This paper proposes a narrowband fully-analog $N$-antenna transmitter that emulates the functionality of a narrowband fully-digital $N$-antenna transmitter. Specifically, in symbol interval $m$, the proposed fully-analog transmitter synthesizes an arbitrary complex excitation vector $\bm x[m]\in\mathbb{C}^N$ with prescribed total power $\|\bm x[m]\|_2^2=P$ from a single coherent RF tone, using only tunable phase-control elements embedded in a passive interferometric programmable network. The programmable network is excited through one input port while the remaining $N - 1$ input ports are impedance matched. In the ideal lossless case, the network transfer is unitary and therefore redistributes RF power among antenna ports without dissipative amplitude control. The synthesis task is posed as a unitary state-preparation problem: program a unitary family so that $\bm V(\bm\varphi)\bm e_1=\bm c$, where $\bm c=\bm x/\sqrt{P}$ and $\|\bm c\|_2=1$. We provide a constructive realization and a closed-form programming rule: a binary magnitude-splitting tree allocates the desired per-antenna magnitudes $|c_n|$ using $N -1$ tunable split ratios, and a per-antenna output phase bank assigns the target phases using $N$ tunable phase shifts. The resulting architecture uses $2N-1$ real tunable degrees of freedom and admits a deterministic $O(N)$ programming procedure with no iterative optimization, enabling symbol-by-symbol updates when the chosen phase-control technology supports the required tuning speed. Using representative COTS components, we model the RF-front-end DC power of the proposed fully-analog transmitter and compare it against an equivalent COTS fully-digital array. For $N\le 16$, the comparison indicates significant RF-front-end power savings for the fully-analog architecture. The results in this paper are intended as a proof-of-concept for a narrowband fully-analog transmitter.

翻译：本文提出一种窄带全模拟$N$天线发射机，其功能等效于窄带全数字$N$天线发射机。具体而言，在符号间隔$m$内，所提出的全模拟发射机仅通过嵌入无源干涉可编程网络的可调相位控制元件，从单一相干射频载波合成具有预设总功率$\|\bm x[m]\|_2^2=P$的任意复激励向量$\bm x[m]\in\mathbb{C}^N$。可编程网络通过一个输入端口激励，其余$N-1$个输入端口则进行阻抗匹配。在理想无损情况下，网络传递函数为酉矩阵，因此可在天线端口间重新分配射频功率而无需耗散性幅度控制。该合成任务可表述为酉态制备问题：编程酉矩阵族使得$\bm V(\bm\varphi)\bm e_1=\bm c$，其中$\bm c=\bm x/\sqrt{P}$且$\|\bm c\|_2=1$。我们提出了一种构造性实现方案及闭式编程规则：二进制幅度分配树通过$N-1$个可调分配比实现各天线目标幅度$|c_n|$的分配，而各天线输出相位组则通过$N$个可调移相器赋予目标相位。最终架构使用$2N-1$个实数可调自由度，并支持无需迭代优化的确定性$O(N)$编程流程，当所选相位控制技术满足调谐速度要求时，可实现逐符号更新。采用典型商用现货元件，我们对所提全模拟发射机的射频前端直流功耗进行建模，并与等效商用全数字阵列进行对比。当$N\le 16$时，对比结果表明全模拟架构可显著节省射频前端功耗。本文成果旨在为窄带全模拟发射机提供概念验证。