Apparatus, system, and method for improving frequency measurement in reverberation periods of an ultrasonic transducer

Abstract

The present disclosure relates to apparatuses, systems, and methods for improving frequency measurements during the reverberation period of an ultrasonic transducer. Embodiments of the invention include a primary short circuit (PSC) coupled to a primary side of a transformer and a damping element coupled to a transducer, the transducer being coupled to a secondary side of the transformer, the damping element being configured to damp a received signal during a portion of the reverberation period. The PSC and the damping element may be enabled substantially simultaneously. Enabling the PSC circuit alleviates a parallel resonance that would otherwise be partially generated in the transducer, but increases the received signal by a DC offset voltage. The damping element damps the DC offset voltage. The received signal may be damped before the received signal is amplified by an amplifier. The damping facilitates earlier and more accurate measurement of at least one operating characteristic of the PAS sensor during the reverberation. Another embodiment prevents the DC offset voltage by selectively enabling the PSC within a determined time of a zero crossing of a given signal.

Description

Technical Field

[0001] The present technology generally relates to devices, systems, and methods for detecting obstacles. More specifically, the present technology relates to parking assist sensors and other sensors for detecting obstacles. The present technology also relates to the use of ultrasonic sensors to detect obstacles. The present technology also relates to determining the operating frequency of a transducer. The transducer can be used in an ultrasonic sensor. The present technology also relates to determining the operating frequency of a transducer based on the measurement of one or more reverberations after a ranging signal is transmitted by the transducer. Background Art

[0002] Today, various sensor systems are used with motor vehicles and other systems. Examples of such sensor systems include parking assist sensors, rearview sensors, blind spot detection sensors, collision avoidance sensors, and others (collectively, each sensor herein is a "PAS" sensor and the collection of sensors forming a PAS system). PAS systems are typically used to assist a vehicle driver during parking (such as parallel parking), during lane changes, collision avoidance, etc. The vehicle driver can range from a human to a fully automated / self-driving vehicle system. PAS systems typically operate based on a sonar-type principle, whereby ultrasonic sound waves are transmitted and, based on the reception of an echo, an obstacle to be avoided (if any) is detected. Such obstacles can be of any form or type, including but not limited to other vehicles, pedestrians, animals, fixtures (such as light poles, building parts, etc.), etc. The obstacle can be stationary or moving.

[0003] PAS systems are typically configured to use the sonar principle and detect an obstacle within a varying distance from the sensor based on the time elapsed between the transmission of a ranging signal and the reception of an echo, where the transmission and reception are typically performed by the same transponder. As is well known, PAS sensors typically use a piezoelectric transducer (herein a "transducer") to transmit a ranging signal. The ranging signal can be transmitted as one or more pulses (or impulses of ultrasonic sound waves). After the reverberation period has elapsed, any resulting echo is also typically received by the transducer. During the reverberation period, the operating characteristics of the PAS sensor are typically measured.

[0004] However, a transducer typically used in combination with the secondary coil of a transformer coupled thereto typically produces series resonance and parallel resonance. System designers typically attempt to eliminate the parallel resonance to enable more precise determination of the PAS sensor operating characteristics.

[0005] There are various known methods for eliminating parallel resonance. However, when such parallel resonance is eliminated, a DC voltage offset (increase) typically occurs in the received signal provided by the transducer to the receiver component. Such DC offset delays and otherwise adversely affects the measurement of one or more PAS sensor characteristics detected by the receiver during the reverberation period.

[0006] Accordingly, devices, systems, and methods are needed for damping and / or eliminating DC offsets generated in received signals of a PAS sensor, where any parallel resonance effects of transducers and other external components (such as transformers) have been eliminated to facilitate more precise measurement of PAS sensor operating characteristics during the reverberation period of the PAS sensor. SUMMARY OF THE INVENTION

[0007] Various embodiments of the present disclosure describe devices, systems, and methods for improving frequency measurement during the reverberation period of a PAS sensor. For at least one embodiment, devices, systems, and methods are described for damping DC offsets present in received signals provided to a receiver of a PAS sensor. For at least one embodiment, devices, systems, and methods are described for preventing DC offsets from occurring in received signals provided to a receiver of a PAS sensor.

[0008] According to at least one embodiment of the present disclosure, a method may include enabling a primary short circuit coupled to a primary side of a transformer, and enabling a damping element coupled to a transducer coupled to a secondary side of the transformer. For at least one embodiment, the transducer may be configured to generate received signals during at least a transmit period and a reverberation period. The damping element may be coupled to the transducer and configured to damp the received signal during at least a portion of the reverberation period.

[0009] For at least one embodiment, the primary short circuit and the damping element may be enabled substantially simultaneously.

[0010] For at least one embodiment, the primary short circuit may be coupled to a first set of inductive coils of the transformer. The secondary side of the transformer includes a second inductive coil. Enabling the primary short circuit reduces parallel resonance generated by the combination of the second inductive coil, a transducer parallel capacitor, and an external capacitor. During enabling of the primary short circuit, the received signal increases in DC offset voltage.

[0011] For at least one embodiment, the damping element dampens the DC offset voltage when enabled. For at least one embodiment, the primary short circuit and the damping element may be enabled substantially simultaneously. For at least one embodiment, the received signal may be damped by the damping element before being amplified by an amplifier.

[0012] For at least one embodiment, enabling each of the primary short circuit and the damping element facilitates at least one operation, including mitigating parallel resonance and damping DC offset voltages present during reverberation period measurements. For at least one embodiment, the at least one operation may include accelerating an earlier measurement of at least one operating characteristic of the PAS sensor during the reverberation period. For at least one embodiment, the at least one operation may facilitate a more precise measurement of at least one operating characteristic of the PAS sensor during the reverberation period. For at least one embodiment, the at least one operating characteristic is the operating frequency of the transducer.

