DE3044701A1 - Radio receiver with fast tuning over broad-band - is achieved by using coarse-tuned oscillator and fast-tuned oscillator - Google Patents

Abstract

The radio receiver has the frequency of its first oscillator (4) set digitally and variable automatically in coarse steps spaced equidistant over the width of the receive band. The bandwidth of the intermediate frequency output signals from the HF input circuit is at least equal to the width of the frequency step of the first oscillator. The intermediate frequency output signal is converted into a second intermediate frequency signal by mixing with a second oscillator (9) and then narrow band filtered. The second oscillator frequency is tuned rapidly and automatically over a band equal in width to the width of the first oscillator's frequency step. A unit with a screen displays the frequency spectrum of radio signals with cursor control and digital display.

Description

Receiver for radio reconnaissance

The invention relates to a receiver in the preamble of the claim 1 Type specified Such receivers in analog design have two requirements to meet, which oppose each other in the general case. On the one hand, the vote should be of a wide frequency range as quickly as possible, as the for the one-time By tuning the frequency range, the time required is decisive for the shortest Duration of a signal that can be reliably received. Quick tuning of the reception area however, has the disadvantage of insufficient frequency resolution in known receivers with himself. On the other hand, radio reconnaissance receivers have a high frequency resolution requires, in turn, generally at a slow tuning speed is coupled.

Known digital receivers in which the reception frequency is small Steps is tuned over the entire frequency range to be received although they have high frequency resolution, they are usually too slow to switch the frequency, since the settling time to the new frequency is relatively long is. Digital frequency synthesis circuits that have very short switching times, are very complex and come because of the costs associated with the effort many user cases not considered.

The requirements to be placed on a radio intelligence receiver and some embodiments of receivers are of the type described above Described in detail in "News from Rohde & Schwarz" 59, February / March 1973, pages 5-11.

The object of the present invention is to provide one for radio reconnaissance Specify suitable recipient, who with little effort both the claims for fast tuning of a wide frequency range as well as a high one Frequency resolution met.

According to the invention, this object is achieved by a receiver the features specified in claim 1. Advantageous embodiments and Further developments are described in the subclaims.

The frequency of the first oscillator is digital and therefore high Frequency accuracy adjustable. The one in the gradual switchover of the first Oscillator settling time to be taken into account is in the receiver according to the invention of subordinate importance, as it is only advanced in a few rough steps and the switching time is therefore at. a tuning process over the entire Frequency range occurs only a few times, so that for this a commercially available more cost-effective Oscillator can be used.

The frequency of the second oscillator only covers a ratio frequency band narrow to the entire frequency range. Within this narrow frequency band is a high frequency resolution even with well-known, rapidly tunable oscillators possible. Since the second oscillator always runs through the same frequency band, can the use of a digitally adjustable frequency synthesis circuit is also advantageous be, the effort due to the restriction to a relatively narrow frequency band is considerably reduced.

For tuning the reception frequency over the entire frequency range Afe e the first oscillator has equidistant frequency steps, their mutual Distance Af with n frequency steps Af = Af e / n. The received KF vibrations are mixed with the vibrations of this oscillator and into an intermediate frequency band implemented. The frequency conversion can have additional fixed frequency superposition stages contain what may be responsible for the separation of unwanted sidebands from Can be an advantage. The signal converted to the first intermediate frequency passes through a bandpass filter that has a bandwidth at least as large as that Distance between two frequency levels of the first oscillator.

This ensures that every receiving frequency is tuned through of the first oscillator is once within the filter bandwidth. Favorably the bandwidth is only slightly larger than the frequency step width Af to the Avoid the transmission of interfering frequencies to the IF receiver as far as possible.

