-to-device (D2D) WD, a machine-type WD or a WD capable of machine-to-machine communication (M2M), a low-cost and / or low-complexity WD, a sensor equipped with a WD, a tablet computer, a mobile terminal, a smartphone, a laptop computer (LEE) equipped with an embedded device, a laptop computer mount device (LME), a USB dongle, a client device (CPE), an Internet of Things (IoT) device, or a narrowband IoT (NB-IoT) device, etc.

[0025] Furthermore, in some embodiments, the generic term "radio network node" is used. It can be any kind of radio network node, which may include any of the following: base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, multi-cell / multicast coordination entity (MCE), relay node, access point, radio access point, remote radio unit (RRU), and remote radio headend (RRH).

[0026] Note that although terms from a particular wireless system, such as 3GPP LTE and / or New Radio (NR), may be used in this disclosure, this should not be construed as limiting the scope of this disclosure to the aforementioned systems. Other wireless systems (including, but not limited to, Wideband Code Division Multiple Access (WCDMA), Microwave Access Global Interoperability (WiMax), Ultra Mobile Broadband (UMB), and Global System for Mobile Communications (GSM)) may also benefit from utilizing the ideas covered in this disclosure.

[0027] It should also be noted that the functions described herein, such as those performed by wireless devices or network nodes, can be distributed across multiple wireless devices and / or network nodes. In other words, it is anticipated that the functions of the network nodes and wireless devices described herein are not limited to being performed by a single physical device, and in fact, can be distributed across several physical devices.

[0028] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will also be understood that the terms used herein should be interpreted as having the same meaning as they have in the context of this specification and the relevant field, and will not be interpreted in an idealized or overly formal sense unless so explicitly defined herein.

[0029] Some embodiments are designed for low-power receivers with intermediate frequency (IF) detection and local oscillator (LO) frequency correction.

[0030] Returning to the accompanying drawings, similar elements are indicated by similar reference numerals. Figure 3 The diagram illustrates a communication system 10 according to an embodiment, which may support 3GPP-type cellular networks such as LTE and / or NR (5G) standards. It includes an access network 12 (e.g., a radio access network) and a core network 14. The access network 12 includes multiple network nodes 16a, 16b, 16c (collectively referred to as network nodes 16), such as NBs, eNBs, gNBs, or other types of wireless access points. Each network node defines a corresponding coverage area 18a, 18b, 18c (collectively referred to as coverage area 18). Each network node 16a, 16b, 16c can be connected to the core network 14 via a wired or wireless connection 20. A first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to or be paged by the corresponding network node 16a. A second WD 22b in coverage area 18b can wirelessly connect to the corresponding network node 16b. Although multiple WDs 22a, 22b (collectively referred to as wireless devices 22) are shown in this example, the disclosed embodiments are equally applicable to situations where a single WD is in the coverage area or a single WD is connected to a corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include more WDs 22 and network nodes 16.

[0031] Furthermore, WD 22 is expected to be able to communicate simultaneously with more than one network node 16 and more than one type of network node 16, and / or be configured to communicate with more than one network node 16 and more than one type of network node 16, respectively. For example, WD 22 may have dual connectivity with LTE-enabled network nodes 16 and the same or different network nodes 16 that support NR. As an example, WD 22 may communicate with an eNB for LTE / E-UTRAN and a gNB for NR / NG-RAN.

[0032] Wireless device 22 is configured to include wireless receiver 24, which is configured to compensate for IF frequency drift. WD 22 may also include a low-power transmitter 26. Both wireless receiver 24 and low-power transmitter 26 are referred to as "low-power" because they are designed to consume less power than the main transceiver 25 used for primary communication with network nodes and / or another WD 22. Wireless receiver 24 is designed to consume less power than the main transceiver 25 by performing a reduced set of functions and using components that perform these reduced functions with minimal power consumption.

[0033] According to the embodiments, reference will now be made to Figure 4Describe the example implementation of WD 22 and network node 16 discussed in the preceding paragraphs.

[0034] The communication system 10 includes a network node 16, which includes hardware 28 enabling it to communicate with the WD 22. The hardware 28 may include a radio interface 30 for establishing and maintaining at least a wireless connection 32 with the WD 22 located within a coverage area 18 served by the network node 16. The radio interface 30 may be configured as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 30 includes an antenna array 34 for radiating and receiving signals(s) carrying electromagnetic waves.

