MONITORING A HIGH-FREQUENCY TRANSMITTER

Abstract

Proposed embodiments provide a radio frequency (RF) transmitter assembly and a method for monitoring the RF transmitter. The RF transmitter assembly includes a phase shifter configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to an RF reference signal. The RF transmit signal is coupled to a transmit antenna, while a portion of the RF transmit signal is coupled out to generate an RF feedback signal. A binary phase stepper is provided to generate an RF test signal by applying only either a first phase offset or a second phase to the RF reference signal. A mixer is also provided to mix the RF test signal and the RF feedback signal to generate a mixer output signal.As a result of the simplified hardware of the binary phase stepper (operable in only two modes), space can be saved. At the same time, an efficient means for monitoring the phase shifter is disclosed, requiring only two adjustments of the phase stepper.

Description

TECHNICAL FIELD

[0001] This invention generally relates to radio frequency (RF) transmitters. More particularly, it relates to RF transmitter arrays and methods for evaluating the performance of an RF transmitter array. BACKGROUND

[0002] Modern radar devices such as radar range and speed sensors can be integrated into so-called monolithic microwave integrated circuits (MMIC). Radar sensors can be used, for example, in the automotive sector, where they are used in advanced driver assistance systems (ADAS) such as adaptive cruise control (ACC). Such systems can be used to automatically adjust a car's speed to maintain a safe distance from other vehicles ahead. However, RF circuits are also used in many other areas, such as RF communication systems.

[0003] A radar MMIC typically contains elements of the RF front-end of a radar transceiver (e.g., local oscillators, power amplifiers, low-noise amplifiers, mixers, etc.), analog preprocessing of the intermediate frequency (IF) or baseband signals (e.g., filters, amplifiers, etc.), and analog-to-digital conversion (ADC). The RF front-end typically includes multiple receive and transmit channels in applications that employ beamsteering techniques and phased array antennas (to detect the angle of arrival of incoming RF radar signals).

[0004] The phase of the transmit signal must be controlled very precisely. Accordingly, the phase shift and / or amplitude gain caused by each output channel must be known. Therefore, feedback hardware for measuring the transmit phase is implemented in many state-of-the-art radar MMIC transceivers. This hardware facilitates the phase calibration of each transmit channel. However, this hardware requires additional space and consumes additional power.

[0005] DE 10 2018 112 092 A1 describes a circuit including a radio frequency (RF) channel having an input node and an output node configured to receive an RF oscillator signal at the input node and provide an RF output signal at the output node; a mixer configured to mix an RF reference signal and an RF test signal representative of the RF output signal to generate a mixer output signal; an analog-to-digital converter configured to sample the mixer output signal to generate a sequence of sample values;and a control circuit configured to generate a sequence of phase shifts by phase-shifting the RF test signal and / or the RF reference signal using one or more phase shifters, calculate a spectral value from the sequence of samples, and calculate estimated phase information indicative of a phase of the RF output signal based on the spectral value.;

[0006] DE 10 2018 114 471 A1 describes a radar system comprising a first radar chip with a first RF contact, a second radar chip with a second RF contact, an RF signal path connecting the first RF contact to the second RF contact, and a local oscillator arranged in the first radar chip and configured to generate an RF oscillator signal and coupled to the first RF contact to transmit the RF oscillator signal to the second radar chip. A feedback circuit in the second radar chip is switchably connected to the second RF contact and configured to reflect at least a portion of the RF oscillator signal arriving via the RF-RF signal path as an RF feedback signal.A measuring circuit arranged in the first radar chip, which is connected to the first RF contact via a coupler, receives the RF feedback signal and is configured to determine a signal representing a phase shift.

[0007] There is therefore a need for a compact and energy-efficient means of monitoring the operation of an RF transmitter. SUMMARY

[0008] Examples disclosed herein propose a radio frequency (RF) transmitter arrangement comprising a phase shifter, a coupler, a binary phase stepper, and a mixer. The phase shifter is configured to receive an RF reference signal and to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal. The coupler is configured to couple the RF transmit signal to a transmit antenna and to extract a portion of the RF transmit signal to generate an RF feedback signal. The binary phase stepper is configured to receive the RF reference signal and to generate an RF test signal.The phase stepper is configured to be operable in a first mode in which the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal, and in a second mode in which the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal, wherein the first phase offset differs from the second phase offset. The mixer is configured to receive the RF test signal and the RF feedback signal, and to mix the RF test signal and the RF feedback signal to generate a mixer output signal.

[0009] Proposed approaches use a binary phase-stepping device capable of applying only two distinct phase offsets to the RF reference signal to generate RF test signals for comparison with the RF feedback signal to evaluate the transmit path of the RF transmitter array (i.e., to monitor the phase shifter). This allows the phase shifter's operation to be evaluated while minimizing the space required by the monitoring hardware, while facilitating rapid monitoring. Thus, the proposed RF transmitter array finds particular use when deployed within a radar MMIC.

[0010] Other examples disclosed herein provide a method for evaluating the performance of an RF transmitter assembly.The RF transmitter assembly includes: a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal; a coupler configured to couple the RF transmit signal to a transmit antenna and to extract a portion of the RF transmit signal to generate an RF feedback signal; a phase stepper configured to receive the RF reference signal and to generate an RF test signal based on applying one or a plurality of test phase offsets to the RF reference signal; and a mixer configured to receive the RF test signal and the RF feedback signal and to mix the RF test signal and the RF feedback signal to generate a mixer output signal. The procedure has:. while the phase stepper applies a first phase offset to the RF reference signal, controlling the phase shifter to generate a first sequence of RF transmit signals, each of the RF transmit signals being based on applying each of a test set of phase offsets to the RF reference signal; while the phase stepper applies a second phase offset to the RF reference signal, controlling the phase shifter to generate a second sequence of RF transmit signals, each of the RF transmit signals being based on applying each of a test set of phase offsets to the RF reference signal; sampling the mixer output at a plurality of sampling times to provide a sequence of digital samples, each of the sequence of digital samples corresponding to a respective one of the first sequence of RF transmit signals or one of the second sequence of RF transmit signals; Applying a discrete Fourier transform (DFT) to the sequence of digital samples to generate a plurality of DFT bin values, each DFT bin value corresponding to different harmonics present in the sequence of digital samples, the DFT bin values ​​comprising a DC amplitude value of the sequence of samples, a first harmonic amplitude value of the sequence of samples, and a third harmonic amplitude value of the sequence of samples; and Identifying a defect of the phase shifter based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value.