By superimposing the broadband IF signal with the oscillation a second oscillator converts the signal to a second intermediate frequency. The frequency of the second oscillator is over a frequency band, its width is equal to the distance between two frequency levels of the first oscillator, wobbled. The signal converted to the second intermediate frequency is filtered with a narrow band and can thus be clearly assigned to a specific reception frequency. There the second oscillator only has a narrow frequency band, which is also for everyone Reception frequencies remain the same, is wobbled, is with continuous tuning with an analog control signal a high frequency resolution and when using a digitally adjustable frequency synthesis circuit an even more reasonable cost given.

Tuning the receiving frequency over the entire frequency range now takes place in such a way that the first oscillator first switches to the lowest frequency level fll is set. After the transient process has subsided, the frequency becomes of the second oscillator from the lower limit f21 over the wide frequency band tuned up to the upper limit 2h. After reaching this upper limit, on the one hand, the second oscillator is reset to the output frequency f2l; otherwise the first oscillator is switched to the next frequency level at the same time. The switching time of the first oscillator is generally greater than the time to Resetting the second oscillator so that the latter remains on the lower one for a while Frequency f2l is held until after the frequency of the first oscillator has stabilized the wobbling process is repeated. The current receiving frequency is during the switchover time not defined, so that reception does not make sense during this time.

The evaluation of the signals is therefore interrupted during this time.

For storing the IF signal filtered out of the narrow band The information obtained is a memory arrangement with a large number of memory locations intended. The frequency range is correspondingly divided into a large number of narrow sub-ranges divided equally width. Each of these sub-areas is one of the storage locations assigned. The frequency resolution for further evaluation is due to the width the frequency subranges are limited. The storage of the information has opposite the advantage of immediate further processing or display without storage, that the data is written over by more recent data from the same frequency subrange are retained and can be queried several times during this time.

Since, as already mentioned, the receiving frequency during the switchover of the first oscillator cannot be defined, the information is transmitted during the sweep of the second oscillator won. The narrow-band filtered signal is used for this scanned several times during the wobbling process, and the information obtained therefrom via the signal amplitude at the current frequency (possibly after digitization) in written to the memory location assigned to this frequency. The frequency assignment can be done by direct frequency determination, but it can also, for example can be derived from the comparison with the instantaneous value of the control signal.

Frequency allocation is particularly easy when using a digitally adjustable frequency synthesis circuit.

The memory contents are used for quick and clear evaluation on a screen as a wave display, d. H. as a representation of the Signal amplitude displayed over the frequency of the entire frequency range. At digital For this purpose, the storage is still a D / A converter between the memory and the screen to be provided.

The memory contents can be repeated independently of the writing process be queried. This makes it possible to get a flicker-free picture through accordingly to generate high repetition frequency of the query process. A refresh rate of about 30 Hz is generally sufficient for this. In addition, the wave display a visual marker can be displayed. This visual mark is associated with Control devices along the frequency axis can be moved as desired, so that this means that any point in the spectrum can be marked.

About the possibility of repeated tuning of the frequency range and the associated wave display can also be provided that any Reception frequency can be entered. The first oscillator is then associated with an Control unit set so that the entered frequency is in the middle of the tuning of the second oscillator swept reception frequency band lies. The frequency input can be done using a separate keyboard as well as by setting the visual marker on the corresponding position in the wave display and pressing an associated Command button. When setting the receiver to a specific reception frequency, the switching of the first oscillator is interrupted during the second oscillator can still be swept. This results in a section from the wave display corresponding to the receiving frequency band swept over during the wobbling process.

This reception frequency band can now be viewed on the screen as a detail panorama shown from the wave display with expanded frequency scale; will. Advantageous there is a separate one for storing the values of the detail panorama Provide storage arrangement.

This allows the entire frequency range as well as additionally, For example, arranged one above the other on a screen, the detail panorama being represented. This detail panorama can be characterized as a frequency magnifier.