[0013] According to at least one embodiment of the present disclosure, a PAS sensor may include a transformer having a primary side and a secondary side. The sensor may further include a primary short circuit coupled to the primary side of the transformer and a transducer coupled to the secondary side of the transformer, the transducer being configured to generate a received signal. The received signal may be generated during at least the reverberation period and the echo period. The sensor may further include a damping element coupled to the transducer and configured to damp a DC offset voltage in the received signal during at least a portion of the reverberation period.

[0014] For at least one embodiment, the PAS sensor may include a controller configured to enable each of the primary short circuit and the damping element. When the primary short circuit is enabled and there is no damping of the DC offset voltage, the received signal amplitude may be increased above the receiver input limit by the DC offset voltage. For at least one embodiment, when the damping element is enabled, the DC offset voltage is damped. For at least one embodiment, damping of the DC offset voltage facilitates an earlier and more precise determination of at least one operating characteristic of the PAS sensor. For at least one embodiment, the at least one operating characteristic is the operating frequency of the transducer.

[0015] For at least one embodiment, the controller may further be configured to determine when the transducer has entered the reverberation period and, after a stabilization phase, enable each of the primary short circuit and the damping element.

[0016] For at least one embodiment, the damping element may include a first damping resistor and a first damping switch, the first damping resistor being coupled to each of the transducer and the high terminal of an amplifier (such as a low noise amplifier), the first damping switch switchably coupling the first damping resistor to a second electrical potential.

[0017] For at least one embodiment, the PAS sensor may include a second capacitor having a first end coupled to the transducer and a second end coupled to each of a first damping resistor and the high terminal of the amplifier. When the primary short is enabled and the damping element is not enabled, the second capacitor increases the received signal by a DC offset voltage. For at least one embodiment, when the received signal crosses an echo detection threshold, an echo period begins. The controller may be configured to deactivate each of the primary side short and damping before the echo period begins.

[0018] According to at least one embodiment of the present disclosure, a method may include detecting a zero crossing of a received signal generated by a transducer in a PAS sensor. The transducer generates the received signal during at least a reverberation period. The method may further include enabling a primary short coupled to a primary side of a transformer during a determined time of the zero crossing. A secondary side of the transformer is coupled to the transducer. When the primary short is enabled, a parallel resonance that would otherwise be generated during the reverberation period is alleviated.

[0019] For at least one embodiment, the method may include enabling a damping element. The damping element is coupled to the transducer and is configured to damp the received signal during at least a portion of the reverberation period. For at least one embodiment, the primary short and the damping element may be enabled substantially simultaneously. The damping element reduces the received signal when enabled while the primary side short is enabled. For at least one embodiment, the method may further include, during the reverberation period, measuring at least one operating characteristic of the PAS sensor at an earlier time and more precisely than in the case where at least the primary short is not enabled. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Features, aspects, advantages, functions, modules, and components of the devices, systems, and methods provided by various embodiments of the present disclosure are further disclosed herein with respect to at least one of the following description and drawings. In the drawings, like components or elements of the same type may have the same reference numerals and may include additional letter designators, such as 108a - 108n, etc., where the letter designator indicates that the components with the same reference numeral (e.g., 108) have common characteristics and / or features. Additionally, various views of a component may be distinguished by a first reference mark followed by a dash and a second reference mark, where, for the purposes of this description, the second reference mark is used to specify the view of the component. If only the first reference mark is used in this specification, the description applies to any similar component and / or view having the same first reference numeral, regardless of any additional letter designators or second reference marks (if any).

[0021] Figures 1A to 1C Schematic diagram of a prior art PAS sensor.

[0022] Figure 2shows a time-varying received signal received by a receiver of a prior art PAS sensor as by Figures 1A to 1C The received signal changes with time as received by the receiver of the prior art PAS sensor.

[0023] Figure 3 is a schematic diagram of a prior art PAS system that includes Figures 1A to 1C Two or more PAS sensors 100 of

[0024] Figure 4 shows a time-varying received signal received by a receiver of a damped PAS sensor configured according to at least one embodiment of the present disclosure.

[0025] Figure 5A shows a time-varying received signal received by a prior art PAS sensor, and wherein the DC offset is not damped, as opposed to a damped received signal that varies with time as received by a damped PAS sensor, and wherein the DC offset is damped.

[0026] Figure 5B shows a time-varying "amplified signal" (as described herein) provided by a prior art PAS sensor, and wherein the DC offset in the received signal is not damped, as opposed to a time-varying "damped amplified signal" (as described herein) provided by a damped PAS sensor, and wherein the DC offset in the received signal is damped.

[0027] Figure 6A is a schematic diagram of at least one embodiment of the present disclosure and a damped PAS sensor configured to damp the DC offset in the received signal.

[0028] Figure 6B is at least one embodiment of the present disclosure and is used in a Figure 6A Schematic diagram of the receiver in the damped PAS sensor configured to damp the DC offset in the received signal.

[0029] Figure 7A and Figure 7B is a schematic diagram of a phase detection PAS sensor configured according to at least one embodiment of the present disclosure.

[0030] Figure 8 shows a time-varying received signal received by a receiver of a phase detection PAS sensor according to at least one embodiment of the present disclosure.

[0031] Figure 9 is a flowchart showing at least one embodiment of the present disclosure and a method for using a damped PAS sensor to damp the DC offset originally present in the received signal.

[0032] Figure 10 is a flowchart showing at least one embodiment in accordance with the present disclosure and a process for using a phase detection PAS sensor to prevent DC offset that would otherwise occur in a received signal. DETAILED DESCRIPTION

[0033] The various embodiments described herein relate to devices, systems, and methods for damping DC offset in a received signal of a PAS sensor during a primary side short

[0034] period (PSSP) of a reverberation period (RP). As used herein, "damping" (and its conjugates) refers to damping, reducing, and / or eliminating DC offset from a received signal of a PAS sensor.