[0035] In the illustrated embodiment, the hardware 28 of network node 16 further includes processing circuitry 36. Processing circuitry 36 may include processor 38 and memory 40. Specifically, in addition to or in lieu of a processor (e.g., a central processing unit) and memory, processing circuitry 36 may include integrated circuits for processing and / or control, such as one or more processors and / or processor cores and / or FPGAs (Field-Programmable Gate Arrays) and / or ASICs (Application-Specific Integrated Circuits), adapted to execute instructions. Processor 38 may be configured to access (e.g., write to and / or read from) memory 40, which may include any kind of volatile and / or non-volatile memory, such as cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0036] Therefore, network node 16 also has software 42 stored internally, such as in memory 40, or in external memory (e.g., a database, storage array, network storage device, etc.), which is accessible by network node 16 via an external connection. Software 42 can be executed by processing circuitry 36. Processing circuitry 36 can be configured to control any methods and / or processes described herein, and / or cause such methods and / or processes to be executed, for example, by network node 16. Processor 38 corresponds to one or more processors 38 for performing the functions of network node 16 described herein. Memory 40 is configured to store data, programming software code, and / or other information described herein. In some embodiments, software 42 may include instructions that, when executed by processor 38 and / or processing circuitry 36, cause processor 38 and / or processing circuitry 36 to perform the processes described herein for network node 16.

[0037] The communication system 10 also includes the previously mentioned WD 22. WD 22 may have hardware 44, which may include a radio interface 46 configured to establish and maintain a wireless connection 32 with a network node 16 serving the coverage area 18 currently in which WD 22 is located. The radio interface 46 may be configured as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 46 includes an antenna array 48 for radiating and receiving signals carrying electromagnetic waves. The radio interface of the wireless device 22 may include a wireless receiver 24 configured to compensate for unknown IF frequencies.

[0038] The hardware 44 of the WD 22 also includes processing circuitry 50. Processing circuitry 50 may include a processor 52 and memory 54. Specifically, in addition to or in lieu of a processor (e.g., a central processing unit) and memory, processing circuitry 50 may include integrated circuits for processing and / or control, such as one or more processors and / or processor cores and / or FPGAs (Field-Programmable Gate Arrays) and / or ASICs (Application-Specific Integrated Circuits), adapted to execute instructions. Processor 52 may be configured to access (e.g., write to and / or read from) memory 54, which may include any kind of volatile and / or non-volatile memory, such as cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0039] Therefore, WD 22 may further include software 56, which is stored, for example, in memory 54 at WD 22, or in external memory (e.g., a database, storage array, network storage device, etc.) accessible by WD 22. Software 56 may be executed by processing circuitry 50. Software 56 may include client application 58. Client application 58 may be used to provide services to human or non-human users via WD 22.

[0040] Processing circuitry 50 may be configured to control any of the methods and / or processes described herein, and / or cause such methods and / or processes to be performed, for example, by WD 22. Processor 52 corresponds to one or more processors 52 for performing the functions of WD 22 described herein. WD 22 includes memory 54 configured to store data, programming software code, and / or other information described herein. In some embodiments, software 56 and / or client application 58 may include instructions that, when executed by processor 52 and / or processing circuitry 50, cause processor 52 and / or processing circuitry 50 to perform the processes described herein with respect to WD 22. For example, the radio interface of wireless device 22 may include a wireless receiver 24 configured to compensate for IF frequency drift.

[0041] In some embodiments, the internal operation of network node 16 and WD22 can be as follows: Figure 4 As shown, and independently, the surrounding network topology can be Figure 3 The topology.

[0042] The wireless connection 32 between WD 22 and network node 16 conforms to the teachings of the embodiments described throughout this disclosure. More precisely, some of the teachings of these embodiments can improve data rates, latency, and / or power consumption, and thus provide benefits such as reduced user wait times, relaxed file size limits, better responsiveness, and extended battery life. In some embodiments, measurement procedures may be provided to monitor data rates, latency, and other factors that improve one or more of the embodiments.

[0043] Various units can be implemented to achieve the functionality of the low-power receiver disclosed herein, such that a portion of the unit is stored in memory within the processing circuitry. In other words, the unit can be implemented within the processing circuitry in hardware or a combination of hardware and software.

