WO2007014869A1

WO2007014869A1 - Radio receiving device

Info

Publication number: WO2007014869A1
Application number: PCT/EP2006/064493
Authority: WO
Inventors: Wolfgang Schaefer; Gerhard Kottschlag; Jens Passoke
Original assignee: Robert Bosch Gmbh
Priority date: 2005-08-03
Filing date: 2006-07-21
Publication date: 2007-02-08
Also published as: DE102005036446A1; EP1913750A1

Abstract

The invention relates to a radio-receiving device (1) provided with a receiving part (2) which comprises a mixer oscillator (VCO), whose oscillation frequency is coupled to the frequency and/or phase of a reference oscillator (20) and which is used for converting a radio reception signal (HF) on an intermediate frequency, and a signal processing part (3) which is placed downstream for processing the intermediate frequency signal (ZF) and comprises means (16, 16a, 16b) for determining a frequency deviation between the reference frequency (RF) of the reference oscillator (20) and a reference frequency defined according to the intermediate frequency signal (ZF) or a signal derived therefrom. In the receiving part (2), the parameters are adapted in such a way that it makes it possible to directly or indirectly control the oscillation frequency according to the determined frequency deviation (Δf).

Description

ROBERT BOSCH GMBH, 70442 Stuttgart

Radio receiver

The invention relates to a radio receiver with a receiving part, which has a mixing oscillator whose oscillation frequency is coupled to the frequency or phase of a reference oscillator and which is used to convert a radio reception signal to an intermediate frequency and a subsequent signal processing part for further processing of the intermediate frequency signal.

Such radio-receiving devices are well known, for example, as car radios. The receiving part of such radio receiving equipment has a mixer for

Converting received and possibly pre-amplified radio-frequency radio reception signals with an antenna to the intermediate frequency. For this purpose, the mixer is supplied with an oscillator signal (hereinafter also referred to as mixer drive signal), from whose oscillation frequency the reception frequency results. In some receivers, the oscillator does not oscillate at the mixer drive frequency, but rather at a t.c. significantly higher frequency. In these cases, the output of the oscillator is divided by a divider (hereinafter referred to as divider V) down to the frequency of the mixer drive signal. At the output of the mixer, an intermediate frequency filter set to at least one defined intermediate frequency can be provided. The possibly filtered intermediate frequency signal is then amplified and further processed.

The oscillator signal is typically generated with a voltage controlled oscillator (VCO) integrated into a phase locked loop (PLL - phase-locked loop). The PLL includes a programmable divider (hereafter referred to as divider N) which divides the VCO signal down to the PLL comparison frequency. This signal is fed to an input of a phase comparator to compare the divided oscillator signal with a reference frequency signal of the reference oscillator with respect to the phase position. The comparison result is used to track the VCO. Between the reference oscillator and phase comparator usually another divider is implemented (hereinafter referred to as divider R) to divide the high frequency reference signal to the PLL comparison frequency.

For processing the received intermediate frequency signal, in particular when a digital signal processing of the intermediate frequency signal takes place, a highly accurate reference frequency is required, from which the mixed signal is derived. The optimal use of Zwischenfrequenzfϊlters requires the most accurate intermediate frequency and thus a stable frequency of the reference oscillator. In digital

Broadcasting systems, such as DRM (Digital Radio Mondial) and DAB (Digital Audio Broadcast), the accuracy of the intermediate frequency for the synchronization time of subsequent digital signal processing is of great importance. The advantage of lower synchronization times arises, inter alia, in frequency jumps, by the reduced computational effort required and lower turn-on times.

Conventionally, therefore, highly accurate and therefore expensive crystals are used for the oscillators. It is also known to measure the frequency differences in the signal processing part by means of an external reference and in the signal processing part digitally, d. H. numerically to compensate. At this

The frequency offset continues until the IF stages, so that the IF signal is not centered in the pass frequency range of the hardware intermediate frequency filter. Thus, these filters can not be used optimally. Sometimes only wider (less selective) filters are used, so that even those IF signals that have a corresponding frequency offset, still in the

Passage range of the filter are. The object of the invention is therefore to provide an improved radio receiver, with the frequency deviations of the intermediate frequency signal can be reduced inexpensively and reliably.

The object is achieved with the radio receiver of the aforementioned type according to the invention that the signal processing part has means for determining a frequency deviation of the reference frequency of the reference oscillator from a defined reference frequency of the intermediate frequency signal or derived signals, and in the receiving part an adaptation of parameters for direct or indirect Setting the oscillation frequency as a function of the detected frequency deviation takes place. The determination of the frequency deviation of the reference oscillator relies i.d.R. to the evaluation of the intermediate frequency signal or signals derived therefrom, e.g. its frequency offset.