[0035] As Figures 1A to 1C shown, the PAS sensor 100 generally includes a transmitter 102 coupled to a first set of induction coils L1 located on the primary side of a transformer TR1. A second induction coil L2 located on the secondary side of the transformer TR1 is coupled to a transducer PZ1 that emits one or more ranging signals and receives one or more received signals. Such transmissions and receptions typically occur at ultrasonic frequencies, such as 50 kHz or other frequencies. One or more circuit elements are provided for controlling such transmissions, determining the frequency and other components of the transmitted ranging signals, and processing the received echo signals. A non-limiting example of such a PAS sensor 100 is described in more detail, for example, in Application 543.

[0036] As Figure 1A shown, the transducer PZ1 is generally coupled to a receiver 104 by a parallel circuit configuration including a first capacitor C1 and a first resistor R1. The first capacitor C1 generally matches the inductance and capacitance provided by the second induction coil L2. R1 is generally selected such that the reverberation signal is optimally damped. For at least one embodiment, R1 is 12 kΩ. Given that the peak-to-peak voltage generated by the transformer TR1 can include 200 volts or greater, overvoltage protection for the receiver 104 is typically provided by a second capacitor C2 and an optional third capacitor C3. It is generally understood that, for better EMC, C3 can be used to provide symmetry of the receiver input. For at least one embodiment, C2 and C3 (when used) can be coupling capacitors that can be used to isolate the received signal 114 between a high voltage domain (typically generated when the transducer PZ1 transmits) and a low voltage domain (typically generated when the transducer PZ1 receives an echo). Such voltage domains can vary by approximately 200 volts peak-to-peak. It is generally understood that the voltage generated by the transducer PZ1 (in this document, "ranging voltage") during the transmission of one or more ranging signals will also be received by the transducer PZ1. In the absence of overvoltage protection provided by the second capacitor C2, such a ranging voltage can overload the receiver 104.

[0037] AsFigure 1B As shown, the transducer PZ1 is typically a piezoelectric transducer, which can be electrically modeled as including a series resonance circuit (SRC) and a parallel resonance circuit (PRC). The series resonance circuit is formed by a third inductor L3 and a fourth capacitor C4 within the transducer PZ1, and the parallel resonance circuit is formed by a combination of a secondary induction coil L2, a fifth capacitor C5 generated from the electrical modeling of the transducer PZ1, and a first capacitor C1.

[0038] Several factors can affect the performance of the transducer PZ1, including but not limited to the manufacturing process used, the operating temperature, the age, and others. Given such variability, it should be understood that the SRC can be used to define the exact frequency at which the PAS sensor 100 can achieve the desired performance level. Therefore, to improve performance, by adjusting C1, the PRC can be tuned to be close enough to the SRC such that the desired quality factor (Q) of the transducer PZ1 can be achieved thereby. For some embodiments, tuning generally includes an appropriate match of the resistance provided by the first resistor R1 and the total capacitance provided by the first capacitor C1 ( Figure 1A as shown) and the fifth capacitor C5. Additionally, due to the direct correlation between the SRC and the transducer PZ1 frequency measured during the reverberation period, the PZ1 tuning generally occurs during the reverberation period (as described below). Additionally, it is generally understood that a substantially similar match of the SRC and the PRC and knowledge of the SRC frequency are generally required.

[0039] Furthermore, it should be understood that when the transmit frequency of the transducer PZ1 is tuned to be consistent with the SRC, changes in performance can be easily detected. Such changes in performance can be caused by various reasons, including but not limited to snow, ice, rain, or mud obscuring the sensor, age, temperature, or others. Additionally, in accordance with ISO26262, it is desirable to know the exact frequency of the transducer PZ1 in order to comply with various safety requirements and other regulatory requirements.

[0040] As shown in the figure, the transducer PZ1, the first capacitor C1, the first resistor R1, and the second capacitor C2 are commonly connected to a first node 110. The second capacitor C2 outputs a received signal 114 to the receiver 104. The received signal 114 can be referred to herein as having a high voltage potential. Each of the transducer PZ1, the first capacitor C1, and the first resistor R1 can be further coupled to a second node 112. The second node 112 can be grounded or otherwise provide a low impedance. A third capacitor C3 can be coupled to the second node 112 and can effectively output a low signal 116 to the receiver 104.

[0041] As is well known, the transducer PZ1 operates effectively within a given operating cycle including a transmission segment, during which a ranging signal is transmitted by the transducer PZ1. For at least one embodiment, the required operating frequency is 50 kHz. Such transmission of the ranging signal is detected by the receiving side of the transducer PZ1, and a received signal 114 is generated and provided to the receiver 104.

[0042] As Figure 1C shown, the transmitter 102 can generally be coupled to the power supply voltage Vsup by a third transmitter switch XS3 and a fourth transmitter switch XS4, respectively, which is selectively coupled to the center terminal XC of the first coil L1. The top terminal XT and the bottom terminal XB of the first coil L1 are coupled to a first current source I1 and a second current source I2, respectively. The transmitter 102 can include a primary short circuit 128, which is configured for the primary side short period (PSSP). The primary short circuit 128 can include a first transmitter resistor XR1 coupled to a third node 130 by a first transmitter switch XS1. The third node 103 can be grounded or otherwise provide a defined impedance. A second transmitter resistor XR2 is also coupled to the third node 130 by a second transmitter switch XS2.

[0043] Due to the coupling of the first coil L1 and the second coil L2, when the primary short circuit 128 is enabled, the short circuit thus provided is transmitted to the second coil L2, then to the transducer PZ1, and finally into the received signal 114. It should be understood that such transmission is based on the rated factor of the transformer TR1 and results in the received signal being offset (increased) by a DC component (herein, "DC offset"). Although there is a DC offset, frequency measurement may be impossible because the received signal 114 exceeds the "receiver input limit" 204 (as Figure 2 shown and further discussed below). As used herein, the "receiver input limit" refers to the known principle that the receiver clamps its output at a given level (such as level 204), rather than reducing its AC gain to zero as might occur when the received signal has a DC component exceeding a given limit.

