Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
  • H04L27/22—Demodulator circuits; Receiver circuits
  • H04L27/233—Demodulator circuits; Receiver circuits using non-coherent demodulation
  • H04L27/2332—Demodulator circuits; Receiver circuits using non-coherent demodulation using a non-coherent carrier
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying

Definitions

• the present invention relates to a communication system according to the preamble of claim 1, in which wave-modulated signals, in particular MSK signals (minimum shift keymg), are transmitted, and a corresponding receiver.
• wave-modulated signals in particular MSK signals (minimum shift keymg)
• MSK signals minimum shift keymg
• DECT systems Digital European Cordless Telephone
• radio systems which are operated in the so-called unlicensed ISM frequency bands (Industrial Scientific Medical)
• super heterodyne receivers are often used to receive and demodulate phase-modulated signals.
• low IF intermediate frequency
• zero IF zero IF
• Low-IF receivers use a relatively low intermediate frequency, which can be, for example, approximately 1 MHz for input signal frequencies of approximately 2 GHz, while the intermediate frequency for zero-IF receivers is 0 MHz.
• the phase-modulated received signal is demodulated by means of suitable, often analog signal processing (e.g. with DECT receivers).
• FIG. 4 shows a simplified block diagram of such a low or zero IF (homodyne) receiver.
• the communication information to be transmitted is transmitted via the phase of a carrier signal, the phase of the carrier signal being changed as a function of the value of the communication information to be transmitted.
• ⁇ 0 denotes the carrier frequency
• ⁇ 0 represents the zero phase
• the signal components u (t) and v (t) contain the time-dependent phase information corresponding to the communication or night bits to be transmitted. By recovering this phase information, the values of the individual communication bits can be deduced in the receiver.
• the reception signal x RF (t) is first pre-filtered by means of a bandpass filter 14 and amplified by means of a linear amplifier 23 in m low-IF or zero-IF receivers.
• the received signal thus processed is then divided into two signal paths, namely an I and a Q signal path.
• the received signal m in a mixer 15 is multiplied by the signal cos ( ⁇ 0 t) of a local oscillator 17, while in the Q signal path the received signal in a mixer 16 is multiplied by the corresponding quadrature signal -sm ( ⁇ 0 t) , which is obtained from the oscillator signal cos ( ⁇ 0 t) with the aid of a corresponding phase shift unit 18.
• a low-pass filtering with the aid of appropriate anti-aliasing filters 19 and 20 and an A / D conversion with the aid of corresponding A / D converters 21 and 22 then take place in both signal paths.
• the output signals of the two signal paths are finally grounded evaluated by a (in the present case digital) signal processing unit in order to use the signals thus obtained to produce the generally complex useful signal [u (t) + jv (t)] ⁇ 0 t) with the desired phase information, from which in turn the values of the transmitted communication or message bits d k can be derived.
• such a homodyne receiver generally has two real signal paths, each with a mixer 15 or 16, a filter 19 or 20 and an A / D converter 21 or 22 required.
• a component 18 is required to generate the quadrature signals of the local oscillator 17.
• the procedure described above is in principle suitable for all types of phase modulation. However, it does not take advantage of the properties of suitably defined modulation methods to reduce effort.
• the present invention is therefore based on the object of proposing a communication system for transmitting and receiving angle-modulated signals, in particular digital phase or frequency-modulated signals, and a corresponding receiver, the receiver being able to be implemented with significantly less effort.
• coding information or coding bits are inserted into the message bits to be transmitted, where in particular, for example, a coding bit with the fixed binary value "1" can be inserted between two successive message bits.
• the receiver is designed such that, by suitable signal processing of the angle-modulated signal based on the message and coding bits, the original message bits can be detected with only one real signal path, ie without a complex I / Q signal path. In contrast to the known homodyne receiver shown in FIG. 4, the destination of the receiver is therefore not the signal reconstruction, but the detection of the digital transmission data.
• the proposed coding and pulse shaping make phase-incoherent demodulation of the angle-modulated received signal and detection of the digital transmit data independent of a possible phase shift between the high-frequency received signal of the receiver and the local oscillator signal, which is used in the receiver for mixing down the received signal into the baseband , enables.