[0044] Figure 5 This is a flowchart of an example process in a wireless receiver 24 according to some embodiments of the present disclosure. One or more blocks described herein can be performed by one or more elements of the wireless receiver 24, such as one or more of LO 60, tuning circuitry 62, and mixer 64. The method includes searching for a relevant peak in an FFT frequency window (block S10); and tuning LO 60 based on the frequency bin of the found peak (block S12).

[0045] In some embodiments, searching for a correlation peak includes: searching for a correlation peak within a first FFT frequency window of a first width; and when a correlation peak is found in the first window, searching for a correlation peak within a second FFT frequency window of a second width narrower than the first width. In some embodiments, searching for a correlation peak includes: searching for a correlation peak within a first FFT frequency window of a first width; and when no correlation peak is found in the first FFT frequency window, searching for a correlation peak within a second FFT frequency window of a second width wider than the first width. In some embodiments, tuning LO 60 includes, when no correlation peak is found in any FFT frequency window, tuning LO 60 with a step size wider than a portion of the maximum width of the FFT frequency window, said portion having a width of at least 20% of the maximum width. In some embodiments, tuning LO 60 includes tuning LO 60 to a local oscillation frequency that produces the strongest correlation peak within the correlation window. In some embodiments, searching for a correlation peak within the correlation window includes correlating a sequence detected in the envelope of the frequency components of the intermediate frequency (IF) signal with a reference sequence. In some embodiments, the method includes continuing to narrow the FFT frequency search window for each of a plurality of successive searches until a predetermined number of searches have been performed. In some embodiments, the method includes continuing to widen the FFT frequency search window for each of a plurality of successive searches until a predetermined number of searches have been performed.

[0046] The general processing flow of the arrangements of this disclosure has been described, and examples of hardware and software arrangements for implementing the processes and functions of this disclosure have been provided. The following sections provide details and examples of the arrangement of a low-power receiver with intermediate frequency (IF) detection and local oscillator (LO) correction.

[0047] In some embodiments, an analog IF detection and LO correction block is implemented. Some embodiments are applicable to any kind of low-power receiver architecture using a self-excited oscillator (meaning an oscillator without phase-locked loop), but are not limited to this particular architecture.

[0048] Figure 6This is an example of a low-power receiver configured according to the principles disclosed herein, referred to herein as wireless receiver 24. Wireless receiver 24 includes an LO 60, tuning circuitry 62, mixer 64, IF filter 66, envelope detector 68, and baseband circuitry 70, which controls tuning circuitry 62 via control circuitry 72. Mixer 64 mixes the received signal with a local carrier signal from LO 60 to generate an IF signal. The IF signal is filtered by IF filter 66, and envelope detector 68 detects the envelope of the filtered IF signal. Baseband circuitry 70 can be configured to generate a control signal that is sent to control circuitry 72 to control the analog IF detection and LO correction functions of tuning circuitry 62. LO 60 can be a self-excited oscillator not controlled by frequency locking or phase-locked loop.

[0049] refer to Figure 7 Example wireless receiver 24: The receiver chain of wireless receiver 24 may include a baseband filter 74, a hard limiter 76, a correlator 78, and a sequence generator 80. The correlator 78 may output a control signal for controlling the crystal oscillator of the main receiver of WD 22.

[0050] The wireless receiver 24 includes a tuning circuit 62 that performs analog IF detection and LO correction functions to estimate the IF frequency and tune the LO frequency (i.e., detect the frequency and tune LO 60 in the correct direction to compensate for LO 60 drift). For example, LO 60 can be tuned by the tuning circuit 62 such that a correlation peak is observed in the correlation window, thereby enabling compensation for IF frequency drift. In some embodiments, the tuning circuit may include a low-power analog Fast Fourier Transform (FFT); the signal associated with each of the plurality of bins of the FFT output can be used to correlate with a predetermined sequence, such as a preamble sequence. The correlation is performed by at least one correlator. In some embodiments, only one correlator correlates all FFT bins sequentially. In some embodiments, the correlation is performed by separate correlators, one correlator per FFT bin. In some embodiments, the number of correlators can be optimized based on power, area, and performance. One or more bins corresponding to the highest correlation, or at least the correlation peak, or at least a peak above a threshold, are used to identify IF frequency drift and tune the local oscillator. One advantage of the analog FFT is its low power consumption. Another advantage is that all frequency bins of the FFT output are available simultaneously in parallel. By using parallel processing, it is possible to identify one or more most relevant bins by analyzing the correlation of these output signals, and thus identify the frequency drift to be compensated. If no peak is found, the IF signal is outside the FFT window, and therefore the LO can be calibrated. That is, the LO can be tuned with a larger step size, equal to a portion of the maximum FFT window width, for example, between 20% and 100% of this maximum width.