[0044] As discussed in application 543 and otherwise known in the art, during the primary side short period PSSP, the PRC is removed so that the received signal 114 represents the performance of the transducer PZ1 based only on the SRC and not on both the SRC and the PRC.

[0045] Various embodiments of the present disclosure are conducive to damping the DC offset. Since the received voltage V(Rx) of the received signal earlier in the reverberation period is less than the receiver input limit 204, the embodiments of the present disclosure are conducive to more accurate and earlier performance measurement of the transducer PZ1. It should be understood that the longer measurement period provided by the embodiments of the present disclosure enables improvement in the accuracy of such performance measurement.

[0046] As Figure 2 shown, the received signal 114 can be defined as occurring within a received cycle (RC) having three components. First, a transmit period (TP) occurs from an initial / start time (t0(n)) to a first time (t1(n)), where "n" is an integer specifying the current operating cycle. The TP coincides with the transducer PZ1 transmitting a ranging signal. During the transmit period, the transmitted ranging signal is reflected into the receiving element of the transducer PZ1, and the ranging signal 114 is obtained during the TP. Such received signals exceed the voltage input limit of the receiver 104 (herein, such a limit is referred to as the receiver input limit 204).

[0047] Second, the receive cycle 202 includes a reverberation period (RP) that occurs from t1(n) to a sixth time (t6(n)). During the reverberation period RP, electrical signals are generated in the transducer PZ1 due to the continued reverberation of the mechanical elements of the transducer PZ1. During the "first / steady stage" of the reverberation period RP (shown as occurring from t1(n) to t2(n)), the received signal 114 behaves unstably. As Figure 2 shown for illustrative purposes only, such unstable behavior can include a decrease in amplitude that may be caused by, for example, a phase shift. Other undesirable behaviors may occur during the first / steady stage. For at least one embodiment of the present disclosure, the first stage occurs for fifty microseconds (50 μs), plus / minus ten percent (10%). For other embodiments, the first / steady stage can last for any given period of time, including zero microseconds (0 μs), twenty microseconds (20 μs), or other times. The primary side short period PSSP occurs after the first stage, and as shown, from t2(n) to t5(n). It should be understood that the PSSP can start at t1(n), but typically starts at t2(n). During the PSSP, a DC offset occurs for the known PAS sensor 100, but is damped by the embodiments of the present disclosure.

[0048] For known PAS sensors, the RP can be further divided into three additional stages, including a "second stage", a "third stage", and a "fourth stage". As Figure 2 shown, the second stage occurs from t2(n) to t4(n) (the time t3(n) is referenced Figure 6A shown and discussed below), the third stage occurs from t4(n) to t5(n), and the fourth stage occurs from t5(n) to t6(n).

[0049] Conversely, according to at least one embodiment of the present disclosure, as Figure 4As shown and due to the damping of the DC offset, a "second stage of damping" occurs from t2(n) to t3(n), and a "third stage of damping" occurs from t3(n) to t5(n). A fourth stage persists and occurs from t5(n) to t6(n). Thus, for at least one embodiment, the third stage of damping begins earlier at time t3(n) compared to the known undamped third stage that begins at time t4(n) (discussed in more detail below).

[0050] As Figure 2 shown, for the known PAS sensor 100 and during the second stage t2 - t4, due to the DC offset, the received signal 114 remains above the receiver input limit 204. At time t4, the received signal 114 drops below the receiver input limit 204, and the PAS sensor 100 system measurement can begin. As used herein, the third stage t4(n) to t5(n) may also be interchangeably referred to as the "reverberation measurement period" (RMP) of the known system. As Figure 4 shown and for at least one embodiment of the present disclosure, the third stage of damping t3(n) to t5(n) is also referred to as the "damped reverberation measurement period" (DRMP). Since the DC offset is not damped, for the known PAS sensor 100, the DC offset remains present during the RMP. Only after the received signal 114 has been sufficiently reduced by natural signal attenuation and / or the effect of the high resistance 132 at the input of the receiver 104, can the RMP begin for the known PAS sensor 100. Additionally, during the third stage t4(n) to t5(n), the voltage of the received signal 114 does not exceed the receiver input limit 204.

[0051] During the RMP and DRMP, the PAS sensor 100 is typically configured to perform various measurements based on the received signal 114. During the RMP and DRMP, the received signal 114 and the damped received signal 514 respectively at least partially represent one or more operating parameters of the PAS sensor 100.

[0052] Third, the Receive Cycle (RC) includes an Echo Detection Period (EDP) that occurs from t6(n) of the next operation cycle to the start time t0(n+1). Typically, the EDP begins when the received signal 114 drops below a given Echo Detection Threshold (EDT) 208. Prior to the EDP, the PAS sensor 100 can be saturated with noise, dominated by reverberation signals, and / or otherwise unable to perform obstacle detection. During the Echo Detection Period (EDP) from t6(n) to t0(n+1), the received signal 114 is generated in transducer PZ1, mainly due to the ranging signal reflecting from one or more obstacles and the transducer PZ1 receiving such reflections as one or more echo signals. During the EDP, obstacle detection and other uses of the PAS sensor typically occur. During the EDP, the received signal 114 is typically not damped, but can be damped for a given implementation.