[0011] The proposed method thus facilitates the detection of a phase shifter defect by operating a phase stepping device to apply only two different phase offsets. This is achieved by operating the phase shifter to generate a sequence of RF transmit signals (by applying a test set of phase offsets to the RF reference signal) while the phase shifter applies a first phase offset, and while the phase shifter applies a second phase offset to generate a sequence of digital samples. Processing these digital samples can thus provide information for detecting / identifying a phase shifter defect while minimizing the power consumption and time required to complete the process.

[0012] Those skilled in the art will recognize additional features and advantages upon reading the following detailed description and upon viewing the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present disclosure is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like reference numerals refer to similar or identical elements. The elements of the drawings are not necessarily to scale relative to one another. The features of the various illustrated examples may be combined, provided they are not mutually exclusive. Fig. Figure 1 illustrates an RF transmitter arrangement. Fig. Figure 2 illustrates a binary phase stepper device according to one aspect of the invention. Fig. 3 is a flowchart of a method for evaluating the performance of an RF transmitter array. DETAILED DESCRIPTION

[0014] Some examples described herein provide an RF transmitter arrangement. The RF transmitter arrangement includes a binary phase stepper capable of operating in only two modes, each mode applying a different phase offset to an RF reference signal to generate RF test signals, while a phase shifter generates an RF transmit signal by applying a phase offset to the RF reference signal. An RF feedback signal is extracted from the RF transmit signal and compared to the RF test signals, from which the operation of the phase shifter can be evaluated.

[0015] Further examples described herein provide a method for evaluating the performance of an RF transmitter array. The method generates a sequence of digital samples by mixing a plurality of RF transmit signals generated by the phase shifter with RF test signals generated by the phase stepper operating in two different modes.

[0016] Proposed embodiments provide a radio frequency (RF) transmitter assembly and a method for monitoring the RF transmitter. The RF transmitter assembly includes a phase shifter configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to an RF reference signal. The RF transmit signal is coupled to a transmit antenna, while a portion of the RF transmit signal is coupled out to generate an RF feedback signal. A binary phase stepper is provided to generate an RF test signal by applying only either a first phase offset or a second phase to the RF reference signal. A mixer is also provided to mix the RF test signal and the RF feedback signal to generate a mixer output signal.As a result of the simplified hardware of the binary phase stepper (operable in only two modes), space can be saved. At the same time, an efficient means for monitoring the phase shifter is disclosed, requiring only two adjustments of the phase stepper.

[0017] To best understand the present disclosure, it is important to understand the functional operation of existing RF transmitter assemblies with a means for evaluating phase shifter behavior.

[0018] Fig. 1 illustrates an example of an RF transmitter assembly 100. It is noted that the RF transmitter assembly 100 of Fig. Figure 1 is a simplified block diagram illustrating the basic structure of the RF transmitter transmit path (i.e., RF front-end) and the measurement path and may therefore include additional components depending on the application, for example, multiple transmit paths, each applying a different phase offset to generate different RF transmit signals.

[0019] The transmit path of the RF transmitter assembly 100 includes a phase shifter 110, an output amplifier 120, a coupler 130, and a transmit antenna 140. The measurement path includes a phase stepper 150, a mixer 160, an ADC converter 170, and a processor / controller 180.

[0020] An RF reference signal is generated, for example, by a local oscillator (LO). The RF reference signal can therefore also be referred to as an LO signal. The RF reference signal can be frequency-modulated. In radar applications, such as automation applications, the LO / RF reference signal is typically located in the super-high frequency (SHF) or extremely high frequency (EHF) band (e.g., between 76 GHz and 81 GHz).

[0021] The RF reference signal is fed through a splitter 105 into both the transmission path and the measurement path of the RF transmitter arrangement 100.

[0022] In the transmit path, phase shifter 110 receives the RF reference signal and generates an RF transmit signal. The RF transmit signal is generated by applying one of a plurality of phase offsets to the RF reference signal. Accordingly, phase shifter 110 controls the phase of the RF transmit signal. This means that phase shifter 110 is required for precise control of the phase of the RF transmit signal—either to program a different starting phase of the RF transmit signal or to continuously modulate the phase of the RF transmit signal. Thus, phase shifter 110 controls an overall phase offset / delay of the transmit path.

[0023] In some cases, phase shifter 110 may apply any phase offset between 0 and 360 degrees. Typically, phase shifter 110 may adjust the phase of the RF reference signal to one of 64 or more different (equidistant) phases. Phase shifter 110 may be implemented using IQ (in-phase / quadrature) modulators. Nevertheless, phase shifter 110 may be any component capable of applying any of a plurality of phase offsets, as would be appreciated by one skilled in the art.

[0024] The transmit path may additionally include an output amplifier 120 for amplifying the RF transmit signal. The transmit path further includes a coupler 130 configured to couple the RF transmit signal to a transmit antenna 140 for radiating the signal into the environment.