In order to achieve a higher frequency accuracy, the second Oscillator can be provided for recording the detail panorama, the wobble to run at a reduced speed. With the same number of storage locations of the two memory arrangements for the entire frequency range or the narrower one The frequency band is then also obtained in the representation of the detail panorama a much higher frequency resolution for the viewer on the screen. This is guaranteed when the selection characteristic is in the second intermediate frequency is adapted.

The recording of the spectrum for the entire frequency range and the Recording of the clipping panorama for the narrow frequency band can be advantageous be combined in such a way that with the visual mark that can be faded in in the wave display a frequency is set. After tuning the receive frequency through The first oscillator is set for the entire frequency range so that the The second oscillator wobbles the marked frequency in the middle of the swept Reception frequency band of the bupe comes to rest. This emr) frequency band is then as a detail panorama in addition to the wave display in the one already described Way presented. After taking the panorama, the jumps first oscillator back to the lowest frequency level f11 and a new cycle Wave display / clipping panorama done.

As with the wave display, you can also use the detail panorama a movable visual marker can be displayed. With this visual marker, a Frequency can be set relatively precisely due to the stretched frequency scale. This is made possible in an advantageous manner in an expanded version of the system commanding a listening or direction finding device on one of the spectrum selectable frequency. Such an additional receiving part can, for example to the output of the broadband filter with the interposition of a narrowband filter Filters can be connected. The first oscillator is then automatically set so that that the frequency marked on the screen corresponds to the reception frequency of the listening and / or Forms DF receiving part.

During eavesdropping or direction finding, with such an arrangement the setting of the first oscillator cannot be changed, so that no new spectrum of the entire frequency range can be recorded. The recording of the detail panorama with the marked reception frequency as the center frequency is still possible because the swept second oscillator is in a separate one Signal path is arranged. Should the monitoring of the entire frequency range be continued are also during the eavesdropping or direction finding, a separate receiver is with own RF input part required. This will then be on the marked frequency commanded. An extension of the system by several to different frequencies Commandable fixed frequency receiver is easily possible. The control of each Oscillators or receivers are expediently carried out by a central control unit.

The through the two visual marks in the wave display and in the clipping panorama Marked frequencies can nocs digitally on facilities provided for this purpose displayed or output.

The invention is illustrated below using an example with the aid of Illustrations still illustrated. FIG. 1 shows the basic structure of a receiver according to the invention, FIG. 2 the chronological sequence of the individual frequency settings.

The signals received via the antenna 1 are used in an amplifier 2, which can also be designed as an antenna distributor, reinforced and thereafter in a mixer 3 with the oscillations of the digitally adjustable first oscillator 4 superimposed. The intermediate-frequency signal filtered broadband in the filter 5 is in a further flischstufe 7 with the oscillation of the swept second oscillator 9 superimposed and converted to a second intermediate frequency ZF '. After narrower band Filtering in the filter 8, this signal is sent to the central control unit 10 for evaluation, Storage, display, etc. supplied. On the screen 11 is in the lower half the wave display extending over the entire tuned frequency range and in the upper half of the screen a detail panorama with an expanded frequency scale shown. On the one hand, the central control device wobbles the second oscillator 9 by means of a sawtooth voltage and also controls via a data bus the stepwise switching of the first oscillator 4. The broadband intermediate frequency The signal is also sent to an eavesdropping receiver via a narrow-band filter 6 fed. The needle-shaped, Visibility marks that can be shown in the display, each individually along the frequency axes be moved.

Alternatively or in addition to that after the narrow-band filter 6 arranged interception part can still a separate eavesdropper 12 may be provided, which then also via a data line from the control unit 10 is commanded.

The receiver is, for example, over a 50 MEz wide frequency range tunable. The center frequency of this range can be set on the control unit will.

The first oscillator is used to tune the receiving frequency 10 frequency steps at a distance of 5 MHz each. The IF signal at the output of the filter 5 has a bandwidth of 5.5 MHz. This broadband IF signal is with the oscillator frequency swept over the frequency range of 5 MEz mixed, the resulting second IF is narrow-band filtered and the signal amplitude in the control unit 10, for example, evaluated logarithmically and stored. The wave display continues are then made up of ten sections lined up without gaps.