[0053] As further shown and known, various circuit elements are also typically used in the PAS sensor 100 to convert, monitor, process, and otherwise manage the received signal 114 during each of the Transmit Period (TP), Reverberation Period (RP), and Echo Detection Period (EDP). Such components typically include an Analog-to-Digital Converter (ADC) 106 and a Digital Control Component 108. The functions and characteristics of the ADC 106 and the Digital Control Component 108 are well known in the art. The ADC receives the amplified signal 118 from the receiver 104 and outputs a digital signal 120. The Digital Control Component 108 is typically coupled to an Electronic Control Unit (ECU), and one or more data signals 122 are communicated via the ECU. The Digital Control Component 108 is typically configured to provide one or more first control signals 124 to the receiver 104 and one or more second control signals 126 to the transmitter 102.

[0054] As is well known and as Figure 3 shown, the ECU 300 can be coupled to one or more sensors 100-1 to 100-N, as well as other vehicle components 304, including but not limited to one or more signal actuators 304-1, steering actuators 304-2, brake actuators 304-3, throttle actuators 304-5, displays and user interfaces 304-6, etc. Such components are well known in the art and will not be further described herein.

[0055] As Figure 4 shown and according to at least one embodiment of the present disclosure, when the DC offset is damped from the received signal 114 and the damped received signal 514 can be provided to the damped receiver 605 (as Figure 6A shown).

[0056] More specifically, at least one embodiment of the present disclosure facilitates providing earlier generated cycles and / or more precise reverberation measurement cycles, such earlier generated cycles being referred to herein as DRMP. As shown and for at least one embodiment, the DRMP can start at t3(n), while the prior art RMP starts at t4(n). Damping of the DC offset causes the damped received signal 514 to fall below the receiver input limit 204 at an earlier time

[0057] earlier. It should be understood that for at least one embodiment, t2(n) and t3(n) can occur substantially simultaneously. For at least one embodiment, t3(n) occurs within 51.2 μs of t2(n). For at least one embodiment, t3(n) occurs approximately 350 μs earlier than t4(n) (the "earlier detection cycle" herein). It should be understood that the earlier detection cycle can be adjusted based on the ratio of the damping resistance provided by the first damping resistor DR1 (as described below with reference to Figure 6B stated) to the HR of a given receiver. For a non-limiting example, a damping resistance of 10 kOhms compared to an HR of 70 kOhms will result in t3(n) being increased by a factor of seven (7) relative to t4(n).

[0058] In Figure 5A is shown the effect of undamping the DC offset of the received signal 114 and damping the DC offset of the damped received signal 514.

[0059] In Figure 5B is shown the effect of undamping the DC offset of the amplified signal 118 and damping relative to the damped amplified signal 618. As discussed above, the presence of the DC offset generally prevents earlier determination of one or more operating characteristics of the PAS sensor 100.

[0060] As Figure 5A shown, when the DC offset is undamped, the voltage of the received signal 114 exceeds the receiver input limit 204. Such conditions delay the RMP until t4(n). In contrast, when damping the DC offset in an embodiment according to the present disclosure, the damped received signal 514 causes the DRMP to start at t3(n), where t3(n) occurs before t4(n). It should be understood that the actual DC voltage added to the received signal due to the DC offset and damped by an embodiment of the present disclosure depends on the circuit and the specific implementation. Using at least one embodiment of the present disclosure, such a DC offset voltage can be reduced by ninety percent (90%). Damping of such DC offsets facilitates earlier measurement of one or more operating characteristics of the PAS sensor. Similarly, in Figure 5BTherein, an amplified signal 118 generated by an undamped prior art PAS sensor 100 is shown and compared with a damped amplified signal 618 generated according to at least one embodiment of the present disclosure. Similarly, damping of the DC offset facilitates earlier occurrence of DRMP, which results in the damped digital signal 620 being available at t3(n), while for the prior art PAS sensor 100, the digital signal 120 is not available until t4(n). It should be understood that the amount of delay in the availability of the received signal avoided by damping the DC offset by using embodiments of the present disclosure depends on the circuit and the specific implementation. Further, it should be understood that for many known PAS sensors, the RMP may not have sufficient duration to complete the required frequency measurement because reverberation may complete earlier than provided by the RMP. Thus, as in embodiments of the present disclosure, by using DRMP, a longer period for frequency measurement can be provided.

[0061] Further, it should be understood that for at least one embodiment of the present disclosure, a ten percent (10%) reduction (pre-damping) in the voltage of the received signal 114 may occur by damping the DC offset.

[0062] As Figure 6A and Figure 6B shown, the damped PAS sensor 600 may include many circuit elements common to the Figure 1A PAS sensor 100, including those shown and described above. Herein, common components are generally identified. Further, for at least one embodiment, the damped PAS sensor 600 may include a damped receiver 605. The elements of the damped receiver 605 are shown in Figure 1C Figure 6B Therein.

[0063] More specifically, for at least one embodiment, the damped receiver 605 may include a damping element 602 configured to receive the received signal 114, damp the DC offset in such signals during a portion of the reverberation period (RP), and output a damped received signal 514. For at least one embodiment, damping of the DC offset occurs by using one or more voltage damping circuit elements. For at least one embodiment, damping of the DC offset occurs by selectively coupling one or more resistors to a ground node or a low impedance node.

[0064] More specifically, and as Figure 6B ​As shown, for at least one embodiment of the present disclosure, the damping element 602 may include a first damping resistor DR1 selectively coupled to a ground potential, a reference potential, or a low impedance potential through a first damping switch DS1. The first damping resistor DR1 may be configured to have a parallel circuit configuration with a low noise amplifier 628. The LNA 628 may be any suitable amplifier, such as those commonly known and used for PAS sensors. The LNA 628 receives the damped received signal 514 and outputs a damped amplified signal 618 after any additional amplifier stage 629.

[0065] For at least one embodiment, a second damping resistor DR2 may be selectively coupled to a ground potential through a second damping switch DS2. It should be understood that the purpose of each of the first damping resistor DR1, the first damping switch DS1, the second damping resistor DR2, and the second damping switch DS2 may be used to facilitate a fully differential receiver input configuration, where a high voltage (+) potential occurs at the high terminal 630 of the LNA 628 and a low voltage (-) potential occurs at the low terminal 632 of the LNA 628.