[0025] In particular, coupler 130 is configured to provide power of the RF transmit signal to transmit antenna 140 with minimal power loss. Coupler 130 also extracts a fraction of the power of the RF transmit signal and provides it to the measurement path, and in particular, to mixer 160. This fraction is typically in the range of 20 dB to prevent the RF signal transmitted to the antenna from suffering excessive power reduction due to this power split.

[0026] It is desirable to know the precise phase shift of the RF transmit signal relative to the RF reference signal applied through the RF transmit path (i.e., actively applied by phase shifter 110 and passively applied by other components such as amplifier 120). If the RF transmitter is part of a radar sensor device, the phase of the RF transmit signal must be known to derive the beam angle. In other words, the phase shift of the RF transmit signal must be tuned to specific values ​​to achieve a desired beam angle.

[0027] However, various factors can affect the phase offset of the transmit path. For example, the temperature of the components in the transmit path can change the phase offset applied by these components. Furthermore, manufacturing tolerances and aging can affect the phase offset applied by the components, in particular the phase shifter 110. Accordingly, any imperfections in the phase offset must be detected and compensated (e.g., by calibrating the phase shifter 110) to ensure correct operation of the RF transmitter. This is relevant for radar applications, and particularly in radar used for automotive applications, since any errors can make the radar unsafe for use. Nevertheless, phase offset compensation may also be required for other applications, such as wireless communication systems.

[0028] Accordingly, it is typical for state-of-the-art RF transceivers to have a measurement path as shown.

[0029] The measurement path includes a phase stepper 150 configured to receive the RF reference signal and apply one of a plurality of phase offsets to the RF reference signal to generate an RF test signal. Similar to the phase shifter 110 of the transmit path, the phase stepper 150 applies one of a plurality of (typically equidistant) phase offsets between 0 and 360 degrees.

[0030] In contrast to the phase shifter 110, the phase stepper 150 typically has fewer settings (i.e., can be controlled to apply a smaller number of different phase offsets). However, the more settings the phase stepper 150 has, the more accurate the measurement result of the phase offset applied by the phase shifter 110 (due to a noise averaging effect). Therefore, it is generally desirable to provide a phase stepper 150 with a high number of settings. The trade-off for this is that it may take longer to perform the measurement because more measurements must be taken and more processing is required.

[0031] Furthermore, the measurement path includes a mixer 160 that receives the RF test signal from the phase stepper 150, and an RF feedback signal that is extracted from the RF transmit signal by the coupler 130. The RF feedback signal is thus essentially the same (ie, has the same phase offset) as the RF transmit signal.

[0032] Mixer 160 combines the RF test signal and the RF feedback signal to generate a mixer output signal. Specifically, the RF test signal is downconverted by mixer 160 with the RF feedback signal, resulting in a mixer output signal.

[0033] Finally, the mixer output signal is digitized by an analog-to-digital converter (ADC). That is, the mixer output signal is sampled by the ADC 170 to generate digital samples. The digital samples can then be processed by a processor 180 to extract the amplitude and phase information.

[0034] In particular, to extract a phase measurement of the phase shifter 110 for a setting of the phase shifter 110 (i.e., for a phase offset applied by the phase shifter 110), the following procedure is performed: (i) the phase shifter 110 is controlled to apply the phase offset to the RF reference signal to generate an RF transmit signal (and thus a particular RF feedback signal); (ii) the phase stepper 150 is controlled to apply each of the plurality of phase offsets available from the phase stepper 150 (e.g., cycles through each setting of the phase stepper 150); (iii) for each offset applied by the phase stepper 150 (and after the signals have settled), the ADC is controlled to generate a digital sample by sampling the mixer output signal; (iv) once all digital samples are generated, an FFT is applied to the digital samples; (v) Phase and amplitude information extracted from the first harmonic of the FFT.

[0035] Accordingly, to extract phase and amplitude information of the transmit path for phase adjustment of phase shifter 110, phase stepper 150 must be cycled through various settings and measurements taken during each adjustment. Note that the amplitude of the transmit path includes the amplitude of the output amplifier 120, and the phase of the transmit path includes the controllable phase of phase shifter 110 and the phase of the output amplifier 120. There is also another phase shift applied in the measurement path from the output of coupler 130 to the input of mixer 160 (which is essentially constant because it includes passive elements).

[0036] It should be noted that during this measurement procedure, the transmitter must be active and therefore consumes power. It should also be noted that, since the phase stepper 150 must have a large number of settings, the phase stepper 150 consumes a large amount of space, which is particularly disadvantageous when the RF transmitter assembly 100 is implemented in a radar MMIC. Furthermore, the measurement procedure consumes power and can therefore heat the RF transmitter assembly 100, resulting in further deviation of the phase offset. It was therefore recognized that there is a need for an improved means of monitoring the phase offset applied by the transmit path.

[0037] Fig. Figure 2 illustrates a binary phase stepper 151 according to this aspect of the invention. The illustrated binary phase stepper 151 replaces the phase stepper 150 described above.

[0038] It is proposed to replace the phase stepper 150, which is typically used to monitor the phase offset applied by the transmit path, with a binary phase stepper 151. That is, known phase steppers are operable in a large number of different modes / settings to provide a high number of different phase offsets. In fact, this is often desirable to improve the accuracy of the measurement using the known measurement technique described above (in which a sample of the mixer output signal is taken for each RF test signal while the phase stepper cycles through each of a plurality of phase offsets). In contrast, the proposed solution provides a binary phase stepper 151 operable exclusively in only two modes.

[0039] As can be seen, the binary phase stepper 151 is operable only in a first mode, in which the phase stepper 151 generates the RF test signal based on applying a first phase offset (e.g., 0 degrees) to the RF reference signal, and in a second mode, in which the phase stepper 151 generates the RF test signal based on applying a second phase offset (e.g., 90 degrees) to the RF reference signal. To be clear, the first phase offset is different from the second phase offset.