[0051] Figure 8 An example correlation process is shown. When the output of mixer 64 is outside the passband of IF filter 66, the output of the correlation process has no sharp peak. When the output of mixer 64 is within the passband of IF filter 66, the output of the correlation process has a detectable peak.

[0052] Figure 9 WD 22 is shown that shares the same LO 60 between wireless receiver 24 and low-power transmitter 26. Therefore, the tuned LO 60 can also be used for signals transmitted by low-power transmitter 26.

[0053] refer to Figure 10 The control circuit 72 can be used to control the analog FFT unit 84, so that the FFT unit 84 operates only when necessary (e.g., when in...). Figure 8 (When no peak is observed in the correlation window). Envelope detector 86 can be configured to detect the envelope of the signal in each frequency bin of the FFT output by FFT unit 84. Baseband filter 88 filters the output of envelope detector 86 and outputs a filtered signal that is correlated by correlator 90 with a locally generated sequence from sequence generator 92.

[0054] In typical low-power receiver topologies, some embodiments provide an IF signal within the bandwidth of the IF filter 66, making it possible to detect baseband clock drift. However, in cases where it is impossible to detect the IF frequency and tune LO 60 accordingly, the IF signal may drift outside the IF filter bandwidth window, making it impossible to detect and compensate for baseband clock drift. (See also...) Figure 8 ); refer to Figure 11 For low-power receivers that include a correlator 78 and a sequence generator 80 in the baseband, LO 60 can be tuned so that a sequence correlation peak can be observed within the correlation window. Without such a control loop, the received signal may be outside the IF filter bandwidth, and further compensation will be impossible. (See...) Figure 8 ); For low-power receivers including correlator 78, coarse frequency synchronization (i.e., a "quick find" frequency peak method) can be performed, followed by fine frequency synchronization using the correlator; and / or It is possible to use a narrower IF filter 66 in low-power receivers, which improves receiver sensitivity and interference immunity.

[0055] Some embodiments also achieve numerous network scalability advantages, such as one or more of the following: - like Figure 9As shown in the WD22, where the same LO 60 is shared between the wireless receiver 24 and the low-power transmitter 26, tuning the LO 60 can also be used to transmit signals. Low data rate communication can be established between low-power devices. Correcting the LO frequency drift makes it possible to transmit closer to the center frequency of other receivers, thereby achieving energy savings at the network scale. - When network-level interference and other sources of IF uncertainty are involved, additional information may be derived; and / or - Enables wireless receivers 24 in uncertain frequency environments, such as low-power device clusters.

[0056] Low-power simulated FFT implementation: An example implementation of FFT cell 84 is a 16-point analog domain FFT using a charge reuse analog Fourier transform (CRAFT) engine. For the definition of 5 GS / s (meaning a sampling rate of 5 GHz) and 16 cells, it demonstrates a power consumption of 3.8 mW.

[0057] With a projected maximum IF frequency of 250 MHz (consistent with target device-to-device applications), a sampling rate of only 500 MHz would suffice. Since the power consumption of analog FFTs scales linearly with respect to the sampling rate, the known FFT architecture implemented according to the principles disclosed herein can consume only approximately 0.38 mW, making it compatible with low-power receiver applications.

[0058] The dynamic range of the analog FFT unit 84 can be reduced to further reduce power consumption by at least 50%.

[0059] Furthermore, due to the introduction of the tuning circuit 62 and baseband feedback from the baseband circuit 70 or correlator 78, the FFT unit 84 can be turned off when not needed, which means reduced power consumption at the system level and even further.

[0060] Implementation of intermediate frequency detection and LO calibration: Implementation option: Use correlator.