[0066] As further shown, the damping receiver 605 may also include a high resistor (HR) and a low resistor (LR). According to at least one embodiment, the HR and LR may also be coupled to a ground potential or other reference potential and are used to facilitate the damping of any DC voltage generated during the echo detection period (EDP).

[0067] For at least one embodiment, the damping element 602 damps the DC offset generated due to the respective enabling of the first transmit switch XS1 and the second transmit switch XS2, and at the same time the primary short circuit 128 is enabled. More specifically, and according to the subsequently generated phase of the fully differential receiver input configuration, the capacitor C2 or C3 is discharged by the first damping resistor DR1 or the second damping resistor DR2, respectively. For other configurations, only the second capacitor is discharged by the first damping resistor DR1 during DRMP.

[0068] For at least one embodiment, the first damping switch DS1 and the second damping switch DS2 may be operated in synchronization with the corresponding operation of the respective first transmit switch XS1 and the second transmit switch XS2. For at least one embodiment, the digital control 608 sends a first damping control signal 624 to the damping element 602, in synchronization with sending a second control signal 126 to the transmitter 102. The second control signal 126 includes the control signals provided by the primary short circuit 128 for the first transmit switch XS1 and the second transmit switch XS2. For at least one embodiment, the damping element 602 may be provided in combination with or separately from the damping receiver 605.

[0069] For at least one embodiment, at least DR1 and DR2 for the fully differential receiver can be resistive elements of 10 kOhm. For other embodiments, it should be understood that DR1 and / or DR2 can be selected based on the desired speed of the DC offset to be damped as provided by the second capacitor C2. For at least one embodiment, DR1 and / or DR2 can be selected such that the second capacitor C2 discharges in substantially twenty microseconds (20 μs). For at least one embodiment, the time period required to discharge the second capacitor C2 and damp any DC offset component can be determined based on the available reverberation time, where for a shorter reverberation time, tight damping of the received signal 114 is provided.

[0070] In addition, it should be understood that, given electromagnetic compatibility (EMC) considerations, a fully symmetric receiver input configuration may be required. When there are no EMC considerations, the second damping resistor DR2 and the second damping switch DS2 may not be utilized.

[0071] It should be understood that for Figure 6A and Figure 6B embodiments, the PAS sensor 600 does not need to be configured to determine when the zero-crossing of the received signal occurs because each of the primary short circuit 128 and the damping element 602 is operated substantially synchronously.

[0072] As Figure 7A and Figure 7B shown, and for at least one embodiment of the present disclosure, the "damping" of the DC offset can be achieved by preventing the generation of the DC offset. More specifically, the phase detection PAS sensor 700 can be configured to control the primary short circuit 128 such that its enabling occurs within a determined time of the zero-crossing or other change of one or more of the transmitted voltage signal, the transducer voltage signal, the received signal voltage V(Rx), or another detectable signal generated within the PAS sensor.

[0073] It should be understood that for an ideal circuit, the determined time can occur substantially simultaneously with such detected signal changes. However, for a non-ideal circuit, the determined time varies based on the characteristics of the circuit of a given PAS sensor and the actual components used therein, including but not limited to the characteristics of the second capacitor C2 and other circuit elements.

[0074] Thus, for at least one embodiment of the present disclosure, an iterative method can be used to determine the amount of adjustment required to determine the time. For one such iterative method embodiment, for a first operating cycle, the PSSP is enabled substantially simultaneously with the zero crossing of a detectable signal, such as a transmitted signal voltage, a transducer voltage signal, or other signal, and the resulting DC offset is measured. For a second operating cycle, an adjustment (positive or negative in time) is made to the determined time such that the corresponding adjustment of the enabling of the PSSP results in a reduction of the DC offset, as measured for the second operating cycle, relative to the zero crossing detected for the second operating cycle. Additional iterative adjustments can be made to the determined time until the desired reduction of the DC offset (if not completely eliminated) is achieved.

[0075] For another embodiment, the predetermined time can be determined during the manufacture of the PAS sensor, during the initialization phase of the PAS sensor, or otherwise. For at least one embodiment, the predetermined time can be algorithmically defined based on empirical analysis, simulation, or otherwise in view of the DC offset expected to be produced for a given set of PAS sensor circuit components. It should be understood that such algorithmic definition can be determined during initial testing of the PAS sensor in the factory, or during later testing of the PAS sensor in the field or other settings.

[0076] As shown, the phase detection PAS sensor 700 can include many circuit elements common to Figure 1A the PAS sensor 100, including Figure 1C those shown and described above and Figure 7B further modified therein. Herein, common components are generally identified. Additionally, for at least one embodiment, the phase detection PAS sensor 700 can include a phase detector 702 coupled to the transmitter 102. For at least one embodiment, the phase detector can be coupled to the digital control component 108 to receive a second control signal 126. The phase detector 702 operates the first transmit switch XS1 and the second transmit switch XS2 via a control signal 704. For at least one embodiment, these first and second transmit switches can be enabled within the determined time of a detectable change in the receiver signal 114. For at least one embodiment, such detectable change can be based on the time of the transmitter differential outputs TX1 and TX2 to derive a phase. For at least one embodiment, the determined time can be adjusted within one or more operating cycles. It should be understood that when the primary short 128 is enabled substantially precisely, substantially no DC offset is introduced onto the received signal 114.

[0077] For other embodiments, it should be understood that the phase detector 702 may be coupled to any circuit location that can detect a zero crossing. Such locations include, but are not limited to, locations on the secondary side of the transformer TR1, such as the first node 110 at the input of the receiver 104 and other locations.