For example, the number of storage locations is 1000 for each of the two storage arrangements. One storage space corresponds to the wave display thus a frequency sub-range of 50 kHz, for the detail panorama this width 5 kHz. For a rough frequency control you can still click on the screen Frequency markers are displayed on each frequency scale, for example in the distance of 5 or 0.5 MHz.

On the lower half of the screen there is a 50 CET wide frequency band written, the center frequency of this band is set by hand on the display unit. The visual marker (cursor) belonging to the lower track can be attached to any straight line point of interest in this image. On the upper half of the screen a moving 5 MEz wide "magnifying glass" appears in such a way that the center frequency of the Magnifying glass corresponds to the setting of the lower cursor, the frequency of which is also on one Is displayed digitally.

With the cursor belonging to the upper track, a frequency of interest can be set more precisely, the cursor frequency is set to shown on the associated display. Should the set signal be monitored or listened to its frequency is "commanded" into the receiver at the push of a button, i. H. the receiver adjusts itself to the frequency given by the cursor above.

The wave indicator operation is now interrupted because the receiver now serves as a listening receiver and is no longer allowed to jump. The 50 MEz ad disappears from the screen, only the 5 CET wide cutout with the commanded frequency written as center frequency.

So when equipped with a receiver it is only possible either eavesdropping when a panorama is 5 MEz wide, or the 50 MHz band is closed monitor, but not both at the same time.

When showing the chronological sequence of the individual frequency settings in FIG. 2A, 2B and 2C is the time scale for tuning the receive frequency over the entire frequency range in 10 equal intervals according to the time interval between two further switching of the first oscillator frequency and a time range 11laupe "for recording the detail panorama. Tuning across the frequency range and recording the detail panorama together make up a cycle. In the case of uninterrupted radio reconnaissance such cycles follow one another without any gaps. Swings in the first interval the first oscillator on its lowest frequency level f11 and then holds this frequency until the end of the first interval. During the settling process, in FIG. 2A is shown in dashed lines, is the frequency of the first Oscillator not defined. The dashed curve only roughly shows the frequency curve when settling.

The time during which the frequency of the first oscillator was kept stable is shown as a solid line in the frequency diagram. The second oscillator at the beginning of the first interval still oscillates at the upper limit frequency f2h des swept frequency band of width Af and is then set to the lower limit frequency f2l reset. The first oscillator remains until the end of the settling process the second oscillator is at its lower limit frequency f21. After that, the Frequency of the second oscillator from the lower band limit f21 to the upper band limit f2h continuously tuned. While the second oscillator is wobbling the reception frequency based on the lowest reception frequency fel a reception frequency band the width Af. During this time, the evaluation and storage of the received signals. When the second oscillator finishes sweeping, it begins the second interval with switching the first oscillator and resetting of the second oscillator. The receiving frequency runs through with each wobble process of the second oscillator one of 10 seamlessly contiguous frequency bands the width Af. Combined, these frequency bands result in the entire frequency range Afe After completion of the tenth interval, i.e. H. after reaching the upper limit If the reception frequency range is missing, the first oscillator jumps to the frequency 1C Commanding the first oscillator on this frequency he follows for example, by setting the cursor anywhere in the Wave display. The frequency flc is such that the in the wave display by the Cursor marked reception frequency fc in the middle of when tuning the second Oscillator swept receive frequency band lies. The tuning speed of the second oscillator is compared to the tuning speed in the example shown in the intervals 1 to 10 by a factor of 3 less, so that for inclusion of the detail panorama results in a higher frequency resolution. Accordingly is the frequency hold time of the first oscillator is also extended. The receiving frequency runs through, as shown in FIG. 2C can be seen, a frequency band of width Af with the marked frequency fc as the center frequency. After completing the recording of the detail panorama a cycle is completed and a new cycle begins with switching over the first oscillator to the lowest frequency stage f11 and resetting the second Oscillator to its output frequency f21