The determination of the frequency deviation in the signal processing part and the implementation of the correction at least predominantly in the upstream receiving part has the advantage that thereby the filter effect can be optimally used and the filter present at the output of the mixer of the receiving part can be designed more selective. This means that interference signals from the adjacent channels can be suppressed more strongly and a better filtering effect and thus a better reception comes about. The compensation of the frequency deviation already in the receiving part has the further advantage that larger tolerated and thus more cost-effective quartz crystals can be used for the reference oscillators of the receiving part.

The means for determining the frequency deviation in the signal processing part are preferably designed to determine an offset divider value for the PLL divider N. With the help of the offset divider values determined in the signal processing part, the PLL is corrected by one or more tuning steps. Thus, the VCO and derived therefrom Mischeransteuerfrequenzen so that the IF signal is as close as possible to the desired IF frequency. The desired IF frequency may deviate from the nominal value due to tolerances of the IF filters. - A -

It is particularly advantageous if a receive channel memory is provided for storing information about the frequency deviation detected in a broadcast channel in conjunction with the broadcast channel. Thus, the frequency deviation for a respective receiving frequency z. B. when restarting a radio receiver immediately available and it can be a

Pre-compensation can be made, resulting in a reduced synchronization time of the following signal processing. The receive channel memory may be, for example, an extension station memory, a favorite list memory area or a frequency table memory area extended by an entry for information about the frequency deviation, in particular the entry of the offset divider value, for a respective reception frequency.

However, the determination of the deviation of the reference frequency also allows a prediction of the optimum offset divider value before a frequency jump.

It is also advantageous if the radio receiver is set up to provide the stored information about the respectively determined frequency deviation for retrieval and for compensation of the reference frequency error when setting the receiver to a broadcast channel. The synchronization time of the signal processing, in particular a digital signal processing can be shortened as a whole, so that z. B. after switching on a radio receiver, the audio signal is available faster. Due to the precompensation, the frequency offset is reduced and the received signal does not have to be pushed optimally into the filter bandwidth in several cycles. Rather, from the beginning the received signal can be decoded with a minimized bit error rate.

The means for determining the frequency deviation are preferably designed to estimate a frequency deviation for a different reception frequency than the set reception frequency from at least one frequency deviation determined for a respective set reception frequency. This way a can

Compensation of a possible frequency deviation for a hitherto unexamined receiving frequency from the detected for other receiving frequencies frequency deviations done. Any inaccuracies in the estimation of the Frequency deviation then only needs to be adjusted to a lesser extent than would be the case without estimating the frequency deviation.

Furthermore, it is advantageous if the receiving part has a controllable in dependence on the detected frequency deviation and connected to the reference oscillator electronic switching network for the adjustment of the reference oscillator. With the switchable network, for example, a quartz can be pulled capacitively to correct the frequency inaccuracy.

Furthermore, it is advantageous if the signal processing part has an analog /

Digital converter for converting the analogue

Zwischenfrequenzrundfunkempfangsignals in a digital signal and for further processing of the intermediate frequency signal has. The signal processing part is then designed to determine the frequency deviation from the digital intermediate frequency signal, for example by numerical signal processing with the aid of a microprocessor which is present anyway in any case in the signal processing part. No additional hardware is required to determine the frequency deviation. It only needs the signal processor of the signal processing part to be suitably programmed.

The means for determining the frequency deviation may also, in particular in the case of analog modulation methods, be designed in such a way that they are e.g. determine the frequency deviation from the carrier or pilot tone of the intermediate frequency signal.

Furthermore, it is advantageous if a temperature sensor is provided in the radio receiver. The radio receiver is then designed to compensate for the reference frequency as a function of a measured from the temperature sensor with the temperature and a stored temperature characteristic of the reference oscillator, in particular the temperature characteristic of an oscillator quartz. By using and possibly storing the temperature information, the temperature drift of the quartz can thus also be calculated and compensated for via its temperature characteristic. The compensation can in turn via the divider setting of the PLL divider and / or the electronic influence of the quartz, for example be made with a switchable network for the capacitive pulling of the quartz.

The digital broadcasting systems DAB, DVB-T and DRM transmit in their signals time and frequency reference pilots, which calculate the exact

Allow frequency deviation up to the range of 1/10 Hz. The calculation of the respective frequency offset of the various methods are state of the art, as they are elementary necessary for synchronization.

