Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Phase comparison
Reexamination Certificate
2003-03-05
2004-09-21
Le, N. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Phase comparison
C455S226100
Reexamination Certificate
active
06794858
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a receiving level measuring circuit for use in a receiver of a mobile communication system, and more particularly to a receiving level measuring circuit capable of improving measuring accuracy of a receiving level and of meeting the specifications for the use of a receiver having a plurality of branches.
2. Description of the Related Art
In a mobile communication system, various multiple access methods have been invented to utilize resources of limited frequencies or the like, and a CDMA (direct sequence-code division multiple access) method is receiving attention.
In the CDMA method, particularly in a DS-CDMA (direct sequence code division multiple access) method in which individual spread codes are allocated to channels to be used for communications so as to be multiplexed and a pilot symbol is inserted into a transmission symbol before transmission while an amplitude phase variation is extracted from a despread signal of the pilot symbol and used to correct the received symbol for demodulation at a receiving end, it is known that there is a need for measuring a level of a received wave in a receiver in order to perform a closed-loop control type transmission power control that is characteristic of the DS-CDMA method.
A conventional general receiving level measurement for a level measurement of a received wave comprises detecting an RSSI (a received signal strength indicator) of a received-signal in a radio frequency band that has already been input to a receiver and calculating a dB value of the RSSI.
First, a sample structure of a receiving level measuring circuit in the conventional CDMA receiver will be described with reference to FIG.
9
. Referring to
FIG. 9
, there is shown a block diagram illustrating a sample structure of the conventional receiving level measuring circuit.
As shown in
FIG. 9
, the conventional receiving level measuring circuit comprises an RSSI detection unit
1
, an analog-to-digital conversion unit (shown as an A-D unit)
2
, an RSSI averaging unit
3
, and a voltage/dB conversion unit
4
.
The following describes components of the conventional receiving level measuring circuit.
The RSSI detection unit
1
is used to detect a received signal strength indicator (RSSI) of a received signal in a radio frequency band and to output the voltage. Note that this unit is implemented in a commercially available RSSI detection IC.
The analog-to-digital conversion unit
2
is used to convert an RSSI analog value whose voltage has been output to a digital value.
The RSSI averaging unit
3
is used to average the detected RSSI.
The voltage/dB conversion unit
4
is used to convert the averaged RSSI voltage to a dB vale. Note that the function of this unit is implemented by previously generating a conversion table of the RSSI voltage versus the RSSI dB value and referencing it.
The following describes an operation of the conventional level measuring circuit with reference to FIG.
9
.
In the conventional level measuring circuit, a received signal in a radio frequency band input to a receiver is input to the RSSI detection unit
1
, an RSSI of the received signal is detected and output as an analog voltage value, the analog value is converted to a digital value in the analog-to-digital conversion unit
2
, the value is submitted to a given averaging process in the RSSI averaging unit
3
and then converted to a dB value in the voltage/dB conversion unit
4
, and a result of measuring the receiving level of the signal input to the receiver is output as an RSSI dB value.
This enables a measurement of a quality of receiving the signal input to the receiver.
The above conventional receiving level measuring circuit, however, has a problem that the signals input to the receiver are not always at desirable wave levels since a plurality of transmitters and receivers use an identical radio frequency band for communications in the DS-CDMA method, by which they are measured simply as receiving levels despite the fact that interference wave levels are included.
In addition, the RSSI measurement in the radio frequency band has a problem that it is impossible to measure levels lower than or equal to an in-band noise of a radio unit of the receiver in a theoretical sense, thereby disabling accurate measurement of receiving levels at all levels.
To solve these problems, there has been offered a technology titled “Receiving level measuring method and receiving level measuring circuit” (Applicant: Hitachi Kokusai Electric Inc., Inventor: Takahito Ishii) in Japanese Unexamined Patent Publication (Kokai) No. 285209 of 2001 laid open to public inspection on Oct. 12, 2001.
This conventional technology is a receiving level measuring method and a receiving level measuring circuit for detecting a field strength of a received signal, detecting a desirable wave and an interference wave for each spread code from a baseband signal through a quadrature detection, synthesizing a plurality of desirable wave components with each other to convert them into electricity, correcting the synthesized desirable wave level by adding a reception field strength detected in the radio unit if the reception field strength is more than the in-band noise while using the desirable wave level directly if the reception field strength is lower than or equal to the in-band noise, and considering it to be a result of the receiving level measurement.
The conventional technology in the above, the receiving level measuring-circuit in Japanese Unexamined Patent Publication No. 285209 of 2001 has a basic configuration enabling a measurement of a desirable wave receiving level up to a level lower than or equal to the in-band noise of the receiver radio unit since the measuring circuit separates and measures the desirable level and interference wave level and uses the desirable wave power level as a desirable wave receiving level if the reception field strength is a specific value or below (in-band noise or below) or corrects the desirable wave power level by adding the field strength level to the desirable wave power level and considers the corrected value to be a desirable wave receiving level if the reception field strength is more than the specific value (more than the in-band noise).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a receiving level measuring circuit capable of improving measuring accuracy of a receiving level by correcting phase rotation caused by a frequency error between oscillators included in a transmitter and a receiver and by inhibiting an inappropriate correction in situations that no desirable wave exists.
It is another object of the present invention to provide a receiving level measuring circuit adapting to a receiver configuration having a plurality of antennas (branches).
In accordance with one aspect of the present invention, there is provided a receiving level measuring circuit, comprising: received signal strength indicator (RSSI) detection means for detecting a field strength of a received signal, quadrature detection means for performing a quadrature detection of the received signal, desirable/interference wave detection means for detecting a plurality of desirable wave components, a plurality of interference wave components, and a plurality of frequency error vectors from the received signal submitted to the quadrature detection, frequency error correction-value acquisition means for previously storing a correction value corresponding to the frequency error and then adding and averaging the plurality of frequency error vectors detected by the desirable/interference wave detection means so as to get the correction value corresponding to the frequency error submitted to a unit conversion, frequency error correction means for adding the plurality of desirable wave components detected by the desirable/interference wave detection means and for correcting the desirable wave components using the correction value, desirable wave. component electricity conversion means for co
He Amy
Hitachi Kokusai Electric Inc.
LandOfFree
Receiving level measuring circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Receiving level measuring circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Receiving level measuring circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3265481