Circuit for a demodulator for a radio data signal in a radio receiver
First Claim
1. Circuit for a demodulator for a radio data signal in a radio receiver, where transmission of the radio data signal is carried out through phase shifting of at least one suppressed auxiliary signal (pc1, ps1) within a multiplex signal (MPX), comprisingfilter means (15) for band-pass filtering the multiplex signal, said filtering defining a base band;
- means (18,
19) for obtaining, from the radio receiver, at a scanning clock rate produced by the radio receiver, reference carriers having two phase positions shifted 90°
with respect to each other;
mixing means (16,
17) for mixing, into the base band, the filtered multiplex signal (MPX) in digital form and said reference carriers having said two phase positions shifted 90°
with respect to each other, to thereby produce a first mix signal (wc) and a second mix signal (ws);
generating means (37) for producing a first and a second auxiliary signal (pc1, ps1) having, respectively, a cosine and a sine wave form;
first multiplying means (33,
34) for multiplying the first mix signal (wc) by said first auxiliary signal (pc1) and for multiplying the second mix signal (ws) by said second auxiliary signal (ps1) and deriving first and second multiplied signals;
adding means (38) coupled to receive the first and second multiplied signals and adding the first and second multiplied signals, and producing a first output signal (A1);
second multiplying means (35,
36) for multiplying the first mix signal (wc) by the second auxiliary signal (ps1) and for multiplying the second mix signal (ws) by the first auxiliary signal (pc1) and deriving third and fourth multiplied signals;
subtracting means (39) coupled to receive said third and fourth multiplied signals and forming the difference between the third and fourth multiplied signals, and thereby producing a second output signal (A2); and
means for controlling the phase position of the first and second auxiliary signals (pc1, ps1) to cause the first output signal (A1) to correspond to the radio data signal (RDS) shifted down into the base band;
wherein said means for controlling said phase position comprisesmultiplying means (48) for multiplying the first output signal (A1) by the second output signal (A2) to obtain a third output signal (A3);
a plurality of low-pass filters (53, 54,
55) connected to have the first (A1) and the second (A2) and the third (A3) output signal each passed through a respective low-pass filter (53, 54,
55) and deriving first (H1), second (H2) and third filtered signals;
third multiplying means (56) for multiplying the first (H1) and the second (H2) low-pass filtered signals (H1, H2) by each other and deriving a multiplied signal (H4);
subtracting means (58) for subtracting the multiplied signal (H4) from the low-pass filtered third signal (H3); and
a threshold circuit (59) receiving the result (H5) of the subtraction and generating a control voltage for said auxiliary signal generating means (37), producing said auxiliary signals (pc1, ps1).
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Accused Products
Abstract
In a circuit for a demodulator of a radio data signal in a radio receiver, the multiplex signal in digital form is mixed into the baseband, in two phase positions shifted 90° with respect to each other, after band-pass filtering, together with a reference carrier generated at a sampling clock rate produced in the radio receiver, thus producing a first and a second mix signal. A first and a second auxiliary signal with, respectively, a sine waveform and a cosine waveform are produced. The first mix signal is multiplied by the first auxiliary signal, and the second mix signal by the second auxiliary signal. The results of these multiplications are added together, producing a first output signal. The first mix signal is multiplied by the second auxiliary signal, and the second mix signal by the first auxiliary signal, and the results subtracted from each other, thus producing a second output signal. The phase position of the auxiliary signals is controlled in such a manner that the first output signal corresponds to the radio data signal (RDS) shifted down into the baseband.