The invention will be explained in more detail with reference to the accompanying drawings. Show it:

FIG. 1 shows a block diagram of a radio receiver with a synchronization unit designed to determine the frequency deviation and a correction of the frequency deviation in the receiver;

FIG. 2 shows a block diagram of an oscillator circuit for the radio receiver of FIG. 1.

FIG. 1 shows a block diagram of a radio receiver 1 with a

Detect part 2 and a subsequent signal processing part 3. The receiving part 2 has in a conventional manner an antenna 4 for receiving high-frequency radio reception signals HF, which are pre-amplified and filtered in a selective preliminary stage 5. At the output of the selective preliminary stage 5, a mixer 6 is arranged to the high-frequency broadcast reception signal HF by means of a

Mixer drive signal MF for an adjustable reception frequency to an intermediate frequency signal ZF with a defined intermediate frequency to implement. The mixer drive signal MF is generated in a manner known per se with an oscillator circuit 7 which has a voltage-controlled oscillator VCO (Voltage Controlled Oscillator) which is controlled by a phase-locked loop PLL. For this purpose, the frequency of a free-running voltage-controlled oscillator VCO is divided down by a programmable divider to a fixed comparison frequency. The phase difference between the frequency derived from the voltage-controlled oscillator VCO and one generated by means of a reference oscillator (usually quartz-controlled) reference frequency is determined in a phase comparator. The phase difference of the two signals is converted into a control voltage and supplied to the voltage-controlled oscillator VCO. As a result, the frequency of the voltage-controlled oscillator VCO is regulated exactly to the multiple of the PLL reference frequency set in the divider.

If necessary, an intermediate frequency filter 8 is connected at the output of the mixer 6 with an automatic gain control AGC (Automatic Gain Control).

The output of Zwischenfrequenzfϊlters 8 is connected to an analog-to-digital converter 9. The digitally converted intermediate frequency signal ZF is then filtered with a digital filter 10 and subjected to a frequency transformation 11 in a signal processing unit. Preferably, a fast Fourier transform FFT is performed. The frequency-transformed digital signal is split back into the basic signal components in a demodulator 12a. A demultiplexer

12 is used in a known manner to select the contents of the various scrambled channels or data streams of the frequency-transformed and demodulated signal and summarized in blocks, and to lead these blocks in time-division multiplex to the input of a channel decoder 13. The output of the channel decoder 13 is connected to an audio decoder 14, for example, to decode an MPEG standard coded audio signal. The output of the audio decoder 14 is connected to an audio signal reproducing unit 15 having an amplifier speaker system.

At the input and output of the signal processor for frequency transformation 11 are means

16, 16 a and 16 b provided for determining a frequency deviation of the reference and / or mixer drive frequency MF of the oscillator circuit 7 of a defined frequency to perform a synchronization of the oscillator circuit 7 of the receiving part 2. Since the frequency correction can be carried out in two steps (I Ia and I Ib), corresponding signal correction blocks I Ia, Ib are provided at the input and output of the FFT, which determine a first portion of the frequency offset calculated in block 16a or the second component calculated in block 16b Correct the proportion of the frequency offset as promptly as possible in the signal. The correction signals calculated in blocks 16a and 16b are also added in an adder 16 to a total frequency error and converted according to the currently set PLL step frequency in integer PLL correction steps for the oscillation circuit. Thus, according to the present invention, a frequency deviation Δf is detected in the oscillator circuit 7 in the signal processing part 3. An information about the detected

Frequency deviation .DELTA.f is, for example, fed back into the oscillator circuit 7 as an offset divider value for correcting the frequency deviation .DELTA.f.

The structure of the oscillator circuit 7 is shown again in detail in FIG. From the voltage-controlled oscillator VCO, a signal is generated with the aid of a divider N 17, the phase position of which is compared in the phase comparator 18 with the reference signal of a reference oscillator 20 which is divided by a divider R 19. The output signal of the phase comparator 18 is connected to a low-pass filter 21, which is also commonly referred to as a loop filter. Its output signal is used as a control voltage to the voltage controlled oscillator

VCO supplied. The output signal of the VCO is also supplied to a second divider V 22 and divided down there to the required mixer drive frequency. The chosen division ratio of the divider V 22 must be taken into account in the conversion rule for calculating the offset divider value for the divider N 17 from the determined frequency deviation Δf.