[0078] For at least one embodiment, the detection of a zero crossing or other change in the received signal 114 may occur relative to the current induced in the first induction coil L1 or the second induction coil L2. However, it should be understood that due to the instability of the received signal 114 during the first / stable phase (t1(n)-t2(n)), the determination of the zero crossing is more difficult and less precise. Therefore, for at least one embodiment, the zero crossing detection occurs relative to the current induced by the first induction coil L1 on the primary side of the transformer TR1. For other embodiments, the zero crossing detection may occur based on the differential voltage across the top terminal XT and the bottom terminal XB.

[0079] It should be understood that the zero crossing received signal 714 of the phase detection PAS sensor 700 generally will not need to be reduced by using a damping element (such as the damping element 602).

[0080] As Figure 8 shown, the zero crossing reverberation measurement period (XRMP) may also substantially start at time t2(n). For at least one embodiment, t2(n) occurs within the determined time when the zero crossing received signal 714 crosses the receiver input limit 204. It should be understood that times t3(n) and t4(n) are not used. Instead, the XRMP may start when the zero crossing is detected by the phase detector 702, and the PSSP is enabled therewith, such as at time t2(n).

[0081] It should be understood that even when using the zero crossing embodiment, a DC offset component will still be generated due to imprecise timing, component delays, or other reasons. Therefore, for at least one embodiment of the present disclosure, the combined PAS sensor may include both the damping element 602 and the phase detector 702.

[0082] In addition, for at least one embodiment of the combined PAS sensor, the control signal 704 provided by the phase detector 702 to the first transmit switch XS1 and the second transmit switch XS2 may also be provided to the damping element 602, for example, via a direct connection, via the processing of the digital control component 108, or in other ways. Therefore, for at least one embodiment of the combined PAS sensor, time t3(n) may occur earlier during the PSSP by using zero crossing detection and damping of the received signal 114.

[0083] As Figure 9As shown, the method for damping DC offset according to an embodiment of the present disclosure starts at the beginning of the reverberation period (RP) (e.g., at time t1(n)), as in operation 900.

[0084] According to operation 902, the method may include waiting for a first / stable period, such as a stable period from t1(n) - t2(n). It should be understood that for at least one embodiment, the first / stable period may be a previously determined period. For another embodiment, the first / stable period may be based on a measurement of the received signal 114, where the end of the first / stable period is based on the received signal 114 presenting one or more predetermined signal characteristics. Examples of such predetermined signal characteristics may include, but are not limited to, frequency, phase, and amplitude. After the end of the first / stable period, the method continues.

[0085] According to operation 904A, the method may include enabling a primary short circuit. According to operation 904B, the method may include enabling a damping element. As described above and for at least one embodiment of the present disclosure, the enabling of the primary short circuit and the damping element occurs substantially simultaneously.

[0086] According to operation 906, the method may include waiting for the detection that the damped received signal is below the receiver input limit.

[0087] According to operation 908, the method may include analyzing the damped received signal to determine one or more operating characteristics of the PAS sensor.

[0088] According to operation 910, the method may include monitoring the damped received signal for crossing the echo detection threshold (EDT).

[0089] According to operation 912, the method may include an echo detection period (EDP). As described above, during the EDP, the received signal 114 is mainly affected by the received echo signal, where such echo signals can be used to detect obstacles.

[0090] According to operation 914, the method ends and a new operating cycle may begin, returning again to operation 900 for the next such operating cycle.

[0091] As Figure 10 shown, the method for eliminating DC offset in the received signal of a PAS sensor and according to an embodiment of the present disclosure starts at the beginning of the reverberation period (RP) (e.g., at time t1), as in operation 1000.

[0092] According to operation 1002, the method may include waiting for a first / stabilization period, such as a stabilization period from t1 to t2. It should be understood that for at least one embodiment, the first / stabilization period may be a previously determined period. For another embodiment, the first / stabilization period may be based on a measurement of the received signal 114, wherein the end of the first / stabilization period is based on the received signal 114 presenting one or more predetermined signal characteristics. Examples of such predetermined signal characteristics may include, but are not limited to, frequency, phase, and amplitude. After the end of the first / stabilization period, the method continues.

[0093] According to operation 1003, the method may include waiting for a detectable phase change in the received signal 114, the transmitter voltage, or the transducer voltage, a detectable change in the received voltage, or other changes.

[0094] According to operation 1004A, the method may include enabling a primary short circuit at a determined time after a detectable phase change in the received signal 114, the transmitter voltage, or the transducer voltage, a detectable change in the received voltage, or other changes is detected.

[0095] According to optional operation 1004B, the method may further include damping any remaining DC offset by enabling a damping element. As described above and for at least one embodiment of the present disclosure, the enabling of the primary short circuit and the damping element occurs substantially simultaneously.

[0096] According to operation 1006A / 1006B, the method may include waiting for the received signal or the damped received signal (when operation 1004B is performed) to fall below the receiver input limit.

[0097] According to operation 1008A / 1008B, the method may include analyzing the undamped or damped received signal, depending on the circumstances and based on whether operation 1004B is performed, to determine one or more operating characteristics of the PAS sensor.

[0098] According to operation 1010, the method may include monitoring the (un)damped received signal for crossing an echo detection threshold (EDT).

[0099] According to operation 1012, the method may include an echo detection period (EDP). As described above, during the EDP, the received signal 114 is mainly affected by the received echo signal, and such echo signals can be used to detect obstacles.

[0100] According to operation 1014, the method ends and a new operating cycle may begin, returning again to operation 100 for the next such operating cycle.

[0101] It should be understood that with reference to Figure 9 and Figure 10The above operations are merely illustrative and are not intended herein to occur in the order, sequence, or otherwise for all embodiments of the present disclosure. One or more operations may be performed in parallel and operations may not be performed, as provided for any given use of embodiments of the present disclosure.

