Method and arrangement for the broadband generation of IQ signals, particularly in multi-channel systems

Abstract

Method for the broadband generation of IQ signals, in which a reference signal is first doubled in frequency and then divided down again with a master-slave flip-flop (DIV2) in order to obtain an I component and a Q component of the reference signal, characterized in that the reference signal is additionally provided with a phase shift and is then mixed with the I component generated by the master-slave flip-flop and / or the Q component of the reference signal, wherein the phase shift is selected such that it at least approximately compensates for a phase shift caused by the frequency doubling and the division, and depending on an amplitude of a mixed signal obtained by the mixing, the I component and the Q component are either not rotated in phase or are rotated by 180° or are corrected.

Description

Technical application area

[0001] The present invention relates to a method and an arrangement for the broadband and synchronous generation of IQ signals, in particular in multi-channel systems, in which a reference signal is first doubled in frequency and then fed to a master-slave flip-flop in order to obtain an I component and a Q component of the reference signal.

[0002] Many applications, whether in radar or communications systems, require signals that are 90° out of phase with each other. Such signals are also known as quadrature or IQ signals. IQ signals can be generated, for example, directly via IQ oscillators or from a reference signal using a phase shifter. Phase shifters can be implemented actively or passively. Passive implementations have the disadvantage that they can only generate IQ signals in a narrowband. In contrast, active components offer an efficient way to generate IQ signals with an extremely wideband. State of the art

[0003] For the generation of broadband IQ signals, an arrangement is known in which a reference signal f ref,inFirst, the frequency is doubled with a frequency doubler X2 and then divided down again with a static divider or master-slave D flip-flop DIV2. The flip-flop DIV2 contains the I and Q signals, which are each fed to an output as output signals f out , Q , f out , I Such an arrangement is exemplified in Fig. 1 shown.

[0004] A disadvantage of this arrangement, however, is that such flip-flops, when configured as static dividers, contain feedback FB for dividing frequencies. This makes the flip-flop unstable without an input signal, causing the signal paths in the flip-flop to oscillate. If such a flip-flop is switched on, or the signal is briefly removed from its input and then reapplied, a phase uncertainty of the I / Q signals f arises. out , Q , f out,I, because the flip-flop can latch in either a high or a low state as its initial state. This gives the IQ signals an additional phase shift of either 0° or 180°.

[0005] In single-channel systems, this property is often negligible. However, in multi-channel systems, where each individual channel or channel bundle is required to generate its own I / Q signals from a reference signal, this inevitably leads to channel asynchrony, as the 0° / 180° phase uncertainty of the flip-flops is randomly distributed across all channels. This results in phase errors, and the individual channels are no longer synchronized with each other. Fig. Figure 2 shows an example of a block diagram of such a multi-channel system. The input reference signal f ref,inis first divided into N channels by a distribution network K. For each of these channels, the reference signal is then doubled in the frequency doubler X2 and subsequently divided down using a master-slave D flip-flop DIV2 as a static divider, resulting in an I and a Q component of the reference signal for each of the channels. In the example of the Fig. 2 is a phased array transmission system in which the IQ signals generated in this way are used to shift the phase of each transmission channel with a vector adder VA so that the signals emitted via the TX antennas can be focused in any direction using constructive interference. The vector adder VA is controlled by a suitable controller. Application in phased array systems is particularly interesting because beamforming of the transmission waves can increase the system dynamics and thus the range. It can also be used in multi-channel receivers where phase shifters, delays (delayed phase), or IQ signals in general are required for any purpose.

[0006] In such an application, where the synchronicity of the individual channels is of fundamental importance, the 0° / 180° phase uncertainty of the IQ signals prevents the use of the classic concept of Fig. 1 for the examples mentioned. Considering the phased array system from Fig. 2, the 0° / 180° phase uncertainty generates destructive interference of the electromagnetic transmission waves, which degrades the system performance.

[0007] Therefore, narrowband and passive components have been used to generate I / Q signals in multi-channel systems. However, as soon as a somewhat broader frequency range is to be covered, deviations from the target phase of the processed signals arise, and system performance deteriorates. Generating a stable and precise phase with passive components becomes more difficult the larger the desired frequency range.