Claims (17)

Claims 1. Receiver for radio reconnaissance for quick tuning the received frequency over a wide frequency range, with the received RF oscillations by superimposing the oscillation of a first oscillator in the high frequency Input part can be converted to a first intermediate frequency, characterized by the following features: the frequency (f1) of the first oscillator (4) is digital adjustable and in several coarse steps (#f), which are equidistant over a frequency range are distributed over the width of the reception frequency range f, can be automatically incremented, the intermediate-frequency output signal of the high-frequency input part has a Bandwidth that is at least as large as the frequency step width of the first Local oscillator, the intermediate frequency output signal is by superimposing the oscillation of a second oscillator (9) on a second Intermediate frequency converted and narrow-band filtered, the frequency (f2) of the second The oscillator is automatically tunable over a frequency band, its Width is the same as the frequency step width of the first local oscillator, according to tuning the second oscillator automatically becomes the frequency of the first The oscillator is switched one step further and the second during this switchover Oscillator reset to its original frequency. 2. Receiver according to claim 1, characterized in that the frequency range is divided into a large number of narrow sub-areas and each sub-area Storage space is allocated to a storage arrangement. 3. Receiver according to claim 2, characterized in that the signal amplitude after conversion to the second intermediate frequency and after narrow-band filtering sampled while tuning the second oscillator and into that of the current one Reception frequency assigned memory space of the memory arrangement is written will. 4. Receiver according to claim 2 or 3, characterized in that the Brought memory contents on a screen (11) as a wave display for display will. 5. Receiver according to claim 4, characterized in that the memory contents be queried repeatedly for the wave display regardless of the writing process, where the Refresh rate is so high that on the screen a flicker-free image appears. tj. Receiver according to claim 4 or 5, characterized by an in the wave display can be faded in and operated by operating devices along the frequency axis movable visual mark. 7. Receiver according to claim 1, characterized in that any Receiving frequency can be entered and the first oscillator is set so that that the entered frequency is in the middle of when tuning the second oscillator covered receiving frequency band. 8. Receiver according to claim 6 and 7, characterized in that the Enter any desired reception frequency by setting the visual indicator to the corresponding point in the wave display. 9. Receiver according to claim 7 or 8, characterized in that a separate memory arrangement is provided for the reception frequency band and that the Reception frequency band on the screen as a detail panorama with an expanded frequency scale can be represented. 10. Receiver according to one of claims 7 to 9, characterized in that that the second oscillator can be tuned at a reduced speed. 11. Receiver according to one of claims 7 to 10, characterized in that that the recording of the clipping panorama between two recording periods for that entire frequency range takes place. 12. Receiver according to claim 9, characterized in that by a can be faded in into the panorama view and by means of appropriate operating devices along the frequency axis displaceable second visual mark a desired frequency can be selected from the frequency band shown. 13. Receiver according to one of the preceding claims, characterized in that that the intermediate-frequency output signal of the high-frequency input section also Via a narrow-band filter (6) to an intermediate-frequency listening and / or DF receiving part can be supplied, and that during the listening and / or bearing time, the frequency of the first Oscillator is not changed. 14. Receiver according to one of the preceding claims, characterized in that that an additional monitoring and / or direction finding receiver (12) with its own RF input part can be commanded to any receiving frequency. 15. Receiver according to claim 6 or 12, characterized in that the reception frequencies set by the visual marker digitally. are displayed. 16. Receiver according to one of claims 1 to 15, characterized in that that the second oscillator is repeated over the frequency band by an analog control signal is continuously tunable. 17. Receiver according to one of claims 1 to 15, characterized in that that the second oscillator is digitally adjustable in small frequency steps Frequency generator is.