19 Citations
15 Claims
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1. Circuit for a demodulator for a radio data signal in a radio receiver, where transmission of the radio data signal is carried out through phase shifting of at least one suppressed auxiliary signal (pc1, ps1) within a multiplex signal (MPX), comprising
filter means (15) for band-pass filtering the multiplex signal, said filtering defining a base band; -
means (18,
19) for obtaining, from the radio receiver, at a scanning clock rate produced by the radio receiver, reference carriers having two phase positions shifted 90°
with respect to each other;mixing means (16,
17) for mixing, into the base band, the filtered multiplex signal (MPX) in digital form and said reference carriers having said two phase positions shifted 90°
with respect to each other, to thereby produce a first mix signal (wc) and a second mix signal (ws);generating means (37) for producing a first and a second auxiliary signal (pc1, ps1) having, respectively, a cosine and a sine wave form; first multiplying means (33,
34) for multiplying the first mix signal (wc) by said first auxiliary signal (pc1) and for multiplying the second mix signal (ws) by said second auxiliary signal (ps1) and deriving first and second multiplied signals;adding means (38) coupled to receive the first and second multiplied signals and adding the first and second multiplied signals, and producing a first output signal (A1); second multiplying means (35,
36) for multiplying the first mix signal (wc) by the second auxiliary signal (ps1) and for multiplying the second mix signal (ws) by the first auxiliary signal (pc1) and deriving third and fourth multiplied signals;subtracting means (39) coupled to receive said third and fourth multiplied signals and forming the difference between the third and fourth multiplied signals, and thereby producing a second output signal (A2); and means for controlling the phase position of the first and second auxiliary signals (pc1, ps1) to cause the first output signal (A1) to correspond to the radio data signal (RDS) shifted down into the base band; wherein said means for controlling said phase position comprises multiplying means (48) for multiplying the first output signal (A1) by the second output signal (A2) to obtain a third output signal (A3); a plurality of low-pass filters (53, 54,
55) connected to have the first (A1) and the second (A2) and the third (A3) output signal each passed through a respective low-pass filter (53, 54,
55) and deriving first (H1), second (H2) and third filtered signals;third multiplying means (56) for multiplying the first (H1) and the second (H2) low-pass filtered signals (H1, H2) by each other and deriving a multiplied signal (H4); subtracting means (58) for subtracting the multiplied signal (H4) from the low-pass filtered third signal (H3); and a threshold circuit (59) receiving the result (H5) of the subtraction and generating a control voltage for said auxiliary signal generating means (37), producing said auxiliary signals (pc1, ps1). - View Dependent Claims (2, 3, 4)
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5. Circuit for a demodulator for a radio data signal in a radio receiver, where transmission of the radio data signal is carried out through phase shifting of at least one suppressed auxiliary signal (pc1, ps1) within a multiplex signal (MPX), comprising
filter means (15) for band-pass filtering the multiplex signal, said filtering defining a base band; -
means (18,
19) for obtaining, from the radio receiver, at a scanning clock rate produced by the radio receiver, reference carriers having two phase positions shifted 90°
with respect to each other;mixing means (16,
17) for mixing, into the base band, the filtered multiplex signal (MPX) in digital form and said reference carrier having said two phase positions shifted 90°
with respect to each other, to thereby produce a first mix signal (wc) and a second mix signal (ws);generating means (37) for producing a first and a second periodic auxiliary signal (pc1, ps1); first multiplying means (33,
34) for multiplying the first mix signal (wc) by said first auxiliary signal (pc1) and for multiplying the second mix signal (ws) by said second auxiliary signal (ps1) and deriving first and second multiplied signals;adding means (38) coupled to receive the first and second multiplied signals and adding the first and second multiplied signals, and producing a first output signal (A1); second multiplying means (35,
36) for multiplying the first mix signal (wc) by the second auxiliary signal (ps1) and for multiplying the second mix signal (ws) by the first auxiliary signal (pc1) and deriving third and fourth multiplied signals;subtracting means (39) coupled to receive said third and fourth multiplied signals and forming the difference between the third and fourth multiplied signals, and thereby producing a second output signal (A2); and means (53, 54, 55, 56, 57,