[0040] This significantly reduces the area and complexity of the phase stepper 150 since only two different offsets need to be applied by the binary phase stepper 151.

[0041] In one embodiment, a difference between the first phase offset and the second phase offset of the binary phase stepper 151 is 90 degrees. For example, the first phase offset may be 0 degrees, and the second phase offset may be 90 degrees. As will become clear from the following, this selection of phase offsets may simplify the processing / calculations for determining phase and amplitude information of the RF transmit signal. However, alternative phase offsets may still allow for the derivation of phase and amplitude information.

[0042] Accordingly, to determine phase information of the RF transmit signal, the controller 180 of the RF transmitter assembly 100 may be configured to first, while the binary phase stepper 151 is operating in the first mode (i.e., while the binary phase stepper 151 is applying the first phase offset to the RF reference signal to generate the RF test signal), control the phase shifter 110 to generate a first sequence of RF transmit signals. Each of the RF transmit signals, in this case, is based on applying each of a test set of phase offsets to the RF reference signal. The controller 180 also controls the ADC to sample the mixer output at a first plurality of sample times to provide a first sequence of digital samples, wherein each of the first sequence of digital samples corresponds to a respective one of the first sequence of RF transmit signals.

[0043] Essentially, to determine transmit path phase and amplitude information for adjusting phase shifter 110 (e.g., for applying an X-degree offset by phase shifter 110), phase stepper 151 is controlled to apply only one phase offset to the RF reference signal to generate the RF test signal. To collect sufficient information to determine the phase and amplitude information, phase shifter 110 is controlled to cycle through a plurality of test phase offsets.

[0044] That is, instead of cycling the phase stepper 150 through a large number of settings (which requires a phase stepper 150 capable of applying a large number of phase offsets), the phase shifter 110 is controlled to cycle through a number of settings. For example, the phase shifter 110 can be controlled to apply a test phase offset in addition to the phase offset setting being evaluated (e.g., X degrees), applying a first test phase offset (e.g., 0 degrees), a second test phase offset (e.g., 90 degrees), a third test phase offset (e.g., 180 degrees), and a fourth test phase offset (e.g., 270 degrees). Of course, the ADC can be controlled to generate digital samples, each digital sample corresponding to a mixer output, when the phase shifter 110 is controlled to apply each of these test phase offsets.

[0045] The above examples should not be considered limiting, and alternative test phase offsets may be applied. However, it can simplify subsequent processing / calculations by having a set of equidistant phase offsets, such as 0, 90, 180, and 270 degrees.

[0046] In other words, instead of the procedure for extracting a phase measurement of the phase shifter 110 described above, the following procedure for calculating phase and amplitude information for a setting of the phase shifter 110 is proposed: (i) the phase stepping device is controlled by the switch to operate in a first mode in which a first phase offset (e.g., 0-degree phase offset or 90-degree phase offset) is applied to the RF reference signal to generate the RF test signal; (ii) the phase shifter 110 is controlled to apply one of the plurality of test phase offsets to the RF reference signal to generate an RF transmit signal (and thus a specific RF feedback signal). The test phase offsets may comprise equidistant phase offsets. For example, the test phase offsets may comprise four equidistant phase offsets (e.g., X + 0, 90, 180, and 270 degrees); (iii) for each test phase offset applied by the phase stepper 110 (and after the signals have settled), the ADC is controlled to generate a digital sample by sampling the mixer output signal; (iv) Once all digital samples have been generated, an FFT is applied to the digital samples. For example, if four equidistant phase offsets are applied by the phase stepper 110, a simple 4-point FFT can be applied, requiring only basic arithmetic operations to be applied to the four digital samples; (v) Phase and amplitude information extracted from the first harmonic of the FFT.

[0047] Thus, it was recognized that it is only necessary to provide one phase stepper 151 that has two operating modes (i.e., capable of applying only two phase offsets to the RF reference signal). This greatly reduces the complexity of the phase stepper 151, thereby saving silicon space and reducing power consumption.

[0048] In one example, phase stepper 151 is configured to apply a 0-degree phase offset to the RF reference signal, and phase shifter 110 is configured to apply 0-, 90-, 180-, and 270-degree test phase offsets in addition to the X-degree setting of phase stepper 110 being evaluated. In this case, four digital samples are generated. Sig1 denotes the digital signal value associated with phase shifter 110 applying a 0-degree test phase offset, Sig2 denotes the digital signal value associated with phase shifter 110 applying a 90-degree test phase offset, Sig3 denotes the digital signal value associated with phase shifter 110 applying a 180-degree test phase offset, and Sig4 denotes the digital signal value associated with phase shifter 110 applying a 270-degree test phase offset.

[0049] In this case, a very simple four-point FFT can be calculated as follows: Re1=Sig1−Sig3 Im1=−(Sig2−Sig4)

[0050] Thus, by applying simple arithmetic functions to the voltages represented by the digital samples, the phase and amplitude information can then be easily extracted from the Re1+j*lm1 signal.

[0051] This is, of course, a simplified example of how this procedure can be performed. Alternative test phase offsets can be applied, from which phase and amplitude information can be derived. Nevertheless, the above example provides a very simple and therefore fast and energy-efficient means of measuring the phase and amplitude information of the transmit path, corresponding to the phase shifter 110 operating according to a given setting.

[0052] The RF transmitter arrangement 100 may therefore include a processor 180 configured to receive the first sequence of digital samples and generate phase and amplitude information of the RF transmit signal based on a result of processing the first set of digital samples with a discrete Fourier transform.

