Abstract: Part of compensation of the transmission characteristics of the optical transmitter is performed by transmitter compensation circuitry disposed at a stage prior to the optical transmitter. Remaining part of compensation of the transmission characteristics of the optical transmitter and compensation of the transmission characteristics of the optical receiver is performed by a receiver compensation circuitry disposed at a stage subsequent to the optical receiver. Transmitter compensation characteristics of the transmitter compensation circuitry is set so that a peak-to-average-power ratio of an output signal from the transmitter compensation circuitry becomes equal to or smaller than a predetermined value.

Abstract: Part of compensation of the transmission characteristics of the optical transmitter is performed by transmitter compensation circuitry disposed at a stage prior to the optical transmitter. Remaining part of compensation of the transmission characteristics of the optical transmitter and compensation of the transmission characteristics of the optical receiver is performed by a receiver compensation circuitry disposed at a stage subsequent to the optical receiver. Transmitter compensation characteristics of the transmitter compensation circuitry is set so that a peak-to-average-power ratio of an output signal from the transmitter compensation circuitry becomes equal to or smaller than a predetermined value.

Abstract: A process of estimating a transfer function or an inverse transfer function of the optical transmitter from first data obtained by the optical receiver when a first known signal is transmitted from the transmitter to the receiver, and a temporary transfer function or a temporary inverse transfer function of the optical receiver, is performed for multiple frequency offsets between the optical transmitter and the optical receiver. At this time, the transfer function or the inverse transfer function of the optical transmitter is estimated by comparing the first data obtained by compensating at least one or none of a temporary transfer function of the optical receiver and transmission path characteristics detected in the receiver, with a first known signal before transmission to which what is not compensated for the first data between the temporary transfer function of the optical receiver and the transmission path characteristic is added.

Abstract: A process of estimating a transfer function or an inverse transfer function of the optical transmitter from first data obtained by the optical receiver when a first known signal is transmitted from the transmitter to the receiver, and a temporary transfer function or a temporary inverse transfer function of the optical receiver, is performed for multiple frequency offsets between the optical transmitter and the optical receiver. At this time, the transfer function or the inverse transfer function of the optical transmitter is estimated by comparing the first data obtained by compensating at least one or none of a temporary transfer function of the optical receiver and transmission path characteristics detected in the receiver, with a first known signal before transmission to which what is not compensated for the first data between the temporary transfer function of the optical receiver and the transmission path characteristic is added.

Abstract: A method estimating transmission characteristics of an optical transmitter of a transmission unit and an optical receiver of a reception unit, including: estimating a temporary transfer or inverse transfer function of the optical receiver; estimating a transfer or inverse transfer function of the optical transmitter from first data acquired by the reception unit when a first known signal is transmitted from the transmission unit, and the estimated temporary transfer or inverse transfer function of the optical receiver, a difference between the first known signal and an original first known signal is minimized; and estimating a transfer or inverse transfer function of the optical receiver from second data acquired by the reception unit when a second known signal is transmitted from the transmission unit, and the estimated transfer or inverse transfer function of the optical transmitter, a difference between the second known signal and an original second known signal is minimized.

Abstract: A method estimating transmission characteristics of an optical transmitter of a transmission unit and an optical receiver of a reception unit, including: estimating a temporary transfer or inverse transfer function of the optical receiver; estimating a transfer or inverse transfer function of the optical transmitter from first data acquired by the reception unit when a first known signal is transmitted from the transmission unit, and the estimated temporary transfer or inverse transfer function of the optical receiver, a difference between the first known signal and an original first known signal is minimized; and estimating a transfer or inverse transfer function of the optical receiver from second data acquired by the reception unit when a second known signal is transmitted from the transmission unit, and the estimated transfer or inverse transfer function of the optical transmitter, a difference between the second known signal and an original second known signal is minimized.

Abstract: In a method in which a compensation coefficient calculating portion (6) calculates a compensation coefficient of a compensation portion (5) which compensates transmission characteristics of a signal, a known signal is extracted from the signal. Next, a pseudo-random number is added to the extracted known signal. Next, the compensation coefficient is calculated by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.

Abstract: In a method in which a compensation coefficient calculating portion (6) calculates a compensation coefficient of a compensation portion (5) which compensates transmission characteristics of a signal, a known signal is extracted from the signal. Next, a pseudo-random number is added to the extracted known signal. Next, the compensation coefficient is calculated by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.

