DE19830991A1 - Transmitter search run method for radio receivers esp. car radios - Google Patents

Abstract

A method of detecting a receivable transmitter during a transmitter search run in a radio receiver, in which a frequency (intermediate frequency) (fZF) lying at a fixed spacing above or below the required receiving frequency (fg) is searched for, this frequency being generated by frequency subtraction of variable frequency (fvco) and the receiving frequency (fg). The presence of the intermediate frequency (IF) (fZF) is determined such that a count-time interval, the so-called 'gating' time (tTOR) is determined from the self-adjusting intermediate frequency (fZF) during which a reference frequency (fREF) is counted and compared with a threshold value after the 'gating' time has elapsed. With agreement of the counted value (Wref) and the threshold value, the existence of a transmitter is inferred and the receiving frequency of the receivable transmitter is stored.

Description

The present invention relates generally to radio receivers, such as radio or television receivers using a station search are equipped, and in particular be it meets a method and a device with which Station search can be determined whether a station on the be receiving frequency can be received or not.

During a station search, the reception area of a radio receiver is scanned, and if a station worthy of reception is found, the search is stopped. For this purpose, the entire frequency band that can be received by the radio receiver in question is run through. This usually does not happen continuously but in certain frequency steps. The step size depends on the frequency band to be received. In FM radio, i.e. in the FM band with a reception frequency of f _E = 87.5 MHz to 108 MHz, the step size is 100 kHz, since the frequencies are assigned to the transmitter stations in a 100 kHz frequency grid. Other frequencies and step sizes are used accordingly with AM broadcasting.

In radio reception technology, in particular radio reception technology, intermediate frequency reception technology is usually used nowadays. For this purpose, the receiver has a local oscillator in the form of a voltage-controlled oscillator ( _VCO ), which generates an oscillator frequency (f _VCO ) that is below or above the frequency to be received by a certain constant frequency range, the so-called intermediate frequency (f _IF ) lies. In FM radio this intermediate frequency f _{ZE is} typically 10.7 MHz and in AM radio f _IF = 450 kHz. In the case of the FM radio band given here as an example, assuming that the oscillator frequency (f _VCO ) is above the reception frequency, the frequency f _{VCO of} the VCO would thus vary between 98.2 MHz and 118.7 MHz. A frequency f _E that can be received with this system is exactly when the difference between the oscillator frequency and the receiving frequency in frequency modulation results in the intermediate frequency of 10.700 MHz (f _VCO - f _E = 10.700 MHz). In the case of amplitude modulation, this difference must result in exactly the intermediate frequency.

If possible, all receivable stations should be used when searching for stations found and the search then either ge at these points stops or the found transmitter frequencies for a later one Evaluation or setting can be saved so that ei at a later point in time this determined transmission station directly can be adjusted.

Various criteria can be evaluated for a search stop, for example the field strength or the zero crossing of the S curve of the frequency demodulator. Another possibility is the search stop by means of intermediate frequency counting, as described for example in DE 42 10 961 A1. For this purpose, the intermediate frequency f _IF formed when a transmitter is received is measured. This measurement is carried out digitally by counting the oscillations of the intermediate frequency over a certain period of time, the so-called gate time t _TOR . For this purpose, a counter is set to an expected value and then counted down during the gate time, or an upward payment is made from zero. The counter reading must now be evaluated to determine whether it represents the desired intermediate frequency with a high probability or whether it is the reception of an adjacent channel. For this, a window must be specified who the counting result may be within, the so-called counting validity range.

Through the frequency modulation itself, as well as through interference of reception, such as noise or modulation  malfunctions, such as those installed in vehicles in particular If radio receivers occur, interference can easily occur Receive frequency and thus deviations in the intermediate frequency surrender. A fairly statistical count To get the result of the intermediate frequency count, the Time span during which the intermediate frequency periods are counted be made long enough. The frequency deviation This results in averages. Every extension of the count time improved by the averaging frequency varia the results statistically and increases accuracy activity.

However, an extension of the counting time has the disadvantage that the time required for the channel search increases. This is especially in receivers that use the so-called RDS (Radio Da ta system) use system, not acceptable. With these RDS reception systems will deteriorate in reception conditions of a transmitter on alternative frequencies on de the same station can also be received, vice versa switches. So the change to an alternative frequency remains unnoticed for the listener, he must as quickly as possible means to be accomplished in less than a millisecond. This means that the station search must do this in a very short time determine alternative frequencies with great certainty.

In order to shorten the station search time, de for example in EP 0 297 624 A a method and egg ne proposed device in which the intermediate frequency first counted during a short time window and with a limit that has a relatively wide intermediate frequency range allows, is compared. If within that time window the presence of the intermediate frequency and thus that Presence of a receivable transmitter is detected, so takes place a second count of the intermediate frequency over a longer one Time window, the count value here with a limit value which is compared within the selected time window must lie.  