[0061] In some embodiments, the tuning circuit 62 uses an envelope detector 86, a baseband filter 88, a comparator and correlator 90, and a frequency control unit 92 to process the output of the FFT unit 84. The correlator 90 uses a sequence generator 94 to search for the desired OOK modulated signal in different frequency bins provided by the FFT unit 84. The frequency control unit 92 controls the frequency of LO 60. Figure 10 The example of this topology is provided for wireless receiver 24, which uses a self-excited oscillator as LO 60 (without PLL). Figure 11 This is another example topology using the LO 60 wireless receiver 24 based on the principles disclosed herein.

[0062] By performing correlation on signals at different FFT frequency bins, it is possible to distinguish the desired IF signal from interference. In cases where multiple bins contain signal energy, the correlator 90 can then be used to determine which bin contains the desired signal. Another situation where correlation is useful is when the signal is very weak, at or below the noise floor, and therefore its presence cannot be determined solely by observing the signal power level.

[0063] When a correlator 90 is provided after the analog FFT 84, faster operation is possible than without such a correlator because several FFT cells can be studied in parallel for the modulated signal. Different numbers of correlators 90 and associated analog signal chains can be used, each chain including an envelope detector 86 and a baseband filter 88. To reduce chip area, the analog signal chain and correlator 90 may not be implemented for each FFT cell output signal. In this case, the signals can be studied sequentially, starting with the strongest signal and moving towards weaker signals, until the desired IF signal is found, based on the signal power level. Switches can be used to connect the FFT cell outputs to the envelope detector 86. With each envelope detector 86 connected to a separate subset of the FFT cell outputs using multiplexers, the search can begin with the strongest signal in each subset, moving to the second strongest, and so on, to reduce switching complexity compared to a full switch matrix.

[0064] Figure 12 The flowchart in is Figure 10 and 11 An example of the implementation process.

[0065] During the ON mode of the FFT unit 84 in the tuning circuit 62, the FFT unit 84 begins peak search with a default user-defined sequence code and window width (box S14). The correlator 90 correlates and integrates the signal received from the baseband filter 88 with the specified sequence code from the sequence generator 92 to obtain the frequency. f RF – f LO The expected peak (S20).

[0066] Once the desired peak is found (box S18), the frequency width of the FFT peak search window can be narrowed (box S20) to increase frequency resolution. The LO frequency can be tuned based on the FFT output of the found peak.

[0067] If no peak is found (box S18), the peak search frequency window can be widened by consuming more power (box S22). In the worst case, even with the maximum window width, no peak is found (box S24), requiring proper calibration of the self-excited oscillator to ensure... fLO >f RF – Maximum window width and f LO <f RF (Assuming low-end mixing) (Box S26).

[0068] Another possible implementation: using an ADC Other implementations of the IF detection and LO correction boxes are also possible. Some examples are described below. In some embodiments, the IF frequency can be searched by detecting the energy using FFT (detecting at which frequency the energy peak is observed). The oscillator frequency of LO60 can then be adjusted, and the peaks can be studied one by one along the main path. Furthermore, to detect the FFT energy peak, an envelope detector 86 and an ADC 96 can be implemented to quantize the signal from the envelope detector 86. Figure 13 An example embodiment is shown in which a digital processor 98 between ADC 96 and LO60 is configured to tune LO 60.

[0069] Some non-limiting embodiments may include one or more of the following.

[0070] An implementation of a low-power receiver for performing IF frequency detection and LO frequency correction without using a PLL, wherein: Example 1. A low-power receiver, comprising: a. A low-power self-excited oscillator generates a local carrier frequency (LO), which is fed into a down-conversion mixer; b. Baseband circuitry; and / or c. Controllable simulation of IF detection and LO correction frame.

[0071] Example 2. A controllable analog IF detection and LO correction frame from 1c, comprising: a. A simulated IF detection and LO correction box for estimating the IF frequency and tuning the LO accordingly, including a simulated FFT box; b. Control block, used to enable / disable analog IF frequency detection and LO correction box; Example 3. The low-power receiver in Example 1 further includes: a. Correlator, which correlates the received OOK sequence with the locally generated sequence; b. The baseband circuit from 1b also includes circuitry for generating and modulating clock signals with the same period time.