[0053] Processor 180 may then be further configured to modify an operating parameter of phase shifter 110 and / or generate a signal indicating a failure of phase shifter 110 based on the generated phase and amplitude information. That is, if the generated phase and amplitude information does not correspond to expected values, action may be taken to report and correct the operation of phase shifter 110.

[0054] According to a further aspect of the present invention, a method for evaluating the performance of an RF transmitter arrangement is provided which is faster than existing methods. This method is described in Fig. 3 is presented in the form of a flow chart.

[0055] In a prior art implementation, the behavior / function of the phase shifter of an RF transmitter array is typically evaluated by measuring phase and amplitude information of the transmit path (in a manner as described above) for each phase shifter phase setting to be used. However, it should be noted that this is very time-consuming, as many phase shifter settings may need to be evaluated, and each measurement of the phase and amplitude information requires time.

[0056] To combat this, it has recently been proposed to skip measuring phase and amplitude information for less important phase shifter settings. That is, only phase measurements of the most important phase shifter settings are taken, assuming correct operation for less important settings when the important settings are operated correctly. However, this assumption can lead to errors.

[0057] Accordingly, the proposed method proposes a small extension of the measurement procedure described above to provide a rapid means of evaluating the behavior of the RF transmitter array while avoiding the introduction of undesirable assumptions.

[0058] It will be appreciated that the proposed method may be performed on the RF transmitter arrangement as described above, which comprises a binary phase stepper operable in only two modes, but may equally be applied to an RF transmitter arrangement having a phase stepper operable in more than two modes (but may not require the use of more than two modes of such a phase stepper).

[0059] In other words, the RF transmitter arrangement comprises a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal. The RF transmitter also includes a coupler configured to couple the RF transmit signal to a transmit antenna and to extract a portion of the RF transmit signal to generate an RF feedback signal. Further, a phase stepper is provided configured to receive the RF reference signal and to generate an RF test signal based on applying one or a plurality of test phase offsets to the RF reference signal. In some embodiments, the phase stepper is a binary phase stepper, as in Fig. 2. Finally, the RF transmitter assembly includes a mixer configured to receive the RF test signal and the RF feedback signal and to mix the RF test signal and the RF feedback signal to generate a mixer output signal.

[0060] In step 210, the phase stepper applies a first phase offset to the RF reference signal. Accordingly, the phase stepper generates an RF test signal with the first phase offset and provides the RF test signal to the mixer. The first phase offset may be 0 degrees, for example. However, examples are not limited to 0 degrees.

[0061] While the phase stepper applies the first phase offset to the RF reference signal, the phase shifter is controlled in step 220 to generate a first sequence of RF transmit signals. Each of the RF transmit signals is based on applying each of a test set of phase offsets to the RF reference signal. In this way, a sequence of RF feedback signals is generated and provided to the mixer, while the RF test signal with the first phase offset is also provided to the mixer.

[0062] In step 230, the phase stepper applies a second phase offset to the RF reference signal. Accordingly, the phase stepper generates an RF test signal with the second phase offset and provides the RF test signal to the mixer. The second phase offset may be, for example, 90 degrees. However, examples are not limited to 90 degrees, as long as the second phase offset differs from the first phase offset.

[0063] While the phase stepper applies the second phase offset to the RF reference signal, the phase shifter is controlled in step 240 to generate a second sequence of RF transmit signals. Each of the RF transmit signals is based on applying each of the test set of phase offsets to the RF reference signal. In this way, a sequence of RF feedback signals is generated and provided to the mixer, while the RF test signal with the second phase offset is also provided to the mixer.

[0064] The test set of phase offsets may include equidistant phase offsets. For example, the test set of phase offsets may include four equidistant phase offsets, such as 0, 90, 180, and 270 degrees.

[0065] It should be noted that steps 210-240 can be performed in different orders. For example, the phase shifter can be set to apply one of the test set of phase offsets, while the phase stepper is controlled to apply the first and second phase offsets sequentially. In any case, the phase stepper and the phase shifter must be controlled so that the mixer receives a complete combination of the RF feedback signals with the test phase offsets and the RF test signal with the first and second phase offsets.

[0066] In step 250, the mixer output is sampled at a plurality of sample times to provide a sequence of digital samples. That is, the mixer combines the input RF test signal and RF feedback signal, and the resulting output is sampled at a number of different times. Each of the sequences of digital samples corresponds to a respective one of the first sequence of RF transmit signals or one of the second sequence of RF transmit signals. That is, the mixer output is sampled for each combination of the first or second sequence of RF transmit signals from the phase shifter and the test signals from the phase stepper. Accordingly, a sequence of digital samples is obtained for the complete combination of the two phase stepper settings and the phase shifter test settings.

[0067] To be clear, each digital sample corresponds to a downconverter signal with an amplitude that depends on the phase difference between the RF feedback signal and the RF test signal at the time the sample is taken by the mixer. This sampling can be performed, for example, by an ADC.

[0068] In step 260, a discrete Fourier transform is applied to the sequence of digital samples to generate a plurality of DFT bin values. Each DFT bin value corresponds to different harmonics present in the sequence of digital samples. The DFT bin values ​​include at least one DC amplitude value of the sequence of samples (i.e., a zero-order harmonic amplitude value), a first harmonic amplitude value of the sequence of samples, and a third harmonic amplitude value of the sequence of samples.

[0069] In step 270, a defect of the phase shifter is identified based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value.

[0070] For example, if the magnitude of the first harmonic amplitude value is much larger than the DC amplitude value and the third harmonic amplitude value, this would indicate that the phase shifter is operating normally. If this is not the case, the relative proportions between the magnitude of the DC, first harmonic, and third harmonic amplitude values ​​indicate a failure and can also reveal the nature and / or source of the failure.