This method and this device result in a loading acceleration of the station search, but the station search remains relatively slow and the frequency determination is not sufficiently precise.

The object of the present invention is therefore a method ren and a device for a station search stop Radio receivers indicate the intermediate frequency reception use technology, the frequency determination quickly and done very accurately.

This object is achieved by the method according to the invention Claim 1 and the device according to the invention according to claim 6 solved. Advantageous further developments of the method and Device are specified in the respective subclaims.

In the known methods of intermediate frequency counting, the counting time, also called gate time, is usually derived from the reference frequency f _REF generated by an internal oscillator. In contrast, in the method and the device according to the invention, the intermediate frequency f _{IF is used} to generate the gate time. The higher lying reference frequency f _REF is then counted. This means, for example, that the frequency is approximately six times higher in the FM operating mode (f _IF = 10.7 MHz, f _REF = 61.5 MHz) and the frequency is approximately 136 times higher in the AM operating mode (f _IF = 450 kHz) , f _REF = 61.5 MHz) counts as in the methods and devices of the prior art. This enables statistically very precise counting results to be achieved with very short gate times. These counter results are available immediately after only one goal time. So counting over multiple gate times is not necessary. This enables a very fast and precise station search.

The invention is based on the schematic Block diagram of the drawing figure 1 explained in more detail be tert.  

Fig. 1 shows schematically the device according to the invention. The device comprises four blocks, the controller, the reference frequency counter, the gate time counter and the evaluation block. In the controller, the reference frequency f _{Ref generated} by a quartz oscillator present in the receiving circuit, not shown here, the desired gate time t _TOR , the count valid range W _G , a signal S _{AM / FM} indicating whether the receiver is in the AM -Mode or the FM mode should work, and an activation signal S _EN , with which the circuit can be activated or deactivated, entered as control signals. The control unit is followed by the counters, the reference frequency counter and the gate time counter.

The goal time counter is used to determine the desired goal time during which the reference frequency is to be counted. The controller loads the gate time value VALUE _TOR into the gate time counter, if necessary by converting the entered value for the desired gate time t _TOR . This is in from dependence on an additional value _WORTH, who is also entered in the Torzeitzählerblock and the exact frequency of the intermediate frequency describes what is particularly important in the AM mode, determines a preload for the gate time counter VALUE _BEFORE. This value VALUE _BEFORE represents the initial value for the gate time counter. In the exemplary embodiment shown here, the gate time counter is a down counter that counts down clocked from the initial value. The intermediate frequency f _ZFAM or f _ZFFM (here, for example, in the value range between 10.6 and 10.79 MHz) can be used as the clock and is entered in the gate time counter. When the gate time counter has expired, ie has reached its value zero, it generates a signal S _AB which is returned to the control.

The reference frequency counter is used to count the reference frequency during the gate time t _TOR . To do this, the controller receives a reference expected value VALUE _REF as the initial value. This reference expected value depends on the receiving intermediate frequency f _ZAM or f _ZFFM , the gate time t _TOR and the expected intermediate frequency f _ZF . The reference frequency counter is in turn a down counter which, after receiving a start signal S _BEN from the controller, starts counting down. This start signal starts the gate time counter at the same time. The reference _{frequency counter is} clocked with the reference _frequency f _REF . The counter stops when it has received the sequence signal S _AB from the gate time counter via the control. The then pending value of the reference frequency counter W _REF is given to the evaluation block. The counters are then reloaded with their start values.

It is determined in the evaluation block whether the value of the reference _{frequency counter} W _REF which is present after the count lies within the valid range of the count value W _G. For this purpose, the value W _G for the validity range is supplied to the evaluation block via the controller. The result of the evaluation is shown at two outputs A and B of the evaluation block. If the signal at output B is positive, the value of the reference frequency counter W _REF lies within the range of validity values W _G. The associated reception frequency can be saved as the transmitter frequency and the station search can be ended if necessary. However, if the signal at output B is negative, the value of the reference frequency counter W _REF lies outside the valid range of the count value W _G. The associated reception frequency is not saved. In this case, the second output A of the evaluation block also shows whether the result is above or below the preset value. The result is displayed immediately at outputs A and B after each elapsed time and is there until the next gate time has elapsed.

In FM and AM mode, the circuit works in the same way in principle. The operating mode is set via the signal S _{AM / FM} , with certain presettings being changed in the individual blocks, these presettings particularly affecting the precharge values of the counters.

Overall, the invention provides a method and a pre direction with the help of the presence of a set ten transmitter can be determined quickly, which makes overall a fast station search can be carried out, whereby the received stations may be saved can. The circuit arrangement according to the invention can by few signals in a simple and clear manner per be programmed, the control signals advantageously can be entered via a bus structure. Furthermore the result of the measurement is displayed with two signals, which in turn can be easily processed.  