[0072] Example 4. IF frequency drift estimation is used to adjust LO.

[0073] Example 5. Between two measurements, the millimeter wave and analog components may be in idle mode.

[0074] Example 6. The WD includes a master transceiver and a low-power receiver. The master transceiver's reference clock is derived from the output of a crystal oscillator (XO), which also serves as the system clock for the low-power receiver's baseband. The low-power transmitter uses the same LO as the low-power receiver to transmit at a frequency close to that of other receivers in the network.

[0075] Example 7. The simulated IF detection and LO correction box of Example 2.a also includes (main implementation): a. Envelope detector; b. Baseband filter; c. Correlator; d. Sequence generator.

[0076] Example 8. The simulated IF detection and LO correction box of Example 2.a also includes (other implementations): a. Envelope detector; b. ADC.

[0077] As those skilled in the art will appreciate, the concepts described herein can be embodied as methods, data processing systems, computer program products, and / or computer storage media storing executable computer programs. Therefore, the concepts described herein can take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects, all collectively referred to herein as “circuit” or “module.” Any process, step, action, and / or function described herein can be performed by and / or associated with a corresponding module, which can be implemented using software and / or firmware and / or hardware. Furthermore, this disclosure can take the form of a computer program product on a tangible computer-readable storage medium having computer-executable computer program code contained within the medium. Any suitable tangible computer-readable medium can be utilized, including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

[0078] This document describes several embodiments with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer (thus creating a special-purpose computer), a special-purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create components for implementing the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams.

[0079] These computer program instructions may also be stored in a computer-readable storage medium or storage medium that can instruct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction components that implement the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0080] Computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus, thereby producing a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0081] It is important to understand that the functions / actions marked in the boxes may not occur in the order indicated in the operating instructions. For example, two boxes shown consecutively may actually be executed substantially simultaneously, or these boxes may sometimes be executed in reverse order, depending on the functions / actions involved. Although some diagrams include arrows on the communication path to indicate the main direction of communication, it should be understood that communication can occur in the opposite direction to the direction depicted by the arrows.

[0082] Computer program code used to perform the operations of the concepts described herein may be written in an object-oriented programming language, such as Python, Java®, or C++. However, computer program code used to perform the operations of this disclosure may also be written in a conventional procedural programming language, such as the "C" programming language. The program code may be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer, partially on a remote computer, or entirely on a remote computer. In the latter case, the remote computer may be connected to the user's computer via a local area network (LAN) or a wide area network (WAN), or it may be connected to an external computer (e.g., via the Internet through an Internet service provider).

[0083] In conjunction with the foregoing description and accompanying drawings, numerous different embodiments have been disclosed herein. It will be understood that it would be excessive and confusing to describe and illustrate each combination and sub-combination of these embodiments literally. Therefore, all embodiments can be combined in any manner and / or combination, and this specification (including the accompanying drawings) should be construed as constituting a complete written description of all combinations and sub-combinations of the embodiments described herein, as well as the ways and processes of making and using them, and should support the claims for any such combinations or sub-combinations.

[0084] The abbreviations that may be used in the preceding description include: Those skilled in the art will appreciate that the embodiments described herein are not limited to those specifically shown and described above. Furthermore, unless otherwise stated above, it should be noted that all figures are not drawn to scale. Based on the foregoing teachings, various modifications and variations are possible without departing from the scope of the appended claims.

Claims

1. A wireless receiver (24), comprising: A local oscillator LO (60) is configured to generate a local oscillator signal, wherein the LO (60) is not phase-locked; A mixer (64) is configured to mix the local oscillator signal with the received amplitude shift keying (ASK) modulated signal to generate an intermediate frequency (IF) signal. and A tuning circuit (62) is configured to estimate the frequency of the IF signal and tune the LO (60) to compensate for IF frequency drift. The tuning circuit (62) includes an analog fast Fourier transform circuit (84) configured to perform a fast Fourier transform (FFT) of the IF signal to obtain signals in a plurality of frequency bins. The IF frequency estimation is based on the correlation between the signals in the plurality of frequency bins and a reference sequence.

2. The wireless receiver (24) according to claim 1, wherein, The LO (60) is tuned according to a digital control signal of the FFT (84) based at least in part on the IF signal.