[0071] This means that if the phase shifter malfunctions, the DC and third harmonic components may become large and / or the first harmonic component may become unacceptably small. Thus, these values ​​can be compared against a variety of pass / fail conditions to identify a fault. Specifically, if the first harmonic amplitude value fails a first harmonic condition, the DC amplitude value satisfies a DC failure condition, and / or the third harmonic amplitude value satisfies a third harmonic (i.e., image) failure condition, then a fault can be identified.

[0072] However, embodiments are not limited to this, and a combination of the DFT bin values ​​may be processed to identify a failure (e.g., a summation of the DC amplitude value and the third harmonic amplitude value, etc.). The conditions by which failure or success is evaluated may depend on the specific application.

[0073] Although not shown, the method may then include further steps of modifying the operation of the phase shifter based on the identified defect. Thus, the method may provide a means for automatically correcting / calibrating a phase shifter. Additionally or alternatively, an output signal may be generated indicating a failure of the phase shifter based on the identified phase shifter defect.

[0074] It should be noted that the above procedure is based on the Fig.1 described controller / processor.

[0075] As a specific example, the first phase offset is a 0-degree phase offset (i.e., the phase stepper applies a 0-degree offset to the RF reference signal), and the second phase offset is a 90-degree phase offset (i.e., the phase stepper applies a 90-degree offset to the RF reference signal). The test set of phase offsets applied by the phase shifter to the RF reference signal includes 0-, 90-, 180-, and 270-degree phase offsets. Essentially, the process performs the measurement procedure described above, but under conditions where the phase stepper applies a 0-degree phase offset as well as a 90-degree phase offset.

[0076] In particular, four digital samples are generated for each setting of the phase stepper, resulting in a total of eight digital samples. 1...4denotes the digital signal values ​​associated with the phase stepper applying a 90-degree test phase offset while the phase shifter applies each of the test set phase offsets (e.g., Sin2 denotes the digital sample value generated when the phase stepper applies the 90-degree phase offset and the phase shifter applies the 90-degree phase offset). Cos 1...4 denotes the digital signal values ​​associated with the phase stepper applying a 0-degree test phase offset while the phase shifter applies each of the test set phase offsets (e.g., Cos3 denotes the digital sample value generated when the phase stepper applies the 0-degree phase offset and the phase shifter applies the 180-degree phase offset).

[0077] In this case, applying the DFT to generate the DFT bin values ​​involves calculating a four-point complex FFT. Due to the choice of phase stepper settings and the test set of phase offsets chosen in this example, only sum operands are required, meaning the process of applying the Fourier transform is computationally efficient and fast.

[0078] In particular, the DC component can be calculated by: Re0=cos1+cos2+cos3+cos4 Im0=sin1+sin2+sin3+sin4

[0079] The first harmonic component can be calculated by: Re1=cos1+sin2−cos3−sin4 Im1=sin1−cos2−sin3+cos4

[0080] The third harmonic component can be calculated by: Re3=cos1−sin2−cos3+sin4 Im3=sin1+cos2−sin3−cos4

[0081] Thus, by applying simple arithmetic functions to the voltages represented by the digital samples, the various harmonic components can be easily extracted from the cos 1...4 - and are 1...4 -signals can be derived.

[0082] As shown, the main advantage of the extended procedure is that no additional measurement is required to monitor the correct functionality of the phase shifter beyond repeating the measurement for two phase-step device settings. In other words, it is not necessary to cycle through each phase shifter setting in use to determine the correct operation of the phase shifter. Essentially, the number of measurements that must be taken to derive the phase shifter's behavior is minimized. Therefore, minimal additional power consumption is required for monitoring.

[0083] In addition to the examples described above, the following examples are disclosed.

[0084] Example 1 is an RF transmitter arrangement comprising: a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal; a coupler configured to couple the RF transmit signal to a transmit antenna and to couple out a portion of the RF transmit signal to generate an RF feedback signal; a binary phase stepper configured to receive the RF reference signal and to generate an RF test signal, wherein the phase stepper is configured to be operable in a first mode in which the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal, and in a second mode in which the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal, wherein the first phase offset is different from the second phase offset; and a mixer configured to receive the RF test signal and the RF feedback signal, and to mix the RF test signal and the RF feedback signal to generate a mixer output signal.

[0085] Example 2 is the RF transmitter arrangement according to Example 1, further comprising: an analog-to-digital converter, ADC, configured to sample the mixer output signal to generate digital samples; and a controller configured to: while the binary phase stepper is operating in the first mode, controlling the phase shifter to generate a first sequence of RF transmit signals, each of the RF transmit signals being based on applying each of a test set of phase offsets to the RF reference signal; and controlling the ADC to sample the mixer output at a first plurality of sample times to provide a first sequence of digital samples, each of the first sequence of digital samples corresponding to a respective one of the first sequence of RF transmit signals.

[0086] Example 3 is the RF transmitter arrangement of Example 2, further comprising a processor configured to receive the first sequence of digital samples and generate phase and amplitude information of the RF transmit signal based on a result of processing the first set of digital samples with a DFT.

[0087] Example 4 is the RF transmitter assembly of Example 3, wherein the processor is further configured to modify an operating parameter of the phase shifter and / or generate a signal indicative of a failure of the phase shifter based on the generated phase and amplitude information.

[0088] Example 5 is the RF transmitter assembly of any of Examples 2-4, wherein the controller is further configured to: while the binary phase stepper is operating in the second mode, controlling the phase shifter to generate a second sequence of RF transmit signals by applying each of the plurality of phase offsets; and controlling the ADC to sample the mixer output at a second plurality of sample times to provide a second sequence of digital samples, each of the second sequence of digital samples corresponding to a respective one of the second sequence of RF transmit signals.