[0102] Although the various embodiments of the invention claimed herein have been described above to a certain degree of particularity or with reference to one or more separate embodiments, many changes may be made to the disclosed embodiments without departing from the spirit or scope of the invention claimed herein. The use of the terms “about” or “substantially” means that a value of an element has a parameter that is expected to be close to the stated value or position. However, as is well known in the art, there may be minor variations that prevent the value from exactly equaling the stated value. Accordingly, differences such as a 10% difference are expected and known to be reasonable differences by one of ordinary skill in the art and are acceptable relative to the stated or ideal goal of one or more embodiments of the present disclosure. It should also be understood that the terms “top” and “bottom,” “left” and “right,” “upper” and “lower,” “first,” “second,” “next,” “last,” “before,” “after,” and other similar terms are used for descriptive and convenience purposes only and are not intended to limit any orientation or configuration of any element of the various embodiments of the present disclosure or any sequence of operations. Additionally, the terms “coupled,” “connected,” or otherwise are not intended to limit such interactions and signal communications between two or more devices, systems, components or otherwise to direct the interactions; indirect couplings and connections may also occur. Further, the terms “and” and “or” are not intended to be used in a limiting or expansive nature and cover any possible range of combinations of elements and operations of embodiments of the present disclosure. Accordingly, other embodiments are contemplated. It is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the basic elements of the invention as defined in the appended claims.

Claims

1. A method for a PAS sensor of a parking assistance system, the method comprises: enabling a primary short circuit, the primary short circuit being coupled to a primary side of a transformer; and enabling a damping element, the damping element being coupled to a transducer, the transducer being coupled to a secondary side of the transformer; wherein the transducer generates a received signal during at least a transmission period and a reverberation period; wherein the damping element is coupled to the transducer, and the damping element is operable to damp the received signal during at least a portion of the reverberation period; and wherein the damping element comprises: a damping resistor, the damping resistor being coupled to the transducer and a high terminal of an amplifier; and a damping switch, the damping switch being switchably coupled to a ground potential for the damping resistor.

2. The method according to claim 1, wherein the primary short circuit is coupled to a first set of inductive coils of the transformer; wherein the secondary side of the transformer comprises a second inductive coil; wherein enabling the primary short circuit alleviates a parallel resonance generated by a combination of the second inductive coil, a transducer parallel capacitor, and an external capacitor; wherein, when the primary short circuit is enabled, the received signal increases a DC offset voltage; and wherein the damping element, when enabled, damps the DC offset voltage.

3. The method according to claim 2, wherein the primary short circuit and the damping element are enabled substantially simultaneously; and wherein the received signal is damped by the damping element before being amplified by an amplifier.

4. The method according to claim 2, wherein enabling the primary short circuit and the damping element facilitates at least one operation, the at least one operation comprises: alleviating the parallel resonance during reverberation period measurement; damping the DC offset voltage; and accelerating an earlier and more accurate measurement of at least one operating characteristic of the parking assistance system PAS sensor during the reverberation period.

5. A parking assistance system PAS sensor, the PAS sensor comprises: a transformer having a primary side and a secondary side; a primary short circuit, the primary short circuit being coupled to the primary side of the transformer; a transducer, the transducer being coupled to the secondary side of the transformer, the transducer being operable to generate a received signal; wherein the received signal is generated during at least a reverberation period and an echo period; a damping element, the damping element being coupled to the transducer, the damping element being operable to damp a DC offset voltage in the received signal during at least a portion of the reverberation period; a controller, the controller being operable to enable the primary short circuit and the damping element; wherein when the primary short circuit is enabled and there is no damping of the DC offset voltage, the received signal amplitude is increased by the DC offset voltage above a receiver input limit; wherein when the damping element is enabled, the DC offset voltage is damped; and wherein the damping element comprises: a damping resistor, the damping resistor being coupled to the transducer and a high terminal of an amplifier; and A damping switch that can switchably couple the damping resistor to a potential different from the potential of the high terminal.

6. The PAS sensor according to claim 5, wherein damping of the DC offset voltage facilitates earlier and more precise determination of at least one operating characteristic of the PAS sensor.

7. The PAS sensor according to claim 6, wherein the controller is further operable to: determine when the transducer has entered the reverberation period; and after the stabilization phase, enable the primary short circuit and the damping element.

8. The PAS sensor according to claim 5, wherein the damping element further comprises: a first damping resistor coupled to the high terminal of the transducer and the low noise amplifier; a first damping switch that can switchably couple the first damping resistor to a second potential; a second capacitor having a first end coupled to the transducer and a second end coupled to the high terminal of the first damping resistor and the low noise amplifier; wherein when the primary short circuit is enabled and the damping element is not enabled, the second capacitor increases the received signal by the DC offset voltage; wherein when the received signal crosses the echo detection threshold, the echo period begins; and wherein the controller deactivates the primary side short circuit and the first damping resistor before the start of the echo period.

9. A method for a parking assist system PAS sensor, the method comprises: detecting a change in a first signal generated by a parking assist system PAS sensor; wherein the first signal is generated during at least a reverberation period; and at a determined time after detecting the change in the first signal, enabling a primary short circuit coupled to the primary side of a transformer, wherein the secondary side of the transformer is coupled to a transducer, and in response to enabling the primary short circuit, reducing the parallel resonance that would otherwise occur during the reverberation period; and enabling a damping element coupled to the transducer, the damping element being configured to damp the received signal via a first damping resistor and a first damping switch during at least a portion of the reverberation period, the first damping resistor and the first damping switch both being switchably coupled to a potential.

10. The method according to claim 9, wherein when the primary side short circuit is enabled, the damping element reduces the received signal when enabled; and the method further comprises: measuring at least one operating characteristic of the PAS sensor at an earlier time during the reverberation period and more precisely than would be the case without enabling at least the primary short circuit.

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