Source: https://patents.google.com/patent/US5963590?oq=6275268
Timestamp: 2018-06-25 13:05:18
Document Index: 289249246

Matched Legal Cases: ['art 11', 'art 12', 'art 13', 'art 14', 'art 15', 'art 18', 'art 14', 'art 13', 'art 18', 'art 13', 'art 13', 'art 11', 'art 12', 'art 13', 'art 14', 'art 15', 'art 14', 'art 18', 'art 14', 'art 18', 'art 13', 'art 13', 'art 13', 'art 13', 'art 20', 'art 22', 'art 22', 'art 22', 'art 22', 'art 22']

US5963590A - Method for receiving digital radio signals and a digital radio signals receiver - Google Patents
Method for receiving digital radio signals and a digital radio signals receiver Download PDF
US5963590A
US5963590A US08345665 US34566594A US5963590A US 5963590 A US5963590 A US 5963590A US 08345665 US08345665 US 08345665 US 34566594 A US34566594 A US 34566594A US 5963590 A US5963590 A US 5963590A
US08345665
The present invention relates to a digital radio communication system and in particular, to a method for receiving digital radio signals and a digital radio signals receiver which can minimize power consumption and maintain good voice quality. This invention is useful for digital mobile radiotelephones, digital cellular radiotelephones, digital cordless telephones, Personal HandyPhone system and the like.
Digital radio signal receiver 300 comprises radio frequency (RF) part 11 which amplifies radio frequency signals received by an antenna and converts them to intermediate frequency signals using predetermined frequency signals from a local oscillator, intermediate frequency (IF) part 12 which amplifies the intermediate frequency signals, differential detector part 13 was designed for demodulation of differential quadrilateral phase shift keying (DQPSK), parallel-to-serial (P/S) converter part 14 which converts parallel signals to a serial signal, framing part and voice decoder part 15 which outputs error information and extracts voice data from the serial signal, speaker 16 which produces a voice based on the voice data, microprocessor unit (MPU) 17 which performs a retransmission request based on the error information, bit timing recovery (BTR) part 18 which supplies regenerated synchronous clock signal to P/S part 14, and clock generator 19 which produces a sampling clock 32f to differential detector part 13 and synchronous clock to the BTR part 18.
However, when the sampling rate is maintained at the high frequency, a power consumption in differential detector part 13 increases and arises a problem arises that batteries contained within digital mobile radiotelephones, digital cellular radiotelephones, digital cordless telephones and the like are consumed faster. On the other hand, if the sampling rate frequency is maintained low, power consumption in the differential detector part 13 decreases. However, the voice quality becomes worse, because a stability against a fading, multipath and similar effects becomes low.
The differential detector for demodulation of DQPSK signals, which are used in a digital radio signal receiver, employs plural shift registers which are adapted to change a number of bits of each shift register. A framing portion and, voice detector generates error information and extracts voice data from the serial signal, and converts I and Q parallel output signals of the differential detector to serial signals.
An error ratio monitor detects an error information regarding digital demodulation and calculates a bit error ratio E on the basis of the error information of the framing portion and voice detector. A sampling rate changing module changes a sampling rate for digital demodulation based on a signal from the error ratio monitor. The sampling rate is shifted to a higher frequency than a present frequency when the error ratio exceeds a specified upper limit, for example a bit error ratio of 10-2, and a lower frequency when the error ratio falls below a specified lower limit, for example a bit error ratio of 10-3. A sampling clock selector supplies a selected preferable sampling clock signal which is, determined by the sampling rate changing module to, the differential detector. The sampling clock signal has a frequency of N (N is an integer) times higher than a symbol rate frequency.
In the configuration described above, the error ratio may be for example, a frame error ratio or similar in the framing portion and voice detector. Additionally the specified upper limit is generally greater than the specified lower limit, however, the specified upper limit may be equal to the specified lower limit.
The present invention is applied to digital modulation systems such as π/4-shift differential quadrilateral phase shift keying (π/4 DQPSK), differential quadrilateral phase shift keying (DQPSK), quadrilateral phase shift keying (QPSK), phase shift keying (PSK), quadrilateral amplitude modulation (QAM), gaussian minimum shift keying (GMSK), and minimum shift keying (MSK).
In the digital radio signal receiver of the invention, when the error ratio exceeds the specified upper limit, the sampling rate for digital demodulation is changed to higher frequency than a sampling frequency which is actually used. As a result, the stability against fading, multipath and similar effects becomes higher and the error ratio is decreased. When the error ratio falls below the specified lower limit, the sampling rate for digital demodulation is changed to a lower frequency. As a result, stability against fading, multipath and similar effects becomes lower and the error ratio is increased. Therefore, the error ratio is kept between the specified upper and lower limits, and, the power consumption power is minimized.
