US 2017/0317697 A1Published application

Transmitter, signal synthesis circuit, and signal synthesis method

AssigneeNEC Corporation

InventorKeiichi MOTOI

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Abstract

A multi-bit digital signal that is generated by modulating a baseband signal by a modulation circuit and includes components in a radio frequency band is amplified by switch-mode amplifiers (100-1, 100-2) on a bit-by-bit basis, amplified signals are band-limited by frequency-variable variable band limiting units (201-1, 201-2) and thereafter subjected to voltage-to-current conversion by voltage/current source conversion units (202-1, 202-2) provided with variable capacitances, the signals converted to current are synthesized at a synthesis point X, and a resultant signal is impedance-corrected by an impedance correction unit (203) and output as a transmission signal to an antenna of a load (300). Consequently, the present invention provides a transmitter capable of synthesizing output signals from a plurality of switch-mode amplifiers and transmitting a resultant signal while maintaining an impedance characteristic with respect to a plurality of transmit frequencies without increasing a circuit size.

Claims10

Dependent claims

A transmitter comprising:

a modulation circuit configured to modulate a baseband signal into a multi-bit digital signal including a component in a radio frequency band;
a switch-mode amplifier disposed corresponding to each bit of the multi-bit digital signal output from the modulation circuit and configured to amplify the multi-bit digital signal on a bit-by-bit basis;
a signal-synthesizing circuit configured to signal-synthesize the multi-bit digital signal output from the respective switch-mode amplifiers as a transmission signal;
and
an antenna configured to transmit the transmission signal, wherein
the signal-synthesizing circuit includes:
a frequency-variable band-limiting unit that band-limits an output signal from each of the switch-mode amplifiers;
a voltage/current source conversion unit that converts an output signal from each of the band-limiting unit from voltage to current, the voltage/current source conversion unit including at least a variable capacitance;
and
a synthesizing point configured to connect output nodes of the respective voltage/current source conversion unit and synthesize output signals output from the respective voltage/current source conversion unit, and
the transmitter further comprises an impedance correction unit that corrects an impedance, the impedance correction unit being disposed on a signal path between the synthesizing point of the signal-synthesizing circuit and the antenna serving as a load.

8 more elements

Dependencies are inferred from the claim text.