Device and method for providing electrical signals for testing radio receivers

Abstract

Circuit arrangement for providing electrical signals for broadband testing of multi-channel radio direction finders, with several channels, each having a direct digital synthesizer (DDS) (21, 22, ... 2n), wherein the direct digital synthesizer (21, 22, ... 2n) outputs an electrical signal whose frequency and / or amplitude and / or phase is adjustable, and a control device (30) which outputs at least one control signal which is applied to at least one direct digital synthesizer (21, 22, ... 2n), wherein the control signal serves to adjust the frequency and / or the amplitude and / or the phase of the output signal of the direct digital synthesizer, wherein the control device (30) has a memory with at least one test program for a broadband test of a corresponding multi-channel radio direction finder, wherein a test program can be selected via the input device (32) and the control signals are output accordingly to the direct digital synthesizers which provide the multi-channel electrical signals required for testing the corresponding radio direction finder.

Description

[0001] The invention relates to a device and a method for providing or processing electrical signals for a broadband testing of radio receivers, in particular multi-channel radio direction finders.

[0002] In radio reception systems, and especially in radio direction finding systems, it is necessary to electrically test the receiving antennas and the receiving channels. To test the receiving channels, for example, a defined test signal can be applied as a simulated antenna signal to the receiver input to correct the amplitude and phase of the receiving channel.

[0003] DE 29 52 220 A1 describes a goniometer for testing a direction finder. N / S, E / W, and auxiliary antenna voltages are generated for the three channels of the direction finder using a power divider, controllable phase shifters, and controllable attenuators. Diodes are primarily used for control. An external measuring transmitter is required as a frequency generator. This arrangement is very complex in terms of circuitry. Furthermore, this arrangement has limited application in terms of the frequency range, as many components are relatively narrowband.

[0004] DE 31 32 089 A1 relates to a method for the artificial generation of bearing signals for simulating various angles of incidence and phase positions. It proposes circumventing the narrowband nature of a known angle sensor by converting the output voltages of the angle sensor and those of an additional phase shifter into the desired output frequency by mixing them with an alternating voltage of variable frequency. This also requires an external measuring transmitter.

[0005] The disadvantages of the previously discussed publications are essentially that the circuit complexity is already relatively high for just three channels. In a multi-channel application, such as a 9-channel radio reception system, the complexity increases considerably.

[0006] The object of the present invention is to provide a device, in particular a circuit arrangement and a method for testing radio receivers and in particular multi-channel radio direction finders.

[0007] The object is achieved by the features of the claims. One aspect of the invention is based on the use of a direct digital synthesizer (DDS) with an electrical output signal whose frequency and / or amplitude and / or phase can be adjusted. The device or circuit arrangement preferably has a plurality of channels, each of which preferably has a DDS that outputs an individually adjustable output signal. One DDS that outputs an output signal is preferably used for each channel of a radio receiver to be tested. A clock signal generated by a clock generator can be supplied to the DDS in all channels of the circuit arrangement.

[0008] Furthermore, at least one control signal output by an optional control device can be applied to the at least one DDS. The control signal can be used to adjust the frequency and / or the amplitude and / or the phase of the output signal of the DDS. The control device can, for example, output two or more control signals, each of which is applied to at least one DDS of at least two channels, wherein at least two DDSs are controlled such that the amplitude and / or the phase of the output signal of the at least two DDSs is different. The frequency of the output signals of the at least two direct digital synthesizers is preferably the same. Short description of the characters

[0009] By way of example, illustrative, non-limiting embodiments of the present invention will be described with reference to the accompanying drawings, in which the same reference numeral is used to designate the same or similar components in different figures. In the drawings: Fig. 1 is a block diagram of a circuit arrangement according to the invention according to a first embodiment; and Fig. 2 a block diagram of an extended circuit arrangement according to a preferred embodiment of the invention. Detailed description

[0010] In Fig. 1 shows a first embodiment of a circuit arrangement according to the invention. An oscillator signal, which is generated by a clock generator, for example by a quartz oscillator 10, optionally serves as a clock signal for all direct digital synthesizers (DDS) 21, 22, ... 2n together, i.e. the clock signal is fed to all channels of the circuit arrangement. The DDS is controlled by means of a control device 30 such that the frequencies and / or the amplitudes and / or the phase positions, optionally to the common clock, can be set separately for all DDS. The control device 30 outputs at least one control signal, preferably it outputs n control signals, i.e. one control signal each to a DDS of a channel of the circuit arrangement.