The divider N 17 is set to a divider value which is corrected with the offset divider value of the signal processing part 3. By the means for determining a frequency deviation 16 in the signal processing part 3 thus data for the frequency deviation .DELTA.f of the set radio program with a

Conversion rule converted into a number of integer tuning steps of the phase-locked oscillator circuit 7 and sent the result as an offset divider value to the oscillator circuit 7. Any remaining, non-integer component is corrected in the digital signal processing part 3. Advantageously, this can be exploited that digital radio systems according to the DAB (Digital

Audio Broadcast), DRM (Digital Radio Mondial) or DVB-T (Digital Video Broadcasting-Terrestrial) can usually detect the frequency deviation in the range of 10 Hz. The error measure for the frequency deviation can be in one integer part of tuning steps in the oscillator circuit 7 and a fraction less than or equal to half a tuning step are decomposed.

When using a fractional PLL, the divider N 17 can not be adjusted only to integer division ratios, but is adjustable in finer steps, e.g. in steps of 0.25. This feature can be used to further reduce the remaining residual frequency error of the IF signal.

But also the derivation of the reference e.g. from the pilot of an analog, frequency-modulated stereo signal is conceivable.

The result of the determination of the frequency error, in particular the offset divider value, can be stored as an attribute with the reception frequency on a station button, in a favorites list or in a frequency table in order to provide a faster one for further calls of the same frequency or previously not called frequencies

To enable synchronization of the received signal.

On the basis of the generally known quartz characteristic curve of the oscillator crystals, a temperature compensation can additionally take place on the basis of a temperature detected with a temperature sensor integrated in the radio receiver 1.

Claims

ROBERT BOSCH GMBH, 70442 StuttgartPatent claims

First broadcast receiving device (1) having a receiving part (2), which has a mixing oscillator (VCO) whose oscillation frequency is coupled to the frequency and / or phase of a reference oscillator (20) and for converting a radio reception signal (HF) to an intermediate frequency serves, and with a subsequent signal processing part (3) for further processing the intermediate frequency signal (ZF), characterized in that the signal processing part (3) means (16, 16a, 16b) for determining a frequency deviation of the reference frequency (RF) of the reference oscillator (20) a defined reference frequency from the intermediate frequency signal (ZF) or derived signals and in the receiving part (2) an adjustment of parameters in dependence on the detected frequency deviation (.DELTA.f) is carried out.

2. Broadcasting receiver (1) according to claim 1, characterized in that the means (16, 16a, 16b) for determining the frequency deviation (.DELTA.f) or an additional module for determining an offset divider value from the frequency deviation (.DELTA.f) for one with the Output of the local oscillator (VCO) coupled frequency divider of the receiving part (2) is designed to reduce the frequency deviation of the intermediate frequency signal.

3. Broadcasting receiver (1) according to claim 1 or 2, characterized by receiving channel memory for storing information about the detected at a broadcast channel frequency deviation (.DELTA.f) or offset Teilerwertes in connection with the broadcast channel.

4. Radio receiving apparatus (1) according to claim 3, characterized in that the receiving channel memory station station memory, Favoritenlistenspeicher- or frequency table storage areas.

5. Radio receiving device (1) according to any one of claims 3 or 4, characterized in that the radio receiver (1) for providing the stored information for retrieval and offset Teilerwert- pre-adjustment in setting the receiving part (2) is set up on a broadcast channel.

6. Radio receiving apparatus (1) according to any one of the preceding claims, characterized in that the means (16, 16a, 16b) for determining a frequency deviation (.DELTA.f) or an additional assembly for estimating a frequency deviation (.DELTA.fi) for a different reception frequency than the set Receiving frequency from at least one determined for each set receiving frequency frequency deviation (.DELTA.f ₂ ) are formed.

7. Radio receiving apparatus (1) according to any one of the preceding claims, characterized in that the receiving part (2) in dependence on the detected frequency deviation (.DELTA.f) controllable and with the reference oscillator (20) connected electronic switching network for adjusting the reference oscillator (20) ,

8. Broadcasting receiver (1) according to any one of the preceding claims, characterized in that the signal processing part (3) an analogue

Digital converter (9) for converting the analog intermediate frequency radio reception signal (IF, HF) into a digital signal and is designed to determine the frequency deviation (.DELTA.f) from the digital intermediate frequency signal (ZF) or derived signals therefrom.

9. Radio receiving apparatus (1) according to any one of the preceding claims, characterized in that the means for determining the frequency deviation (.DELTA.f) from the pilot tone of the intermediate frequency signal (ZF) are formed.

10. Broadcasting receiver (1) according to any one of the preceding claims, characterized by a temperature sensor, wherein the radio receiver (1) for compensating the reference frequency (RF) in response to a measured temperature with the temperature sensor and a stored temperature characteristic of the reference oscillator (20), in particular the temperature characteristic of an oscillator quartz is formed.