Reference list

f _REF

Reference frequency
f _VCO

Oscillator frequency
f _ZF

Intermediate frequency
f _E

Reception frequency
f _ZFFM

Intermediate input frequency in FM mode
f _ZFAM

Intermediate input frequency in AM mode
t _GATE

Goal time
W _G

Count validity range
S _{AM / FM}

Signal for setting the AM or FM operating mode
S _AEN

Activation signal for station search
S _AB

Signal that the gate time counter has expired
S _BEN

Start signal for reference frequency counter and gate time counter
W _REF

Value of the reference frequency counter after completion of the count
VALUE _REF

Reference frequency expected value
VALUE _GOAL

Goal time value
_BEFORE

Preload value
A Output on which a signal indicates whether the reference frequency count is above or below the count valid range
B Output at which a signal indicates whether the reference frequency count is within the count valid range or not

Claims (8)

1. A method for determining receivable transmitters during a station search in a radio receiver using the intermediate frequency reception technology, the radio receiver looking for a frequency (intermediate frequency f _IF ) lying at a fixed distance above or below the desired reception frequency (f _E ) , which is generated by frequency subtraction of a variable frequency (f _VCO ) and the receiving frequency (f _E ), characterized in that the presence of the intermediate frequency (f _IF ) is determined by a time interval from the intermediate frequency (f _IF ) which arises , the so-called gate time (t _TOR ), is generated during which a reference frequency (f _REF ) is counted and compared after the elapse of the gate time with a limit value, whereby if the count value (W _REF ) and the limit value match the existence of a Transmitter is closed and the reception frequency of this receivable transmitter is saved. 2. The method of claim 1, wherein the limit is a gül scope and a match of count and limit value is present if the count value is within the the limit of validity. 3. The method of claim 2, wherein the scope for the FM radio reception range the specifiable values ± 100 kHz, ± 50 kHz, ± 25 kHz, ± 12.5 kHz or ± 6.25 kHz and for the AM radio reception range the specifiable values ± 4, ± 2, ± 1, ± 0.5 or ± 0.25 kHz around the expected reception frequency quenz around. 4. The method according to any one of the preceding claims, characterized in that if the counter value and the limit value do not match, ei ne is displayed whether the count value and thus the measured  frequency above or below the preselected value located. 5. The method according to any one of the preceding claims, characterized in that the intermediate frequency is variable. 6. Device for determining receivable transmitter during egg seeker search in a radio receiver that uses the intermediate frequency reception technology, whereby in the radio receiver egg ne at a fixed distance, the so-called intermediate frequency, oscillator frequency (f _VCO ) lying above or below the reception frequency is generated that under the assumption me a constant intermediate frequency (f _IF ) while changing the oscillator frequency (f _VCO ) the entire frequency range of the radio receiver is scanned, from the intermediate frequency (f _IF ) generated in the presence of a receivable transmitter a time interval, the so-called gate time (t _TOR ) is generated during which a reference frequency (f _REF ) is counted and compared with a limit value, the frequency of the receivable transmitter being determined from the setting of the oscillator frequency (f _VCO ) if the count value lies within a valid range of the count value surrounding the limit value and saved w ird, characterized in that the device comprises a controller, a reference frequency counter, a gate time counter and an evaluation block,
inputs for the input of the reference frequency (f _REF ), the desired gate time (t _TOR ), the count valid range (W _G ), an operating range signal (S _{AM / FM} ), and an activation signal S _{AEN are} provided in the control,
wherein the controller connection lines having the Torzeitzäh ler with which the gate time entered (t _TOR), a calculated therefrom Torzeitwert VALUE _TOR and a start signal (S _BEN) for starting the Torzeitzählers be forwarded to the gate time, and run signal to the the gate time a Ab (S _AB), which indicates that the gate time is abge run, is returned to the controller, wherein the gate time further comprises an input to which the intermediate frequency (f _ZfAM or f _ZFFM) and an additional value value _to the exact frequency describes the intermediate frequency that can be given
wherein the controller has connecting lines to the reference frequency counter with which the reference frequency (f _REF ), a reference frequency _expected value (VALUE _REF ), a start signal (S _BEN ) for starting the reference frequency counter, and a stop signal (S _AB ) for stopping the reference frequency counter become,
wherein the evaluation block has a connection line to the reference frequency counter with which the count value (W _REF ) is entered after the counting has ended, and a connection line to the control via which the count value valid range (W _G ) is entered, and
wherein the evaluation block has an output (B) at which a signal indicates whether the count value (W _REF ) of the reference frequency counter is within or outside the valid range value (W _G ), and an output (A) which indicates whether the count value (W _REF ) is above or below the count value valid range (W _G ). 7. The device according to claim 6, characterized in that the control is designed so that it the reference frequency expectation value (VALUE _REF ) from the reception frequency (f _AM , f _FM ), the gate time (t _TOR ) and the intermediate frequency (f _IF ) calculate net. 8. The device according to claim 6 or 7, characterized in that it is the reference frequency counter and the gate time counter Down counter.