[0011] The maximum frequency that can be generated using a DDS depends on the frequency of clock signal 1 and is slightly less than half the clock frequency. Depending on the selected DDS, frequencies of several hundred MHz can currently be generated. The lowest frequency that can be generated is practically 0 Hz.

[0012] The control device 30 can also output at least two control signals, which are applied to at least one DDS 21, 22, ... 2n of at least two of the n channels 1, 2, ... n. At least two DDSs can be controlled such that the amplitude and / or phase of the output signal of the at least two DDSs is different, wherein the frequency of the output signal of the at least two direct digital synthesizers is preferably the same. This allows a signal to be provided at the outputs 51, 52, ... 5n that simulates antenna signals of a direction-finding antenna system upon reception of a radio signal at a specific angle of incidence. These output signals are applied to the corresponding inputs of the channels of a radio receiver to be tested.

[0013] The control device 30 preferably has an input device 32. A user can use the input device to select the control signals to be output to the DDS and to set the desired frequency and / or amplitude and / or phase of the output signal of the controlled direct digital synthesizer. The control device 30 can have a memory with at least one test program to perform a broadband test of a corresponding multi-channel radio receiver. A test program can preferably be selected using the input device 32, and the test program outputs the corresponding control signals to the direct digital synthesizers, which provide the multi-channel electrical signals required to test the corresponding radio receiver.

[0014] Preferred embodiments of the method according to the invention are described below. The test programs are mentioned only as examples.

[0015] Preferably, a test program controls the DDS of several channels in such a way that the output signals of the DDS simulate the antenna signals of a direction finding antenna system that arise when a radio signal is received at one or more specific angles of incidence.

[0016] According to a preferred embodiment, the control device 30 can successively provide control signals with which the direct digital synthesizers 21, 22, ... 2n successively provide output signals whose amplitudes are adjusted according to the desired angle of incidence of a radio signal received by the direction finding antenna system and whose phases are adjusted according to the desired phase positions of the radio signal relative to one another.

[0017] Alternatively, using an additional test program, control signals can be output to the direct digital synthesizers from multiple channels. The amplitudes and phase angles are fixed for a specific angle of incidence of a simulated radio signal, and the frequencies of the output signals are varied equally for all operating channels. The output signals can be used to test the frequency dependence of a direction-finding system.

[0018] To provide a test signal for measuring the intermodulation of a receive channel, the control device 30 can apply control signals to at least two direct digital synthesizers 21, 22, ...2n using a further test program, whereby the two direct digital synthesizers output signals at different frequencies. The amplitudes of the output signals are preferably equal. The magnitude of the amplitude is varied successively, and the two output signals are combined using a summing device.

[0019] Low-pass filters 41, 42, ... 4n are used for optional filtering of the DDS output signals. This can be used, for example, to suppress the clock frequency or attenuate harmonics. The signals for testing multiple channels of a radio receiver are available at the circuit's outputs 51, 52, ... 5n, which are electrically connected to the DDS or the low-pass filters. Fig. Channels 1 to n are shown in Figure 1. The arrangement can be applied to any number of channels, e.g., three channels.

[0020] In Fig.Figure 2 shows an expanded circuit arrangement with which the output signals 51, 52, ... 5n generated by the DDSs are transformed into a higher-frequency range 51', 52', ... 5n' using mixers 61, 62, ... 6n, i.e., the output signals are output at a higher frequency. The mixer signals, which are generated, for example, by an external measuring transmitter 8, are preferably synchronized with the clock signal of the oscillator 10 for the DDSs 21, 22, ... 2n.