3. The wireless receiver (24) according to any one of claims 1 and 2 further includes an envelope detector for detecting the envelope of the FFT (84) of the IF signal and a baseband filter (88) for filtering the detected envelope.

4. The wireless receiver (24) according to claim 3 further includes at least one correlator (90) configured to correlate the sequence detected in the envelope of the detected FFT (84) of the IF signal with a reference sequence.

5. The wireless receiver (24) according to claim 4, wherein, The tuning circuit (62) is configured to tune the LO (60) such that a correlation peak appears in the frequency bin associated with at least one correlator (90).

6. The wireless receiver (24) according to claim 5, wherein, The FFT(84) is disabled when no peak is observed.

7. The wireless receiver (24) according to any one of claims 4-6, wherein, The at least one correlator (90) is configured to perform a coarse frequency estimation using a first-width FFT frequency window, and then perform a fine-width FFT frequency estimation using a second-width FFT frequency window that is narrower than the first width.

8. The wireless receiver (24) according to any one of claims 4-7, wherein, The ASK modulation signal is an on / off keyed OOK modulation signal, wherein each of the at least one correlator (90) is configured to search for the on / off keyed OOK modulation signal in different frequency bins of the FFT (84).

9. The wireless receiver (24) according to any one of claims 4-8, wherein, Each correlator (90) of the at least one correlator (90) performs a correlation between a reference sequence and a sequence associated with a different frequency bin of the FFT of the IF signal.

10. The wireless receiver (24) according to any one of claims 4-10, wherein, The tuning circuit (62) is configured to determine the frequency bin of the FFT associated with the strongest correlation peak.

11. The wireless receiver (24) according to any one of claims 4-9, wherein, The tuning circuit (62) is configured to tune the LO (60) to the frequency of the FFT frequency bin with the strongest correlation peak.

12. The wireless receiver (24) according to any one of claims 1-11, wherein, The tuning circuit (62) is configured to tune the LO (60) to a frequency that, when mixed with the received signal, provides an IF signal at a frequency within the operating bandwidth of the IF filter of the receiver chain of the wireless receiver (24).

13. The wireless receiver (24) according to any one of claims 1-12, further comprising, for each of the plurality of frequency compartments, an envelope detector and a baseband filter for detecting and filtering the envelope of the signal in the frequency compartment.

14. The wireless receiver (24) according to any one of claims 1-13, wherein, The wireless receiver (24) is included in the wireless device (22).

15. A method for compensating for frequency drift of a local oscillator LO (60) in a wireless receiver (24) according to any one of claims 1-14, the wireless receiver (24) being configured to provide a tuning control signal to the LO (60), the method comprising: Search for the (S10) correlation peak within the FFT frequency window; and The frequency binning (S12) of the LO (60) is tuned based on finding the peak frequency bin.

16. The method of claim 15, wherein, Search-related peaks include: Search for the relevant peak within a first FFT frequency window of the first width; and When the relevant peak is found in the first window, the relevant peak is searched in a second FFT frequency window with a width narrower than the first width.

17. The method according to any one of claims 15 and 16, wherein, The search for the relevant peaks includes: Search for relevant peaks within a first FFT frequency window of the first width; and If the correlation peak is not found in the first FFT frequency window, the correlation peak is searched in a second FFT frequency window with a width that is wider than the first width.

18. The method according to any one of claims 15-17, wherein, Tuning the LO (60) includes tuning the LO (60) with a step size wider than a portion of the maximum width of the FFT frequency window when no relevant peak is found in any FFT frequency window, the portion having a width of at least 20% of the maximum width.

19. The method according to any one of claims 1-15, wherein, Tuning the LO (60) includes tuning the LO (60) to the local oscillation frequency that produces the strongest correlation peak within the correlation window.

20. The method according to any one of claims 15-19, wherein, Searching for relevant peaks in the relevant window includes sequences detected in the envelope of the frequency components of the intermediate frequency (IF) signal that are correlated with the reference sequence.

21. The method according to any one of claims 15-20, further comprising continuing to narrow the FFT frequency search window for each of the plurality of successive searches until a predetermined number of searches have been performed.

22. The method according to any one of claims 15-20, further comprising continuing to widen the FFT frequency search window for each of the plurality of successive searches until a predetermined number of searches have been performed.

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