FIG. 1 is a block diagram which shows a main parts of the digital radio signal receiver of the invention.
Digital radio signal receiver 100 comprises RF part 11 which amplifies radio frequency signals received by an antenna and converts them to intermediate frequency signals by using predetermined frequency signals from a local oscillator, IF part 12 which amplifies the intermediate frequency signals, differential detector part 13 for DQPSK demodulation P/S part 14 which converts parallel signals to a serial signal, framing part and voice decoder part 15 which generates error information and extracts voice data from the serial signal produced by P/S part 14, speaker 16 which produces a voice based on the voice data, MPU 17 which carries out a retransmission request based on the error information, BTR part 18 which supplies a regenerated synchronous clock signal to P/S part 14, and clock generator 19 which supplies a synchronous clock to BTR part 18.
Differential detector part 13 has shift registers as does the differential detector part 13 in FIG. 1 and outputs a I signal and Q signal. A number carried by bits of each shift register of differential detector part 13 are changeable. Differential detector part 13 is provided with a sampling clock selected from clock signals 32f, 16f, 8f and 4f by sampling clock selector part 20.
In step S3, sampling rate changing part 22 checks whether bit error ratio E is located between the upper limit i.e. 10-2 and the lower limit i.e. 1-3 (10-2 ≧E≧10-3) or not. If so, the operation of sampling rate changing part 22 returns to step S2 for receipt of a next bit error ratio and the present sampling rate SR is held at 8f. Otherwise, the operation proceeds to step S4.
In step S4, sampling rate changing part 22 checks whether bit error ratio E is greater than 10-2 (E>10-2) or the ratio E is smaller than 10-3 (E<10-3). If the ratio E is greater than 10-2 the operation proceeds to step S4. If the ratio E is smaller than 1031 3, the operation proceeds to step S7.
If the sampling rate SR is set to any of sampling clocks 32f, 16f and 4f by sampling rate changing part 22, the steps of the operation of part 22 from step S2 to step S8 are respectively repeated to employ a preferable sampling rate. According to a digital radio communication system of the invention, since the error ratio is kept between the predetermined upper limit and the predetermined lower limit, good voice quality is obtained. Also, since the sampling rate is not increased to unnecessarily high frequency, power saving are achieved.
1. A method for receiving digital radio signals at a predetermined transmission rate, comprising the steps of:
monitoring a bit error ratio for digital demodulation; and
changing a sampling rate for digital demodulation of said digital radio signals at said predetermined transmission rate to a higher level when the bit error ratio exceeds a specified upper limit and to a lower level when the bit error ratio falls below a specified lower limit.
2. The method according to claim 1, wherein a digital modulation system of the digital demodulation is selected from π/4-shift differential quadrilateral phase shift keying, quadrilateral phase shift, and phase shift keying.
3. A digital radio signal receiver for receiving digital radio signals at a predetermined transmission rate, comprising:
a digital demodulation means for demodulating said digital radio signals;
a bit error ratio monitoring means for monitoring a bit error ratio in the digital demodulation means; and
a sampling rate changing means for changing a sampling rate at which said digital radio signals at said predetermined transmission rate are sampled for digital demodulation to a higher level when the bit error ratio exceeds a specified upper limit and to a lower level when the bit error ratio falls below a specified lower limit based on a signal from the bit error ratio monitoring means.
4. A digital radio signal receiver, comprising:
a digital demodulation means for demodulating a digital radio signal;
a bit error ratio monitoring means for monitoring a bit error ratio in the digital demodulation means;
a sampling rate changing means for changing a sampling rate of the digital demodulation means to a higher level when the bit error ratio exceeds a specified upper limit and to a lower level when the bit error ratio falls below a specified lower limit based on a signal from the bit error ratio monitoring means; and
a digital modulation system of the digital demodulation means being one of π/4-shift differential quadrilateral phase shift keying and differential quadrilateral phase shift keying, the digital demodulation means being a differential detector having shift registers, and the sampling rate changing means changing a frequency of a sampling clock and changing a number of bits of each of said shift registers in the differential detector to adapt to the frequency of the sampling clock.
5. A digital radio signal receiver for receiving digital radio signals at a predetermined transmission rate, comprising:
a differential detector for demodulating said digital radio signals in said digital radio signal receiver;
a bit error ratio monitor for detecting an error information of digital demodulation and calculating a bit error ratio on the basis of said error information;
a sampling rate changing module for changing a sampling rate at which said digital radio signals at said predetermined transmission rate are sampled in said differential detector for digital demodulation based on a signal from said bit error ratio monitor, said sampling rate being shifted to a higher frequency than a present frequency when said bit error ratio goes beyond a specified upper limit and to lower frequency when the bit error ratio falls below a specified lower limit; and
a sampling clock selector for supplying sampling clock signals determined by said sampling rate changing module to said differential detector.