58) for controlling the phase position of the first and second auxiliary signals (pc1, ps1) to cause the first output signal (A1) to correspond to the radio data signal (RDS) shifted down into the base band;said phase position control means comprising means for providing a control signal to said means (37) for generating at least one of said auxiliary signals (pc1, ps1), for controlling said at least one auxiliary signal in dependence on the provided control signal, wherein said control signal can assume two levels; and wherein said generating means (37) comprises a register (62), said register being incremented or decremented by clock signals having a frequency which is significantly higher than the frequency of the respective periodic signal to be generated, said register being, respectively, incremented or decremented in dependence on the level of the control signal; and means (65) for calculating a function value from the respective content of the register (62) and generating said periodic auxiliary signals (pc1, ps1), wherein the value range which the content of the register (62) can assume corresponds to a half-period of the respective auxiliary signal (pc1, ps1) to be generated; and wherein, upon an overflow or underflow of the register (62), the sign of the calculated function value is changed. - View Dependent Claims (6, 7, 8, 9)
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10. A method to demodulate a radio signal in a radio receiver, where transmission of the radio signal is carried out through phase shifting and at least one suppressed auxiliary signal within a multiplex (MPX) signal, comprising
band-pass filtering the multiplex (MPX) signal, said filtering defining a base band; -
obtaining, from the radio receiver, at a sampling clock rate produced by the radio receiver, a reference carrier having two phase positions shifted 90°
with respect to each other;mixing, into the base band, the filtered multiplex (MPX) signal, in digital form, with said reference carrier having said two 90°
phase-shifted positions, to thereby produce a first mix signal (wc) and a second mix signal (ws);generating a first periodic auxiliary signal (pc1) and a second periodic auxiliary signal (ps1); multiplying, in a first multiplication step, the first mix signal (wc) by the first auxiliary signal (pc1) and multiplying the second mix signal (ws) by the second auxiliary signal (ps1); adding the results of the multiplications of said first multiplication step and thereby producing a first output signal (A1); multiplying, in a second multiplication step, the first mix signal (wc) by the second auxiliary signal (ps1) and the second mix signal (ws) by the first auxiliary signal (pc1); forming the difference between the results of the multiplications of the first and second multiplication steps, and thereby producing a second output signal (A2); and controlling the phase position of said auxiliary signals (pc1, ps1) to cause correspondence of the first output signal (A1) to the radio data signal (RDS) shifted down into the base band; and wherein the reference carrier is present as a 0, 1, 0, -1 . . . sequence of numbers for a sine phase position and as a 1, 0, -1, 0 . . . sequence of numbers for a cosine phase position. - View Dependent Claims (11, 12)
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13. A method to demodulate a radio signal in a radio receiver, where transmission of the radio signal is carried out through phase shifting and at least one suppressed auxiliary signal within a multiplex (MPX) signal, comprising
band-pass filtering the multiplex (MPX) signal, said filtering defining a base band; -
obtaining, from the radio receiver, at a sampling clock rate produced by the radio receiver, a reference carrier having two phase positions shifted 90°
with respect to each other;mixing, into the base band, the filtered multiplex (MPX) signal, in digital form, with said reference carrier having said two 90°
phase-shifted positions, to thereby produce a first mix signal (wc) and a second mix signal (ws);generating a first periodic auxiliary signal (pc1) and a second periodic auxiliary signal (ps1); multiplying, in a first multiplication step, the first mix signal (wc) by the first auxiliary signal (pc1) and to form a first product, and multiplying the second mix signal (ws) by the second auxiliary signal (ps1) to form a second product; adding the first product and the second product and thereby producing a first output signal (A1); multiplying, in a second multiplication step, the first mix signal (wc) by the second auxiliary signal (ps1) to form a third product, and the second mix signal (ws) by the first auxiliary signal (pc1) to form a fourth product; forming the difference between the third and fourth product, and thereby producing a second output signal (A2); and controlling the phase position of said auxiliary signals (pc1, ps1) to cause correspondence of the first output signal (A1) to the radio data signal (RDS) shifted down into the base band; and wherein the step of controlling the phase position of the first and second auxiliary signals (ps1, pc1) comprises providing a control signal (US) which can assume two levels; incrementing or decrementing the content of a register (62) by clock signals which have a frequency which is significantly higher than the frequency of the respective auxiliary signal to be generated; and calculating a function value from the respective content of the register (62), wherein the value range, which the content of the register can assume, corresponds to a half-period of the signal to be generated, and wherein the sign of the calculated function value changes at each overflow and underflow of the register (62), and controls said first and second auxiliary signals. - View Dependent Claims (14, 15)
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Specification