[0089] Example 6 is the RF transmitter assembly of Example 5, further comprising a processor configured to: receive the first sequence of digital samples and the second sequence of digital samples; applying a DFT to the first sequence of digital samples and the second sequence of digital samples to generate a plurality of DFT bin values, each DFT bin value corresponding to different harmonics present in the first sequence of digital samples and the second sequence of digital samples.

[0090] Example 7 is the RF transmitter arrangement of Example 6, wherein the DFT bin values ​​include a DC amplitude value of the sequence of samples, a first harmonic amplitude value of the sequence of samples, and a third harmonic amplitude value of the sequence of samples. In this case, the processor is further configured to identify a defect of the phase shifter based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value.

[0091] Example 8 is the RF transmitter assembly of Example 7, wherein the processor is further configured to generate an error signal in response to the identified DC amplitude satisfying a DC failure condition, the identified first harmonic amplitude value satisfying a first harmonic condition, and / or the identified third harmonic satisfying a third harmonic failure condition.

[0092] Example 9 is the RF transmitter assembly of any one of examples 7 or 8, wherein the processor is further configured to modify an operating parameter of the phase shifter and / or generate a signal indicative of a failure of the phase shifter based on the identified defect of the phase shifter.

[0093] Example 10 is the RF transmitter arrangement of any one of Examples 3-9, wherein applying the DFT comprises processing the sequence of digital samples using only arithmetic and geometric functions and / or approximations.

[0094] Example 11 is the RF transmitter assembly of any one of Examples 1-10, wherein a difference between the first phase offset and the second phase offset of the binary phase stepping device is 90 degrees.

[0095] Example 12 is the RF transmitter arrangement of any one of Examples 1-11, wherein the test set of phase offsets comprises equidistant phase offsets.

[0096] Example 13 is a method for evaluating the performance of an RF transmitter assembly. The RF transmitter assembly includes: a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal; a coupler configured to couple the RF transmit signal to a transmit antenna and to extract a portion of the RF transmit signal to generate an RF feedback signal; a phase stepper configured to receive the RF reference signal and to generate an RF test signal based on applying one or a plurality of test phase offsets to the RF reference signal; and a mixer configured to receive the RF test signal and the RF feedback signal, and to mix the RF test signal and the RF feedback signal to generate a mixer output signal.The procedure has:. while the phase stepper applies a first phase offset to the RF reference signal, controlling the phase shifter to generate a first sequence of RF transmit signals, each of the RF transmit signals being based on applying each of a test set of phase offsets to the RF reference signal; while the phase stepper applies a second phase offset to the RF reference signal, controlling the phase shifter to generate a second sequence of RF transmit signals, each of the RF transmit signals being based on applying each of a test set of phase offsets to the RF reference signal; sampling the mixer output at a plurality of sampling times to provide a sequence of digital samples, each of the sequence of digital samples corresponding to a respective one of the first sequence of RF transmit signals or one of the second sequence of RF transmit signals; Applying a discrete Fourier transform, DFT, to the sequence of digital samples to generate a plurality of DFT bin values, each DFT bin value corresponding to different harmonics present in the sequence of digital samples, the DFT bin values ​​comprising a DC amplitude value of the sequence of samples, a first harmonic amplitude value of the sequence of samples, and a third harmonic amplitude value of the sequence of samples; and Identifying a defect of the phase shifter based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value.

[0097] Example 14 is the method of Example 13, further comprising modifying an operation of the phase shifter based on the identified defect of the phase shifter.

[0098] Example 15 is the method of example 13 or 14, further comprising generating an output signal indicative of a failure of the phase shifter based on the identified defect of the phase shifter.

[0099] Example 16 is the method of any one of Examples 13-15, further comprising generating phase and amplitude information of the RF transmit signal based on a result of processing the sequence of digital samples with a DFT.

[0100] Example 17 is the method of any one of Examples 13-16, wherein the test set of phase offsets comprises equidistant phase offsets.

[0101] Example 18 is the method of any one of Examples 13-17, wherein the phase stepper is a binary phase stepper configured to be operable in a first mode in which the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal, and in a second mode in which the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal. The method further comprises: Controlling the phase stepping device to operate in the first mode while controlling the phase shifter to generate the first sequence of RF transmit signals; and Controlling the phase stepper to operate in the second mode while controlling the phase shifter to generate the second sequence of RF transmit signals.

[0102] Example 19 is the method of Example 18, wherein a difference between the first phase offset and the second phase offset of the binary phase stepper is 90 degrees.

[0103] Although specific examples have been illustrated and described herein, those skilled in the art will recognize that a variety of alternative and / or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific examples discussed herein. Therefore, it is intended that this invention be limited only by the claims and their equivalents.

[0104] It should be noted that the methods and devices, including their preferred embodiments, as set forth in this document can be used alone or in combination with the other methods and devices disclosed in this document. In addition, the features set forth in connection with one device are also applicable to a corresponding method, and vice versa. Furthermore, all aspects of the methods and devices set forth in this document can be combined in any desired manner. In particular, the features of the claims can be combined with one another in any desired manner.

[0105] It should be noted that the description and drawings merely illustrate the principles of the proposed methods and systems. Those skilled in the art will be able to implement various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and embodiments set forth in this document are primarily intended to be expressly provided for illustrative purposes only to assist the reader in understanding the principles of the proposed methods and systems. Furthermore, all statements herein that provide principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to include their equivalents.

[0106] In the claims, any reference signs placed in parentheses should not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The embodiments may be implemented using hardware comprising a plurality of different elements. In a device claim enumerating a plurality of means, a plurality of those means may be embodied by one and the same hardware element. The mere fact that certain measures are listed in mutually different dependent claims does not indicate that a combination of those measures cannot be used. Furthermore, in the appended claims, lists comprising "at least one of: A; B; and C" should be construed as (A and / or B) and / or C.