• the carrier phase control required in the homodyne receiver shown in FIG. 4 can thus be omitted.
• the mixer, filter and A / D converter only have to be provided once. Since no complex I / Q signal path is required, the mixer, filter and A / D converter only have to be provided once. Since no complex I / Q signal path is required, the
• Quadrature signal generation for the local oscillator signal is eliminated, and there are no matching requirements to be observed between the I / Q signal paths.
• FIG. 1 shows a simplified block diagram of a receiver according to the invention
• FIG. 2 shows a possible implementation of a digital demodulator shown in FIG. 1,
• FIG. 4 shows a simplified block diagram of a known homodyne receiver.
• the present invention is explained below by way of example using MSK-modulated (minimum shift keying) signals for the noise-free case.
• MSK-modulated minimum shift keying
• the invention is not restricted to this type of modulation, but rather can be applied generally to all types of angle modulation, in particular to all CPFSK (continuous phase frequency shift keying) modulation methods, such as those used according to the DECT or GSM mobile radio standard ,
• the phase of the carrier signal is rotated either by - ⁇ / 2 or by + ⁇ / 2 depending on the binary value d k e ⁇ - 1,1) to be transmitted.
• the high-frequency MSK signal x RF (t) transmitted by a transmitter 25 shown in FIG. 1 via a transmitting antenna 26 and received by a receiver 27 via a receiving antenna 1 generally has the form:
• ⁇ 0 denotes the carrier frequency
• ⁇ 0 the zero phase
• ⁇ the phase offset between the RF received signal and the signal from the local oscillator (not shown in FIG. 1) of the receiver 27
• ⁇ (t) which are the result of the binary information to be transmitted adjusting phase change of the carrier signal.
• the transmitter 25 shown in Fig. 1 is designed such that not only the actual message bits d k are transmitted phase-modulated, but also coding bits, which guide from the transmitter 25 at regular intervals before passing ⁇ be inserted, with the phase modulation in the yogaenbitsequenz.
• ⁇ k ⁇ / 2 - (f + / t _, + ... + /, +
• a digital demodulator 6 shown in FIG. 1 has the task of determining the transmitted message bits d k by evaluating the individual sample values y.
• a possible implementation of the digital demodulator 6 is shown in FIG. 2 in the form of a simplified block diagram.
• the digital demodulator 6 comprises only three memory or delay elements 7-9, which form a shift register of the length 3, two multipliers 10 and 11 and an adder 12 and a sign. Detector 13.
• the multipliers 10 and 11 By interconnecting the multipliers 10 and 11 with the individual memory stages 7-9 of the shift register it is achieved that one of these two multipliers always multiplies two samples of the baseband signal sequence y k , which go back to two successive message bits, while the other multiplier two Multiplied samples of the baseband signal sequence y k , which are based on two successive coding bits.
• the multiplication results are added by the adder 12, so that the sign detector 13 can simply determine and output the values of the transmitted message bits d by evaluating the sign of the addition result.
• the aforementioned coding not only implements pulse shaping, but in particular enables phase-incoherent demodulation and detection of the message bits d independently of a possible phase offset ⁇ between the high-frequency received signal x RF (t) and the local oscillator signal, so that none Carrier phase control is required.
• 3 shows the bit error rate (BER) that can be achieved using the present invention as a function of the bit signal-to-noise ratio E b / N 0 .
• the corresponding BER characteristics of other known demodulation methods are also shown for comparison. It can be seen from the illustration in FIG.
• a higher-quality Hadamard coding can be used, in which the coding bits are inserted into the message bit sequence to be transmitted at greater intervals.
• the digital demodulator 6 shown in FIG. 2 must of course be adapted accordingly with regard to the length of the shift register and the connection of the two multipliers 10, 11 to the shift register.

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• 1999
  • 1999-09-08 DE DE19942944A patent/DE19942944A1/de not_active Withdrawn
• 2000
  • 2000-09-06 CN CNB008124698A patent/CN100399774C/zh not_active Expired - Fee Related
  • 2000-09-06 JP JP2001522736A patent/JP3601713B2/ja not_active Expired - Lifetime
  • 2000-09-06 EP EP00956517A patent/EP1210806A1/de not_active Withdrawn
  • 2000-09-06 WO PCT/EP2000/008701 patent/WO2001019046A1/de not_active Application Discontinuation
• 2002
  • 2002-03-08 US US10/094,559 patent/US6549588B2/en not_active Expired - Lifetime

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