Abstract: A feedback path (307) is formed between an output (310c) of a fixed divider (305) and a control terminal (310b) of an inverting/noninverting unit (304). A connection device (306) is arranged on the feedback path (307). The feedback path (307) is connected/disconnected according to the level of the control signal M from outside, thereby switching the number of divisions. The delay time of the signal given to the input terminal (310a) of the inverting/noninverting unit (304) to pass through the feedback path (307) and return to the control terminal (310b) is set greater than the pulse width of the input clock signal. A small pulse input invalidating function is provided in the fixed divider (305). Alternatively, a small pulse output prohibiting function is provided in the inverting/noninverting unit (304).

Abstract: A feedback path (307) is formed between an output (310c) of a fixed divider (305) and a control terminal (310b) of an inverting/noninverting unit (304). A connection device (306) is arranged on the feedback path (307). The feedback path (307) is connected/disconnected according to the level of the control signal M from outside, thereby switching the number of divisions. The delay time of the signal given to the input terminal (310a) of the inverting/noninverting unit (304) to pass through the feedback path (307) and return to the control terminal (310b) is set greater than the pulse width of the input clock signal. A small pulse input invalidating function is provided in the fixed divider (305). Alternatively, a small pulse output prohibiting function is provided in the inverting/noninverting unit (304).

Abstract: In the dual modulus prescaler circuit, an output terminal of the first multi-input logic gate circuit is connected to a data input terminal of a first D flip-flop circuit; output terminals of the first to (n-2)th D flip-flop circuits are, respectively, connected to data input terminals of the second to (n-1)th D flip-flop circuits; output terminals of the (n-1)th and nth D flip-flop circuits are connected to input terminals of the first multi-input logic gate circuit; the second multi-input logic gate circuit is connected to the output terminal of the (n-1)th D flip-flop circuit and receives a switching signal; and an output terminal of the second multi-input logic gate circuit is connected to a data input terminal of the nth D flip-flop circuit. Moreover, all the aforementioned connections are connections using differential signals.

Abstract: A phase-locked loop comprises a phase detector receiving an externally supplied reference signal and a feedback signal, a charge pump connected to an output of the phase detector, a loop filter configured to extract a low-frequency component from an output of the charge pump, and a voltage controlled oscillator having an input connected to the output of the loop filter and an output connected to the feedback signal supplied to the phase detector. The charge pump comprises a first switch that controls outputting a positive current based on the output of the phase detector, a second switch that controls outputting a negative current based on the output of the phase detector, a third switch connected between the first switch and the second switch to control an output to the loop filter, and a switching control signal input terminal that receives a switching control signal for controlling a switching operation of the third switch.

Abstract: A phase-locked loop comprises a phase detector receiving an externally supplied reference signal and a feedback signal, a charge pump connected to an output of the phase detector, a loop filter configured to extract a low-frequency component from an output of the charge pump, and a voltage controlled oscillator having an input connected to the output of the loop filter and an output connected to the feedback signal supplied to the phase detector. The charge pump comprises a first switch that controls outputting a positive current based on the output of the phase detector, a second switch that controls outputting a negative current based on the output of the phase detector, a third switch connected between the first switch and the second switch to control an output to the loop filter, and a switching control signal input terminal that receives a switching control signal for controlling a switching operation of the third switch.

Abstract: In an image-rejection receiver having a first frequency conversion stage (1, 2, 9) having a pair of frequency mixers (1,2) each supplied external radio frequency signal (RF) and first local frequency signal (LOCAL1) with quadrature phase relations (9), a second frequency conversion stage (3-6, 10) having two pairs of frequency mixers (3-4, 5-6) at each output of each first stage mixer and second local frequency signal (LOCAL2) with quadrature phase relations (10), and an adder (7) and a subtractor (8) for providing sum and difference of amplitude of outputs of said second frequency conversion stage to provide inphase component (BBI) and quadrature-phase component (BBQ), no filter is used for removing an undesirable image signal which is generated in frequency conversion. A control circuit (11) is provided to keep accurate quadrature phase relations for said first local frequency signal, and said second local frequency signal, by measuring D.C. component of a product of outputs of two of mixers.

Abstract: A programmable delay generator comprises a first ramp wave generator and a second ramp wave generator, each having the same structure as each other, each of them operating with external common clock pulses, and each of them providing potential gradient and final potential incorporated with an external set data; a comparator for comparing an output (Vs) of the first ramp wave generator and an output (Vk) of the second ramp wave generator so that an output pulse is provided when the outputs of two ramp wave generators coincide with each other; said first ramp wave generator providing a first ramp voltage (Vs) upon receipt of a first set data (S) at a predetermined time (t0); said second ramp wave generator providing a threshold voltage (Vk) upon receipt of a second set data (K) at a time which preceds at least one clock time (T) than said predetermined time (t0); said comparator providing an output pulse delayed by delay time (td) which is proportional to ratio (K/S) of said second set data (K) and said first s