[0008] For the Fig. In the multi-channel system shown in Figure 2, it is in principle possible to generate the IQ signals directly behind the reference oscillator, i.e., before signal distribution. This would ensure that the phase error of 0° or 180° would be the same in all channels and thus synchronous. However, this increases the wiring complexity in the distribution network and the risk of phase errors in the IQ signals due to this wiring. Therefore, it is optimal if each channel generates its own IQ signals, which have a precise, stable, and broadband 90° phase relationship to one another. This provides the vector adder with nearly perfect IQ signals, and beamforming becomes possible for this phased array system over a wide frequency range.Even with MIMO receivers, where each channel receives different signals from different antennas, each channel must have a separate IQ signal generation so that the signals of the individual channels can be phase-shifted or delayed synchronously with each other and thus processed.

[0009] JP 2005094113 A describes an arrangement and a method for generating IQ signals, in which a reference signal is first doubled in frequency and then fed to a clock input of a master-slave flip-flop in order to obtain an I component and a Q component of the reference signal.

[0010] US 7227346 B1 discloses a phase detection arrangement with two parallel channels and digital mixers, in which IQ components are formed in each channel. This arrangement is used, for example, in a phased array system. US 7502278 B1 describes a beamformer system in which IQ components are formed. The synchronized IQ components are provided using cascaded master-slave D flip-flops. US 2010 / 0260076 A1 also describes a phased array system with multiple channels. In one embodiment, IQ components are generated and fed to a vector adder. US 2010 / 0013527 A1 also describes a phased array system in which IQ components are formed and combined for multiple channels.

[0011] The object of the present invention is to provide a method and an arrangement for the broadband generation of IQ signals without 0° / 180° phase uncertainty. Description of the invention

[0012] The problem is solved by the method and the arrangement according to patent claims 1 and 6.

[0013] Advantageous embodiments of the method and the arrangement are the subject of the dependent patent claims or can be found in the following description and the embodiments.

[0014] In the proposed method, a reference signal is first doubled in frequency in a known manner according to the previously described classical concept and then fed to the clock input of a master-slave flip-flop, in particular a master-slave D flip-flop, to obtain an I component and a Q component of the reference signal. To avoid the phase uncertainty inherent in this principle, a solution is proposed in which the reference signal is additionally used with a phase shift in the signal processing.

[0015] In this solution, the master-slave flip-flop is operated in a known manner with feedback in the configuration as a static divider. The reference signal is additionally mixed with a phase shift with the I component and / or the Q component at the output of the master-slave flip-flop, whereby the phase shift of the reference signal is selected such that it at least approximately compensates for the frequency-dependent phase shift caused by the frequency doubling and the subsequent division. The amplitude of the mixed signal obtained by mixing the I component and the Q component with the phase-shifted reference signal then provides information about whether the I and Q components are either not present or are shifted in phase by 180°. The output signals of the mixers are then used to correct the phase of the I and Q signals. This can be done, for example, in the control logic of the vector adder as in Fig. 4 or with Gilbert cells as amplifiers for phase shift as in Fig. 3. In this way, it is ensured that the I and Q components obtained at the output of the arrangement or by the proposed method or the added I and Q signals behind the vector adder VA no longer exhibit a 0° / 180° phase uncertainty.

[0016] In the associated arrangement for the broadband generation of IQ signals with one or more signal channels, each signal channel has a frequency doubler and a master-slave flip-flop. The frequency doubler doubles the frequency of a reference signal applied to the arrangement's signal input and feeds it into the flip-flop's clock input. The flip-flop then provides an I component of the reference signal at a first output and a Q component at a second output.

[0017] In the proposed arrangement, the flip-flop comprises, in a known manner, the feedback path between the Q output of the slave and the data input of the master. At least one device for generating an additional phase is provided, to whose input the reference signal is applied. The output of this device for generating an additional phase is connected to a first input of a mixer, via whose second input the I component or Q component obtained at the first or second output of the flip-flop is supplied. The mixer thus mixes the I component or the Q component with the reference signal provided with an additional phase. The device for generating an additional phase is designed such that it provides the reference signal with an additional phase, which at least approximately compensates for the frequency-dependent phase shift caused by the frequency doubling and the down-sampling.The output or mixed signal obtained at the output of the mixer serves as the input signal for a device for phase correction by 0° or 180°, to which the first output with the I signal component and the second output with the Q signal component of the flip-flop are connected. This phase correction device is designed such that it either does not rotate the phase of the I component and the Q component by 180°, or corrects it accordingly, depending on the mixer's output signal. This device can be, for example, a Gilbert cell, one for the first and one for the second output of the flip-flop, which multiplies the I or Q signal by either +1 or -1, thus shifting it by 0° or 180°.Alternatively - for example when used in a phased array system - a vector adder can be used which knows the phase position of the I and Q signals and in whose control logic this is taken into account when setting the desired phase position in each channel and compensated accordingly.