[0021] Optionally, the output signal of the mixer 61, 62, ...6n can be applied to a bandpass filter 71, 72, ...7n in each channel. The bandpass filter provides a filtered output signal 51', 52', ...5n'. The output signals of this extended circuit arrangement can be used to test the multiple channels of a radio receiver in the higher frequency range.

[0022] The above explanations relate to examples for implementing the invention. Modifications and extensions are possible for those skilled in the art. Preferably, switching to the extended circuit arrangement and thus to the higher-frequency range occurs automatically, e.g., during the execution of a test program. Furthermore, multiple extensions can be provided for respective frequency ranges.

Claims

[1] Circuit arrangement for providing electrical signals for a broadband test of multi-channel radio direction finders, with a plurality of channels, each having a direct digital synthesizer (DDS) (21, 22, ... 2n), wherein the direct digital synthesizer (21, 22, ... 2n) outputs an electrical signal whose frequency and / or amplitude and / or phase is adjustable, and a control device (30) which outputs at least one control signal which is applied to at least one direct digital synthesizer (21, 22, ... 2n), the control signal serving to adjust the frequency and / or the amplitude and / or the phase of the output signal of the direct digital synthesizer, wherein the control device (30) has a memory with at least one test program for a broadband test of a corresponding multi-channel radio direction finder, wherein a test program can be selected via the input device (32) and the control signals are correspondingly output to the direct digital synthesizers which provide the multi-channel electrical signals required for testing the corresponding radio direction finder. [2] Circuit arrangement according to claim 1, comprising a clock generator (10) which supplies a clock signal which is preferably supplied to the direct digital synthesizer (21, 22, ... 2n) in all channels. [3] Circuit arrangement according to claim 1 or 2, wherein the control device (30) outputs at least two control signals which are applied to at least one direct digital synthesizer (21, 22, ... 2n) of at least two channels (1, 2, ... n), wherein at least two direct digital synthesizers are controlled such that the amplitude and / or the phase of the output signal of the at least two direct digital synthesizers is different, wherein preferably the frequency of the output signal of the at least two direct digital synthesizers is the same. [4] Circuit arrangement according to claim 1 or 2, wherein the control device (3) has an input device (32) for selecting the control signals to be output to the direct digital synthesizers (21, 22, ... 2n) and for setting the respectively desired frequency and / or the amplitude and / or the phase of the output signal of the controlled direct digital synthesizer. [5] Circuit arrangement according to one of claims 1 to 4, wherein the control device (30), preferably controlled by a selected test program, controls the direct digital synthesizers of a plurality of channels in such a way that the output signals output by the direct digital synthesizers simulate the antenna signals of a direction finding antenna system which arise when a radio signal is received at a certain angle of incidence. [6] Circuit arrangement according to claim 5, wherein the control device (30) provides successive control signals with which the direct digital synthesizers (21, 22, ... 2n) successively output output signals whose amplitudes are adjusted according to the desired angle of incidence of a radio signal received by the direction finding antenna system and whose phases are adjusted according to the desired phase positions of the radio signal relative to one another. [7] Circuit arrangement according to one of claims 5 or 6, wherein the control device (30) preferably outputs control signals to the direct digital synthesizers of several channels by means of a further test program, wherein the amplitudes for a specific angle of incidence of a simulated radio signal and the phase positions are fixed and the frequencies of the output signals are varied equally for all operated channels, wherein the output signals can be used to test the frequency dependence of a direction finding system. [8] Circuit arrangement according to one of claims 5 to 7, wherein the control device (30) applies control signals to at least two direct digital synthesizers (21, 22, ...2n), preferably by means of a further test program, whereby the two direct digital synthesizers output output signals with different frequencies, wherein preferably the amplitudes of the output signals are of the same size, but the size of the amplitude is varied successively, and with a summing device with which the two output signals are connected together to provide a test signal for