Radio
A received signal vector (X(t)) from an array antenna (# 1 to # 4 ) is subjected to frequency offset correction by a frequency offset correction part ( 6 ) and thereafter subjected to adaptive array processing. An error signal (e(t)) is referred to on the basis of an output signal (y(t)) from the adaptive array and a reference signal (d(t)) held in a memory ( 30 ) in a reference signal section or a replica signal (d′(t)) output from a forced phase-locking processing part ( 20 ) in a section having no reference signal, so that a frequency offset quantity (Δθ) is extracted therefrom by an offset extraction part ( 100 ).
1. A radio unit comprising:
an array antenna including a plurality of antennas; and
adaptive array processing means for receiving signals from said plurality of antennas and extracting a signal from a prescribed terminal, wherein
said adaptive array processing means includes frequency offset compensation means for compensating for a frequency offset of a received signal in response to a supplied offset compensation quantity,
said radio unit further comprising:
offset quantity detection means for receiving an output of said adaptive array processing means and extracting the frequency offset at prescribed timing; and
offset compensation quantity operation means for sequentially updating said offset compensation quantity for each symbol in a time slot on the basis of the result of detection by said offset quantity detection means.
2. The radio unit according to claim 1 , wherein
said received signal is divided into a plurality of slots to be transmitted,
each said slot includes:
a first partial signal including a predetermined reference signal, and
a second partial signal including transmitted data, and
said offset quantity detection means includes:
first storage means for holding said reference signal,
forced phase-locking means forcibly synchronizing the phase of an output from said adaptive array processing means with a prescribed phase,
error signal generation means outputting the difference between the reference signal stored in said first storage means and said output from said adaptive array processing means in a period when said adaptive array processing means outputs said first partial signal while outputting the difference between an output from said forced phase-locking means and said output from said adaptive array processing means in a period when said adaptive array processing means outputs said second partial signal, and
offset extraction means for extracting said frequency offset on the basis of the output from said error signal generation means.
3. The radio unit according to claim 2 , wherein
said offset compensation quantity operation means includes:
second storage means for storing said offset compensation quantity at any time, and
calculation means calculating an update value θ′ for said offset compensation quantity as:
θ′=θ+μ×Δθ
on the basis of the offset compensation quantity θ stored in said second storage means and the output Δθ from said offset extraction means assuming that μ represents a prescribed coefficient.
4. The radio unit according to claim 2 , wherein
said offset compensation quantity operation means includes:
second storage means for storing said offset compensation quantity at any time, and
calculation means calculating an update value θ′ for said offset compensation quantity on the basis of the offset compensation quantity θ stored in said second storage means and the output Δθ from said offset extraction means while reducing the quantity changed in updating as the updating progresses.
5. The radio unit according to claim 4 , wherein
said offset compensation quantity operation means further includes:
error detection means for detecting a receiving error, and
said calculation means calculates the update value θ′ for said offset compensation quantity as:
θ′=θ+(μ 0 ×λ T )×Δθ
on the basis of the offset compensation quantity θ stored in said storage means and the output Δθ of said offset extraction means assuming that λ represents a prescribed positive coefficient less than 1 and μ0 represents an initial value of the coefficient μ while assuming that T represents a value corresponding to the number of updating opportunities allowing no detection of receiving errors.
6. The radio unit according to claim 4 , wherein
said calculation means updates said offset compensation quantity every plurality of frames.
7. The radio unit according to claim 2 , wherein
said offset compensation quantity operation means includes:
second storage means for storing said offset compensation quantity at any time, and
calculation means calculating an update value θ′ for said offset compensation quantity on the basis of the offset compensation quantity θ stored in said second storage means and the output Δθ from said offset extraction means while increasing the quantity changed in updating in response to the magnitude of the absolute value of the output from said error signal generation means.
8. The radio unit according to claim 2 , wherein
said offset compensation quantity operation means includes:
second storage means for storing said offset compensation quantity at any time, and
calculation means calculating an update value θ′ for said offset compensation quantity,
i) on the basis of the offset compensation quantity θ stored in said second storage means and the output Δθ from said offset extraction means while increasing the quantity changed in updating in response to the magnitude of the absolute value of the output from said error signal generation means in a period when said adaptive array processing means outputs said first partial signal, or
ii) as:
θ′=θ+μ×Δθ
in a period when said adaptive array processing means outputs said second partial signal, assuming that μ represents a prescribed coefficient.
9. The radio unit according to claim 1 , wherein
said received signal is divided into a plurality of slots to be transmitted,
each said slot includes:
a first partial signal including a predetermined reference signal, and
a second partial signal including transmitted data, and
said offset quantity detection means includes:
forced phase-locking means forcibly synchronizing the phase of the output from said adaptive array processing means with a prescribed phase,
error signal generation means outputting the difference between an output from said forced phase-locking means and the output from said adaptive array processing means in a period when said adaptive array processing means outputs said second partial signal, and
offset extraction means for extracting said frequency offset on the basis of the output from said error signal generation means.
10. The radio unit according to claim 9 , wherein
said offset compensation quantity operation means includes:
second storage means for storing said offset compensation quantity at any time, and
calculation means calculating an update value θ′ for said offset compensation quantity as:
θ′=+μ×Δθ
on the basis of the offset compensation quantity θ stored in said second storage means and an output Δθ from said offset extraction means assuming that μ represents a prescribed coefficient.