[0018] Using this method and the associated arrangement, synchronous IQ signals are obtained in each channel of a multi-channel transmit or receive system. These signals are very stable and precise in phase over an extremely wide frequency range and can be used, for example, with a vector adder to specifically shift the signal phase of each channel. The lower cutoff frequency is 0 Hz, and the upper cutoff frequency is determined only by the system component with the lowest maximum operating frequency. In one implementation already implemented using silicon-germanium technology, frequencies of over 30 GHz were achieved. Through further optimizations or other semiconductor technologies such as InP, GaAs, etc., even higher frequencies can be achieved. Already published publications show circuit components in silicon-germanium that have reached 60 GHz and more as the upper cutoff frequency.The proposed method and the associated arrangement thus achieve signal synchronicity and extremely high bandwidth for multi-channel systems in which IQ signal generation is required.

[0019] The method and the associated arrangement can be used in all applications in which each channel of a multi-channel system requires stable and broadband IQ signal generation that is synchronous with all other channels. This is the case, for example, in phased array channels to operate beamforming with vector adders. Beamforming can be used in all transmission systems (radar, mobile communications, etc.). The proposed method and the proposed arrangement can also be used on the receiver side of (particularly multi-channel) radar or mobile communications systems, where each receiving channel receives signals from a different antenna and these signals are to be phase-shifted, modulated, or demodulated in each channel. Examples of this are the use in (particularly multi-channel) communication systems (e.g., methods that use orthogonal carriers (OFDM), QAM, Rake receivers) and radar systems (e.g.,for phased array beamforming, IQ receiver for image rejection), on the transmitter and receiver side. Short description of the drawings

[0020] The proposed method and the associated arrangement are explained in more detail below using exemplary embodiments in conjunction with the drawings. Herein: Fig. 1 an example of a classical broadband IQ signal generation according to the state of the art (includes 0° / 180° phase uncertainty of the I and Q output signals); Fig. 2 an example of a classical broadband IQ signal generation for a phased array transmission system according to the state of the art; Fig. 3 an example of an arrangement for broadband IQ signal generation according to the proposed method; and Fig. 4 the example of Fig. 3 in a multi-channel phased array transmission system. Ways to implement the invention

[0021] Fig. 1 shows an arrangement for the classical broadband IQ signal generation, in which a reference signal f ref,in First, the frequency is doubled in a frequency doubler X2 and then divided again with a master-slave D flip-flop DIV2. The flip-flop contains the I and Q signals, which are used as output signals f out , Q , f out , I can be output. The frequency-doubled input signal is connected in a known manner to the clock inputs CLK of the master and slave. The Q output of the slave is connected to the data input D of the master via a feedback path FB. As already explained in the introductory section, in such a system, a phase uncertainty occurs in the IQ signals at the output, which receive either a phase position of 0° or an additional phase position of 180°.

[0022] Fig. Figure 2 shows a multi-channel system according to the state of the art, in which this arrangement is used in each channel to generate the IQ signals. Due to the 0° / 180° phase uncertainty of the flip-flops, which occurs randomly in all channels, phase errors arise and the individual channels are no longer synchronized. Especially in a phased array transmission system, as used in Fig. As shown in Figure 2, this phase uncertainty leads to unwanted destructive interference of the electromagnetic transmission wave.