6. A digital radio signal receiver according to claim 5, wherein said sampling clock signals are any frequency of N times higher than a symbol rate frequency where N is an integer.
7. A digital radio signal receiver according to claim 5, wherein said sampling clock signals are any of 32 times said symbol rate frequency, 16 times said symbol rate frequency, 8 times said symbol rate frequency and 4 times said symbol rate frequency.
8. A digital radio signal receiver for receiving digital radio signals at a predetermined transmission rate, comprising:
a differential detector for demodulating said digital radio signals in said digital radio signal receiver to produce a demodulated digital signal;
a bit error ratio monitor for detecting errors in the demodulated digital signal and calculating a bit error ratio;
a sampling rate changing module for changing a sampling rate at which said digital radio signals at said predetermined transmission rate are sampled in said differential detector for digital demodulation based on a signal from said bit error ratio monitor, said sampling rate being shifted to a higher frequency than a present frequency when said bit error ratio goes beyond a specified upper limit and to a lower frequency when the bit error ratio falls below a specified lower limit;
a sampling clock selector for supplying sampling clock signals determined by said sampling rate changing module to said differential detector; and
said upper limit of said bit error ratio being 10-2 and said lower limit of said bit error ratio being 10-3.
9. A digital radio signal receiver comprising:
a differential detector for demodulating a digital signal in said digital radio signal receiver;
a bit error ratio monitor for monitoring an error information signal, detecting errors in the demodulated digital signal, and calculating a bit error ratio;
a sampling rate changing module for changing a sampling rate for digital demodulation of said digital signal at a given transmission rate based on a signal from said bit error ratio monitor, said sampling rate for digital demodulation being shifted to a higher frequency than a present frequency when said bit error ratio goes beyond a specified upper limit and to a lower frequency when the bit error ratio falls below a specified lower limit;
a sampling clock selector for supplying sampling clock signals determined by said sampling rate for digital demodulation changing module to said differential detector; and
a framing portion and voice detector for generating said error information for digital demodulation.
10. A digital radio signal receiver comprising:
a sampling clock selector for supplying sampling clock signals determined by said sampling rate for digital demodulation changing module to said differential detector;
a framing portion and voice detector for generating said error information for digital demodulation; and
said error ratio monitor receiving and detecting said error information from said framing portion and voice detector.
11. A method for receiving digital radio signals comprising the steps of:
detecting an error information for digital demodulation;
calculating a bit error ratio from said error information;
producing a sampling rate for digital demodulation of said digital radio signal at a given transmission rate based on said bit error ratio;
changing said sampling rate for digital demodulation into a higher frequency when said bit error ratio goes beyond a specified upper limit and to a lower frequency when the bit error ratio falls below a specified lower limit; and
supplying a sampling clock signal determined by said sampling rate for digital demodulation.
12. A method for receiving digital radio signals according to claim 11, wherein the steps of supplying a sampling clock signal includes supplying any frequency of N times higher than a symbol rate frequency where N is an integer.
13. A method for receiving digital radio signals according to claim 11, wherein the step of supplying said sampling clock signal includes supplying said sampling clock signal at any of 32 times said symbol rate frequency, 16 times said symbol rate frequency, 8 times said symbol rate frequency and 4 times a symbol rate frequency.
US08345665 1993-11-29 1994-11-28 Method for receiving digital radio signals and a digital radio signals receiver Expired - Lifetime US5963590A (en)
JP29845093A JP3106818B2 (en) 1993-11-29 1993-11-29 Digital radio receiving method and apparatus
JP5-298450 1993-11-29
US08775116 US5956376A (en) 1993-11-29 1996-12-30 Apparatus for varying a sampling rate in a digital demodulator
US08775116 Division US5956376A (en) 1993-11-29 1996-12-30 Apparatus for varying a sampling rate in a digital demodulator
US5963590A true US5963590A (en) 1999-10-05
ID=17859870
US08345665 Expired - Lifetime US5963590A (en) 1993-11-29 1994-11-28 Method for receiving digital radio signals and a digital radio signals receiver
US08775116 Expired - Lifetime US5956376A (en) 1993-11-29 1996-12-30 Apparatus for varying a sampling rate in a digital demodulator
US (2) US5963590A (en)
JP (1) JP3106818B2 (en)
CA (1) CA2136896C (en)
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Electronics Information and Communication Assoication, Fall 1990 National Conference, "Structure and Performance of the B/300 p/4-Shift QPSK Baseband Differential Detector", by Denno, Sawahashi and Saito, of NTT Radio Communications Systems Laboratories.
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CA2136896C (en) 2000-06-20 grant
JPH07154441A (en) 1995-06-16 application
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