Claims

[1] High frequency, RF, transmitter arrangement, comprising: a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal; a coupler configured to couple the RF transmit signal to a transmit antenna and to couple out a portion of the RF transmit signal to generate an RF feedback signal; a binary phase stepper configured to receive the RF reference signal and to generate an RF test signal, the phase stepper configured to be operable in a first mode in which the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal, and in a second mode in which the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal, the first phase offset being different from the second phase offset; a mixer configured to receive the RF test signal and the RF feedback signal, and to mix the RF test signal and the RF feedback signal to generate a mixer output signal; an analog-to-digital converter, ADC, configured to sample the mixer output signal to generate digital samples; and a controller configured to: while the binary phase stepper is operating in the first mode, to control the phase shifter to generate a first sequence of RF transmit signals, each of the RF transmit signals being based on applying each of a test set of phase offsets to the RF reference signal, and while the binary phase stepper is operating in the second mode, to control the phase shifter to generate a second sequence of RF transmit signals by applying each of the plurality of phase offsets; and controlling the ADC to sample the mixer output at a first plurality of sample times to provide a first sequence of digital samples, each of the first sequence of digital samples corresponding to a respective one of the first sequence of RF transmit signals, and controlling the ADC to sample the mixer output at a second plurality of sample times to provide a second sequence of digital samples, each of the second sequence of digital samples corresponding to a respective one of the second sequence of RF transmit signals, a processor configured to receive the first sequence of digital samples and the second sequence of digital samples, apply a discrete Fourier transform, DFT, to the first sequence of digital samples and to the second sequence of digital samples to generate a plurality of DFT bin values, wherein the DFT bin values ​​include a DC amplitude value of the sequence of samples, a first harmonic amplitude value of the sequence of samples, and a third harmonic amplitude value of the sequence of samples, and wherein the processor is further configured to identify a defect of the phase shifter based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value. [2] The RF transmitter assembly of claim 1, wherein the processor is further configured to modify an operating parameter of the phase shifter and / or generate a signal indicating a failure of the phase shifter based on the generated phase and amplitude information. [3] The RF transmitter assembly of claim 1 or 2, wherein the processor is further configured to generate an error signal in response to the identified DC amplitude satisfying a DC failure condition, the identified first harmonic amplitude value satisfying a first harmonic condition, and / or the identified third harmonic satisfying a third harmonic failure condition. [4] The RF transmitter assembly of any one of claims 1 to 3, wherein the processor is further configured to modify an operating parameter of the phase shifter and / or generate a signal indicating a failure of the phase shifter based on the identified defect of the phase shifter. [5] An RF transmitter arrangement according to any one of claims 1 to 4, wherein applying the DFT comprises processing the sequence of digital samples using only arithmetic and geometric functions and / or approximations. [6] An RF transmitter arrangement according to any one of claims 1 to 5, wherein a difference between the first phase offset and the second phase offset of the binary phase stepping device is 90 degrees. [7] An RF transmitter arrangement according to any one of claims 1 to 6, wherein the test set of phase offsets comprises equidistant phase offsets. [8] A method for evaluating the performance of a radio frequency, RF, transmitter arrangement, the RF transmitter arrangement comprising: a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal; a coupler configured to couple the RF transmit signal to a transmit antenna and to extract a portion of the RF transmit signal to generate an RF feedback signal; a phase stepper configured to receive the RF reference signal and to generate an RF test signal based on applying one or a plurality of test phase offsets to the RF reference signal;and a mixer configured to receive the RF test signal and the RF feedback signal, and to mix the RF test signal and the RF feedback signal to generate a mixer output signal, the method comprising:; while the phase stepper applies a first phase offset to the RF reference signal, controlling the phase shifter to generate a first sequence of RF transmit signals, each of the RF transmit signals being based on applying each of a test set of phase offsets to the RF reference signal; while the phase stepper applies a second phase offset to the RF reference signal, controlling the phase shifter to generate a second sequence of RF transmit signals, each of the RF transmit signals being based on applying each of a test set of phase offsets to the RF reference signal; sampling the mixer output at a plurality of sampling times to provide a sequence of digital samples, each of the sequence of digital samples corresponding to a respective one of the first sequence of RF transmit signals or one of the second sequence of RF transmit signals; Applying a discrete Fourier transform, DFT, to the sequence of digital samples to generate a plurality of DFT bin values, each DFT bin value corresponding to different harmonics present in the sequence of digital samples, the DFT bin values ​​comprising a DC amplitude value of the sequence of samples, a first harmonic amplitude value of the sequence of samples, and a third harmonic amplitude value of the sequence of samples; and Identifying a defect of the phase shifter based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value. [9] The method of claim 8, further comprising modifying an operation of the phase shifter based on the identified defect of the phase shifter. [10] The method of claim 8 or 9, further comprising generating an output signal indicative of a failure of the phase shifter based on the identified defect of the phase shifter. [11] The method of any one of claims 8 to 10, further comprising generating phase and amplitude information of the RF transmit signal based on a result of processing the sequence of digital samples with a DFT. [12] A method according to any one of claims 8 to 11, wherein the test set of phase offsets comprises equidistant phase offsets. [13] The method of any one of claims 8 to 12, wherein the phase stepper is a binary phase stepper configured to be operable in a first mode in which the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal, and in a second mode in which the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal, and wherein the method further comprises Controlling the phase stepping device to operate in the first mode while controlling the phase shifter to generate the first sequence of RF transmit signals; and Controlling the phase stepper to operate in the second mode while controlling the phase shifter to generate the second sequence of RF transmit signals. [14] The method of claim 13, wherein a difference between the first phase offset and the second phase offset of the binary phase stepper is 90 degrees.

Images