[0023] Fig. Figure 3 shows an example of an embodiment of an arrangement or method according to the present invention. In this example, the D flip-flop is operated as a static divider DIV2 with the feedback path FB. However, in this solution, a down-converter MixQ, MixI is used to convert the phase-shifted reference signal f ref,inwith the I or Q signal of the static divider DIV2. Here, it is important to delay the reference signal with a suitable device φ by the same phase as the signal passing through the frequency doubler X2 and the divider DIV2 in order to ensure the broadband nature of the IQ signal generation. The IQ signals initially still contain the 0° / 180° phase uncertainty at the output of the divider DIV2. At the output of the mixers MixQ, MixI, a DC signal is then obtained, which is either "high" or "low", depending on the phase position of the I and Q signals (either 0° or 180°). This information is then used to compensate for one of the two possible phase positions of the IQ signals (for example, 180°). This can be done, for example, as in Fig. 3, with amplifiers that rotate the signal by 180° if necessary. For example, a Gilbert cell can be used to multiply / mix the I or Q signal by +1 or -1. Another compensation option is shown in Fig. 4 is shown using the well-known phased array system. Here, the information about the phase position of the IQ signals is transferred via the mixers MixQ / MixI to the vector adder VA, whose control logic adjusts the phase change to its output in such a way that the phase uncertainty is compensated and the desired phase position of the transmitted signals is set. Thus, in this configuration, all IQ signals in all channels of a multi-channel system are synchronized to the reference signal. List of reference symbols X2 frequency doubler DIV2 Static divider / master-slave D flip-flop FB feedback D Data input CLK clock input Q Q output K Distribution network N Number of channels TX transmit antennas VA vector adder φ Device for generating an additional phase MixI Mixer MixQ mixer

Claims

[1] Method for the broadband generation of IQ signals, in which a reference signal is first doubled in frequency and then divided down again with a master-slave flip-flop (DIV2) in order to obtain an I component and a Q component of the reference signal, characterized by that the reference signal is additionally provided with a phase shift and is then mixed with the I component generated by the master-slave flip-flop and / or the Q component of the reference signal, wherein the phase shift is selected such that it at least approximately compensates for a phase shift caused by the frequency doubling and the division, and depending on an amplitude of a mixed signal obtained by the mixing, the I component and the Q component are either not rotated or are rotated by 180° in phase or are corrected. [2] Method according to claim 1, characterized bythat the rotation of the phase of the I component and the Q component is carried out using a Gilbert cell, which multiplies the I and Q components either by +1 or by -1. [3] Method according to claim 1 or 2, characterized by that the reference signal is divided into several channels for the operation of a multi-channel system, with the frequency doubling and the down-splitting or synchronisation taking place in each of the channels in order to generate for each channel an I component and a Q component of the reference signal synchronous with the other channels. [4] Method according to claim 3, characterized by that the generated I component and the generated Q component in each of the channels are fed to a vector adder (VA) for the operation of a phased array system. [5] Method according to claim 1, characterized bythat the reference signal is divided into several channels for the operation of a multi-channel system, wherein the frequency doubling and the division down take place in each of the channels in order to generate an I component and a Q component of the reference signal for each channel synchronously with the other channels, the generated I component and the generated Q component in each of the channels are fed to a vector adder (VA) for the operation of a phased array system and the rotation of the phase of the I component and the Q component takes place in the vector adder (VA) as a function of the amplitude of the mixed signal obtained by the mixing. [6] Arrangement for the broadband generation of IQ signals with one or more signal channels, each signal channel having a frequency doubler (X2) and a master-slave flip-flop (DIV2), which are designed and connected in such a way that a reference signal applied to a signal input of the arrangement is doubled in frequency by the frequency doubler (X2) and then fed to a clock input (CLK) of the master-slave flip-flop (DIV2), by which the reference signal doubled in frequency is divided down again and an I component of the reference signal is provided at a first output and a Q component of the reference signal is provided at a second output, characterized bythat furthermore at least one mixer (MixI, MixQ), a device for generating an additional phase (φ) and a device for phase correction are connected in the arrangement in such a way that a reference signal applied to the signal input is additionally mixed via the device for generating an additional phase (φ) and the mixer (MixI, MixQ) with the I component provided at the first output and / or the Q component of the reference signal provided at the second output and, depending on an amplitude of a mixed signal obtained by mixing, the I component and the Q component are either not rotated in phase or are rotated by 180° or corrected by the phase correction device, wherein the device for generating an additional phase (φ) is designed in such a way that it provides a reference signal applied to the signal input of the arrangement with a phase shift,which at least approximately compensates for the phase shift caused by frequency doubling and down-scaling. [7] Arrangement according to claim 6, characterized by that the phase correction device is formed by a Gilbert cell. [8] Arrangement according to claim 6, characterized by that the phase correction device is formed by a vector adder (VA). [9] Arrangement according to one of claims 6 to 8, characterized by that, when there are several signal channels, the phase correction devices of the individual signal channels are each coordinated with one another in such a way that the I components and Q components generated in each signal channel are synchronous with the I components and Q components of the other signal channels.

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