measuring the intermodulation of a receive channel. [9] Circuit arrangement according to one of claims 1 to 8, wherein in each channel the output signal of the direct digital synthesizer (21, 22, ...2n) is applied to a corresponding low-pass filter (41, 42, ...4n), and the low-pass filter outputs a filtered output signal (51, 52, ...5n). [10] Circuit arrangement according to one of claims 1 to 9, wherein in each channel the output signal of the direct digital synthesizer (21, 22, ...2n) or of the low-pass filter (41, 42, ...4n) is applied to an associated mixer (61, 62, ...6n), which mixes the output signal with a higher-frequency mixed signal and outputs an output signal with a higher frequency. [11] Circuit arrangement according to claim 10, wherein in each channel the output signal of the mixer (61, 62, ...6n) is applied to a bandpass filter (71, 72, ...7n) which outputs a filtered output signal (51', 52', ...5n'). [12] Circuit arrangement according to claim 10 or 11, wherein the higher-frequency mixed signal is provided by a measuring transmitter (8) which is preferably synchronized with the clock signal of the clock generator (10) for the direct digital synthesizers (21, 22, ...2n). [13] Method for providing electrical signals for a broadband test of multi-channel radio direction finders, comprising controlling a direct digital synthesizer (DDS) (21, 22, ... 2n) per channel and outputting an electrical signal whose frequency and / or amplitude and / or phase can be adjusted, outputting at least one control signal by means of a control device (30), wherein the control signal is applied to at least one direct digital synthesizer (21, 22, ... 2n) and the control signal serves to adjust the frequency and / or the amplitude and / or the phase of the output signal of the direct digital synthesizer, and selecting a test program for a broadband test of a corresponding multi-channel radio direction finder, and outputting corresponding control signals to the direct digital synthesizers that provide the multi-channel electrical signals required to test the corresponding radio direction finder. [14] Method according to claim 13, comprising supplying a clock signal to the direct digital synthesizer (21, 22, ... 2n), preferably in all channels. [15] Method according to claim 13 or 14, comprising outputting at least two control signals which are applied to at least one direct digital synthesizer (21, 22, ... 2n) of at least two channels (1, 2, ... n), wherein at least two direct digital synthesizers are controlled such that the amplitude and / or the phase of the output signal of the at least two direct digital synthesizers is different, wherein preferably the frequency of the output signal of the at least two direct digital synthesizers is the same. [16] Method according to claim 13 or 14, comprising selecting the control signals to be output to the direct digital synthesizers (21, 22, ... 2n) and setting the respectively desired frequency and / or the amplitude and / or the phase of the output signal of the controlled direct digital synthesizer by means of an input device. [17] Method according to one of claims 13 to 16, comprising controlling the direct digital synthesizers of a plurality of channels in such a way that the output signals output by the direct digital synthesizers simulate the antenna signals of a direction finding antenna system which are generated when a radio signal is received at a specific angle of incidence. [18] Method according to claim 17, comprising the successive provision of control signals with which the direct digital synthesizers (21, 22, ... 2n) successively output output signals whose amplitudes are adjusted according to the desired angle of incidence of a radio signal received by the direction finding antenna system and whose phases are adjusted according to the desired phase positions of the radio signal relative to one another. [19] Method according to one of claims 17 or 18, with the output of control signals to the direct digital synthesizers of several channels, wherein the amplitudes for a specific angle of incidence of a simulated radio signal and the phase positions are fixed and the frequencies of the output signals are varied equally for all operated channels, wherein the output signals can be used to test the frequency dependence of a direction finding system. [20] Method according to one of claims 13 to 19, comprising applying control signals to at least two direct digital synthesizers (21, 22, ...2n), whereby the two direct digital synthesizers output signals with different frequencies, wherein preferably the amplitudes of the output signals are equal, but the size of the amplitude is successively varied and with a summing device with which the two output signals are connected together to provide a test signal for measuring the intermodulation of a receive channel.

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